ask help on valve flow simulation(3D modelling)

Anna

Hello, anybody can give me hints on a flow control valve simulation? I created a 3D modelling, a big up oil container and a small valve at bottom. Here are some boundary conditions defined: 1 unsteady laminar flow, under atmospheric pressure operation condition, only gravity causes the flow; 2 one phase fluid, because it will work on unpredictable temperature, so I set energy in.

Because I am a newer on FLUENT, so all the time I got rubbish results. So what should be correct settings? I did setting on Define-model,energy, viscous ; material; operation condition; boundary conditions; solver-controls; solution; initilize and iterate.

Sometimes the iterate doesn't run or just appears one convergence, 0; sometimes the result on pressure is decreasing along the gravity direction. And where is the correct reference pressure location?

Please tell me what shall I do on this modelling, I really need your kind help.