The paper presents the behavor of sedimentladen negative buoyant plume issued vertically into uniform flow. Special attention is paid on the effect of settling particles on plume motion. Experimental and theoretical studies were made on the variations of plume properties, such as plume trajectories, grouth of width and decay of concentration and velocity. The path of maximum velocity was pulled down due to settling of sediments and there found a vertical gap between the path of maximum cocentration and maximum velocity. Except these features, the plume motion was almost the same as that of non-settling matter.

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Laboratory experiments were performed to study the upward liquid volume flux of two-dimensional bubble plumes in homogeneous and linearly stratified environments. The liquid volume flux in homogeneous ambients was scaled with the buoyancy flux, the elevetion above the bubble source, and the effect of slip velocity of bubbles. The deficit of buoyancy flux in stratified environments was similarly parameterized with stratification intensity. With using these two fluxes, a simple formulae of liquid volume flux was obtained for both of homogeneous and stratified environments.

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A numerical simulation is performed on a bubble plume, a typical gas-liquid phase flow, for extending the applicability of GAL-LES model, which has been recently developed by the authors for multiphase turbulent flow. The GAL-LES model has succeeded in simulating the essential features of large-eddy structure, which is found to be appreciably affected by the bubble concentration at the inlet slot, giving quantitatively good agreements with the previous experimental results.

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Hydraulic gradients in a circular conduit with a hydraulic jump were investigated by experiments. It was made to confirm the results presented by Kalinske et. al. on closed conduit flow, and to establish a set of formula in determining the location and height of the jump. The experimental observations were conducted in three cases, i. e. 1) steady hydraulic jumps with different lengths, 2) moving hydraulic jumps due to pressurized flow coming from the inlet of the conduit and 3) the alternate flow of full flow and partly-full flow. Observation results on the hydraulic grade line of flows in the conduit, which are different from the previous researches, are discussed

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A numerical model for the transition from partly full to completely full flow is developed to predict flow pattern in a steep circular conduit with a bell mouth at the inlet. The boundary and initial condition of the full/partly-full interface, and its pattern of propagation downstream with the increase of flow speed are discussed in this paper, taking into consideration the two downstream end conditions, i.e. free and choked. The numerical calculation is carried out and its prediction is compared with experimental data.

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Hydraulic characteristics of vortex flow dropshaft with contraction which is aimed to deal with energy dissipation and deaeration adequately are treated. Through the experiment, it is clarified that this structure has the effect of diminishing air entrainment. Next, free surface swiring flows passed through contraction are modelled and analyzed. The swirling flows are governed by the two nondimensioal numbers, the circulation number and the Froude number. Some results of practical use are also presented.

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It has been pointed out that, for surcharged flow simulations in urban drainage sewer pipe systems, manholes are very important runoff elements that govern the pressure-wave celerity of the surcharged flow.
In the first half of this paper, a lumping-method of manhole cross-sectional areas is presented. In this method, areas of some manholes are concentrated at the area of an adjacent manhole: manhole areas are never ignored but lumped.
In the later half, the usefulness of the method is demonstrated through numerical simulations with a prismatic sewer pipe system and SWMM-EXTRAN.

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The model scale effect in the vortex experiments cannot be avoided due to the influence of the viscosity.
In this study we evaluated quantitatively the scale effects in the model experiment of the intake vortex using five kinds of scale model, and therefore we propose a new experimental method.
As a result, when we experiment with the intake vortex in Froude model, the method correcting water viscosity by water temperature control is effective for adequate evaluation of the scale effect.

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To promote time and effort savings and to increase efficiency in experimenting with water-flow installations, the practical use of numerical simulation has been studied. The velocity distribution at the intake structure of hydraulic model, was compared using numerical simulation data and one dimentional LDA measurements. The numerical simulation data of the velocity distribution just downstream of the channel curve in the gradually widening of the channel was in good agreement with the results obtained by measurement except the area of strongly unsteady flow

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A study was made on generated field with no air core vortex above the vertical outflow in a tank, based on the theoretical and experimental considerations.
This air core vortex was found to be affected by the inertial, viscous and surface tension forces. And thus there were examined using the dimensionless radial Reynolds number, Rr, and dimensionless radial Weber number, We. In terms of these numbers, it was found that the limitations of the core vortex could be clearly defined.

