About ADM(approximate deconvolution model) and repeated filtering of ui

NewKid · February 4, 2018, 21:01

Hi guys,
Does anybody know ADM (approximate deconvolution model) and the repeated filtering of ui very well?

I wonder if there existed some codes (function) in OpenFoam to solve those repeated filtering of ui. Or how to implement those process in C++ code?

Thanks very much!

NewKid · February 4, 2018, 21:14

The repeated filtering of ui is shown as follows.
ADM.JPG

Santiago · February 5, 2018, 16:47

There is a class in openFOAM called 'LESfilter' for which you have to define a dictionary with the filter of your preference (box, laplace). The usage is really simple.

Regarding ADM, I dont know how easy is to implement it on the PISO framework since the convective term can be solved implicitly. The problem with ADM formulation is thatyou have to advance in time the de-filtered (deconvoluted?) Convective term, forcing the use of an explicit time advancement for it (Adam-Bashford, RK4).

NewKid · February 5, 2018, 19:09

Thanks very much.
The class 'LESFilter' in OpenFoam contains more than 'one-order' filtering?

Santiago · February 8, 2018, 04:15

Quote:

Originally Posted by NewKid

Thanks very much.
The class 'LESFilter' in OpenFoam contains more than 'one-order' filtering?

What do you mean by one-order?

NewKid · February 26, 2018, 01:00

Dear Santiago, I'm sorry not to replay in time because I've spent some days on Spring Festival vacation with my family.
As for the LESFilter class, I've read the files, which seems like an abstract class, and I wonder if you could provide some examples like how to define a dictionary with the filter.
The so-called "one-order" filtering is not very accurate, in fact , I mean "one-time" filtering like 1.JPG, "two-time" filtering like 2.JPG, and "three-time" filtering like 3.JPG.
I wonder how these repeated filtering can be understood and how to code to implement these (in OpenFOAM as defined filters in LESFilter class or pure C/C++).
Thanks very much.
Best regards!

Santiago · February 27, 2018, 04:54

As far as the types of filters implemented in foam-extend go, the one you might want to give a look at is the laplaceFilter. The source code is located in src/turbulenceModels/LES/LESfilters/laplaceFilter

This particular set of filters (yes, is a family depending of the choice of filter length) was proposed by M. Germano in 1986. About the approximate deconvolution, you'll just have to apply the filter repeatedly for the first three terms of the inverse series (N=5).

DongMei · March 17, 2018, 21:16

Hi, Santiago,
I installed OpenFoam 4 in Ubuntu 16.04. The path of laplaceFilter you mentioned is "/opt/openfoam4/src/TurbulenceModels/turbulenceModels/LES/LESfilter/laplaceFilter", which is a little different from yours.
After reading the laplaceFilter.H and laplaceFilter.C files, I think laplaceFilter(const fvmesh& mesh, scalar widthCoeff) or laplaceFilter(const fvmesh& mesh, const dictionary& db) is enough for the filtering of ui, is that right?
As you mentioned, I should repeat the filtering of first three terms of the inverse series, what do the first three terms of the inverse series mean?

February 4, 2018, 21:01	About ADM(approximate deconvolution model) and repeated filtering of ui	#1
NewKid Senior Member LT Join Date: Dec 2010 Posts: 104 Rep Power: 15	Hi guys, Does anybody know ADM (approximate deconvolution model) and the repeated filtering of ui very well? I wonder if there existed some codes (function) in OpenFoam to solve those repeated filtering of ui. Or how to implement those process in C++ code? Thanks very much!

February 27, 2018, 04:54	laplaceFilter -- source code	#7
Santiago Senior Member Santiago Lopez Castano Join Date: Nov 2012 Posts: 354 Rep Power: 15	As far as the types of filters implemented in foam-extend go, the one you might want to give a look at is the laplaceFilter. The source code is located in src/turbulenceModels/LES/LESfilters/laplaceFilter This particular set of filters (yes, is a family depending of the choice of filter length) was proposed by M. Germano in 1986. About the approximate deconvolution, you'll just have to apply the filter repeatedly for the first three terms of the inverse series (N=5).

February 4, 2018, 21:14		#2
NewKid Senior Member LT Join Date: Dec 2010 Posts: 104 Rep Power: 15	The repeated filtering of ui is shown as follows. ADM.JPG

February 5, 2018, 16:47		#3
Santiago Senior Member Santiago Lopez Castano Join Date: Nov 2012 Posts: 354 Rep Power: 15	There is a class in openFOAM called 'LESfilter' for which you have to define a dictionary with the filter of your preference (box, laplace). The usage is really simple. Regarding ADM, I dont know how easy is to implement it on the PISO framework since the convective term can be solved implicitly. The problem with ADM formulation is thatyou have to advance in time the de-filtered (deconvoluted?) Convective term, forcing the use of an explicit time advancement for it (Adam-Bashford, RK4).

February 5, 2018, 19:09		#4
NewKid Senior Member LT Join Date: Dec 2010 Posts: 104 Rep Power: 15	Thanks very much. The class 'LESFilter' in OpenFoam contains more than 'one-order' filtering?

February 26, 2018, 01:00		#6
NewKid Senior Member LT Join Date: Dec 2010 Posts: 104 Rep Power: 15	Dear Santiago, I'm sorry not to replay in time because I've spent some days on Spring Festival vacation with my family. As for the LESFilter class, I've read the files, which seems like an abstract class, and I wonder if you could provide some examples like how to define a dictionary with the filter. The so-called "one-order" filtering is not very accurate, in fact , I mean "one-time" filtering like 1.JPG, "two-time" filtering like 2.JPG, and "three-time" filtering like 3.JPG. I wonder how these repeated filtering can be understood and how to code to implement these (in OpenFOAM as defined filters in LESFilter class or pure C/C++). Thanks very much. Best regards!

March 17, 2018, 21:16		#8
DongMei New Member DongMei Join Date: Mar 2018 Posts: 10 Rep Power: 8	Hi, Santiago, I installed OpenFoam 4 in Ubuntu 16.04. The path of laplaceFilter you mentioned is "/opt/openfoam4/src/TurbulenceModels/turbulenceModels/LES/LESfilter/laplaceFilter", which is a little different from yours. After reading the laplaceFilter.H and laplaceFilter.C files, I think laplaceFilter(const fvmesh& mesh, scalar widthCoeff) or laplaceFilter(const fvmesh& mesh, const dictionary& db) is enough for the filtering of ui, is that right? As you mentioned, I should repeat the filtering of first three terms of the inverse series, what do the first three terms of the inverse series mean?