CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM

BC for pressure driven compressor cascade

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   September 6, 2012, 06:38
Default BC for pressure driven compressor cascade
  #1
New Member
 
Matthew Wright
Join Date: Sep 2012
Posts: 1
Rep Power: 0
MattWright is on a distinguished road
Hi. I am currently doing a thesis where I am running a simulation on a cascade of compressor blades in OpenFOAM. The simulation is 2D and consists of 1 blade with cyclic boundaries on the top and bottom of the domain for the cascade effect. I am running a compressible, laminar case. I ran rhoSimplecFoam and adapted my case from the tutorial, and this runs fine with the BCs the same as the tutorial. However, when I try my own BCs it crashes. I want total pressure specified at the inlet and static pressure at the outlet. The velocity is driven by the pressure at and angle of 55deg at the inlet. Total temperature is also specified at the inlet. Here are my p, U and T files. Can someone tell me what I am doing wrong. Thanks.

FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [1 -1 -2 0 0 0 0];

internalField uniform 101300;

boundaryField
{
BC1_on_INLET
{
type totalPressure;
p0 uniform 101300;
value uniform 101300;
gamma 1.4;
}
BC1_on_LOWER_PERIODIC
{
type cyclic;
}
BC1_on_OUTLET
{
type fixedValue;
value uniform 88131;
}
BC1_on_PROFILE
{
type zeroGradient;
}
BC1_on_SYM1
{
type empty;
}
BC1_on_SYM2
{
type empty;
}
BC1_on_UPPER_PERIODIC
{
type cyclic;
}
}


// ************************************************** *********************** //

FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
BC1_on_INLET
{
type pressureDirectedInletVelocity;
inletDirection uniform (1.428 1 0);
value uniform (0 0 0);
}
BC1_on_LOWER_PERIODIC
{
type cyclic;
}
BC1_on_OUTLET
{
type zeroGradient;
}
BC1_on_PROFILE
{
type slip;
}
BC1_on_SYM1
{
type empty;
}
BC1_on_SYM2
{
type empty;
}
BC1_on_UPPER_PERIODIC
{
type cyclic;
}
}


// ************************************************** *********************** //

FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 0 0 1 0 0 0];

internalField uniform 300;

boundaryField
{
BC1_on_INLET
{
type totalTemperature;
T0 uniform 300;
value uniform 300;
gamma 1.4;
}
BC1_on_LOWER_PERIODIC
{
type cyclic;
}
BC1_on_OUTLET
{
type zeroGradient;
}
BC1_on_PROFILE
{
type zeroGradient;
}
BC1_on_SYM1
{
type empty;
}
BC1_on_SYM2
{
type empty;
}
BC1_on_UPPER_PERIODIC
{
type cyclic;
}
}


// ************************************************** *********************** //
MattWright is offline   Reply With Quote

Old   April 26, 2013, 21:18
Default
  #2
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
Hi Matthew,

I also want to simulate a cascade with same inlet and outlet BC as your. Do you have solved this problem? Please let me know any progress that you have made.
Case of fixed inlet total pressure and fixed outlet static pressure

Regards
Sunxing
Sunxing is offline   Reply With Quote

Old   August 27, 2013, 03:02
Default floating point exception
  #3
New Member
 
Akash Sharma
Join Date: May 2013
Location: Paris
Posts: 15
Rep Power: 4
akashjangid is on a distinguished road
Hey, I am also doing the same case. I have the same boundary condition.
After some iteration there is an error coming floating point exception. Does anyone has solved this kind of error

Thanks !!
akashjangid is offline   Reply With Quote

Old   August 29, 2013, 04:16
Default
  #4
New Member
 
bscphil's Avatar
 
Phillip
Join Date: Mar 2012
Location: Germany
Posts: 27
Rep Power: 5
bscphil is on a distinguished road
Quote:
Originally Posted by akashjangid View Post
Hey, I am also doing the same case. I have the same boundary condition.
After some iteration there is an error coming floating point exception. Does anyone has solved this kind of error

Thanks !!
Hey Foamer's,

by a pressure driven flow simulated with rhoSimpleFoam:
  1. check your initial conditions (e.g. don't set the initial value for U to (0 0 0), but to a small value like (0.1 0.1 0); just trying to set the initial value for p to your static pressure at the outlet)
  2. check your discretization schemes
  3. check your under relaxation factors
  4. check your solver settings
That's it for more information, please post your case as *.zip with the files: fvSchemes, fvSolution, thermophysicalProperties, RASProperties, BC's.

