Numerical Simulation Of Gap Effect In Aerodynamic Heating

Supersonic aircrafts are facing the challenge of aerodynamic heating, in order to solve the thermal barrier, we need to install thermal protection system outside the aircrafts, for example, the thermal protection tile on the space shuttle. Because of the special functional requirements, different gaps are often designed on surface of the thermal protection layer, these gaps can interfere with flow boundary layer, and local thermal environment is formed. Empirical researches at home and abroad were carried out on gap effect, but there was few numerical simulation work. This paper mainly discussed the aerodynamic heating gap effect scientific questions, and is great significant to realize the refinement design of the supersonic aircraft thermal protection system.In this paper, the main work consists of two parts:gap effect in aerodynamic heating and measures to reduce the gap effect.Firstly, based on the finite volume method, the two-dimensional compressible Navier-Stokes equations were solved, the S-A turbulence model transport equation was used to close the control equations in calculation, quadrilateral grid and triangular grid structure was used in grid mesh, the Roe space discrete format and the Runge-Kutta time discrete format was also used to discrete the control equations, and to calculate the derivative argument in the control equations, the Green-Gauss Node Based method was used, models with different angle of attack, Mach number, width depth ratio were established. The gap effect under the transonic and supersonic flow condition was simulated with Fluent successfully. The results show that:the distribution of heat flux in gaps show a "U" shape, with the increase of gap depth, the heat flux ratio decreases, till the "dead zone" appeared. While with the increase of the Mach number and angle of attack, the heat flux in gap increases.Then, gap effect coefficient was discussed in this paper. The gap effect coefficient concept was proposed, which means the ratio of the heat flux value at the gap windward side vertices and the plate heat flux value of the corresponding points. Models with different chamfers and convex angle were established. The results show that:setting chamfer at the windward side vertices can effectively reduce the gap effect coefficient, while setting convex angle at the same vertices, the gap effect coefficient reduced.This work was supported by the National Natural Sciences Foundation of China (No.11272042).