Sloshing and Swirling in Partially Loaded Prismatic Chamfered Tanks

In this study a sloshing experiment using a partially filled membrane tank model was carried out and compared with numerical simulation. The pressure was measured at 10 points and a load cell measured the longitudinal and transversal forces, under regular and irregular excitation. A 3D finite difference method based solver was used for the numerical simulation. When the prismatic tank length to breadth ratio is near 1, swirling, i.e., liquid free surface’s rotating motion in the tank might occur when the tank is excited near its natural frequency, especially for medium and low tank filling levels. According to the experimental and simulation data, the magnitude of the forces and impact pressures in this situation can be significant and therefore cannot be neglected. Tank designs might use different length to breadth ratios (Lt/Bt) depending on the ship size and number of tanks, so the problem is worth being investigated. The Lt/Bt and the occurrence of swirling was then investigated. The pressure distribution when the swirling occurs is then compared with the 1st mode sloshing pressure distribution, and considerations about the tank safety are inferred.