Showing papers in "Journal of Hydraulic Research in 1989"
TL;DR: In this article, a generation mechanism for secondary currents in closed and open channel flows can be explained by using the longitudinal vorticity equation, which is used to explain the secondary motions in open and closed channel flows.
Abstract: Secondary currents are generated and modified as a result of the anisotropy of turbulence, which is caused by the boundary conditions of the bed, the side-wall and the free surface, as well as the aspect ratio of the channel and the channel geometry. Secondary currents affect the primary mean flow, producing threedimensional structures. Such a generation mechanism for secondary currents in closed and open channel flows can be explained well by using the longitudinal vorticity equation. The secondary motions in open channel flows are quite different from those in closed channel flows.
232 citations
TL;DR: In this paper, the structure of uniform flow in a smooth open channel is investigated and it is found that the universal law of the wall describes rather well the data over the entire channel depth (Fig. 2); in the core of the outer region (0.2 < y/d < 0.7), a wake of limited strength (Π ≈ 0.08) exists; in the near-surface zone (0.,7 < y /d < 1.0), a retarding effect, possibly due to weak secondary currents, tends to compensate the wake divergence
Abstract: Laboratory experiments on the structure of uniform flow in a smooth open channel are reported. Velocity profiles (Figs. 2 and 3) and turbulence intensity profiles (Fig. 6) as well as friction velocity (Table 2) were measured. It was found that: the universal law-of-the-wall describes rather well the data over the entire channel depth (Fig. 2); in the core of the outer region (0.2 < y/d < 0.7), a wake of limited strength (Π ≈ 0.08) exists; in the near-surface zone (0.7< y/d < 1.0), a retarding effect, possibly due to weak secondary currents, tends to compensate the wake divergence (Fig. 4), resulting in a modified distribution of the mixing length (Fig. 5).
173 citations
TL;DR: In this paper, the authors investigated the spatial lag effects of alluvial systems under bed load sediment transport conditions and proposed a numerical model to predict the spatial and temporal variation of the mean bed elevation and bed load transport rate under steady flow, non-equilibrium conditions.
Abstract: Spatial lag effects, which are viewed as the inability of an alluvial system to immediately overcome the presence of constrained sediment boundary conditions, are investigated under bed load sediment transport conditions. An equation which characterises spatial lag effects and two theoretical spatial lag coefficient relations are investigated experimentally. Values of the spatial lag coefficient obtained from experimental data are compared with the theoretical relations and one relation is recommended. A numerical model which incorporates the spatial lag equation is formulated. The performance of the model is tested against data measured by a previous investigator and the ability of the model to successfully predict the spatial and temporal variation of the mean bed elevation and bed load transport rate under steady flow, non-equilibrium conditions is verified.
124 citations
TL;DR: In this paper, the effect of wall friction on the sequent depths ratio in classical hydraulic jumps is analyzed based on experimental data, and an approach is presented by which it is seen that the infent depths are not only influenced by the inflow Froude number, but also by inflow Reynolds number, and inflow aspect ratio.
Abstract: The effect of wall friction on the sequent depths ratio in classical hydraulic jumps is analysed. Based on experimental data, an approach is presented by which it is seen that the sequent depths are not only influenced by the inflow Froude number, but also by the inflow Reynolds number, and the inflow aspect ratio. The prediction is compared to own and other experimental data, and a fair agreement between the two is found. Finally, an expression is given for the limit condition for which scale effects are still absent. All results are presented in terms of jump inflow quantities and thus ensure a simple application to design problems.
121 citations
TL;DR: In this paper, a numerical model for simulating the flow and the settling performance of primary clarifiers is presented, which consists of two parts: a flow model providing the velocity and turbulent viscosity/diffusivity field and a suspended-sediment transport model for determining the particle concentration field.
Abstract: A numerical model is presented for simulating the flow and the settling performance of primary clarifiers. The model consists of 2 parts: a flow model providing the velocity and turbulent viscosity/diffusivity field and a suspended-sediment transport model for determining the particle concentration field. The model is an improvement over simple algebraic relations and previous numerical models because, with the aid of the k-e turbulence model employed, it allows a more realistic prediction of the velocity and turbulent diffusivity distribution, and also because it accounts for differential settling by solving concentration equations for individual fractions of different particle sizes. The model is applied to calculate the flow field, the flow through curve and the suspended solids concentration field in the primary settling tank of the City of Sarnia, Ontario, Canada for various overflow rates and settling velocity curves. In spite of the geometric simplifications employed in the model the concentration ...
