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Studies of granular flow down an inclined chute. Quarterly technical progress report, 13 June 1992--12 September 1992

Description: The driving force for the granular flow in the experimental region is gravity. The vehicle which re-circulates this flow is an 46 cm Corra-Trough belt conveyor manufactured by Buck-El, Inc. A drawing of this conveyor is shown in Figure 3. Entrance and exit chambers were designed to route the flow between the chute and the conveyor. Both devices had to be flexible because the position of the chute relative to the conveyor changes each time the angle of the chute is changed. Finally, to control the entering flow more accurately, an adjustable gate apparatus was constructed. The first step in setting up the chute is angle adjustment. The granular material used in the experiments described in this report are technical quality glass spheres, three millimeters in diameter. These beads are produced by Cataphote, Inc. Cataphote lists the tolerances for the 3mm spheres at {plus_minus}0.2 mm. The average mass of a single bead was measured to be 0.034 g which gives an average measured specific gravity of the glass at 2.42 g/cm{sup 3}.
Date: December 1, 1992
Creator: Hanes, D. M.
Partner: UNT Libraries Government Documents Department

Vertical natural convection heat transfer data for an enclosed fluid

Description: Natural convection flow of enclosed fluids with high temperature gradients can result in extremely high heat transfer rates. This phenomenon must be accurately modeled in order to predict the correct temperature distribution of structures in contact with the convecting flow. Ignoring the heat transfer by natural convection and assuming only the normal molecular heat conduction of stagnant water can result in an underestimate of the heat transfer by several orders of magnitude. Natural convection of enclosed fluids is different than free convection to a non-enclosed (i.e., open) ambient atmosphere since the recirculating fluid flow pattern can have a significant influence on the resultant heat transfer. Rayleigh numbers extending the entire range from conditions where free convection is a second order effect (e.g., Ra < 3000) to those where turbulent free convection dominates (e.g., Ra > 10{sup 5}) were tested and the results described. Inconsistencies between earlier investigations reported in the literature are resolved because of the wide test range capability. Correlations of the data in the form of Nusselt number as a function of Rayleigh number are provided for 0 < Ra < 10{sup l2}.
Date: December 31, 1995
Creator: Coffield, R. D. & Harry, J. A.
Partner: UNT Libraries Government Documents Department

Phase distribution in complex geometry conduits

Description: Some of the most important and challenging problems in two-phase flow today have to do with the understanding and prediction of multidimensional phenomena, in particular, lateral phase distribution in both simple and complex geometry conduits. A prior review paper summarized the state-of-the-art in the understanding of phase distribution phenomena, and the ability to perform mechanistic multidimensional predictions. The purpose of this paper is to update that review, with particular emphasis on complex geometry conduit predictive capabilities.
Date: December 31, 1992
Creator: Lahey, R. T. Jr.; Lopez de Bertodano, M. & Jones, O. C. Jr.
Partner: UNT Libraries Government Documents Department

Predictive modeling of particle-laden, turbulent flows. Quarterly progress report No. 1, September 1--December 1, 1992

Description: The successful prediction of particle-laden, turbulent flows relies heavily on the representation of turbulence in the gas phase. Several types of turbulence models for single-phase gas flow have been developed which compare reasonably well with experimental data. In the present work, a ``low-Reynolds`` k-{epsilon}, closure model is chosen to describe the Reynolds stresses associated with gas-phase turbulence. This closure scheme, which involves transport equations for the turbulent kinetic energy and its dissipation rate, is valid in the turbulent core as well as the viscous sublayer. Several versions of the low-Reynolds k-{epsilon} closure are documented in the literature. However, even those models which are similar in theory often differ considerably in their quantitative and qualitative predictions, making the selection of such a model a difficult task. The purpose of this progress report is to document our findings on the performance of ten different versions of the low-Reynolds k-{epsilon} model on predicting fully developed pipe flow. The predictions are compared with the experimental data of Schildknecht, et al. (1979). With the exception of the model put forth by Hoffman (1975), the predictions of all the closures show reasonable agreement for the mean velocity profile. However, important quantitative differences exist for the turbulent kinetic energy profile. In addition, the predicted eddy viscosity profile and the wall-region profile of the turbulent kinetic energy dissipation rate exhibit both quantitative and qualitative differences. An effort to extend the present comparisons to include experimental measurements of other researchers is recommended in order to further evaluate the performance of the models.
Date: December 31, 1992
Creator: Sinclair, J. L.
Partner: UNT Libraries Government Documents Department

[Kinetic theory and boundary conditions for flows of highly inelastic spheres: Application to gravity driven granular flows down bumpy inclines]. Quarterly progress report, April 1, 1992--June 30, 1992

Description: In this quarter, we extended our study of the effects of isotropic boundary vibrations to steady, gravity driven, inclined granular flows. These flows are more complex than those considered last quarter because of the presence of slip and mean velocity gradients at the boundary. Consequently, it was first necessary to modify the boundary conditions derived by Richman (1992) to account for corrections to the flow particle velocity distribution function from velocity gradients. In what follows we only summarize the results obtained.
Date: December 1, 1992
Creator: Richman, M. W.
Partner: UNT Libraries Government Documents Department

Chaotic vibrations of tubes with nonlinear supports in crossflow

Description: By means of the unsteady flow theory and a bilinear mathematical model, a theoretical study is presented for chaotic vibrations associated with the fluidelastic instability of nonlinearly supported tubes in a crossflow. A series of effective tools, including phase portraits, power spectral density, Poincar`e maps, Lyapunov exponent, fractal dimension, and bifurcation diagrams, are utilized to distinguish periodic and chaotic motions when the tubes vibrate in the instability region. Results show periodic and chaotic motions in the region corresponding to the fluid damping controlled instability. Nonlinear supports, with symmetric or asymmetric gaps, significantly affect the distributions of periodic, quasiperiodic and chaotic motions of the tube with various flow velocity in the instability region of the TSP(tube-support-plate)-inactive mode.
Date: December 1, 1992
Creator: Cai, Y. & Chen, S. S.
Partner: UNT Libraries Government Documents Department