Aerodynamic Optimization of the Nose Shape of a High-speed Train

La influencia de la aerodinámica en el diseño de los trenes de alta velocidad, unida a la necesidad de resolver nuevos problemas surgidos con el aumento de la velocidad de circulación y la reducción de peso del vehículo, hace evidente el interés de plantear un estudio de optimización que aborde tales puntos. En este contexto, se presenta en esta tesis la optimización aerodinámica del testero de un tren de alta velocidad, llevada a cabo mediante el uso de métodos de optimización avanzados. Entre estos métodos, se ha elegido aquí a los algoritmos genéticos y al método adjunto como las herramientas para llevar a cabo dicha optimización. La base conceptual, las características y la implementación de los mismos se detalla a lo largo de la tesis, permitiendo entender los motivos de su elección, y las consecuencias, en términos de ventajas y desventajas que cada uno de ellos implican. El uso de los algorimos genéticos implica a su vez la necesidad de una parametrización geométrica de los candidatos a óptimo y la generación de un modelo aproximado que complementa al método de optimización. Estos puntos se describen de modo particular en el primer bloque de la tesis, enfocada a la metodología seguida en este estudio. El segundo bloque se centra en la aplicación de los métodos a fin de optimizar el comportamiento aerodinámico del tren en distintos escenarios. Estos escenarios engloban los casos más comunes y también algunos de los más exigentes a los que hace frente un tren de alta velocidad: circulación en campo abierto con viento frontal o viento lateral, y entrada en túnel. Considerando el caso de viento frontal en campo abierto, los dos métodos han sido aplicados, permitiendo una comparación de las diferentes metodologías, así como el coste computacional asociado a cada uno, y la minimización de la resistencia aerodinámica conseguida en esa optimización. La posibilidad de evitar parametrizar la geometría y, por tanto, reducir el coste computacional del proceso de optimización es la característica más significativa de los métodos adjuntos, mientras que en el caso de los algoritmos genéticos se destaca la simplicidad y capacidad de encontrar un óptimo global en un espacio de diseño multi-modal o de resolver problemas multi-objetivo. El caso de viento lateral en campo abierto considera nuevamente los dos métoxi dos de optimización anteriores. La parametrización se ha simplificado en este estudio, lo que notablemente reduce el coste numérico de todo el estudio de optimización, a la vez que aún recoge las características geométricas más relevantes en un tren de alta velocidad. Este análisis ha permitido identificar y cuantificar la influencia de cada uno de los parámetros geométricos incluídos en la parametrización, y se ha observado que el diseño de la arista superior a barlovento es fundamental, siendo su influencia mayor que la longitud del testero o que la sección frontal del mismo. Finalmente, se ha considerado un escenario más a fin de validar estos métodos y su capacidad de encontrar un óptimo global. La entrada de un tren de alta velocidad en un túnel es uno de los casos más exigentes para un tren por el pico de sobrepresión generado, el cual afecta a la confortabilidad del pasajero, así como a la estabilidad del vehículo y al entorno próximo a la salida del túnel. Además de este problema, otro objetivo a minimizar es la resistencia aerodinámica, notablemente superior al caso de campo abierto. Este problema se resuelve usando algoritmos genéticos. Dicho método permite obtener un frente de Pareto donde se incluyen el conjunto de óptimos que minimizan ambos objetivos. ABSTRACT Aerodynamic design of trains influences several aspects of high-speed trains performance in a very significant level. In this situation, considering also that new aerodynamic problems have arisen due to the increase of the cruise speed and lightness of the vehicle, it is evident the necessity of proposing an optimization study concerning the train aerodynamics. Thus, the aerodynamic optimization of the nose shape of a high-speed train is presented in this thesis. This optimization is based on advanced optimization methods. Among these methods, genetic algorithms and the adjoint method have been selected. A theoretical description of their bases, the characteristics and the implementation of each method is detailed in this thesis. This introduction permits understanding the causes of their selection, and the advantages and drawbacks of their application. The genetic algorithms requirethe geometrical parameterization of any optimal candidate and the generation of a metamodel or surrogate model that complete the optimization process. These points are addressed with a special attention in the first block of the thesis, focused on the methodology considered in this study. The second block is referred to the use of these methods with the purpose of optimizing the aerodynamic performance of a high-speed train in several scenarios. These scenarios englobe the most representative operating conditions of high-speed trains, and also some of the most exigent train aerodynamic problems: front wind and cross-wind situations in open air, and the entrance of a high-speed train in a tunnel. The genetic algorithms and the adjoint method have been applied in the minimization of the aerodynamic drag on the train with front wind in open air. The comparison of these methods allows to evaluate the methdology and computational cost of each one, as well as the resulting minimization of the aerodynamic drag. Simplicity and robustness, the straightforward realization of a multi-objective optimization, and the capability of searching a global optimum are the main attributes of genetic algorithm. However, the requirement of geometrically parameterize any optimal candidate is a significant drawback that is avoided with the use of the adjoint method. This independence of the number of design variables leads to a relevant reduction of the pre-processing and computational cost. Considering the cross-wind stability, both methods are used again for the minimization of the side force. In this case, a simplification of the geometric parameterization of the train nose is adopted, what dramatically reduces the computational cost of the optimization process. Nevertheless, some of the most important geometrical characteristics are still described with this simplified parameterization. This analysis identifies and quantifies the influence of each design variable on the side force on the train. It is observed that the A-pillar roundness is the most demanding design parameter, with a more important effect than the nose length or the train cross-section area. Finally, a third scenario is considered for the validation of these methods in the aerodynamic optimization of a high-speed train. The entrance of a train in a tunnel is one of the most exigent train aerodynamic problems. The aerodynamic consequences of high-speed trains running in a tunnel are basically resumed in two correlated phenomena, the generation of pressure waves and an increase in aerodynamic drag. This multi-objective optimization problem is solved with genetic algorithms. The result is a Pareto front where a set of optimal solutions that minimize both objectives.

