11 Julho 2017, 11:38 - Jorge Manuel Fontes Coelho
Turbulent/non-turbulent interfaces in a stably stratified fluid
Tomoaki Watanabe (Nagoya University)
Turbulence in the natural environment is often localized and bounded by laminar (non-turbulent) flows, where turbulence is separated from non-turbulent fluids by an interfacial layer called turbulent/non-turbulent interface layer (TNTI layer). These flows are often stably stratified, such as ocean mixing layers and atmospheric boundary layers. Stably stratified fluids support propagation of internal gravity wave, which can transport energy and momentum. In the present study, localized turbulence bounded by non-turbulent fluids with internal gravity wave is studied with direct numerical simulations of stably stratified shear layers in a uniformly stratified fluid. A TNTI layer is detected by identifying the turbulent region with potential vorticity. The flow properties near the TNTI layer change depending on the local buoyancy Reynolds number near the interface. An imprint of the internal gravity wave propagating in the non-turbulent region is found for vorticity within the TNTI layer, inferring that the interaction between turbulence and internal gravity wave occurs. The amount of the kinetic energy extracted from the turbulent region by the internal gravity wave is comparable to the dissipation in the turbulent region.