Publicação
CFD analysis of the air flow through horizontal axis wind turbines
| Resumo: | The main purpose of this thesis was the development of a procedure which allowed to perform numerical simulations of atmospheric flows over a flat terrain and through a wind turbine. The modelling and simulation work was carried out with the use of the Computational Fluid Dynamics (CFD) software ANSYS Fluent. For the CFD procedure, the 3D Reynolds Averaged Navier-Stokes Equations using the - turbulence model was employed, considering some modifications in the model constants to account for an atmospheric flow. Regarding the modelling practice of the neutral atmospheric boundary layer, custom equations were used for representing the logarithmic velocity profile, the turbulent kinetic energy and turbulent dissipation rate. Some practices were also dedicated to the establishment of accurate boundary conditions of the computational domain as well as the selection of the wall function representing the ground. The rotor of the wind turbine was modelled with the use of a porous jump boundary condition, in which the rotor is considered an actuator disc with an infinite number of blades. In this work, four different major simulations were performed. In the first one, a CFD procedure was created which allowed to recreate an atmospheric flow in a flat terrain with a high-level accuracy, with only a 1.5% error in velocity discrepancies. For the second simulation, a CFD technique was developed to model the flow of the wind through an actuator disc. This model was validated with the Jensen and the Larsen mathematical wake models, and it displayed a capability of accurately modelling the far-wake of the turbine, with an error of roughly 5%. The third and fourth simulations include the analyses of the wake effects between two wind turbines. In the third, the rotors are distanced 6D in the prevailing wind direction and it shows a 10% decrease in the wind velocity and a 28% decrease in the power output of the downstream turbine. In the fourth, the rotors are distanced just as in the third simulation but also 4D in the perpendicular direction. Consequently, the wake effects of the upstream turbine did not directly affect the downstream turbine. |
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| Autores principais: | Silva, Diogo Miguel Costa da |
| Assunto: | ANSYS fluent Atmospheric wind flow CFD Wind energy Horizontal axis wind turbines Energia eólica Escoamento de vento atmosférico Turbinas eólicas de eixo horizontal Engenharia e Tecnologia::Engenharia Mecânica |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The main purpose of this thesis was the development of a procedure which allowed to perform numerical simulations of atmospheric flows over a flat terrain and through a wind turbine. The modelling and simulation work was carried out with the use of the Computational Fluid Dynamics (CFD) software ANSYS Fluent. For the CFD procedure, the 3D Reynolds Averaged Navier-Stokes Equations using the - turbulence model was employed, considering some modifications in the model constants to account for an atmospheric flow. Regarding the modelling practice of the neutral atmospheric boundary layer, custom equations were used for representing the logarithmic velocity profile, the turbulent kinetic energy and turbulent dissipation rate. Some practices were also dedicated to the establishment of accurate boundary conditions of the computational domain as well as the selection of the wall function representing the ground. The rotor of the wind turbine was modelled with the use of a porous jump boundary condition, in which the rotor is considered an actuator disc with an infinite number of blades. In this work, four different major simulations were performed. In the first one, a CFD procedure was created which allowed to recreate an atmospheric flow in a flat terrain with a high-level accuracy, with only a 1.5% error in velocity discrepancies. For the second simulation, a CFD technique was developed to model the flow of the wind through an actuator disc. This model was validated with the Jensen and the Larsen mathematical wake models, and it displayed a capability of accurately modelling the far-wake of the turbine, with an error of roughly 5%. The third and fourth simulations include the analyses of the wake effects between two wind turbines. In the third, the rotors are distanced 6D in the prevailing wind direction and it shows a 10% decrease in the wind velocity and a 28% decrease in the power output of the downstream turbine. In the fourth, the rotors are distanced just as in the third simulation but also 4D in the perpendicular direction. Consequently, the wake effects of the upstream turbine did not directly affect the downstream turbine. |
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