No description available.

This project examined the effect of Gurney flaps on a 2D, 2-ft chord NACA 0036 airfoil in the Cal Poly 3’x4’ low speed wind tunnel at 25 m/s. It also covered the numerical simulation of the experiment in computational fluid dynamics (CFD). During the study, problems with the wind tunnel data were seen. After a careful diagnosis, the problem was traced to dirty flow conditioners which were subsequently replaced. Five Gurney flaps at 1, 2, 3, 4, and 5% of the chord were tested. The Gurney flaps had the effect of eliminating the lift reversal effect and lowering the profile drag at low angles of attack, ranging from 4-27%. The optimal Gurney flap appeared to be 2% of the chord. CFD modeling of the problem had limited success, with the best results coming from Mentor’s k-w SST turbulence model. This model reproduced the non-linear lift curve, and captured the trend in rising drag fairly well, but failed to predict the correct point of separation. Attempts to model the Gurney flap in CFD were unsuccessful.

A geração de energia elétrica por meio de aerogeradores de microporte vem ganhando espaço em várias partes do mundo; porém, estudos que descrevem e analisam este artefato, ainda são restritos se comparados a aerogeradores de médio e grande porte. Países como China e Estados Unidos, por exemplo, buscam cada vez mais estudar a microgeração de energia eólica, servindo como motivação para que exista maior número de estudos neste campo, também aqui no país. Neste sentido, a presente pesquisa apresenta análise de perfis NACA com diferentes ângulos de passo visando a microgeração de energia eólica. Para tanto realizou-se levantamento das velocidades de vento na parte superior de um prédio localizado no centro de Porto Alegre durante 5 dias e os perfis aerodinâmicos foram testados no programa computacional Q-Blade. Selecionou-se 3 perfis NACA (0012, 6409, 1412), 3 ângulos de passo (15º, 30° e 45º) e 5 velocidades de vento (de 1m/s à 5 m/s). Os modelos analisados foram obtidos através de impressão 3D. Foram então realizados ensaios aerodinâmicos utilizando o túnel de vento nos quais foram medidos o número de rotação por minuto (RPM), a velocidade de vento da partida da hélice, a tensão, corrente e a potência elétrica, geradas para diferentes configurações de ensaio. O trabalho contribui no sentido de auxiliar projetos que envolvam design e tecnologia que visem à melhoria da funcionalidade prática de microgeradores eólicos de eixo horizontal para as diversas aplicações possíveis. Os resultados apontam que o ângulo de passo de 45º apresenta os maiores índices de rotação, tensão, corrente e potência elétrica para todos os perfis NACA analisados, sendo o perfil NACA 0012 o de maior destaque em relação a esses mesmos parâmetros. / Electric power generation by small scale wind turbines has been gaining space in several parts of the world, however, studies that describe and analyze this artefact, are still more restrict in comparison to medium and large scale wind turbines. Countries such as China and the United States, for example, are increasingly seek to study wind power microgeneration, working as a motivator in order to increase the number of studies in the field, even here in the country. In this matter, the present research presents an analysis of NACA profiles with different pitch angles seeking wind energy microgeneration. In order to do so, it was gathered the wind speed of the top portion of a building located in central Porto Alegre during 5 days and the aerodynamic profiles were tested in the computer program Q-Blade. 3 NACA profiles (0012, 6409, 1412), 3 pitch angles (15º, 30° e 45º) and 5 wind velocities (1m/s to 5 m/s) were selected. The analyzed models were obtained through 3D printing. Aerodynamical tests were performed using the Wind tunnel and were observed the number of rotation per minute (RPM), the wind speed start of the propeller, electric tension, current and power generated for different test configurations. The work contributes to assisting projects that involves design and technology aimed at improving the practical functionality of horizontal axis wind generators for the various possible applications. The results indicate that the 45º pitch angle presents the highest rates of rotation, electric tension, current and power for all the NACA profiles analyzed, with the NACA 0012 profile being the most prominent in relation to these same parameters.

Limit Cycle Oscillation is a type of aircraft wing structural vibration caused by the non-linearity of the system. The objective of this thesis is to provide a numerical study of this aeroelastic behavior. A CFD solver is used to simulate airfoils displaying such an aeroelastic behavior under certain airflow conditions. Two types of airfoils are used for this numerical study, including the NACA64a010 airfoil, and the supercritical NLR 7301 airfoil. The CFD simulation of limit cycle oscillation (LCO) can be obtained by using published flow and structural parameters. Final results from the CFD solver capture LCO, as well as flutter, behaviors for both wings. These CFD results can be obtained by using two different solution schemes, including the Roe and Zha scheme. The pressure coefficient and skin friction coefficient distributions are computed using the CFD results for LCO and flutter simulations of these two airfoils, and they provide a physical understanding of these aeroelastic behaviors.

