Experimental observation of gravity-capillary solitary waves generated by a moving air-suction

Gravity-capillary solitary waves are generated by a moving “air-suction” forcing instead of a moving “air-blowing” forcing. The air-suction forcing moves horizontally over the surface of deep water with speeds close to the minimum linear phase speed $c_{\mathrm{min}}=$23cm/s. Three different states are observed according to forcing speed below $c_{\mathrm{min}}$. At relatively low speeds below $c_{\mathrm{min}}$, small-amplitude linear circular depressions are observed, and they move steadily ahead of and along with the moving forcing. As the forcing speed increases close to $c_{\mathrm{min}}$, however, nonlinear 3-D gravity-capillary solitary waves are observed, and they move steadily ahead of and along with the moving forcing. Finally, when the forcing speed is very close to $c_{\mathrm{min}}$, oblique shedding phenomena of 3-D gravity-capillary solitary waves are observed ahead of the moving forcing. We found that all the linear and nonlinear wave patterns generated by the air-suction forcing correspond to those generated by the air-blowing forcing. The main difference is that 3-D gravity-capillary solitary waves are observed “ahead of” the air-suction forcing, whereas the same waves are observed “behind” the air-blowing forcing.