Simulación de componentes no estacionarias de viento en orografías complejas

Realistic operation of helicopter flight simulators in complex topographies (such as urban environments) requires appropriate prediction of the incoming wind, and this prediction should be made in real time. Unfortunately, the wind topology around complex topographies shows time-dependent, fully nonlinear, turbulent patterns (i.e., wakes) whose simulation cannot be made using computationally inexpensive tools based on corrected potential approximations. Instead, the full Navier-Stokes plus some kind of turbulent modeling is necessary, which is quite computationally expensive. The complete unsteady flow depends on two parameters, namely the velocity and orientation of the free stream flow. The aim of this MSc thesis is to develop a methodology for the real time simulation of these complex flows. For simplicity, the flow around a single building (20 mx20 m cross section and 100 m height) is considered, with free stream velocity in the range 5-25 m/s. Because of the square cross section, the problem shows two reflection symmetries, which allows for restricting the orientations to the range 0° < a. < 45°. The methodology includes an offline preprocess and the online operation. The preprocess consists in three steps: An appropriate, unstructured mesh is selected in which the flow is sim¬ulated using OpenFOAM, and this is done for 33 combinations of 3 free stream intensities and 11 orientations. For each of these, the simulation proceeds for a sufficiently large time as to eliminate transients. This step is quite computationally expensive. Each flow field is post-processed using a combination of proper orthogonal decomposition, fast Fourier transform, and a convenient optimization tool, which identifies the relevant frequencies (namely, both the basic frequencies and their harmonics) and modes in the computational mesh. This combination includes several new ingredients to filter errors out and identify the relevant spatio-temporal patterns. Note that, in principle, the basic frequencies depend on both the intensity and the orientation of the free stream flow. The outcome of this step is a set of modes (vectors containing the three velocity components at all mesh points) for the various Fourier components, intensities, and orientations, which can be organized as a third order tensor. This step is fairly computationally inexpensive. The above mentioned tensor is treated using a combination of truncated high order singular value, decomposition and appropriate one-dimensional interpolation (as in Lorente, Velazquez, Vega, J. Aircraft, 45 (2008) 1779-1788). The outcome is a tensor representation of both the relevant fre¬quencies and the associated Fourier modes for a given pair of values of the free stream flow intensity and orientation. This step is fairly compu¬tationally inexpensive. The online, operation requires just reconstructing the time-dependent flow field from its Fourier representation, which is extremely computationally inex¬pensive. The whole method is quite robust.

