[Goutam]

(buoyantBousseinsqSimpleFoam)

I want to calculate local and average Nusselt number for a square cavity when
T_left=303 K, T_right= 283 K, T_ref= 293 K, Detta T = 20, u=v=0 for all wall and uper and lower wall are adiabetic.

local Nu = -0.05 * Grad(T) at the wall

average Nu = Integration [local Nu, {y, 0, 1}]

How I will calculate this, please help me?

I am considering the benchmark problem, paper name:

Natural convection flow in a square cavity revisited: laminar and turbulent models with wall functions, International journal for numerical methods in fluids, vol. 18, pp. 695-719, 1994.