Correlating turbulence intensity and length scale with the unsteady lift force on flat plates in an atmospheric boundary layer flow

Abstract

The correlation between turbulence intensity and length scale and the lift force on a horizontal flat plate in an atmospheric boundary layer flow is investigated in this study. Experiments were conducted in a large-scale wind tunnel to measure the peak loads on flat plate models of various chord length dimensions at different heights within simulated atmospheric boundary layers. The peak lift force coefficient on the flat plates was correlated with both turbulence intensity and length scale. The results show that the peak lift force coefficient on the flat plate is a function of vertical integral length scale (Lwx) and vertical turbulence intensity (Iw) in terms of a parameter defined as Iw(Lwxc)2.4, where c is the chord length of the plate. An increase in this turbulence parameter from 0.005 to 0.054, increases the peak lift force coefficient from 0.146 to 0.787. The established relationship is then used to predict the peak wind loads on full-scale heliostats within the atmospheric surface layer as a case study. It is found that decreasing the ratio of heliostat height to the chord length dimension of the mirror panel from 0.5 to 0.2 leads to a reduction of 80% in the peak stow lift force coefficient, independent of the terrain roughness.