A method to correct the flow distortion of offshore wind data using CFD simulation and experimental wind tunnel tests

The assessment of wind energy resource for the development of deep offshore wind plants requires the use of every possible source of data and, in many cases, includes data gathered at meteorological stations installed at islands, islets or even oil platforms—all structures that interfere with, and change, the flow characteristics. This work aims to contribute to the evaluation of such changes in the flow by developing a correction methodology and applying it to the case of Berlenga island, Portugal. The study is performed using computational fluid dynamic simulations (CFD) validated by wind tunnel tests. In order to simulate the incoming offshore flow with CFD models a wind profile, unknown a priori, was established using observations from two coastal wind stations and a power law wind profile was fitted to the existing data (a=0.165). The results show that the resulting horizontal wind speed at 80 m above sea level is 16% lower than the wind speed at 80 m above the island for the dominant wind direction sector.

Memòria justificativa de l'estada de recerca

Estudi elaborat a partir d’una estada a l’Associação para o Desenvolvimento da Aerodinânica Industrial (ADAI) de la Universitat de Coimbra, Portugal, entre març i juliol de 2006. Aquesta disposa d'un laboratori d'assaigs i té medis suficients per a cremar de manera controlada parcel•les prèviament delimitades en terreny forestal. Això permet observar el fenomen dels incendis forestals a dues escales de treball diferents. L’objectiu ha estat l’obtenció de dades experimentals sobre la propagació de fronts de flames que avancen sobre combustible tractat amb retardants sota l’efecte del pendent o el vent. S’ha participat en proves experimentals de camp i se n’han realitzat dues en instal•lacions de laboratori en què l’efecte del pendent o de la velocitat del vent podia ser variat. Degut a l’elevat nombre de variables que entren en joc l’anàlisi acurada de les dades encara està en procés.

Developing discontinuous Galerkin methods for the resolution of the incompressible Navier-Stokes equations

Informe de investigación elaborado a partir de una estancia en el Laboratorio de Diseño Computacional en Aeroespacial en el Massachusetts Institute of Technology (MIT), Estados Unidos, entre noviembre de 2006 y agosto de 2007. La aerodinámica es una rama de la dinámica de fluidos referida al estudio de los movimientos de los líquidos o gases, cuya meta principal es predecir las fuerzas aerodinámicas en un avión o cualquier tipo de vehículo, incluyendo los automóviles. Las ecuaciones de Navier-Stokes representan un estado dinámico del equilibrio de las fuerzas que actúan en cualquier región dada del fluido. Son uno de los sistemas de ecuaciones más útiles porque describen la física de una gran cantidad de fenómenos como corrientes del océano, flujos alrededor de una superficie de sustentación, etc. En el contexto de una tesis doctoral, se está estudiando un flujo viscoso e incompresible, solucionando las ecuaciones de Navier- Stokes incompresibles de una manera eficiente. Durante la estancia en el MIT, se ha utilizado un método de Galerkin discontinuo para solucionar las ecuaciones de Navier-Stokes incompresibles usando, o bien un parámetro de penalti para asegurar la continuidad de los flujos entre elementos, o bien un método de Galerkin discontinuo compacto. Ambos métodos han dado buenos resultados y varios ejemplos numéricos se han simulado para validar el buen comportamiento de los métodos desarrollados. También se han estudiado elementos particulares, los elementos de Raviart y Thomas, que se podrían utilizar en una formulación mixta para obtener un algoritmo eficiente para solucionar problemas numéricos complejos.

Estudi de l’eficiència aerodinàmica de vehicles pesants de transport de passatgers

Estudi de l’eficiència aerodinàmica de les carrosseries de vehicles pesants de cara a reduir el consum de combustible en autocars de llarg trajecte. L’estudi es basa en tres aspectes: validació del programa de simulació, estudi aerodinàmic de diferents carrosseries d’autocar de mercat i estudi aerodinàmic de diferents complements

Millora aerodinàmica de la nova carrosseria del vehicle l'Àliga. Estudis dels efectes de la rugositat i l'inserció d'apèndixs aerodinàmics

L' objectiu d' aquest estudi és intentar millorar l' aerodinàmica de la nova carrosseria del vehicle de baix consum de la UdG,l' Àliga, a través de programes informàtics de CFD.Des de fa uns anys l' Escola Politècnica Superior de la Universitat de Girona participa a l' Eco Shell Marathon, mirant d' assolir els millors resultats possibles.El nom del vehicle utilitzat per aquesta carrera és l' Àliga.Aquest projecte parteix dels resultats obtinguts al Projece fi de carrera d' en Daniel Vilavedra Vilà (2006):"Redisseny aerodinàmic de la carrosseria del vehicle de baix consum Àliga"

Estudi de l’eficiència aerodinàmica de vehicles pesants de transport de passatgers

Estudi de l’eficiència aerodinàmica de les carrosseries de vehicles pesants de cara a reduir el consum de combustible en autocars de llarg trajecte. L’estudi es basa en tres aspectes: validació del programa de simulació, estudi aerodinàmic de diferents carrosseries d’autocar de mercat i estudi aerodinàmic de diferents complements

Estudi de la influència del vent en l’estabilitat de vehicles pesants de transport de viatgers.

