An��lisis de la influencia de imperfecciones en el borde de ataque en perfiles aerodin��micos a bajos n��meros de Reynolds

En esta tesis se ha analizado la influencia que tienen ciertas imperfecciones en el borde de ataque de un perfil aerodin��mico sobre el comportamiento aerodin��mico general del mismo, centr��ndose fundamentalmente en la influencia sobre el coeficiente de sustentaci��n m��xima, coeficiente de resistencia y sobre la eficiencia aerodin��mica del perfil, es decir sobre la relaci��n entre la sustentaci��n y la resistencia aerodin��micas. Tambi��n se ha analizado su influencia en otros aspectos, como la entrada en p��rdida, ��ngulo de ataque de sustentaci��n m��xima, ��ngulo de ataque de eficiencia m��xima, coeficiente de momento aerodin��mico y posici��n del centro aerodin��mico. Estos defectos de forma en el borde de ataque pueden aparecer en algunos procesos de fabricaci��n de determinados elementos aerodin��micos, como pueden ser las alas de peque��os aviones no tripulados o las palas de aeroturbina. Los perfiles se ha estudiado a bajos n��meros de Reynolds debido a su uso reciente en una amplia gama de aplicaciones, desde veh��culos a��reos no tripulados (UAV) hasta palas de aeroturbina de baja potencia, e incluso debido a su potencial utilizaci��n en aeronaves dise��adas para volar en atm��sferas de baja densidad. El objeto de estudio de esta tesis no ha sido analizado en profundidad en la literatura cient��fica, aunque s�� que se ha estudiado por varios autores el comportamiento de perfiles a bajos n��meros de Reynolds, con ciertas protuberancias sobre su superficie o tambi��n con formaci��n de hielo en el borde de ataque. Para la realizaci��n de este estudio se han analizado perfiles de distinto tipo, perfiles sim��tricos y con curvatura, perfiles laminares, y todos ellos con igual o distinto espesor, con el objeto de obtener y comparar la influencia del fen��meno estudiado sobre cada tipo de perfil y as�� analizar su grado de sensibilidad a estas imperfecciones en la geometr��a del borde de ataque. Este trabajo ha sido realizado experimentalmente utilizando una t��nel aerodin��mico dise��ado espec��ficamente a tal efecto, as�� como una balanza electr��nica para medir las fuerzas y los momentos sobre el perfil, y un esc��ner de presiones para medir la distribuci��n de presiones sobre la superficie de los perfiles en determinados casos de inter��s. La finalidad de este estudio est�� orientada al establecimiento de criterios para cuantificar la influencia en la aerodin��mica del perfil que tiene el hecho de que el borde de ataque presente una discontinuidad geom��trica, con el objeto de poder establecer los l��mites de aceptaci��n o rechazo de estas piezas en el momento de ser fabricadas. Del an��lisis de los casos estudiados se puede concluir que seg��n aumenta el tama��o de la imperfecci��n del borde de ataque, la sustentaci��n aerodin��mica m��xima en general disminuye, al igual que la eficiencia aerodin��mica m��xima, pues la resistencia aerodin��mica aumenta. Sin embargo, en algunos casos, para peque��os defectos se produce un efecto contrario. La sustentaci��n m��xima aumenta apreciablemente sin apenas p��rdida de eficiencia aerodin��mica m��xima. ABSTRACT The aim of this thesis is to analyze the effects of leading edge imperfections on the aerodynamic characteristics of airfoils at low Reynolds numbers. The leading edge imperfection here considered being a slight displacement of half airfoil with respect to the other. This study has focus on its influence on the airfoil���s aerodynamic lift, drag and on the aerodynamic efficiency of the airfoil, that is, the relationship between the aerodynamic lift and drag. It has also been studied how this fact may alter some other aerodynamic aspects of airfoils, such as stall, angle of attack of maximum lift, angle of maximum efficiency, aerodynamic moment coefficient and aerodynamic center position. These imperfections in the leading edge may appear in some manufacturing processes of certain aerodynamic elements, such as unmanned aircraft wings or wind turbine blades. The study has focused on the analysis of the behavior at low Reynolds numbers due to recent use of low Reynolds numbers airfoils in a wide range of applications, from unmanned aerial vehicles (UAV) to low power wind turbine blades, or even due to their potential use in aircraft designed to fly in low density atmospheres as the one existing in Mars. This phenomenon has not been deeply analyzed in the literature, although several authors have discussed on airfoils at low Reynolds number, with leading edge protuberances or airfoils with ice accretions. Various types of airfoils have been analyzed, laminar and non-laminar, symmetric and curved airfoils, and airfoils with different thickness, in order to compare the degree of influence of the phenomenon studied on each airfoil type and thus, to estimate the degree of sensitivity to the anomaly geometry. The study was carried out experimentally using a test chamber designed specifically for this purpose, as well as an electronic balance to measure the forces and moments on the airfoil, and a pressure scanner to measure distribution of pressures in certain cases. The main purpose of this research is to establish a criteria for quantifying the influence that a slight displacement of half aerofoil with respect to the other has in the degradation of aerodynamics characteristics, aiming at establishing the acceptance limits for these pieces when they are manufactured, according to the type of airfoil used. Based on the results obtained from the analysis of the cases under study it can be concluded that displacements, within the range of study, decreases maximum aerodynamic lift, but the aerodynamic drag increases, and consequently there is a reduction of aerodynamic efficiency. However, in some cases, for small defects opposite effect occurs. The maximum lift increases significantly with little loss of maximum aerodynamic efficiency.

Probabilistic approach for longitudinal ventilation system design in fire situations

The main objective of ventilation systems in tunnels is to reach the highest possible safety level both in service and fire situation; being the fire one, the most relevant when designing the system. When designing a longitudinal ventilation system, the methodology to evaluate the capacity of the system is similar both in service and fire situation, with the exception of the chimney effect and the phenomena of thermal transfer which is responsible or the changes in the density of the air. When facing the dimensioning task for longitudinal ventilated tunnels, although similar methodologies are used in different countries, specific hypothesis (aerodynamic, thermal properties, traffic) even if discussed in the literature or current practice, are not usually detailed in the regulations or recommendations. The aim of this paper is to propose a probabilistic approach to the problem which would allow the designer, and the tunnel owner, to understand the uncertainty and sensibility adopted in the results and, eventually, identify possible ways of optimizing the ventilation solution to be adopted.

