Learning Forum

[MDave]

Hello,

I have modeled 2D "Eulerian two phase: fluid-granular system" in Fluent (for fluidized bed). The solid volume fraction is 0.65. After running transient analysis, the solid volume fraction contours observed in CFD post are attached herewith (For 0 s and 0.01 s). At 0th s, the solid volume fraction contour shows non-homogeneous graphics (kind of red dots). However, by using probe, the value of solid volume fraction at every point in the patched region is showing 0.65 (which is correct). Then, after selecting immediate next time step (0.01 s), the graphical image seems good (plain single colour).

Kindly guide for the possible reasons behind this.

Thanks.

[Karthik Remella]

Hello,nWhat does your contour plot at t = 0 s look like in Fluent? Before you run the model, could you please check this plot in Fluent and share it with us? Also, what does the plot look like in Fluent at t = 1 s?nKarthikn

[MDave]

Thank you sir for the response. The plots in fluent before running the model and at t = 1 s are attached herewith. In fluent, after running the simulation the maximum value of solid volume fraction is showing 0.649 (in the contour legend) instead of 0.65. nn

[Rob]

Staff are not permitted to open attachments. If the packing limit is 0.65 it's likely the maximum solids volume fraction will be very slightly below this. At the packing limit any slight solver inaccuracy (eg vol fraction 0.6500000000000001) would cause the particle bed to separate VERY quickly so a small amount of leeway is built in. n

[MDave]

Thank you Sir, for the information as well as explanation. I am uploading figures here for 's comment. nBefore running simulationnAt t = 1 snThanks and Regards. n

[Rob]

That looks fine. In Fluent don't select any surfaces when plotting in 2d. You're currently plotting contours on the cell facets (edges). n

[MDave]

Thank you sir. May I know what can be possible reason for the contours obtained in CFD post as mentioned in the 1st question in this thread. n

[Amine Ben Hadj Ali]

As I mentioned on The ALH and Learning Room: Check your graphics card driver and update it. Also ensure you are using a real professional graphic card and not a gaming one or graphic chip. Second: ensure you are using CFD-Post Compatible files. Third: do expect limitations when post-processing Fluent results in CFD-Post.n

[MDave]

Thank you sir. Noted all the points. So in case any discrepancy is found between the contours of Fluent and CFD post (because of any of the above reasons); we must rely on Fluent plots, right? n

[Rob]

Given the plot from Post was at 0.01s and 1s in Fluent I'm not sure what I should be comparing. The messy red/orange may mean you patched the volume fraction at the packing limit, which is very definitely not recommended, and the Fluent output is reflecting some numerical issues. n

[Amine Ben Hadj Ali]

Fluent is the solver-CFD-Post ist just the post-processer->You rely on Solver results!n

[MDave]

Okay, understood. Thank you sir.n

[Amine Ben Hadj Ali]

Welcome!n

[MDave]

Does CFD-Post Compatible files mean, we should select Fluent -> Solution -> Calculation Activities -> Automatic Export -> File type -> CDAT for CFD-post & EnSight ? nAlso, is 4 GB Radeon 530 graphic card compatible with CFD-post? nThank you in advance. n

[Rob]

Up to you, CFD post will read cdat and dat files. However, Fluent can't read cdat as there isn't enough information in them for the solver. nGraphics cards that we support are listed here, https://www.ansys.com/solutions/solutions-by-role/it-professionals/platform-support Note, if a card isn't listed it means we've not tested it, it may work, it may not. n

[MDave]

Thank you sir.n