RANS-based Aerodynamic Shape Optimization Investigations of the Common Research Model Wing

Abstract

The aerodynamic shape optimization of transonic wings requires Reynolds-averaged Navier-Stokes (RANS) modeling due to the strong nonlinear coupling between airfoil shape, wave drag, and viscous effects. While there has been some research dedicated to RANS-based aerodynamic shape optimization, there has not been an benchmark case for researchers to compare their results. In this investigations, a series of aerodynamic shape optimizations of the Common Research Model wing defined for the Aerodynamic Design Optimization Workshop are presented. The computational fluid dynamics solves Reynolds-averaged Navier-Stokes equations with a Spalart-Allmaras turbulence model. A gradient-based optimization algorithm is used in conjunction with a discrete adjoint method that computes the derivatives of the aerodynamic forces. The drag coefficient at the nominal flight condition is minimized subject to lift, pitching moment and geometric constraints. A multilevel acceleration technique is used to reduce the computational cost. A total of 768 shape design variables are considered, together with a grid with 28.8 million cells. The drag coefficient of the optimized wing is reduced by 8.5% relative to the baseline. The single-point design has a sharp leading edge that is prone to flow separation at off-design conditions. A more robust design is achieved through a multipoint optimization, which achieves more reliable performance when lift coefficient and Mach number are varied about the nominal flight condition. To test the design space for local minima, randomly generated initial geometries are optimized, and a flat design space with multiple local minima was observed.

Aerostructural optimization of the Common Research Model configuration

“…The CRM configuration is a useful benchmark for drag prediction, having served as the geometry of interest for both the 4 th and 5 th Drag Prediction Workshops b [3]. More recently, a modified the CRM wing has been used as a benchmark case for the for for the Aerodynamic Design Optimization Discussion Group (ADODG) [6,7,8,9].…”

Strategies for Solving High-Fidelity Aerodynamic Shape Optimization Problems

“…There are visible differences in the airfoils C p distributions, as shown in Figure 9. This might be caused by local minima that are close to each other, as previously observed by Lyu et al [16,11]. The multilevel approach has also been successfully applied in [11].…”

“…This study is performed using the benchmark case for aerodynamic design optimization developed by the Aerodynamic Design Optimization Discussion Group (ADODG) a : the lift-constrained drag minimization of the NASA Common Research Model (CRM) wing [13,14,15] with a RANS model that were presented at the 2014 AIAA Science and Technology Forum and Exposition in a special session organized by the ADODG [16,11,17,18,19].…”

Collaborative Aircraft Design Methodology using ADAS Linked to CEASIOM

“…for corresponding flight conditions. Usually to get a well designed wing a multi-level optimization 42 should be considered, namely, optimizations for cruise, takeoff and landing. For low speed aircraft a good number to assess the design is the Oswald factor e, which is not so high (e = 0.82) for the ADAS configuration.…”