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Re: [sparta-users] [EXTERNAL] Validation chemical reactions in a box
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From: Steve P. <sj...@gm...> - 2024-09-24 00:12:11
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>> is there a command in SPARTA to count the number of a specific reaction? At the end of a run, there is a section in the log file which lists gas (or surface) reactions and gives the counts for each reaction during the run. There is also a current pending PR $405, which has a new compute gas/reaction/grid command which will count the numbers of different reactions (within) each grid cell for the current timestep. This values can be written to a dump grid file, or could be input to compute reduce to produce a total count (all grid cells) of a particular reaction which could be output with the stats_style command. Steve On Mon, Sep 23, 2024 at 5:28 AM Marc Vives Massana < mar...@kr...> wrote: > Dear Michael, > > I've tried to implement what you suggested but when simulating only the > reaction O2+O2 -> O2 + O2 with zero energy release, apparently, no > reactions take place. The way I've implemented it now is to first simulate > the dissociation of oxygen with its corresponding reactions until it > reaches equilibrium, then, i only simulate O2+O2 -> O2 + O2 with zero > energy release. > > Furthermore, I now check the number of reactions from the log file but is > there a command in SPARTA to count the number of a specific reaction? > > Best, > Marc > > El vie, 20 sept 2024 a las 17:15, Gallis, Michael A. (<ma...@sa...>) > escribió: > >> Marc >> >> >> >> The equilibrium DSMC simulations maintain the gas at equilibrium, so >> there is no flow, transport or a transient. As said, all the code does is a >> numerical, Monte Carlo integration of the reaction cross section over the >> velocity distribution function. >> >> >> >> You can easily calculate the reaction rate at equilibrium, for any >> reaction. You can just suspend product creation and energy release. The gas >> will stay at equilibrium and you just tally the reactions for any >> particular temperature. >> >> >> >> So for example for O2+O2 -> O2 + O +O just simulate : O2+O2 -> O2 + O2 >> with zero energy release. >> >> >> >> Michael >> >> >> >> >> >> *From: *Marc Vives Massana <mar...@kr...> >> *Date: *Thursday, September 19, 2024 at 6:25 AM >> *To: *Gallis, Michael A. <ma...@sa...> >> *Cc: *spa...@li... < >> spa...@li...> >> *Subject: *Re: [EXTERNAL] [sparta-users] Validation chemical reactions >> in a box >> >> Dear Michael, >> >> >> >> Thank you again for the clarifications! After reading more about what you >> suggested, I've realised that what I actually want to do is to compare the >> analytical QK model expression for reaction rates at equilibrium against >> the results from the DSMC simulation. This would effectively verify the set >> up and then compare the results with the experimental data you provided in >> your papers to validate for example. >> >> >> >> Do you know a way to compute the reaction rates in equilibrium when using >> the QK model? Furthermore, is it possible to obtain an analytical >> expression for the transient properties in a "closed box" when using the QK >> model. >> >> >> >> Thanks in advance, >> >> Marc >> >> >> >> El mié, 18 sept 2024 a las 0:51, Gallis, Michael A. (<ma...@sa...>) >> escribió: >> >> Marc >> >> >> >> For the “closed box” cases like the one you are simulating the code works >> as a Monte Carlo integrator of the reaction probability over the velocity >> distribution function. For the TCE model the reaction probability is >> extracted from the reaction probability using an identical albeit >> analytical integration. So, if the code is not reproducing analytical >> results or is not in agreement with other codes, is because you are using >> different reaction rates. All these are clearly described in Bird 1994, >> Chapter 5. Make sure you are familiar this before you attempt any >> code-to-code comparisons. >> >> >> >> The reaction rates that come with Sparta are taken from Park (1990). >> However, other authors have proposed different reaction rate sets. Thus, >> they are not unique nor are they supposed to agree with any other set. >> >> >> >> For surface chemistry I think the NASA/Ames folk would be better >> positioned to answer your questions. None of the test cases in the 2015 >> tutorial included surface chemistry or gas phase chemistry validation. >> >> >> >> Michael >> >> >> >> >> >> >> >> >> >> >> >> *From: *Marc Vives Massana <mar...