Ventilation and FFFS fire tests for ���Calle 30��� road tunnels

Between 2003 and 2007 an urban network or road tunnels with a total constructed tubes length of 45 km was built in the city of Madrid. This amazing engineering work, known as "Calle 30 Project" counted with different kinds of tunnel typologies and ventilation systems. Due to the length of the tunnels and the impact of the work itself, the tunnels were endowed with a great variety of installations to provide the maximum levels of safety both for users and the infrastructure includieng, in some parts of the tunnel, fixed fire fighting system based on water mist. Whithin this framework a large-scale programme of fire tests was planned to study different aspects related to fire safety in the tunnels including the phenomena of the interaction between ventilation and extinguishing system. In addition, these large scale fire tests allowed fire brigades of the city of Madrid an opportunity to define operational procedures for specific fire fighting in tunnels and evaluate the possibilities of fixed fire fighting systems. The tests were carried out in the Center of Experimentation "San pedro of Anes" which includes a 600 m tunnel with a removable false ceiling for reproducing different ceiling heights and ventilation conditions (transverse and longitudinal ones). Interesting conclusions on the interaction of ventilation and water mist systems were obtained but also on other aspects including performance of water mist system in terms of reduction of gas temperatures or visibility conditions. This paper presents a description of the test's programme carried out and some previous results obtained.

The Cup Anemometer, a Fundamental Meteorological Instrument for the Wind Energy Industry. Research at the IDR/UPM Institute

The results of several research campaigns investigating cup anemometer performance carried out since 2008 at the IDR/UPM Institute are included in the present paper. Several analysis of large series of calibrations were done by studying the effect of the rotor���s geometry, climatic conditions during calibration, and anemometers��� ageing. More specific testing campaigns were done regarding the cup anemometer rotor aerodynamics, and the anemometer signals. The effect of the rotor���s geometry on the cup anemometer transfer function has been investigated experimentally and analytically. The analysis of the anemometer���s output signal as a way of monitoring the anemometer status is revealed as a promising procedure for detecting anomalies.

Sistema de control de tracci��n y salida para un monoplaza de la F��rmula SAE

En este proyecto de final de carrera se detalla el proceso de dise��o, fabricaci��n, montaje y ajuste de un dispositivo electr��nico que sirva como sistema de control de tracci��n de un veh��culo y que acoplaremos sobre un monoplaza de carreras que participa en la competici��n Formula SAE. La Formula SAE (Society of Automotive Engineers - Sociedad de Ingenieros de Automoci��n), es una competici��n de coches de carreras monoplaza a nivel universitario que promueve el desarrollo de la ingeniera aplicada a la automoci��n. Se pretende que este libro sirva de gu��a para el correcto manejo y desempe��o del sistema fabricado. Adem��s se ha pretendido que su lectura resulte f��cil y comprensible para que la persona que lea este libro sea capaz de entender el sistema realizado para as�� poderlo mejorar. Gracias a la colaboraci��n entre la Escuela T��cnica Superior de Ingenier��a y Sistemas de Telecomunicaci��n (ETSIST) de la Universidad Polit��cnica de Madrid (UPM), la Escuela de Ingenieros Industriales de esta misma Universidad (ETSII) y el Instituto Universitario de Investigaci��n del Autom��vil (INSIA), se sientan las bases de una plataforma docente en la cual se posibilita la formaci��n y desarrollo de un veh��culo tipo formula que participa en la ya mencionada competici��n Formula SAE. Para ello, se formo en el 2003 el equipo UPMRacing, primer representante espa��ol en el evento. El equipo se compone de m��s de 50 alumnos de la UPM y del M��ster de Ingenier��a en Automoci��n del INSIA. Es por tanto, en el veh��culo fabricado por el equipo UPMRacing, en el que se pretende instalar este sistema de control de tracci��n. El control de tracci��n es un sistema de seguridad del autom��vil dise��ado para prevenir la perdida de adherencia cuando alguna rueda presenta deslizamiento, bien porque el conductor se excede en la aceleraci��n o bien porque el firme este resbaladizo. La unidad de procesamiento del sistema de control de tracci��n fabricado lee la velocidad de cada rueda del veh��culo mediante unos sensores y determina si existe deslizamiento, en tal caso, manda una se��al a la centralita para disminuir la potencia hasta que el deslizamiento disminuya a unos valores controlados. El sistema cuenta con un control remoto que sirve como interfaz para que el piloto pueda manejarlo. Por ultimo, el dispositivo es capaz de conectarse a un bus de comunicaciones CAN para configurar ciertos par��metros. El objetivo del sistema es, b��sicamente, hacer que el coche no derrape en aceleraciones fuertes; concretamente en las salidas desde parado y al tomar una curva, aumentando as�� la velocidad en circuito y la seguridad del piloto. ABSTRACT. The purpose of this project is to describe the design, manufacture, assembly and adjustment processes of an electronic device acting as the traction control system (TCS) of a vehicle, that we will attach to a single-seater competition formula SAE car. The Formula SAE (Society of Automotive Engineers) is a graduate-level singleseater racing car competition promoting the development of automotive applied engineering. We also intend this work to serve as a technical user guide of the manufactured system. It is drafted clearly and concisely so that it will be easy for all those to whom it is addressed to understand and subject to further improvements. The close partnership among the Escuela T��cnica Superior de Ingenier��a y Sistemas de Telecomunicaci��n (ETSIST), Escuela de Ingenieros Industriales (ETSII) of Universidad Polit��cnica de Madrid (UPM), and the Instituto Universitario de Investigaci��n del Autom��vil (INSIA), lays the foundation of a teaching platform enabling the training and development of a single-seater racing car taking part in the already mentioned Formula SAE competition. In this respect, UPMRacing team was created back in 2003, first spanish representative in this event. The team consists of more than 50 students of the UPM and of INSIA Master in Automotive Engineering. It is precisely the vehicle manufactured by UPMRacing team where we intend to install our TCS. TCS is an automotive safety system designed to prevent loss of traction when one wheel has slip, either because the driver exceeds the acceleration or because the firm is slippery. The device���s central processing unit is able to detect the speed of each wheel of the vehicle via special sensors and to determine wheel slip. If this is the case, the system sends a signal to the ECU of the vehicle to reduce the power until the slip is also diminished to controlled values. The device has a remote control that serves as an interface for the pilot to handle it. Lastly, the device is able to connect to a communication bus system CAN to set up certain parameters. The system objective is to prevent skidding under strong acceleration conditions: standing-start from the starting grid or driving into a curve, increasing the speed in circuit and pilot���s safety.

A study on the inclusion of forest canopy morphology data in numerical simulations for the purpose of wind resource assessment

A series of numerical simulations of the flow over a forest stand have been conducted using two different turbulence closure models along with various levels of canopy morphology data. Simulations have been validated against Stereoscopic Particle Image Velocimetry measurements from a wind tunnel study using one hundred architectural model trees, the porosities of which have been assessed using a photographic technique. It has been found that an accurate assessment of the porosity of the canopy, and specifically the variability with height, improves simulation quality regardless of the turbulence closure model used or the level of canopy geometry included. The observed flow field and recovery of the wake is in line with characteristic canopy flows published in the literature and it was found that the shear stress transport turbulence model was best able to capture this detail numerically.

