get dimensionless field values of a geometric field

superkelle · April 6, 2020, 09:34

I wish to use a approximation for a coefficient "Rstabilisation" that is dependent on a dimension variable/field " nElectron" in my whole simulated region. The value of nElectron is in the "log" what is a transcendent function and only accepts dimensionless values. I worked around by defining a new dimensionless field nElectronDimless.

Code:

volScalarField nElectronDimless = nElectron;
nElectronDimless.dimensions().reset(dimless);

volScalarField RStabilisation = RDefault*exp(-stabParamR*log(nElectronDimless));

Is there a nicer way to implement that? I tried something like:

Code:

volScalarField RStabilisation = RDefault*exp(-stabParamR*log(nElectron.field());
...
volScalarField RStabilisation = RDefault*exp(-stabParamR*log(nElectron.value());

but those did not work.

superkelle · April 9, 2020, 08:08

When someone is interested, now I work with and I define RStabilisation with its dimensions in "createFields"

Code:

RStabilisation.field() = RDefault.value()*exp(-stabParamR*log(nElectron.field()));

some similar threads for those kind of dimension problems:

volScalarField to power of constant

how to convert to dimensionless scalar in openfoam

Adriana Correia · November 26, 2020, 05:28

I had the some problem using tanh and it worked with your solution! Thanks a lot

April 6, 2020, 09:34	get dimensionless field values of a geometric field	#1
superkelle Member alexander thierfelder Join Date: Dec 2019 Posts: 71 Rep Power: 6	I wish to use a approximation for a coefficient "Rstabilisation" that is dependent on a dimension variable/field " nElectron" in my whole simulated region. The value of nElectron is in the "log" what is a transcendent function and only accepts dimensionless values. I worked around by defining a new dimensionless field nElectronDimless. Code: volScalarField nElectronDimless = nElectron; nElectronDimless.dimensions().reset(dimless); volScalarField RStabilisation = RDefaultexp(-stabParamRlog(nElectronDimless)); Is there a nicer way to implement that? I tried something like: Code: volScalarField RStabilisation = RDefaultexp(-stabParamRlog(nElectron.field()); ... volScalarField RStabilisation = RDefaultexp(-stabParamRlog(nElectron.value()); but those did not work.

April 9, 2020, 08:08		#2
superkelle Member alexander thierfelder Join Date: Dec 2019 Posts: 71 Rep Power: 6	When someone is interested, now I work with and I define RStabilisation with its dimensions in "createFields" Code: RStabilisation.field() = RDefault.value()exp(-stabParamRlog(nElectron.field())); some similar threads for those kind of dimension problems: volScalarField to power of constant how to convert to dimensionless scalar in openfoam ruloz and Adriana Correia like this.

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November 26, 2020, 05:28		#3
Adriana Correia New Member Adriana Ferreira Join Date: Sep 2018 Posts: 6 Rep Power: 8	I had the some problem using tanh and it worked with your solution! Thanks a lot