Experimental Study of the Near Wall Region of a Natural Convection Driven Flow Next to a Vertical Cylinder
Temperature and velocity fields are measured in the boundary layer flow of air along a heated vertical cylinder using cold-wire thermometry, thermocouples and two-component laser Doppler anemometry. Detailed measurements are taken at three different heights, corresponding to Rayleigh numbers, ranging from Ra = gβΔTL 4/ αv ≈ 1.0 ×1010 to Ra ≈ 1.7 ×1011. The highest of these showed clearly evidence of confinement by the containment cylinder. This paper focuses on measurements of the mean and turbulence quantities in the near wall region where the varying thermal properties also affect the flow due to the strong temperature gradient there. A new set of boundary layer equations are established to represent the variable properties of the flow in this region. This experimental investigation also reveals that the strong temperature gradients adversely affect both the steady and unsteady temperature results because of the conduction to the supports of the temperature probes.
KeywordsBoundary Layer Wall Shear Stress Natural Convection Rayleigh Number Wall Region
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