Fine Numerical Simulation/Experimental Study On High Speed Flow And Aero-Optics Application

As a key problem in fluid dynamics research and technology application, the complex supersonic/hypersonic flow involves shock waves, flow transition, high Reynolds number flow, unsteady flow, and turbulent vortex separation. Caused by the supersonic/hypersonic flow, there exist complex physical phenomena such as aero-optical effects. In this dissertation these flow phenomena and physical phenomena were studied based on detailed numerical simulation and experimental method.The LES/RANS hybrid algorithm was proposed, considering the compressibility effects, to solve the problem of fine simulation of supersonic/hypersonic flow. In order to enhance the simulation efficiency a large-scale parallel simulation strategy was carried out, a PC cluster based parallel computing platform was set up, and a parallel program was achieved.Some classic examples, such as Lax shock wave tube problem, moving shock/density wave interference, double Mach reflection and shock/vortex interference, were carried out for investigating numerical methods. And supersonic/hypersonic shock/boundary layer interaction problem was in-depth validated and studied. At last, the 5th order WENO space scheme and 3rd order TVD Runge-Kutta temporal scheme are used in LES/RANS hybrid method to solve the problem of supersonic/hypersonic fine flow simulation. The results showed that the method meets the requirements of sophisticated simulation of supersonic/hypersonic flow.Experimental research and numerical simulation were used to study hypersonic inlet's flow structure and starting characteristics in the process of inlet lip opening, and got some very valuable results. During experiment, a directly connected wind tunnel was independently designed to simulate a free stream Mach at 5.3, based on which the dynamic process of inlet opening was studied; by measuring the wall pressure distribution on the inlet, the inlet flow characteristics during the process of inlet opening were studied. Based on experiment, the numerical simulation method was used to simulate some typical states in the process of inlet opening. The complex shock/boundary layer interaction phenomenon was analyzed, and the starting characteristics of the inlet with boundary layer separation were also discussed.Focus on the aero-optical effect derive from high speed flow field, the intrinsic link between optical transmission and flow field property was analyzed; the forms of expression and simulation method were built to analyze the optical transmission effect caused by "near field", such as turbulent boundary layer, shear layer and shock wave; then a criterion of solution is proposed and discussed particularly.The ray tracing method used in the study of aero-optical effects was developed. The method was based on grids and flow field data, using Runge-Kutta ray tracing method as the basic way. Based on flow field grid and data, a self-adaptive ray tracing algorithm was proposed, where the tracing step distance is self-adaptive according to local refraction index gradient and grid geometry scale. It can well solve the light field in the presence of large refractive index gradient (corresponding to large density gradient).Using large scale parallel computing, Settles cavity's supersonic three-dimensional flow was simulated. The velocity distribution and pulse mass flow rate of shear layer and re-attached region has been calculated, and results tallied with experimental data. Based on the calculated flow field, the optical transmission effects caused by cavity shear layer were researched. The results showed that, cavity flow leaded to severe wave front distortion and significantly reduced light intensity Strehl ratio. Another typical open cavity with the length-depth ratio L/D=5 was also studied. Its three-dimensional unsteady flow and self-oscillation characteristics were researched, as well as aerodynamic noise, self-oscillation mode. The results tallied with the data from relevant publications.