A novel transient-adaptive subcell algorithm with a hybrid application of different collision techniques in direct simulation Monte Carlo (DSMC)

Abstract

A novel hybrid transient adaptive subcell (TAS) direct simulation Monte Carlo (DSMC) algorithm is proposed to simulate rarefied gas flows in a wide range of Knudsen numbers. It is derived and analyzed by using a time and spatial discrete operator approach based on the non-homogeneous, local N-particle kinetic equation, first proposed by Stefanov. The novel algorithm is considered together with the standard and hybrid collision algorithms built on uniform grids. The standard collision algorithm uses only one single scheme—the NoTime Counter (NTC), or the Generalized or Simplified Bernoulli trials (GBT, SBT). The hybrid algorithm employs NTC, GBT, or SBT depending on the instantaneous number of particles in the considered cell. The novel hybrid TAS algorithm benefits from both the hybrid collision approach and the transient adaptive subcell grid covering each collision cell to achieve a uniform accuracy of order O(Δ t, Δ r) independently of the number of particles in the cells. To this aim, a local time step is defined as coherent with the TAS grid covering the corresponding collision cell. The novel hybrid TAS algorithm is tested on two-dimensional benchmark problems: supersonic rarefied gas flow past of a flat plate under an angle of incidence and pressure-driven gas flow in a microchannel. The results obtained by the hybrid TAS algorithm are compared to those obtained by the standard algorithms and the available Bird's DS2V code using nearest neighbor collision and open-source OpenFOAM code. The comparison shows an excellent accuracy of the suggested algorithm in predicting the flow field.

Numerical Investigation of Multiphase Flow in 2D Microchannel Using Volume of Fluid Method: A Study on Water Droplet Dynamics

“…When the volume fraction of the primary phase (C) is zero means the primary phase is absent from the cell. The primary phase and secondary phase are both present in the cell when C is between 0 and 1, with the primary phase taking up some space in the cell [39,40].…”

Direct Simulation Monte Carlo Simulation of the Effect of Needle Valve Structures on the Rarefied Flow of Cold Gas Thrusters

“…The hybrid algorithm employs NTC, GBT, or SBT depending on the instantaneous number of particles in the considered cell. The novel hybrid TAS algorithm benefits from both the hybrid collision approach and the transient adaptive subcell grid covering each collision cell to achieve a uniform accuracy of order O (Δt, Δr) independently of the number of particles in the cells [ 39 ].…”

Rarefied gas flow past a liquid droplet: interplay between internal and external flows

“…Since its development, the DSMC method has been ameliorated and employed to investigate several canonical rarefied gas flow problems; see, e.g. Rana, Mohammadzadeh & Struchtrup (2015), Stefanov, Roohi & Shoja-Sani (2022), Taheri, Roohi & Stefanov (2022), Sadr & Hadjiconstantinou (2023) and references therein. Nevertheless, the DSMC method also demands a very high computational cost for processes in the transition regime.…”