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Showing papers by "Ephraim M Sparrow published in 1967"


Journal ArticleDOI
TL;DR: In this paper, the directional distribution of radiant flux reflected from roughened surfaces is analyzed on the basis of geometrical optics, and the analysis successfully predicts the off-specular maxima in the reflection distribution which are observed experimentally and which emerge as the incidence angle increases.
Abstract: The directional distribution of radiant flux reflected from roughened surfaces is analyzed on the basis of geometrical optics. The analytical model assumes that the surface consists of small, randomly disposed, mirror-like facets. Specular reflection from these facets plus a diffuse component due to multiple reflections and/or internal scattering are postulated as the basic mechanisms of the reflection process. The effects of shadowing and masking of facets by adjacent facets are included in the analysis. The angular distributions of reflected flux predicted by the analysis are in very good agreement with experiment for both metallic and nonmetallic surfaces. Moreover, the analysis successfully predicts the off-specular maxima in the reflection distribution which are observed experimentally and which emerge as the incidence angle increases. The model thus affords a rational explanation for the off-specular peak phenomenon in terms of mutual masking and shadowing of mirror-like, specularly reflecting surface facets.

1,673 citations


Journal ArticleDOI
TL;DR: In this paper, a combined analytical and experimental study of the flow and temperature fields in the boundary layer on a continuous moving surface has been carried out, including both laminar and turbulent flow conditions.

664 citations


Journal ArticleDOI
TL;DR: In this article, the free-convection temperature field within a buoyant plume rising from a heated horizontal wire was explored experimentally, and the laminar plume exhibited a slow, regular swaying motion.

63 citations



Journal ArticleDOI
TL;DR: In this paper, a method of analysis is presented for determining closed-form solutions for two-component stratified laminar flow in horizontal ducts of arbitrary cross-section.
Abstract: A method of analysis is presented for determining closed-form solutions for two-component stratified laminar flow in horizontal ducts of arbitrary cross section. It is demonstrated that the method is remarkably easy to apply and produces results of high accuracy. As an application, solutions are obtained for stratified flow in a circular tube. The results are compared with various limiting cases and excellent agreement is found to exist. Among the limiting cases, an exact solution was derived by Green's functions for the problem in which the interface between the flow components is situated at the horizontal diametral plane.

38 citations


Journal ArticleDOI
TL;DR: In this paper, a cylindrical rod along the axis of a converging nozzle was used to determine flow field and surface friction characteristics of a wall jet, and the measured wall-jet velocity profiles could be satisfactorily represented in terms of a law of the wake, wherein the wake function depends on a transverse curvature parameter.
Abstract: The investigation described here is an experimental study directed toward determining flow field and surface friction characteristics of a cylindrical wall jet. The flow configuration is obtained by placing a cylindrical rod along the axis of a converging nozzle. The flow field thus produced consists of a developing turbulent boundary layer co-existing with an outer fluid layer that mixes freely with quiescent surroundings. Direct measurements of fluid friction at the rod surface, performed with a hot-film element, revealed a significant effect of transverse surface curvature on the local friction factor. Velocity profiles at various axial stations exhibited similarity in the outer mixing layer, but not in the boundary layer adjacent to the surface. Representations of the velocity field in terms of law of the wall variables and defect-law variables revealed significant transverse curvature effects. The measured wall-jet velocity profiles could be satisfactorily represented in terms of a law of the wake, wherein the wake function depends on a transverse curvature parameter. In the outer mixing layer, the eddy viscosity data correspond closely to those of free jets.

19 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the hydrodynamic stability of developing laminar flow in the entrance region of parallel plate channel using small disturbances theory and found that the flow was stable.
Abstract: Hydrodynamic stability of developing laminar flow in entrance region of parallel plate channel investigated using small disturbances theory

14 citations


Journal ArticleDOI
TL;DR: Directional distributions of thermal radiation emittance measured for influence of surface roughness of electric nonconductor were measured by as discussed by the authors, showing that thermal radiation can be influenced by the roughness properties of the surface of the electric non-conductor.

8 citations