The Effect Of Wall Temperature Distribution And Blunt Cone Bluntness On The Stability And Transition Prediction In The Supersonic Boundary Layers

Hypersonic vehicle is a key part of the research and development of aerospace technology.However,there are still many problems to be solved in its design and manufacture,one of which is how to accurately predict the transition position of hypersonic vehicle boundary layer.For hypersonic plate boundary layer,the oncoming flow Mach numbers 4.5,6and 7,and under three different wall conditions including isothermal,adiabatic and wall temperature distribution conditions(Isothermal wall temperature takes as same as oncoming flow temperature and temperature distribution conditions give wall temperature at 120s,300s,400s and 600s four different times).For zero angle of attack cone boundary layer,the oncoming flow Mach number is 5,and the radii of six blunt heads are R*=1mm,1cm,5cm,10cm,20cm and 30cm,respectively.The gas parameters are taken as that of the air corresponding at a height of 30 km,the basic flow field is calculated by direct numerical simulation,then the stability analysis is carried out,and thee ~Nmethod is used to predicate the transition position.The main conclusions are as follows:1.For supersonic plate boundary layer:The longer the aircraft passes through the flow field,the wall temperature is closer to the adiabatic,the more unstable the first mode wave is and the more stable the second mode wave is.The first mode dominates the transition under the adiabatic wall conditions with Mach numbers of 4.5 and 6.In other cases,the transition is dominated by the second mode wave under three Mach numbers of the isothermal wall conditions,the temperature distribution wall conditions and the adiabatic wall condition at Mach number of 7.It is also found that the unstable frequency is the highest under the condition of isothermal wall,and the transition position is closer to the leading edge of the plate,and the larger the Mach number,the more forward the transition position is.The unstable frequency is the lowest under the condition of adiabatic wall,and transition position will move backward as the oncoming flow Mach number increase.In the case of the wall temperature distribution condition,the transition location will move forward as the oncoming flow Mach number increase.It is also found that the higher the wall temperature is,the further backward the transition location is.For the boundary conditions of the wall temperature distribution,it is difficult to find a certain temperature as the isothermal wall temperature to replace wall temperature distribution condition.So,the basic flow still needs to be calculated by direct numerical simulation.2.For supersonic blunt cone boundary layer of zero attack angle:With the increase of bluntness of the blunt cone,the unstable frequency range of the second mode neutral curve becomes narrower,the unstable region corresponding to the neutral curve moves backward,and the radius of the blunt head is linearly related to it.With the increase of bluntness of blunt cone,the transition position moves backward.The radius of blunt head is linearly related to the transition position.And according to the LST calculations,no transition reversal was found.Under the condition of isothermal wall,with the increase of wall temperature,the unstable region moves to the low frequency direction,which makes the second mode more stable and the transition position move backward.This is similar to the conclusion of the flat panel.