Help! Free waterjet simulation

Annie

Hi, everyone!

I am trying to use CFD and am inexperienced with it. Can anyone with experience in modelling free water jets help me?

I am using CFX5.4.1 to model a axisymmetry water jet after it coming through a very fine nozzle(1 mm). I am going to know the jet's velocity and pressure distribution when it sprays in air atmosphere. The jet got high velocity (900m/s) and pressure (350 MPa).

I use a three-dimensional computational domain. i.e. a vertical 10mm diameter cylinder of length 100 mm. The water jet enters domain on the top of cylinder.

This problem is considered as steady state, highly turbulent and two-phase (air and water). The air is assumed to form a continuous phase and the water is to form a disperse phase.

At jet_inlet boundary, I put same velocity but different volume fraction for tow phase, i.e. water_speed= 900m/s, water_vf=1, air_speed =900 m/s, air_vf=0

I set the initial phase distribution to air 100% and water 0%.

I could not get a convergence solution of my model. What are the reasons?

Could I use multiphase model in this simulation? I know that CFX5 does not support continuous-continuous multiphase calculations. But the two phases I got here are both continuous.

Please help me! Thanks in advance.