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Although self-excited sloshing phenomena of free surface are sometimes observed in an outlet pit of electric power plants, the onset mechanisms are not clearly understood. Numerical analysis based on two dimensional geometry was conducted to evaluate such phenomena using moving grid transformation method. In the analyses, third order finite difference scheme is used for discretization of convective terms in momentum equations describing flow behavior, while boundary conditions at moving free surface are completely modeled considering surface tension and shear forces. Finally, it was shown that the analysis can simulate the self-excited phenomena due to internal flow depending on Froude and Reynolds numbers.

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Hydraulic characteristics of unsteady flows were investigated experimentally in compound channels with vegetated flood plains. Some noticeable differences between unsteady flow structure in compound channels with and without vegetation were revealed. The vegetation in the flood plains increases the unsteadiness of the main-channel velocity and its double peek property is changed by the effects of vegetation arrangement. During the rising stage, the velocity in the vegetation does not reach the value in the steady flow case so that the lateral velocity gradient and the turbulence intensity increase near the vegetation interface. Lastly, 1-D numerical calculation technique for unsteady flow with vegetation in flood plains was investigated.

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It is well known that large scale horizontal vortices occur between the flood plain and the main channel in a compound open channel flow. The momentum transport in the transverse direction by the vortices affects the resistance to flow in rivers during flood. The numerical method based on the plane two-layer model is proposed in order to simulate the flow in a compound open channel with a rectangular main channel. The horizontal and vertical structure of the flow due to the horizontal vortices is examined through the comparison of numerical results to the laboratory tests by Ikeda et al.

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In compound open channels, a shear instability generates large horizontal vortices at the junction between the main channel and the flood plains, so that a pair of vortex streets are formed near the both junctions. Stability of horizontal vortices is studied in terms of shear instability and Karman's vortex streets. It was found from the experiment that the interaction between the main channel and the flood plain becomes strong at some intermediate width of the main channel. The vortices are unstable when the width of main channel is comparable with the depth of the main channel.

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3-dimensional flow structure in meandering channels during flood is discussed based on the velocity measurements results by 2-component fiber optic laser Doppler anemometer. Growth and decay processes of secondary flow cells in meandering channels and their differences between before and alter inundation are particularly highlighted. Interaction between the lower layer flow (the main channel), and the upper layer flow (the flood plain) is also stressed. The matters pointed out in the paper are: closely related to the energy loss mechanism in compound meandering flows and should therefore properly be estimated in mathematical or numerical methods for engineering purposes.

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Based on a numerically-generated boundary-fitted orthogonal curvilinear coordinate system, a 2-layered, 2-d mathematical model for unsteady flows with complicated boundaries is presented. It is employed to evaluate the change of flow patterns such as water surface level, velocity vector, Lagrangian pathline and friction factor in sinegenerated meandering compound channel in terms of water depth ratio between in main channel and in flood plain. It is concluded that the over-bank flow is impacted severely by the meandering main channel flow when the flow depth on flood plain is shallow, and is almost independent of that when h_u/h_i is greater than 0.9, except the super-elevation of water surface due to the meandering in-bank flow. The bulk friction factor (for f/8C_f, ) changes with h_u/h_i very interestingly.

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Laboratory experiments were performed to study the effects of meandering vegetation zone along alternate sandbars. It is shown that the flow structure consists of horizontal free sheer layer along vegetated zone and secondary currents in meandering flow. Momentum transfer due to turbulence and that due to secondary currents were compared, which indicates importance of the latter.

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Numerical analysis based on k-ε turbulence model is applied to complicated flows in stream-type fishways: Denil type, superactive-type bottom baffles and Alaska steeppass. In these fishways, the hydraulic resistance and cellular motions are controlled by obliquely arranged fins, and the effect of fins are represented by adding the terms of the longitudinally averaged drag and turbulent energy production corresponding to the workdone by the drag to the governing equation of flow. The present model can describe the outline of the flow behavior in various fishways of stream-type.

