An Experimental Study of Turbulent Natural Convection Boundary Layers

[+] Author and Article Information
G. C. Vliet, C. K. Liu

Aerospace Sciences Laboratory, Lockheed Palo Alto Research Laboratory, Palo Alto, Calif.

J. Heat Transfer 91(4), 517-531 (Nov 01, 1969) (15 pages) doi:10.1115/1.3580236 History: Received September 13, 1968; Revised January 27, 1969; Online August 25, 2011


An experimental investigation on turbulent natural convection boundary layers has been conducted with water on a vertical plate of constant heat flux. Local heat transfer data are presented for laminar, transition, and turbulent natural convection, with the emphasis on the turbulent regime. The data extend to a modified Rayleigh number of 1016 for a threefold range in Prandtl number. The results indicate that natural transition occurs in the range 1012 < Ra* < 1014 ; i.e., fully developed turbulent flow occurs by Ra* = 104 . This latter value can be as low as 2 × 1013 with the use of a trip rod. The physical structure of the turbulent boundary-layer flow was studied using the combined time-streak marker hydrogen bubble method. Temperature data and temperature corrected velocity data obtained by hot-film sensors are presented for Ra* values between 8.7 × 1013 and 7.1 × 1014 . For the range of variables investigated, the major conclusions are (a) the local heat transfer coefficient exhibits a slight decrease with length, (b) confirmation that the vortex street layer in the transition region decays into a longitudinal-vortex-type structure, and (c) the outer portion of the thermal and velocity fields can be approximated by power profiles that fit almost all the data available to date.

Copyright © 1969 by ASME
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