Semi-analytical study on liquid sloshing in a rectangular tank with different horizontal elastic baffles subjected to combined surge and pitch excitations

In this paper, a semi-analytical fluid–structure interaction model is established for a rectangular tank equipped with a horizontal elastic baffle under combined surge-pitch excitations, considering six typical edge constraint conditions (clamped-clamped, supported-simply supported, clamped-simply supported, simply supported-clamped, clamped-free, and simply supported-free). Based on potential flow theory and the Euler–Bernoulli beam assumption, the governing equations for the coupled baffle-sloshing system are derived using a subdomain division method and eigenfunction expansion, and the model is validated against automatic dynamic incremental nonlinear analysis numerical solutions and experimental data. The effects of baffle width, position, thickness, and boundary constraint type on the coupled natural frequency, free-surface wave height, mid-point deflection, and energy absorption are systematically investigated. The results indicate that baffle geometry effects on liquid sloshing strongly depend on boundary conditions. The sign of surge excitation frequency significantly modulates the response, where in-phase surge-pitch coupling prominently enhances the fluid–structure resonant response, especially for thin baffles in the positive-frequency regime under specific geometric parameters.