Dissipation Scalings in the Turbulent Boundary Layer at Moderate $$Re_{\theta}$$

Abstract

We present an experimental and numerical study of the turbulent boundary layer at \(1200< Re_{\theta} <3400\). We propose a combined approach that involves the use of a multi-hole pitot probe, hot-wire anemometry and direct numerical simulations, that allows to characterise the isotropy and the energy dissipation scalings of the flow in the outer layer, in the range \(0.4< y/\delta <0.75\), with y the vertical coordinate and \(\delta\) the boundary layer thickness. We confirm previous results from the literature that show that for low values of \(Re_{\theta}\) (in our case \(Re_{\theta} <2500\)), on the outer layer the dissipation constant \(C_\varepsilon\) is Reynolds number dependent, following a \(Re_\lambda ^{-1}\) law. This dependency seems to be robust, as the value of \(C_\varepsilon\) collapses for previously reported direct numerical simulations and experiments with different incoming velocities. We also show that, while large scales of the flow are strongly anisotropic on the outer layer, the turbulence energy dissipation rate and the dissipation constant can still be characterised assuming local isotropy and homogeneity.