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February 25, 2010, 14:01 
Boundary conditions  OpenFoam

#1 
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sankarv
Join Date: Feb 2010
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I am a new user of OpenFoam and I am trying to setup an underexpanded supersonic jet issuing into an open atmosphere.
I am using the rhoCentralFoam and it has an example for the a similar jet. Even though I can just copy the b.c. files (p,T and U) from the tutorial, I would like to better understand the various keywords in these files. For example, Jet_inlet { type totalPressure; value uniform 300000.0; p0 uniform 300000.0; U U; phi phi; rho none; psi psi; gamma 1.4; } I do not understand all the keywords here. what does p0, phi, and psi stand for ? I saw another example where all of the above keywords are not used ? Is there any documentation for what kind of keywords must be specified for what kind of boundary conditions ? Somebody please help. Thanks Vaidya 

February 26, 2010, 06:50 
Underexpanded jets  Boundary conditions help

#2 
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sankarv
Join Date: Feb 2010
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Hello OpenFoamers
I need some help with the boundary conditions desperately. As I have mentioned in my previous post, I am trying to simulate an underexpanded jet. I have successfully simulated the same problem using Fluent. Now I am trying to use OpenFoam to compare the two solvers. (BTW, This is my first ever OpenFoam simulation.....) I am using rhoCentralFoam. It is a 2D grid I imported from Fluent using fluentMeshtoFoam. Here is the configuration. _________________________________  freestream     wall_inlet   Outflow   !  ! jet_inlet axis  ! Here is my 'p' file dimensions [1 1 2 0 0 0 0]; internalField uniform 10000.0; boundaryField { Jet_inlet { type totalPressure; value uniform 300000.0; p0 uniform 300000.0; U U; phi phi; rho none; psi psi; gamma 1.4; } wall_inlet { type zeroGradient; } axis { type zeroGradient; } outflow { type pressureTransmissive; value 10000.0 } top_boundary { type pressureTransmissive; value 10000.0 } } // ************************************************** *********************** // For the outflow and top_boundary (freestream) I have tried wave transmissive, zeroGradient,pressureTransmissive boundary conditions. But the simulation always crashes when the initial transient shock reaches the outflow. Here is my 'U' file dimensions [0 1 1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { Jet_inlet { type fixedValue; value uniform (319.2 0 0); } wall_inlet { type fixedValue; value uniform (0 0 0); } axis { type zeroGradient; } outflow { type inletOutlet; inletValue uniform (0 0 0); value uniform (0 0 0); } top_boundary { type zeroGradient; } } Here is my 'T' file { Jet_inlet { type totalTemperature; value uniform 300; T0 uniform 300; U U; phi phi; rho none; psi psi; gamma 1.4; } wall_inlet { type zeroGradient; } axis { type zeroGradient; } outflow { type zeroGradient; } top_boundary { type totalTemperature; value uniform 300; T0 uniform 300; U U; phi phi; rho none; psi psi; gamma 1.4; } } I must admit I am using the boundary conditions by looking at similar files in the rhoCentralFoam. I would sincerely appreciate if someone can tell me what is wrong with my setup and also if possible tell me the meaning of the various keywords in the b.c files 'p','U' and 'T'. I can make an educated guess about some of them, but I would be more comfortable hearing that from experts out there... Please help Thanks Vaidya 

March 19, 2010, 05:05 

#3 
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did you find a solution for the definition of psi, phi and U in totalPressure bc?


April 4, 2010, 18:02 
Creating New solver: for particle laden compressible jets

#4 
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sankarv
Join Date: Feb 2010
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Hello OpenFoamers
I am a new user of OpenFoam and I am trying to setup a particleladen underexpanded supersonic jet issuing into an open atmosphere. Note, before I started OpenFoam, I ran fluent and got a converged solution for this problem Here are details of OpenFoam simulation:  Solver: rhoCentralFoam Grid: axisymmetric grid imported from Fluent using fluentMeshtoFoam I.C: I used the converged Fluent solution as initial condition for openFoam I managed to get a converged steady state solution for this problem without particles Particle laden jets: ! Now I am trying to run a particleladen jets. Since the solver rhoCentralFoam does not have Lagrangian Particle Tracking in it, I realized that I have to create a new solver. I came across the icoLagrangianFoam solver which is basically a particle tracking solver for an incompressible flow. I found a nice tutorial "Tutorial icoLagrangianFoam/SolidParticle" by Auerlia Vallier (google for file name: Tutorial_icoLagrangianFoam_reviewed.pdf). I used that and managed to implement particle tracking in the rhoCentralFoam solver. I called this new solver rhoCentralParticleFoam This works well. But the problem is that the drag model in the original icoLagrangianFoam is a very simple constant drag model. I want to implement the standard drag model which is a function of particle Reynolds number based on the stokesian drag for spherical particles. Chapter 5 in the tutorial describes how to implement this drag model. When I did these changes I get compilation errors that I cannot comprehend. I admit that I don't know c++ and I am not able to figure out the exact problem. Can someone help me to fix these compilation errors ? I have attached a tar file which contains the codes I am using for this solver 

October 22, 2010, 02:58 
underexpanded jets

#5 
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karthick
Join Date: Oct 2010
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halo mr. sankarv
i am a new user of fluent! from ur post i learnt that u ve successfully simulated underexpanded jets in fluent. presently i am tryng to simulate the same!!! but i don get the results at alll can u just help me with the same!!!! could u say me wat sort of profile ahs to be put and the necessary boundary conditions to be specified in gambit and the NPR values to be put in the fluent!!!! i am desperately in nedd of ur help !!! 

October 22, 2010, 09:29 

#6  
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sankarv
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Karthick
There is a paper by K. Senesh & V.Babu titled Numerical Simulation of Subsonic and supersonic jets, AIAA 20053095. In this paper they talk about the models, grids, initial conditions and boundary conditions for fluent. I followed this paper to setup my case in fluent. Please try to look up this paper. Quote:


February 14, 2012, 07:18 

#7 
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edin michael
Join Date: Feb 2012
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Hi i am just starting in cfd... and am trying to simulate underexpanded jet using fluent. but my solution is not converging. can you please help me with it.


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