A three-dimensional potential flow model was formerly developed to predict wind fields in complex terrain. In the potential flow model, wind vectors and air flows are estimated from a velocity potential function obtained by combining two or three-dimensional doublets and a uniform stream. In this paper, the validity of the potential flow model was examined through comparison against wind tunnel experiments and field model experiments. The calculated wind direction with the potential flow model can be considered mostly appropriate excluding wake district. The calculated wind velocities closely agree with the observed ones at a distance from the ground but are overestimated near the ground. This is due to potential flow which cannot accomodate viscous effects. To introduce viscous effects, a quasi-potential flow model was developed. This model is a simple method to modify wind fields of the potential flow model with only velocity distribution of inflow boundary conditions. The results of the quasi-potential flow model agree relatively well with the observed velocities even near the ground.

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When the high concentrated turbid water enters into a reservoir and collides at the dam, an internal surge is formed. With the repetition of the surge, the turbid water spreads in an extensive space of reservoir. The understanding of behavior of the surge is necessary to manage properly the water quality in the reservoir. As a reservoir has in general a three-dimensional geometry, the behavior of surge seems to be different from that of the two-dimensional surge. In this study, the experiments of internal surge are carried out by using the three-dimensional reservoir model with gradual change in channel cross-section. It is shown that the motion of surge is considerably affected by a reservoir geometry and by the selective outflow. Theoretical investigation is also made on the height and the advance speed of surge.

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The behavior of bores in a channel of constant water depth caused by the breaking of a dam is investigated. The basic equation in this problem are derived on the basis of Whitham's assumptions in the dam-break problems on dry bed, and they are solved on the assumption that the ratio γ of water particle velocity to wave-front velocity in a bore only depends on the relative water depth h₀/h₁, across the dam initially set. The validity of the solution is examined in comparison with laboratory experiments, it is concluded that the solution is applicable for a relatively long time after the formation of a bore. It is also discussed with a moving hydraulic jump condition in the dam-break problems.

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Wave damping by submerged vertical plate is important for estimation of transmitted waves over a submerged dike. Large discrete vorticies are generated alternately, near both sides of the edge of the vertical plate. The behavior of the vorticies can be classified into three types in relation to the ratio of the plate height to the depth. The velocity inside the vorticies are measured, and it is found that the vortex is simulated with the turbulent Oseen's vortex model. Good agreement of the energy loss of the wave with the energy of the generated vorticies confirms that the wave energy is dissipated as a result of the formation of the vorticies. New formula for estimating energy loss of wave is presented as a function of the external parameters for waves and the vertical plate.

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The caverns are of use for such various purposes as the electric power station, fuel stock piling and repository of exhausting materials. The present study deals with the heat conduction around the oil cavern and the canister for reposing the radioactive nuclides. The measurement of temperature is done by thermometer as well as the photographic observation due to Thermosensitive liquid-crystal-film in a laboratory. The experimental results are compared with several numerical calculations obtained from the modified Fluid in Cell method on the basis of a set of energy and groundwater equations.

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This paper examines classification of rapidly varied flows in a two-layered density stratified system with surface layer flowing, and the other stagnant. The analogous phenomena in open channel hydraulics are transient ones from a supercritical to a subcritical flow regime. In density stratified flows, the phenomena present remarkably different flow regimes according to some form of the upstream and downstream conditions. It is shown, on the basis of theoretical and experimental knowledges about the internal hydraulic jump, that relationships between the densimetric Froude number at the outlet, depth ratio of downstream surface layer relative to outlet depth, flow rate of entrainment of lower salt water, and types of flow are defined qualitatively.

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The existing instability theories can not treat evolutional and equilibrium processes of alternate bars because of the linear theory. The purpose of this work is to clarify the stabilization mechanism of bars in equilibrium and to estimate dominant wave length and bar formation conditions based on the derived nonlinear solutions. The theoretical dominant wave length is obtained by the condition that wave steepness of equilibrium bar becomes maximum. This dominant wave length is almost identical to that by the linear theory. The formation region becomes narrower than that by the linear theory, but the former still provides a good explanation for the formation region of alternate bars.

