# the meaning of "mag"?

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 November 17, 2014, 20:16 the meaning of "mag"? #1 New Member   Yongxiao Wang Join Date: Nov 2014 Posts: 16 Rep Power: 3 Hello there, I met some problems about unit. What is the result of the following formula? (2.0)*mag(symm(fvc::grad(U))) Is it the square of strain rate (unit:s^-2) ? What is the meaning of "mag"?

 November 18, 2014, 03:20 #2 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,783 Rep Power: 22 mag = magnitude __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

 November 18, 2014, 06:46 #3 New Member   Yongxiao Wang Join Date: Nov 2014 Posts: 16 Rep Power: 3 Thank you for your reply. Dose this means "mag(symm(fvc::grad(U)))" has no unit? But the error information shows the unit of "(2.0)*mag(symm(fvc::grad(U)))*nu()" is "[0 2 -2 0 0 0 0]". Why is it the unit of nu [0 2 -1 0 0 0 0]?

 November 18, 2014, 08:13 #4 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 19 nu is the kinematic viscosity with unit m^2/s. U is velocity with unit m/s grad is derivative with unit 1/m Multiply all of them and you get m^2/s * m/s * 1/m = m^2/s^2 Everything is fine. __________________ The skeleton ran out of shampoo in the shower.

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