Floworks Fix fluid volume draining

[Hepcatdsm]

Hi, I am working on a project where I must evaluate the time it takes to drain a fix volume of water that sits in an assembly.

I am looking for ways to:

1- tell Floworks that I have a fix volume and it will only do analysis on this volume of water

2- tell Floworks that the outlet velocity/volume flow rate/mass flow rate is dependant on the free surface height

3- evaluate the time to drain the fixed volume of water

Thx for your help

 

[cbrn]

Hi,
you shouldn't need a CFD to do a task like that: the solution equation is rather simple and the only problem is to determine the variation of volume in function of heigth (because, if the container is a straight cylinder, it's immediate, but if it has a complex shape there may be no explicit law). The best you can do is, in my opinion:
- reverse your time-variant problem to be a "surface-height"-variant problem, and subdivide the total initial height in a sufficiently high number of levels.
- determine with a CAD the initial fluid volume
- determine with a CAD the fluid volume at the next level
- subtract the two volumes in order to have the volume which exits the container in this step
- consider as "free surface height" the average between the initial and final heights
- with that height, and with the volume calculated before, compute the time it takes for this step (that's why the discretization step is important: too fine and it will take years to finish the computation, too coarse and your precision will fly away)
- proceed like that until you have "procesed" all your "levels". Then trivially sum the partial times calculated like that !!

Of course, if in some way you can build up the equation V=f(h), you're done and you can do everything analytically in one pass (provided that you can integrate the function...) !!!

Regards