The authors advocate a current control system to enhance water quality in reservoirs via a combination of dispersed aeration and selective inflow/discharge facilities. Although from spring to autumn the temperature in the surface layer of the reservoir is usually higher than that of inflowing river water, it may drop lower during the rainy season, in cold summers or directly after major flooding. When this happens, turbulent river water heavy in nutrient salts enters the reservoir surface layer, leading to potential eutrophication and long-term turbidity.
This report describes the Water Temperature Control System, designed to enhance water quality in reservoirs by addressing these specific problems. This system regulates the vertical temperature distribution in the reservoir and the temperature of inflowing river water using heat pumps.

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Through exeriments for horizontally homogeneous shearing flow, characteristics of mutual entraiments are observed. The velocity fluctuations near the density interface became relatively large. This shows the mutual entrainment toward the upper-and the lower layer-directions were caused simultaneously near the interface by shear instability.
With visualization technique it is observed that the mutual interactions between the vortex shear layer and the gravity wave play a dominant role on the interfacial mixing.
The characteristics of mutual entrainment are also analyzed considering the interraction between the dynamical property of vertex shear layer and graviry wave.

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Adoption of the light-limitation method for preventing reservoir eutrophication requires an efficient destratification system. Here, bubble plume system was discussed. The stratification is destroyed with the evolution of the intermediate layer, which is bounded from the upper and the lower layers by fronts. Most efficient destratification is achieved with the equivalent plume number of 1300. The upper front density gap is parameterized with the bubbling rate, the depth and intensity of the initial thermocline. For the light limitation method, the bubbling rate should be large enough to make it small. For the hypolimnetic aeration, on the other hand, the bubbling is to be weak as to keep it large.

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Hypolimnitic water lifting system with a vertical shroud and continuous bubbling was analyzed to examine destratification efficiency in two-layered environments. The lifting discharge of the shroud was numerically estimated, the results of which were fitted to empirical formulae, using representative scales of velocity and total void ratio. These formulae were linked with destrartification efficiency introduced in other investigations. It was clarified that this system has more lifting efficiency compared with the air-bullet lifter and that the characteristics of mixing efficiency are quite different.

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Tokyo Bay has been selected as a study area and the bay was divided into 215 blocks in order to analyze the exchange flow between various blocks by applying a non-linear programming method and to identify the characteristics of flows in the bay in four seasons.
The analytical results obtained successfully revealed the occurrence of flow patterns which cannot be expressed by existing simulation analyses, and consequently made it possible to conduct discussion on the environmental values given to each block.
Based on the results of flow analysis, particles were thrown into all boxes in the bay and the tracking of these particles was carried out, in an attempt to evaluate the size of bay-water retention time.

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Typical river modification methods were applied to the Tagawa River, Tochigi prefecture, Japan. A range of 1.25km was straightened and widened to reduce flooding.
An investigation of the available habitat and the biota was made to grasp the biological effect of the modification. This study discusses the small river modification method to preserve the fish habitat. There are a few studies which observed a relationship between riparian habitat and change of fish for a stream modification in Japan.

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Laboratory tests were performed for flow over flexible, artificial vegetations attached to the bottom of an open channel. It is found that the turbulence generated near the boundary of the vegetation is transported upward by ejection event and downward by sweep, respectively. The organized vortex generated at the boundary of the vegetation is closely associated with the transport of the Reynolds stress. Moreover, instantaneous three-dimensional velocity fields above the vegetation are obtained by using Mass-Consistent model. A close relation between the organized vortex and honami (waving of the flexible vegetation) is observed.

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Recently, it has become important to consider environment around dams or weirs according to the change of the social background.
Under the circumstances, many fishways have been constructed on the weir or low dams. Most of fishways, however, are designed without hydraulic consideration. It is useful to research into the inside structure of the pool-type fishway, in order to increase the rate of passing fish. In this paper hydraulic problems are reported that have to be taken into consideration at the design of fishway.

