Learning Forum

[aniruddhabose96]

Hi

I am simulating 10 um dense particles in a pipe with DRW model on. I am seeing some weird/strange deposition pattern where it seems the particles are lining up along mesh cells (although not sure). This pattern is not observed with DRW model off or DRW model ON for 100 um particles. Why is this occuring? I have turned ON high-resolution tracking and left everything at default. Please see attached picure.

[judy.cooper]

Hi:

What release are you using?  Are you using an erosion model or sticking fate to measure deposition? Are you using extra tries with DRW?

It is possible that the interaction between the 10 micron particles and the fluid is going wrong for DRW.  The sources here are very small, as particles < 20 microns will usually just follow the streamlines, so the calculation may be subject to mesh effects.  I would try solving the 10 micron particles uncoupled with Discrete Random Walk to see if this is the cause.

[aniruddhabose96]

Hi. Thanks for reply. I am using uniform randomised surface injection with standard method. Without the DRW model the 10 um particles with 2500kg/m3 density fully suspend in the pipe. But with the DRW model, more particles are settling. But literature shows that 10 um particles are fully suspended in DNS/LES studies. So something is wrong in the DRW model for 10 um. I am using unsteady sims with reflect BC on the floor and no Random eddy lifetime . High res tracking is ON. Now I am trying different time scale constant values to see if thats the cause.

What do you recommend to do in this case??

 

[aniruddhabose96]

I checked with Time scale constant = 3 and 0.02 but both predicted significant deposition which is not true for 10 um particles. Is that right?

[aniruddhabose96]

Hi-Is that any theory reg the Time scale constant and its dependence with particle size in DRW model?