Improved basic understanding, predictability, and controllability of vortex-dominated and unsteady aerodynamic flows are important in enhancement of the performance of next generation helicopters. The primary objective of this research project was improved understanding of the fundamental vorticity and turbulent flow physics for a dynamically stalling airfoil at realistic helicopter flight conditions. An experimental program was performed on a large-scale (C = 0.45 m) dynamically pitching NACA 0012 wing operating in the Texas A&M University large-scale wind tunnel. High-resolution particle image velocimetry data were acquired on the first 10-15% of the wing. Six test cases were examined including the unsteady (k>0) and steady (k=0) conditions. The relevant mechanical, shear and turbulent time-scales were all of comparable magnitude, which indicated that the flow was in a state of mechanical non-equilibrium, and the expected flow separation and reattachment hystersis was observed. Analyses of the databases provided new insights into the leading-edge Reynolds stress structure and the turbulent transport processes. Both of which were previously uncharacterized. During the upstroke motion of the wing, a bubble structure formed in the leading-edge Reynolds shear stress. The size of the bubble increased with increasing angle-of-attack before being diffused into a shear layer at full separation. The turbulent transport analyses indicated that the axial stress production was positive, where the transverse production was negative. This implied that axial turbulent stresses were being produced from the axial component of the mean flow. A significant portion of the energy was transferred to the transverse stress through the pressure-strain redistribution, and then back to the transverse mean flow through the negative transverse production. An opposite trend was observed further downstream of this region.

Improved basic understanding, predictability, and controllability of vortex-dominated and unsteady aerodynamic flows are important in enhancement of the performance of next generation helicopters. The primary objective of this research project was improved understanding of the fundamental vorticity and turbulent flow physics for a dynamically stalling airfoil at realistic helicopter flight conditions. An experimental program was performed on a large-scale (C = 0.45 m) dynamically pitching NACA 0012 wing operating in the Texas A&M University large-scale wind tunnel. High-resolution particle image velocimetry data were acquired on the first 10-15% of the wing. Six test cases were examined including the unsteady (k>0) and steady (k=0) conditions. The relevant mechanical, shear and turbulent time-scales were all of comparable magnitude, which indicated that the flow was in a state of mechanical non-equilibrium, and the expected flow separation and reattachment hystersis was observed. Analyses of the databases provided new insights into the leading-edge Reynolds stress structure and the turbulent transport processes. Both of which were previously uncharacterized. During the upstroke motion of the wing, a bubble structure formed in the leading-edge Reynolds shear stress. The size of the bubble increased with increasing angle-of-attack before being diffused into a shear layer at full separation. The turbulent transport analyses indicated that the axial stress production was positive, where the transverse production was negative. This implied that axial turbulent stresses were being produced from the axial component of the mean flow. A significant portion of the energy was transferred to the transverse stress through the pressure-strain redistribution, and then back to the transverse mean flow through the negative transverse production. An opposite trend was observed further downstream of this region.

No description available.

Recent interest in Micro Aerial Vehicles (MAVs) and Unmanned Aerial Vehicles (UAVs) have revived research on the performance of airfoils at relatively low Reynolds numbers. A common problem with low Reynolds number flow is that separation is almost inevitable without the application of some means of flow control, but understanding the nature of the separated flow is critical to designing an optimal flow control system. The current research presents results from a joint effort coupling numerical simulation and wind tunnel testing to investigate this flow regime. The primary airfoil for these studies is a modified 4415 with an adaptive actuator mounted internally such that the camber of the airfoil may be changed in a static or oscillatory fashion. A series of simulations are performed in static mode for Reynolds numbers of 25,000 to 100,000 and over a range of angles of attack to predict the characteristics of the flow separation and the coefficients of lift, drag, and moment. Preliminary simulations were performed for dynamic mode and it demonstrates a definitive ability to control separation across the range of Re and AoA. The earlier experimental work showed that separation reduction is gradual until a critical oscillation frequency is reached, after which increases in frequency have little additional impact on the flow. Present numerical simulation results were compared with the previous experiments results which were performed on the airfoil in like flow conditions and these comparisons allow the accuracy of both systems to be determined.

