Analysis On Impulse Disturbance Flow Field Of Hypersonic Blunt Cone And Thermal Response Of Protection System

Hypersonic vehicle often meets a variety of unpredictable disturbance during the space flight process.The existence of disturbance has a significant influence on flow field,aerodynamic characteristic and structural strength.The diversity and uncertainty of disturbance bring big challenges to the design of hypersonic vehicle.The free-stream disturbance enters the flow field,generates a strong interaction with the bow shock and the boundary layers,and appears a more complex characteristic in the boundary layers.Therefore,it is very necessary to study the hypersonic flow field with disturbance over blunt cone.In this paper,free-stream disturbance hypersonic flow field and the thermal response of thermal protection system with damage are studied based on direct numerical simulation method and finite element method.The details are as following:1.A high-order accuracy direct numerical simulation method is introduced,and space discrete format and time discrete format are given.For the space discrete format,the inviscid item of N-S equations can be resolved into positive flux item and negative flux item through the flux vector splitting method,and is discreted using seven-order accuracy weighted essentially non-oscillatory algorithm.The viscid item is discreted by the six-order accuracy differential format.An explicit third-order total variation diminishing Runge-Kutta method is used for the time discrete format.The effectiveness of the numerical method is verified through two classic examples.2.The basic characteristics of hypersonic flow field with free-stream disturbance are studied using the high-order accuracy direct numerical simulation method.The effects of disturbance on the aero-thermodynamic parameters in the wall are analyzed,and the evolution of disturbance modal in the boundary layers based on Fourier Spectrum Analysis is discussed.The results showed that the effects of disturbance on the flow field can be divided into the disturbance effects and the disturbance after-effects.Disturbance effects have a large influence but a short action time,and the influence of the disturbance after-effects are the relatively small and long.The interaction of free-stream disturbance with the shock and boundary layer is very strong.The shock has an enlarge deformation and the disturbance is also significantly increase.A new disturbance wave appears within and outside the boundary layer after the interaction.The effects of disturbance on the head of blunt cone are significantly greater than the non-head area.3.The basic characteristics of hypersonic steady flow field and disturbed flow field under different wall temperature conditions are study based on the high-order accuracy direct numerical simulation method.The effects of wall temperature are analyzed based on based on Fourier Spectrum Analysis.The effects of wall temperature on the disturbance modal on boundary layer are study.The results show that the higher the wall temperature,the greater the thickness of boundary layer.As the flow push forward,the thickness of the boundary layer in the blunt cone increases significantly.The main impact of the wall temperature is found on the flow field in the boundary layer.The wall temperature plays an important role on the stability of the flow field.4.The thermal response and stress response characteristics of blunt cone under the free-stream disturbance are study using the finite element method.The effects of stream disturbance amplitude on the pressure response of blunt cone are discussed and mechanical characteristics of thermal response and stress response are compared.The results showed that the maximum stress and smaller strain region always appears the stagnation point and the central area of the leading edge of blunt cone.The stress of structure increases with the increasing of disturbance amplitude.As the disturbances spread to the downstream,temperature stress fields gradually expand to downstream.Compared to the pressure load,the temperature load has a more significant influence on the stress distribution.5.The coupled thermo-mechanical analyses of the ceramic tile protection system with damage are presented using ABAQUS finite element software.The thermodynamics response mechanism of ceramic tile protection system is analyzed considering the different of the heat flux in the damaged area.The influence of different sizes and damage locations on the thermodynamic response of the ceramic tile protection system is discussed.The existence of damage increases the maximum temperature and the maximum stress of the thermal protection structure.The side wall and the top corners of the cavity first reach the limit value of temperature and the thermal stress of the corner edge of the cavity is the largest.The maximum temperature and maximum stress increase with the increasing depth of damage,and the maximum temperature point moves down along the side wall of the cavity as the depth increases.The maximum temperature value is gradually decreased with the increasing of the damage length.The location of damage changes the distribution of temperature field and stress field,and thermal stress of structure damaged in the off-center is greater than that of structure damaged in the center.