Random Velocity Component Research Articles

Effects of separated flow on cotton dust sampling with a vertical elutriator.

The vertical elutriator used for cotton dust sampling was examined theoretically and experimentally to determine airflow patterns and particle transport. The theory of diverging channel flow predicts that a separated eddying flow will occur in the elutriator. This calculation disagrees with the laminar flow assumptions used to predict the size sampling characteristic or cutoff of the elutriator. Smoke injection tests verified random local velocity components and clearly showed that the flow is not uniformly upward and laminar. Particle transport tests indicated that unit density spheres as large as 27 micron can reach the sample on the elutriator filter.

The persistence of warps

Hunter and Toomre (1969) have demonstrated that a simple warp of a stellar disk will damp out within one or two galactic rotation periods due to rapid differential recession of stellar orbits. If, however, the galactic gravitational field is more nearly spherically symmetric, the rate of differential recession is decreased and the warp may persist for a longer time. We therefore propose that the observed gaseous warps exist in regions outside of the massive stellar disk; that is, in regions where the gravitational field is essentially spherically symmetric. A necessary condition of this hypothesis is that long-lived warps are present only in a low mass, low random velocity component of the galaxy – presumably the gas.

Electrokinetic movement of suspended colloids in a flowing medium. II. Experimental investigation

An experimental model was constructed to test the theory developed in Part I. In this model, stainless-steel electrodes were utilized in a parallel-plate configuration. The suspensions studied were prepared from colloidal kaolin and deionized water. The influent concentration of suspension was maintained at 60 mg 1 −1. The flow rate of suspension was 250 ml min −1, while the electric field strength between the electrodes was 100 v cm −1. Mass concentration of suspension was measured at various points in the system both in situ on a continuous basis and by withdrawing samples. Both methods involved light transmittance measurements. The following flow characteristics of the medium were measured with a hot-film sensor and related equipment: (a) mean velocity profile, and the (b) root-mean-square (rms), (c) autocorrelation, and (d) spectral density of the random velocity component. The theoretical equations with appropriate boundary conditions were solved on a digital computer using a continuous system modeling program to provide a comparison of theoretical and experimental results. This analysis indicated that the theoretical equations developed in this study for Brownian and convective dispersion conditions provide a valid description of the electrokinetic movement of charged colloids suspended in flowing water.

Some statistical properties of the ground diffraction patterns of vertically reflected radio waves

This paper describes the results of a vertical incidence fading amplitude experiment vising an array of seven receiving aerials. The purpose of the experiment was to test certain assumptions in the correlation analysis of Briggs et al. (1950) and Phillips and Spencer (1955) and to obtain more detailed information on the spatial structure of the ground diffraction pattern. The results show that in general the spatial and temporal correlation functions have different shapes (the difference increasing when the random velocity component V c is large) and that patterns are often periodic or complex. The values of the various parameters derived from correlation analysis are shown not to be independent of the aerial separation. It is suggested however that short base-line experiments usually give meaningful results.