Analysis and Measurements of a Simulated Atmospheric Boundary Layer Using Cowdrey Rods

Particle image velocimetry (PIV) measurements were performed to characterize a simulated atmospheric boundary layer (ABL) in a closed-return subsonic wind tunnel using two sets of Cowdrey rods located upstream of the test section. Three configurations were investigated: both rod sets installed, only the upstream set, and only the downstream set. Mean velocity, turbulence intensity, and spectral characteristics obtained from PIV were compared with hot-wire anemometry and seven-hole probe measurements, showing good overall agreement and clarifying the distinct roles of each grid. In addition, a corrected theoretical formulation of the Cowdrey method for generating an ABL was developed to resolve internal inconsistencies in the original derivation and to recover the same final design law, but on a physically consistent basis. The revised formulation provides a clear theoretical foundation for the Cowdrey method and can aid in the interpretation of measurements obtained with Cowdrey grids in wind tunnels.