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The hydraulic characteristics of an ice-covered river is much different from those at other seasons, because the frictional resistance between water surface and icesheet increases due to the ice cover on the water surface.
Accuracy of estimation of the average velocity is dependent on the velocity profile. Usually, the k-ε model is used to estimate the velocity profile under ice cover. This paper verifies a new estimation of a velocity profile under ice, the Two-Power LAW, using data measured in Hokkaido.

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Two velocity components of subsurface flow, observed in a rectangular wind tunnel basin equipped with a water circulation pump system, are measured over a vertical cross-section of the basin. Measurements are carried out for three cases: 1) reference wind speed U_a=8.4m/s without water current; 2) U_a=8.4m/s with current velocity U=10cm/s; and 3) U_a=8.4m/s with current velocity U=-10cm/s. A pair of secondary circulations is observed in a cross-section of the flow in the basin for each case: in the case-1 and case-3, a downwelling zone is found along the sidewall and an upwelling zone in the centre of the basin; and in the case-2, an upwelling zone is found along the sidewall and a downwelling zone in the centre of the basin. It is estimated that the velocity of the secondary circulations would be about 7-50% of the mainflow velocity.

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Unsteady flows were generated over smooth and rough, wavy beds in a wind tunnel with the section of 80cm×80cm and length of 820cm. Seven waves were placed in the tunnel and the measurement was carried out over the sixth bed. Longitudinal and vertical velocity components were measured with a X-type hot-wire anemometer at 9 sections over the wavy beds. For all the sections, the velocities were taken from the bed surface to the top of the tunnel. At each point, the measurements were repeated 5 times. The large volume of data obtained are used to calculate the ensemble-mean velocities as well as the Reynolds stresses.

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It is very important to examine the effects of pressure gradient on the turbulent structures. In the present study, accurate FLDA measurements over wavy bed have been conducted in open-channel flows. The pressure gradient parameter p⁺ obtained in this study was compared with that of air duct flows. The friction velocity was accurately determined even in the pressure-gradient flows with ‘viscous-sublayer’ formula, i. e., U⁺=y⁺. On the other hand, the velocity profiles of inner region have deviated largely from the universal velocity profile, i. e., U⁺=1/k·ln y⁺As, which dose exist in zero-pressure gradient flows. The distributions of turbulence intensities and Reynolds stress near the wall gradually changed form universal distributions.

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Turbulence measurements in and over the cavity of open-channel flows were conducted by making use of a two component fiber-optic laser Doppler anemometer (FLDA). Mean Structures in the cavity shear layer were examined in detail and it was revealed that the turbulent structures depended on the length of cavity significantly.
The visualization of coherent vortices was carried out by the use of dye injection techniques, and the characteristics of coherent and unstable vortices around separation point were clarified by means of unstable analysis. The fundamental frequency was determined and unstability of coherent vortices was examined.

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Flow fields of gradually contracted open channel flows are measured by a Hot-film anemometer. Mean velocity profiles of the inner and the outer region are well expressed by the log-wake law. The wake strength parameter H decreases in the flow direction, and shapes of Reynolds stress distributions are slenderized than the universal distribution for a 2-D uniform flow. The turbulence energy is transformed into the mean flow energy, because the region, where the value of turbulence production is negative, exists. The intensity of the secondary flow decreases in the flow direction.

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The three dimensional flow field of an open channel flow with a moderate adverse pressure gradient was measured by a Hot-film anemometer. It is found that the intensity of the secondary flow which normalized by a mean bulk velocity increases in the flow direction. The secondary flow affects on mean velocity profiles and friction velocity distributions. In particularly, as the intensity of the Reynolds stress increases in the flow direction, the production of turbulence energy is increased. Therefore, the intensity of the turbulence energy increases.

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Six different versions of low Reynolds number type κ-ε model including the original one by Jones and Launder are utilized to predict the velocity, turbulent kinetic energy and wall shear stress in case of an oscillatory boundary layer. A quantitative comparison is made to distinguish the most efficient model by virtue of the accuracy in prediction. The comparison with the experimental data shows that the versions having correct behavior near the wall may predict the flow parameter very well.

