[npuh002]

Hi, I'm trying to model the formation of a jet in FLUENT. The jet is formed at high pressure by forcing through a small orifice. As a result, there is a reduction in diameter. In this case, the reduction is smooth. I have used an axisymmetric model to do this, with pressure boundary conditions at the inlet and the outlet (10 MPa and 0 MPa respectively). I have included the energy equation and viscous heating as well as the temperature-dependent viscosity of the fluid I am simulating, glycerol. The results exhibit a loss of energy between the inlet and the outlet (kinetic + heat) even though the wall flux is set to 0 (which should make it adiabatic). The speed at the outlet does not match the experimental results (50% less in volumetric jet speed). Interestingly, if I solve the same model in 2D planar (NOT axisymmetric) and a symmetry boundary condition where there was an axis boundary condition, the simulation results match (error of 5% in volumetric jet speed) and the energy balance is OK. Is there a possibility of energy being lost within the axisymmetric system? Are there further models I should be including in the flow? I have removed the turbulence model as it only lowered the output jet speed. I have also increased everything to second order. Your help would be much appreciated. P.S. I'm a student at the University of Auckland