[sita]

Dear all,

I'm playing around with the velocity ramping functionality for multiphase flows (OpenFOAM-dev, build dev-54cb927cee89, on Scientific Linux cluster).

At the moment I'm trying to adapt the DTCHull tutorial case to include a quarter sine velocity ramp at start-up. I've included the required fvOptions file in constant, adapted the simulation parameters to run a transient simulation (the original tutorial uses local time stepping), and added ramping to my inlet and outlet BCs in 0/U.

However, after running setFields, my outlet velocity ramping BC changes back to the original outletPhaseMeanVelocity, without velocity ramping. I've already removed all occurrences of #includeEtc "caseDicts/setConstraintTypes", but still my ramping BC keeps disappearing.

Surely there must be something very silly that I'm overlooking here, but right now I can't find it. Does anyone have experience with this?

Thanks in advance,
Sita

[sita]

Got it: I was using the wrong syntax for the velocity ramping BCs

[seyfigirgin]

Originally Posted by sita

Got it: I was using the wrong syntax for the velocity ramping BCs

Hi Sita,

How did you manage to do this. I want to apply setFields command without changing the boundary conditions also

[sita]

Ouch, that was a long time ago; I changed jobs in the meantime...

I looked up some old code, here's the contents of the 0/u file, hopefully that'll help you:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5.x                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      binary;
    class       volVectorField;
    location    "0";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
#include		"../constant/refValues";

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

internalField   uniform (0 0 0);

boundaryField
{
    // hull parts
	".*\$_s[0-9]_b[0-9]"
	{
		type			movingWallVelocity;
		value			uniform (0 0 0);
	}
	// symmetry plane
    _ymin
    {
        type            symmetryPlane;
    }
	// atmosphere
    _zmax
    {
        type            pressureInletOutletVelocity;
        value           uniform (0 0 0);
    }
	// outlet
    _xmin
    {
        type            outletPhaseMeanVelocity;
        alpha           alpha.water;
        value           $internalField;
        UnMean          
		{
			value		$Uref;
			type		scale;
			scale
			{
				type		quarterSineRamp;
				start		0;
				duration	$duration; //#calc	"400*$deltaT";
			}
		}
    }
	// far side of box
    _ymax
    {
        type            zeroGradient;
    }
	// bottom of box
    _zmin
    {
        type            zeroGradient;
    }
	// inlet
    _xmax
    {        
		type            uniformFixedValue;
		value			$internalField;
        uniformValue    
		{
			value		(#neg $Uref 0 0);
			type 		scale;
			scale
			{
				type	quarterSineRamp;
				start	0;
				duration $duration; //#calc	"400*$deltaT";
			}
		}
	}
}


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

[seyfigirgin]

Originally Posted by sita

Ouch, that was a long time ago; I changed jobs in the meantime...

I looked up some old code, here's the contents of the 0/u file, hopefully that'll help you:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5.x                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      binary;
    class       volVectorField;
    location    "0";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
#include		"../constant/refValues";

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

internalField   uniform (0 0 0);

boundaryField
{
    // hull parts
	".*\$_s[0-9]_b[0-9]"
	{
		type			movingWallVelocity;
		value			uniform (0 0 0);
	}
	// symmetry plane
    _ymin
    {
        type            symmetryPlane;
    }
	// atmosphere
    _zmax
    {
        type            pressureInletOutletVelocity;
        value           uniform (0 0 0);
    }
	// outlet
    _xmin
    {
        type            outletPhaseMeanVelocity;
        alpha           alpha.water;
        value           $internalField;
        UnMean          
		{
			value		$Uref;
			type		scale;
			scale
			{
				type		quarterSineRamp;
				start		0;
				duration	$duration; //#calc	"400*$deltaT";
			}
		}
    }
	// far side of box
    _ymax
    {
        type            zeroGradient;
    }
	// bottom of box
    _zmin
    {
        type            zeroGradient;
    }
	// inlet
    _xmax
    {        
		type            uniformFixedValue;
		value			$internalField;
        uniformValue    
		{
			value		(#neg $Uref 0 0);
			type 		scale;
			scale
			{
				type	quarterSineRamp;
				start	0;
				duration $duration; //#calc	"400*$deltaT";
			}
		}
	}
}


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

Is this your original U file or modified U file to protect your BCs. What did you add to this original U file i don't understand.

[sita]

Usually you start by saying something like, hey, thanks for trying to help!

But anyway, this is the original 0/U file, with a working velocity ramping BC at _xmin. The code at the beginning, under // hull parts, contains regex to refer to different hull parts in the mesh file. As I mentioned earlier, I changed jobs in the meantime, so I don't exactly remember all the details of this, and can't test if the file still works under the current version of OpenFOAM. Hope this helps.



P.S. This 0/U file is not the one for the DTCHull tutorial case, but for a very similar ship simulation, hence the different names, but the velocity ramping BC at the domain inlet (called _xmin here) is the same.