Design Optimization Method of Multi-Element Flaps for High-lift Devices Considering Ground Effect

For a WIGE (Wing-in-Ground-effect) craft, the ground effect has important influence on its takeoff performance during the whole takeoff process, hence the ground effect must be taken into account in the aerodynamic shape design of the WIGE crafts' high-lift device. This paper proposes a surrogate-based design optimization method for a high-lift device with multi-element flaps, through considering the ground effect in the aerodynamic performance evaluation of the high-lift device during the optimization, the present method is more suitable for the WIGE crafts than the conventional high-lift design method without consideration of ground effects. Using the RANS (Reynolds-Averaged Naiver-Stokes) equation solver and the efficient surrogate-based optimizer (an in-house code: SurroOpt), the design optimization of a WIGE craft's multi-element flaps is carried out. Taking the double flap high-lift device as an example, with NACA23012 airfoil as baseline airfoil, the optimization is carried out by using 56 design variables, with the maximum lift coefficient as objective. The optimized double flap high-lift device shows a high takeoff lift coefficient of 2.808 under the ground effects, which verifies the effectiveness of the optimization method developed in this article.