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Horizontal large-scale eddies are observed at the flood flow in river with vegetation. Velocity and water level fluctuate periodically by these eddies. In this study the experiment is conducted to clear the characteristics of periodical low fluctuation modes in flow. Non-linear stability analysis using a simple 2D-numerical model is performed, providing a good explanation for experimental results of distribution of velocity and dominant wave length of horizontal eddy in flow with vegetation.

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The change and its influential factors of the thermal environment of Nagoya City and its suburbs are examined. As a results, the trends of the warming and drying caused by the urbanization in the areas concerned were confirmed quantitatively. The actual conditions of the principal influent factors which were the heat exhaust, change of land use and sea breeze from Ise Bay were grasped, and the relations between these factors and the warming and drying in the area were discussed.

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This paper is a study on an application of thermodynamics to urban thermal environment. First field observations were performed in the campus of Shibaura Institute of Technology in Omiya city, and then thermal balance analyses were carried out using the one dimensional thermal balance model. Through this procedure, we clarified the thermal characteristics of four different landuses. Second we applied the thermodynamics to analyze the energy flows for a 1m atomospheric layer on the ground and evaluated the entropy balances. Finally we have proved the applicability of the environmental thermodynamics to urban thermal environment.

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Air temperature of the surface boundary layer in urban and its suburb areas are determined using a vegetation model by TM for regional surface energy balance. The model is based on the assumption that evapotranspiration in urban areas is due primarily to vegetation and there is Monin-Obukhov similarity in urban areas. In this model. evapotranspiration is controlled by the evapotranspiration area index. i.e., effective leaf area index, vapor pressure deficit at leaf temperature and stomatal opening. Moderation effect due to vegetation on air temperature in urban areas can be determined from the relation between NDVI and air temperature indicated by the vegetation model. The moderation effect is 1°C for an increase of 0.1 in NDVI.

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Growing cities have been deteriorating heat environment due to artificial coverage of the ground and artificial heat effluence. The authors focused on the watering on paved roads as one of elective and immediate measures against the situation and observed the elect on the micro climate in a city area in the last summer. The results showed that the difference in temperature and humidity at two points with and without watering were maximum 1.5 degree and 8%, respectively. In addition, the estimated heat balance at the points showed that the considerable latent heat and the lateral heat transport contributed to lower the surface temperature of the road due to watering.

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Sea breeze and geostroplic wind which blow from the south not only cool the air in the center of Tokyo but remove a large amount of heat flux produced there to the leeward. In order to evaluate this influences, temperature field of the Tokyo metropolotan area was analyzed by using a turblent closure model.
As a result, the relation between the strengh of geostrophic wind and a rise in temperature of suburban area was revealed.

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The cooling effect of river on atmospheric temperature around river in summer is a well known phenomenon. To elucidate this phenomenon qualitatively, some experiments were carried out in wind tunnel having 90×90 cm cross section. A river channel is simulated by a long squarepipe (12.5×8 cm cross section), and dry ice was set inside of this pipe as cooling source. Both side of this pipe, heat insulating materialcovered with artificial lawn as surface roughness were installed as riverside area. Wind velocity was measured with 2-dimensional hot-film anemometer. Changes of values of Reynolds stress and eddy viscosity, and of theirprofiles were analyzed in combination with experimental conditions of cooling and wind velocity.

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Field observations were conducted at Ara-river in 1993 summer to evaluate the effect of heat balance on water temperature. The observation in the river course consists of measurements on long-and short-wave radiations, heat and vapor fluxes on water surface and measurements on vertical distribution of water temperature, saline concentration and transmissivity of solar radiation through the water body. The development of thermocline in the water body associated with net radiation was observed.

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Meteorological field observations were performed in the Ara River to study the effect of vegetation (trees and grasses) on urban meteorological environment in summer. In those observations, velocity, temperature and humidity profiles were measured by using lifting balloons. Momentum, heat and vapor fluxes were derived from the observed data. The results reveal the process of heat exchange between the atmosphere and the vegetation. It is found that the atmosphere is cooled by transpiration of both trees and grasses.