@kr...> >> *Date: *Tuesday, September 17, 2024 at 6:18 AM >> *To: *Gallis, Michael A. <ma...@sa...> >> *Cc: *spa...@li... < >> spa...@li...> >> *Subject: *Re: [EXTERNAL] [sparta-users] Validation chemical reactions >> in a box >> >> You don't often get email from mar...@kr.... Learn why >> this is important <https://aka.ms/LearnAboutSenderIdentification> >> >> Dear Michael, >> >> >> >> Thanks for the feedback. The comparison I'm trying to do is not only >> against other codes but also analytical data. Therefore, I took the >> reaction parameters described in sparta/examples/chem example which I >> believe is a similar case. My next question would be where the Arrhenius >> activation energy Ea, prefactor A, and exponent b, used in the example case >> are obtained from. Is a general database stating these parameters for all >> chemical reactions at different temperatures publicly available? >> >> >> >> The next cases that I wanted to replicate are the validated test cases >> that were used to validate SPARTA and presented in the slides from the >> short course in 2015 available from the website. To better understand the >> chemical reactions taking place on the surface and to have a reference, is >> it possible to obtain the cases set up that were used for those >> validations? This would validate the chemical reactions on the surface >> which requires some input data for the reactions that I'm >> struggling to find. Do you know where I can find reliable data for the >> reactions taking place on the surface? >> >> >> >> Thanks in advance, >> >> Marc >> >> >> >> El jue, 12 sept 2024 a las 16:41, Gallis, Michael A. (<ma...@sa...>) >> escribió: >> >> Marc >> >> >> >> This is a very interesting comparison you are trying to do. However, >> before you make a code-to-code comparison you need to make sure both codes >> are using the same molecular parameters, relaxation rates and most >> importantly reaction rates. >> >> >> >> Michael >> >> >> >> *From: *Marc Vives Massana <mar...@kr...> >> *Date: *Thursday, September 12, 2024 at 6:42 AM >> *To: *spa...@li... < >> spa...@li...> >> *Subject: *[EXTERNAL] [sparta-users] Validation chemical reactions in a >> box >> >> Some people who received this message don't often get email from >> mar...@kr.... Learn why this is important >> <https://aka.ms/LearnAboutSenderIdentification> >> >> Dear SPARTA users, >> >> >> >> I've been working on a validation case for the chemical reactions but the >> results are not as good as expected. >> >> >> >> The case is based on the work done by Scanlon et al. (see: >> https://doi.org/10.2514/1.J053370) who were validating dsmcFoam. The >> case basically consists of a box of side length 1e-5 m with gas at 20.000 K >> and 0.0063 atm. The boundaries are specular and adiabatic walls. Initially, >> there is only O2 present in the box and only the dissociation reactions are >> considered: >> >> O2 + O2 --> O + O + O2 >> O2 + O --> O + O + O >> >> >> >> I tested the TCE and QK models and the results for the temperature and >> species fractions are not so good, see the figures below. Therefore, I >> kindly ask if someone could help me in implementing the chemical reactions >> or finding some validated cases with SPARTA so I could take a look at them. >> >> >> >> Thanks in advance, >> >> Marc Vives >> >> >> >> I'll also leave the input file in case it helps: >> >> >> >> ## INITIALISATION ## >> >> seed 12345 >> dimension 3 >> >> global gridcut 1e-5 comm/sort yes >> >> global mem/limit 1024 >> >> units si >> >> boundary r r r >> >> >> # PROBLEM DEFINITION ## >> >> variable l equal 1e-5/2 >> create_box -$l $l -$l $l -$l $l >> create_grid 10 10 10 block * * * >> >> global nrho 2.3118406573249943e+22 fnum 463 >> >> species air.species O2 O >> mixture air O2 O vstream 0.0 0.0 0.0 temp 20000 >> mixture air O2 frac 1.0 >> mixture air O frac 0.0 >> >> create_particles air n 0 >> >> ## SETTINGS ## >> >> collide vss air air.vss >> react tce air.tce >> >> timestep 1e-9 >> >> ## RUN ## >> >> compute counts count O2 O >> compute temp temp >> fix output print 1 "$(step) $(c_temp) $(c_counts[1]) $(c_counts[2])" file >> output screen no >> >> stats_style step np ncoll nreact c_temp >> >> stats 1000 >> >> run 10000 >> >> >> >> _______________________________________________ > sparta-users mailing list > spa...@li... > https://lists.sourceforge.net/lists/listinfo/sparta-users > |
