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[swak4Foam] Problem to calculate grad(U) using swak4Foam |
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March 15, 2012, 17:43 |
Problem to calculate grad(U) using swak4Foam
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#1 |
New Member
Hugo
Join Date: Jan 2011
Location: Montreal
Posts: 27
Rep Power: 15 |
Dear Foamers,
I need to calculate the strain rate tensor S_ij . In OpenFOAM this is made using the relation S_ij = symm(grad(U)). I am trying do this with swak4Foam (funkyDoCalc) but I just can't calculate grad(U). The error is the following: Code:
Time = 1100 strainRate : swak4Foam: Allocating new repository for sampledGlobalVariables --> FOAM FATAL ERROR: Parser Error at "1.7" :"syntax error, unexpected ')'" "grad(U)" " ^" From function parsingValue in file lnInclude/CommonValueExpressionDriverI.H at line 718. FOAM exiting Thanks, Hugo |
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March 15, 2012, 19:06 |
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#2 | |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 4,225
Rep Power: 51 |
Quote:
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March 15, 2012, 19:52 |
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#3 | |
New Member
Hugo
Join Date: Jan 2011
Location: Montreal
Posts: 27
Rep Power: 15 |
Quote:
Thanks Bernhard, Hugo |
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March 19, 2012, 17:16 |
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#4 |
New Member
Hugo
Join Date: Jan 2011
Location: Montreal
Posts: 27
Rep Power: 15 |
Thanks for the patch!
I applied it to 1.6 but I still get the Code:
Parser Error at "1.1-4" :"field grad not existing or of wrong type" "grad(U)" " ^^^^ " From function parsingValue in file lnInclude/CommonValueExpressionDriverI.H at line 724. FOAM exiting Furthermore, I pulled the developing version with mercurial and I get errors when trying to recompile in OF 1.7.1 on OS X 10.6.8. I tried in a desktop and in a laptop with the same result. The recompilation in Ubuntu 11.04 showed -apparently- no errors. Could you please take a look at the attachment ? Thanks! h |
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March 20, 2012, 19:43 |
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#5 | |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 4,225
Rep Power: 51 |
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August 28, 2014, 05:23 |
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#6 | |
Senior Member
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Quote:
I wish to use the "grad(U)" function for the inlet boundary condition for "Tau" using groovyBC. Where, U is fully developed flow. I am getting following error message: Code:
--> FOAM FATAL ERROR: Parser Error for driver PatchValueExpressionDriver at "1.18-21" :"field grad not existing or of wrong type" "2*pow(mag(symm(grad(U))),2)" ^^^^ ----------------| Context of the error: Is "grad(U)" boundary condition possible using groovyBC? I am using OF-2.1.x installed on Ubuntu 11.04 Thanks in advance! |
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August 28, 2014, 06:07 |
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#7 | |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 4,225
Rep Power: 51 |
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September 23, 2014, 01:16 |
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#10 | ||
Senior Member
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Quote:
Quote:
Best Luck! |
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September 24, 2014, 23:38 |
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#11 | |
New Member
Hugo
Join Date: Jan 2011
Location: Montreal
Posts: 27
Rep Power: 15 |
Quote:
Yes, you can calculate grad(U) using expressionField and then manipulate the result as with any other field. This way, you could calculate the instantaneous rate of strain and then control the averaging process as convenient. I do this in controlDict and not with funkyDoCalc as I tried originally. Hope it helps, |
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September 25, 2014, 20:07 |
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#12 |
Senior Member
ArathoN
Join Date: Jul 2011
Posts: 137
Rep Power: 16 |
doesn't openfoam have the utility to calculate the velocity gradient? what does swakfoam do more that the preloaded utility?
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November 24, 2020, 11:28 |
what is the difference between this swak function and surfaceFieldValue?
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#13 | |
Member
Join Date: Apr 2018
Location: UK
Posts: 78
Rep Power: 8 |
Sorry to revive an old post but I am encountering a related problem.
I have been trying to compute grad(U) on wall patches using swak4Foam and built-in OF function surfaceFieldValue and compare the results. After looking at this post, I realise I have been trying to do the impossible as grad(U) is not defined on patches: Quote:
Code:
extremesGradU { type swakExpression; valueType patch; patchName walls; verbose true; expression "grad(U)"; accumulations (min max); outputControlMode timeStep; outputInterval 1; writeStartTime yes; } Now, if I use surfaceFieldValue to compute grad(U) on the "walls" patch, I do get an output: Code:
maxGradUOnWalls { // Mandatory entries (unmodifiable) type surfaceFieldValue; libs (fieldFunctionObjects); // Mandatory entries (runtime modifiable) fields (grad(U)); operation max; regionType patch; name walls; // Optional entries (runtime modifiable) postOperation none; // weightField alpha1; scaleFactor 1.0; writeArea false; surfaceFormat none; // Optional (inherited) entries writeFields false; scalingFactor 1.0; writePrecision 8; writeToFile true; useUserTime true; region region0; enabled true; log true; // timeStart 0; // timeEnd 1000; executeControl timeStep; executeInterval 1; writeControl timeStep; writeInterval 1; } Therefore my question is: why does surfaceFieldValue compute grad(U) if grad(U) not defined on boundary patches? Perhaps I have misunderstood what surfaceFieldValue does. Strangely enough then, if I try to compute snGrad(U) using surfaceFieldValue I do not get an output, but I do get an output for snGrad(U) in swak. p.s. I have tested these on depthCharge2D tutorial. |
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