Robust Design Optimization of Hydrodynamic Characteristics of Airfoil 791

Chenghu ZHANG (School of Energy and Power Engineering, Jiangsu University)

CHALLENGE - A lot of uncertainties (such as geometric environmental parameter fluctuation) exist in practical engineering and production application environment, which dramatically influence the actual performance of theoretical solutions. Therefore, the purpose of optimization is not only to acquire a higher-quality solution but also to satisfy the specified robustness requirements.

SOLUTION - Robust design optimization method was proposed to reduce the influence of uncertain factors on the stability of hydrodynamic performance. Firstly, Bezier curve was used to parameterize the suction side of the airfoil, and its thickness was controlled by four points, which was then taken as the optimization variables. Secondly, the criterion of robustness was given, and then a robust mathematical model was established. Finally, two objective functions of robust optimization were gained on the basis of uncertainty analysis with surrogate model. Combined with MOGA multi-objective genetic algorithm provided by modeFRONTIER, a robust optimal solution with better hydrodynamic characteristics was obtained. 

BENEFITS - The results showed that compared with original case, the thickness near trailing edge altered more smoothly, the resistance and surface wave intensity were obviously decreased, and the maximum reduction of drag-lift ratio and wake unevenness were 6.89% and 25.04% respectively, which contributed to the improvement of wake quality. This robust optimization method featured with short optimization cycle and low cost has a better balance between the hydrodynamic characteristics and the robustness. It can be used in the optimization of airfoils as well as the stability optimization of other hydraulic machinery under uncertainties.