A Study on the Effects of Small Bottom Stiffeners on Sloshing Resonance

Abstract

Internal structures of the liquid cargo tanks, such as horizontal girders and small longitudinal stiffeners may affect sloshing behaviors in lower filling conditions. Since the assessment of sloshing load in shallow liquid conditions is required by the classification societies for the structural dimensioning, the present study investigates the impact of the tiny bottom stiffeners on the resonance behaviors of the sloshing. For this purpose, sloshing resonant period and damping in rectangular tanks were obtained from sloshing free oscillation tests using a clean tank and a tank with small bottom stiffeners. Both experimental study and numerical simulations based on Moving Particle Semi-implicit (MPS) method were carried out. Initially, the numerical results are validated. After that, a series of simulations were performed considering different combinations of stiffeners sizes and a range of filling ratio that included very shallow liquid condition. The results show that in clean tanks, the resonant period obtained numerically agreed well with analytical ones. The stiffeners on the bottom increase resonant period, but its value is slightly lower than the analytically obtained considering the filling height as the difference between the real filling height and stiffener height. Finally, two distinct behaviors regarding the damping were identified.