[Tushar@cfd]

Dear ALL,

I wish to extrapolate internal fields on to the Wall Boundary condition instead of zeroGradient condition.

The following extrapolation I wish to use:

tau[wall] = average(tau) - average(normal)*(Sum( (normal[i]-average(normal))*(tau[i]-average(tau)) )/ Sum (pow((normal[i]-avg(normal)),2) )

where, i depends on the number of neighbouring faces surrounding the cell centre near the wall patch;
normal[i] are the distance of face centres (tau[i]);
Sum depends on the i;
average(tau) is the mean of tau[i];
average(normal) is the mean of normal[i];

How would I progress for the same?

Thanks in Advance!

[gschaider]

Originally Posted by Tushar@cfd

Dear ALL,

I wish to extrapolate internal fields on to the Wall Boundary condition instead of zeroGradient condition.

The following extrapolation I wish to use:

tau[wall] = average(tau) - average(normal)*(Sum( (normal[i]-average(normal))*(tau[i]-average(tau)) )/ Sum (pow((normal[i]-avg(normal)),2) )

where, i depends on the number of neighbouring faces surrounding the cell centre near the wall patch;
normal[i] are the distance of face centres (tau[i]);
Sum depends on the i;
average(tau) is the mean of tau[i];
average(normal) is the mean of normal[i];

How would I progress for the same?

Thanks in Advance!

internalField(tau) gives you a field with the values of the cells next to the patch. All the other things (average, sum, normal(), pow) are named exactly the way you wrote them

[Tushar@cfd]

internalField(tau) gives you a field with the values of the cells next to the patch. All the other things (average, sum, normal(), pow) are named exactly the way you wrote them

Thanks a million Bernhard,

You mean to say I should use the following expression

{
type groovyBC;
variables "taui=internalField(tau);normali=internalField(nor mal());";
valueExpression "tau = average(tau) - average(normal())*(Sum( (normali-average(normal()))*(taui-average(tau)) )/ Sum (pow((normali-average(normal())),2) )";
...
}

Please correct me if I am wrong

[gschaider]

Originally Posted by Tushar@cfd

Thanks a million Bernhard,

You mean to say I should use the following expression

{
type groovyBC;
variables "taui=internalField(tau);normali=internalField(nor mal());";
valueExpression "tau = average(tau) - average(normal())*(Sum( (normali-average(normal()))*(taui-average(tau)) )/ Sum (pow((normali-average(normal())),2) )";
...
}

Please correct me if I am wrong

sum should be lower-case. But looks alright apart from that

[EhsanMh]

Originally Posted by Tushar@cfd

Thanks a million Bernhard,

You mean to say I should use the following expression

{
type groovyBC;
variables "taui=internalField(tau);normali=internalField(nor mal());";
valueExpression "tau = average(tau) - average(normal())*(Sum( (normali-average(normal()))*(taui-average(tau)) )/ Sum (pow((normali-average(normal())),2) )";
...
}

Please correct me if I am wrong

Dear Tushar & Bernhard
I want to use extrapolation you explained here, but when i use the following code:

variables "pi=internalField(p); normali=internalField(normal());";

i get the following error:

--> FOAM FATAL ERROR:
Parser Error for driver PatchValueExpressionDriver at "1.15-20" :"syntax error, unexpected TOKEN_normal"
"internalField(normal())"
^^^^^^
----------------|

[Minisasi]

Hello,
I want to impose on my boundary something like:

 T_b = T_s/5

where
T_b is the temperature at my boundary
T_s is the temperature at the position S .

Is there a way to extrapolate that value at S, and impose it at the boundary?

Thank you in advance,
Cheers