Physical arguments and experimental evidence in support of the mesolayer theory of turbulence

Experimental data are studied in light of the mesolayer theories of turbulence developed for a number of problems including flow in a pipe, the boundary layer at zero incidence, and the atmospheric boundary layer. The mesolayer theories take into account the presence of large-scale eddies near the wall. The interaction of big eddies with the surface generate a second boundary layer, called the mesolayer, whose thickness, scaled on the friction velocity u sub tau and viscosity v, is proportional to R(1/2) = (u sub tau H/v)(1/2), where H is the outer length. Inside this layer, both viscosity and the outer length are important. The systematic deviation of mean velocity data about the logarithmic law in pipe-flow and turbulent boundary layer is examined. It varies at R(1/2) and can be attributed to mesolayer effects. Analysis also strongly suggests that some quanities directly connected to the large-scale eddies near the wall scale on the mesolayer thickness. The existence of the mesolayer between the inner and outer regions prevents the commonly assumed overlap--the logarithmic profile.