[brunop96]

Hi everyone! I'm trying to simulate the flow over tubes in a bank with heat transfer. I'm using the buoyantBoussinesqPimpleFoam solver for forced convection. I've set the g vector and beta to zero. My question is... Why the velocity is not according with the analytical solution (Vmax = 2 m/s) ? The tubes have transverse and longitudinal pitch equal 2 and diameter 1. The surface temperature is constant, 400K, and the internal field 300K. Inlet velocity 1 m/s and pressure zero gradient, outlet velocity zero gradient and pressure 0, top and bottom slip condition and frontAndBack empty (2D flow).



I think my mesh is OK. According to checkMesh


Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 80996
internal points: 0
faces: 160002
internal faces: 78990
cells: 39832
faces per cell: 6
boundary patches: 5
point zones: 0
face zones: 0
cell zones: 1

Overall number of cells of each type:
hexahedra: 39832
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
frontAndBack 79664 80996 ok (non-closed singly connected)
inlet 148 298 ok (non-closed singly connected)
topAndBottom 476 956 ok (non-closed singly connected)
outlet 148 298 ok (non-closed singly connected)
cylinderWalls 576 1152 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-11 -13 0) (45 13 1)
Mesh has 2 geometric (non-empty/wedge) directions (1 1 0)
Mesh has 2 solution (non-empty) directions (1 1 0)
All edges aligned with or perpendicular to non-empty directions.
Boundary openness (-1.14969e-18 6.86221e-18 -2.93229e-20) OK.
Max cell openness = 2.01764e-16 OK.
Max aspect ratio = 2.31215 OK.
Minimum face area = 0.0011945. Maximum face area = 0.2858. Face area magnitudes OK.
Min volume = 0.0011945. Max volume = 0.05716. Total volume = 1448.94. Cell volumes OK.
Mesh non-orthogonality Max: 41.4806 average: 8.0013
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.661525 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End



The max velocity is calculated by Vmax = (((Transversal pitch/(Transversal pitch - diameter)) * inlet velocity).

Somebody have experienced that problem or something familiar? Any suggestion?



Thank you for your help!!

[tomf]

Hi,

Why would you expect the 2 m/s? It looks like this should only be the case if you have these tubes locked inside a channel? Now you allow the fluid to also flow above or below it. As that area will have lower resistance, more fluid will pass than through the tubes.

Regards,
Tom