Stability and Sensitivity Analysis of Darrieus Wind Turbine CFD Simulations at Low Tip Speeds

Authors: Md Mahmud Hasan Saikot, Mahbub Siam, and Mahfuzur Rahman

Abstract

Computational Fluid Dynamics (CFD) is an essential tool for studying Darrieus wind turbines and helping them reach a mature industrial standard. The most exploited design choice for the Darrieus turbines is the H-shape configuration which has a great performance in high tip speed ratios (TSR). However, in low TSRs, it performs poorly due to the large angle of attack variation and flow separation. The simulation results also become unstable, leading to inaccurate and often misleading results. This study exploited high-fidelity unsteady 2D simulations to analyze a three-bladed H-Darrieus wind turbine in low TSRs and predict a stable simulation model. A new parameter, S0, was coined to help quantify the stability of the simulations. The quantified simulation stability was monitored against courant numbers to determine the criteria for stable simulation. We found that the Standard SST model is more stable at low TSR than the curvature-corrected SST model, and the standard model is also less mesh-sensitive. It was also found that mesh and timestep sensitivity must be done in both high and low TSRs to obtain accurate results in a wide TSR range.

Original research article to appear in ICMIME 2022

Fig: Comparison Between Simulations done with two different Turbulence Models.