How to find area of the meshed grid at an inlet or outlet? and How to find flux at a inlet/outlet?

MFiX How to
#1

For a given pipe geometry, the actual dimensions are given (0.305 m in Diameter). however, when you mesh in MFIX due to the cut-cell method- some of the area will be different than the actual geometry specified area.

  1. How do you calculate the cross-sectional area of a certain outlet/inlet after it has meshed?
  2. How do you calculate the volume of the entire MESHED geometry as compared to the actual volume of the geometry ?
1 Like
#2

Hey Niranjan,

I was facing a similar problem. What I do is, I load the mesh.vtu output file into paraview. In this file, the volume for each cell is given, so you can calculate the total volume. For the surface at inlet/outlet, I make a slice there and then use the Cell Size-Filter on that slice, which gives you the area of the cells.

I hope that helps,

Best Janna

#3

The area of a BC region is reported in the .OUT file. In the 22.2 release we will also report the area or volume of monitor regions that involve area (mass flow rates) or volume integrals. These will be in the monitor file header.

#4

Thanks Janna,

This is what I had in mind as well. I will try this!

#5

Thanks Jeff.
Yes, I do remember seeing the area of the BC. However, I was not sure if its the area of just the inlet (say cylinder) or the entire inlet/outlet region (a rectangle).

#6

It is the area of the fluid cells. If there are blocked or cut cells, only the active fluid cells are used in the computation of the area, not the entire rectangular region.

#7

Makes sense.

So I have a cylindrical inlet/outlet and it will only include the area of the fluid cells in this region.

#8

Correct. The area will likely be a bit smaller than a perfect cylinder due to the cut cell meshing (the circle is approximated by a series of lines), especially if the mesh is coarse.

#9

Yes that is correct. I have tried to compare the area in paraview, and its generally 1 - 5% smaller