CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

suitable boundary condition for scavenging process?

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 24, 2013, 17:38
Default suitable boundary condition for scavenging process?
  #1
Senior Member
 
immortality's Avatar
 
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26
immortality is on a distinguished road
I have found the cause of errors in my simulation.its at scavenging process.
there is a tube that is filled with
internalField: U=0,T=400K,p=250000pa
and suddenly one side of it become open to environment.the environment has

BC: p0=100000pa and T=288K.
I have set various set of BC's for it but I have not obtain correct answer yet.a divergence in e calculation is occured because of decreasing T below 200K.
I have examined these sets so far:
1)p:waveTransmissive T and U:zeroGradient
Code:
type            waveTransmissive;
        field           p;
        phi             phi;
        rho             rho;
        psi             psi;
        gamma           1.4;
        fieldInf        100000;
        lInf            .1;
        value           uniform 100000;
problem: physically incorrect situation with continously increasing pressure return of decreasing.
2)p:totalPressure T and U:zeroGradient
Code:
type totalPressure;
            p0 uniform 100000;
            gamma 1.4;
            rho rho;
            psi none;
problem: physically incorrect situation with reaching high pressure around 200000 return of outside pressure(100000).
3)p:fixedValue T and U:zeroGradient
Code:
type fixedValue;
      value uniform 100000;
problem: physically incorrect situation with a very low temperature and divergence due to e value.
4)p:fixedValue T:fixedValue U:zeroGradient
T:
Code:
type fixedValue;
      value uniform 288;
p:
Code:
type fixedValue;
      value uniform 100000;
problem:like above(3)
why this simple phenomenon has these difficulties?
could anyone give me any help?
thanks.

Last edited by immortality; January 25, 2013 at 05:34.
immortality is offline   Reply With Quote

Old   January 25, 2013, 01:11
Default
  #2
Senior Member
 
immortality's Avatar
 
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26
immortality is on a distinguished road
any guidance or idea?just a small tube with higher pressure fluid than outside.what's wrong with the modelling?what BC is appropriate? can be linear schemes unstable?
Any thought is appreciated.
immortality is offline   Reply With Quote

Old   January 25, 2013, 06:48
Default
  #3
Senior Member
 
immortality's Avatar
 
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26
immortality is on a distinguished road
fvSchemes:
Code:
fluxScheme      Kurganov;

ddtSchemes
{
    default         Euler;
    ddt(rho)        Euler;
    ddt(rhoU)       Euler;
    ddt(rhoE)       Euler;
    ddt(rho,U)      Euler;
    ddt(rho,e)      Euler; 
    ddt(rho,omega)  Euler;
    ddt(rho,k)      Euler;
}

gradSchemes
{
    default         none;
    grad(U) Gauss linear;
    grad(rho) Gauss linear;
    grad(rhoU) Gauss linear;
    grad((1|psi)) Gauss linear;
    grad(e) Gauss linear;
    grad(sqrt(((Cp|Cv)*(1|psi)))) Gauss linear;
   // grad(c) Gauss linear;
    grad(T) Gauss linear;
    grad(omega) Gauss linear;
    grad(k) Gauss linear; 
}

divSchemes
{
    default none;
    div(tauMC) Gauss linear;

    div(phi) Gauss linear;
    div(phi,omega) Gauss linear;
    div(phi,k) Gauss linear;
    //div(phiEp) Gauss linaer;
    //div(phiUp) Gauss linear;
    //div(sigmaDotU) Gauss linear;
}

laplacianSchemes
{
    default         none;
    laplacian(muEff,U) Gauss linear corrected;
    laplacian(alphaEff,e) Gauss linear corrected;
    laplacian(alpha,e) Gauss linear corrected;
    laplacian(k,T) Gauss linear corrected;
    laplacian(DepsilonEff,omega) Gauss linear corrected;
    laplacian(DkEff,k) Gauss linear corrected;
    laplacian(DomegaEff,omega) Gauss linear corrected;
}

interpolationSchemes
{
    default none;
    reconstruct(rho) vanLeer;
    reconstruct(U) vanLeerV;
    reconstruct(T) vanLeer;

    interpolate(rho) linear;
    interpolate(U) linear;
    //interpolate(T) linear;
    //interpolate(e) linear;
    //interpolate(c) linear;
    interpolate(rhoU) linear;
    //interpolate(rPsi) linear;
    interpolate(muEff) linear;
    interpolate(tauMC) linear;
}

snGradSchemes
{
    default none;

    snGrad(U) corrected;

}
fvSolution:
Code:
solvers
{
    "(rho|rhoU|rhoE)"
    {
        solver          diagonal;
    }

    U
    {
        solver          smoothSolver;
        smoother        DICGaussSeidel;
        nSweeps         4;
        tolerance       1e-11;
        relTol          0;
        maxIter        2000;
    }

    h
    {
        $U;
        tolerance       1e-12;
        relTol          0;
        maxIter         2000;
    }

   e
   {
   $U;
   tolerance 1e-12;
   relTol 0;
   maxIter 5000;
   }

   "(k|omega)"
   {
   solver smoothSolver;
   smoother GaussSeidel;
   nSweeps 3;
   tolerance 1e-11;
   relTol 0;
   maxIter         2000;
   }
}
I have attached files of my case:
Attached Files
File Type: gz scavenging_1.tar.gz (5.1 KB, 1 views)
File Type: gz scavenging_2.tar.gz (5.0 KB, 1 views)
File Type: gz scavenging_3-p.tar.gz (5.0 KB, 1 views)
File Type: gz scavenging_3-p_InletOutlet.tar.gz (5.0 KB, 1 views)
File Type: gz scavenging_3_p_T.tar.gz (5.0 KB, 1 views)
immortality is offline   Reply With Quote

Old   January 25, 2013, 19:10
Default
  #4
Senior Member
 
immortality's Avatar
 
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26
immortality is on a distinguished road
does someone know any experiment result of pressures at a scavenging process of a suddenly opened tube to surroundings?
immortality is offline   Reply With Quote

Reply


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
External Radiation Boundary Condition (Two sided wall), Grid Interface CFD XUE FLUENT 0 July 8, 2010 06:49
how to set up a wall boundary condition according to calculated wall shear stress? gameoverli OpenFOAM Pre-Processing 1 May 21, 2009 08:28
[Commercial meshers] Trimmed cell and embedded refinement mesh conversion issues michele OpenFOAM Meshing & Mesh Conversion 2 July 15, 2005 04:15
Pressure Boundary Condition Matt Umbel Main CFD Forum 0 January 11, 2002 10:06
The Boundary Condition about the Flat Plate boing Main CFD Forum 1 January 6, 2002 16:53


All times are GMT -4. The time now is 18:32.