For your next post/problem, please, just characterize your case: solver, discretization schemes, turbulence model, mesh (y+values), fluid properties, physical properties (Mach-range) etc.
bscphil is offline   Reply With Quote

Old   August 29, 2013, 15:13
Default
  #5
New Member
 
Akash Sharma
Join Date: May 2013
Location: Paris
Posts: 15
Rep Power: 4
akashjangid is on a distinguished road
I changes the initial condition for velocity but still same error is coming. I have attached my case here.

Thanks!!
Attached Files
File Type: gz test.tar.gz (2.6 KB, 20 views)
akashjangid is offline   Reply With Quote

Old   August 31, 2013, 18:32
Default
  #6
New Member
 
bscphil's Avatar
 
Phillip
Join Date: Mar 2012
Location: Germany
Posts: 27
Rep Power: 5
bscphil is on a distinguished road
Quote:
Originally Posted by akashjangid View Post
I changes the initial condition for velocity but still same error is coming. I have attached my case here.

Thanks!!
Your boundary conditions seem's to be right. Please post the terminal output of the last time steps. In which equation is the error ??

For your next try change your relaxation factors to:
Code:
relaxationFactors
{    
    fields
    {
        p    0.3; 
        rho    0.05;    
    }
    equations
    {
        U    0.7;
        k    0.7; 
        epsilon    0.7;
        h    0.5;
    }
}
and set
Code:
    transonic       false;
For better results, you've change the schemes from upwind scheme to a more non-diffusive scheme, e.g. linearUpwind or QUICK for the convective terms and decrease the relTol values for p and U,k,epsilon

Good luck
bscphil is offline   Reply With Quote

Old   September 8, 2013, 18:01
Default Difference in results
  #7
New Member
 
Akash Sharma
Join Date: May 2013
Location: Paris
Posts: 15
Rep Power: 4
akashjangid is on a distinguished road
Hello bscphil

My simulation results are coming good now, but there is still one problem.
I have the results in fluent for same case(which are correct), but the openfoam results differ by a lot.
I have attached 2 screen-shot of Mach contour at 50 % span length for fluent and openfoam.

I have the same BC, but the velocity is coming much much higher in openfoam
Any suggestions for this ?

Thanks
Attached Images
File Type: jpg fluent.jpg (25.5 KB, 29 views)
File Type: jpg openfoam.jpg (34.3 KB, 25 views)
akashjangid is offline   Reply With Quote

Old   September 13, 2013, 10:55
Default Temperature Problem
  #8
New Member
 
Akash Sharma
Join Date: May 2013
Location: Paris
Posts: 15
Rep Power: 4
akashjangid is on a distinguished road
Hello,

I gave total temp boundary condition at my inlet

outlet
{
type totalTemperature;
T0 uniform 517.5; ( 517.5 is the total temperature)
value uniform 517.5;
gamma 1.4;
}

But in the result my static temp is going as high as 580 k.
Why is the happening ? plz help me with this ..

Thanks
akashjangid is offline   Reply With Quote

Reply

Thread Tools
Display Modes

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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
internal flow BCs: pressure driven versus velocity driven mihaipruna OpenFOAM Running, Solving & CFD 22 March 6, 2014 11:06
Lid Driven Cavity using Ghost Cell Method and in C++ illuminati5288 Main CFD Forum 0 August 12, 2011 22:05
is there any parallel code for the famous Lid Driven Cavity flow? gholamghar Main CFD Forum 0 August 1, 2010 01:55
How to simulate the fan driven by the airflow? Jason FLUENT 2 April 17, 2008 15:56
Practical/Industrial Appications of the Lid Driven GD Main CFD Forum 1 December 19, 2007 07:30


All times are GMT -4. The time now is 16:10.