DSMC study of hypersonic rarefied flow using the Cercignani–Lampis–Lord model and a molecular-dynamics-based scattering database

Abstract

This study proposes a scattering database method to model gas–solid interaction based on a database of distributions of scattering velocity obtained by a molecular dynamics simulation. The proposed method is used as the boundary condition in the direct simulation Monte Carlo method to simulate hypersonic flow over a rounded wedge at different Knudsen numbers (Kn). The effects of different wall models [e.g., the scattering database method and the Cercignani–Lampis–Lord (CLL) model] on the flow simulation were compared and analyzed. When Kn ≥ 1, the results based on the CLL model are evidently different from those of the scattering database model, where this difference increases with the degree of rarefication of flow. The mechanism of this discrepancy is such that when the flow is rarefied, a large number of freestream molecules from the far-field directly collide with the wall. In particular, near the stagnation point, the tangential reflection kinetic energy of freestream molecules is amplified due to the conversion of their normal incident kinetic energy. The scattering feature of this conversion is challenging to reproduce based on the theoretical framework of the CLL model. Still, a specific local parameter can describe the ratio of this conversion. Therefore, compared with the traditional wall model, the scattering database method can show more detailed scattering features and, hence, could be a promising tool for the study of gas–solid interaction in hypersonic rarefied flow.

Investigation of the Inverse Magnus Effect on a Rotating Sphere in Hypersonic Rarefied Flow

“…In this section, the numerical method used in this investigation is described, followed by two benchmark cases to validate the in-house code developed by the first author in previous works [23][24][25].…”

DSMC Study of Strong Shear Nonequilibrium Phenomenon in Hypersonic Knudsen-Layer Flows

“…The flow case was simulated by the DSMC code based on the algorithm of Bird. The DSMC code was detailed in previous papers of authors [11,12]. As shown in figure 1, the flowfield settings of the plane Couette flow are as follows: the argon gas is driven by the upper wall along the positive x direction at the velocity value uup; the lower wall is fixed at coordinate z = 0, i.e., the lower-wall speed is 0; the spacing between the two walls is Lz; the reference shear rate γ = uup/Lz; the length of the wall is Lx; the wall model is the CLL model and a diffuse-reflection wall, i.e., its accommodation coefficient is 1; the gas boundaries are periodic.…”

Numerical study of strong shear nonequilibrium phenomenon and its relaxation mechanism in hypersonic Knudsen layer flows based on the direct simulation Monte Carlo method

“…In order to provide a benchmark for the parametric study, a test case of plane Couette ow was simulated by the DSMC code based on the algorithm of Bird. The DSMC code has been tested and detailed in our previous articles [33,34]. Figure 1 shows the physical model and simulation result of the test case.…”

“…Figure 11 shows the variation of ux v x distributions in cases 6.1-6.4, where the ux v x distribution records the v x distribution in an upward molecular ux that is de ned as all the molecules crossing the interface between two statistical layers along the positive z direction (i.e., v z > 0). This statistical way was usually used in the study of gas-solid interaction [34] to observe the v distribution of incident/re ected molecular ux at the wall. Here, it is used to observe the v distribution after molecular collisions.…”