97 citations
TL;DR: In this article, the performance of a spillway aerator is studied on a steep spillway model with high velocities and new air concentration and velocity measurements are performed, and the behavior of the air demand relationship between the air discharge and the subpressure in the cavity beneath the nappe is analyzed.
Abstract: Cavitation erosion damage to spillway surfaces may be prevented with the use of aeration devices (aerators) introducing air in the layers close to the channel bottom in order to reduce cavitation damage. The performance of a spillway aerator are studied on steep spillway model with high velocities (from 4 m/s up to 15 m/s) and new air concentration and velocity measurements were performed. The data are presented and analysed developping new equations. The behaviour of the air demand relationship between the air discharge and the subpressure in the cavity beneath the nappe is analyzed. All these results provide a better understanding of the air entrainment processes above a spillway aerator and the quantity of air entrained can be obtained. Experimental data at the impact point of the jet are shown. The results indicate a strong deaeration process occuring in the impact region and reducing the effect of the aeration occuring above the aerator.
90 citations
TL;DR: In this paper, Beam and Warming implicit Unite difference schemes are introduced to integrate the equations describing the two-dimensional unsteady free-surface flows, allowing sharp discontinuous initial conditions, and do not require isolation of a bore.
Abstract: Beam and Warming implicit Unite difference schemes are introduced to integrate the equations describing the two-dimensional unsteady free-surface flows. These schemes are second-order accurate in space and time, allow sharp discontinuous initial conditions, and do not require isolation of a bore. Subcritical and supercritical flows may be present indifferent parts of the channel or they may occur in sequence. Depending upon the Courant number used in the computations, sharp discontinuities may be slightly smeared since they are not isolated. Different procedures for incorporating the boundary conditions are discussed. The analysis of two-dimensional unsteady free-surface (lows resulting from the breaking of a dam are presented to illustrate the aplication of the methods.
74 citations
TL;DR: In this paper, the main features of the highly anisotropic turbulence in the region of vanishing shear near the free surface of two-dimensional channel flow have been calculated using a Reynolds-stress transport model with surface effect terms in the pressure-strain-rate correlation.
Abstract: The main features of the highly anisotropic turbulence in the region of vanishing shear near the free surface of two-dimensional channel flow have been calculated using a Reynolds-stress transport model with surfaceeffect terms in the pressure-strain-rate correlation. The form of these terms is identical for solid and free surfaces. For a free surface, however, the surface-proximity function is an order of magnitude greater than the function for a rigid surface.
62 citations
TL;DR: In this article, a directional wavemaker theory for wave basins with sloping bottoms and reflective sidewalls is presented, which includes the refraction, shoaling and diffraction that occur in wave basin with the wavemaker mounted along one end of the basin.
Abstract: A directional wavemaker theory is presented for waves in wave basins with sloping bottoms and reflective sidewalls. The theory includes the refraction, shoaling and diffraction that occur in wave basins with the wavemaker mounted along one end of the basin. A procedure is shown which utilizes the reflection from the sidewalls to produce planar wave trains at a given location in the basin, similar to that which would be obtained by an infinitely long wavemaker.
61 citations
TL;DR: In this article, a study of the flow downstream of a spillway aerator was performed on the Clyde dam spillway model and a comparison between the free-surface aeration and the downstream of an aerator is developed.
Abstract: Cavitation erosion damage to spillway surfaces may be prevented with the use of aeration devices (aerators), introducing air in the layers close to the channel bottom. A study of the flow downstream of a spillway aerator was performed on the Clyde dam spillway model. The results are presented and a comparison between the free-surface aeration and the flow downstream of an aerator is developed. Such a method enables to compute the flow parameters at any point downstream of an aerator, in particular the air concentration near the spillway bottom. The computed results are compared with experimental data. This analysis contributes to a method for the determination of aerator spacing and aerator location.
59 citations
TL;DR: In this paper, the formation of ripples on an erodible sand bed by varying the roughness, the mass density of the uniform grain material and the history of the bed evolution was investigated.
