Hello，everyone！
I’ve added three chemical reactions to my case：R1：2C+O2=2CO R2：CO+0.5O2=CO2 R3：C+O2=CO2
I find that R2 has an exceptionally high rate of reaction, but instead of CO2, CO is produced.
I don’t know what’s wrong, can you check it out for me? And I want to make sure that a large reaction rate means that the reaction must be going on?
Thank you very much!
singleC.mfx (30.5 KB)
usr_rates.f (3.9 KB)
usr_rates_des.f (6.7 KB)
I always prefer using monitors over visualization if you want to understand what’s going on. I added an “average over region” for mass fractions, and “maximum over region” for reaction rates, with a monitor_dt of 0.001
Here’s what I’m seeing:
MAXRATE.csv
# Monitor type: Maximum over region, Volume = 0.19200000E-04
# "Time","RRates_R2","RRates_R1","RRates_R3"
0.0000000 , 0.0000000 , 0.0000000 , 0.0000000
0.10169130E-02, 0.0000000 , 0.67576306E-14, 0.0000000
0.19997211E-02, 0.0000000 , 0.11574247E-10, 0.0000000
0.30060696E-02, 0.0000000 , 0.81608432E-09, 0.0000000
0.40095064E-02, 0.0000000 , 0.14276240E-07, 0.0000000
0.50282069E-02, 0.0000000 , 0.96808860E-07, 0.0000000
0.60484333E-02, 0.0000000 , 0.45335439E-06, 0.0000000
0.70099748E-02, 324.95020 , 0.11943785E-05, 0.0000000
0.80737755E-02, 11.312259 , 0.22639025E-05, 0.0000000
0.90700591E-02, 22.390174 , 0.10874491E-01, 0.0000000
0.10010304E-01, 605.74353 , 0.10434127 , 0.0000000
0.11082880E-01, 102.24452 , 0.10441414 , 0.0000000
0.11996040E-01, 501.98753 , 0.10453213 , 0.0000000
0.13010662E-01, 256.26517 , 0.10475122 , 0.0000000
0.14138019E-01, 463.70910 , 0.10640284 , 0.0000000
0.15178331E-01, 551.60614 , 0.11185888 , 0.0000000
MASSFRAC.csv:
# Monitor type: Arithmetic average over region, Volume = 0.19200000E-04
# "Time","x_g_N2","x_g_CO2","x_g_CO","x_g_O2"
0.0000000 , 1.0000000 , 0.0000000 , 0.0000000 , 0.0000000
0.10169130E-02, 0.99867778 , 0.0000000 , 0.0000000 , 0.13222215E-02
0.19997211E-02, 0.99740202 , 0.0000000 , 0.0000000 , 0.25979811E-02
0.30060696E-02, 0.99609910 , 0.0000000 , 0.0000000 , 0.39009013E-02
0.40095064E-02, 0.99479823 , 0.0000000 , 0.0000000 , 0.52017665E-02
0.50282069E-02, 0.99347567 , 0.0000000 , 0.0000000 , 0.65243309E-02
0.60484333E-02, 0.99214975 , 0.0000000 , 0.0000000 , 0.78502466E-02
0.70099748E-02, 0.99089965 , 0.0000000 , 0.23312162E-08, 0.91003500E-02
0.80737755E-02, 0.98942387 , 0.33272042E-08, 0.10579011E-08, 0.10576128E-01
0.90700591E-02, 0.98812647 , 0.87134333E-08, 0.30157790E-09, 0.11873519E-01
0.10010304E-01, 0.98689182 , 0.30262733E-07, 0.39755603E-08, 0.13108163E-01
0.11082880E-01, 0.98541801 , 0.10751546E-06, 0.29373581E-09, 0.14581936E-01
0.11996040E-01, 0.98424234 , 0.18619242E-06, 0.27721044E-08, 0.15757567E-01
0.13010662E-01, 0.98287458 , 0.30683645E-06, 0.39127920E-09, 0.17125260E-01
0.14138019E-01, 0.98143146 , 0.47857943E-06, 0.49951226E-08, 0.18568252E-01
0.15178331E-01, 0.98003853 , 0.74227000E-06, 0.91164418E-08, 0.19960993E-01
the reactions are
R2: CO + 0.5*O2 --> CO2
R1: 2*char + O2 --> 2*CO
R3: char + O2 --> CO2
R3 has a reaction rate of 0. R1 has a reaction rate which is increasing up to 0.11, but R2 is dominating at 551. Both CO2 (column 3) and CO (column 4) have increasing mass fractions, but CO2 is higher than CO by several orders of magnitude, in keeping with the ratio of the reaction rates - 4.0e-05 CO2 vs, 2.2e-08 CO. It looks correct to me.
I see that you are still using MFiX version 23.3.2, maybe try updating to the latest if you are still having trouble.
– Charles
Thank you for your answer.
I tried to run the programme with MFIX 24.1.1, but I have the problem shown in the picture. Do you not have this problem with the latest version of MFIX?
Unsuccessful seeding used to be a warning that most users did not pay attention to. It is now flagged as a fatal error. You can adjust your seeding options or bypass the error (I don’t recommend that) as suggested in the message.
Yes, as Jeff said this warning has been upgraded to a fatal error
Note this message in the output:
|-------------------------------------------------------------------|
| IC Region: 3 |
|-------------------------------------------------------------------|
| Phase | Input | Input | Number of | EPs | Solid |
| ID | Specified | Value | Particles | | mass |
|-------|-----------|-----------|-----------|-----------|-----------|
| 1 | PART NB | 36000 | 26936 | 3.67E-01 | 4.67E-03 |
|-------|-----------|-----------|-----------|-----------|-----------|
I had to reduce the particle number from 36000 to 26900 to get the case to run - I should have mentioned that, sorry.
Thanks，I reduce the particle number from 36000 to 26900 to get the case to run，but then there is the problem of invalid floating point operations (as shown).
Are you experiencing this problem when running it? Is it because the reaction rate of R2 is too large（551kmol/m^3/s)?
Can you please check what those 339 warnings and 21 messages are?
Does the crash occur immediately upon starting the simulation or after a while?
You can try to build the solver with debug flags to see if it gives you the exact location of the crash.
I ran this case and did not see this error. Are you running the latest version? (24.1.1)? How long did the case run before the error occurred? Are you running on Linux or Windows? Linux gives full stack traces, while on Windows we are only able to identify the line where the crash occurred.
I’m running mfix version 24.1.1 on windows and I get this error in about 0.44s.
It seems to have all the warnings about velocity limits being exceeded and will crash after running for a while.
It is possible you are generating too much gas. My suggestion is to run the case without reactions to make sure the hydrodynamics is fine. Then turn the reactions back on, maybe one at a time. Double check your reaction rates to see if what you get is what you expect.
Thanks for the suggestion, I’ll try that.