I. Laminar Boundary Layer Stability in Free Convection. II. Laminar Free Convection with Variable Fluid Properties

Citation

Plapp, John Elmer (1957) I. Laminar Boundary Layer Stability in Free Convection. II. Laminar Free Convection with Variable Fluid Properties. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/6DDP-8W66. https://resolver.caltech.edu/CaltechETD:etd-09142004-153230

Abstract

I. LAMINAR BOUNDARY LAYER STABILITY IN FREE CONVECTION The stability with respect to transition to turbulent flow of laminar free convection flow along a semi-infinite flat plate was studied analytically by the method of small oscillations. Six procedures of varying degrees of mathematical complexity for solving approximately the stability problem were developed according to different assumptions regarding the presence or absence of heat conduction and viscous and body forces. The procedure which considers that only inertial, pressure, and viscous forces control the stability was applied to the case of free convection of air along a vertical plate. It was found that the analytic predictions agreed qualitatively but not quantitatively with experimental observations made by other investigators of the appearance of instability in such a flow. II. LAMINAR FREE CONVECTION WITH VARIABLE FLUID PROPERTIES Heat transfer by laminar free convection along a semi-infinite flat plate was analyzed with the assumption that the density, specific heat, viscosity, and thermal conductivity of the fluid are functions of the temperature. An approximate method for obtaining heat-transfer rates was developed and was applied to cases of heating and cooling oils with large changes in their Prandtl numbers. By comparison, it was found that earlier and more general analyses based on essentially constant-property assumptions give good results in the variable-property case when they are based on the properties of the fluid at the plate surface.

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