Abstract: Experiments in an open channel were conducted to investigate the formation of ripples on an erodible sand bed by varying the roughness, the mass density of the uniform grain material and the history of the bed evolution. A first set ofexperiments was conducted by gradually increasing the slope in small increments from a value at which no transport occurred to one at which ripples started forming. In a supplementary set. the same slope change was achieved rapidly in a single step. Visualizations showed that two types of ripple formation exist, depending on how fast the slope rate was increased. A third type is observed for fine and heavy bed material (lead) at high bed load transport. The results can be interpreted by using a coherent structure model for the turbulent flow. In the framework of such a concept, the initial disturbances can be interpreted as transport relics of so-called sweep events, and the initial wave length is related to the sweep “periods”.
TL;DR: In this paper, the nonlinear viscous oscillatory flow over a wavy wall of small amplitude ∊∗ is determined and an independent analysis for small values of a ∗/L ∗ is performed and the results of the two approaches have been successfully compared.
Abstract: The non-linear viscous oscillatory flow over a wavy wall of small amplitude ∊∗ is determined. The solution holds for arbitrary values of a ∗/L ∗ (a ∗ is the amplitude of fluid oscillations near the wall and L ∗ is the wavelength of wall perturbation); previous works of Lyne [1], Kaneko and Honji [2] on the subject are thus extended. An independent analysis for small values of a ∗/L ∗ is performed and the results of the two approaches have been successfully compared. The form of the steady streamings set up in addition to the oscillatory motion by the bed profile is analyzed for different values of the parameters of the problem. The relevance of the results to the study of ripples formation at the bottom of sea waves is discussed.
TL;DR: In this paper, the internal flow features of hydraulic jumps in trapezoidal channels are explored based on 3D observations, and it is shown that the flow phenomena significantly differ from the classical hydraulic jump, particularly attributed to the presence of a bottom roller.
Abstract: The internal flow features of hydraulic jumps in trapezoidal channels are explored. Based on 3-D observations, it is shown that the flow phenomena significantly differ from the classical hydraulic jump. This is particularly attributed to the presence of a bottom roller. The main flow properties such as the sequent depths, the spatial extension of the bottom roller, and the length characteristics are analysed. Further, typical jump instabilities are discussed. Finally, some design recommendations are presented.
TL;DR: In this article, the authors consider the superposition of two potential-flow motion fields, endowed with singularities of helicoidal shape, in the form of a helicoidal vortex and a uniform distribution line source.
Abstract: The phenomenon under consideration is represented as the superposition of two potential-flow motion fields, endowed with singularities ofhelicoidal shape. In the first field the singularity is a helicoidal vortex (i.e. the circulation around it is finite); in the second one the singularity is a uniform distribution line source, sinusoidally pulsating in time. If the draft tube is rectilinear, the solution pertaining to the first field adequately represents the "rotating perturbation field", devoid of any synchronous component: it is not necessary in this case to assign a finite amplitude to the second flow field. If the draft-tube rectilinear stretch is followed by an elbow, qualitative considerations show that a synchronous component must needs arise. If, moreover, the vortex rope is cavitated, the linear combination (with suitable amplitudes) of the two flow fields allow the total perturbation field to be represented (rotating+ synchronous components). Obviously, a certain number of compatibility condit...
TL;DR: In this article, the authors considered the occurrence of a submerged hydraulic jump in a low head canal regulating structure with piers, where the jump dynamics is affected by the abrupt lateral expansion at the end of the piers.
Abstract: The occurrence of a submerged hydraulic jump in a low head canal regulating structure with piers is considered. The problem is three-dimensional because of the abrupt lateral expansion at the end of the piers. The jump dynamics is affected by this expansion, and this effect should be taken into account in calculating the hydraulics for the structure.
TL;DR: For a channel with a deep and a shallow region an eigenvalue-eigenfunction solution is obtained for the dispersion of effluent released in either the deep or shallow region.
Abstract: For a channel with a deep and a shallow region an eigenvalue-eigenfunction solution is obtained for the dispersion of effluent released in either the deep or shallow region. Each region is assumed to have a constant velocity and constant dispersion coefficient and the boundary condition at the discontinuity is the equality of mean concentration and concentration flux. The results are compared with experiments and are in qualitative agreement. Both experiment and theory show that if rapid initial dilution is important there is a great advantage in releasing the effluent in the deeper region.
