The effect of boundary conditions and ribs on the total radiation efficiency of submerged plates

The radiation efficiency of a plate submerged in water is often used as a basis on which to represent the sound radiation from more complex underwater structures. The boundary conditions and stiffening ribs are known to have a significant influence on sound radiation from a plate for frequencies below the critical frequency. A numerical and analytical investigation of the radiation efficiency of submerged plates is presented in this paper. The total radiation efficiency is developed from a numerical finite element model using ANSYS by averaging the efficiency due to three point force positions. The effect of boundary conditions and ribs on the total radiation efficiency is discussed in detail. The basic results are compared with those from a numerical boundary element model using SYSNOISE and an analytical engineering formula. Excellent agreement is obtained between the two numerical methods. The analytical results agree well with the numerical ones over the whole frequency range except for some small regions.