Research On Liquid Sloshing Dynamics In Flat Cylinder Tanks

Tank vehicles are widely used in road transport of liquid cargoes.While promoting the development of the national economy,they also bring about serious traffic safety problems.It is found that liquid sloshing in partially-filled tanks is one of the most important reasons causing tanker accidents,especially the rollover accidents.Therefore,it is quite necessary to study the dynamic characteristics of liquid sloshing in partiallyfilled tanks.The purpose of this paper is to analyze the dynamic characteristics of liquid slsohing in partially-filled tanks by FLUENT simulation.The main research work are summarized as follows:(1)It was decided by market research that liquid sloshing in flat cylinder tank is the research object in this paper.The cross section of the tank has a radius of 0.86 m;liquid fill level in the cylinder tank changes from 0.1 to 0.9.(2)FLUENT software was used to solve liquid free oscillation in cylindrical tank.During the simulation,the trajectory of the liquid center of mass was recorded.The lateral impact of liquid sloshing on the tank wall and the moment of liquid sloshing around tank's lowest point were also recorded.In order to study the influence of liquid properties on slsohing dynamicas,three different liquid,water,engine oil and glycerol are included,were selected to participate sloshing.FLUENT software was used to simulate liquid free oscillation by setting the initial condition of free liquid surface to be an inclined plane.The initial gradient of free surface is obtained by lateral excitation acting on the tank.It varies from 0.1 to 1,which correspond to a lateral excitation of 0.1 g to 1.0 g on the tank.Therefore,the free oscillation of every kind of liquid includes a combination of a liquid filling ratio of 0.1 to 0.9 and a tilted liquid surface of 0.1 to 1.0.The test of step-independent and the test of grid independence of FLUENT simulation have been studied.In the step-independent test,the simulation step of 0.001 s was determined.In the grid-independent test,the grid size of 0.02 m was determined.(3)Using the data obtained from FLUENT simulation,dynamic characteristics of liquid sloshing are studied.It is found that liquid sloshing has obvious periodici features.Therefore,the characteristics of trajecotry of liquid bulk's center of mass,sloshing frequency,sloshing damping ratio and liquid mass involved in slsohing are studied.The research on featrue of trajectory of liquid bulk's center of mass shows that trajectory of liquid bulk's center of mass can be accurately described by circular arcs and the radius of the circular arc is equal to the distance from the geometric center of liquid mass to the center of the tank when the radius of the circular arc is equal to the free surface level.The study on sloshing frequency shows that under the condition of constant lateral acceleration,sloshing frequency increases with the increasement of liquid filling ratio.Under the condition of constant filling ratio,the influence of acceleration on sloshing frequency is quite small.Under the same liquid filling ratio and lateral excitation,sloshing frequencies for the three liquids are nearly equal to each other.Therefore,liquid sloshing frequency is mainly affected by the filling ratio;the effects of lateral acceleration and type of liquids are quite small and can be neglected.The research on the non-dimensional damping coefficient of liquid sloshing shows that sloshing damping exhibits a strong nonlinear characteristic,which shows a monotone decreasing trend with the extension of simulation time.The damping coefficient can be described as a linear function of time over the 20 s simulation time;the damping coefficient is affected by the type of liquid,the filling ratio,and the lateral acceleration.In general,the higher the viscosity of a liquid,the greater the damping coefficient under the same conditions.When the viscosity of liquid is small(water),the damping coefficient increases with the increase of the filling ratio and the lateral excitation.When the viscosity of liquid is large(oil and glycerin),the damping coefficient varies with the filling ratio,the lateral acceleration has no obvious impact on it.Studies on the quality of liquid involved in the slsohing show that not all the liquid is involved in the slsohing,and the quality of liquid involved in sloshing is affected by the type of liquid,the lateral excitation and the filling ratio.When the liquid viscosity is very small(water),the mass of liquid involved in sloshing tends to decrease monotonously with the increase of liquid filling ratio and the lateral excitation.When the viscosity of liquid is large(glycerin and oil),there is a turn in the curve respect to liquid fill level.The research can provide theoretical basis and data support for the construction of equivalent mechanical model of liquid sloshing and the stability control strategy of liquid tanker vehicles.