# Algebraic Model for Variance - grid size surface field

 Register Blogs Members List Search Today's Posts Mark Forums Read

 June 28, 2012, 05:03 Algebraic Model for Variance - grid size surface field #1 Member     Alex Join Date: Apr 2010 Posts: 48 Rep Power: 8 Hello, I have a rhoPimpleFoam solver which solve the equation for an extra scalar equation c (progress variable) and an algebraic equation for its variance. The model for the variance is var (c) = a * (Delta X)^2 * (grad (c))^2 where the Delta X is the grid size, a is a constant (0.08333) and grad (c) is the gradient of C field. The solver upload the data for progress variable (which goes from 0 to 1) and variance (which goes from 0 to 0.25) from a two dimensional table . Table looks like: Variance PV other variables 0 0 : : : 1 0.1 0 : : : 1 0.5 0 : : : 1 -------------------------------- My questions are the following: 1) I defined the grid size field in the following way and I would like to know if it's correct surfaceScalarField GridSize ( IOobject ( "GridSize", runTime.timeName(), mesh, IOobject::NO_READ, IOobject::NO_WRITE ), mesh, dimensionSet(0,-1,0,0,0,0,0) ); GridSize = mesh.surfaceInterpolation::deltaCoeffs(); ---------- 2) My secondo question is: considering the equation for the variance: VarC.internalField() = pow((GridSize.internalField(),2)*0.08333*magSqr(fv c::grad(C)); when I run the simulation, after a few iterations, the variance goes out of bound (despite I impose to stay inside the limit of 0-0.25) and the simulation crashes soon. Is that have something to do with the gridsize definition? thanks for the help

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post minhaj_iut FLUENT 3 March 17, 2016 05:57 Attesz CFX 7 January 5, 2013 04:32 Chander CFX 4 April 2, 2012 07:10 siw ANSYS Meshing & Geometry 24 August 24, 2010 11:22 Beginner Main CFD Forum 1 January 7, 2009 06:36

All times are GMT -4. The time now is 10:04.