GRID INFLUENCE ON AIR FLOW NON-UNIFORMITY IN WIND TUNNELS

摘要

The experimental results of the influence of fine-scale turbulence generated by the grids and vortex structure destroyer (VSD) on an inhomogeneous flow field in a wind tunnel are presented. It is shozvn that the application of turbulence grids leads to the dependence of the smoothing rate of non-uniform velocity profiles and the turbulence level on the grid cell size. In particular, the installation of a fine-meshed grid results in a slower rate of smoothing of the non-uniform velocity profiles and velocity fluctuations compared with the case without the grid. An optimal ratio between the cell size and the scale of inhomogeneity, at which the most efficient equalizing of the flow field inhomogeneity takes place, is found. When the VSD is installed in the large transverse gradient zone of the turbulence level, the rate of equalizing this gradient is significantly diminished due to a skin friction decrease in the turbulent boundary layer.