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Shallow open-channel flow with groins is a very important subject to be studied in hydraulics and river engineering as well as in fluid mechanics. In this kind of flow, horizontal separation eddies induced by the groins influence strongly the recirculating flow, the reattachment of separation flow, the transport of momentum and sediment, and so on. It is therefore necessary to understand the nature of the eddies. In this paper, an experimental study was conducted to investigate the properties of the eddies, including the period and phase velocity of vortex, reattachment of separation flow, etc. It is found that the scale of vortices is increased while they move downstream. The phase velocity of eddies is found to be kept to be constant. The characteristics of open channel flow with two-groins is also studied. The mass and momentum exchange velocities, the contour of the root mean-square of water surface fluctuation, etc., have been presented.

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The streamwise development of pairs of longitudinal vortices and their effects on the sediments were investigated experimentally for different vortex pair configuraions. Three-components velocity measurements have been made in an open channel flow with a vortex pair artificially generated by two delta vanes protruding from the flatbed. The experimental results showed that delta vanes produced sand ribbons and controlled the longitudinal vortices, the mean motion of the vortex centers qualitatively followed a vortex filament model and the vortices with the flow depth spacing indicated a significant interaction between them.

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It is one of the important subject in river planning works to predict flow field and bed topography in the region around spur-dikes. Especially, the qualitative understanding of the mechanism of sediment deposition produced by spur-dikes enables the effective design of spur-dike collocation. However, since various complex phenomena are coexisting in the neighborhood of spur-dikes, it is necessary to investigate which phenomenon is essential for the sediment deposition around spur-dikes. In this study, a detailed observation of flow and river bed material in an area including a spur-dike in an actual river is performed, and the mechanism of sediment deposition produced by spur-dike is discussed.

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In taking the discharge by the side weir in the river, the discharge is as large as possible comparing from weir width and the sediment discharge is as little as possible. The bed in front of the weir is made down by the slanting strips. And the following problems are investigated. 1) How long is the bed near the wall made down by the size of the slanting strips with relation to sediment diameter and shear stress. 2) How much is the sediment discharge decreased by the variation of the bed in front of the side weir. 3) How is discharge of the side weir varied by the slanting strips

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As a drastic countermeasure of reservoir sedimentation and turbid effluence over a long term, a bypassing tunnel system is proposed and studied. It can transport both bed load and suspended sediment without passing a reservoir. Two different scaled hydraulic model studies are executed to examine the properties of the bed load in the tunnel and the river bed variation near the entrance of it. Stability of the system on the sediment transport is also discussed through the experimental results.

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Measurements of three dimensional velocities of solid-liquid upflow in a vertical pipe were made by using an acoustic doppler velocimeter (ADV). The neutral plastic particles with the density of 1. 047kg/cm³ and the diameters of 1. 4mm, 0. 66mm and 0. 33mm were transported in a vertical pipe of 19cm inner diameter. The concentration of particles in the flow ranged from about 0. 055% to 1. 564%. It was found that the turbulence intensity of fluid increases with the increase of concentration and diameter of particles and lager than that of clear water flow at the same flow condition; while at the case of particle diameter 0. 33mm and concentration 0. 385%, the turbulence intensity decreases than that of a clear water flow at the same conditions.

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The behavior of particles in Gas-Liquid-Solid three-phase flow in a horizontal pipe was experimentally investigated. The behavior of particles was recorded with a high speed video camera and was analyzed with a X-Y coordinator. It was found that particles in a solid-liquid slug section were accelerated and transported. On the other hand, particles in a gas-liquid section remained at the same position. Lift-off angle of particles decreased with increasing the apparent mean velocity of solid-liquid mixtures.But, it increased with increasing the apparent air velocity. Keywords: part stationary bed, gas-liquid-solid

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Flow resistance and sediment transport for slip flow of sediment layer in a horizontal pipe are discussed experimentally, and following conclusions are obtained;Shear stress of bed surface of a sliding sediment layer can be estimated by the method of hydraulic radius dividion of the clear water flow section into two, for pipe wall and sediment wall. Conditions for occurrence of slip flow of sediment are explained by the relationship between energy gradient and thickness of sediment layer. The condition of incipient motion of slip flow can be estimated by equations of stable force balance.

