Numerical Investigation Of Liquid Sloshing By MPS Method

Liquid sloshing flow is commonly encountered in partially filled tanks subjected to external excitations.Violent liquid sloshing usually leads to local impact pressure on the bulkhead of liquid tanks,which may further result in local breakage of the tank structure.At the same time,moments induced by liquid sloshing can break the global stability of a ship,even capsize the ship in rough conditions.In addition,loads induced by sloshing have been become an important part for safety assessment of liquid carriers.Therefore,it is of practical importance to study the violent sloshing in fields of naval architecture and ocean engineering.Based on our in house meshless particle solver MLParticle-SJTU,liquid sloshing problems are investigated systematically in the aspects of the effect of excitation frequency and filling level,damping effect and physical mechanisms of baffles,sloshing under multiple DOF excitations etc.The thesis can be organized as follows:1.The effect of excitation frequency on liquid sloshingFirstly,liquid sloshing flows in a 2D rectangular tank subjected to harmonic rotational motion under shallow water condition and critical depth condition are simulated to investigate the effect of excitation period on sloshing.Then,sloshing phenomena in a 3D membrane tank subjected to single DOF rolling and single DOF pitching motion are also simulated.The effect of filling level and excitation frequency on impact pressure is parametrically investigated and discussed.In the last,sloshing cases in a rectangular tank for a wide range of rolling frequencies are investigated.The varying pattern of excitation frequency on sloshing moments is obtained.It can be seen that excitation frequency can affect the moments and impact pressure induced by sloshing significantly.The flow field is quite violent when excitation frequency is close to model frequency.2.The damping effect and physical mechanisms of different types of baffles on sloshingFirstly,liquid sloshing in a 2D rectangular tank with vertical and symmetrical horizontal baffle is simulated to analyze the damping effect of baffles with different dimensions and locations.Results show that the damping effect of these two types of baffles are both remarkable and the damping effect becomes more significant when increasing the dimension and height of baffles.In addition,3D liquid sloshing with different types of baffles is also simulated to analyze physical mechanisms of the damping effect.It can be seen that baffles can blockT convection motion and consume kinetic energy of the flow.Vortex and severe fluid collision around the tips of baffles may also cause energy dissipation.The resonant frequency would be changed due to the presence of baffles.3.Liquid sloshing under multiple DOF excitationFirstly,liquid sloshing in a 2D rectangular tank under the coupling motion of pitching and surging is simulated to investigate the effect of phase lag on sloshing amplitude between these two excited motions.Then 3D liquid sloshing is simulated to study the effect of phase lag between rolling and pitching motion.At last,sloshing in a tank with six DOF motion is simulated.Results show that the amplitude and impact pressure can be larger due to the coupling effect of multiple DOF excitation,which may result in the breakage of tank wall.However,the amplitude of sloshing can be reduced by setting reasonable phase lags among different DOF excitations.