Experimental Research on Shallow‐Water Sloshing Resonant Frequencies in Rectangular Tanks Under Lateral Regular and Irregular Excitations

Sloshing‐induced loads in the shallow‐water tanks have an important impact on ship stability and structural safety. This study experimentally investigates the kinematic characteristics of shallow‐water sloshing motions in rectangular tanks under regular and irregular lateral excitations. Based on the third‐order nonlinear potential flow theory, the approximate formula of the nonlinear lowest resonance frequency is derived considering the damping effect. Experimental results show that the nonlinear resonance frequency under lateral regular excitations can be accurately predicted by the approximate formula. The power spectral densities of free surface elevations at the tank wall under lateral irregular excitations are presented with different spectral peak frequencies. The results indicate that power spectral density energy is mainly concentrated in the first‐order, third‐order, and fifth‐order natural frequencies of fluid in the rectangular tank.