1D-3D co-simulation pipe resonance induced by cavitating vortex shedding

Abstract Hydraulic systems may experience excitation caused by complex flow patterns within various components of the system. A computational effective way to predict the interaction between the hydraulic system and the excitation source is to conduct a co-simulation using two independent simulation codes. One code models the fluid pipe system using a one-dimensional compressible approach, while the other code simulates the excitation source with a three-dimensional model. Recognized as a standard communication protocol for linking two simulation codes that solve a system of ordinary differential equations, the Functional Mockup Interface, FMI, protocol has been implemented in SIMSEN to couple with the Ansys CFX software solution. Localized hydrodynamic instabilities including cavitation are prone to interact with the entire system. A cavitating case study has been investigated to assess robustness and accuracy of the co-simulation performed with the FMI protocol. The case study consists in a straight pipe connecting two constant pressure tanks with a bluff body placed at 3/4 of the pipe length. The vortex shedding is the excitation which frequency is proportional to the flow velocity. Measurements are available for resonant and non-resonant conditions in cavitating and free cavitating flow regimes. Co-simulations are performed between SIMSEN 1D model of the pipe and a pseudo 3D CFX model of the bluff body, reduced to one cell in the width direction. The comparisons with measurements show good agreement despite the pseudo 3D approach to simulate bluff body-induced excitation. This demonstrates that this approach is valid to address complex unsteady, compressible and cavitating flow phenomena.