drops are moving against gravity with my mesh
/edit: since my first description was to confusing, i now updated the first post. now with pictures and even with downloadable case file. thank you all for your support!
3 drops are initialised at rest at different positions over a structured surface in a 3D case without gravity http://dl.dropbox.com/u/29343553/ope...Screenshot.png >> depending on initialising-position: 1 is rising (right drop), 1 is at rest (middle drop), 1 is falling (left drop) http://dl.dropbox.com/u/29343553/ope...reenshot-1.png details: - 3D case, cubic domain, 1 bottom patch with structures on it, 5 ambient patches - boundary conditions: see below - drops = phase1 = water, surounding = phase2 = air - interFoam solver - gravity g is set to 0 - drops initialised at rest with 0.8mm radius in 2mm height - cells per radius: 6 - only hexaedrons - mesh created in icem cfd, imported via fluent3DMeshToFoam - checkMesh: see below casefile download: http://dl.dropbox.com/u/29343553/ope...sHappen.tar.gz BCs for U: Quote:
Quote:
Quote:
Quote:
|
happens also with more correctors:
Quote:
Quote:
Quote:
|
anyone any idea why this might happen?
|
;) i guess ur problem is in boundary conditions, check ur boundary conditions again!
and share it in openFOAM maybe some one can help you |
Quote:
Quote:
Quote:
Quote:
what do you mean by share it in openFOAM? posting on their site? regards, |
What is the topology of OUTSIDE (upload a picture of your domain)? If there is any corner in the patch, applying totalPressure is unphysical. Also, you could try zeroGradient on alpha instead of constantAngle 90 and see if that helps at all.
- Anton |
the domain is a cubic box. all patches except the bottom patch are plain, using patchtype wall and their BCs are defined by OUTSIDE. the bottom is not plain. there are the pyramid structures. the patchtype is wall and the BCs are defined as BOTTOM.
i defined all outside patches as one part in icem and i specify just one BC for all those ambient patches. |
So you have five sides of a box in OUTSIDE, which means you are trying to apply an isopressure boundary condition (totalPressure with p0=const) to a surface which contains corners and edges (i.e. discontinuities).
|
yes, i do. :)
i will check what happens when i use 5 different patches for it and report my results. but thank you so far. |
It doesn't matter if you use one or five patches. The important point is to change your boundary conditions.
|
so instead i should formulate the BC like this?
{ type fixedValue; value uniform 0; } or zero gradient? |
No! fixedValue again is specifying a constant pressure, which cannot physically exist on a discontinuous surface. You will need to specify a gradient instead. The interFoam tutorials use buoyantPressure, or you can use zeroGradient depending on your definition of pressure.
|
okay..
now i used zeroGradient for all BCs, except U at the bottom wall (this is fixed to 0) and apha1 at the ambient patches (this is inletOutlet). but my drop is still rising against gravity... /edit: maybe i will upload a clean and simple version of my case soon, so that you can get an impression of what is happening, since it is hard to explain... |
hi friend
for alpha: zeroGradient for U zergoradient for all patch except the bottom put it fixedValue zero for p put all patch bouyant pressure except for out-let and put fixed value zero ofcurse i suppose ur geometry is a column! |
i am sorry, it seems my case description was quite bad since all of you are unsure about my setup :(
here again, hopefully i can express myself more clearly this time: - i do use a cube as my domain. - the bottom patch is a solid surface (it is not plain but structured). - the other 5 patches are ambient. - there is no inlet or outlet in this case except from the ambient patches. - i tried using zeroGradient for all BCs to fix my problems. with exception of: - U at the bottom wall (this is fixed to 0) - apha1 at the ambient patches (this is inletOutlet). the droplet is still accelerated against gravity. /edit: Quote:
|
hello of_user,
Maybe an obvious question, did you use -9.81 for the gravity? ;) best Wouter |
i updated post 1 to make my case clearer and i provide a downloadable casefile for anyone how is interested in testing ;)
|
All times are GMT -4. The time now is 17:22. |