Multi-Objective Aerodynamic Optimization of External Compression Supersonic Intake using Kriging/MOGA
A formal optimization procedure is reported for an external-compression supersonic intake with the twin objectives of maximizing the total pressure recovery while simultaneously minimizing the intake pressure drag. Prior to that, two key design modifications are introduced to the supersonic intake. First, a small cowl offset distance is applied, deliberately violating the shock-on-lip condition. This ensures an attached external shock at the cowl, which is beneficial, in return for a small, controlled flow spillage. Second, in a novel development, an internal wedge angle is introduced at the cowl lip, which forces the terminal shock to be a strong oblique shock. This also helps anchor the terminal shock at the cowl lip for a range of intake back-pressure values, and reduces the cowl external angle with respect to the free stream. The optimization problem is formulated based on axiomatic design theory with the two design parameters innovatively selected as the Oswatitsch ramp angle triplets and the cowl internal wedge angle, respectively. A multi-objective genetic algorithm (MOGA), assisted by a Kriging meta-model with infilling, is run in tandem with a RANS solver, to iteratively compute the Pareto front. The optimal design yields ramp angles that are somewhat smaller than the theoretical Oswatitsch values, yet returns a total pressure recovery very close to the Oswatitsch optimum while reducing the intake pressure drag significantly.