Approximate analytic solution of heat conduction in hollow semi-spheres flying at hypersonic speed

Heat transfer in blunt noses of hypersonic vehicles with coolant inside can be approximately considered as heat conduction in hollow semi-sphere with aerodynamic heating on the outer boundary and enhanced cooling on the inner boundary. Theoretical investigations of temperature field in hollow semi-spheres were carried out by solving the two-dimensional axsymmetric conduction equation, which could be transformed into Legendre equation when the separation of variables is applied. However, for such a semi-sphere flying at hypersonic speed, the distribution of heat transfer rates as an outer boundary condition is so complex that the integration in the Legendre solution is nearly impossible to be completed. In this paper, a 4th order Legendre polynomial, derived by the method of undetermined coefficients, was adopted to approach the local similarity solution of hypersonic aerodynamic heating and simplify the integration process, by which an approximate solution could be set up for the temperature field. The approximate solution is also validated by comparing the analytical results with data from numerical simulations, in which the conduction equation is solved with the improved Richardson scheme. Both analytical and numerical results are compared to each other and match quite well.