On stability of channel flow of thermoviscous fluid

Resumo

The paper presents key results on a large-scale entrainment of thermoviscous liquid layers with different temperatures and their further mixing observed in the plane-parallel flow with an inflectional velocity profile. We show that the instability development in the channel is more intensive at the inflection point vicinity and is not related directly to vorticity generation in the near-wall region. The considered flow being unstable relative to the finite-amplitude harmonic disturbances possesses several resonant frequencies initiating the most intense entrainment. Temperature fields are analyzed based on the time-averaged entrainment layer thickness and temperature isoline displacement. We discuss the spectral properties of flow enstrophy, vorticity, and kinetic energy in terms of asymptotics of cascades observed and coherent structures. Okubo-Weiss criterion is used for mapping of four flow zones wherein an active filamentation of the turbulent veil or long-term existence of vortex structures is possible.