[NightWing]

Hi

I have a set of boundary conditions for my problem. Like, i have a one end closed tube which is open at the other end. The tube is inclined at 20 degree. Through the open end air is entering into the tube and the walls of the tube are applied with constant heat flux.

In my problem, i have divided the tube equally into a upper portion (top side) and lower portion (bottom side). I have applied two different magnitude of flux at these two portions

Topside
{
type      fixedGradient;
value    uniform 200;
}

Bottomside
{
type      fixedGradient;
value    uniform 600;
}

Now, i want to calculate the heat transfer coefficient, near to the both walls (top wall and bottom wall) of my tube.

i.e Q/A = k*dt/dx;  Q/A = h*(Tw-Tref);

But in my case the temperature of wall (Tw) at upper portion of my tube will be greater than at my lower end. Eventually my heat transfer coefficient will have a varying values at both sides

Now if i want to calculate heat transfer coefficient nearer to my top portion of my tube:

k*dt/dx =h*(Ttopwall -Tref);  where Ttopwall is the temperature given to the wall due to my applied flux

and

k*dt/dx =h*(Tbottomwall -Tref); here Tbottomwall is the temperature given to the wall due to my applied flux

How can i calculate these boundary values seperately.

i.e. I want to write in a file, Ttopwall and Tbottom wall and then to use it to compute heat transfer coefficient

any suggestion?

[T.D.]

Hi,

to get a patch label (at the Top-level code) use something like:

label Topwallside = mesh.boundaryMesh().findPatchID("Topside");

//Now, for values at boundary cells, you can use something at the Top-level code like:
forAll(mesh.boundaryMesh()[Topwallside],i)
{
double TheValue = T.boundaryField()[Topwallside][i]; // do whatever you want with "TheValue" at position "i"
}

Good Luck !

Regards,
T.D.

[NightWing]

What i did is; i created a new header file called parametersCalc.H

In that i defined like this

label Topwallside = mesh.boundaryMesh().findPatchID("Topside");

//Now, for values at boundary cells, you can use something at the Top-level code like:
forAll(mesh.boundaryMesh()[Topwallside],i)
{
double TheValue = T.boundaryField()[Topwallside][i]; 

htc = Q/(TheValue-Tref);
}

But now the code is compiling but during runtime it shows a dimensional mismatch. As TheValue is not taking up units as Kelvin

What can be done?

Moreover, as i am new to this; is there a way so that i can get all the values of Temperature just next to the wall?

[T.D.]

Hello NightWing,

In order to fix any dimensions errors, you can create and use dimensional scalars by:

dimensionedScalar a("a", dimensionSet(0,0,0,0,0,0,0), 1.0);

so "a" above, will be a dimensioned scalar type of zero dimension and value=1.0.

Good Luck !