Investigacions recents revelen com l’acció del vent lateral és un efecte molt important en bona part dels accidents ocorreguts en vehicles pesants de transport per carretera. És per això que el perfil aerodinàmic del vehicle esdevé determinant en l’avaluació de les forces laterals que hi actuen.El present projecte té per objecte determinar les forces laterals que s’exerceixen en vehicles pesants de transport de passatgers degut a l’acció del vent i investigar-ne la seva perillositat. Per fer-ho s’utilitzen models numèrics de dinàmica de fluids i, per diferents velocitats del vehicle, es simulen vents amb diferent intensitat i direcció. D’aquí es determinen unes condicions de perillositat en funció, entre d’altres variables, de l’angle d’incidència del vent i de la seva velocitat

Estudi i simulació aerodinàmica amb programari de dinàmica de fluids computacional (CFD) en un model bàsic de vehicle de competició de la categoria CM (curses de muntanya)

Aquest projecte té com a objectiu la simulació numérica de la carrosseria d’ un vehicle de curses de muntanya de categoria CM

Ballistisen simuloinnin liikeidean kehittämismahdollisuudet

Asevaikutusta laukaisusta kohteeseen simuloiva integroitu laskentaketju koostuu sisä-, ulko- ja maaliballistiikan malleista. Ulkoballistiikka kattaa laskentamallit radanlaskennan, sääkorjauksen ja ammusaerodynamiikan alueilla. Graafisella käyttöliittymällä toteutetulla, fysikaalisesti tarkkaan mallinnukseen perustuvalla ja kokonaisuuden kattavalla laskentajärjestelmällä on kasvavaa tarvetta teknisiä ja koulutuksellisia tarkoituksia varten. Erikoisesti, jos laskentaketjuun lisätään räjähdysvaikutuksen mallintaminen, voidaan simuloida asejärjestelmien vaikutusta kohteessa käyttäjien arvostamalla tavalla. Tietointensiiviset ballistiikan laskentamallit ovat välttämättömiä työkaluja teknisen suunnitteluosaamisen kattamiseksi ja kilpailuedun luomiseksi verkostoituneessa yritysympäristössä. Yliopistotutkimuksen tuottamien laskennallisten menetelmien hyötykäyttö yritysten suunnittelujärjestelmissä syventää teknistä osaamista, jolla on myös henkilöstöä motivoiva vaikutus teknisesti vaikeutuvilla markkinoilla. Työssä arvioidaan toimialaa analysoimalla eri käyttötarpeita samoille tietokantoihin tukeutuville laskentamalleille. Tarkastellaan teknisiä perusteita, käyttöympäristöjä ja markkinoita liiketoimintamahdollisuuksien tunnistamiseksi. Työn tuloksena syvennetään näkemystä ydinosaamisista ja visioidaan liikeidean erottumista kilpailijoista, markkinoita ja sen kehittämistä.

Panel Method Formulation for Oscillating Airfoils in Sonic Flow

The mathematical model for two-dimensional unsteady sonic flow, based on the classical diffusion equation with imaginary coefficient, is presented and discussed. The main purpose is to develop a rigorous formulation in order to bring into light the correspondence between the sonic, supersonic and subsonic panel method theory. Source and doublet integrals are obtained and Laplace transformation demonstrates that, in fact, the source integral is the solution of the doublet integral equation. It is shown that the doublet-only formulation reduces to a Volterra integral equation of the first kind and a numerical method is proposed in order to solve it. To the authors' knowledge this is the first reported solution to the unsteady sonic thin airfoil problem through the use of doublet singularities. Comparisons with the source-only formulation are shown for the problem of a flat plate in combined harmonic heaving and pitching motion.