TL;DR: In this paper, a theoretical analysis of the free-surface formation and the development of fine silt concentration caused by the influence of a prevailing combined vortex is presented, and similar similarity relationships for both parameters have been found to exist.
Abstract: A theoretical analysis of the liquid free-surface formation and the development of fine silt concentration caused by the influence of a prevailing combined vortex is presented. Similarity relationships for both parameters have been found to exist. Burgers' vortex has been used to derive approximate formulae for the free-surface and the concentration profiles. Finally, using the present analysis, values for the diffusion coefficient have been calculated.
TL;DR: In this article, the authors presented a mathematical model for the damping of flow and pressure in the water hammer phenomenon, taking into account the dynamic structure of water column motion in a pressurized pipe for a compressible fluid, as well as the energy losses in the elastic walls of the pipe.
Abstract: The Darcy-Weisbach formula, used in the majority of mathematic models for calculating the head losses in the unsteady motion of water does not simulate with sufficient accuracy the damping of flow and pressure in the water hammer phenomenon Taking into account the dynamic structure of water column motion in a pressurized pipe, for a compressible fluid, as well as the energy losses in the elastic walls of the pipe, we present for the calculation of the flow and pressure oscillation damping a formula based on the structural (hysteretic) friction forces [6, 13] In the case of elastic bodies the structural damping forces are proportional to the elastic forces, but a quarter of a period phase out By putting into practice the presented formula a good agreement between computations and experimental measurements is achieved
TL;DR: The devices employed for the measurement of discharges in free surface channels usually generate a great headloss, making them unsuitable for irrigation purposes in flat areas as discussed by the authors, and to solve this problem, the au...
Abstract: The devices employed for the measurement of discharges in free surface channels usually generate a great headloss, incompatible with irrigation purposes in flat areas. To solve this problem, the au...
TL;DR: In this paper, an experimental investigation on regular wave induced forces on a smooth submarine pipeline fixed horizontally near a simulated seabed is carried out in the inertia dominated regime, where a simple poten...
Abstract: An experimental investigation on regular wave induced forces on a smooth submarine pipeline fixed horizontally near a simulated seabed is carried out in the inertia dominated regime. A simple poten...
TL;DR: In this paper, the authors present the results of an experimental investigation on the behavior of Von-Karman coefficient in sediment laden flow in straight and in curved reaches of smooth rectangular rigid boundary open channels.
Abstract: The paper presents the results of an experimental investigation on the behaviour of Von-Karman coefficient in sediment laden flow in straight and in curved reaches of smooth rectangular rigid boundary open channels. The investigation shows the effect of varying the Reynolds number of sediment laden flow, the suspended sediment concentration in the flow, the radius-breadth ratio of the channel, and the central angle of the bend.
TL;DR: In this paper, a theoretical analysis of system singularities and normalized equations describing the water-level motion in the throttled surge tank of a hydropower plant are solved on a digital computer.
Abstract: After a theoretical analysis of system singularities, and normalized equations describing the water-level motion in the throttled surge tank of a hydropower plant are solved on a digital computer. The critical stability conditions for large amplitude oscillations are obtained by finding the conditions under which the initial state point of the system is, in the terminology of the phase plane method, on the limit cycle. The paper demonstrates the possibility of the existence of 2 limit cycles around the singularity representing the steady operating point and the feasibility of the adoption of surge tanks with a section smaller than Thoma critical value.
TL;DR: In this article, the authors present analytical solutions which enable us to predict the transport of sediments: a total sediment load equation is developed, based on balance power, and a comparison is made of several total load formulas with flume data.
Abstract: All important sediment transport formulas have an empirical approach. This paper presents analytical solutions which enable us to predict the transport of sediments: A total sediment load equation is developed, based on balance power. The equations are relatively simple and the procedure for calculation has been facilitated by means of graphs. Shield's and Duboys' formulas were obtained from the concepts established by deducing the proposed equation; also, a formula similar to those of Yang's unit stream is deduced. A comparison with the data from several flumes and rivers indicates that the proposed equations are accurate. Also, a comparison is made of several total load formulas with flume data.