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Solid particle velocities are observed experimentally in water slurries of solid particles slightly thinner or denser than water, and the dynamics of the mixture flows are investigated. Slip velocities given by the difference between the mean velocities of solid particles and water in a circular pipe are reported in the present study.

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This study deals with the effects of the sediment yield on topography of stream or river channels. In this paper, the result of study on propagation characteristics of river bed variation due to large scale sediment yield by using a synthetic sediment routine model in a mountainous river system is presented. After validating the model using the field measurement data, the result of some sets of computer simulations of river bed variation in the conditions of idealized severe sediment yields were carried out. The effects of various conditions of the simulations such as treatment of debris flow and location of observation point, and tendencies of river bed variation are discussed.

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The process of channel network formation is investigated experimentally. Experiments were conducted on the model slope with the artificial rainfall. Video analyses of these experiments enable us to clarify the mechanism of the network formation. The following are the key points;(1) this network formation is influenced by “rainfall intensity”, “infiltration intensity” and “slope gradient”, (2) erosion due to an overland sheet flow and the deposition of sediment mainly supplied by gully erosion are the foundamental process. The time variation of sediment yield from the downstream end of the slope was also investigated, and is seen to be correlated strongly with the progress of gullies.

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The sediment transport process on the steep slope caused by rainfall and its runoff process can be divided into two: I. process casused by rainfall impact and II. process by overland flow. However, it was very rare to deal with two processes simultaneously, and some equilibrium sediment disdcharge equations were proposed by emphasizing either of two processes. In this study, we have proposed a unified model which includes the effects of rainfall impact and overinad flow, and examined the validity of the model by the experiment. Especially, we clarified the contribution of the rainfall impact to the non-equilibrium process of sediment transport.

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Sediment runoff process in an actual small basin is discussed, based on the results of field survey and numerical analysis. In Nigorisawa river, a tributary of R. Mogami, a very active sediment runoff took place in June 1993 due to the erosion of debris produced by landslide. Numerical simulation is conducted in order to specify the sediment runoff and the characteristics of sediment movements along the river reach. The numerical results show that the flow discharge increases rapidly to a magnitude of several ten times of supplied water discharge due to the occurrence of debris flow, and the sediment transport rate and mode change from place to place according to the variation of bed slope and flow width.

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The sediment transport process on the slope caused by rainfall impact and overland flow is the fundamental phenomenon, and many sediment discharge equations were proposed. Though most of them are proposed for the uniform sand, they are usually used for the estimation of the total sediment discharge of sand mixtures which is one of characteristics of the natural slopes. In this study, we experimentally dealt with the armor coat and the fractional sediment discharge on the slope caused by rainfall impact. Next, in order to simulate the non-equilibrium process of sediment transport we have applied the stochastic model which includes the effect of the sediment pick-up rate by rainfall impact. Since the simulated results have explained the experimental results, the validity of the proposed model has been clarified.

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The relationship among the rate of sheet erosion loss E, slope length L, rainfall intensity I, slope S₀ and soil detachability parameter α is expressed in the form of E =α L^β₁ I^β₂ S₀^β₃ and α, β₁, β₂ and β₃ are determined by applying a runoff-erosion model for hypothetical plots. The experimental data obtained in nine field plots with different vegetal cover conditions in northeastern Brazil are used to test the proposed equation. The simulation results and a comparison among the results for different types of vegetal cover are presented.

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Scarcity of data in sediment budget for arid and semi-arid lands (ASAL) is a recognized fact despite their environmental fragility. There is therefore urgent need for exchange of current knowledge in this field for effective conservation. We present a comparison among published and proposed models for computation of sediment yield and transport due to rainfall runoff for a single storm by using data from 8 storm events of 1986 in Katiorin experimental basin which is located in a semi-arid area of Kenya. We categorize the models into black, grey and white box on the basis of their consideration for physical principles.