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Stadies were carried out to investigate the influence of the pavement material and aspect ratio on the wall and ground surface temperature inside a North-South oriented street canyon through the computation of radiation flux.It was found that walls and pavement in a street canyon with small aspect ratio received more solar and infrared radiation due to large sky view-factor and higher temperature of the surrounding surfaces compared with a case of large aspect ratio.Thus, surface temperature of the wall and pavement were also higher. And the surface temperature of the asphalt pavement was higher than that of the concrete one, and infrared radiation emitted from the pavement surface caused the wall temperature in the former higher than in the latter.

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In the outdoor thermal environment, thermal sensations of human are affected by many meteorological conditions. In this study, an attempt is made to provide a tool for systematically analyzing variations of outdoor human energy budget and thermal load as one kind of objective comfort indexes. One example of analysis is presented here and following results are obtained;(1) The long wave radiation from the ground surface makes much effect to the radiative flux to a human body, and (2) A simple method of estimating the thermal load on a human body using the glove temperature is shown to be useful as for the 15 min averaged value.

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The unsteady flow behaviour in the open channel with rectangular dead zone is investigated by both the numerical analysis and the laboratory tests. It is pointed out that the temporal velocity and depth variations at the interface between the main flow and the rectangular dead zone can be decomposed into the three components of (1) the shear layer instability, (2) the seiche and (3) the long period oscillation with twice the period of the seiche. The last component is caused by the alternate pattern of vortex impinging to the downstream corner. It is shown that the unsteady characteristics of the flow are well reproduced numerically by means of 2D-plane open channel flow equations

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In compound open channels, a shear instabilitiy generates periodic 2-D eddies at the junction between the main channel and the flood plains, so that a pair of vortex streets are formed at the both junctions. Velocity distribution in the channel is determined by the interaction between those two vortex streets. The period of the vortex is derived from a linear stability analysis. The experimental data support the results of the analysis. It is found from the experiments that the interaction between the vortex streets is emphasized when they are arranged in the stable order of the Karman vortex.

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Steps towards the prediction of the hydrodynamic forces in the compound open channel with vegetated flood plain are described. An algebraic stress turbulence model is offered with options for open surface proximity and for the presence of vegetation. The efficiencies of the production of turbulence energy and dissipation by the vegetation are discussed. Results for the secondary currents and streamwise velocity are shown for dilute vegetation and for dense vegetation at the flood plain.

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Hydraulic characteristics of unsteady flows were investigated experimentally when flood waves were passing through compound open channels. Some noticeable features of unsteady flow structure in compound channels were revealed which were significantly different from those in single rectangular channels. The unsteadiness of velocity becomes very large in main channels and the peak of velocity appears very earlier than in rectangular channels. Lateral shear stress increases in a rising stage at an interface region of main channel and flood plain. The bed shear stress exceeds the value of steady peak flow in the rising stage.

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The interesting phenomena of surface waves in the rapids of the river will be easily observed at the waterside. Particularly, it has been pointed out that only the periodic component of the waves generated at the rapids will propagate to the waterside of the down-stream pool. In order to elucidate their generating mechanisms, the simplified equations of motion, which involve the terms of the dispersion, Manning's resistance law and the eddy viscosity, are analysed by using perturbation methods and numeical calculations.
The linear and the nonlirear stability the orys how that down-going waves become convectively unstable and their equilibrium amplitude does not exist at the low values of the roughness parameter. The critical Froude number Frcr and the conesponding frequency and wavenumber of unstable waves are also determined as a function of the roughness parameter. In addition, it is revealed that the scaling of the KdV-type, which is the long-wave approximation, yields also the KdV equation, but its dispersion term comes fromt he eddy viscosity and its solution expresses the kinematic wave.
Furthermore, the waves induced by the bottom topography, whose slope is given by a sinusoidal or a step function, will be investigated numerically by spectral methods.

