CFD analysis of tilted vertical axis wind turbine for offshore application

Abstract

Horizontal Axis Wind Turbine (HAWT) is currently dominating the onshore wind energy market. HAWT has remained a popular choice to the engineers due to its higher aerodynamic efficiency than other wind turbine configurations. Now the policy makers are thinking to harness wind energy from offshore. The technology of extracting offshore wind energy is still in a preliminary level. In the recent years some popular and economical concepts like Floating Axis Wind Turbine (FAWT) has been developed. Maintaining an upright position on floating axis base would not be economically feasible. As HAWT is known to respond negatively in yawed flow or tilted flow condition, it could not be a reliable choice for offshore application. That is why some scientists are considering Vertical Axis Wind Turbine (VAWT). The primary goal of this thesis to numerically validate an existing experimental work of VAWT in upright and tilted conditions by comparing power co-efficient. The numerical validation is carried out by means of Computational Fluid Dynamics (CFD) and a comparative analysis of VAWT in upright and tilted condition is drawn. CFD analysis of VAWT requires solving Unsteady Reynolds Averaged Navier-Stokes (URANS) equation. Upon reviewing the existing literatures regarding VAWT, it has been found that, there has not been any study regarding the choice of parameters for solving URANS equation like turbulence model, mesh dependency and time step in three dimension. Although, there are some works in two dimension, the three dimensional affect like tip vortices will be dominant in case of low aspect ratio turbine and hence could not be ignored. As this thesis is dealing with a low aspect ratio turbine and three dimensional CFD analysis of VAWT is computationally expensive, choosing the right parameters at the beginning of the research is very important. Therefore a thorough and rigorous parametric study is comprehended. After choosing the right parameters, validation is done. Follo...