Showing papers by "Richard J Goldstein published in 1973"

Turbulent convection in a horizontal layer of water

Abstract: Overall heat transfer and mean temperature distribution measurements have been made of turbulent thermal convection in horizontal water layers heated from below. The Nusselt number is found to be proportional to Ra0·278 in the range 2·76 × 105 < Ra < 1·05 × 108. Eight discrete heat flux transitions are found in this Rayleigh number range. An interferometric method is used to measure the mean temperature distribution for Rayleigh numbers between 3·11 × 105 and 1·86 × 107. Direct visual and photographic observations of the fluctuating interferogram patterns show that the main heat transfer mechanism is the release of thermals from the boundary layers. For relatively low Rayleigh numbers (up to 5 × 105) many of the thermals reach the opposite surface and coalesce to form large masses of relatively warm fluid near the cold surface and masses of cold fluid near the warm surface, resulting in a temperature-gradient reversal. With increasing Rayleigh numbers, fewer and fewer thermals reach the opposite bounding surface and the thermals show persistent horizontal movements near the bounding surfaces. The central region of the layer becomes an isothermal core. The mean temperature distributions for the high Rayleigh number range are found to follow a Z−2 power law over a considerable range, where Z is the distance from the bounding surface. A very limited agreement with the theoretically predicted Z−1 power law is also found.

Light-Scattering Characteristics of Biological Particles

Abstract: Measurements have been obtained of the light-scattering characteristics of 0.5 μ diameter polystyrene spheres, red blood cells, and hemoglobin free red cell “ghosts.” The information obtained consists of measurements of the magnitude of laser radiation scattered by dilute aqueous suspensions of the above particles as a function of the particle concentration and the angle of observation, measured from the direction of the incident beam. In addition, the results for the spheres are compared to analytical predictions calculated from the Mie theory.The light source employed is a 75 mW He Ne laser operating continuously at 632.8 nm. The laser beam is spatially filtered and focused (large F no.) at the center of a 1.6 cm i.d. cylindrical glass scattering cell. Scattered intensity measurements are obtained with an S-20 multiplier phototube, mounted on a beam which rotates about the scattering cell as an axis.The data for the polystyrene spheres are quite strongly forward directed with a relative minimum at about...