| A new inverse design method for complex 3D aerodynamic and hydrodynamic systems is presented. The method uses an existing 2D inverse design procedure to design a series of airfoils in isolation. The airfoils are used to create a Non-Uniform Rational B-spline (NURBS) surface for each component in the geometry. If the geometry consists of two or more components, the surface-to-surface intersection problem is written as a constraint function that is solved by a well-established continuation method. Those parts of the surfaces exposed to the flow are discretized and a 3D flow analysis is performed. The results of the flow analysis are used to update the input to the 2D design code until the desired 3D flow characteristics and geometric constraints are satisfied.; Several suitable iteration procedures are discussed, and their relative convergence rates and computational speeds are compared. A transpiration method is used to significantly increase the speed of the Jacobian evaluations. The introduction of the transpiration method reduces the computational time to such an extent that most typical design problems can be performed in less than 10 minutes on a desktop computer with a 1.8 GHz processor.; A unique feature of the current design method is that it produces the initial shape in the first step of the iteration process. Most 3D inverse design methods expect the designer to provide an initial shape or surface mesh, which is then adjusted in designated areas by the inverse method. The current method, in contrast, only requires the designer to specify the general features of the body and where the control airfoils are to be placed.; Five examples, showing both lifting and non-lifting bodies, are presented. The final two examples demonstrate how the method can be applied to the design of geometries consisting of several components. The method was able to produce the desired aerodynamic and geometric characteristics for all the example cases. It was also able to complete each design stage in less than 10 minutes---an important consideration when using the method as a practical design tool. |
