Transonic Airfoil Study Using Sonic Plateau, Optimization and Off-Design Performance Maps

A number of transonic airfoils, designed using differing approaches, are evaluated over a wide range of operating conditions, using a tool for generating aerodynamic performance maps. Details of key performance boundaries are also extracted, including drag divergence and separation onset. The aerodynamic performance maps and boundaries, which are based upon extensive use of a rapid 2D CFD tool, are first demonstrated on an existing airfoil, for which the design condition is known and for which experimental data is available. Aerodynamic maps are then presented for a series of airfoils which are designed using a sonic plateau, inverse design approach. Further maps are presented for airfoils designed using single-point and multi-point optimization. The impact of the alternative design approaches is studied, using the performance maps and the resulting characteristics of the performance boundaries. In particular, the trade-off between drag divergence and the onset of separation, combined with viscous and wave drag development, is presented. The study provides some insights into the challenge of achieving a well posed optimization formulation for transonic airfoil design

An Efficient Bi-Level Surrogate Approach for Optimizing Shock Control Bumps under Uncertainty

The assessment of uncertainties is essential in aerodynamic shape optimization problems in order to come up with configurations that are more robust. The influence of aleatory fluctuations in flight conditions and manufacturing tolerances is of primary concern when designing shock control bumps, as their effectiveness is highly sensitive to the shock wave location. However, exploring the stochastic design space for the global robust optimum increases the computational cost, especially when dealing with nonconvex design spaces and multiple local optima. The aim of this paper is to develop a framework for efficient aerodynamic shape optimization under uncertainty by means of a bi-level surrogate approach and to apply it to the robust design of a retrofitted shock control bump over an airfoil. The framework combines a surrogate-based optimization algorithm with an efficient surrogate-based approach for uncertainty quantification. The surrogate-based optimizer efficiently finds the global optimum of a given quantile of the drag coefficient. It outperforms traditional evolutionary algorithms by effectively balancing exploration and exploitation through the combination of adaptive sampling and a moving trust region. At each iteration of the optimization, the surrogate-based uncertainty quantification uses an active infill criterion in order to accurately quantify the quantile of the drag at a reduced number of function evaluations. Two different quantiles of the drag are chosen, the 95% to increase the robustness at off-design conditions, and the 50% for a configuration that is best for day to day operations. In both cases, the optimum configurations lead to an airfoil that is more robust to geometrical and operational uncertainties, compared to the configuration obtained through classical deterministic optimization

Calculation and measurement of transonic flows over aerofoils with novel rear sections

SIGLEAvailable from British Library Document Supply Centre- DSC:8670.19(RAE-TM-AERO--2145) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

CFD methods for drag prediction and analysis currently in use in UK

SIGLEAvailable from British Library Document Supply Centre- DSC:8670.19(RAE-TM-AERO--2146) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

A study flows over highly-swept wings designed for manoeuvre at supersonic speeds

Report also known as BR--112012SIGLEAvailable from British Library Document Supply Centre- DSC:8670.19(RAE-TM-AERO--2147) / BLDSC - British Library Document Supply CentreGBUnited Kingdo