Inlet Boundary Conditions ?

[timsefton]

I'm modeling a simple nozell to investigate an air amplification scheme.  The input to the nozell is compressed air at about 100 PSI - I'm not sure what the best type of load to use for this - the fan surface doesn't seem to work well - If I use the Surface Pressure / Traction object - not sure which option to use - Static pressure or Total Pressure or other, like traction - can someone explain which of these options would work best for understanding resulting velocity and pressure out the end of the nozzel, and what traction pressure is ?

 Thanks

Tim

ps:  here is a cross section of the model to show you inputs and outputs - red is input, both front and back of nozzel are inlet / outlets with no other constraints.

[Joey.X · Accepted solution]

For this internal flow, same physical problem can be modelled either following two ways with the speficied BCs and the ways of validating result.

(a) Spcify Inlet pressure +outlet pressure, validate result at flow rate (or velocity)

(b) Specify inlet velocity (or flowrate) + outlet pressure(or inlet/outlet BC), validate average pressure drop from inlet to outlet

Numerically (b) is stable than (a), and one of the special case is setting outlet pressure=0 (or set inlet/outlet BC). 

It appears that you have convergence issue according your posted image, I suggest that you change your modelling to (b) and make sure the mesh is good condition.