mhdFoam for fusion plasma

edmund32 · February 12, 2020, 14:55

Hi, I'm sorry if this is a stupid question, but what are good values of rho, nu, mu and sigma in constant/transportProperties to describe a confined plasma in a fusion reactor? I currently have them all set to one just to figure out what's going on but I'm not really sure how to modify these to increase the realism, I mean I've been looking at papers and found values of resistivity ~1e-5, viscosity ~1e-6 (Stanier 2013, Zhang 2019) but I'm not sure how to set them when the permeability is set to 1. Thanks!

HPE · February 12, 2020, 17:00

'Good' in terms of? 'Good' for what? IMHO, the question needs further refinement.

edmund32 · February 13, 2020, 11:12

Yes, I'm sorry I'm fairly new to this, I'll spend some time reading papers and try to formulate this better, but what I mean is I've used the same parameters of permeability,density,conductivity and viscosity (all set equal to 1) to describe liquid metal flow in the Hartmann and Shercliff tutorials that I'm trying to use now to describe plasma, and I feel like I should vary them for this vastly different state of matter, but I'm not completely sure how, I mean, can I just set them to mu=1,rho=1,sigma=10^4,nu=10^-4 to include the effects of the greater conductivity and much smaller viscosity? I'm not really sure how to calculate these when the permeability and density are set to 1, and setting the permeability to that of vacuum and the density to fusion reactor values (10^18 m^-3) seems to break things.

edmund32 · February 25, 2020, 04:38

One thing I would like to ask: when I set the permeability to 4*pi*1e-7 kgms**-2A**-2, the kinematic viscosity to 10m**2s**-1, the density to 1e-6 kgm**-3 and the conductivity to 1e5 s**3A**2kg**-1m**-3, I have to set the timestep to 1e-10 just so the simulation doesn't become unstable. All of these are acceptable parameters for fusion plasma calculations, and the required timestep should be of the order of 10**-8s for an even finer mesh from the Alfven speed of this plasma, why is it so low? And why are the output pressures when I do manage to keep it running on the order of 1e8? Is it just because they're kinematic pressures so dividing by such a small density causes them to be huge? I get similarly large pressures when I start reducing these parameters to the orders of rho=1e-3,nu=1,mu=1.26e-3,sigma=1e2 and I'm wondering if it would be better to just keep these parameters set to unity.

February 12, 2020, 14:55	mhdFoam for fusion plasma	#1
edmund32 New Member Edmund Teller Join Date: Feb 2020 Posts: 12 Rep Power: 6	Hi, I'm sorry if this is a stupid question, but what are good values of rho, nu, mu and sigma in constant/transportProperties to describe a confined plasma in a fusion reactor? I currently have them all set to one just to figure out what's going on but I'm not really sure how to modify these to increase the realism, I mean I've been looking at papers and found values of resistivity ~1e-5, viscosity ~1e-6 (Stanier 2013, Zhang 2019) but I'm not sure how to set them when the permeability is set to 1. Thanks!

February 12, 2020, 17:00		#2
HPE Senior Member Herpes Free Engineer Join Date: Sep 2019 Location: The Home Under The Ground with the Lost Boys Posts: 932 Rep Power: 12	'Good' in terms of? 'Good' for what? IMHO, the question needs further refinement. __________________ The OpenFOAM community is the biggest contributor to OpenFOAM: User guide/Wiki-1/Wiki-2/Code guide/Code Wiki/Journal Nilsson/Guerrero/Holzinger/Holzmann/Nagy/Santos/Nozaki/Jasak/Primer Governance Bugs/Features: OpenFOAM (ESI-OpenCFD-Trademark) Bugs/Features: FOAM-Extend (Wikki-FSB) Bugs: OpenFOAM.org How to create a MWE New: Forkable OpenFOAM mirror

February 13, 2020, 11:12		#3
edmund32 New Member Edmund Teller Join Date: Feb 2020 Posts: 12 Rep Power: 6	Yes, I'm sorry I'm fairly new to this, I'll spend some time reading papers and try to formulate this better, but what I mean is I've used the same parameters of permeability,density,conductivity and viscosity (all set equal to 1) to describe liquid metal flow in the Hartmann and Shercliff tutorials that I'm trying to use now to describe plasma, and I feel like I should vary them for this vastly different state of matter, but I'm not completely sure how, I mean, can I just set them to mu=1,rho=1,sigma=10^4,nu=10^-4 to include the effects of the greater conductivity and much smaller viscosity? I'm not really sure how to calculate these when the permeability and density are set to 1, and setting the permeability to that of vacuum and the density to fusion reactor values (10^18 m^-3) seems to break things. Last edited by edmund32; February 14, 2020 at 05:05.

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February 25, 2020, 04:38		#4
edmund32 New Member Edmund Teller Join Date: Feb 2020 Posts: 12 Rep Power: 6	One thing I would like to ask: when I set the permeability to 4pi1e-7 kgms-2A-2, the kinematic viscosity to 10m2s-1, the density to 1e-6 kgm-3 and the conductivity to 1e5 s3A2kg-1m-3, I have to set the timestep to 1e-10 just so the simulation doesn't become unstable. All of these are acceptable parameters for fusion plasma calculations, and the required timestep should be of the order of 10-8s for an even finer mesh from the Alfven speed of this plasma, why is it so low? And why are the output pressures when I do manage to keep it running on the order of 1e8? Is it just because they're kinematic pressures so dividing by such a small density causes them to be huge? I get similarly large pressures when I start reducing these parameters to the orders of rho=1e-3,nu=1,mu=1.26e-3,sigma=1e2 and I'm wondering if it would be better to just keep these parameters set to unity.