Predicción de la velocidad crítica de flameo mediante el uso de modelos aeroelásticos extrapolados en tiempo real con datos de vuelo

La Aeroelasticidad fue definida por Arthur Collar en 1947 como "el estudio de la interacción mutua entre fuerzas inerciales, elásticas y aerodinámicas actuando sobre elementos estructurales expuestos a una corriente de aire". Actualmente, esta definición se ha extendido hasta abarcar la influencia del control („Aeroservoelasticidad‟) e, incluso, de la temperatura („Aerotermoelasticidad‟). En el ámbito de la Ingeniería Aeronáutica, los fenómenos aeroelásticos, tanto estáticos (divergencia, inversión de mando) como dinámicos (flameo, bataneo) son bien conocidos desde los inicios de la Aviación. Las lecciones aprendidas a lo largo de la Historia Aeronáutica han permitido establecer criterios de diseño destinados a mitigar la probabilidad de sufrir fenómenos aeroelásticos adversos durante la vida operativa de una aeronave. Adicionalmente, el gran avance experimentado durante esta última década en el campo de la Aerodinámica Computacional y en la modelización aeroelástica ha permitido mejorar la fiabilidad en el cálculo de las condiciones de flameo de una aeronave en su fase de diseño. Sin embargo, aún hoy, los ensayos en vuelo siguen siendo necesarios para validar modelos aeroelásticos, verificar que la aeronave está libre de inestabilidades aeroelásticas y certificar sus distintas envolventes. En particular, durante el proceso de expansión de la envolvente de una aeronave en altitud/velocidad, se requiere predecir en tiempo real las condiciones de flameo y, en consecuencia, evitarlas. A tal efecto, en el ámbito de los ensayos en vuelo, se han desarrollado diversas metodologías que predicen, en tiempo real, las condiciones de flameo en función de condiciones de vuelo ya verificadas como libres de inestabilidades aeroelásticas. De entre todas ellas, aquella que relaciona el amortiguamiento y la velocidad con un parámetro específico definido como „Margen de Flameo‟ (Flutter Margin), permanece como la técnica más común para proceder con la expansión de Envolventes en altitud/velocidad. No obstante, a pesar de su popularidad y facilidad de aplicación, dicha técnica no es adecuada cuando en la aeronave a ensayar se hallan presentes no-linealidades mecánicas como, por ejemplo, holguras. En particular, en vuelos de ensayo dedicados específicamente a expandir la envolvente en altitud/velocidad, las condiciones de „Oscilaciones de Ciclo Límite‟ (Limit Cycle Oscillations, LCOs) no pueden ser diferenciadas de manera precisa de las condiciones de flameo, llevando a una determinación excesivamente conservativa de la misma. La presente Tesis desarrolla una metodología novedosa, basada en el concepto de „Margen de Flameo‟, que permite predecir en tiempo real las condiciones de „Ciclo Límite‟, siempre que existan, distinguiéndolas de las de flameo. En una primera parte, se realiza una revisión bibliográfica de la literatura acerca de los diversos métodos de ensayo existentes para efectuar la expansión de la envolvente de una aeronave en altitud/velocidad, el efecto de las no-linealidades mecánicas en el comportamiento aeroelástico de dicha aeronave, así como una revisión de las Normas de Certificación civiles y militares respecto a este tema. En una segunda parte, se propone una metodología de expansión de envolvente en tiempo real, basada en el concepto de „Margen de Flameo‟, que tiene en cuenta la presencia de no-linealidades del tipo holgura en el sistema aeroelástico objeto de estudio. Adicionalmente, la metodología propuesta se valida contra un modelo aeroelástico bidimensional paramétrico e interactivo programado en Matlab. Para ello, se plantean las ecuaciones aeroelásticas no-estacionarias de un perfil bidimensional en la formulación espacio-estado y se incorpora la metodología anterior a través de un módulo de análisis de señal y otro módulo de predicción. En una tercera parte, se comparan las conclusiones obtenidas con las expuestas en la literatura actual y se aplica la metodología propuesta a resultados experimentales de ensayos en vuelo reales. En resumen, los principales resultados de esta Tesis son: 1. Resumen del estado del arte en los métodos de ensayo aplicados a la expansión de envolvente en altitud/velocidad y la influencia de no-linealidades mecánicas en la determinación de la misma. 2. Revisión de la normas de Certificación Civiles y las normas Militares en relación a la verificación aeroelástica de aeronaves y los límites permitidos en presencia de no-linealidades. 