中文摘要：

如何准确可靠地模拟从外层空间高稀薄流到近地面连续流的航天器高超声速绕流环境与复杂流动变化机理是流体物理的前沿基础科学问题．基于对Boltzmann方程碰撞积分的物理分析与可计算建模，确立了可描述自由分子流到连续流区各流域不同马赫数复杂流动输运现象统一的Boltzmann模型速度分布函数方程，发展了适于高、低不同马赫数绕流问题的离散速度坐标法和直接求解分子速度分布函数演化更新的气体动理论数值格式，建立了模拟复杂飞行器跨流域高超声速飞行热环境绕流问题的气体动理论统一算法．对稀薄流到连续流不同Knudsen数0．002≤Kn∞≤1．618、不同马赫数下可重复使用卫星体再入过程（110一70km）中高超声速绕流问题进行算法验证分析，计算结果与典型文献的MonteCarlo直接模拟值及相关理论分析符合得较好．研究揭示了飞行器跨流域不同高度高超声速复杂流动机理、绕流现象与气动力／热变化规律，提出了一个通过数值求解介观Boltzmann模型方程，可靠模拟高稀薄自由分子流到连续流跨流域高超声速气动力／热绕流特性统一算法．

英文摘要：

How to solve hypersonic aerothermodynamics and complex flow mechanism covering various flow regimes from high rarefied free-molecular flow of outer-layer space to continuum flow of near-ground is one of the frontier basic problems in the field of fluid physics. In this work, the unified Boltzmann model equation based on the molecular velocity distribution function is presented for describing complex hypersonic flow transport phenomena covering all flow regimes by physics analysis and model processing of the collision integral to the Boltzmann equation. The discrete velocity ordinate method is developed to simulate complex flows from low Mach numbers to hypersonic flight, and the gas-kinetic coupling-iteration numerical scheme is constructed directly to solve the evolution and updating of the molecular velocity distribution function by employing the unsteady time-splitting method and the NND finite-difference technique. Then, the gas-kinetic unified algorithm （GKUA） is presented to simulate the three-dimensional hypersonic aerothermodynamics and flow problems around space vehicles covering various flow regimes from free-molecule to continuum. To verify the accuracy and reliability of the present GKUA and simulate gas thermodynamic transport phenomena covering various flow regimes, firstly, the two-dimensional supersonic flows around a circular cylinder are simulated in the continuum regime of Kn∞ = 0.0001 and in the high rarefied regime of Kn∞ = 0.3 through the comparison between the Navier- Stokes （N-S） solution and the direct simulation Monte Carlo （DSMC） result, respectively. It is indicated that the GKUA can exactly＇ converge to the N-S solution in the continuum flow regime, and the computed results of the GKUA are consistent with the DSMC simulation with a small deviation of 0.45% in the high rarefied flow regime. Then, the three- dimensional complex hypersonic flows around reusable satellite shape are studied as one of the engineering applications of the GKUA with a wide range 0.002 ≤ Kn?