I require some technical help on the cfd of an fsae intake manifold, regarding specifying the boundary conditions. According to flow simulation, specifying outlet boundary condition mean flow is exiting the manifold to that condition. I don't understand why in case of intake manifold most people and solidworks tutorial has specified environmental pressure(101325Pa) at the outlet of runners, as the flow here enters the engine of the car and not atmosphere. Rather env.pressure should be given at the inlet as the flow is entering through the environment considering ambient conditions. I just want to check the pressure loss till the air reaches the engine. And taking the bc's as provided in tutorial( inlet velocity, outlet env.pressure), solver shows pressure at inlet above the ambient pressure! Please help and provide some technical understanding about this!! (As in cfd of c-d nozzle the selection of boundary conditions is straight forward.) I am not doing time dependent transient analysis, but the simple analysis.

Values for boundary conditions in cfd of c-d nozzle-

inlet env.pressure- 101325Pa

mass flow rate- 0.075kg/s (reference max.)

flow simulation works best in one of 2 ways

2 pressures > determine the flow rate

an inlet volume flow rate and a pressure > determine the pressure at the inlet side

you can use outlet volume flow rate but it is not recommended by the developers due to the assumption made about the velocity profile

from a physical perspective, an outlet volume flow rate of your intake at the engine side and then a pressure opening where it meets with the throttle body makes sense to me.

but another way you could think of it is to look at how you will test in your flow bench and just match that.