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

摘要

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(min) = 23 cm s(-1). Three different states are observed according to forcing speeds below cmin. At relatively low speeds below cmin, 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 cmin, however, nonlinear three-dimensional (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 cmin, 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.