April 16, 2022 at 7:57 pmGermanchoacrSubscriber
Hi I have a Fluent bus exhaust transient simulation with these high residuals:April 18, 2022 at 10:37 amNikhil NaraleAnsys EmployeeHello
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Can you provide more details on the computational domain, mesh, models, and the solver settings?
As you have tried multiple things, can you try refining the mesh and check if that works?
April 18, 2022 at 4:10 pmGermanchoacrSubscriberHello nnarale thanks for answering. The residuals:
The domain is made with a mesh of about 2.5 million elements, the physics corresponds to a turbulent, transient, multicomponent, incompressible system. What you say about solver I dont know if are solution methods I have in Solution: Methods: scheme: simple...
April 19, 2022 at 7:11 amNikhil NaraleAnsys EmployeeHello,
It looks like the residuals are still moving down. Why don't you try extending your simulation for some more iterations and let the residuals stabilize a bit.
Can you also try monitoring the parameter of your interest (for example, pressure or velocity) and not only the residuals and see if that converges (Reaches to a constant value after some iterations)?
April 19, 2022 at 11:03 amRobForum ModeratorGiven it's transient you also need to run the model long enough to cover whatever time you're interested in. Why is the model transient and not steady?
April 20, 2022 at 5:26 pmApril 20, 2022 at 6:52 pmNikhil NaraleAnsys EmployeeHello,
It is difficult to comment on the convergence of the solution just on the basis of the residual plots. I would recommended you to plot and monitor the output parameters of you interest. Check if those parameters are reasonable and perhaps are constant (provided that those parameters are not inherently un-steady).
April 21, 2022 at 12:49 amApril 21, 2022 at 12:50 amApril 21, 2022 at 12:50 amGermanchoacrSubscriberApril 21, 2022 at 6:59 amNikhil NaraleAnsys EmployeeHello,
If you are using Specie Transport model, 'Species' function should appear in the function's drop down menu. Can you check if the model is turned on because from the latest residual plot that you shared, it looks like you are not solving for the species.
If not X-Y plot, you can define a surface report from 'Report definition' for monitoring species concentration, provided that the Specie Transport model is turned on, with respect to iterations/time steps and plot and monitor it along with the solution.
April 21, 2022 at 8:02 amphanicmsfSubscriberThank you.
April 23, 2022 at 2:54 amApril 25, 2022 at 4:07 amGermanchoacrSubscriberAs refinement criterion I created a cell register for all the domain and after click in calculate appears these changes:
Grid size [original |adapted |change ]
cells [2,494,995 |9,979,980 |+7,484,985 ]
faces [5,105,117 |30,285,321 | +25,180,204 ]
April 26, 2022 at 12:05 pmNikhil NaraleAnsys EmployeeHere you are trying to activate automatic mesh refinement, which helps fluent to refine/coarsen the mesh during a calculation.
What I suggested is to try refining the mesh before you import it in Fluent solver. In simple words, try reducing the size of the cells in your mesh. Note that, this will increase the overall computational time.
April 26, 2022 at 12:06 pmNikhil NaraleAnsys EmployeeAny thoughts on this?
April 27, 2022 at 5:04 amGermanchoacrSubscriberHi the simulation reports: solution converged since time step 8 of 2000 programmed, reaching a continuity residual of 1e-5 :
now I have a trouble with a mixture properties
having same properties values than a different previus mixture
and that volume_volume appears with air not with the mixture
Finally appears erased the nitrogen-oxide-air mixture and I don┬┤t find how to create it again...
April 28, 2022 at 4:00 amApril 28, 2022 at 7:20 amNikhil NaraleAnsys Employee
If there are 3 species, you just have to define mass fractions for the two. Solver will calculate the mass fraction for the 3rd specie (1 - addition of the two mass fractions).
April 28, 2022 at 7:04 pmGermanchoacrSubscriberThansk Nikhil I already know that before, but it does not answer my questions
Thanks in advance
April 29, 2022 at 2:25 amGermanchoacrSubscriberNow in Inlet exhaust I can add the NO specie. I still have a dude with a mixture nitrogen-oxide-air properties having same properties values than a different previus original case mixture and than pure NO...
April 30, 2022 at 3:48 amGermanchoacrSubscriberI can add de NO specie changing the order of the species of the mixture clicking Edit in name and then the Last Species buttom
May 4, 2022 at 4:33 amMay 4, 2022 at 10:21 amRobForum ModeratorWhat concentration of CO relative to NOx have you got? Remember you have convection and diffusion to consider.
May 4, 2022 at 6:59 pmMay 5, 2022 at 10:42 amRobForum ModeratorViewing 25 reply threads
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