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-   -   Fully developed flow boundary condition (http://www.cfd-online.com/Forums/openfoam-solving/71369-fully-developed-flow-boundary-condition.html)

jits_aps90 December 28, 2009 10:24

Fully developed flow boundary condition
 
I am working on Jets in Crossflow (JICF) problem as a part of my Masters thesis.
At a face, which is inlet for the jet, I want to implement "A FULLY DEVELOPED FLOW" condition, that will help saving my length of the jet pipe, otherwise I will have to work on :

L(entrance) = 0.06 * Re * D. (for laminar flow)

To avoid this, I want to implement such a condition.

How I can implement such a condition in OpenFOAM.

Thanks a lot.

AlanR December 31, 2009 01:51

jits,

One method is to set up the inlet profile with your fully developed flow. The /incompressible/simpleFoam/pitzDailyExptInlet tutorial shows how to do this. There is a file called /constant/boundaryData/inlet/points that has a list of points where you will set your profile. The file /constant/boundaryData/inlet/0/U is where you store the velocity (and other) values for each point. I put the formula in a spreadsheet, calculate the velocity profile data and copy it to the Foam file - this method is working well for me. Good luck,

Alan

jits_aps90 January 4, 2010 00:57

thanks AlanR,
i shall surely try this , seems this should work, even if its 3d I flow, I hope the same things should hold.
thanks once again.

ngj January 4, 2010 05:43

Hi Jitender

Another approach is to look in the example

~/OpenFOAM/OpenFOAM-1.6.x/tutorials/incompressible/pisoFoam/les/pitzDailyDirectMapped

where a mapping procedure is carried out between to planes with a given offset between them. The profile from the interior plane is mapped back on to the inlet, hence between these two planes you basically have an infinitely long pipe, and since you are considering laminar flows, then the distance between the two planes is of minor importance as far as the validity of the velocity (and turbulence) profile(s) goes.

I have some nice pictures of a laminar jet in a laminar cross flow on which I performed a POD-analysis, so if you are interested in seeing the results just drop me an email.

Happy New Year,

Niels

jits_aps90 January 4, 2010 06:10

thanks a lot and i wish the same for you.

i viewed the pitzDailyMapped case, but i couldn't find out at what offset the values are mapped.
and how many times the values are mapped. Are they mapped untill the flow becomes fully developed.

thanks

ngj January 4, 2010 06:52

Hi

Look at the following file in the tutorial case: "system/changeDictionaryDict". Running the utility changeDictionary before running the application changes the boundary type in constant/polyMesh/boundary with whatever is stated in the first file. In the first file you also state the offset vector of the given patch.

I will send you an email later today with my results.

Bests,

Niels

Asgarian September 8, 2011 11:29

Hi
 
Hi,

I guess this page was active long before, but it is still worthy to ask my question.
I need to simulate fully developed flow in a geometry (e.g. pipe) with one inlet and one outlet. I prefer to avoid modelling a long pipe; can I implement the same method to model small piece of pipe instead? :rolleyes:

Tanx

nihossain November 2, 2011 17:10

Quote:

Originally Posted by jits_aps90 (Post 241046)
I am working on Jets in Crossflow (JICF) problem as a part of my Masters thesis.
At a face, which is inlet for the jet, I want to implement "A FULLY DEVELOPED FLOW" condition, that will help saving my length of the jet pipe, otherwise I will have to work on :

L(entrance) = 0.06 * Re * D. (for laminar flow)

To avoid this, I want to implement such a condition.

How I can implement such a condition in OpenFOAM.

Thanks a lot.

Hey, do you have any idea how to do that in FLUENT? I'm having the same problem where I need a fully developed flow at the inlet but don't want to change the pipe length. Some help would be really appreciated.


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