Experimental Study Of Liquid Slamming With Entrapped Air On Elastic Sidewalls

Liquid slamming is a common physical phenomenon that exists in land transportation,aerospace engineering,ship and ocean engineering.When liquid slamming occurs,the free surface will show different physical phenomena or a combination of multiple physical phenomena,such as breaking wave and entrapped air.Liquid slamming is one of the most difficult problems in the field of fluid mechanics due to the complex factors including entrapment effect and hydroelasticity.Physical model experiment is the most reliable method to study liquid slamming.Thus,in this paper,the model experimental platform of liquid slamming in an elastic rectangular tank is built.The image data acquisition system is designed to realize the non-contact measurement of the free surface in the tank.And the slamming pressure and the structural response of the elastic sidewall are obtained through the sensing data acquisition system.The study of the liquid slamming with entrapped air on the elastic sidewalls is mainly carried out in three aspect: the kinematic and dynamic characteristics of liquid slamming and the structural response of the elastic sidewalls.Three problems including the effect of air cavity on the evolution of the free surface during liquid slamming,the temporal and spatial distribution of slamming pressure and structural response with and without air cavity,the effect of air cavity on slamming pressure impulse are investigated.The results show that the air cavity plays likely an air cushion during liquid slamming.Thus,the slamming mode is changed from liquid-direct impact to liquid-indirect impact due to the existence of air cushion.And the impact point is changed due to the existence of the entrapped air.The existence of the air cavity leads to a significant reduction of the maximum slamming pressure and structural stress.But the oscillation of entrapped air significantly increases the duration of the slamming,which causes an increase in the pressure impulse in spatial distribution.Based on Morlet continuous wavelet transform,the energy distribution of slamming pressure and structural response is studied from the perspective of slamming energy,and the time-frequency distribution of energy spectrum of slamming pressure and structural response is obtained.The results show that the energy distribution range of the slamming pressure and the structural response is very wide,and the energy is mainly distributed in high frequency,showing obvious pulse characteristics.And the air cavity plays a cushion effect during the liquid slamming,i.e.,the slamming energy is significantly lower than that of the liquid slamming without entrapped air.