Speaker 2 :Yeunwoo Cho(Korea Advanced Institute of Science and Technology)Date & Time: October 15th (Fri.), 2021 / 10:50-11:30PM (Tokyo (JST))Title: Hysteresis phenomena in gravity-capillary waves on deep water generated by a moving two-dimensional/three-dimensional air-blowing/air-suction forcingAbstract: Hysteresis phenomena in forced gravity-capillary waves on deep water where the minimum phase speed c_min = 23cm/s are experimentally investigated. Four kinds of forcings are considered: two-dimensional/three-dimensional air-blowing/air-suction forcings. For a still-water initial condition, as the forcing speed increases from zero towards a certain target speed (U), there exists a certain critical speed (U_crit) at which the transition from linear to nonlinear states occurs. When U < U_crit, steady linear localized waves are observed (state I). When U_crit < U < c_min, steady nonlinear localized waves, including steep gravity-capillary solitary waves, are observed (state II). When U is nearly equal to c_min, periodic shedding phenomena of nonlinear localized depressions are observed (state III). When U > c_min, steady linear non-local waves are observed (state IV). Next, with these state-II, III and IV waves as new initial conditions, as the forcing speed is decreased towards a certain target speed (U_final), a certain critical speed (U_crit_2) is identified at which the transition from nonlinear to linear states occurs. When U_crit_2 < U_final < U_crit, relatively steeper steady nonlinear localized waves, including steeper gravity-capillary solitary waves, are observed. When U_final < U_crit_2 , linear state-I waves are observed. These are hysteresis phenomena, which show jump transitions from linear to nonlinear states and from nonlinear to linear states at two different critical speeds. For air-blowing cases, experimental results are compared with simulation results based on a theoretical model equation. They agree with each other very well except that the experimentally identified critical speed (U_crit_2) is different from the theoretically predicted one. *This abstract is excerpted from Park & Cho (JFM, 2020, vol. 885, A20).