Fluid-structure interaction via boundary operator method

This paper is an examination of a simple fluid-structure interaction problem in which a technique for solving time dependent boundary condition problems, the Boundary Operator Method (BOM), is used to gain further insight into fluid-structure response characteristics. The fluid-structure system consists of a compressible liquid having an acoustic pump at one boundary and a spring mass at the other boundary. The response of the spring mass as a result of the acoustic pulsations of the pump is the quantity of interest. This simple model closely represents a PWR core support barrel when excited by pressure waves due to circulating pump pulsations. The general solution of the pressure via the BOM is obtained as a function of the unknown spring mass response. This pressure is evaluated spatially at the spring mass end and the resulting equation of motion for the spring mass is found to be an integral-differential equation. Formulating the solution of the integral differential equation for a harmonic pump pulsation one obtains a normalized displacement of the spring mass as a function of three parameters. These parameters consist of a fluid to structure mass ratio, forcing frequency to uncoupled liquid natural frequency, and a ratio of forcing frequency to uncoupled structural frequency. A study is performed to determine the influence of the three parameters on the structural response.