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#1 |
Senior Member
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Hello Foamers,
I want to simulate a problem which i should set pressure at outlet. as it is not zeroGradient because it is not fully developed flow i should use another outlet type. i read user guide and i think this is a good choice: HTML Code:
pressureInletOutletVelocity Combination of pressureInletVelocity and inletOutlet Best regards, Maysam |
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#2 |
Senior Member
Join Date: Mar 2009
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Depends on your boundary condition.
I pressume, this is just ordinary atmosphere kind outlet, right? In this case probably this will be the best choice { type pressureInletOutletVelocity; value uniform (0 0 0); } |
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#3 | |
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Join Date: Sep 2011
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Quote:
Hi...does it means we know the inlet pressure and we want to know outlet velocity by this by using this function? |
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#4 | |
Senior Member
mauricio
Join Date: Jun 2011
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Quote:
you should use totalPressure for p they are self-stabilizing bcs ![]()
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#5 | |
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Quote:
but is seems in most case total pressure use in inlet and static pressure in outlet? ![]() Also pressureInletOutletVelocity for U can be set in outlet? I was thiking it can only be set in inlet. ![]() ![]() |
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#6 |
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mauricio
Join Date: Jun 2011
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the bcs i mentioned they kinda form a consistent pair and regarding the usage,, i guess you can use it for outlets, but then you have to handle the signs..
here's the description, guess you've seen it already.. i haven't tried it thou ![]() pressureInletOutletVelocity Code:
Description Velocity inlet/outlet boundary condition patches for where the pressure is specified. zero-gradient is applied for outflow (as defined by the flux) and for inflow the velocity is obtained from the patch-face normal component of the internal-cell value. ![]() ty
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Best Regards /calim "Elune will grant us the strength" |
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#7 | |
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Quote:
![]() Where you found this description? Any other document besides the website? |
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#8 |
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mauricio
Join Date: Jun 2011
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the source code
go to your instalation directory (type "which icoFoam" in a terminal and u'll find the dir) then open de *.H and *.C files. they have the descriptions. Search for the name you want, there will generally be a file with such name or very close one.. ![]() theres also a version @ http://www.openfoam.org/docs/cpp/ which has the same files in html
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Best Regards /calim "Elune will grant us the strength" |
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#9 | |
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Yup! I found that but hv to go deep into scr!
http://www.openfoam.org/docs/cpp/ http://foam.sourceforge.net/docs/cpp/a04208_source.html Quote:
I have tried myself with specified outlet velocity with pressureDirectedInletOutletVelocity and inlet with zeroGradient. The simulation can run and vector velocity seems OK! But I havent justified its correctness. Now i try the reverse method inlet velocity pressureDirectedInletOutletVelocity and outlet zeroGradient then see both result. ![]() Last edited by yipiyaya8; March 16, 2012 at 09:21. |
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#10 |
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Aathavan
Join Date: Nov 2012
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Dear Friends,
I have a small problem, actually I got confused totally, the think is i want to keep the total pressure as constant in my whole domain, I have calculate that my Pd = 64.5Pa now I want to implement this, I want to give pressure inlet and pressure outlet 0/U inlet { type pressureInletOutletVelocity; value uniform (0 0 0) // what value i need to use here or is it ok? } 0/p inlet { type fixedValue; } outlet { type fixedValue; value uniform 101325; } what is the condition I need to give for inlet? thanks, Aadhavan |
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#11 |
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mauricio
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hi, let me see if i got this right.. u want to keep the total pressure constant in the whole domain, yet you have a pressure difference (Pd??) of 65pa between inlet-outlet??? i'm sry but i think you need to re-think your problem a bit.. physically speaking... if the total pressure is even in the whole domain i guess there's no dynamics at all!? right? dude i say give your problem a thought and/or explain it better cuz they way u did it looks rly unreasonable..