Genetically aerodynamic optimization of the nose shape of a high-speed train entering a tunnel

The optimization of the nose shape of a high-speed train entering a tunnel has been performed using genetic algorithms(GA).This optimization method requires the parameterization of each optimal candidate as a design vector.The geometrical parameterization of the nose has been defined using three design variables that include the most characteristic geometrical factors affecting the compression wave generated at the entry of the train and the aerodynamic drag of the train.

Dise��o y construcci��n de una mini-turbina e��lica

Dado que es dif��cil imaginar en el futuro una sociedad moderna donde la energ��a no juegue un papel fundamental y puesto que numerosos estudios han demostrado que el ritmo actual de consumo de combustibles es insostenible y perjudicial para la vida del planeta, es fundamental concienciar a la humanidad de que un cambio de tendencia no solo es necesario sino que es imperativo. No se trata de erradicar por completo el uso de fuentes de car��cter f��sil, pues en muchos pa��ses es su principal o incluso su ��nica forma de obtener energ��a, sino de avanzar hacia un equilibrio en la generaci��n, para lo que ser�� vital permitir el desarrollo de energ��as limpias, aumentar la eficiencia de la tecnolog��a y reducir el consumo. En este contexto se ha decidido construir un rotor e��lico de peque��as dimensiones que servir�� como herramienta de estudio para alumnos de ingenier��a. Para dise��ar la turbina se ha desarrollado un modelo de programaci��n inform��tica que, basado en conceptos aerodin��micos, permite calcular la geometr��a de las palas en funci��n de unas condiciones iniciales, estimar la potencia del rotor y obtener sus curvas de funcionamiento. Uno de los principales problemas de la tecnolog��a e��lica es su alta variabilidad, por ello se ha implementado un sistema de regulaci��n de velocidad; se trata de un mecanismo que act��a sobre la orientaci��n de las palas y permite regular la potencia de un generador el��ctrico acoplado al rotor. Los aerogeneradores actuales recurren a este tipo de sistemas para tratar de suavizar los desequilibrios de potencia que puedan producir las r��fagas de viento. Se ha recurrido a un software de dise��o asistido por ordenador para dibujar tanto el rotor como el sistema de regulaci��n de velocidad. La mayor��a de las piezas del rotor se han fabricado con ayuda de una impresora 3D, otras, las met��licas, se han tallado en aluminio mediante un torno. Aunque el programa inform��tico que realiza los c��lculos aerodin��micos devuelve datos te��ricos a cerca del comportamiento del rotor, se ha cre��do necesario probar el molino mediante ensayos de laboratorio a fin de obtener un resultado m��s realista.Abstract Given that it���s difficult to imagine any modern society in the future where energy does not play a crucial role, and as many studies have shown that the actual rate of fuel consumption is unsustainable and harmful to life on the planet, it is essential to raise mankind���s awareness that a change in the current trend is not only necessary, but is also imperative. It is not a question of completely eradicating the use of fossil fuels, as in many countries they are the main or even the only way of generating energy, but rather working towards a balance in generation. To do so it is vital to encourage the development of clean energies, increase technological efficiency and reduce consumption. In view of this we have decided to build a small scale wind turbine rotor which can be used as a study tool for engineering students. To design the turbine a software programme was developed based on aerodynamic concepts, which allows us to calculate the geometry of the blades depending on certain initial conditions, estimate the power of the turbine, and obtain performance curves. One of the main issues with wind technology is its high variability, and therefore we implemented a speed regulation system consisting of a mechanism that varies the orientation of the blades and thus allows us to regulate the power of an electric generator attached to the turbine. Current wind powered generators use this type of system to try to smooth out spikes in power that may be caused by gusts of wind. We have used CAD software to design both the turbine itself and the speed regulation system. Most of the turbine parts have been manufactured with the aid of a 3D printer, while the other metallic parts have been turned on made a lathe in aluminum. Although the software programme which calculates the aerodynamics provide us theoretical data about the operation of the rotor. We consider it necessary to test the wind turbine in a lab to obtain more accurate results.

Flight loads analysis of a maneuvering transport aircraft

The paper provides a method applicable for the determination of flight loads for maneuvering aircraft, in which aerodynamic loads are calculated based on doublet lattice method, which contains three primary steps. Firstly, non-dimensional stability and control derivative coefficients are obtained through solving unsteady aerodynamics in subsonic flow based on a doublet lattice technical. These stability and control derivative coefficients are used in second step. Secondly, the simulation of aircraft dynamic maneuvers is completed utilizing fourth order Runge-Kutta method to solve motion equations in different maneuvers to gain response parameters of aircraft due to the motion of control surfaces. Finally, the response results calculated in the second step are introduced to the calculation of aerodynamic loads. Thus, total loads and loads distribution on different components of aircraft are obtained. According to the above method, abrupt pitching maneuvers, rolling maneuvers and yawing maneuvers are investigated respectively.

Physics of Vibrating Airfoils at Low Reduced Frequency

The unsteady aerodynamics of low pressure turbine vibrating airfoils in flap mode is studied in detail using a frequency domain linearized Navier-Stokes solver. Both the travelling-wave and influence coefficient formulations of the problem are used to highlight key aspects of the physics and understand different trends such as the effect of reduced frequency and Mach number. The study is focused in the low-reduced frequency regime which is of paramount relevance for the design of aeronautical low-pressure turbines and compressors. It is concluded that the effect of the Mach number on the unsteady pressure phase can be neglected in first approximation and that the unsteadiness of the vibrating and adjacent airfoils is driven by vortex shedding mechanisms. Finally a simple model to estimate the work-per-cycle as a function of the reduced frequency and Mach Number is provided. The edge-wise and torsion modes are presented in less detail but it is shown that acoustic waves are essential to explain its behaviour. The non-dimensional work-per-cycle of the edge-wise mode shows a large dependence with the Mach number while in the torsion mode a large number of airfoils is needed to reconstruct the work-per-cycle departing from the influence coefficients.

