This paper presents a parametric investigation of the free vibration characteristics of an auxetic honeycomb sandwich plate mounted at the wall of a liquid tank. Frostig's second model is utilized in the core, while first-order shear deformation theory (FSDT) is applied to the face sheets. The honeycomb core is homogenized using one of the newest revised models (Tornabene's model), and the fluid is assumed to be ideal. The governing equations of motion are derived using Hamilton's principle and solved using the Galerkin method. Present solution method, honeycomb core homogenization formula, and mathematical framework for the fluid-sandwich plate interaction are verified using 3D Finite Element Analysis (FEA). Finally, the wet fundamental frequency is investigated with geometric parameters such as the ratio of tank dimensions to the plate length, fluid height from the plate's bottom edge, plate location at the tank wall, and honeycomb cell geometry. According to the results of this study, the thickness of the face sheet and the cell wall enhance the wet fundamental frequency, while the cell aspect ratio decreases it.
