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Old   January 4, 2015, 03:54
Unhappy uniformTotalPressure BC problems
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Hello, everyone. I want to implement a time-varying total pressure BC. So I use the uniformTotalPressure in OpenFOAM-2.2.2. The velocity boundary is pressureInletOutletVelocity. But as time going on, I always obtain the negative temperature, which is insane.

However, if I just use totalpressure BC without time-varying properties. The simulation is ok. The case aims at solving compressible flow using LES. Piso is used.

Any assistance is appreciated, thanks very much.
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Old   January 4, 2015, 04:22
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The pressure boundary and velocity boundary are belows
PHP Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.2                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    
version     2.0;
    
format      ascii;
    class       
volScalarField;
    
location    "492";
    
object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [--2 0 0 0 0];

internalField   uniform 118847;

boundaryField
{
    
intake_intake
    
{

        
type            uniformTotalPressure;
        
U               U;
        
phi             phi;
        
rho             none;
        
psi             psi;
        
gamma           1.4;
        
pressure        tableFile;
        
tableFileCoeffs 
       

          
fileName     "$FOAM_CASE/constant/p_intake" 
          
outOfBounds  clamp
       } 

    }
        
exhaust_exhaust
    
{

        
type            uniformTotalPressure;
        
U               U;
        
phi             phi;
        
rho             none;
        
psi             psi;
        
gamma           1.4;
        
pressure        tableFile;
        
tableFileCoeffs 
       

          
fileName     "$FOAM_CASE/constant/p_Exhaust" 
          
outOfBounds  clamp
       } 


    }
    
intake_wall_intake_wall
    
{
        
type            zeroGradient;
    }
    
valve1_seat_valve1_seat
    
{
        
type            zeroGradient;
    }

    
exhaust_wall_exhaust_wall
    
{
        
type            zeroGradient;
    }
    
valve2_seat_valve2_seat
    
{
        
type            zeroGradient;
    }
    
cylinderHead
    
{
        
type            zeroGradient;
    }
    
SparkPlug_SparkPlug
    
{
        
type            zeroGradient;
    }
    
stem_wall1_stem_wall1
    
{
        
type            zeroGradient;
    }
    
stem_wall2_stem_wall2
    
{
        
type            zeroGradient;
    }
    
piston
    
{
        
type            zeroGradient;
    }
    
liner
    
{
        
type            zeroGradient;
    }
    
valve1_stem_valve1_stem
    
{
        
type            zeroGradient;
    }
    
valve1_top_up_valve1_top_up
    
{
        
type            zeroGradient;
    }
    
valve1_top_down_valve1_top_down
    
{
        
type            zeroGradient;
    }
    
valve1_bottom_valve1_bottom
    
{
        
type            zeroGradient;
    }
    
valve2_stem_valve2_stem
    
{
        
type            zeroGradient;
    }
    
valve2_top_up_valve2_top_up
    
{
        
type            zeroGradient;
    }
    
valve2_top_down_valve2_top_down
    
{
        
type            zeroGradient;
    }
    
valve2_bottom_valve2_bottom
    
{
        
type            zeroGradient;
    }
    
valve2Baffle_region0
    
{
        
type            zeroGradient;
    }
    
valve2Baffle_region0_slave
    
{
        
type            zeroGradient;
    }
}


// ************************************************************************* // 
PHP Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.2                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    
version     2.0;
    
format      ascii;
    class       
volVectorField;
    
location    "492";
    
object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    
intake_intake
    
{
        
type            pressureInletOutletVelocity;
        
value           uniform (0 0 0);
    }
    
intake_wall_intake_wall
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve1_seat_valve1_seat
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
exhaust_exhaust
    
{
        
type            pressureInletOutletVelocity;
        
value           uniform (0 0 0);
    }
    
exhaust_wall_exhaust_wall
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve2_seat_valve2_seat
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
cylinderHead
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
SparkPlug_SparkPlug
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
stem_wall1_stem_wall1
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
stem_wall2_stem_wall2
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
piston
    
{
        
type            movingWallVelocity;
        
value           uniform (0 0 0);
    }
    
liner
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve1_stem_valve1_stem
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve1_top_up_valve1_top_up
    
{
        
type            movingWallVelocity;
        
value           uniform (0 0 0);
    }
    
valve1_top_down_valve1_top_down
    
{
        
type            movingWallVelocity;
        
value           uniform (0 0 0);
    }
    
valve1_bottom_valve1_bottom
    
{
        
type            movingWallVelocity;
        
value           uniform (0 0 0);
    }
    
valve2_stem_valve2_stem
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve2_top_up_valve2_top_up
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve2_top_down_valve2_top_down
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve2_bottom_valve2_bottom
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve2Baffle_region0
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
    
valve2Baffle_region0_slave
    
{
        
type            fixedValue;
        
value           uniform (0 0 0);
    }
}


// ************************************************************************* // 
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Old   January 12, 2015, 03:04
Default
  #3
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I have solved the problem, just because the uniform pressure within the domain is too small, which induces numerical instability.

But now I met another question, calculation inflow has no problems. But when reverse flow happens, negative temperature occurs near the valve-intake BC (which is the only exit).
I have attached the temperature and velocity distribution as below, the left fig is overall view while the right fig is the enlarged view.
[IMG][/IMG] [IMG][/IMG]
Any advice is appreciated....
Attached Images
File Type: jpg 24_CH5.jpg (24.9 KB, 17 views)
File Type: jpg 24_CH6.jpg (38.5 KB, 13 views)
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