Good morning, I'm modeling the turbulence flow inside a reactor. I use the boundary condition "velocity inlet" for the inlet surface while for the outlet surfaces I use "Pressure outlet".Now I want to verify if a specific head of a pump is enough to guarantee the flow of the fluid inside the reactor. What boundary conditions I have to specify for the inlet and outlet surface.Is it better to define an initial pressure? I hope you will help me!!!Thank you!!!

I suggest you should use 'pressure inlet' BC. You already know head of the pump. Please convert it to N/m2. If you're sure that there is no backflow though outlet(s) of the reactor then try using 'outflow' BC for outlet. I hope this will work.