Heaving motions of a ram wing translating above water

Some high-speed marine vehicles utilize wings operating in the air but in close proximity to the water. At small clearances under the wings, and with augmentation of the incident airflow by front air-based propulsors, water surface deformations can influence the aerodynamic characteristics of such lifting surfaces. A dynamic model is developed in this paper for unsteady forces on a two-dimensional ram wing. The current model is based on the extreme-ground-effect theory for airflow and a linearized potential flow theory for water surface deformations. Parametric results are presented for aerodynamic characteristics of a flat plate, including a static lift coefficient, sensitivity on height, and added mass and damping coefficients in heaving motions. Variable parameters include relative speed, airflow augmentation, and frequency and amplitude of heaving oscillations. The developed method can be applied for more general dynamic modeling of high-speed air-supported marine craft.