# Case II The torque ripples at all

As indicated earlier that Case I over predicted the torque values. To quantify the decrease in the performance, we compute the relative difference and term it RS 127445 “geometric” error due to structural approximations. In physical sense, it is the over prediction of two-dimensional simulations lacking third dimensional flow. Fig. 13 plots the percentage drop in the performance for the Cases relative to Case I. We find that a percentage drop in performance of 18% is expected from simple 2D (Case I) to simple 3D (Case II) simulations. By addition of tip effects from the blades (Case III) an additional 3% drop is observed. Further incorporating the three dimensional support structures (Case IV) the overall drop jumps to 26% relative to the 2D analysis. With the addition of tip effects in the support structure (Case V) the drop reaches to 32%. Usually researchers exclude the support structure (support arms and central hub) to focus on VAWT blades only, thus endocrine system should expect approximated error of 10%–12%. Practically, the results of Case V are expected to be in close agreement with the real-time results as they have the highest level of complexity with lower approximations.