Nonlinear Modeling Study of Aerodynamic Characteristics of an X38-like Vehicle at Strong Viscous Interaction Regions

Abstract

Strong viscous interaction and multiple flow regimes exist when vehicles fly at high altitude and high Mach number conditions. The Navier–Stokes(NS) solver is no longer applicable in the above situation. Instead, the direct simulation Monte Carlo (DSMC) method or Boltzmann model equation solvers are usually needed. However, they are computationally more expensive than the NS solver. Therefore, it is of great engineering value to establish the aerodynamic prediction model of vehicles at high altitude and high Mach number conditions. In this paper, the hypersonic aerodynamic characteristics of an X38-like vehicle in typical conditions from 70 km to 110 km are simulated using the unified gas kinetic scheme (UGKS), which is applicable for all flow regimes. The contributions of pressure and viscous stress on the force coefficients are analyzed. The viscous interaction parameters, Mach number, and angle of attack are used as independent variables, and the difference between the force coefficients calculated by UGKS and the Euler solver is used as a dependent variable to establish a nonlinear viscous interaction model between them in the range of 70–110 km. The evaluation of the model is completed using the correlation coefficient and the relative orthogonal distance. The conventional viscous interaction effect and rarefied effect are both taken into account in the model. The model can be used to quickly obtain the hypersonic aerodynamic characteristics of X38-like vehicle in a wide range, which is meaningful for engineering design.

Unlocking the Key to Accelerating Convergence in the Discrete Velocity Method for Flows in the Near Continuous/Continuous Flow Regimes

“…These methods aim to surmount the limitations tied to mesh size and time step size in the conventional DVM by utilizing the multiscale local solution of the Boltzmann-BGK equation for calculating numerical flux. Notable examples encompass the unified gas kinetic scheme (UGKS) [24][25][26] and the discrete unified gas kinetic scheme (DUGKS) [27][28][29]. The UGKS employs a local integral solution of the Boltzmann-BGK equation in calculating the numerical flux, while the DUGKS adopts a local discrete characteristic solution.…”

Kinetic Theory-Based Methods in Fluid Dynamics

“…After a year-long preparation and a rigorous peer-review process, 12 articles were finally accepted for publication in this Special Issue. These articles report the latest developments in kinetic-theory-related numerical schemes [1,2] and typical applications in multiphase flows [3], thermal flows [4], micro/nano flows [5,6], flows in porous media [7], and compressible flows [8,9], as well as other areas of fluid dynamics [10][11][12]. Specifically, Song et al [1] proposed a simplified linearized Boltzmann method for the effective simulation of acoustic propagation with a lower cost of virtual memory.…”

“…Zhou et al [8] employed the gas-kinetic BGK scheme and performed a thorough analysis of the thermal protection system for vehicles operating in extreme conditions of hypersonic flows. Jiang et al [9] investigated the aerodynamic characteristics of an X38-like vehicle considering strong viscous interactions and complicated rarified effects, which could be of reference value to engineering designs. Morozov and Titarev [10] utilized three numerical tools to study the dynamics of gas expansion due to intense nanosecond laser evaporation into vacuum, with specific attention paid to factors that are essential for experimental measurements.…”