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Unphysical temperature drop when using dynamic mesh

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Old   June 18, 2020, 13:07
Post Unphysical temperature drop when using dynamic mesh
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peyman havaej
Join Date: Jan 2016
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Dear All


I have recently added an Energy equation to a compressible flow solver developed by myself. It seems that the energy equation is solved correctly on the static mesh; it presents a logical and physical solution.


However, when there is a mesh motion, an unreasonable temperature drop is observed in the fluid domain.
I have tried to debug and fix this issue., therefore, considering the following simplified energy equation:

Code:
 fvm::ddt(T) ==fvm::laplacian(alphaThermal,T)
I have set all boundaries and initial conditions to 353K, then it could be logical that temperature remains constant and equal to 353 at the whole of the computational domain. But the temperature has decreased to below 353K.

I have found the unreasonable temperature drop or conservativeness problem is due to the transient term (fvm::ddt(T)).

I have searched for a solution, but I still do not know how I can deal with this problem.

I will appreciate it if anyone has any idea or suggestion about this problem.

Best regards,
Peyman


dynamicMeshDict:
Code:
dynamicFvMesh dynamicMotionSolverFvMesh;

solver 		velocityLaplacian;

diffusivity quadratic inverseDistance 1(interface_fluid);
pointMotionU
Code:
internalField   uniform (0 0 0);

boundaryField
{
    interface_fluid
    {

	type            fixedValue;
        value           uniform (0 0.04 0);

    }  
  inlet
    {
        type            slip;
        value           uniform (0 0 0);
    }

	outlet
    {
	type            slip;
        value           uniform (0 0 0);
    }

    bottumWalls
    {
        type            fixedValue;
        value           uniform (0 0 0);        
    }
    topWalls
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    frontAndBack
    {
        type            empty;
    }
}

T
Code:
internalField   uniform 353.15;

boundaryField
{
   inlet
    {
        type            fixedValue;
        value           $internalField;
        
    }

	outlet
    {
	type            fixedValue;
        value           $internalField;
    }


    bottumWalls
    {
        type            fixedValue;
        value           $internalField;
    }

    topWalls
    {
        type            fixedValue;
        value           $internalField;
    }


interface_fluid
    {
	type            fixedValue;
        value           uniform 353.15;
     }

    frontAndBack
    {
        type            empty;
    }
}
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Old   June 24, 2020, 08:35
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Hi,

Could you find the problem?

I am running a simulation using density-based solver and dynamic mesh in Ansys Fluent, and I also noticed a temperature drop when the mesh moves compared to the static mesh. If I use the pressure based solver then the result is the same for both static and moving mesh.
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Tags
conservative variables, dynamic mesh, energy equation, numerical error, openfoam

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