3. Desarrollo de una metodología de expansión de envolvente basada en el Margen de Flameo. 4. Validación de la metodología anterior contra un modelo aeroelástico bidimensional paramétrico e interactivo programado en Matlab/Simulink. 5. Análisis de los resultados obtenidos y comparación con resultados experimentales. ABSTRACT Aeroelasticity was defined by Arthur Collar in 1947 as “the study of the mutual interaction among inertia, elastic and aerodynamic forces when acting on structural elements surrounded by airflow”. Today, this definition has been updated to take into account the Controls („Aeroservoelasticity‟) and even the temperature („Aerothermoelasticity‟). Within the Aeronautical Engineering, aeroelastic phenomena, either static (divergence, aileron reversal) or dynamic (flutter, buzz), are well known since the early beginning of the Aviation. Lessons learned along the History of the Aeronautics have provided several design criteria in order to mitigate the probability of encountering adverse aeroelastic phenomena along the operational life of an aircraft. Additionally, last decade improvements experienced by the Computational Aerodynamics and aeroelastic modelization have refined the flutter onset speed calculations during the design phase of an aircraft. However, still today, flight test remains as a key tool to validate aeroelastic models, to verify flutter-free conditions and to certify the different envelopes of an aircraft. Specifically, during the envelope expansion in altitude/speed, real time prediction of flutter conditions is required in order to avoid them in flight. In that sense, within the flight test community, several methodologies have been developed to predict in real time flutter conditions based on free-flutter flight conditions. Among them, the damping versus velocity technique combined with a Flutter Margin implementation remains as the most common technique used to proceed with the envelope expansion in altitude/airspeed. However, although its popularity and „easy to implement‟ characteristics, several shortcomings can adversely affect to the identification of unstable conditions when mechanical non-linearties, as freeplay, are present. Specially, during test flights devoted to envelope expansion in altitude/airspeed, Limits Cycle Oscillations (LCOs) conditions can not be accurately distinguished from those of flutter and, in consequence, it leads to an excessively conservative envelope determination. The present Thesis develops a new methodology, based on the Flutter Margin concept, that enables in real time the prediction of the „Limit Cycle‟ conditions, whenever they exist, without degrading the capability of predicting the flutter onset speed. The first part of this Thesis presents a review of the state of the art regarding the test methods available to proceed with the envelope expansion of an aircraft in altitude/airspeed and the effect of mechanical non-linearities on the aeroelastic behavior. Also, both civil and military regulations are reviewed with respect aeroelastic investigation of air vehicles. The second part of this Thesis proposes a new methodology to perform envelope expansion in real time based on the Flutter Margin concept when non-linearities, as freeplay, are present. Additionally, this methodology is validated against a Matlab/Slimulink bidimensional aeroelastic model. This model, parametric and interactive, is formulated within the state-space field and it implements the proposed methodology through two main real time modules: A signal processing module and a prediction module. The third part of this Thesis compares the final conclusions derived from the proposed methodology with those stated by the flight test community and experimental results. In summary, the main results provided by this Thesis are: 1. State of the Art review of the test methods applied to envelope expansion in altitude/airspeed and the influence of mechanical non-linearities in its identification. 2. Review of the main civil and military regulations regarding the aeroelastic verification of air vehicles and the limits set when non-linearities are present. 3. Development of a methodology for envelope expansion based on the Flutter Margin concept. 4. A Matlab/Simulink 2D-[aeroelastic model], parametric and interactive, used as a tool to validate the proposed methodology. 5. Conclusions driven from the present Thesis and comparison with experimental results.