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In a mountainous river, there are many obstruction such as large rocks and bed slopes in a steep, so sub- and super-critical flow conditions coexist and bed evolution has 2-dimensional feature. The purpose of this study is to develop the method for calculating 2-dimensional bed evolution in mountainous river. In this paper, the bed evolution in the steep channel around contraction are investigated experimentally and numerically by means of a 2-dimensional simulation method based on MacCormack's time-splitting finite element scheme. The simulation results show fairly good agreement in bed evolution with experimental results, especially reproducing water way just downstream at the contraction.

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Present paper describes the origin of step-pool systems that is found in authors' flume experiments with gravel beds, and proposes guide lines for design of them basing on the formation mechanisms. Step-pools are generated due to the interaction of antidunes and three-dimensional surface waves (diagonal cross waves) on supercritical flow. When wave lengths of the antidunes and the water surface waves coincide with each other, the two dimensional undulation of antidunes turns out to be three dimensional one gradually and then the surface waves begin to be amplified. Through the sorting of bed material, the steps become strong instructure. Therefore, it is possible to consider that the generation condition of step-pools is the coincidence of wave lengths of antidunes and surface waves. By using the knowledge, guide lines for artificial construction of them is proposed.

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From the view points of ecology and landscape, it is very important for hydraulic engineers to understand hydraulic characteristics of riffles. We performed a field observation at a riffle of the Alci-river in Akiruno city in Tokyo on 25th August 1995. In the observation, flow velocity, fluctuations of velocity and water surface, temperature of water and dissolved oxygen were measured. It is found that an interaction between flow and channel-bed gravels is dominant in determining the texture of free surface in riffles.

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The experiment, for river confluences on alluvial streams at 45⁰ are undertaken. Two models with different conditions are carried out. Suitable mathematical models to simulate river confluence problems are designed. The experiment data are used to calibrate the mathematical models. The flow pattern, flow velocity vectors and bed configuration especially at the confluence region are studied comparatively with the experiment results. Each term of momentum equation for both fixed flat and movable bed are investigated along the main channel. The effect of eddy viscosity on flow pattern on the right side of main channel at the junction is considered. Finally satisfied results and good agreement between physical and numerical models are gained.

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Self-preserving profiles have been observed in experimentally produced onedimensional deltas. We analytically derive such a self-preserving profile from the St. Venant shallow water equations and the continuity equation of sediment, giving profiles of concave form. The theory predicts that the increasing height of the delta front decelerates the migration of the front and reduces the gradient of the longitudinal profile. The experimental results support these results.

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A numerical model is proposed to investigate free meandering of river. Flow field, bed deformation, bank erosion and channel migration are calculated numerically with a general non-orthogonal coordinate system which can be applied to moving boundary conditions. Flow field is calculated from two dimensional momentum equations and continuity equation. Bed deformation is calculated from continuity equation of bed load transport. Bank erosion and deposition is estimated from critical slope of bank material and emergence of bed due to the bed deposition. Time dependent change of channel geometry is calculated with an iteration process of these procedures. Calculated results are favorably compared with experimental results with movable bed and bank, and thus the accuracy of new model is verified.

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Channel processes with bank erosion in unsteady open channel flows are investigated in this paper by numerical analysis. As bank erosion and deposition occur with the lapse of time, the area of the numerical object changes with moving the boundaries. Therefore a moving boundary fitted coordinate system is used to analyze the channel process. The model is applied to experiments for the channel processes with bank erosion of straight and meandering channels. The model is verified for the widening process of straight channel, and modified for the meandering channel process by introducing equations of secondary flow component.

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The aerial photographs of the flood flow of the Tone river on Sept. 18, 1972 were analyzed to obtain velocity vectors. The main river course in the analyzed area is meandering with the wavelength 7-8km and wide flood plain exists on either side of the channel.
Sediment deposition on the flood plain and bank erosion were discussed in connection with the hydraulic characteristics of the flood flow like the absolute velocity, the streamline patterns, the vorticity and the two-dimensional divergence which were calculated by using the obtained velocity vectors.

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