calculation of shear stress

alimea · June 10, 2018, 05:27

Hi

I want to use shear stress tensor at the middle of a code.
Which one is correct and why?

Code:

tau = mu * dev(twoSymm(fvc::grad(U)));

Or

Code:

tau = mu * twoSymm(fvc::grad(U));

I saw in forces.C code that deviatoric component of stress tensor (dev(...)) is used, do you know why?

Regards

Santiago · June 11, 2018, 03:15

Quote:

Originally Posted by alimea

Hi

I want to use shear stress tensor at the middle of a code.
Which one is correct and why?

Code:

tau = mu * dev(twoSymm(fvc::grad(U)));

Or

Code:

tau = mu * twoSymm(fvc::grad(U));

I saw in forces.C code that deviatoric component of stress tensor (dev(...)) is used, do you know why?

Regards

Is your flow compressible? One is a generalization!

alimea · June 11, 2018, 03:24

Quote:

Originally Posted by Santiago

Is your flow compressible? One is a generalization!

No, that is incompresible

Santiago · June 11, 2018, 04:43

Quote:

Originally Posted by alimea

No, that is incompresible

Again, mathematically, the two eqns are equivalent. Numerically, they're not, and are higly dependent on the Pressure Poisson residuals.

June 10, 2018, 05:27	calculation of shear stress	#1
alimea Senior Member A. Min Join Date: Mar 2015 Posts: 308 Rep Power: 12	Hi I want to use shear stress tensor at the middle of a code. Which one is correct and why? Code: tau = mu * dev(twoSymm(fvc::grad(U))); Or Code: tau = mu * twoSymm(fvc::grad(U)); I saw in forces.C code that deviatoric component of stress tensor (dev(...)) is used, do you know why? Regards

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