A slot-baffle design used in water treatment tanks previously developed by the authors is used to suppress sloshing effects in an accelerated tank. This new application is another example of the versatility of the slot-baffle design in inducing turbulence in fluid flow systems, which has numerous uses in engineering applications. Large amplitude surface waves in a harmonically excited tank are simulated using a second-order accurate numerical model in OpenFOAM. The verification of the numerical model is performed by comparing the numerical results with existing laboratory measurements, which show a favorable agreement. Various slot configurations are studied in order to evaluate the damping performance during the external excitation of the tank. It is shown that the present design shows an effective dissipation performance in a broad range of oscillation frequencies, while 88% of the internal kinetic energy of the liquid is dissipated over thirty oscillation periods for the resonance case.