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Mixed Convection from a Rough Plate


Convection formulas are known for forced flow within pipes having smooth and rough interior surfaces as well as for plates with smooth surfaces. However, the convective surface conductance of plates with rough surfaces has not been established. A correlation is developed by positing an analogy between turbulent forced convection in pipe interiors and plates.

A plate with precisely 3 mm of roughness was machined and a wind-tunnel built to house it. Measurements taken with this apparatus match the new correlation within ±3% at Reynolds numbers from 3000 to 40000.

Mixing natural convection with horizontal forced flow was successfully modeled by the L2-norm for vertical and upward-facing plates and the L4-norm for downward-facing plates. With vertical flow on a vertical plate, mixing transitioned between the L4-norm and the L2-norm for both upward and downward flows.

A formula for natural convection from an inclined plate was tested and found to agree within a few percent of rough plate measurements.

Finally, these formulas are combined into a model for mixed convection from rough plates at any inclination.

Full Article

Mixed Convection from a Rough Plate

Supplementary Data

Natural Convection
natural.pdfNatural Convection at a dozen Raleigh numbers in vertical and horizontal orientations.
angles.pdfNatural Convection at angles from −90 to +90
Mixed Convection
mixed-up.pdfRough face up; horizontal forced flow
mixed-aid.pdfRough face vertical; upward forced flow
mixed-vt.pdfRough face vertical; horizontal forced flow
mixed-opp.pdfRough face vertical; downward forced flow
mixed-dn.pdfRough face down; horizontal forced flow


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Copyright © 2016 Aubrey Jaffer

I am a guest and not a member of the MIT Computer Science and Artificial Intelligence Laboratory.  My actions and comments do not reflect in any way on MIT.
agj @ alum.mit.edu
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