Steady-State and Unsteady Simulations of a High Velocity Jet Into a Venturi Shaped Pipe

Abstract

A jet pump consists mainly of a convergent-divergent Venturi shaped duct where a primary stream is applied with the role of entraining a secondary jet. Due to their simple and reliable concept, jet pumps are used in miscellaneous applications. Performance optimization of a jet pump has to be performed for various operation conditions. Thus, numerically robust and cheap models, able to predict accurately the performance parameters of such devices are necessary. Reynolds Averaged Navier-Stokes based formulations are computationally efficient to predict the performance of a jet pump. However, these simulations rely on turbulence closure coefficients, which need to be validated with experimental observations. Large Eddy Simulation solves the most energetic structures in the flow field and it can be used to capture the flow dynamics. On the experimental side, confined geometries challenge the investigation capabilities to capture the flow field accurately and in all the details. The flow field in the jet pump is investigated using Large Eddy Simulation approach and a steady state Reynolds Averaged Navier-Stokes formulation. The flow field solutions obtained with the two numerical tools are compared. A reasonable agreement for the velocity and pressure contours could be achieved. However, the turbulence kinetic energy distribution and the entrained mass flow rate are predicted to be distinct. The difference in entrained mass flow rate leads to differences in jet pump efficiency estimation.