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how to implement the unit gradient vector in openfoam

Dear all,
Recently, I have implemented an equation involving the unit gradient vector, which has the following form, I don't know how to implement it, because it involves the case that the denominator is 0. Is there any good way to solve this problem?

Assumed that p is a volScalarField like pressure and I want to calculate the equation n= $\frac{grad p}{mag(grad p)}$ .

Thans for reading my post.
Best wishes,
Young

Did you solve the problem, i am facing the same situation:confused:

Hi,

Around line 122 of interfaceProperties.C, a unit gradient vector of alpha1_ field (scalar value of Volume Of Fluid) is calculated. This might help you.

https://www.openfoam.com/documentati...8C_source.html

Code:

     // Cell gradient of alpha

     const volVectorField gradAlpha(fvc::grad(alpha1_, "nHat"));

  

     // Interpolated face-gradient of alpha

     surfaceVectorField gradAlphaf(fvc::interpolate(gradAlpha));

  

     // Face unit interface normal

     surfaceVectorField nHatfv(gradAlphaf/(mag(gradAlphaf) + deltaN_));

Value of deltaN_ is decided in interfaceProperties constructor.

Code:

     deltaN_

     (

         "deltaN",

         1e-8/cbrt(average(alpha1.mesh().V()))

     ),