Hydrodynamic Characteristics of a Helicopter Ditching on Different Positions of Wavy Water

The present study numerically explored the hydrodynamic characteristics of a helicopter model experiencing guided ditching on wavy water. The air-water two-phase flow was computed by solving unsteady incompressible Reynolds-averaged Navier-Stokes equations enclosed by the k-omega shear stress transport turbulence model. The effect of water-entry position of the wave, viz., crest, falling, rising and trough, on the ditching behavior of a helicopter was assessed under different initial pitching angles. Results show that the hydrodynamic characteristics of the helicopter ditching on wavy water is significantly different from ditching on still water. Ditching on the crest of a wave illustrates the best performance in terms of angular, vertical, and horizontal acceleration that results from a skiing motion to minimize the hydrodynamic overload. On the other hand, ditching on trough will result in the most severe overload because the largest impacting area of the helicopter provides a relatively large reactive force to decelerate the descending motion of the helicopter. Within the tested angles, ditching on crest is always the best option. The initial pitching angle is influential to the rising and trough cases, such that a smaller pitching angle is suggested for ditching a rising wave, and alternatively, a larger angle is suitable for trough.