local and average Nusselt number
 

Hi everyone

I have problem to obtain the local and average Nusselt number around square cylinder.
Temperature distribution around the cylinder is achieved.
I'm not sure about dimensionless temperature.
which length should be used as characteristic length
what should i do?

Thanks

q= - k Grad T -> q L/k(Tr - T0) = - Grad* T*

Nu = |q|L/k(Tr - T0)

and L is the same characteristic lenght used for defining the non-dimensional form of the continuity, momentume and energy equations

Thanks dear Filippo

but temperature at solid surface of the cylinder is constant.

but you have to consider the normal derivative of the temperature ...