Hakeperävaunun aerodynamiikan parantaminen

Raskaankaluston ajoneuvojen aerodynaaminen kehitys on kulkenut väärään suuntaan jo vuosisadan verran ja niiden muodon määräävä tekijä on kuljetustilan maksimointi ja toi-minnallisuus. Lähiaikoina on astumassa EU:ssa uusi direktiivi voimaan, joka sallii lisämas-san käyttämisen aerodynaamisiin lisäosiin. Työn tarkoituksena on tutkia mahdollisuuksia parantaa hakeperävaunun aerodynamiikkaa yksinkertaisilla lisäosilla. Työ on rajattu koskemaan perävaununetuosaan, -sivuosaan ja -pohjaan. Lisäksi rajoitteita asettaa Suomenlainsäädäntö ja EU:n direktiivit. Työssä perehdytään ilmanvastusvoiman syntymekanismeihin raskaankaluston ajoneuvojen kannalta ja käydään läpi merkittävimmät vaikuttavat tekijät ilmanvastusvoimiin sekä kuorma-auton perävaunun eri muotojen ja osien vaikutus. Perävaunuun asetettavien il-manohjaimien vaikutukset ja toiminta selvitetään. Avainasemassa hakeperävaunun aerodynamiikan parantamisessa on ilmavirtauksen estä-minen perävaunun alle sekä etupuolelta. Lisäksi virtausten muuttamien perävaunun takana on hyödyllistä. Merkittävimmät hyödyt saadaan niistä ratkaisuista, jotka estävät ilman virtausta perävau-nun alle sekä renkaisiin. Näitä ratkaisuja olivat sivuhelmat ja pohjan sekä renkaiden kote-lointi. Lisäksi ilmavirtauksen estäminen perävaunun edestä tuotti merkittävää hyötyä. Levy perävaunun välissä tai koko välin peittämällä saadaan aikaan huomattavaa vähenemistä ilmanvastuksessa.

Pressure dependence of spin fluctuations in metallic glasses Zrâ â Niâ â ,Zrâ â (Nix/Feâ â â -x)â â and /Zrx/feâ â â -x

The superconducting transition temperature Tc of metallic glasses ZrxFelOO-x (x=80, 75), Zr75(NixFelOO-x)25 (x=75, 50, 25), and CU2SZr75 were measured under quasi-hydrostatic pressure up to 8 OPa (80kbar). The volume (pressure) dependence of the electron-phonon coupling parameters Aep for CU25Zr75 was calculated using the McMillan equatio11. Using this volume dependence of Aep and the modified McMillan equation which incorporates spin-fluctuations, the volume dependence of the spin fluctuation parameter, Asf, was determined in Zr75Ni25, ZrxFelOO-x , a11d Zr75(NixFelOO-x)25. It was found that with increasing pressure, spinfluctuations are suppressed at a faster rate in ZrxFe lOO-x and Zr75(NixFelOO-x)25, as Fe concentration is increased. The rate of suppression of spin-fluctuations with pressure was also found to be higher in Fe-Zr glasses than in Ni-Zr glasses of similar composition.

The finite bandwidth model for spin fluctuations in Pd

The frequency dependence of the electron-spin fluctuation spectrum, P(Q), is calculated in the finite bandwidth model. We find that for Pd, which has a nearly full d-band, the magnitude, the range, and the peak frequency of P(Q) are greatly reduced from those in the standard spin fluctuation theory. The electron self-energy due to spin fluctuations is calculated within the finite bandwidth model. Vertex corrections are examined, and we find that Migdal's theorem is valid for spin fluctuations in the nearly full band. The conductance of a normal metal-insulator-normal metal tunnel junction is examined when spin fluctuations are present in one electrode. We find that for the nearly full band, the momentum independent self-energy due to spin fluctuations enters the expression for the tunneling conductance with approximately the same weight as the self-energy due to phonons. The effect of spin fluctuations on the tunneling conductance is slight within the finite bandwidth model for Pd. The effect of spin fluctuations on the tunneling conductance of a metal with a less full d-band than Pd may be more pronounced. However, in this case the tunneling conductance is not simply proportional to the self-energy.

An analysis of the methyl rotation dynamics in the So (x' A) and T (a A) states of thioacetaldehyde from Pyrolysis jet spectra /

