Gas-kinetic unified algorithm for computable modeling of Boltzmann equation for aerothermodynamics during falling disintegration of Tiangong-type spacecraft

Abstract

How to solve the hypersonic aerothermodynamics around large-scale uncontrolled spacecraft during falling disintegrating process from outer space to earth, is the key to predict the flight track of the end-of-life spacecraft reentry crash. To study aerodynamics of spacecraft reentry covering various flow regimes, the Gas-Kinetic Unified Algorithm (GKUA) has been presented by computable modeling of the collision integral of the Boltzmann equation over tens of years. On this basis, the rotational and vibrational energy modes are considered as the independent variables of the gas molecular velocity distribution function, a kind of Boltzmann model equation involving internal energy excitation is constructed by decomposing the collision term of the Boltzmann equation into elastic and inelastic collision terms under the conservation of the summation invariant and the H-theorem. The unified algorithm of the Boltzmann model equation involving thermodynamics non-equilibrium effect is presented for the whole range of flow regimes. The gas-kinetic massive parallel computing strategy is developed to solve the hypersonic aerothermodynamics with the processor cores of 512∼115000 at least 90% parallel efficiency. To validate the accuracy of the GKUA, the hypersonic flows are simulated including the reentry Tiangong-1 spacecraft shape with the wide range of Knudsen numbers of 260∼0.00005 by the comparison of the related results from the DSMC and N-S coupled methods, and the low-density tunnel experiment etc. For uncontrolled spacecraft falling problem, the finite-element algorithm of dynamic thermal-force coupling response is presented, and the unified simulation of the thermal structural response and the hypersonic flow field is tested on the vertical plate, hollow sphere and Tiangong-1 shape under the reentry aerodynamic environment. Then, the forecasting analysis platform of end-of-life large-scale spacecraft flying track is established on the basis of ballistic computation combined with reentry aerothermodynamics and deformation failure/ablation/disintegration.