This research is focused on formulating a new model of entropy production for two-phase flow, including cavitating turbulent flow. In particular, it focuses on the following aspects of the fluid dynamics and the potential contribution of the model to fluid device design. It includes (i) developing a new turbulent entropy model, (ii) a new formula of entropy production rate for two-phase flow including cavitating turbulent flow based on the second law, (iii) applying the technique to study a NACA hydrofoil, and (iv) conducting associated performance analysis of a propeller using post-processing of the CFD results and demonstrating that entropy production of two-phase cavitating flow around the propeller can be correlated to the loss of power output. The first stage consists of formulating the entropy production for laminar channel flow using Gibb’s free energy. This model is validated through the analytically solved Navier-Stokes equations. Subsequently, the single-phase turbulent flow is formulated in a similar manner, but the validations are carried out by comparing the prediction of the model with DNS results. Then, the model of entropy production for two-phase turbulent flow is derived from Gibb’s equation and a version of the Reynolds averaged Navier-Stokes (RANS) equations. The k- ε model is employed to represent the turbulent properties of single phase and two phase flows. A developed inter-phase slip algorithm mixture model is applied to control over coupling of phases. The Rayleigh-Plesset equation is used to model the rate of mass generation of vapour at the inter phase. The standard k-ε turbulence equations are used to describe turbulence in the cavitation flow. The validations of CFD predictions include exploring the force and cavitation characteristics of the NACA 4412 hydrofoil section. The application of this entropy production model in engineering design is presented via the comparisons between CFD results and the experimental data for the velocity distributions behind propeller P5168.

A geração de energia elétrica por meio de aerogeradores de microporte vem ganhando espaço em várias partes do mundo; porém, estudos que descrevem e analisam este artefato, ainda são restritos se comparados a aerogeradores de médio e grande porte. Países como China e Estados Unidos, por exemplo, buscam cada vez mais estudar a microgeração de energia eólica, servindo como motivação para que exista maior número de estudos neste campo, também aqui no país. Neste sentido, a presente pesquisa apresenta análise de perfis NACA com diferentes ângulos de passo visando a microgeração de energia eólica. Para tanto realizou-se levantamento das velocidades de vento na parte superior de um prédio localizado no centro de Porto Alegre durante 5 dias e os perfis aerodinâmicos foram testados no programa computacional Q-Blade. Selecionou-se 3 perfis NACA (0012, 6409, 1412), 3 ângulos de passo (15º, 30° e 45º) e 5 velocidades de vento (de 1m/s à 5 m/s). Os modelos analisados foram obtidos através de impressão 3D. Foram então realizados ensaios aerodinâmicos utilizando o túnel de vento nos quais foram medidos o número de rotação por minuto (RPM), a velocidade de vento da partida da hélice, a tensão, corrente e a potência elétrica, geradas para diferentes configurações de ensaio. O trabalho contribui no sentido de auxiliar projetos que envolvam design e tecnologia que visem à melhoria da funcionalidade prática de microgeradores eólicos de eixo horizontal para as diversas aplicações possíveis. Os resultados apontam que o ângulo de passo de 45º apresenta os maiores índices de rotação, tensão, corrente e potência elétrica para todos os perfis NACA analisados, sendo o perfil NACA 0012 o de maior destaque em relação a esses mesmos parâmetros. / Electric power generation by small scale wind turbines has been gaining space in several parts of the world, however, studies that describe and analyze this artefact, are still more restrict in comparison to medium and large scale wind turbines. Countries such as China and the United States, for example, are increasingly seek to study wind power microgeneration, working as a motivator in order to increase the number of studies in the field, even here in the country. In this matter, the present research presents an analysis of NACA profiles with different pitch angles seeking wind energy microgeneration. In order to do so, it was gathered the wind speed of the top portion of a building located in central Porto Alegre during 5 days and the aerodynamic profiles were tested in the computer program Q-Blade. 3 NACA profiles (0012, 6409, 1412), 3 pitch angles (15º, 30° e 45º) and 5 wind velocities (1m/s to 5 m/s) were selected. The analyzed models were obtained through 3D printing. Aerodynamical tests were performed using the Wind tunnel and were observed the number of rotation per minute (RPM), the wind speed start of the propeller, electric tension, current and power generated for different test configurations. The work contributes to assisting projects that involves design and technology aimed at improving the practical functionality of horizontal axis wind generators for the various possible applications. The results indicate that the 45º pitch angle presents the highest rates of rotation, electric tension, current and power for all the NACA profiles analyzed, with the NACA 0012 profile being the most prominent in relation to these same parameters.