[Roark]

Hi ya'll,

Is it possible to have solar radiation heat a fluid free-surface? In my model I have specified the temp of the air above the free-surface. Is there heat transfer from the air to fluid? If so, it is probably advective heating and not radiation. Forgive me for elementary questions about heat; civil engineers don't know squat about thermodynamics.

Cheers,
-Simon

[JBurnham]

Yes, it is possible, but it is much easier to only model the heat transfer between the air and the liquid. For that, you use free-surface option, and activate heat transfer physics. Give the void (the air above the free surface) an initial temperature, which will be fixed (unless this is a closed system, in which case use thermal bubble model as well). Specify the heat transfer coefficient between water and air for the fluid to 'Heat Transfer to Void Type 1'. That should get you started. See the User Manual for more detail on modeling thermal transport and various ways of modeling the void region as air (variable pressure, variable density, variable temperature, etc.). If you want to include radiative effects as well, look into the 'Emissivity x Stefan-Boltzmann Constant' variable in the User Manual: modeling radiative gain of water bodies is usually very difficult to do accurately, since the time cycles of interest are measured in days and weeks and months, not minutes or hours.

[Roark]

The time scale of solar radiation are probably not appropriate for Flow-3D. Thanks Jeff!