A Study of the Response of Coupled Liquid Flow-Structural Systems Subjected to Periodic Disturbances

Abstract

The dynamic response of liquid flow systems may be grossly affected by motion of the system’s structural supports. Pressure and flow perturbations within the flow system provide the driving forces for the structural supports, and the resulting motion induces further pressure and flow perturbations. In this type of closed-loop system, instabilities are possible. Analysis techniques are developed which enable the analyst to formulate distributed parameter, nonlinear solutions to unsteady flow problems including structural motion. These techniques are based on plane wave theory and require the use of a digital computer. For sinusoidal periodic inputs of small amplitudes, closed-form mathematical solutions are possible if nonlinearities are linearized, and these solutions are carried out. Examples show that resonance points and peak-to-peak pressure amplitudes may be very sensitive to structural properties of the supporting structure. Analytical results obtained with the closed-form linearized model and the nonlinear digital model are compared. It is also shown that the closed-form linearized model gives results which compare favorably with the nonlinear model for the case of sinusoidal inputs, but cannot be applied if the input perturbations are nonsinusoidal or are sufficiently large or if wave shapes are to be computed. Experimental results are shown to agree well with theoretical calculations.