Structure of stably stratified turbulent boundary layer: technical report

Abstract

The structure of a stably stratified thick boundary layer developed in a meteorological wind tunnel is investigated experimentally. Measurements of mean velocity, mean temperature, turbulent intensities, shear stress, heat fluxes and turbulent spectra made at a station 78 ft. from the leading edge are reported. Turbulent quantities were measured by using different hot-wire probes; the measurement technique which is a modification of the procedure suggested by Kovasznay (1953) is described. The results show that stability greatly reduces the turbulence in the boundary layer. The structure of the wall layer is discussed in the light of Monin and Obukhov's (1954) similarity theory and Ellison's (1957) theory. The results are also compared with previous measurements in the laboratory and in the surface layer of the atmosphere in stable conditions. It is shown that mean flow and turbulent characteristics of the wind tunnel boundary layer are well described by the similarity theory, and that this theory provides a good basis for the wind tunnel modeling of similar characteristics of the atmospheric surface layer. Measured spectra of lateral and vertical velocity fluctuations are shown to agree with Kolmogorov's (1941) similarity theory irrespective of the stability. The results are compared with Heisenberg's (1948) theory for the equilibrium spectra. Spectra of temperature fluctuations are shown to have similar form in agreement with Corrsin's (1951) theory. No buoyancy subrange could be identified in any of the spectra.