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Fundamental Concepts of Flow
Published in Jesse Yoder, New-Technology Flowmeters, 2023
Flow velocity is a measurement of how fast the flow is moving per unit of time. A common Imperial (American) unit for measuring flow velocity is feet per second. A common SI (metric) way to measure flow velocity is meters per second.
Sources of Water Supply
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
The intake pipe connecting the intake well with the jack well is usually of a non-pressure type and is laid on a gentle slope. Flow velocity in an intake pipe should not exceed 1.2 m/s. The ends of the pipes are fixed with strainers. The water is drawn into a jack well and then pumped to the purification works. This is a cheap and simple arrangement. Water entering a jack well is pumped to the treatment works. Jack wells should be founded on hard strata.
The Groner-membrane: a hydraulic superconductor for rough tunnels?
Published in Bjørn Honningsvåg, Grethe Holm Midttømme, Kjell Repp, Kjetil Arne Vaskinn, Trond Westeren, Hydropower in the New Millennium, 2020
To control the internal pressure there is a contraction made from steel, at the entrance of the flexible pipe (figure 3). As the flow velocity increases through the contraction, the pressure drops. The low pressure inside the contraction is transmitted to the outside of the flexible pipe through holes in the wall of the contraction. After passing the contraction the flow expands as it enters into the flexible pipe, the velocity decreases and the pressure increases accordingly, while the water outside the pipe maintains the same low pressure as in the contraction. A similar device is installed at the downstream end of the flexible pipe. The result is a constant and controlled pressure difference across the wall of the flexible pipe, even if the pipe is several kilometers long. What makes this solution unique is that the pressure fluctuations due to turbulence always is proportional to the inner pressure.
Erosion time scale in pipes below dikes for turbulent and laminar flow
Published in Journal of Hydraulic Research, 2023
A laminar flow occurs when the fluid flows in parallel layers, with no disruption between those layers. Stokes’ law of friction describes the drag force acting on a spherical body around which a laminar flow passes. Usually drag coefficients (CD) are determined based on the terminal settling velocity of particles. Recently, Wu and Wang (2006), also see Hofstra et al. (2010), presented an overview of drag coefficients for different particle shape factors. The result of their research is reflected in Fig. 3, which shows CD as function of Re,part for natural sands and gravel. When viscous stresses dominate, i.e. if Re,part < 10, the drag coefficient is: A turbulent flow is characterized by irregular variations in pressure and flow velocity. Based on the measurements of Engelund and Hansen (1967), the asymptotic value of CD for Re,part > 100 is about 1.5. For uniform flow, the mean relative turbulence intensity (r0) is (Hoffmans, 2012): where k0 is the mean turbulent kinetic energy, ρ is the density of water and τ0 is the bed/wall shear stress. In rivers, r0 varies from 0.05 (hydraulically smooth bed) to 0.15 (hydraulically rough bed), and in mountain rivers or in steep channels, r0 is about 0.5 (range: 0.2–0.8), which is extremely high. In these flows, bed turbulence is largest. In non-uniform flows, e.g. at bridge piers, abutments and/or sills, turbulence is generated because of the geometry of hydraulic structures.
Establishment of analytical-numerical method to determine the water level in the railway ballast layer contaminated with sandy material
Published in European Journal of Environmental and Civil Engineering, 2021
Darcy’s law provides a linear relationship between flow velocity and hydraulic gradient for water flow through permeable media by assuming laminar flow condition. Based on the proposed law, the relationship is expressed by Equation (3) (Darcy, 1856): Flow velocity (cm/s)