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United States Department of Agriculture

Agricultural Research Service

Title: Surface Roughness and Turbulence Intensity Effects on Scalar Transfer from Soil Surfaces

Authors
item Sauer, Thomas
item Norman, John - UNIV OF WISCONSIN-MADISON
item Mitchell, John - UNIV OF WISCONSIN-MADISON

Submitted to: Proceedings of the Conference on Biometeorology and Aerobiology
Publication Type: Abstract Only
Publication Acceptance Date: February 2, 1996
Publication Date: N/A

Technical Abstract: Exchange of heat and vapor between the soil surface and canopy air has important implications for canopy microclimate and especially leaf wetness and dew duration. A series of field experiments were completed beneath a corn (Zea mays L.) canopy using smooth heat and vapor source plates to measure the interfacial heat and vapor transfer coefficients. Here we report on complementary free and forced convection laboratory heat transfer experiments designed to address the effects of aerodynamic roughness and turbulence intensity on interfacial transfer coefficients. A series of forced convection heat transfer experiments were completed using a 0.35 by 0.86 m anodized aluminum plate. Surface roughness was created by placing 12.7-mm tall by 19-mm diameter aluminum cylinders on the plate surface at spacings of 75 or 37.5 mm. Forced convection heat exchange was measured at air velocities from 9.2 to 2 m s**-1 with free stream turbulence intensities ranging from 0.04 to 0.4. Transfer coefficients for the dense array of roughness elements with a high turbulence intensity were approximately 3 times larger than for the smooth, laminar case. Experiments with wooden roughness elements showed that a rough surface with insulating roughness elements transferred less heat than a smoother surface with efficient heat conducting elements.

Last Modified: 10/21/2014
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