[Abhinav_Nagarajan]

Dear Foamers,
I am simulating a reactor with a weird geometry (please find picture attached), with a diffuser section connected to a rectangular duct.
Simulation conditions:
Inlet velocity: 0.55m/s
Reynold's number(at inlet): 1161

The issue: The centerline velocity decreases along the length of the duct, basically the centreline decelerates as it passes through the rectangular duct, whereas it should increase. Therefore, the results are not validated as per existing analytical models.

I am unable to figure where the problem lies, since I have a mesh with no errors. Could you please help me out with this issue. I have attached my fvschemes, fvsolution and the reactor snip along with the velocity vs length profile.

Thank you!

[SHUBHAM9595]

Hi Abhinav,

Unfortunately, I've to disagree with you

I am unable to figure where the problem lies, since I have a mesh with no errors

As you can clearly see in the output of checkMesh, we do have some issues with the grid.

...........................

    Cell determinant (wellposedness) : minimum: 0.108244 average: 7.7354
    Cell determinant check OK.
 ***Concave cells (using face planes) found, number of cells: 32
  <<Writing 32 concave cells to set concaveCells
    Face interpolation weight : minimum: 0.114561 average: 0.498237
    Face interpolation weight check OK.
    Face volume ratio : minimum: 0.0876268 average: 0.992505
    Face volume ratio check OK.

Failed 1 mesh checks.

End

U can visualize this SPECIFIC set (concaveCells) in paraview with something likw ....

foamToVTK -cellSets concaveCells -time 0

and then get an idea where exactly u need to make changes within the domain...