Frequency response of rectangular plate structures in contact with fluid subjected to harmonic point excitation force

• Frequency response of plate structures in contact with fluid is studied.
• Applied procedure covers thin and thick plates and stiffened panels with various framings.
• Assumed mode method is utilized for the natural vibration analysis.
• Mode superposition method is applied for frequency response calculation.
• Potential theory is adopted for the added mass assessment.
• The method gives very accurate results compared with general purpose FEA software.

Numerical procedure for the forced vibration analysis of bottom and vertical rectangular plate structures in contact with fluid, subjected to internal point harmonic excitation force is developed. The procedure is based on the assumed mode method for free vibration calculation and mode superposition method for forced vibration analysis. Structural model covers Mindlin rectangular plates and stiffened panels. Lagrange's equation of motion is utilized to formulate the eigenvalue problem taking into account potential and kinetic energies of a plate and reinforcements, and fluid kinetic energy which is calculated according to potential flow theory, respectively. From the boundary conditions for the fluid and structure the fluid velocity potential is derived and it is utilized for the calculation of added mass using the assumed modes. The developed theoretical model and in-house code are verified with extensive numerical examples related to forced vibration of bare plates and stiffened panels in contact with different fluid domains. Comparisons of the results with those obtained by a general purpose finite element (FE) software confirmed high accuracy of the presented numerical procedure.