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River water level and average velocity in flood flow are generally calculated on the basis of the one-dimensional equation for unsteady flow. When the geometric shape of the channel is three-dimensional, they are able to be calculated by using the proper roughness coefficient which includes the effects of the geometry. But the method of determining the coefficient reasonably has not yet been established. In this study, the two-dimensional numerical analysis is conducted for the flood flow through gradually varying channel. The analysis considers time variation of transverse movement of water fringe. These numerical results are discussed from the hydraulic point of view. Moreover, the characteristics of equivalent roughness coefficient are investigated based on these results.

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Coherent structures in the near-wall region of turbulent channel flow are investigated using a nobel visualization technique that utilizes fluorescent dye excited by a sheet of laser light. Some new aspects of streamwise vortices in the near-wall region, especially with respect to pattern of existance, structure, behavior and formation, are infferd from the present experiment. The results indicate that a number of pairs of counterrotating streamwise vortices generate near the viscous sublayer and develop away from the wall, which have inherent three dimensional scales and inclined angles in the viscous sublayer, the buffer layer, and the log-region respectively in the inner layer. Further studies suggest that the behaviors of these pairs and the interaction between streamwise vortices have an important role to generate secondary flows in various scales. To further understand the characteristics of the stream wise vortices, three dimensional structures of the streamwise vortices are illustrated based on Taylor's hypothesis and the formation of the streamwise vortices is discussed in detail. On the base of these results, a model of three dimensional structure of the vortex in the near-wall region, termed OSS vortex, is proposed.

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Water surface profile was investigated for a flood flow near the river mouth. where the initial densimetric Froude number, F_i0, based on the whole depth at the river mouth is more than unity. Model experiments for the dispersion of a river into the sea were performed and it was concluded that the present analyses are not directly applicable to the dispersion of rivers when F_i0 is less than 1.5. Thus a modified analysis was made for a flood flow in the neighbourhood of the river mouth. Precise measurements of the water surface profile were carried out in the river channel near the river mouth for a model flow as well as flood flows in rivers, and a rapid variation of the water surface which can not be described by the traditional analysis was observed. A new heoretical analysis was developed to predict the water surface profile near the river mouth.

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Ordinary Kalman filter (OKF) and adaptive Kalman filter (AKF) are used to analyze the long-term pattern fluctuations in a precipitation sequence. They are applied to the smoothed logarithmic-transformed monthly average precipitation sequence at Fukuoka City.
An abnormality detection index φ calculated by OKF is used to detect the abnorma precipitation period and to quantitatively estimate the magnitude of the abnormality. The structure of these abnormal periods is studied.
The system parameters of the precipitation sequence are identified by AKF. The time of occurrence of parameter change and magnitude of change are estimated. The sequence can then be divided into several periods, where each period consists of the same parameters. Characteristics of the precipitation pattern in each period divided by AKF and of the change from one period to the other are investigated.

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In this paper a model for estimation of snowmelt distribution using insolation, air temperature and precipitation is presented. This model includes net radiation, degreehour approach and condensation and convection in a rainy day. At first the model is determined at the observational base. And it is applied to the slopes and the forested area. The results of the application of the model to the base, the slopes and the forested area are in good agreement with observed data.

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Linear response model, one of groundwater simulation models, is the linear model satisfying the laws of proportionality and superposition which is based on groundwater hydraulic theory. This model has parameters such as α-matrix and β-matrix which govern the linear relation between groundwater withdrawal and confined groundwater head. An analysis of the confined aquifer at Lowland, Tokyo was made using the model. Aquifer parameters in the model were modified until the results computed fitted the observed groundwater data. The value of fixed parameters such as α-matrix and β-matrix explains the drawdown of groundwater head by the groundwater withdrawal of this area.

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A theoretical analysis using an integral equation derived for the unknown horizontal velocity component in a pervious wall is proposed for estimating the reflection and transmission coefficients of multitudinous cylinder barriers, and various factors related to wave and structural conditions having influences on the wave dissipating characteristics are investigated for a double or triple cylinder barriers.
In two-dimensional experiments, the theoretical results are in good agreement with experimental data with respect to reflection and transmission coefficients. The nondimensional parameters to determine the reflection and transmission coefficients are the relative water depth, the wave steepness of incident waves, the opening ratio of the cylinder barrier, the relative structural length, and the chamber width ratio.

