Journal ArticleDOI
Turbulent Structure in Unsteady Depth-Varying Open-Channel Flows
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In this paper, velocity measurements in the viscous sublayer of highly unsteady flow have been first conducted to evaluate the friction velocity independently of the log-law, and the von Karman constant κ was calculated using this friction velocity.Abstract:
Turbulence measurements over a smooth wall in unsteady depth-varying open-channel flows were conducted by the simultaneous use of a two-component laser Doppler anemometer (LDA) and a water-wave gauge. In the present study, velocity measurements in the viscous sublayer of highly unsteady flow have been first conducted to evaluate the friction velocity independently of the log-law. The von Karman constant κ was calculated using this friction velocity. It was proven then that the value of κ was really a constant of 0.41 even in unsteady open-channel flows. Next, statistical structures of mean velocity and turbulence characteristics were investigated across the whole flow from the near-wall region up to the free surface. In particular, turbulence measurements near the depth-varying water-surface zone of flood flow were conducted successfully for the first time with the LDA; such measurements have been impossible with conventional velocity instruments such as hot-film anemometers. Mean velocity profiles and turbulence characteristics were revealed in both the rising and the falling stages of the flood period.read more
Citations
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Journal ArticleDOI
Open-Channel Flow Turbulence and Its Research Prospect in the 21st Century
TL;DR: Open-channel turbulence has been studied extensively in the literature as mentioned in this paper, where the concept of local isotropy has proved useful in understanding these flows, such as those in open channels, boundary layers, and pipes.
Journal ArticleDOI
Simulation of sediment transport during flood events: laboratory work and field experiments
TL;DR: In this article, a fundamental understanding of the suspended load transport of river sediment in unsteady flow was initiated by using laboratory erosion tests as well as artificial flood experiments to evaluate the influence of the transient regime on the transport efficiency of the flow.
Journal ArticleDOI
Dam break – Outburst flood propagation and transient hydraulics: A geosciences perspective
TL;DR: In this article, the authors provide experimental data to test hypotheses concerning the effect of a series of external controls on resultant longitudinal flow propagation and transitory hydraulics, including the height of the lock gate raise, bed roughness and suspended sediment concentration.
Journal ArticleDOI
Turbulence Characteristics in Supercritical Open Channel Flows: Effects of Froude Number and Aspect Ratio
TL;DR: In this paper, the instantaneous streamwise and vertical flow velocities were measured in a laboratory flume over the entire width using a 2D-LDA system to determine turbulence intensities, and bed and Reynolds shear stresses.
Journal ArticleDOI
Sediment transport during flood event: a review
TL;DR: In this article, the authors evaluated state-of-the-art research efforts concerning flow characteristics and sediment transport in unsteady flow condition, and found that the methods which are based on steady flow conditions generally underestimate the sediment transport rates.
References
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Journal ArticleDOI
Open‐channel Flow Measurements with a Laser Doppler Anemometer
Iehisa Nezu,Wolfgang Rodi +1 more
TL;DR: In this article, it was shown that the log-law can be applied strictly only to the nearwall region and the von K´rm´n constant κ and integral constant A are truly universal, having values of κ=0.412 and A=5.29 irrespective of the Reynolds and Froude number.
Journal ArticleDOI
Turbulent oscillatory boundary layers at high Reynolds numbers
TL;DR: In this paper, the free-stream flow is a purely oscillating flow with sinusoidal velocity variation, and mean and turbulence properties were measured mainly in two directions, namely in the streamwise direction and in the direction perpendicular to the bed.
Book
Open Channel Hydraulics
TL;DR: The concept of fluid flow energy principle, the momentum principle development of uniform flow concepts, and the analysis of gradually and spatially varied flow design of channels flow measurement rapidly varied flow in non-prismatic channels turbulent diffusion and dispersion in steady open-channel flow turbulent, buoyant, surface jets and associated phenomena gradually varied, unsteady flow rapidly varied, unstable flow hydraulic models.
Journal ArticleDOI
Experimental and numerical study of a turbulent boundary layer with pressure gradients
TL;DR: In this article, an experimental and numerical study of a turbulent boundary layer with pressure gradients was conducted using the recent "fringe method" with its numerical advantages and good inflow quality.
Journal ArticleDOI
An investigation of transition to turbulence in bounded oscillatory Stokes flows Part 1. Experiments
TL;DR: In this paper, the authors used a two-colour laser-Doppler anemometer to measure Axial and radial velocity components of turbulent flow in a circular pipe for the range of Reynolds numbers Reδ = U0δ/ν (U0 = amplitude of cross-sectional mean velocity, δ = (2ν/ω)½) = Stokes layer thickness) from 550 to 2000 and Stokes parameters Λ = R/δ (R = radius of the pipe) from 5 to 10.