# what's the sigma meaning in the Perturbu.C

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 October 5, 2014, 02:57 what's the sigma meaning in the Perturbu.C #1 Member   Jason Tan Join Date: Sep 2014 Posts: 47 Rep Power: 5 I want to simulation LES with magnatic, but it need a perturbu utility,It had a error when i compiled it,because I had a variable "sigma" is conflict with the "sigma" in the Perturbu.C,look below ,anybody could tell me what's the sigma meaning in the Perturbu.C,my sigma represent electric conductivity,is it same ? // streak streamwise velocity U[celli][streamDir] += (utau * duplus/2.0) * (yplus/40.0) * Foam::exp(-sigma * Foam::sqr(yplus) + 0.5) * Foam::cos(betaPlus*zplus) * deviation; // streak spanwise perturbation U[celli][spanDir] = epsilon * Foam::sin(alphaPlus*xplus) * yplus * Foam::exp(-sigma*Foam::sqr(yplus)) * deviation; songwukong and dong like this.

October 5, 2014, 05:35
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Bruno Santos
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Quick answer: From post #14 at http://www.cfd-online.com/Forums/ope...tml#post494266
Quote:
 Code: ```// Perturbation properties //wall normal circulation as a fraction of Ubar/utau duplus 0.25; //spanwise perturbation spacing in wall units betaPlus 200; //streamwise perturbation spacing in wall units alphaPlus 500; //transverse decay sigma 0.00055; //linear perturbation amplitude as a fraction of Ubar epsilon 0.005;```

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