Analysis of Thermodynamically Induced Compressibility in Supercritical Mixing Layers

This research builds upon recent work reported on thermally inhomogeneous supercritical ����2 mixing layers that focus on the effects of thermodynamic compressibility on supercritical mixing [1]. By comparing the findings in Ref. [1] to newly generated data sets, this research identifies key differences in the turbulent structures and mixing dynamics between supercritical and ideal-gas single component and multi-component mixtures. Using an identical setup, Large Eddy Simulation (LES) was performed on a thermally inhomogeneous ����2 mixing layer under ideal-gas settings and on a thermally homogeneous ����4/��2 mixing layer under supercritical fluid conditions. Data sets were produced over a range of grid resolutions, from a relatively coarse grid to a Wall Resolved LES (WRLES) resolution. Analysis shows that the sensitivity of the time derivatives of pressure and temperature to modulating parameters such as ��^2/(������), ����/����, and ����/���� is orders of magnitude greater under near-critical conditions compared to the ideal-gas scenario. The structure of the turbulence within the mixing layer is investigated by analyzing the shape of the Reynolds stress ellipsoids formed within the flow. Comparisons between anisotropy invariance maps reveal more anisotropic turbulence at supercritical conditions. This observation is complemented by the presence of strong density stratification both in the thermally inhomogeneous and multi-component flows, which inhibits velocity fluctuations in directions normal to the local gradient.