Ground effect on a NACA 4412 airfoil flying above monochromatic water waves in steady wind conditions

Operation of in-ground effect (IGE) aircraft in high sea states presents significant challenges due to the highly transient and destabilized aerodynamic loads encountered, which result from the complex and coupled interactions among aircraft dynamics, wind gusts, and time-dependent wave surfaces. The underlying aerodynamics are studied experimentally in a wind-wave towing tank (14.8 m long × 1.15 m wide × 2.2 m high). A NACA 4412 airfoil of chord length 0.41 m and span 1.10 m is towed with a fixed angle of attack of 6^○. Simultaneous measurements of time-resolved lift, drag, and pitching moment are obtained as the airfoil moves at a constant speed against steady wind and above a train of mechanically generated monochromatic water waves. A comprehensive parametric study is conducted by varying wind speeds from 0 to 9.0 m/s, water wave wavelengths from 0.25 to 2 m, and wave amplitudes from 0.5 to 5 cm. The airfoil's motion is either static or maintained at a constant speed of 2.0 m/s. Three different airfoil heights above the mean water surface are used, each representing cases of strong, intermediate, and negligible ground effects. Preliminary results of this parametric study will be compiled, summarized, and selectively presented.