Analysis of the turbulent kinetic energy budget for meandering motion appearing in a backward-facing step flow of viscoelastic fluid in high reynolds number

It is known from our previous study (Ii et al., 2015) that a remarkable meandering motion occurs depending on the Reynolds number and surfactant concentration in a backwardfacing step flow of a viscoelastic surfactant solution in high Reynolds number. The present report provides the examination of the meandering motion from the analysis of the turbulent kinetic energy budget. In particular, we capture the characteristic of the streamwise turbulent velocity fluctuation in terms of analysis of production, turbulent diffusion and dissipation terms. We conclude that the meandering motion become prominent in the flow-regime where the production rate surpasses the dissipation rate resulting in onset of instability at large-scale eddies.