Improved analytical method to study the cup anemometer performance

The cup anemometer rotor aerodynamics is analytically studied based on the aerodynamics of a single cup. The effect of the rotation on the aerodynamic force is included in the analytical model, together with the displacement of the aerodynamic center during one turn of the cup. The model can be fitted to the testing results, indicating the presence of both the aforementioned effects

Optimization of the Integrated Guidance and Control for a Dual Aerodynamic Control Missile

Las futuras misiones para misiles aire-aire operando dentro de la atm��sfera requieren la interceptaci��n de blancos a mayores velocidades y m��s maniobrables, incluyendo los esperados veh��culos a��reos de combate no tripulados. La intercepci��n tiene que lograrse desde cualquier ��ngulo de lanzamiento. Una de las principales discusiones en la tecnolog��a de misiles en la actualidad es c��mo satisfacer estos nuevos requisitos incrementando la capacidad de maniobra del misil y en paralelo, a trav��s de mejoras en los m��todos de guiado y control modernos. Esta Tesis aborda estos dos objetivos simult��neamente, al proponer un dise��o integrando el guiado y el control de vuelo (autopiloto) y aplicarlo a misiles con control aerodin��mico simult��neo en canard y cola. Un primer avance de los resultados obtenidos ha sido publicado recientemente en el Journal of Aerospace Engineering, en Abril de 2015, [Ibarrondo y Sanz-Aranguez, 2015]. El valor del dise��o integrado obtenido es que permite al misil cumplir con los requisitos operacionales mencionados empleando ��nicamente control aerodin��mico. El dise��o propuesto se compara favorablemente con esquemas m��s tradicionales, consiguiendo menores distancias de paso al blanco y necesitando de menores esfuerzos de control incluso en presencia de ruidos. En esta Tesis se demostrar�� c��mo la introducci��n del doble mando, donde tanto el canard como las aletas de cola son m��viles, puede mejorar las actuaciones de un misil existente. Comparado con un misil con control en cola, el doble control requiere s��lo introducir dos servos adicionales para accionar los canards tambi��n en gui��ada y cabeceo. La secci��n de cola ser�� responsable de controlar el misil en balanceo mediante deflexiones diferenciales de los controles. En el caso del doble mando, la complicaci��n a��adida es que los v��rtices desprendidos de los canards se propagan corriente abajo y pueden incidir sobre las superficies de cola, alterando sus caracter��sticas de control. Como un primer aporte, se ha desarrollado un modelo anal��tico completo para la aerodin��mica no lineal de un misil con doble control, incluyendo la caracterizaci��n de este efecto de acoplamiento aerodin��mico. Hay dos modos de funcionamiento en picado y gui��ada para un misil de doble mando: ���desviaci��n��� y ���opuesto���. En modo ���desviaci��n���, los controles act��an en la misma direcci��n, generando un cambio inmediato en la sustentaci��n y produciendo un movimiento de translaci��n en el misil. La respuesta es r��pida, pero en el modo ���desviaci��n��� los misiles con doble control pueden tener dificultades para alcanzar grandes ��ngulos de ataque y altas aceleraciones laterales. Cuando los controles act��an en direcciones opuestas, el misil rota y el ��ngulo de ataque del fuselaje se incrementa para generar mayores aceleraciones en estado estacionario, aunque el tiempo de respuesta es mayor. Con el modelo aerodin��mico completo, es posible obtener una parametrizaci��n dependiente de los estados de la din��mica de corto periodo del misil. Debido al efecto de acoplamiento entre los controles, la respuesta en bucle abierto no depende linealmente de los controles. El autopiloto se optimiza para obtener la maniobra requerida por la ley de guiado sin exceder ninguno de los l��mites aerodin��micos o mec��nicos del misil. Una segunda contribuci��n de la tesis es el desarrollo de un autopiloto con m��ltiples entradas de control y que integra la aerodin��mica no lineal, controlando los tres canales de picado, gui��ada y cabeceo de forma simult��nea. Las ganancias del autopiloto dependen de los estados del misil y se calculan a cada paso de integraci��n mediante la resoluci��n de una ecuaci��n de Riccati de orden 21x21. Las ganancias obtenidas son sub-��ptimas, debido a que una soluci��n completa de la ecuaci��n de Hamilton-Jacobi-Bellman no puede obtenerse de manera pr��ctica, y se asumen ciertas simplificaciones. Se incorpora asimismo un mecanismo que permite acelerar la respuesta en caso necesario. Como parte del autopiloto, se define una estrategia para repartir el esfuerzo de control entre el canard y la cola. Esto se consigue mediante un controlador aumentado situado antes del bucle de optimizaci��n, que minimiza el esfuerzo total de control para maniobrar. Esta ley de alimentaci��n directa mantiene al misil cerca de sus condiciones de equilibrio, garantizando una respuesta transitoria adecuada. El controlador no lineal elimina la respuesta de fase no-m��nima caracter��stica de la cola. En esta Tesis se consideran dos dise��os para el guiado y control, el control en Doble-Lazo y el control Integrado. En la aproximaci��n de Doble-Lazo, el autopiloto se sit��a dentro de un bucle interior y se dise��a independientemente del guiado, que conforma el bucle m��s exterior del control. Esta estructura asume que existe separaci��n espectral entre los dos, esto es, que los tiempos de respuesta del autopiloto son mucho mayores que los tiempos caracter��sticos del guiado. En el estudio se combina el autopiloto desarrollado con una ley de guiado ��ptimo. Los resultados obtenidos demuestran que se consiguen aumentos muy importantes en las actuaciones frente a misiles con control canard o control en cola, y que la interceptaci��n, cuando se lanza cerca del curso de colisi��n, se consigue desde cualquier ��ngulo alrededor del blanco. Para el misil de doble mando, la estrategia ��ptima resulta en utilizar el modo de control opuesto en la aproximaci��n al blanco y utilizar el modo de desviaci��n justo antes del impacto. Sin embargo la l��gica de doble bucle no consigue el impacto cuando hay desviaciones importantes con respecto al curso de colisi��n. Una de las razones es que parte de la demanda de guiado se pierde, ya que el misil solo es capaz de modificar su aceleraci��n lateral, y no tiene control sobre su aceleraci��n axial, a no ser que incorpore un motor de empuje regulable. La hip��tesis de separaci��n mencionada, y que constituye la base del Doble-Bucle, puede no ser aplicable cuando la din��mica del misil es muy alta en las proximidades del blanco. Si se combinan el guiado y el autopiloto en un ��nico bucle, la informaci��n de los estados del misil est�� disponible para el c��lculo de la ley de guiado, y puede calcularse la estrategia optima de guiado considerando las capacidades y la actitud del misil. Una tercera contribuci��n de la Tesis es la resoluci��n de este segundo dise��o, la integraci��n no lineal del guiado y del autopiloto (IGA) para el misil de doble control. Aproximaciones anteriores en la literatura han planteado este sistema en ejes cuerpo, resultando en un sistema muy inestable debido al bajo amortiguamiento del misil en cabeceo y gui��ada. Las simplificaciones que se tomaron tambi��n causan que el misil se deslice alrededor del blanco y no consiga la intercepci��n. En nuestra aproximaci��n el problema se plantea en ejes inerciales y se recurre a la din��mica de los cuaterniones, eliminado estos inconvenientes. No se limita a la din��mica de corto periodo del misil, porque se construye incluyendo de modo expl��cito la velocidad dentro del bucle de optimizaci��n. La formulaci��n resultante en el IGA es independiente de la maniobra del blanco, que sin embargo se ha de incluir en el c��lculo del modelo en Doble-bucle. Un t��pico inconveniente de los sistemas integrados con controlador proporcional, es el problema de las escalas. Los errores de guiado dominan sobre los errores de posici��n del misil y saturan el controlador, provocando la p��rdida del misil. Este problema se ha tratado aqu�� con un controlador aumentado previo al bucle de optimizaci��n, que define un estado de equilibrio local para el sistema integrado, que pasa a actuar como un regulador. Los criterios de actuaciones para el IGA son los mismos que para el sistema de Doble-Bucle. Sin embargo el problema matem��tico resultante es muy complejo. El problema ��ptimo para tiempo finito resulta en una ecuaci��n diferencial de Riccati con condiciones terminales, que no puede resolverse. Mediante un cambio de variable y la introducci��n de una matriz de transici��n, este problema se transforma en una ecuaci��n diferencial de Lyapunov que puede resolverse mediante m��todos num��ricos. La soluci��n resultante solo es aplicable en un entorno cercano del blanco. Cuando la distancia entre misil y blanco es mayor, se desarrolla una soluci��n aproximada basada en la soluci��n de una ecuaci��n algebraica de Riccati para cada paso de integraci��n. Los resultados que se han obtenido demuestran, a trav��s de an��lisis num��ricos en distintos escenarios, que la soluci��n integrada es mejor que el sistema de Doble-Bucle. Las trayectorias resultantes son muy distintas. El IGA preserva el guiado del misil y consigue maximizar el uso de la propulsi��n, consiguiendo la interceptaci��n del blanco en menores tiempos de vuelo. El sistema es capaz de lograr el impacto donde el Doble-Bucle falla, y adem��s requiere un orden menos de magnitud en la cantidad de c��lculos necesarios. El efecto de los ruidos radar, datos discretos y errores del radomo se investigan. El IGA es m��s robusto, resultando menos afectado por perturbaciones que el Doble- Bucle, especialmente porque el n��cleo de optimizaci��n en el IGA es independiente de la maniobra del blanco. La estimaci��n de la maniobra del blanco es siempre imprecisa y contaminada por ruido, y degrada la precisi��n de la soluci��n de Doble-Bucle. Finalmente, como una cuarta contribuci��n, se demuestra que el misil con guiado IGA es capaz de realizar una maniobra de defensa contra un blanco que ataque por su cola, s��lo con control aerodin��mico. Las trayectorias estudiadas consideran una fase pre-programada de alta velocidad de giro, manteniendo siempre el misil dentro de su envuelta de vuelo. Este procedimiento no necesita recurrir a soluciones t��cnicamente m��s complejas como el control vectorial del empuje o control por chorro para ejecutar esta maniobra. En todas las demostraciones matem��ticas se utiliza el producto de Kronecker como una herramienta