Formula for Sediment Transport Subject to Vertical Flows

Sediment transport is a geophysical phenomenon in which sediment particles are driven to move in streamwise and vertical directions by various forces. Almost all existing formulas of sediment transport were derived without considering vertical flows V, resulting in a large discrepancy between measured and predicted transport rates, as has been reported in the literature. This paper investigates the effect of vertical motion on sediment transport. It was found that upward fluid velocity increases particles\u27 mobility, and downward motion increases particles stability. Furthermore, the investigation showed that decelerating flows can promote upward flow and vice versa. New equations were developed to express the influence of vertical motion on sediment transport. A reasonably good agreement between measured and predicted sediment transport rates was achieved

A simple model to extend 1-D hydraulics to 3-D hydraulics

the core of fluid mechanics is the study of friction on a solid/liquid interface, the friction force can be divided into skin friction and form drag. Nikuradse\u27s experiments reveal that the friction factor depends on the Reynolds number (Re) and relative roughness (r), this observation implies the co-existence of skin friction and form drag, but the definitions of Re and r given by Nikuradse cannot be linked with the skin friction and form drag, this leads to the invalidity of existing theory to predict the friction factor in a complex flow, like a channel flow with vegetation. To establish a universal relationship, the hydraulic radius, Reynolds numbers and relative roughness are redefined, and the connection of these parameters with the skin friction and form drag is established. For the flowing fluid, the separation region is generated after passing the fluid, and these eddies form a dead zone , this study reveals that the drag force is proportional to the volume of dead zone. By analyzing the measured data available in the literature, an equation has been established to express the drag force and the volume of dead zone, thus it provides an alternative way to interpret Nikuradse\u27s work and extends the existing outcomes to complex flows. KEY WORDS: Hydrauli

Drag reduction in a flat-plate turbulent boundary layer flow by polymer additives

This paper presents a theoretical study on the velocity distribution and the friction factor of boundary layer flows with polymer additives starting from the concept of “stress deficit.” A novel method of order of magnitude analysis is developed, which converts the governing equations of boundary layer flow into a solvable ordinary differential equation, thus the total shear stress distribution is obtained, then the formulas for the mean velocity profiles and the friction factor for a boundary layer flow are derived after introducing appropriate expressions for the “effective viscosity” and the thickness of viscous sublayer. The derived velocity equation is able to depict the velocity from a solid wall to the outer edge of boundary layer with or without polymer additives using only one fitted parameter D* that is a function of polymer species, its concentration, and Reynolds number. By integrating the velocity profiles, the friction factor and the thickness of boundary layer development are obtained. Experimental data agree well with the theoretical results

Coastal reservoir-a technology to supply sufficient, high-quality and affordable water to industry with minimum environmental/social impact

ABSTRACT: This paper discusses how to supply sufficient water to meet industrial water demand. Australia is not running out of water, but water is running out of Australia’s rivers. About 440km3/year of runoff is lost to the sea, and the total water usage is only about 5-6% of the water availability. Australia is one of the most resourceful countries in the world. All industrial water for the coastal areas can be supplied from coastal reservoirs, even the high-quality cooling water for steel making. To supply sufficient water to inland areas, the author has suggested that the Murray-Darling basin’s cotton farms should be relocated to downstream areas near its coastal reservoir, thus the agricultural water demand is fully met and also the environmental flow is increased significantly. Therefore, its existing dams can be used for mining industry. Water pipelines may be needed to pump water from these dams to the mining sites, trains can also transport water bags from ports to inland areas

Formulae of Sediment Transport in Unsteady Flows (Part 2)

Sediment transport (ST) in unsteady flows is a complex phenomenon that the existing formulae are often invalid to predict. Almost all existing ST formulae assume that sediment transport can be fully determined by parameters in streamwise direction without parameters in vertical direction. Different from this assumption, this paper highlights the importance of vertical motion and the vertical velocity is suggested to represent the vertical motion. A connection between unsteadiness and vertical velocity is established. New formulae in unsteady flows have been developed from inception of sediment motion, sediment discharge to suspension’s Rouse number. It is found that upward vertical velocity plays an important role for sediment transport, its temporal and spatial alternations are responsible for the phase lag phenomenon and bedform formation. Reasonable agreement between the measured and the proposed conceptual model was achieved

Absence of collapse in quantum Rabi oscillations

We show analytically that the collapse and revival in the population dynamics of the atom-cavity coupled system under the rotating wave approximation (RWA), valid only at very weak coupling, is an artifact as the atom-cavity coupling is increased. Even the first-order correction to the RWA is able to bring about the absence of the collapse in the dynamics of atomic population inversion thanks to intrinsic oscillations resulting from the transitions between two levels with the same atomic quantum number. The removal of the collapse is valid for a wide range of coupling strengths which are accessible to current experimental setups. In addition, based on our analytical results that greatly improve upon the conventional RWA, even the strong-coupling power spectrum can now be explained with the help of the numerically exact energy levels.Comment: 21 pages, 3 figure

Flow resistance and bed form geometry in a wide alluvial channel

This paper explores the underlying mechanism of flow resistance in a wide alluvial channel with bed forms. On the basis of published data, it is shown that the grain roughness can be taken as equal to 2 times the median diameter of the bed sediment. An empirical equation for the bed form roughness has been proposed, and it depends on the bed form height and bed form steepness. The influence of the bed form length and height on the total bed shear stress and energy slope is deliberated, and empirical expressions for the length of the separation zone behind the bed forms are also proposed. The study proposed an equation to compute the total bed shear stress as a function of the grain and bed form roughness as well as the important role of the bed form geometry in the overall flow resistance in alluvial channels. The model is tested and verified against 670 flume measurements and 1540 field observations. The computed and measured energy slopes are in good agreement with close to 71% of all data sets within the ±20% error band