OPTIMIZATION OF THE AFT-BODY GEOMETRY OF AXI-SYMMETRIC SLENDER BODY BASED ON WAVE DRAG CONSIDERATIONS

摘要

The objective of the present work is to establish a comprehensive, universally valid, elegant and yet simple method to design slender axisymmetric body of minimum wave drag in transonic and supersonic flows, taking advantage of the progress of computational aerodynamics and optimization technique. Computational aerodynamics will also be used as a tool for numerical experiments in gaining physical understanding of the drag mechanism due to the geometry of the aft-body, such as the correlation between wave drag and wave distribution of the aft-body geometry, by analyzing previously known optimum aerodynamic shapes as well as verifying the validity of those obtained through minimization scheme. Due to its universality and elegance, the Modified Feasible Direction (MFD) based optimization program will be utilized, along with the linear slender body aerodynamics, also due to its elegance and which could shed some light on the generic optimization scheme. The efforts will be focused on inviscid flow. Based on the physical understanding gained above, a practical method of reducing the wave drag of a given body is developed for both bodies with pointed end and with base area, using shock wave generator at a particular location on the aft body. Upon validaton of the MFD optimization program by bench-marking the results with the existing optimum axi-symmetric slender bodies, the program is used to search for optimum aft body geometries which minimize the wave drag. The results show that the MFD optimization program can be effectively utilized in an aerodynamic optimization problem.