having trouble modelling basic convergent water nozzle flow
 

Hi,

Not sure if this is the right place to ask but will explain my issues in case it can be passed onto someone that can help.

I am trying to model a basic convergent water rocket nozzle, however my simulation results are very poor in comparison to manual calculations.

I have created what I believe to be a working mesh and have set the inlet and outlet to be outlet pressure points. I have set the inlet pressure to be 20 bar and the outlet to atmospheric. Is this right? The inlet pressure will decrease with time, however I am unsure how to do this.

Other things I require are the fluid velocity, thrust/ mass flow rate (which can then be used to calculate force?), the pressure and discharge coefficient.

I am quite new to Star so apologies if this seems trivial.

Thanks,

Olli

I'd just replace the inlet with a mass-flow inlet, and monitor the pressure at the inlet, and then increase/decrease mass-flow rate until desired inlet pressure is achieved.