|
[Sponsors] |
![]() |
![]() |
#1 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
i am new to openfoam v2212, i was running cyclone tutorial, it ran without any problems,
i want to reduce the size by 1000 times, when i reduced the mesh to 1000 times, and decreased the particles and total mass of particles for 1000 times, the case will run and give convergence till particle is injected, but courant number blows up after 1 particle is injected, is there anything i should do.. ? decrease the mesh size may be ? any ideas / suggestions ? please explain in detail thank you in advance ![]() |
|
![]() |
![]() |
![]() |
![]() |
#2 |
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,257
Rep Power: 29 ![]() ![]() |
Hello,
Have you also scaled down the velocity? If not this is not surprising you get a higher Courant number if you didn't change the time step. You say you decreased the particles: number of particles or size distribution? Yann |
|
![]() |
![]() |
![]() |
![]() |
#3 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
i have changed time step decreased it,
i was simulating a swirl tube with 20m/s at inlet, 101325 pa at both dust and air outlet, worst condition was 18g of sand in 1m3 of air , i scaled down particles for "geometry's volume" tried to run the simulation, particle size is 125 micrometers, i am getting around 8500 particles per second for given volume of geometry please tell me if i am doing anything wrong or missed out on anything else thanks for reply |
|
![]() |
![]() |
![]() |
![]() |
#4 |
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,257
Rep Power: 29 ![]() ![]() |
It's difficult to help with that few information. Do you have a MPPICFoam log file?
You can try monitoring your max velocity in the domain, using the fieldMinMax function object: https://doc.openfoam.com/2212/tools/...d/fieldMinMax/ See if your max velocity makes sense or if it's nonphysical. Yann |
|
![]() |
![]() |
![]() |
![]() |
#5 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
buddy, i can share log file on Monday (2 days later), thanks for immediate reply, currently i am not able to give you rep power
|
|
![]() |
![]() |
![]() |
![]() |
#6 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
Last edited by Desimuser1; August 14, 2023 at 00:59. Reason: link didnt work |
|
![]() |
![]() |
![]() |
![]() |
#7 |
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,257
Rep Power: 29 ![]() ![]() |
Hello,
There is not much to do with your file: low residual, and it seems there is no parcel at all. So far so good. Yann |
|
![]() |
![]() |
![]() |
![]() |
#8 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
but the simulation stops after 1 or 2 particle enters the system, and courant number shoots up from max 1.5 (lets say), to something like 8.54e+14, or 9.647e+41, like that,,
i dont know why, but log files wont save error messages, my graph is good but it shoots up, tht shot up part is not there. https://drive.google.com/file/d/1u32...ew?usp=sharing https://drive.google.com/file/d/1Hmb...ew?usp=sharing https://drive.google.com/file/d/16IQ...ew?usp=sharing spike that is there was for when i increased the time step 10 times thanks for reply Last edited by Desimuser1; August 14, 2023 at 09:33. Reason: added links to graph |
|
![]() |
![]() |
![]() |
![]() |
#9 |
Member
Utkan Caliskan
Join Date: Aug 2014
Posts: 43
Rep Power: 12 ![]() |
In general, coupled Eulerian-Lagrangian models are mesh dependent, and the MP-PIC is a much more mesh-sensitive method, and making the mesh 1000 times finer will cause problems. You'd have to decrease the particle size equally. Make sure your particle size is at least 2-3 times smaller than the approx cell size (or cube root of cell volume). Furthermore, a fine mesh naturally will result in higher courant values if the velocity and the timestep remain same. At the end of the day, you'll have to find optimal conditions for the numerical setup.
