-Efficiency of the vertical axis wind turbine depends on turbine design. Wind tunnel experiments, usually performed for evaluation of turbine design, are expensive in comparison with CFD simulations. Although purely numeric, CFD models critically depend on a large set of parameters, which varies from mesh size to numerical schemes and models of turbulence. The aim of the presented research is to evaluate the critical ranges of these parameters for a practically applicable turbine design.Keywords -convergence of the model, mesh size, models of turbulence, numerical approximation schemes