Shallow mixing layers over hydraulically smooth bottom in a tilted open channel

• DOI: 10.1017/jfm.2022.818
• Publication Date: 2022-11-08T10:25:42Z
• Authors: Sébastien Proust; Céline Berni; Vladimir I. Nikora
• Keywords: Flume; Shear velocity; Splitter plate; Length scale

Shallow mixing layers (SMLs) behind a splitter plate were studied in tilted rectangular open-channel flume for range of flow depths and the initial shear parameter ${\lambda = (U_{2}-U_{1})/(U_{2}+U_{1})}$ , where $U_1$ $U_2$ are streamwise velocities slow fast streams, respectively. The main focus study is on (i) key parameters controlling time-averaged SMLs; (ii) emergence spatial development Kelvin–Helmholtz coherent structures (KHCSs) large- very-large-scale motions (LSMs VLSMs) associated turbulence statistics. features SMLs mostly controlled by bed-friction length scale $h/c_f$ $\lambda$ as well spanwise $V$ momentum fluxes $UV$ $h$ $c_f$ depth coefficient, For all cases, effect layer SML growth comparatively weak, dominate over turbulent fluxes. Initially, KHCSs their scales largely depend . cannot form if \lessapprox 0.3}$ resembles that free layers. Further downstream, becomes dependent number $S c_f \delta _v /(4 h \lambda )$ $\delta _v$ vorticity thickness. When \gtrapprox 0.01$ longitudinally stretched scaled transverse decrease with increasing $S$ presence LSMs/VLSMs away from depends -value, particularly when $\lambda > 0.3$ resembling conventional flows small.