Asymptotic analysis of boundary thermal-wave process near the liquid–gas critical point

The role of near-critical properties has been considered as key point for the understanding of transient origins of fluid transport physics, especially in the boundary layers. Asymptotic model analysis with modified governing equations of the fluid has been utilized to study the characters of near-critical fluids subjected to a temperature pulse, under different boundary conditions: thermostatic or insulated. The asymptotic solutions show that the boundary layers are mainly governed by the diffusion effect (sensitive to spatial gradients) while exhibiting the wave character in bulk. When a small thermal pulse is imposed at the boundary, wave process with a magnitude about 0.05 mK is seen generated. The wave propagates in the one-dimensional cell, reflecting a quick re-distribution of parameters in acoustic timescale. Transient temperature and pressure results show that as the fluids flow across the boundary layers to the bulk, acoustic wave process is associated with that of the specific energy transportation process.