CFD Online Discussion Forums - adding strainRate in a solver

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adding strainRate in a solver

Hello everyone
I want to add strain rate in interFoam and I do not know how to do that. I need to define one more equation to interFoam similar to the temperature but for volume fraction and I wrote the code for solving the matrix but still have a problem with strain rate.

I defined viscosity like:
surfaceScalarField mu=fvc::interpolate(twoPhaseProperties.mu());

and I tried to define strain rate like:
surfaceScalarField strainRate=fvc::interpolate(viscosityProperties.st rainRate());

which it seems the definition of strain rate is not correct. Do I need to declare sth in creatFields.H for it?
Could anyone help me coding this part.

Regards
Mahyar

Hi Mahyar,

You could always calculate the strain rate values with something like this in the top level solver:

Code:

volScalarField strainRate = sqrt(2.0)*mag(symm(fvc::grad(U)));

surfaceScalarField strainRatef = fvc::interpolate(strainRate);

On another look it seems that the incompressibleTwoPhaseMixture class has a public access function to the viscosityModel class.

Something like this might work as well (warning:untested):

Code:

surfaceScalarField strainratef = fvc::interpolate(twoPhaseProperties.nuModel1().strainRate());

I hope that helps!

Cheers,
Kyle

Quote:

Originally Posted by Mahyar Javidi (Post 524415)

HiKyle

Thanks for your reply. I tried the first part of the code that you mentioned beforein my code and I got an error about the type that strainRate returns (which is double).

I was wondering should I define an object for viscosityModel class and use strainRate function through that object. I think this is the case for twophaseProperties.

Best Regards
Mahyar

Hi Mahyar,

I'm confused by your statement. How can strainRate return a double if you're initializing the variable to be type volScalarField?

Kyle

Dear Kyle

sorry for the late reply.
This is the exact error that I receive when I used the definition of strainRate in the code.

error: call of overloaded ‘sqrt(double)’ is ambiguous

regards
Mahyar

try

Code:

foam::sqrt

instead

Hi

I used volScalarField strainRate = foam::sqrt(2.0)*mag(symm(fvc::grad(U)));
and I got this: error: ‘foam’ has not been declared

Regards
Mahyar

you could always just use 1.41421356237!

Thanks Kyle. The solver compiled now.

Greetings to all!

This is one of those frequently asked questions... gotta make a note to add this to the FAQ...

Mahyar, please try the following:

Code:

::sqrt(2.0)

::sqrt(scalar(2.0))

sqrt(scalar(2.0))

scalar(::sqrt(2.0))

scalar(sqrt(2.0))

I don't have time to test any of them right now, but I do vaguely remember that said error message can be overcome with one or more of the above.

Best regards,
Bruno

Hi Bruno

I checked them in my solver and the results are:

scalar(sqrt(2.0)) error: call of overloaded ‘sqrt(double)’ is ambiguous, note: Foam::doubleScalar Foam::sqrt(Foam::doubleScalar)

scalar(::sqrt(2.0)) It works

sqrt(scalar(2.0)) error: call of overloaded ‘sqrt(double)’ is ambiguous

::sqrt(scalar(2.0)) It works

::sqrt(2.0) It works

Regards
Mahyar

Hi Mahyar,

Many thanks for testing them all! I've added the working ones to the FAQ: http://openfoamwiki.net/index.php/FA...9_is_ambiguous

Best regards,
Bruno