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TUM July 18, 2001 01:40

mesh control problem
 
I am studying simulation of two-phase flow system (solid-liquid). Solid suspense in the liquid that flow through the straight pipe with the geometry below:

Parameters Specification Total length (m) 12.535 Internal diameter (m) 0.06 Configuration Straight Tube inclination Upward 1.190 Volume (m3) 0.035 Particulate

Size (mm) 20.00

Now I have been finish to create the pipe geometry with diameter 0.06 m. And I have been already finish to input the fluid domain: Continuous liquid =Xanthan solution Disperse solid =Calcium alginate bead And I have been already finish to input the boundary condition for input, output and wall: Wall : free slip for Disperse solid & No slip (moving) for Continuous liquid After that I try to set mesh param. with: Maximum edge length = 0.12535 and create surface mesh with default value of surface edge length = 0.062675 and expansion fac. = 1.2 BUT .. Surface mesh cannot create. There is warning " No boundary edge found" So, I try to change the number of the value of surface edge length to create surface. I can find the range of surface edge length about 0.066-0.082 that it can create surface mesh. BUT when I try to write the definition file, it cannot write because there is warning as: Number of floating front nodes detected = 3: Please introduce me to solve this problem, then I can write this file to solve this problem. I think the problem is to be the size of the diameter of the tube that is too small. If I only change the diameter >= 0.12 m. (with the default value of surface edge length), surface mesh can be create and also can write the definition file for solver too.

joseph July 20, 2001 07:01

Re: mesh control problem
 
Hi, generally if during the surface mesh an error occurs then it will not be able to write out a definition file.

try reducing the mesh lenght to 0.006.


Pat Neuman July 25, 2001 13:07

Re: mesh control problem
 
I assume from you message you are using CFX-5, it is a good idea to state this in your message. I hope you are using the latest release, 5.4.1.

Is outer diameter of your cylinder one continuos surface? If so, you would be better off to change this to two 180 degree surfaces.

Finally, under preferences..Meshing mode change your surface mesh type to Advancing Front. This meshing routine will only work if your cylinder is two 180 degree sections.


tum July 26, 2001 10:09

Re: mesh control problem
 
Hi I am sorry that i did not to tellCFX version. That's right CFX-5.4.1 Now i can rum this problem .. i change the value of global tolerence from 0.005 to less than about 0.001. and it can run. Thank you for your comment. Oh to PAT, i use creat/resolve with the diameter 0.06 and deg 360 to creat curve and then i create/surface/extrude that curve. So that i only input the internal diamerter =0.06 , there is not outer diameter

Pat Neuman July 27, 2001 17:17

Re: mesh control problem
 
Regardless or ID or OD, the best way to model a cylinder in CFX 5 is to make two curves, each 180 degrees and extrude both curves to make a cylinder. The meshing routines work better when there are two 180 degree surfaces than a single 360 degree surface.


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