Vamshi Mohan Korivi

Sensitivity derivatives for three dimensional supersonic Euler code using incremental iterative strategy

In a recent work, an incremental strategy was proposed to iteratively solve the very large systems of linear equations that are required to obtain quasianalytical sensitivity derivatives from advanced computational fluid dynamics (CFD) codes. The technique was sucessfully demonstrated for two large two-dimensional problems: a subsonic and a transonic airfoil. The principal feature of this incremental iterative stategy is that it allows the use of the identical approximate coefficient matrix operator and algorithm to solve the nonlinear flow and the linear sensitivity equations; at convergence, the accuracy of the sensitivity derivatives is not compromised. This feature allows a comparatively straightforward extension of the methodology to three-dimensional problems; this extension is successfully demonstrated in the present study for a space-marching solution of the three-dimensional Euler equations over a Mach 2.4 blended wing-body configuration.

Observations on computational methodologies for use in large-scale, gradient-based, multidisciplinary design

Various computational methodologies relevant to large-scale multidisciplinary gradient-based optimization for engineering systems design problems are examined with emphasis on the situation where one or more discipline responses required by the optimized design procedure involve the solution of a system of nonlinear partial differential equations. Such situations occur when advanced CFD codes are applied in a multidisciplinary procedure for optimizing an aerospace vehicle design. A technique for satisfying the multidisciplinary design requirements for gradient information is presented. The technique is shown to permit some leeway in the CFD algorithms which can be used, an expansion to 3D problems, and straightforward use of other computational methodologies.

Methodology for Calculating Aerodynamic Sensitivity Derivatives

A general procedure is developed for calculating aerodynamic sensitivity coefficients using the full equations of inviscid fluid flow, where the focus of the work is the treatment of geometric shape design variables. Using an upwind cell-centered finite volume approximation to represent the Euler equations, sensitivity derivatives are determined by direct differentiation of the resulting set of coupled nonlinear algebraic equations that model the fluid flow

Transonic turbulent airfoil design optimization with automatic differentiation in incremental iterative forms

The primary effort in this study is to develop a practical approach for incorporating a validated computational fluid dynamics (CFD) code into an aerodynamic design optimization procedure with minimal code modification. The approach relies on the automatic differentiation tool ADTFOR to generate the grid sensitivities and derivative terms required by the incremental iterative method for aerodynamic sensitivity analysis. Transonic turbulent airfoil design optimization, based on the Navier-Stokes equations, is chosen as a sample problem to facilitate discussion of the code implementation procedure and the factors that affect the computational efficiency of aerodynamic design optimization.

Aerodynamic optimization using sensitivity derivatives from a three-dimensional supersonic Euler code

Initial results from a three-dimensional marching Euler code equipped with an efficient sensitivity analysis capability are presented. The aerodynamic sensitivity derivatives with respect to wing geometry parameters obtained by the incremental iterative method are compared with those obtained by an efficient central finite differencing method and are both accurate and computationally cheaper. Sample cases for a Mach 2.4 high-speed civil transport wing-body configuration are shown that indicate the feasibility of using these sensitivity derivatives in aerodynamic optimization studies. These demonstrations have been given for design variables that determine wing planform and control flap deflections. The filleted wing-body geometry and computational fluid dynamics grid are modified by automated surface geometry and grid generation codes through which sensitivity information is propagated