A Compressible, Coupled Three-Dimensional/One-Dimensional Flow Solution Method for the Seamless Simulation of Centrifugal Pumps and Their Piping

A compressible finite volume Navier-Stokes flow solver is coupled to a method of characteristics for the seamless turbulent flow simulation of entire pump systems. For the pump, three-dimensional (3D) simulations including cavitating flow conditions are performed, and the piping is treated one-dimensional (1D) by a method of characteristics. Thus, classical boundary conditions at the suction and pressure pipe of the 3D computational domain of the pump are substituted by a two-way coupled 1D piping simulation method. Particular emphasis has been placed on the non-reflecting properties of the 3D-1D coupling interface. For validation, in-house experiments are performed on a low specific speed centrifugal pump in a closed-loop facility. For cavitating flow conditions, excitation on the pump's pressure side by rotor-stator interaction is enhanced over a broad frequency spectrum due to collapsing voids. The suction side piping is shielded by void regions within the blading from the excitation on the pump's pressure side, leading to an acoustic decoupling of the suction side. These experimental observations are reproduced by the new seamless simulation method. In particular, the measured pressure amplitudes are well reproduced for a broad frequency spectrum, at several piping positions, and for a variation of the flow rate and the cavitation intensity. Remaining deviations to experimental data are traced back to the omission of structural compliance and uncertainties regarding the pressure side piping modeling, which will be addressed in future studies.