An Experimental Study On The Interaction Between Water Waves And Submerged Disk

The hydrodynamic model experiment of submerged disk under the action of solitary wave and regular wave was carried out in an offshore tsunami wave basin.A set of built-in multi-component wave force synchronous measurement system is established for the plexiglass disk model with a diameter of 1.2m and a thickness of 0.1m The horizontal force,vertical force and overturning moment acting on the disk can be obtained without affecting the wave surface measurement.Physical experiments of interaction between the water waves and the submerged disk under different water depths,different submerging depths and different wave heights are carried out.The time series of the wave load on the disk and the wave elevation are obtained.Meanwhile,the relationship between the dimensionless wave load on the disk and the relative wave height is analyzed.According to the extreme characteristics of vertical force,horizontal force and overturning moment under the action of solitary wave,the change process of wave load under the condition of complete submerging can be divided into five typical stages: the uplift force is formed in the early stage of solitary wave action and reaches the first peak value;When the wave crest approaches the center of the disk,it forms the extreme value of the forward horizontal force.When the wave crest leaves the center of the disk,the horizontal force in the reverse wave direction reaches an extreme value and the downward force gradually recovers from the extreme value point to the upward force.When the wave crest leaves the edge of the disk,the lifting force reaches the second extreme point.When the wave crest moves further away from the disk,the hydrodynamic load returns to zero.The vertical wave load on the disk is closely related to the submerging depth.When the disk is completely submerged,the vertical force on the disk has two extreme values,while the vertical force on the disk has only one extreme value and its absolute value is greater than the maximum value of the lifting force.When the upper surface of the disk is located at the undisturbed water surface(critical submerging condition),the upward vertical force has only one extreme value,which is due to partial buoyancy loss caused by local trough of the wave surface when the solitary wave leaves the disk,which inhibits the development of the upward lifting force,and the peak value of the upward lifting force is greater than the absolute value of the downward vertical force.When the disk is partially submerged,the buoyancy increases during the wave surface lifting process,making the peak value of the lifting force significantly increase.Relative submerging depth and relative wave height have influence on dimensionless wave load.When the submerging depth is small,the variation rule of dimensionless wave load is more complicated because the solitary wave will break above the disk.Under the action of regular waves,the ratio of disk diameter to wavelength(relative diameter)is between 0.31 and 0.67,and the wave loading process of submerged disk model has obvious periodicity.Under the condition of complete submerging,the time course lines of vertical wave force and horizontal wave force show good periodicity.The peaks and valleys are basically symmetrical,and the phase of the former is slightly ahead.The peaks and valleys of the moment time course line are obviously asymmetrical,and the time course of the head-up moment(positive value)is obviously larger than the time course of the head-down course.For the critical submerged state,in one wave period,the peak value of vertical force is much smaller than the valley value,that is,the vertical force is basically downward.Vertical force and horizontal force are basically in phase.The time course of head-up moment(positive value)is smaller than that of head-down moment.The reason for the significant reduction of lifting force is that some disks are exposed to the water surface and some buoyancy is lost.Under the condition of incomplete submerging,the change of the water line of the disk in the rule leads to the increase of the buoyancy effect on the disk in the wave crest influence stage,which increases the lifting force,but is still less than the extreme value of the downward wave force.The time series of head-up moment(positive value)is also smaller than that of head-down moment.Generally speaking,under the condition of given wave period and water depth,the dimensionless wave force and moment decrease with the increase of wave height.The main reason is that the wave breaking near the disk increases with the increase of wave height,resulting in loss of energy.