practica para manejar las parametrizaciones dependientes de variables, que resultan en matrices de grandes dimensiones. ABSTRACT Future missions for air to air endo-atmospheric missiles require the interception of targets with higher speeds and more maneuverable, including forthcoming unmanned supersonic combat vehicles. The interception will need to be achieved from any angle and off-boresight launch conditions. One of the most significant discussions in missile technology today is how to satisfy these new operational requirements by increasing missile maneuvering capabilities and in parallel, through the development of more advanced guidance and control methods. This Thesis addresses these two objectives by proposing a novel optimal integrated guidance and autopilot design scheme, applicable to more maneuverable missiles with forward and rearward aerodynamic controls. A first insight of these results have been recently published in the Journal of Aerospace Engineering in April 2015, [Ibarrondo and Sanz-Ar��nguez, 2015]. The value of this integrated solution is that it allows the missile to comply with the aforementioned requirements only by applying aerodynamic control. The proposed design is compared against more traditional guidance and control approaches with positive results, achieving reduced control efforts and lower miss distances with the integrated logic even in the presence of noises. In this Thesis it will be demonstrated how the dual control missile, where canard and tail fins are both movable, can enhance the capabilities of an existing missile airframe. Compared to a tail missile, dual control only requires two additional servos to actuate the canards in pitch and yaw. The tail section will be responsible to maintain the missile stabilized in roll, like in a classic tail missile. The additional complexity is that the vortices shed from the canard propagate downstream where they interact with the tail surfaces, altering the tail expected control characteristics. These aerodynamic phenomena must be properly described, as a preliminary step, with high enough precision for advanced guidance and control studies. As a first contribution we have developed a full analytical model of the nonlinear aerodynamics of a missile with dual control, including the characterization of this cross-control coupling effect. This development has been produced from a theoretical model validated with reliable practical data obtained from wind tunnel experiments available in the scientific literature, complement with computer fluid dynamics and semi-experimental methods. There are two modes of operating a missile with forward and rear controls, ���divert��� and ���opposite��� modes. In divert mode, controls are deflected in the same direction, generating an increment in direct lift and missile translation. Response is fast, but in this mode, dual control missiles may have difficulties in achieving large angles of attack and high level of lateral accelerations. When controls are deflected in opposite directions (opposite mode) the missile airframe rotates and the body angle of attack is increased to generate greater accelerations in steady-state, although the response time is larger. With the aero-model, a state dependent parametrization of the dual control missile short term dynamics can be obtained. Due to the cross-coupling effect, the open loop dynamics for the dual control missile is not linearly dependent of the fin positions. The short term missile dynamics are blended with the servo system to obtain an extended autopilot model, where the response is linear with the control fins turning rates, that will be the control variables. The flight control loop is optimized to achieve the maneuver required by the guidance law without exceeding any of the missile aerodynamic or mechanical limitations. The specific aero-limitations and relevant performance indicators for the dual control are set as part of the analysis. A second contribution of this Thesis is the development of a step-tracking multi-input autopilot that integrates non-linear aerodynamics. The designed dual control missile autopilot is a full three dimensional autopilot, where roll, pitch and yaw are integrated, calculating command inputs simultaneously. The autopilot control gains are state dependent, and calculated at each integration step solving a matrix Riccati equation of order 21x21. The resulting gains are sub-optimal as a full solution for the Hamilton-Jacobi-Bellman equation cannot be resolved in practical terms and some simplifications are taken. Acceleration mechanisms with an ��-shift is incorporated in the design. As part of the autopilot, a strategy is defined for proper allocation of control effort between canard and tail channels. This is achieved with an augmented feed forward controller that minimizes the total control effort of the missile to maneuver. The feedforward law also maintains the missile near trim conditions, obtaining a well manner response of the missile. The nonlinear controller proves to eliminate the non-minimum phase effect of the tail. Two guidance and control designs have been considered in this Thesis: the Two- Loop and the Integrated approaches. In the Two-Loop approach, the autopilot is placed in an inner loop and designed separately from an outer guidance loop. This structure assumes that spectral separation holds, meaning that the autopilot response times are much higher than the guidance command updates. The developed nonlinear autopilot is linked in the study to an optimal guidance law. Simulations are carried on launching close to collision course against supersonic and highly maneuver targets. Results demonstrate a large boost in performance provided by the dual control versus more traditional canard and tail missiles, where interception with the dual control close to collision course is achieved form 365deg all around the target. It is shown that for the dual control missile the optimal flight strategy results in using opposite control in its approach to target and quick corrections with divert just before impact. However the Two-Loop logic fails to achieve target interception when there are large deviations initially from collision course. One of the reasons is that part of the guidance command is not followed, because the missile is not able to control its axial acceleration without a throttleable engine. Also the separation hypothesis may not be applicable for a high dynamic vehicle like a dual control missile approaching a maneuvering target. If the guidance and autopilot are combined into a single loop, the guidance law will have information of the missile states and could calculate the most optimal approach to the target considering the actual capabilities and attitude of the missile. A third contribution of this Thesis is the resolution of the mentioned second design, the non-linear integrated guidance and autopilot (IGA) problem for the dual control missile. Previous approaches in the literature have posed the problem in body axes, resulting in high unstable behavior due to the low damping of the missile, and have also caused the missile to slide around the target and not actually hitting it. The IGA system is posed here in inertial axes and quaternion dynamics, eliminating these inconveniences. It is not restricted to the missile short term dynamic, and we have explicitly included the missile speed as a state variable. The IGA formulation is also independent of the target maneuver model that is explicitly included in the Two-loop optimal guidance law model. A typical problem of the integrated systems with a proportional control law is the problem of scales. The guidance errors are larger than missile state errors during most of the flight and result in high gains, control saturation and loss of control. It has been addressed here with an integrated feedforward controller that defines a local equilibrium state at each flight point and the controller acts as a regulator to minimize the IGA states excursions versus the defined feedforward state. The performance criteria for the IGA are the same as in the Two-Loop case. However the resulting optimization problem is mathematically very complex. The optimal problem in a finite-time horizon results in an irresoluble state dependent differential Riccati equation with terminal conditions. With a change of variable and the introduction of a transition matrix, the equation is transformed into a time differential Lyapunov equation that can be solved with known numerical methods in real time. This solution results range limited, and applicable when the missile is in a close neighborhood of the target. For larger ranges, an approximate solution is used, obtained from solution of an algebraic matrix Riccati equation at each integration step. The results obtained show, by mean of several comparative numerical tests in diverse homing scenarios, than the integrated approach is a better solution that the Two- Loop scheme. Trajectories obtained are very different in the two cases. The IGA fully preserves the guidance command and it is able to maximize the utilization of the missile propulsion system, achieving interception with lower miss distances and in lower flight times. The IGA can achieve interception against off-boresight targets where the Two- Loop was not able to success. As an additional advantage, the IGA also requires one order of magnitude less calculations than the Two-Loop solution. The effects of radar noises, discrete radar data and radome errors are investigated. IGA solution is robust, and less affected by radar than the Two-Loop, especially because the target maneuvers are not part of the IGA core optimization loop. Estimation of target acceleration is always imprecise and noisy and degrade the performance of the two-Loop solution. The IGA trajectories are such that minimize the impact of radome errors in the guidance loop. Finally, as a fourth contribution, it is demonstrated that the missile with IGA guidance is capable of performing a defense against attacks from its rear hemisphere, as a tail attack, only with aerodynamic control. The studied trajectories have a preprogrammed high rate turn maneuver, maintaining the missile within its controllable envelope. This solution does not recur to more complex features in service today, like vector control of the missile thrust or side thrusters. In all the mathematical treatments and demonstrations, the Kronecker product has been introduced as a practical tool to handle the state dependent parametrizations that have resulted in very high order matrix equations.

