An Experimental Study On The Performance Of Porous Structure Device In Sloshing Tanks

Tank sloshing is a ship or floating structure with liquid compartments in which large and complex fluid movements occur under the excitation of natural environmental loading factors.Tank sloshing has a great impact on the tank structure,resulting in serious consequences such as structural damage.In order to reduce the sloshing phenomenon of liquid tank,it is necessary to study effective methods to prevent sloshing in liquid tank.In this paper,a kind of porous box structure device is proposed,which is composed of horizontal and vertical plates with holes.Through measured wave height in tank change data,combined with the maximum amplitude curves,wavelet analysis and image analysis method for analysis of hydrodynamic phenomenon in a tank,given porous box the effect of shaking device which has the best resistance sway opening conditions,for different tank flap about scene in practical ocean engineering provides a new thought of resistance shaking device.In this paper,the method of physical model experiment is mainly used to study the hydrodynamic characteristics of the oscillating wave,and it is found that the sloshing wave in the liquid tank has three amplitude changes with the change of frequency within the range of first-order natural frequency.When the excitation frequency is 0.91 f₁～1.09 f₁（f₁=0.55Hz is the natural frequency）.The sloshing wave in the liquid tank has the most drastic change,with a large amplitude and a strong overall nonlinearity,indicating that it is the frequency interval that needs to be focused on in the research.Combined with the image analysis,it is found that the standing wave and traveling wave are the main reasons for the large amplitude elevation in the liquid tank.In order to show that the porous box anti-vibration device has better damping effect,the maximum amplitude of the device is the smallest,and the nonlinearity of the oscillating wave can be significantly reduced by comparing the structure with the single-hole horizontal plate and the single-hole vertical plate.In order to obtain the optimum opening parameters of porous box structure,it is found through experiments that the opening ratio of vertical plate has little influence on its anti-sway ability,and the opening ratio of lath hole with20%porosity has the best anti-sway effect.According to the analysis of wavelet transform,it is found that the amplitude of the energy spectrum of each time history curve can be obtained by the device by suppressing the first and second natural frequencies（f₁and f₂）in the liquid chamber,which can reduce the amplitude elevation and liquid nonlinearity.In order to explore the influence of excitation conditions on the device,the anti-swing ability of the porous structure device under different excitation conditions was studied experimentally,and it was found that the larger rolling Angle would significantly weaken the anti-swing effect of the porous box.However,the elevation change of water depth in the tank has a great randomness of influence on the maximum amplitude variation rule of the oscillation wave.The device still has a good oscillation reduction effect under the condition of H/L=0.130,which indicates that the device has a good oscillation reduction effect in most tank water depth conditions.By virtue of the size of the working conditions of physical model experiment design is always limited,in order to enhance the representative of the results,this paper on the basis of building a machine learning model based on KNN algorithm,the experiment condition through input conditions predict better the hole shape and opening rate of porous structure and the result is consistent with the physical model experiment analysis conclusions,The slat hole with 20%porosity has the best anti-vibration effect,which proves that the device has the characteristics of universality.In order to improve the anti-vibration performance of the porous box anti-vibration device,the experiment focuses on the improvement effect of the porous media structure on the anti-vibration ability of the device.The results show that the addition of porous media can make the peak value of the maximum amplitude curve move back,and the energy in the natural frequency and low frequency condition is reduced by about 38%when adding four layers of flexible plastic sheet structure in the porous box,which is a better scheme.Finally,this paper explores the influence of the installation position of the anti-vibration device.It is found that when the arrangement conditions permit,the anti-vibration device of the porous box will have the best anti-vibration effect when it is placed in the central position of the bottom of the tank.At this time,compared with the result obtained when it is placed on the side wall,the height of the maximum amplitude curve decreases,and the resonance frequency of the tank is advanced.This conclusion provides more design ideas for the application scenarios of box type anti-vibration device in practical engineering.