Thermal relaxation and critical instability of near-critical fluid microchannel flow

摘要

We present two-dimensional numerical investigations of the temperature and velocity evolution of a purennear-critical fluid confined inmicrochannels. The fluid is subjected to two sides heating after it reached isothermalnsteady state. We focus on the abnormal behaviors of the near-critical fluid in response to the sudden imposednheat flux. New thermal-mechanical effects dominated by fluid instability originating from the boundary andnlocal equilibrium process are reported. Near the microchannel boundaries, the instability grows very quickly andnan unexpected vortex formation mode is identified when near-critical thermal-mechanical effect is interactingnwith the microchannel shear flow. The mechanism of the new kind of Kelvin-Helmholtz instability induced bynboundary expansion and density stratification processes is also discussed in detail. This mechanism may bringnabout innovations in the field of microengineering.