Numerical Modeling of Fluid Transients with Structural Compliance

This paper presents fluid transients in a pipeline with the sudden opening of a valve using a network flow solver based on the finite-volume method. There is entrapped air downstream of the valve. The mathematical model is formulated by integrating the flow equations in the liquid (water) zone and compressibility of the entrapped air and the structural deformation of the pipe. An earlier study by the authors shows a good agreement of computed results using the rigid pipe assumption with the experimental data when the percentage of entrapped air is reasonably high (about 50%). However, as the pressure amplitudes go higher when there is a relatively low volume of entrapped air present, the computed results differ from experimental data both in the amplitude of the pressure oscillations and corresponding frequencies. The use of structural deformation modeling coupled with the fluid dynamics problem reduces the difference for much better comparisons with the experimental data.