Computational fluid dynamics (CFDs) simulation tools are developed to analyse the aerodynamic performance of a novel design vertical axis wind turbine (VAWT) and compared against careful data from a 1.6 m diameter device in a wind tunnel. The study investigates the extent to which a CFD model employing the simplest turbulence representation can provide a useful input to evaluate the impact of several key operational parameters: wind speed, rotor speed, yaw angle and blade pitch angle. The results show that simple turbulence modelling techniques are sufficient to evaluate the performance of the turbine in the designed operating conditions and can predict when the turbine will run outside each parameter's operational range. However, such a simple turbulence representation may need further refinement to quantify more precisely the extent to which performance is affected when running some way outside this range. (C) 2013 Elsevier Ltd. All rights reserved.