On simulating the varying fraction of the lower part of the adiabatic boundary layer

Abstract

Results of a theoretical study on the feasibility and techniques of simulating the varying fraction of the lower part of the natural boundary layer in a wind tunnel are presented. It is shown that from the mean velocity profile point of view the entire simulated boundary layer may correspond to the lowest fraction of the atmospheric boundary layer desired, within reason. However, the turbulence intensity characteristics may impose certain restriction natural boundary layer, while simulating the lower 30 to 100 m of the atmosphere. Alternatively, while simulating the lower 100 to 300 m of the atmosphere (natural boundary layer thickness 700m) the turbulence intensity characteristics may impose certain limits on the extent of the atmospheric boundary layer, the simulated boundary layer may correspond to. As long as the power spectra in the simulated boundary layer do not show any significant change with height and show good agreement with the von Karman model spectrum, the simulated boundary layer may be taken to correspond to lowest desired fraction of the atmospheric boundary layer within reason but adequate inertial frequency range should be generated in the simulated turbulent boundary layer. The atmospheric boundary layer height of at least two to three times the structure height should be simulated. Further, proper simulation of the turbulence characteristics should be of primary importance and correct simulation of the shear profile should be of secondary importance.