Multiobjective Design Exploration of an Aeroacoustic Design Problem for Rocket Launch Site with Evolutionary Computation and Large Eddy Simulations

Abstract

In this study, multiobjective design exploration for a rocket launch site is conducted using the evolutionary computation with the large eddy simulation to understand the acoustic characteristics associated with various launch sites and find design information such as trade-off relation among objective functions. The launch site is described by the curved surface. The flat plate inclined with 45 degree is considered as the reference configuration. The objective functions of multiobjective aeroacoustic design optimization are, 1) minimization of averaged sound pressure level near the payload fairing, 2) minimization of maximum pressure on the curved surface of the rocket launch site, and 3) minimization of the difference of the curved surface from the flat plate inclined with 45 degree. Threedimensional compressible Navier-Stokes equations are solved with the modified weighted compact nonlinear scheme. The total number of evaluation in multiobjective evolutionary computation is 2500, and the evaluation of one configuration necessitates the use of 130 nodes(1040 total cores) using ”K” supercomputer. Firstly, the analysis of non-dominated solutions clearly shows that there are various trade-off relations and correlations among the objective functions. Furthermore, the analysis of flow fields shows that as the curved surface around the impingement region becomes steeper, the acoustic waves generated from the impingement region weaken. This is because the curved surface becomes steeper, the separation bubble near the impingement region becomes smaller, and finally disappears. The proper orthogonal decomposition(POD) analysis is conduced to extract the characteristic modes from characteristic non-dominated solutions.