Viscous Flow and Dynamic Stall Effects on Vertical‐Axis Wind Turbines

Abstract

The present paper describes a numerical method, aimed to simulate the flow field of vertical-axis wind turbines, based on the solution of the steady, incompressible, laminar Navier-Stokes equations in cylindrical coordinates. The flow equations, written in conservation law form, are discretized using a control volume approach on a staggered grid. The effect of the spinning blades is simulated by distributing a time-averaged source terms in the ring of control volumes that lie in the path of turbine blades. The numerical procedure used here, based on the control volume approach, is the widely known “SIMPLER” algorithm. The resulting algebraic equations are solved by the TriDiagonal Matrix Algorithm (TDMA) in the r- and z-directions and the Cyclic TDMA in the 0-direction. The indicial model is used to simulate the effect of dynamic stall at low tip-speed ratio values. The viscous model, developed here, is used to predict aerodynamic loads and performance for the Sandia 17-m wind turbine. Predictions of the viscous model are compared with both experimental data and results from the CARDAAV aerodynamic code based on the Double-Multiple Streamtube Model. According to the experimental results, the analysis of local and global performance predictions by the 3D viscous model including dynamic stall effects shows a good improvement with respect to previous 2D models.

Model improvements for evaluating the effect of tower tilting on the aerodynamics of a vertical axis wind turbine

“…A selection of results is presented, including the global performance, and the local aerodynamic coefficients obtained by the DMS model both without the dynamic stall model and with three different dynamic stall models. The calculated results for the Sandia 17 m wind turbine are compared with the experimental data from the prototype of the wind turbine . The thrust force for the DeepWind 5 MW wind turbine design is compared with computations from Risø DTU…”

“…The calculated results for the Sandia 17 m wind turbine are compared with the experimental data from the prototype of the wind turbine. 42,43 The thrust force for the DeepWind 5 MW wind turbine design is compared with computations from Risø DTU. 44…”

Dynamic stall in vertical axis wind turbines: Comparing experiments and computations

“…Although dynamic stall is a dominating feature of vertical axis wind turbine flows, it has been studied extensively in many other contexts (McCroskey, 1976;Leishman and Beddoes, 1986;Carr, 1988;Geissler and Haselmeyer, 2006;Buchner et al, 2012;. On horizontal axis wind turbines, for example, even mild stall decreases performance and increases noise production significantly (Hibbs, 1986;Loratro et al, 2014), and similar effects are experienced to a greater magnitude by vertical axis turbines (Allet and Paraschivoiu, 1995;Scheurich and Brown, 2011).…”

3D URANS analysis of a vertical axis wind turbine in skewed flows

“…The 2D CFD model over-predicts power at high wind speeds, as would be expected from the previous analysis. Figure 3 also compares the data with those predicted using BEM (Blade Element-Momentum) approaches by Allet [19] as well as another CFD approach [20]. The advantage of the CFD approach becomes clearer at high wind-speed conditions, where greater accuracy in predicted power is achieved.…”