[martyn88]

Hello Foamers,

I am having trouble getting a simulation to run and the main problem appears to be at my inlet. It is basically a converging diverging nozzle poking into a freestream and I am defining a inlet flow rate at the nozzle and a small coflow above the nozzle.

I have attempted to use the flowrateinletvelocity condition but it appears to not be prescribing a velocity at the inlet, regardless of how high I set the mass flow rate. I have initialised my internal field velocity at 2m/s so all thats happening is the internal field is leaving the domain and being replaced by zero velocity air.

Here is my mesh at the inlet:

ICEMmesh.jpg


I also used a fixed value velocity at the inlet to compare and found the following:

For flowrateinletvelocity:

- what is wrong with my inlet patch? It seems like it is not properly connected or something, like it is blocked.
- why does mass flow rate BC cause no apparent inlet velocity to be defined?
- why is the temperature not propagating (or doing so extremely slowly)?

massflowrate50_U.jpg

massflowrate50_T.jpg


Fixed value velocity:

- when fixed value velocity is defined, flow is developing, but way too slowly. 20 m/s inlet U should have travelled 4 metres (8 nozzle lengths) in 0.2 secs, however it has not even made the nozzle exit (travelled 10cm max)

fixedvalue20_U.jpg

fixedvalue20_T.jpg

Please find attached the checkMesh log

Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 617519
faces: 1789130
internal faces: 1727110
cells: 586040
boundary patches: 8
point zones: 0
face zones: 1
cell zones: 1

Overall number of cells of each type:
hexahedra: 586040
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 0

Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface topology
CYCLIC_1 23366 23821 ok (non-closed singly connected)
CYCLIC_2 23366 23821 ok (non-closed singly connected)
FREESTREAM_BOTTOM 812 870 ok (non-closed singly connected)
FREESTREAM_TOP 7784 8091 ok (non-closed singly connected)
INLET 588 631 ok (non-closed singly connected)
INLET_COFLOW 1372 1450 ok (non-closed singly connected)
NOZZLEWALL 2772 2900 ok (non-closed singly connected)
OUTLET 1960 2052 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-464.1161237 -5.05255153e-19 -1.064772188e-12) (1143 274.3200073 193.9735322)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-3.79177398008e-17 -5.85917462408e-14 4.36207997116e-14) OK.
Max cell openness = 2.92805429189e-16 OK.
Max aspect ratio = 11.1240642867 OK.
Minumum face area = 0.330563016672. Maximum face area = 36.1242486469. Face area magnitudes OK.
Min volume = 1.56100489244. Max volume = 165.81880705. Total volume = 36706377.576. Cell volumes OK.
Mesh non-orthogonality Max: 48.8035890294 average: 8.6477627171
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.859011733412 OK.
Coupled point location match (average 0) OK.

Mesh OK.


Does anyone have any ideas why it is acting so strangely at the inlet?

Thanks