Optimization research on combination of spike and forward-facing jet using response surface methodology

Both spike and forward-facing jet can reduce the shock wave drag acted on a blunt head hypersonic vehicle significantly. However, they are not be adopted widely because of some shortages. The combination of spike and forward-facing jet takes advantages of both of them, while more complex aerodynamical phenomena and parameter optimization issue are involved. In this paper, the parametric optimization of combination of spike and forward-facing jet is carried out by response surface methodology. The objective of the optimization is to minimize the drag and the jet flux. The optimized parameters are the length of the spike, total pressure of the jet and the diameter of the jet out let. The response surface model is involved to feedback the relationship between the response and the designing parameters. Ⅳ-optimal is used to design the sample points, of which the response values are achieved through numerical simulation. The desirability value is used to estimate the benefits. The principal conclusions are as following:The function of drag and design parameters is supposed to be 2^nd or 3^rd order non-linear polynomial, and the coupling effects among design parameters are evident, especially between the diameter of jet outlet and the total pressure of jet. Response surface model speculated from sample points simulations reveals the relationship between the drag and the design parameters, from which the drag prediction interval of arbitrary parameters combination in design space can be obtained. The optimal parameters of minimum drag and jet mass flow are acquired, where the drag is predicted in a good precision. The study shows that response surface methodology in parameters optimization has high reliability and practicality with less computation requirement, and has good prospect of application in aircraft design.