The main purpose is to develop an efficient yet accurate coupling method integrating Navier-Stokes (N-S) and potential flow solvers with a free wake model. In order to improve the efficiency while maintaining a good accuracy of the method, mid- to farfield computational domain is computed by the potential solvers with the free wake model, whereas the N-S solver is used to solve near-body viscous flow. The coupling method is applied to simulate vortex dominated flows of delta wing type of innovative control effector (ICE) at high angle of attack. An Efficient global optimization (EGO) framework based on variable-fidelity analysis is used to design control surfaces of the ICE configruation for high aerodynamic performance and good rolling performance. The design results will be included in the manuscript of final paper.