Wind tunnel study on the influence of different parapets on the roof pressure distribution of low-rise buildings

High suction loads appear on roofs of low-height buildings. The use of parapets with appropriate height at the roof edges alleviates these loads. The performance of six parapet configurations to decrease the suction loads induced on roofs by oblique winds has been studied in a low speed wind tunnel. The studied parapet configurations include vertical wall parapets, either solid or porous, and cantilevered parapets formed by a small horizontal roof close to the building roof. Low-height parapets with a medium porosity and cantilevered parapets are more efficient than solid parapets to reduce the wind suctions generated on the roofs by conical vortices.

The influence of the section shape of box-girder decks on the steady aerodynamic yawing moment of double cantilever bridges under construction

The yawing moment acting on the box-girder deck of reinforced concrete bridges constructed using the balanced cantilever method during the erection stage has been experimentally analyzed by testing different types of bridge cross-sections. Experimental results show that the yawing moment coefficient decreases as the bridge decks become streamlined, and that the yawing moment coefficient reaches a maximum when the bridge deck length is nearly twice the deck width.

A parametric, experimental analysis of conical vortices on curved roofs of low-rise buildings

Different methods to reduce the high suction caused by conical vortices have been reported in the literature: vertical parapets, either solid or porous, placed at the roof edges being the most analysed configuration. Another method for alleviating the high suction peaks due to conical vortices is the use of some non-standard parapet configuration like cantilever parapets. In this paper the influence of roof curvature on the conical vortex pattern appearing on a curved roof (Fig. 1) when subject to oblique winds is experimentally analysed by testing the mean pressure distribution on the curved roofs of low-rise building models in a wind tunnel. Also, the efficiency of cantilever parapets to reduce mean suction loads on curved roofs is experimentally checked. Very high suction loads have been measured on curved roofs, the magnitude of these high suction loads being significantly decreased when cantilever parapets are used. Thus, the suitability of these parapets to reduce wind pressure loads on curved roofs is demonstrated.

Influence of an upstream building on the wind-induced mean suction on the flat roof of a low-rise building

The effect of an upstream building on the suction forces on the flat roof of a low-rise building placed in the wake of the former is analyzed. The analysis has been performed by wind tunnel testing of a flat roof, low-rise building model equipped with pressure taps on the roof and different block-type buildings (only configurations where the upstream building is as high or higher than the downstream one are considered in this paper). The influence of the distance between both buildings on the wind loads on the downstream building roof is analyzed, as well as the height of the upstream one and the wind angle of incidence. Experimental results reveal that the wind load increases as the relative height of the upstream building increases, the wind load being highest for intermediate distances between buildings, when a passage between them is formed.

Análisis de la influencia de imperfecciones en el borde de ataque en perfiles aerodinámicos a bajos números de Reynolds

