*4.2. Numerical Polars*

The calibrated CFD model was then used to assess the influence of the Reynolds number in case of a high turbulence flow. The tested *Re* values were selected in order to cover the operating conditions of the study case VAWT for all of the analyzed TSRs. Figures 10 and 11 report the lift and drag polars for both positive and negative incidence angles starting from the lowest simulated Reynolds number (i.e., 40 k) up to the highest value of 160 k, with a step of 20 k. The lift increase, delay in stall angle and drag reduction is clearly visible from the CFD results, due to the higher resistance to flow separation as the Reynolds number is increased. Such behavior can be noticed by analyzing the flow field around the blade at 15◦ angle of attack for different Reynolds values, as shown in Figure 12: as the freestream velocity increases, the high vorticity region on the suction side due to separation is reduced and the flow tends to be more attached to the blade.

**Figure 10.** Lift polars for different Reynolds values with a high turbulence flow.

**Figure 11.** Drag polars for different Reynolds values with a high turbulence flow.

**Figure 12.** Vorticity contours and velocity streamlines around the blade at 15◦ incidence for different Reynolds.