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Free surface profile analysis of the steady open channel flows is investigated by means of the one-dimensional basic equations with the effect of the vertical acceleration. The undular jump is one of the fundamental flows which should be considered the effect of the vertical acceleration. It is firstly shown that the wave characteristics of undular jump such as the height of first crest, first trough, etc. can be reproduced by the basic equations and the numerical method developedin the paper. The breaking process of undular jump can also be simulated by multiplying the vertical acceleration term by the dumping function. The numerical method is then applied to the free surface profile analysis of the flow with both the undular jump and the draw-down part in the mild open channel. The free surface profile is calculated as the two-point boundary value problem and compared to the laboratory test.

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In order to study the effect of vibration of trees on the flow in river, the characteristics of flow-induced vibration of a circular cylinder and a twig of pine tree elastically mounted in open channel were investigated experimentally. The amplificationof drag force and lift force acting on a cylinder in flow-inducecd vibration and that of a twig of pine tree were evaluated quantitatively. The locking-in phenomenon was also recognized in the flow induced vibration of pine tree.

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The purpose of this paper is to investigate the effect of a semi-circuler tripping wire on the aerodynamic character of a circuler cylinder. An experimental investigation on the fluid forces acting on a circuler cylinder with a semi-circuler tripping wire were carried out. It was found that there were the range of the bi-stable flows in which the short time-mean values of fluid force change intermittently, the mean values of drag and lift coefficient with setting angle of tripping wire from front stagnation point changed remarkably and the strongest correlation was observed between fluctuation of drag and lift.

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The present paper deals with an experimental method to evaluate the wall shear stress due to an oscillatory pipe flow.The method consists of measuring a pressure difference between two points along the pipe wall and evaluating the acceleration of fluid as precisely as possible. The acceleration of fluid through a pipe is reflected on the record of water level gauge mounted on a basin connected to the pipe. Once the pressure difference and acceleration of fluid are estimated, the wall shear stress is easily derived. A good agreement is found between the results from experiment and laminar theory.

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A comparable study of three versions of low Reynolds number κ-ε model is carried out with special reference to transitional regime in a wave boundary layer on smooth bottom. It is inferred that despite the useful modification suggested by later researchers, the original model by Jones and Launder (1972) has the most precise predition of wave boundary layer structure, especially in transition. Finally, the features of transition in oscillatory boundary layer are elaborated.

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The variation of drag coefficient C_D in multi-phase flow was investigated by using a series of measurements in a perpendicular rectangle duct. Several kinds of granular material of different diameter/specific gravity were used in the experiments.The following were found: as concentration C increases, C_D increases slowly below C/C_o of approximately 0.90, and rapidly above the value. Based on the experimental results, an equation to evaluate CD in multi-phase flow wasproposed. It is inversely proportional to the n-th power of porosity η, void ratio of granular material, and n is the function of velocity particle Reynolds' number R_d (=u_rd/υ).

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For the utilization of ocean energy, we are demonstrating how to gain the difference of water head by wave overtopping and how to discharge the sea water by using the head difference. The devised artificial structure is composed of two parts. One is the dam to activate the wave overtopping and to gain effectively the head difference. The other is the walls to converge the widely distributed wave-energy. The evaluation has been given for the volume of wave overtopping gained effectively by using the structure

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Two big typhoons hit the western part of Japan subsequently on September 1991. They gave extensive severe damages along the coastal region. An investigation about the damages showed that a large quantity of spray of sea water was distributed over a wide area and caused these disasters. Though a few experimental studies on salt damage have been made, many fundamental problems have been left unsolved. In the case when two-dimensional steep waves propagate on a sloping bed, the volume of spray carried by the strong wind is measured, and theoretical development is given for its vertical profiles. The concentration of spray decreases rapidly in the vertical direction and the variation in the leeward direction is very small. The dimensionless vertical profiles of the concentration depend strongly on the wave steepness rather than the wind velocity.

