Numerical Comparison of the Ground-Effect Aerodynamics of the Fuselage Body Flap as a Lift-Enhancement Device at Varying Ground Heights

Wing-in-Ground (WIG) effect craft operate in close proximity to the ground, where aerodynamic performance is strongly influenced by ground-effect phenomena. Improving lift characteristics while limiting drag is therefore important for enhancing the efficiency and controllability of such vehicles. This study investigates the aerodynamic effects of a body flap mounted at the rear of a fuselage operating under WIG conditions. Although the body flap was originally designed as a hydrodynamic braking device, its aerodynamic influence in the undeployed configuration has received limited attention. Computational fluid dynamics simulations were performed to compare the aerodynamic performance of a fuselage with and without a body flap across varying ground heights. Lift, drag, and lift-to-drag ratio were evaluated, and flow-field characteristics were examined to support the force trends. The results show that the inclusion of a body flap leads to increased lift across the ground-effect region with only minor changes in drag, resulting in improved aerodynamic efficiency compared to the baseline configuration. These findings suggest that the body flap may provide aerodynamic benefits in addition to its hydrodynamic braking function. Experimental validation is recommended as future work to further assess the aerodynamic performance under realistic operating conditions.