Urban wind energy: empirical optimization of high-rise building roof shape for the wind energy exploitation

El programa Europeo HORIZON2020 en Futuras Ciudades Inteligentes establece como objetivo que el 20% de la energ��a el��ctrica sea generada a partir de fuentes renovables. Este objetivo implica la necesidad de potenciar la generaci��n de energ��a e��lica en todos los ��mbitos. La energ��a e��lica reduce dr��sticamente las emisiones de gases de efecto invernadero y evita los riesgos geo-pol��ticos asociados al suministro e infraestructuras energ��ticas, as�� como la dependencia energ��tica de otras regiones. Adem��s, la generaci��n de energ��a distribuida (generaci��n en el punto de consumo) presenta significativas ventajas en t��rminos de elevada eficiencia energ��tica y estimulaci��n de la econom��a. El sector de la edificaci��n representa el 40% del consumo energ��tico total de la Uni��n Europea. La reducci��n del consumo energ��tico en este ��rea es, por tanto, una prioridad de acuerdo con los objetivos "20-20-20" en eficiencia energ��tica. La Directiva 2010/31/EU del Parlamento Europeo y del Consejo de 19 de mayo de 2010 sobre el comportamiento energ��tico de edificaciones contempla la instalaci��n de sistemas de suministro energ��tico a partir de fuentes renovables en las edificaciones de nuevo dise��o. Actualmente existe una escasez de conocimiento cient��fico y tecnol��gico acerca de la geometr��a ��ptima de las edificaciones para la explotaci��n de la energ��a e��lica en entornos urbanos. El campo tecnol��gico de estudio de la presente Tesis Doctoral es la generaci��n de energ��a e��lica en entornos urbanos. Espec��ficamente, la optimization de la geometr��a de las cubiertas de edificaciones desde el punto de vista de la explotaci��n del recurso energ��tico e��lico. Debido a que el flujo del viento alrededor de las edificaciones es exhaustivamente investigado en esta Tesis empleando herramientas de simulaci��n num��rica, la mec��nica de fluidos computacional (CFD en ingl��s) y la aerodin��mica de edificaciones son los campos cient��ficos de estudio. El objetivo central de esta Tesis Doctoral es obtener una geometr��a de altas prestaciones (u ��ptima) para la explotaci��n de la energ��a e��lica en cubiertas de edificaciones de gran altura. Este objetivo es alcanzado mediante un an��lisis exhaustivo de la influencia de la forma de la cubierta del edificio en el flujo del viento desde el punto de vista de la explotaci��n energ��tica del recurso e��lico empleando herramientas de simulaci��n num��rica (CFD). Adicionalmente, la geometr��a de la edificaci��n convencional (edificio prism��tico) es estudiada, y el posicionamiento adecuado para los diferentes tipos de aerogeneradores es propuesto. La compatibilidad entre el aprovechamiento de las energ��as solar fotovoltaica y e��lica tambi��n es analizado en este tipo de edificaciones. La investigaci��n prosigue con la optimizaci��n de la geometr��a de la cubierta. La metodolog��a con la que se obtiene la geometr��a ��ptima consta de las siguientes etapas: - Verificaci��n de los resultados de las geometr��as previamente estudiadas en la literatura. Las geometr��as b��sicas que se someten a examen son: cubierta plana, a dos aguas, inclinada, abovedada y esf��rica. - An��lisis de la influencia de la forma de las aristas de la cubierta sobre el flujo del viento. Esta tarea se lleva a cabo mediante la comparaci��n de los resultados obtenidos para la arista convencional (esquina sencilla) con un parapeto, un voladizo y una esquina curva. - An��lisis del acoplamiento entre la cubierta y los cerramientos verticales (paredes) mediante la comparaci��n entre diferentes variaciones de una cubierta esf��rica en una edificaci��n de gran altura: cubierta esf��rica estudiada en la literatura, cubierta esf��rica integrada geom��tricamente con las paredes (planta cuadrada en el suelo) y una cubierta esf��rica acoplada a una pared cilindrica. El comportamiento del flujo sobre la cubierta es estudiado tambi��n considerando la posibilidad de la variaci��n en la direcci��n del viento incidente. - An��lisis del efecto de las proporciones geom��tricas del edificio sobre el flujo en la cubierta. - An��lisis del efecto de la presencia de edificaciones circundantes sobre el flujo del viento en la cubierta del edificio objetivo. Las contribuciones de la presente Tesis Doctoral pueden resumirse en: - Se demuestra que los modelos de turbulencia RANS obtienen mejores resultados para la simulaci��n del viento alrededor de edificaciones empleando los coeficientes propuestos por Crespo y los propuestos por Bechmann y S��rensen que empleando los coeficientes est��ndar. - Se demuestra que la estimaci��n de la energ��a cin��tica turbulenta del flujo empleando modelos de turbulencia RANS puede ser validada manteniendo el enfoque en la cubierta de la edificaci��n. - Se presenta una nueva modificaci��n del modelo de turbulencia Durbin k ��� e que reproduce mejor la distancia de recirculaci��n del flujo de acuerdo con los resultados experimentales. - Se demuestra una relaci��n lineal entre la distancia de recirculaci��n en una cubierta plana y el factor constante involucrado en el c��lculo de la escala de tiempo de la velocidad turbulenta. Este resultado puede ser empleado por la comunidad cient��fica para la mejora del modelado de la turbulencia en diversas herramientas computacionales (OpenFOAM, Fluent, CFX, etc.). - La compatibilidad entre las energ��as solar fotovoltaica y e��lica en cubiertas de edificaciones es analizada. Se demuestra que la presencia de los m��dulos solares provoca un descenso en la intensidad de turbulencia. - Se demuestran conflictos en el cambio de escala entre simulaciones de edificaciones a escala real y simulaciones de modelos a escala reducida (t��nel de viento). Se demuestra que para respetar las limitaciones de similitud (n��mero de Reynolds) son necesarias mediciones en edificaciones a escala real o experimentos en t��neles de viento empleando agua como fluido, especialmente cuando se trata con geometr��as complejas, como es el caso de los m��dulos solares. - Se determina el posicionamiento m��s adecuado para los diferentes tipos de aerogeneradores tomando en consideraci��n la velocidad e intensidad de turbulencia del flujo. El posicionamiento de aerogeneradores es investigado en las geometr��as de cubierta m��s habituales (plana, a dos aguas, inclinada, abovedada y esf��rica). - Las formas de aristas m��s habituales (esquina, parapeto, voladizo y curva) son analizadas, as�� como su efecto sobre el flujo del viento en la cubierta de un edificio de gran altura desde el punto de vista del aprovechamiento e��lico. - Se propone una geometr��a ��ptima (o de altas prestaciones) para el aprovechamiento de la energ��a e��lica urbana. Esta optimizaci��n incluye: verificaci��n de las geometr��as estudiadas en el estado del arte, an��lisis de la influencia de las aristas de la cubierta en el flujo del viento, estudio del acoplamiento entre la cubierta y las paredes, an��lisis de sensibilidad del grosor de la cubierta, exploraci��n de la influencia de las proporciones geom��tricas de la cubierta y el edificio, e investigaci��n del efecto de las edificaciones circundantes (considerando diferentes alturas de los alrededores) sobre el flujo del viento en la cubierta del edificio objetivo. Las investigaciones comprenden el an��lisis de la velocidad, la energ��a cin��tica turbulenta y la intensidad de turbulencia en todos los casos. ABSTRACT The HORIZON2020 European program in Future Smart Cities aims to have 20% of electricity produced by renewable sources. This goal implies the necessity to enhance the wind energy generation, both with large and small wind turbines. Wind energy drastically reduces carbon emissions and avoids geo-political risks associated with supply and infrastructure constraints, as well as energy dependence from other regions. Additionally, distributed energy generation (generation at the consumption site) offers significant benefits in terms of high energy efficiency and stimulation of the economy. The buildings sector represents 40% of the European Union total energy consumption. Reducing energy consumption in this area is therefore a priority under the "20-20-20" objectives on energy efficiency. The Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings aims to consider the installation of renewable energy supply systems in new designed buildings. Nowadays, there is a lack of knowledge about the optimum building shape for urban wind energy exploitation. The technological field of study of the present Thesis is the wind energy generation in urban environments. Specifically, the improvement of the building-roof shape with a focus on the wind energy resource exploitation. Since the wind flow around buildings is exhaustively investigated in this Thesis using numerical simulation tools, both computational fluid dynamics (CFD) and building aerodynamics are the scientific fields of study. The main objective of this Thesis is to obtain an improved (or optimum) shape of a high-rise building for the wind energy exploitation on the roof. To achieve this objective, an analysis of the influence of the building shape on the behaviour of the wind flow on the roof from the point of view of the wind energy exploitation is carried out using numerical simulation tools (CFD). Additionally, the conventional building shape (prismatic) is analysed, and the adequate positions for different kinds of wind turbines are proposed. The compatibility of both photovoltaic-solar and wind energies is also analysed for this kind of buildings. The investigation continues with the buildingroof optimization. The methodology for obtaining the optimum high-rise building roof shape involves the following stages: - Verification of the results of previous building-roof shapes studied in the literature. The basic shapes that are compared are: flat, pitched, shed, vaulted and spheric. - Analysis of the influence of the roof-edge shape on the wind flow. This task is carried out by comparing the results obtained for the conventional edge shape (simple corner) with a railing, a cantilever and a curved edge. - Analysis of the roof-wall coupling by testing different variations of a spherical roof on a high-rise building: spherical roof studied in the litera ture, spherical roof geometrically integrated with the walls (squared-plant) and spherical roof with a cylindrical wall. The flow behaviour on the roof according to the variation of the incident wind direction is commented. - Analysis of the effect of the building aspect ratio on the flow. - Analysis of the surrounding buildings effect on the wind flow on the target building roof. The contributions of the present Thesis can be summarized as follows: - It is demonstrated that RANS turbulence models obtain better results for the wind flow around buildings using the coefficients proposed by Crespo and those proposed by Bechmann and S0rensen than by using the standard ones. - It is demonstrated that RANS turbulence models can be validated for turbulent kinetic energy focusing on building roofs. - A new modification of the Durbin k ��� e turbulence model is proposed in order to obtain a better agreement of the recirculation distance between CFD simulations and experimental results. - A linear relationship between the recirculation distance on a flat roof and the constant factor involved in the calculation of the turbulence velocity time scale is demonstrated. This discovery can be used by the research community in order to improve the turbulence modeling in different solvers (OpenFOAM, Fluent, CFX, etc.). - The compatibility of both photovoltaic-solar and wind energies on building roofs is demonstrated. A decrease of turbulence intensity due to the presence of the solar panels is demonstrated. - Scaling issues are demonstrated between full-scale buildings and windtunnel reduced-scale models. The necessity of respecting the similitude constraints is demonstrated. Either full-scale measurements or wind-tunnel experiments using water as a medium are needed in order to accurately reproduce the wind flow around buildings, specially when dealing with complex shapes (as solar panels, etc.). - The most adequate position (most adequate roof region) for the different kinds of wind turbines is highlighted attending to both velocity and turbulence intensity. The wind turbine positioning was investigated for the most habitual kind of building-roof shapes (flat, pitched, shed, vaulted and spherical). - The most habitual roof-edge shapes (simple edge, railing, cantilever and curved) were investigated, and their effect on the wind flow on a highrise building roof were analysed from the point of view of the wind energy exploitation. - An optimum building-roof shape is proposed for the urban wind energy exploitation. Such optimization includes: state-of-the-art roof shapes test, analysis of the influence of the roof-edge shape on the wind flow, study of the roof-wall coupling, sensitivity analysis of the roof width, exploration of the aspect ratio of the building-roof shape and investigation of the effect of the neighbouring buildings (considering different surrounding heights) on the wind now on the target building roof. The investigations comprise analysis of velocity, turbulent kinetic energy and turbulence intensity for all the cases.