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Two formulas of sand transport rate due to wave action are proposed. One is for the region of saltation and the other is for the sheet-flow motion. The former formula is derived by theoretical consideration in which stochastic characteristics of sand particles on the bed are taken account of. A good agreement between the experimental data and the theory is confirmed. In order to derive the latter one, a series of experiments was carried out in a U-shape tube. The 1.5 power relationship of transport rate and bottom shear stress is concluded empirically for the sheet-flow motion. The limit of application of both formulas is also discussed in the paper.

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A new finite element method for the analysis of surface wave problems is presented in this paper. The characteristic of this method is that the interpolation equation is selected to satisfy the Helmholtz equation in each element. This follows that the variational functional to be minimized can be formulated as in the form that all integrations are limited just on the boundary of the element. The numerical solutions obtained are compared with the analytical and observed results. From these comparative studies, it is concluded that the present method provides a useful and valuable tool for the analysis of surface wave problems.

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The amounts off pollutant loads, which flow into receiving water, are varied by runoff process. For this reason, it becomes important to grasp the conditions of the runoff process of pollutant loads.
Runoff coefficient of pollutants is the index which represents the change of pollutant loads from certain areas where pollutant loads are produced to certain points of river. And runoff coefficients of pollutants represents the system of reaction which are taken in runoff process into receiving water.
So, we make clear the characteristics of runoff coefficient on the basis of the results of case studies with many small and medium rivers. And the major controlling factors of the runoff coefficient of pollutants and their constituent elements were discussed.

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The main purpose of this experimental study is the estimation of critical shear stress of cohesive bottom sediments. The resistance properties against currents are mainly controlled by the electro-chemical bond between individual particles. Hydraulic experiment and physico-chemical test were performed. Bottom sediments were divided into two groups according to characteristics of settling form, flow curve and resuspension behavior. The main factor which controls those characteristics was found to be the nature of cations adhering to particle's surface. For bottom sediments two critical shear stresses were defined from the resuspension behaviors. They showed linear relation with respect to viscosity and yield value on log-log paper but the relations were different between two groups.

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It has been pointed out that clarification of the river bed variation characteristics is an important problem in river engineering.
In this paper, results of the research on the actual conditions of the bed variation based on detailed field survey in Kamanashi river are presented. The field survey is conducted for getting data of the bed form at two stages, just before and after a flood runoff, in the river.
Putting emphasis of consideration on the bars in the river bed, changes of bar geometry during the flood runoff are discussed. On the basis of existing theoretical and experimental study, migration distance and velocity of the bars during the runoff are tried to estimated. For quantitative evaluation of the bed variation characteristics, some effective methods to analyze various field data are also presented.

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Using field and laboratory data, the form drag component of the total friction factor of an alluvial stream is plotted varsus the dimensionless complex reflecting the geometry of sand waves. It is assumed that the flow, which approximates two-dimensional condition, is tranquil, and thus that sand waves are ripples and/or dunes. A particular attention is given to the case when ripples are superimposed on dunes. It has been found that, in general, the relationship between the form drag component and the dimensionless complex mentioned, appears to be linear when this complex is large and it becomes logarithmic when it is small. However, it has also been found, that this general trend tends to deteriorate when the relative sand wave height increases beyond a certain (critical) value.

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In this study, it was tried to evaluate a weir discharge by using of weir height and length, and water depth and velocity under the condition of flows along non-side weir channels. A proposed weir discharge equation is expressed as Q_s=C_w√2g(Δh)^1.5L, in which Q_s is side weir discharge, C_w a discharge coefficient, L weir length and Δh, specific energy of flows over side weirs. C_w is domained by L and Froud number of flows along non-side weir channels. A proposed equation can be applied to a subcritical flow in a fully long uniform channel on a mild slope. As a result, the errors between values by experimental formula and ones by experiments were within ±8%.

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Fluid forces acting on a particle which is moving or resting on the channel bed are not accurately known. Fluid forces of a sphere rolling or sliding on a smooth boundary are measured and the drag coefficient for each case can be determined experimentally. The motion of a solid sphere rolling along the smooth wavy boundary is simulated successfully by using the drag coefficients obtained.

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