From pressure to velocity

Rodrigo Madariaga

Hello CFD Community, whenever I need help, I know I can count on this forum so her goes my question:

I am trying to find the best nozzle for a Oxygen tube. Before I start modifying the nozzle, I am trying to simulate a simple evacuation of oxygen through a pipe. In my experimental facilities, I have the oxygen going through a hose that goes to a manometer and then comes the pipe (3/8in diameter). The manometer reads 40 psi and I havent measured the velocity yet. I made a fluent model of this and in my pressure inlet boundary condition I put the 40 psi in the gauge total pressure. The problem is that when I initialize the solution, the speed starts an 400 m/s wich in my opinion is too much. I cant even start the solution because I know the initial solution is wrong, Does anyone know what is going on? Please help me, thanks.