Experimental And Numerical Research On Thermo-chemical Nonequilibrium Flow With Radiation Phenomenon

This paper is mainly about experimental and numerical study of hypersonic thermochemical nonequilibrium flow and its radiation characteristics. Experimental research includes:l).Highly accurate shock wave standoff distance of the hypersonic spherical steel model has been obtained in China Aerodynamics Research and Development Center (CARDC). The main facilities used are the Reentry Physics Ballistic Range and a high performance, pulsed Nd-YAG laser with pulse duration of 5ns. It is the first time in China to have obtained the clear laser interferogram and shadow graphs of the thermochemical nonequilibrium flowfield around the model without ablation. The error of measurement is about 5%. The model's flight velocity is 5.0~5.5km/s, and the chamber's pressure is 10~80mmHg. Computational Fluid Dynamics (CFD) and Computational Flow Imaging (CFI) methods are used to design and determine the experiment's scheme.2).The radiant intensities of the nonequilibrium flowfield of the hypersonic spherical model in visible light have been obtained under several conditions, and the experimental techniques have been analyzed. A double-slit visible-light radiometer is used with the central wavelength located in the band of green light(517.8nm and 519.8nm) and the half-width 6.6nm. The model's flight velocity is 4.8~5.7km/s, and the chamber's pressure is 10~80mmHg.Numerical research includes the computation of thermochemical nonequilibrium flowfield and its radiation characteristics.The research on numerical simulation of thermochemical nonequilibrium flow includes:1). Analyzing the physical and chemical models for thermochemical nonequilibrium flow. The Park's two-temperature model, Gupta's reaction model with 11 air species and related transportation model, vibration-dissociation coupling model and energy exchange mechanisms are chosen to solve the Navier-Stokes equations.2).Comparing and analyzing the NND scheme, Roe scheme, AUSM-family scheme and related numerical techniques(including the technique for speeding up convergence, MUSCL method, entropy fix method, diagonal implicit processing of source terms, etc.) in simulating thermochemical nonequilibrium flow. The result indicates that the AUSM-family scheme is the best while the implicit LUSGS method has the highest computational efficiency. This paper also puts forward a newentropy fix method, which is independent of the computational grid and is capable to minimize the dissipative effect in the boundary layer.3).The computational codes TCNEQ (2D, 3D), which are for axial symmetrical and three-dimensional flow, have been established by using the above-mentioned physical and chemical models. The codes have good adaptability with structured grids and high level of modularization. The computational aerodynamics and heat flux are consistent with those of the references and the codes have been validated using experimental data.4).It is the first time in China that high accurate comparative research between the experimental and computational shock wave standoff distances is carried out. Several air models are used in computation. The whole flowfield is experimentally validated using CFI method. With CFI method, the numerical results are processed to generate computational shadowgraphs and finite-fringe interferogram, which can be compared with the experimental photos directly.5).The three-dimensional code TCNEQ3D is used to simulate the whole flowfield around the reentry capsule of the Apollo spacecraft (including the base and wake flow). The aerodynamic coefficients of the capsule are calculated and compared with the references and experimental data. The analysis indicates that the nonequilibrium phenomenon is possibly one of the reasons for the discrepancy between the capsule's flight data and the wind tunnel data.The research on numerical computation of the radiation characteristics of thermochemical nonequilibrium flow includes:1. On the basis of the three types of the high temperature air radiation, analyzing and discussing in detail of the mechanism of continuum, atomic lines and m...