Unexpected results for downward convection at small-angles raised
the question of whether vertical natural convection is the same for
rough and smooth plates. This photo shows the plate suspended
vertically by steel wire from the two boards above. The ambient
temperature sensor is taped to the table leg. I measured the
natural convection over three temperature ranges as was done in the
other natural convection runs.
If there is less convection than expected, then it could be due to heat from one side reducing the convection of a side above it, as happens in the upward facing case.
But slightly more convection than expected was measured. As the plate is no longer in the wind tunnel, modeling the emissivity of the room as 0.9 (versus 0.8 for the wind tunnel) brings the simulation into reasonable agreement with measurement. It thus appears that, at least for laminar flows from rectangular plates, natural convection from a rough surface has the same magnitude as convection from a smooth surface.
The graph below is linked to a pdf of the measurements and simulations of natural convection in level and vertical orientations.

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