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With wave-particle decomposition, a unified gas-kinetic wave-particle (UGKWP)method has been developed for the multiscale flow simulations. The UGKWP methodcaptures the transport process in all flow regimes without kinetic solver'sconstraint on the numerical mesh size and time step being less than theparticle mean free path and collision time. In the current UGKWP method, thecell's Knudsen number, defined as the ratio of collision time to numerical timestep, is used to distribute the components in the wave-particle decomposition.However, the adaptation of particle in UGKWP is mainly for the capturing of thenon-equilibrium transport, and the cell's Knudsen number alone is not enough toidentify the non-equilibrium state. For example, in the equilibrium flow regimewith a Maxwellian distribution function, even at a large cell's Knudsen number,the flow evolution can be still modelled by the Navier-Stokes solver.Therefore, to further improve the efficiency, an adaptive UGKWP (AUGKWP) methodwill be developed with the introduction of an additional local flow variablegradient-dependent Knudsen number. As a result, the wave-particle decompositionin UGKWP will be determined by both cell's and gradient's Knudsen numbers, andthe particle in UGKWP is solely used to capture the non-equilibrium flowtransport. The AUGKWP becomes much more efficient than the previous one withthe cell's Knudsen number only in the determination of wave-particlecomposition. Many numerical tests, including Sod tube, shock structure, flowaround a cylinder, flow around a reentry capsule, and an unsteady nozzle plumeflow, have been conducted to validate the accuracy and efficiency of AUGKWP.Compared with the original UGKWP, the AUGKWP achieves the same accuracy but hasadvantages in memory reduction and computational efficiency in the simulationfor the flow with the co-existing of multiple regimes.

Adaptive wave-particle decomposition in UGKWP method for high-speed flow simulations