[Wolle]

Hi all!

Originally Posted by poplar

If you have one outlet and the outlet perpendicular to gravity, simply specify a fixed value zero for pressure. If not,you have to specify the static pressure p in version 1.6, pd(=p-rho*h*x) in 1.5. Setting pd=0 is a easy way, I am not sure whether 1.6 supports pd. In 1.6, it seems that uniformDensityHydrostaticPressure is supposed to facilitate the transition from pd to p by specifying an equivalent to constant pd.

Refering to the above example and running it in OF1.7,wouldn't this mean to set p_rgh to zero? What to set for p then? How to apply the uniformDensityHydrostaticPressure BC correctly? I just can't get it right with this p/p_rgh distinction...

In all setups I tried, setting p_rgh to zero lead to an immediate abort of the solver at timestep 0.

Cheers
Wolle

P.S.: Does anyone have a copy of the complete case discussed above by any chance?

[Peter88]

I am trying to do a natural convection case. I got some weird low temperature under the cilinder and pressure stripes at my boundaries Somebody can help me out? See attachment for pictures. The cilinder is 400K and the internal field 300K. If somebody want to see some 0 files, tell me.

[ravikanthmannem]

Hi, can anybody tell me what has to be the temperature boundary condition of pipe wall and pipe outlet in a turbulent pipe flow where there is uniform heat flux(37.5 W/m^2) at wall and fluid entering at 300K

[Mondal131211]

Originally Posted by ozzythewise

Hi,

Below are my 0/U, 0/T and 0/p files for you to take a look at. I have also attached a picture of my velocity field to show you what the results I got looked like:

0/U:

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

internalField uniform (0 0 0);

boundaryField
{
heatedPlate
{
type freestream;
freestreamValue uniform (0 0 0);
}
leftsideatmosphere
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}
rightsideatmosphere
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}
topatmosphere
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}
frontAndBack
{
type empty;
}
}

0/T:


dimensions [0 0 0 1 0 0 0];

internalField uniform 300; //300k

boundaryField
{
heatedPlate
{
type fixedValue;
value uniform 400; //400K
}
leftsideatmosphere
{
type zeroGradient;
}
rightsideatmosphere
{
type zeroGradient;
}
topatmosphere
{
type zeroGradient;
}

frontAndBack
{
type empty;
}
}

0/p:

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

internalField uniform 0;

boundaryField
{

heatedPlate
{
type buoyantPressure;
rho rhok;
value uniform 0;
}
topatmosphere
{
type buoyantPressure;
rho rhok;
value uniform -1.138941; //-rho*g*h
}
leftsideatmosphere
{
type uniformDensityHydrostaticPressure;
rho 1.161;
pRefValue 101325;
pRefPoint (0 0 0);
value $internalField;
}
rightsideatmosphere
{
type uniformDensityHydrostaticPressure;
rho 1.161;
pRefValue 101325;
pRefPoint (0.1 0 0);
value $internalField;
}
frontAndBack
{
type empty;
}

}

I hope these help. If you need to know anything else just let me know.

-J

Hi ozzythewise,

Though you have posted this thread a long time ago, I hope you can solve my problem easily. can you please look at this link and make any comment for my problem? I am really struggling with this problem.

Natural Convection inside a open Cavity

[Raza Javed]

Hello Everyone,


I am using chtMultiRegionSimpleFoam and my Openfoam version is 4.1.


I have created geometry in Salome and and then imported the UNV file to Openfoam.


My geometry consists of a pipe and three rectangular plates, and all these things are in one box.



The rectangular plates are acting as a heat source which I made using fvOption.


Now, the fluid will flow from the pipe, and due to these hot rectangular plates, the temperature of the fluid will change inside the pipe.


At the inlet, I need to put the flow-rate of 5 litres/minutes.



At the inltet, temperature could be room temperature.


Now, My task is to see the temperature change at the outlet.



I have put some boundary conditions for Velocity, Temperature and Pressure, at inlet, outlet and at the walls of pipe.


But my solver is not converging.



I am not getting which boundary conditions to use.


I have tried putting flowRateInletVelocity, but I don't know which boundary conditions to put at other boundaries in this case?


I am putting my geometry and boundary conditions with this post.


I shall be very thankful, is someone can help me out in this.


Thank you

boundary
{
    inlet
    {
        type            patch;
    }
    outlet
    {
        type            patch;
    }

}
U
{
    internalField   uniform (0 1e-3 0);

    boundaryField
    {
        inlet
        {
            type                flowRateInletVelocity;//pressureInletVelocity;//fixedValue;
            volumetricFlowRate  0.066;
            extrapolateProfile  yes;
            value               $internalField;//uniform (0 1e-3 0);
        }

        outlet
        {
            type                zeroGradient;
            //value           uniform (0 0 0);//$internalField;
        }
        "fluid_to_box"
        {
            type            noSlip;
        }
    }
}

T
{
    internalField   uniform 300;

    boundaryField
    {
        inlet
        {
            type            fixedValue;
            value           uniform 450;//$internalField;
            
        }

        outlet
        {
            type            inletOutlet;
            value           $internalField;
            inletValue      $internalField;
        }

        "fluid_to_box"
        {
            type            compressible::turbulentTemperatureCoupledBaffleMixed;
            Tnbr            T;
            kappaMethod     fluidThermo;
            value           uniform 300;
        }
    }
}


epsilon
{
    internalField   uniform 0.01;

    boundaryField
    {
        inlet
        {
            type            fixedValue;
            value           uniform 0.01;
        }

        outlet
        {
            type            inletOutlet;
            inletValue      uniform 0.01;
        }

        ".*"
        {
            type            epsilonWallFunction;
            value           uniform 0.01;
        }
    }
}

k
{
    internalField   uniform 0.1;

    boundaryField
    {
        inlet
        {
            type            inletOutlet;
            inletValue      uniform 0.1;
        }

        outlet
        {
            type            zeroGradient;
            value           uniform 0.1;
        }

        ".*"
        {
            type            kqRWallFunction;
            value           uniform 0.1;
        }
    }
}


p_rgh
{
    internalField   uniform 0;

    boundaryField
    {
        inlet
        {
            type            fixedFluxPressure;//zeroGradient;
            value           uniform 0;
        }

        outlet
        {
            type            fixedValue;
            value           uniform 0;
        }

        ".*"
        {
            type            fixedFluxPressure;
            value           uniform 0;
        }
    }
}

p
{
    internalField   uniform 0;

    boundaryField
    {
        ".*"
        {
            type            calculated;
            //value           uniform 0;
        }
    }
}

[bhavin_1906]

I have a hot plate coinciding with the bottom of my Domain and I want to simulate the natural convection. The problem is that here I do not know which is my inlet and which one is outlet. I have my boundaries as TOP, SIDES, BOOTTOM & PLATETOP. I have used the inletoutlet conditions of the top & sides and zeroGradient for the bottom. But, it seems that the air isn't moving out of the domain, as the temperature continously goes on increasing and never stabilizes. I have a uniform heat source as the BC for the plate. Can someone help me with this problem?