fluent internal nozzle flow
 

Hello, I need help setting up the physics for this problem in fluent.

I have a 15 degree conic nozzle which I have created the geometry, and meshed (see attached) and named edges for the inlet and outlet.

Total Pressure = 2.5 MPa
Total Temperature = 2500K
exit mach should be 3.0

here is what I used:

Physics-setup

General
Density-Based Solver : selected because was originally designed for high-speed compressible flows.
Time: Steady
2D Space: Planar

Models
energy equation: on energy equation is coupled to the continuity and momentum equations
Viscous model: inviscid

Materials
Air - Set density to ideal gas

Cell Zone Conditions
Surface_Body Operating pressure set to 0 Pa

Boundary Conditions
inlet: type pressure-inlet, Gauge total pressure:2500000 Pascal, Gauge Total Temperature 2500 K constant
outlet: type pressure-outlet, Gauge total pressure: 0 Pa, 300K

Solution Methods

Formulation:Implicit ,Flux type: Roe-FDS
Spatial Discretization: Least squares cell based
flow
Second order upwind

So... I ran calculation with solution steering, 1000 iterations, flow type supersonic, use fmg initialization


and well it does not look as I had expected. what should I do instead so that I have mach=1 at the inlet, and so that it expands to mach 3 at the exit. the geometry was determined by method of characteristics to do this with the input data.:confused:
Attachment 17434

Attachment 17435

Attachment 17436

re ran with a modified geometry including a convergent seciton... results look more like they should, but is this necessary? :confused:Attachment 17444