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Complex free-surface flows in the vicinity of an obstacle placed on the floor of a channel to generate a surface wave has been studied experimentally and numerically. The numerical method examined is the simplified MAC method of Hirt & Nichol with the volume of fraction (VOF) method of treating the free surface. This calculation method used with a third-order upwind differencing scheme gives results that agree very well with experiments for not too large waves with relatively small velocities. The experiments show that as the flow volume and the velocity increase, the disturbances appear on the free surface with significant air entrainment. The present calculation method, although does not reproduce the detailes of the experiment exactly, shows appearance similar disturbances.

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Time series of the porewater pressure in seabed under the action of the changing water pressure was experimentally investigated. Firstly, the response of porewater pressure to an abrupt change of the water pressure at the bed surface was measured. Secondly, a simple impulse-response model was proposed to estimate the time scale of the relaxation of porewater pressure on the basis of the experimental results. Finally, the transient process of porewater pressure under a sinusoidal change of the water pressure at the bed surface was reproduced by the proposed impulse-response model.

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Velocity distributions in internal wave solitons have been measured by means of image processing. Density distributions have also been measured with an electric conductivity meter to investigate mixing of the density in the solitons. The steady distribution patterns of velocity and density in a frame at rest with respect to the solitons vary markedly depending on the interfacial-layer-thickness to the soliton-amplitude ratio.

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It has been pointed out that, for surcharged flow simulations in urban drainage sewer 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 theoretical expression of the celerity, which evaluates a hydraulic function of manhles, is presented. In the later half, numerical simulations with representative urban sewer and simple underground channel systems are made using SWMM-EXTRAN, and the influence of a manhole storage on runoff characteristics of the surcharged flow are investigated.

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In some cases of shell type roller gates with a long span, oscillations of gates are seen during small gate opening because of their flexibilty. In order to make clear this phenomenon, for an actual shell type roller gate on a river weir, frequency and accelerations of vertical and horizontal direction were measured at some points, i. e. center, 1/4 and edge of span with small opening. Range of gate opening which causes oscillations, frequency and mode of oscillation, time series of frequency acceleration and etc. were analyzed.

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To clarify the basic characteristics of nappe oscillation, the effect of confined air behind the nappe was investigated experimentally. As a result, it is clarified that the shift of oscillation mode is caused by nappeconfined air interaction near the natural frequency of confined air. That is, the confined air behind the nappe plays an important role to maintain and amplify the nappe oscillation. If the natural frequency of nappe approaches to the natural frequency of confined air from the lower level, the mode of the nappe oscillation shifts to the higher mode and the nappe begins to oscillate like a resonance box with the natural frequency of confined air.

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A numerical simulation model has been developed for computing the behavior of drift wood and its dam up process due to jamming between and/or in front of the houses when drift wood debouches into horizontally two-dimensional flow field. The calculation is accomplished by an interacting combination of Eulerian fluid and Lagragian drift wood equations, in which a turbulent diffusivity and rotational angular velocity of the drift wood are stochastically given. The positions, rotational angles in a group of drift wood, and time change of the number of dammed up drift wood in the experiments are well explained by the calculation.

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This paper is concerned with the water hammer in coarse solidliquid two-phase flows in pipes. Theoretical consideration was made on in-situ concentrations, and the equations to analyze the water hammer phenomena in coarse solid-liquid two-phase flows in pipes were propoased. The calculated results for maximum surge pressure were compared with the experimental results. The agreement was observed to be good. Therefore, it was confirmed that this model proposed here is applicable to the high concentrated twophase flows.

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The pressure of mud-debris flow acting on an obstacle was evaluated for cases in which the mud-debris flow was regarded as a non-compressible, then as a compressible fluid. In a non-compressible fluid, an equation of the fluid motion describes an equilibrium between pressure and potential rate. For a compressible fluid, the force is calculated by the density, impact velocity, and propagation velocity of pressure in the fluid. Analytical results showed that in a very few times, the force acting on a structure was some times the expected momentum value (per second)

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Some critical discussions are made on the structures of governing equations which are applied to one fluid model, two fluid model and fluid-solid particle model. Special concerns are paid on the interaction force in the conservation equations for moment and energy. It is shown that there are two conflicting concepts in evaluating the interaction force between liquid and solid phases; one is that the force should not be introduced positively in governing equations, as a form like body force, but as in stress tensors, and the other emphasizes the force is reasonable in present formulas.

