Variable T_inf for convection problem in a pipe using groovyBC
 

Hi all,
I am trying to simulate a simple pipe with constant heat flux walls, which are cooled by fluid flow going through the pipe.

Here is an image for better illustration:

http://www.cfd-online.com/Forums/att...1&d=1378316658

Here is what I am gonna do. For wall BC I want to use:

In which T_inf is the average bulk temperature of the fluid, which varies across the pipe.

To calculate bulk temperature I want to use the average value of T as a variable of x (Length from the inlet).

How can I calculate this average in each x and use it as T_inf?

Is it possible to do this using groovyBC?

Not the way you'd want to.

The first thing is that T_avg(s) is not really well defined after the pipe bend (BTW: convention is that x is a component of cartesian coordinates. The string length which you mean is s. At least the way I learned it). So the first thing would be to specify/calculate it for the whole geometry. Then you can calculate your T_avg(s) (for this there is actually a functionObject swakExpressionAverageDistribution in the development verson. But currently there is no way to feed that data back to your BC)

Thank you Bernhard.

Why don't you use the turbulentHeatFluxTemperature boundary condition?

See also http://www.cfd-online.com/Forums/ope...mperature.html

In principle you're right. The problem is the T_inf he wants: an average of the T in the fluid. I don't think turbulentHeatFluxTemperature does that (last time I looked you specified the T_inf. It didn't get calculated from the solution)