Aerodin��mica experimental de elementos de parques energ��ticos

La creciente demanda de energ��a el��ctrica y la necesidad de implementar energ��as no contaminantes hace que las llamadas tecnolog��as verdes sean cada d��a m��s solicitadas. Entre estas tecnolog��as encontramos la energ��a solar y la energ��a e��lica; ambas tienen una trayectoria de uso e investigaci��n bastante amplia, sin embargo a��n presentan problemas de fondo que impiden dar mayor impulso a su uso. El objetivo de la presente tesis es presentar soluciones a problemas de optimizaci��n en campos conversores de energ��a. Para ello se analizan y resuelven dos problemas por medio de t��cnicas de aerodin��mica experimental: el primero sobre campos de colectores solares y el segundo sobre campos e��licos. Las t��cnicas de medici��n utilizadas en aerodin��mica, y en el presente trabajo, son: medici��n de cargas, anemometr��a de hilo caliente, velocimetr��a por imagen de part��culas y escaneo de presiones; adem��s de un an��lisis estad��stico de los datos. En el primer caso se ensayan experimentalmente colectores solares parab��licos en donde, por cuestiones de seguridad o por protecci��n contra el viento, se utilizan cercas. ��stas modifican el comportamiento del flujo corriente abajo y se ha encontrado que la distancia a la cual se colocan, as�� como el tipo de cercas (s��lida o permeable), modifican las cargas estructurales a las que los colectores est��n expuestos. Los resultados demuestran que existe una distancia cr��tica en la cual la presencia de la cerca aumenta la carga en lugar de disminuirla, por lo cual la selecci��n adecuada del parapeto y la distancia a la cual se coloca son de suma importancia para la optimizaci��n de la estructura. En el segundo caso se ensaya experimentalmente y simula num��ricamente la estela de turbinas e��licas por medio de discos porosos. En donde un disco permeable simula el rotor de una turbina. El disco es capaz de semejar la estela y los efectos que ��sta puede causar corriente abajo. Los resultados muestran que seleccionando adecuadamente la porosidad, es posible simular coeficientes de empuje similares a los desarrollados por los aerogeneradores, adem��s la estela y sus efectos son semejantes a los medidos en campo. ABSTRACT The called green energy technologies are increasingly required because of the growing demand for electricity and the need to implement nonpolluting energy. Among the green energy technologies it is found the solar and the wind energy, both have a history of use and fairly extensive research; however they still have problems which limit to give them further impetus to its use. The aim of this thesis is to present solutions to optimization problems in energy harvesting. To this end it is analysed, and solved, two problems by means of techniques in experimental aerodynamics: the first issue with regard to parabolic troughs and the second about wind farms. The measurement techniques commonly used in aerodynamics, and used in this research work, are: measurement of loads, hot wire anemometry, particle image velocimetry and scanning of pressures; where data are collected and then an statistical analysis is done. In the first case it is tested parabolic troughs where, either for security reasons or protection against the wind actions, fences are used. These fences modify the behaviour of flow downstream and it was found that the distance at which they are placed, and the type of fences (solid or permeable) modify the structural loads to which the parabolic troughs are exposed. The results show that there is a critical distance at which the presence of the fence increases the load instead of protecting the parabolic trough, hence making the proper selection of the parapet and the distance at which it stands are paramount for the optimization of the structure. In the second case it is tested, experimentally and numerically, the wake of wind turbines by means of porous disks; where the permeable disc simulates a turbine rotor. The disc is able to mimic the wake and the effects that it can cause downstream. The results show that by properly selecting the porosity, it is possible to simulate drag coefficients similar to those developed by wind turbines; moreover the porous disk wake and its effects are similar to those measured on field.

Tridimensional simulation of the speed, pressure and turbulence fields of the air flow on the geometry of a freight truck inside a wind tunnel

This study shows the air flow behavior through the geometry of a freight truck inside a AF6109 wind tunnel with the purpose to predict the speed, pressure and turbulence fields made by the air flow, to decrease the aerodynamic resistance, to calculate the dragging coefficient, to evaluate the aerodynamics of the geometry of the prototype using the CFD technique and to compare the results of the simulation with the results obtained experimentally with the ���PETER 739 HAULER��� scaled freight truck model located on the floor of the test chamber. The Geometry went through a numerical simulation process using the CFX 5,7. The obtained results showed the behavior of the air flow through the test chamber, and also it showed the variations of speed and pressure at the exit of the chamber and the calculations of the coefficient and the dragging force on the geometry of the freight truck. The evaluation of the aerodynamics showed that the aerodynamic deflector is a device that helped the reduction the dragging produced in a significant way by the air. Furthermore, the dragging coefficient and force on the prototype freight truck could be estimated establishing an incomplete similarity.