Unified gas-kinetic scheme for reactive flow with multi-scale transport and chemical non-equilibrium

TL;DR

This paper extends the unified gas-kinetic scheme (UGKS) to simulate reactive flows with chemical non-equilibrium, effectively capturing multi-scale transport and complex physics in rarefied gas mixtures across various flow regimes.

Contribution

The study develops an extended UGKS that incorporates chemical non-equilibrium for reactive flows, advancing multi-scale flow simulation capabilities.

Findings

Validated UGKS against DSMC for shock and hypersonic flows.

Demonstrated UGKS's effectiveness in complex 3D re-entry scenarios.

Showed potential for industrial applications in aerospace and semiconductor manufacturing.

Abstract

Reactive flows for rarefied gas mixtures involve a multi-scale transport characterized by particle collisions and free streaming, and non-equilibrium physics containing multi-species interactions, and chemical non-equilibrium. These flows are pivotal in aerospace engineering and semiconductor manufacturing, impacting spacecraft control and thermal protection in near-space flight, and plasma etching for chip processing. Therefore, the simulation of these multi-scale and non-equilibrium flow is of scientific and industrial significance. Following the methodology of direct modeling, the unified gas-kinetic scheme (UGKS) is constructed to describe the multi-scale transport of gas molecules across all flow regimes. This study extends the UGKS to the reactive flows with chemical non-equilibrium for the capture of more complex flow physics. Test cases, including shock structures, hypersonic flows around a two-dimensional cylinder and the three-dimensional re-entry and space vehicle, and nozzle plume flow into a vacuum, are used to validate the UGKS through the comparison with the direct simulation Monte Carlo method. The study shows that the methodology of direct modeling and the extended UGKS have great potential for simulating multi-scale flows with complex non-equilibrium physics.