Its a pipe around 50 cm length vertically mounted. Top end is open for air Inlet and bottom end closed with 40 cm diameter of half sphere.
I make few holes(all are same diameter and place in same distance) on half sphere for air outlet. I want to find out the velocity at certain distance with respect to holes angle of outgoing air.
In Boundary Condition I have 2 parameters.
Total air flow 2000 m3/h (mass flow rate) and static pressure 45 pa constant.
After simulating in fluent I will get different velocities from every holes. I have to achieved same velocity from all holes.
But I didn't understand if all holes are in symmetry(same diameter) and flow also constant then why the values different.
Now I am using K- epsilon model with Enhanced wall function
If you are solving an incompressible flow model, without a constraint on the mass flow rate, the solution with multiple outlets can be unique. The continuity equation can be satisfied even if you do not have the same flow rate on all the outlet.
Fluent should equally distribute by default the mass flow rate between outles http://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node247.htm
Check if the geometry is correct and if the convergence to a steady state is really achieved.
Not sure whether I understand the issue correctly.
If there are only few holes and their number is well known, why you cannot split the overall massflow rate in equal amounts and assign it equally to all of them? In the result the velocities from all different holes should be (almost) equal.
With a kind of pressure boundary condition it could result in different velocities due to hydrostatic pressure differences. Since the holes are placed on a half-sphere surface, the hydrostatic pressure could be different for different air outlets.
Another point is, that on a coarse mesh there could arise discretization differences for the resulting injection velocities. The solver should obey to the specified mass flow rate for the given discretization/triangulation of the small holes. If the mesh is still coarse, than the velocity calculates from the specified mass flow rate divided by density and cross sectional area of the discretized hole. The latter is a sum over the area of the mesh cells being used to mesh the hole. This can vary from hole to hole depending on the meshing method and mesh generator which you use. In consequence the injected mass flow rate and air density would be equal, but the injection velocity would be different, since the represented cross-sectional area of the holes on your given mesh might be different.
Hopefully that helps.
Regards,
Thomas Frank.
- Badges
- Science topic