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In order to study turbulence modulation in solid-liquid two-phase flows, in particular effects of slip velocity between the two phases on turbulence structure of the fluid phase, interaction between turbulence generated by settling particles and the oscillating grid turbulence is calculated using the turbulence model based on the one-point closures. The calculated values either for the turbulence due to settling particles or for the oscillating grid turbulence agree well with the experimental data in the previous studies. And the model predicts that mixing of particles decays turbulence of the fluid phase.

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A new framework to develope an LES model for solid-liquid phase flow with high concentration is presented by introducing a mixed Eulerian and Lagrangian formulation of solid-particle movement. The present model has been applied to a typical twophase flow, a particle plume where solid particles settle down with a constant volume flux in the still water, giving good agreements with the experimental data.

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Suspension of the particle in the turbulent flow is simulated based on the equation of motion. The time series of the turbulence is simulated by superposing the oscillations with various frequencies in taking account of energy spectrum of the turbulence. The settling velocities under regular and irregular oscillations are estimated. The response of the particle to the turbulence is considered through the characteristics of the vertical displacement of particle. Furthermore the time scale of the motion of particles is estimated based on the dynamic response expressed by the energy spectrum of the particle's displacement.

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How to simulate the turbulent flow field is the key of the stochastic simulation of suspended sediment transport. In this study, a new method for simulating the turbulent flow field is proposed, in which the energy spectrum of turbulence is taken into account. The trajectory of suspended particles are computed based on the equation of motion in the simulated turbulent flow field, and compared with that of the Monte Carlo method. It clarifies the physical background of Monte Carlo method, in which the hysteresis of the turbulence cannot be expressed.

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Bed material load has been classified into a bed load and a suspended load based on their pattern of motion. And then the theoretical and expreimental investigations were carried out on each motion separately. But the moving characteristics of each motion should be connected smoothly, because both types of sediment are supplied into the flow from the bed due to the action of water flow. Considering such a concept, the first unified simulation model for bed material load was constructed in this study by extending the saltation model proposed previously. This model enables us to investigate the mechanism of transition between a bed load and a suspended load, and to analyze a series of particle trajectory in the condition where both type of motion coexist.

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Recent studies of the turbulent structure of unsteady open-channel flow enable us to investigate the suspended sediment transport at unsteady flow. This study shows the temporal changes of the turbulent structure and the concentration distribution of the sediment-laden unsteady flow by flume experiments. Furthermore, the effect of theb ase flow, the unsteadiness and sand diameter on the phase lag between the peak of the flow depth and that of the suspension is studied by solving the linealized depth-averaged diffusion equation.

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In this paper, deposition and transport processes of suspended load on a channel bed with a large porosity are discussed. These processes might be observed in mountain rivers, particularly in deposition areas of debris flow. In such a field, suspended load would fall into the bed layer and its transport rate would decrease in the streamwise direction. With an attention focussed on the difference of the deposition processes due to the geometrical size of the porosity, the deposition and transport processes are investi-gated experimentaly and its numerical model is presented.

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To investigate the sediment suspension from the bed, it is most important to evaluate the forces acting on sand particle exactly. In most cases a flat bed which is consisted of uniform sand particle was chosen as the research topic. In situ, bed is not flat locally and the sand particle has any exposure to flow. In the present paper, it is taken the exposure of sand particle into consideration to estimate the concentration in bed-layer.
With increasing the angle of escape, the threshold of sand particle approaches 0.07m/s asymptotically. It is one third-one half of the value which is calculated by Komar·Miller's formula in the case that the exposure of adjacent sand particle becomes the same. The maximum concentration in bed-layer is 20-35 times of it that the exposure of adjacent sand particle is the same.

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