Journal Article•
TL;DR: In this article, the LCH-ARTICLE-1989-010 Record created on 2007-04-24, modified on 2016-08-08, was used as a reference.
Abstract: Note: [101] Reference LCH-ARTICLE-1989-010 Record created on 2007-04-24, modified on 2016-08-08
TL;DR: In this article, the mean and fluctuating pressures on various geometries of vertical-lift gates have been measured and analyzed and the influence of various hydraulic parameters and the magnitude of the gate opening on mean and r.m.s. pressure fluctuations and their spatial correlations has been investigated.
Abstract: Mean and fluctuating pressures on various geometries of vertical-lift gates have been measured and analysed. The influence of various hydraulic parameters and the magnitude of the gate opening on mean and r.m.s. pressure fluctuations and their spatial correlations has been investigated. The variations in the distribution pattern, spatial correlations and intensity of pressure fluctuations have been studied when the gate is forced to vibrate with a single degree-of-freedom in the vertical direction at specified frequencies and amplitude. Total intensity of fluctuating pressures on vibrating gates has been obtained by integrating the r.m.s. pressure fluctuations over the gate thickness. The distinct peak in the total intensity of fluctuating pressure on the gate indicates the presence of a dominant frequency which is considered to be the critical condition for the design of hydraulic control gates.
TL;DR: In this article, a model runner for a 6-nozzle Pelton turbine was used to visually observe the interference in buckets and jet disturbance outside of buckets, and the visual observation revealed that the jet from...
Abstract: Jet interference in buckets and jet disturbance outside of buckets have been visually observed in a model runner for a 6-nozzle Pelton turbine. The visual observation has revealed that the jet from...
TL;DR: In this paper, the influence of conduit slope is considered, including very steep slopes (up to 30%), and experimental observations were made for a wide range of Froude numbers and slopes, and non-dimensional design curves are provided.
Abstract: The case of a hydraulic jump in a closed conduit with pressure flow downstream from the jump has been investigated for horizontal conduits by a number of researchers. In the research reported herein, the influence of conduit slope is considered, including very steep slopes (up to 30%). The theoretical analysis of this case does not lead to a direct solution for jump height because there are too many unknowns in the equation. Accordingly, experimental observations were made for a wide range of Froude numbers and slopes, and non-dimensional design curves are provided.
TL;DR: In this paper, an empirical equation has been developed for rate of bed-load transport based on shear stresses, bed friction coefficient and particle properties, which is in a form suitable for use in the study of estuaries and coasts.
Abstract: An empirical equation has been developed for rate of bed-load transport based on shear stresses, bed friction coefficient and particle properties. It has been calibrated by using laboratory and field data covering a limited range of sediment sizes (from fine non-cohesive silt up to a median size of 1.4 mm) and has been shown to apply to streams transporting sediment of median size up to 300 mm. Development of this equation followed the lead given by Bagnold (1980, 1986) and extended his work so that it can be applied to unsteady flows. It is in a form suitable for use in the study of estuaries and coasts. The parameters in the equation can be obtained in the field without great difficulty.
TL;DR: In this paper, a dimensionless parameter is proposed for representing the intensity of turbulent interaction and is used as the independent variable to develop a model for predicting the shear stress profile on the bed of a flood plain.
Abstract: Experiments in a flume with a compound section are described, in which lateral shear stress profiles were measured for various flow depths and inclinations of the main channel bank. General forms of bed shear stress profiles on the flood plain are described and the dependence of the turbulent interaction between channel and flood plain flows on flow depth and on the inclination of the main channel bank is examined. A dimensionless parameter is proposed for representing the intensity of turbulent interaction and is used as the independent variable to develop a model for predicting the shear stress profile on the bed of a flood plain. Equations are presented for predicting the value of this independent variable.
TL;DR: In this article, a plunging density current in a diverging horizontal channel is analyzed using a two-layer non-miscible flow model, and the equations governing the flow are presented.
Abstract: Flow of a plunging density current in a diverging horizontal channel is analyzed using a two layer nonmiscible flow model. The equations governing the flow are presented. Interface profiles that can exist are identified, and the behavior of the flow densimetric Froude number at the plunge line is investigated. The theoretical results are compared with experimental data.