En esta tesis se ha analizado la influencia que tienen ciertas imperfecciones en el borde de ataque de un perfil aerodinámico sobre el comportamiento aerodinámico general del mismo, centrándose fundamentalmente en la influencia sobre el coeficiente de sustentación máxima, coeficiente de resistencia y sobre la eficiencia aerodinámica del perfil, es decir sobre la relación entre la sustentación y la resistencia aerodinámicas. También se ha analizado su influencia en otros aspectos, como la entrada en pérdida, ángulo de ataque de sustentación máxima, ángulo de ataque de eficiencia máxima, coeficiente de momento aerodinámico y posición del centro aerodinámico. Estos defectos de forma en el borde de ataque pueden aparecer en algunos procesos de fabricación de determinados elementos aerodinámicos, como pueden ser las alas de pequeños aviones no tripulados o las palas de aeroturbina. Los perfiles se ha estudiado a bajos números de Reynolds debido a su uso reciente en una amplia gama de aplicaciones, desde vehículos aéreos no tripulados (UAV) hasta palas de aeroturbina de baja potencia, e incluso debido a su potencial utilización en aeronaves diseñadas para volar en atmósferas de baja densidad. El objeto de estudio de esta tesis no ha sido analizado en profundidad en la literatura científica, aunque sí que se ha estudiado por varios autores el comportamiento de perfiles a bajos números de Reynolds, con ciertas protuberancias sobre su superficie o también con formación de hielo en el borde de ataque. Para la realización de este estudio se han analizado perfiles de distinto tipo, perfiles simétricos y con curvatura, perfiles laminares, y todos ellos con igual o distinto espesor, con el objeto de obtener y comparar la influencia del fenómeno estudiado sobre cada tipo de perfil y así analizar su grado de sensibilidad a estas imperfecciones en la geometría del borde de ataque. Este trabajo ha sido realizado experimentalmente utilizando una túnel aerodinámico diseñado específicamente a tal efecto, así como una balanza electrónica para medir las fuerzas y los momentos sobre el perfil, y un escáner de presiones para medir la distribución de presiones sobre la superficie de los perfiles en determinados casos de interés. La finalidad de este estudio está orientada al establecimiento de criterios para cuantificar la influencia en la aerodinámica del perfil que tiene el hecho de que el borde de ataque presente una discontinuidad geométrica, con el objeto de poder establecer los límites de aceptación o rechazo de estas piezas en el momento de ser fabricadas. Del análisis de los casos estudiados se puede concluir que según aumenta el tamaño de la imperfección del borde de ataque, la sustentación aerodinámica máxima en general disminuye, al igual que la eficiencia aerodinámica máxima, pues la resistencia aerodinámica aumenta. Sin embargo, en algunos casos, para pequeños defectos se produce un efecto contrario. La sustentación máxima aumenta apreciablemente sin apenas pérdida de eficiencia aerodinámica máxima. 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.

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.

Diseño y construcción de una mini-turbina eólica

Dado que es difícil imaginar en el futuro una sociedad moderna donde la energía 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 carácter fósil, pues en muchos países es su principal o incluso su única forma de obtener energía, sino de avanzar hacia un equilibrio en la generación, para lo que será vital permitir el desarrollo de energías limpias, aumentar la eficiencia de la tecnología y reducir el consumo. En este contexto se ha decidido construir un rotor eólico de pequeñas dimensiones que servirá como herramienta de estudio para alumnos de ingeniería. Para diseñar la turbina se ha desarrollado un modelo de programación informática que, basado en conceptos aerodinámicos, permite calcular la geometría de las palas en función de unas condiciones iniciales, estimar la potencia del rotor y obtener sus curvas de funcionamiento. Uno de los principales problemas de la tecnología eólica es su alta variabilidad, por ello se ha implementado un sistema de regulación de velocidad; se trata de un mecanismo que actúa sobre la orientación de las palas y permite regular la potencia de un generador eléctrico acoplado al rotor. Los aerogeneradores actuales recurren a este tipo de sistemas para tratar de suavizar los desequilibrios de potencia que puedan producir las ráfagas de viento. Se ha recurrido a un software de diseño asistido por ordenador para dibujar tanto el rotor como el sistema de regulación de velocidad. La mayoría de las piezas del rotor se han fabricado con ayuda de una impresora 3D, otras, las metálicas, se han tallado en aluminio mediante un torno. Aunque el programa informático que realiza los cálculos aerodinámicos devuelve datos teóricos a cerca del comportamiento del rotor, se ha creído necesario probar el molino mediante ensayos de laboratorio a fin de obtener un resultado más 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.