Development and validation of a hybrid aerodynamic design method for curved diffusers using genetic algorithm and ball-spine inverse design method

Abstract

The inverse design is one of the aerodynamic design methods, in which the pressure distribution along the wall is known, and the duct geometry is unknown. To obtain the best geometry by the inverse design, the target pressure distribution along the walls should be optimum. This paper presents an aerodynamic design of diffusers by optimizing the wall pressure distribution and applying it to the ball-spine inverse design method. A code was first developed to solve the boundary layer equations using the integration method, and then incorporated into a genetic algorithm to optimize the wall pressure distribution to achieve the maximum pressure recovery without separation occurrence. Depending on the type of the duct, a series of constraints was applied to the wall pressure distributions during the optimization process. The optimized pressure distribution was considered as the target pressure distribution for the inverse design problem. The duct geometry changes during the inverse design process to reach one satisfying the target pressure distribution. An offline connection was observed between the ball-spine inverse design method and the genetic algorithm. The boundary layer code was the medium for this offline connection. The optimized wall pressure distribution and inverse design process were evaluated for a straight diffuser and three S-shaped diffusers with different height to length ratios. The results revealed the robustness of the offline link of the inverse design and the genetic algorithm for the optimal aerodynamic design of ducts.