Large eddy simulation of turbulent flow past a parabolic dish

Thin parabolic geometries are used in solar power generators and antennas, wherein the aerodynamic load on the structure is an important parameter. Flows over parabolic troughs been studied extensively because most solar panels have parabolic trough geometries. Meanwhile, some solar panels and most antennas located in windy highlands and open fields have parabolic dish geometries. So far, very little has been done for LES studies on flows past parabolic dishes at high Reynolds numbers. Thus, this study uses the LES method to scrutinize the flows over parabolic dishes with different focal ratios (f/D = 0.25–0.45) at a Reynolds number of 1.5×10⁵. The effects of the focal ratio on the recirculation bubble length, flow characteristics, and drag coefficients are examined. The results indicated that the recirculation zone size is not significantly affected by the focal ratio until the ratio is very small; the recirculation zone becomes noticeably enlarged only when the dish is largely curved, such that f/D ≤ 0.35. The pressure spectrum analysis shows that there are three different dominant frequencies, which are associated with the pulsation of the recirculation bubble, vortex shedding from the dish edge, and separated shear layer instability, respectively. The overall frequency trends for the parabolic dish with f/D = 0.25 are similar to those past the circular disk, except for the three dominant frequencies being shifted to lower values. The drag coefficient tends to decrease with an increase in the focal ratio.