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Best Regards /calim "Elune will grant us the strength" |
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#12 |
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Aathavan
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Hi Fomers and Calim;
I am simulating a fan using MRFSimpleFoam, I have given the boundary condition as follows, 0/U inlet { type flowRateInletVelocity; flowRate 2; value uniform (0 0 0); } outlet { type zeroGradient; } 0/P inlet { type zeroGradient; } outlet { type fixedValue; value uniform 101325; } the simulation ran upto 10000 Iteration, I have attached the Residual plot as well, please have a look. but the result is not matching with experimental result. actually inlet pressure should be less than outlet pressure but I an getting other way around. I am trying to fix this issue by giving different BC as follows, 0/U outlet { type zeroGradient; } inlet { type pressureInletOutletVelocity; value uniform (0 0 0) 0/p inlet { type totalPressure; gamma 0; p0 uniform 101325; // total pressure value uniform 101325; } outlet { type fixedValue; value uniform 101260.5; // static pressure } while execute the solver, I am getting the following error, Create mesh for time = 0 Reading field p Reading field U --> FOAM FATAL IO ERROR: Cannot find patchField entry for cyclic ILR0 Is your field uptodate with split cyclics? Run foamUpgradeCyclics to convert mesh and fields to split cyclics. file: /home/cerecam/OpenFOAM/OpenFOAM-2.0.1/tutorials/incompressible/MRFSimpleFoam/exCompDomain/onlyPressure/0/U::boundaryField from line 25 to line 76. From function GeometricField<Type, PatchField, GeoMesh>:: GeometricBoundaryField::GeometricBoundaryField ( const BoundaryMesh&, const DimensionedField<Type, GeoMesh>&, const dictionary& ) in file /home/cerecam/OpenFOAM/OpenFOAM-2.0.1/src/OpenFOAM/lnInclude/GeometricBoundaryField.C at line 271. FOAM exiting please guide me how to approach this problem, I am really struggling to solve this problem. please help me, thanks, Aadhavn |
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#13 |
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sirshosona
Join Date: Jan 2013
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I want to use pressureinletoutletVelocity boundary condition for velocity at outlet as this is not fully developed (there is a chance to be backflow) flow. But my question is what the value I should set? Is it always (0 0 0)? What is the function of this fixed value of velocity?
type pressureInletOutletVelocity; value uniform (0 0 0) |
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#14 |
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n/a
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It seems the velocity you prescribe is only for the tangential component of the boundary....I do not think you specify the normal velocity to the boundary... I will look more into this.
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#15 |
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Hi to all
Someone know how velocity is obtained from pressure in pressureInletOutletVelocity? thank to all |
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#16 |
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hello
I want to use the pressureInletOutletVelocity for the outlet of the airfoil boundary condition. But I don’t the mean of tangent velocity?and What is the difference between value and tangential velocity?</SPAN> Is this value scalar or vector? thanks |
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#17 |
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Hi,
why you want use this boundary condition for airfoil? I think that this boundary condition have to be used with multiphase flow or when in the same boundary you have an inlet and outlet flux. This is your case? Anyway a zeroGradient condition is applied for outflow; for inflow, the velocity is obtained from the patch-face normal component of the internal-cell value. |
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#18 | |
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mauricio
Join Date: Jun 2011
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Quote:
hi pressureinletoutletvelocity (in) bcs are to be used with inletoutlet (out) bcs for the u field and you use totalpressure(in) and fixedvalue(out) for the p field these bcs guarantee a well-posed problem in case the user has only pressure measures and backflow expected try that l8r and gl ![]()
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Best Regards /calim "Elune will grant us the strength" |
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#19 |
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mauricio
Join Date: Jun 2011
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just to add,
if these bcs are the best ones for your case that's a whole new ball game! ![]() l8r
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Best Regards /calim "Elune will grant us the strength" |
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#20 |
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hi dear mauricio
thanks for your answer. ![]() But I did not answer my question: What is the difference between value and tangential velocity?Is this value scalar or vector? |
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