|
|
![]() |
![]() |
![]() |
![]() |
#10 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
thanks for reply utkan
i will try it out after trying: i got scaled up geometry working, my boundary condition was wrong for velocity (i had given zero gradient at outlet), i have changed it to pressureInletOutletVelocity BC Last edited by Desimuser1; August 21, 2023 at 06:30. Reason: tried the advice |
|
![]() |
![]() |
![]() |
![]() |
#11 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
i started to use original geometry, dia 16mm , velocity of 20m/s, 101325pa at both air and dust outlet, case condition is 18g of sand in 1m3 of air, (i have scaled it to my volume flow rate), and particle size is 88 micrometers, (i get around 126,000) particles passing through it in 1 second, but it is not simulating, i have attached the log file,
thank for reply in advance https://drive.google.com/file/d/1wHU...usp=drive_link https://drive.google.com/file/d/126_...usp=drive_link https://drive.google.com/file/d/12Pk...usp=drive_link https://drive.google.com/file/d/1cD4...usp=drive_link https://drive.google.com/file/d/1XTt...usp=drive_link https://drive.google.com/file/d/1mh6...usp=drive_link |
|
![]() |
![]() |
![]() |
![]() |
#12 |
Member
Utkan Caliskan
Join Date: Aug 2014
Posts: 43
Rep Power: 12 ![]() |
It seems to me that your numerical setup is not properly built. I'd activate the adaptive time stepping. Also, I'd use the code from the OpenFOAM Foundation (.org) for the MP-PIC method.
|
|
![]() |
![]() |
![]() |
![]() |
#13 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
FOR ADJUSTABLE TIMESTEP
i had changed control dict to adapt to adjustable time step (macCo 1), but as soon as the particles start hitting dust outlet or air outlet, courant number shoots up very high from 1 or 1.001.. like that to 10^30 something, the adjustable time step corrects by doing time step in the order of 10^-47 like that, i am thinking boundary conditions might be the problem for velocity @inlet - -20 fixed value at z @dustOut - pressure inlet outlet velocity ,value = 0 (just like base case - cyclone) (i want to try with zeroGradient) @airOut - pressure inlet outle velocity, value = 0 (just as base case - cyclone) ( i want to try with zeroGradient) for p @inlet - zero gradient (i want to change this to fixed flux pressure, value 0) @dustOut - fixed value (101325/1.2) @airOut - fixed value (101325/1.2) if i dont insert particles i am getting convergence at 10-6 accuracy with mesh of 1.2 million cells, (limited computing power) FOR ORG VERSION i had tried ofv10 from the start, the original tutorial of the v10 (Mppic - cyclone) was no running proerly, i.e. Allrun script didnt work for the original tutorial case, so i thought it would be easier to do on v2212 FOR NUMERICAL SETUP i was asked by the client to simulate these consitions and their geometry, i cant change anything thanks for the reply in advance Last edited by Desimuser1; August 23, 2023 at 03:29. Reason: updating numerical setup |
|
![]() |
![]() |
![]() |
![]() |
#14 |
Member
desimuser1
Join Date: Mar 2023
Posts: 35
Rep Power: 3 ![]() |
i had given escape BC to both air and dust outlet,
in the image, it tells 1 particle has escaped, but in dust and air outlet, it tells 0 particles has escaped, so where did it escape to ? currently i thought to run the simulation till i get covergence of 10^-5 accuracy (with new BC), then i will put particles in it thanks for reply in advance Last edited by Desimuser1; August 23, 2023 at 03:38. Reason: update |
|
![]() |
![]() |
![]() |
Tags |
cyclone, mppic, scaling |
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Simulate cyclone separators by MPPICFoam: large errors when scaled down to mm | Dosin | OpenFOAM Running, Solving & CFD | 8 | November 5, 2016 18:50 |
Particle separation in an axial cyclone | Cloudseeker | CFX | 3 | August 19, 2014 21:13 |
Steam-Water Vertical Cyclone Separator | Munggang | FLUENT | 3 | April 29, 2014 14:38 |
Force can not converge | colopolo | CFX | 13 | October 4, 2011 23:03 |
Modelling Industrial cyclone behaviour | Günther Hasse | Main CFD Forum | 3 | October 12, 1999 20:34 |