Jet-cooled, laser-induced phosphorescence excitation spectra (LIP) of thioacetaldehyde CH3CHS, CH3CDS, CD3CHS and CD3CDS have been observed over the region 15800 - 17300 cm"^ in a continuous pyrolysis jet. The vibronic band structure of the singlet-triplet n -* n* transition were attributed to the strong coupling of the methyl torsion and aldehydic hydrogen wagging modes . The vibronic peaks have been assigned in terms of two upper electronic state (T^) vibrations; the methyl torsion mode v^g, and the aldehydic hydrogen wagging mode v^^. The electronic origin O^a^ is unequivocally assigned as follows: CH3CHS (16294.9 cm"'' ), CH3CDS (16360.9 cm"'' ), CD3CHS (16299.7 cm"^ ), and CD3CDS (16367.2 cm"'' ). To obtain structural and dynamical information about the two electronic states, potential surfaces V(e,a) for the 6 (methyl torsion) and a (hydrogen wagging) motions were generated by ab initio quantum mechanical calculations with a 6-3 IG* basis in which the structural parameters were fully relaxed. The kinetic energy coefficients BQ(a,e) , B^(a,G) , and the cross coupling term B^(a,e) , were accurately represented as functions of the two active coordinates, a and 9. The calculations reveal that the molecule adopts an eclipsed conformation for the lower Sq electronic state (a=0°,e=0"') with a barrier height to internal rotation of 541.5 cm"^ which is to be compared to 549.8 cm"^ obtained from the microwave experiment. The conformation of the upper T^ electronic state was found to be staggered (a=24 . 68° ,e=-45. 66° ) . The saddle point in the path traced out by the aldehyde wagging motion was calculated to be 175 cm"^ above the equilibrium configuration. The corresponding maxima in the path taken by methyl torsion was found to be 322 cm'\ The small amplitude normal vibrational modes were also calculated to aid in the assignment of the spectra. Torsional-wagging energy manifolds for the two states were derived from the Hamiltonian H(a,e) which was solved variationally using an extended two dimensional Fourier expansion as a basis set. A torsionalinversion band spectrum was derived from the calculated energy levels and Franck-Condon factors, and was compared with the experimental supersonic-jet spectra. Most of the anomalies which were associated with the interpretation of the observed spectrum could be accounted for by the band profiles derived from ab initio SCF calculations. A model describing the jet spectra was derived by scaling the ab initio potential functions. The global least squares fitting generates a triplet state potential which has a minimum at (a=22.38° ,e=-41.08°) . The flatter potential in the scaled model yielded excellent agreement between the observed and calculated frequency intervals.

Techniques for Enhancing Wind Energy Generation - A CFD Based Multibody Dynamics Approach in Horizontal Axis Wind Turbines

Wind energy has emerged as a major sustainable source of energy.The efficiency of wind power generation by wind mills has improved a lot during the last three decades.There is still further scope for maximising the conversion of wind energy into mechanical energy.In this context,the wind turbine rotor dynamics has great significance.The present work aims at a comprehensive study of the Horizontal Axis Wind Turbine (HAWT) aerodynamics by numerically solving the fluid dynamic equations with the help of a finite-volume Navier-Stokes CFD solver.As a more general goal,the study aims at providing the capabilities of modern numerical techniques for the complex fluid dynamic problems of HAWT.The main purpose is hence to maximize the physics of power extraction by wind turbines.This research demonstrates the potential of an incompressible Navier-Stokes CFD method for the aerodynamic power performance analysis of horizontal axis wind turbine.The National Renewable Energy Laboratory USA-NREL (Technical Report NREL/Cp-500-28589) had carried out an experimental work aimed at the real time performance prediction of horizontal axis wind turbine.In addition to a comparison between the results reported by NREL made and CFD simulations,comparisons are made for the local flow angle at several stations ahead of the wind turbine blades.The comparison has shown that fairly good predictions can be made for pressure distribution and torque.Subsequently, the wind-field effects on the blade aerodynamics,as well as the blade/tower interaction,were investigated.The selected case corresponded to a 12.5 m/s up-wind HAWT at zero degree of yaw angle and a rotational speed of 25 rpm.The results obtained suggest that the present can cope well with the flows encountered around wind turbines.The areodynamic performance of the turbine and the flow details near and off the turbine blades and tower can be analysed using theses results.The aerodynamic performance of airfoils differs from one another.The performance mainly depends on co-efficient of performnace,co-efficient of lift,co-efficient of drag, velocity of fluid and angle of attack.This study shows that the velocity is not constant for all angles of attack of different airfoils.The performance parameters are calculated analytically and are compared with the standardized performance tests.For different angles of ,the velocity stall is determined for the better performance of a system with respect to velocity.The research addresses the effect of surface roughness factor on the blade surface at various sections.The numerical results were found to be in agreement with the experimental data.A relative advantage of the theoretical aerofoil design method is that it allows many different concepts to be explored economically.Such efforts are generally impractical in wind tunnels because of time and money constraints.Thus, the need for a theoretical aerofoil design method is threefold:first for the design of aerofoil that fall outside the range of applicability of existing calalogs:second,for the design of aerofoil that more exactly match the requirements of the intended application:and third,for the economic exploration of many aerofoil concepts.From the results obtained for the different aerofoils,the velocity is not constant for all angles of attack.The results obtained for the aerofoil mainly depend on angle of attack and velocity.The vortex generator technique was meticulously studies with the formulation of the specification for the right angle shaped vortex generators-VG.The results were validated in accordance with the primary analysis phase.The results were found to be in good agreement with the power curve.The introduction of correct size VGs at appropriate locations over the blades of the selected HAWT was found to increase the power generation by about 4%