The behavior throughout all over a plane forced plume is predicted by a differential and integral hybrid model. The differential boundary layer equations are used to develop an integral formulation which can describe the streamwise variations of mass, momentum and buoyancy fluxes. The eddy viscosity coefficient connects with the entrainment coefficient in this theoretical derivation. It enables to derive a relationship between the entrainment velocity and the Richardson number theoretically. It shows that the entrainment coefficient increases from 0.065 for a jet to 0.156 for a plume with an increase of the Richardson number. It is found that this model reasonably predicts the distributions of mean velocity, mean buoyancy and Reynolds stress and their streamwise variations.

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In natural rivers, there often happen the flows which bed roughness changes abruptly by some reasons. Around the section of abrupt change, river bed or bed protection structures may be scoured or eroded by the action of high shear stress, which is caused by development of the internal boundary layer. There are generally two types of flow, that is, smooth to rough bed flow, and rough to smooth bed flow. It is found that these two types of flow are not of same property, by the results of experiments. Based on some assumptions wich are derived from the experimental results, bed shear stress and internal boundary layer thickness can be calculated by applying the momentum equation to the control volume of internal boundary layer. This method can simulate the flow conditions in the wind tunnel and open channel.

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In order to make a physical model of bed material load transport process including both bed load and suspended sediment, it is important to investigate the mechanism of transition from bed load motion to suspension. In this paper, based on clearer definitions of bed load motion and suspension, a physical model of transition from saltation as deterministic motion into suspension as random motion is proposed and it is inspected by film analysis of behaviors of polystyren particles in open channel flows. Furthermore, based on the present model for transition from saltation to suspension, the so-called reference concentration of suspended load, total load transport rate, and the ratio of suspended load to total load are deduced to demonstrate the utility of the present model.

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Numerous rock caverns are in use for the purpose of underground electric power stations, the fuel stock piling and the repository of radioactive nuclides. This paper studies the groundwater motion in fractured rock masses by taking the deformation of fractures and rock into consideration, and the groundwater movement around cavern is analyzed by applying the rock block model. The theoretical results are compared with those of field measurements.

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Model experiments are performed to examine the vertical mixing process in the case when the wind stress and thermal convection simultaneously act on the surface of thermally stratified water body. The stress-driven mechanical turbulence and thermally induced convective motions are simulated by means of the oscillating grid and the bottom plate heater, respectively. Introducing the characteristic velocity scale defined by linearly superimposing the energy flux of mechanical turbulence and thermal convection, the mixing rate can be expressed as a function of an overall Richardson number. Analytical solutions for the mixing layer depth, specific density anomaly, etc., are derived based on the experimental law of mixing rate. Satisfactory agreement between the theory and experiments is obtained. Additionally, the régimes where the mechanical or thermal stirring effects dominate the mixing process, respectively, are systematically classified.

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Stability problems, including oscillation or even divergence of the solution, have been always involved in case of the unsteady flow computation as far as explicit method is employed.
The Optimum Grid Method (OGM) proposed in this paper eliminates stability problems with minimum computation time, keeping the solution points in domains of determination, since the computer can choose optimum time intervals automatically. OGM makes it also possible to evaluate computational error scales.
OGM is an extended form of the characteristics method with a fixed time interval being intensively utilized and developed by Iwasa and his group. It should be noted that OGM is solely designed for PAX type parallel processors, though this may be employed by any existing computers.

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A theoretical study on the axisymmetric flow into a point sink in a stratified fluid was conducted by Hino and Onishi, and its theoretical results were verified experimentally by Hino et al. But these experimental results did not explain any effects of the finite opening on selective withdrawal. Therefore, the data obtained by these experiments are insufficient to adapt in designing the actual intake structures.
The present study was conducted theoretically and experimentally to determine the effects of the dimensions of intake opening on the thickness of the withdrawal layer. Among discussed profiles of density distribution in the reservoir, both non-linear and linear types are included. And velocity distributions in stratified flow toward selective withdrawal finite opening are measured by LDV and useful estimation formula of withdrawal water quality is presented.

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The present study has carried out highly accurate measurements of secondary currents in fully-developed straight open channel flows by making use of a powerful two-color Laser Doppler Anemometer system with a direct digital signal processing. The primary and secondary velocity distributions, the maximum-velocity-dip phenomena, the bed and side-wall shear stress distributions and also the turbulence characteristics were made clear in channels of the aspect ratio of 2. The effects of free surface on three-dimensional structure were then examined by comparison with the data of closed duct flow. Most noticeable feature is that a strong free-surface vortex is produced due to high an-isotropy of turbulence which is caused by the existence of free surface. This vortex produces a velocity dip and also restrains the development of the bottom vortex.

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Mathematical models for defining three-dimensional turbulent flow and bed topography in meandering sand-silt rivers are presented, and interaction between them is analyzed. It is revealed theoretically that the secondary flow shows reduction in its magnitude from that of uniformly-curved open channels and shows phase-lag against the channel plan-form. A model for defining bed topography is derived by considering sediment balance for both bed load and suspended load, the transport rates and directions of which are obtained from the flow field thus determined. Laboratory tests have supported the present models. The study presented herein has made it possible to predict the large-scale bed topography of meandering sand-silt rivers such as the magnitude and the location of local scour and point-bar deposit.

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Although a suspended-load phenomenon has been treated as turbulent diffusion, the phenomenon should be mainly considered as convective dispersion by the external forces due to gravity and random turbulent fluctuation. Based on this concept, the new theory on suspended-load is developed, that is, the coefficient of diffusion and the distribution of concentration are analyzed by the aid of the newly constructed simulation model, which is based on the dynamic equation of particle motion and verified by the experimental data. The characteristics of its motion are studied by the newly developed theory and some of the problems which are not clearly explained by the existing theories can be solved.

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An integral (bulk) layer model is devised for the prediction of thermal fields in reservoirs. The vertical mixing process is described by using the integral equation approach of a bulk mixed layer model. The horizontal advective process is evaluated by our developed theory for withdrawal flow fields. Intending to obtain useful information on internal behaviors, a year-long field survey was carried out at a reservoir. It is demonstrated by the comparison between predicted data and observed data that the present analysis is capable of reproducing field measurements of water temperature with remarkable accuracy, regardless of its simple modeling. Applying the analysis, the non-dimensional hydraulic parameters which govern the thermal fields are derived which enables the classification of the types of stratification in reservoirs.

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The dispersive transport of a conservative solute in the two dimensional stratified confined aquifer is analyzed by applying Aris moment method. In this analysis, the permeability distribution is a known function of vertical position of the layer and the flow is unidirectional, parallel to the stratification. The result of the analysis is that non-Fickian behavior occurs early in the dispersion process, macroscopic-dispersion coefficients have been demonstrated to depend in a complex manner on heterogeneities of the permeability. This process can not be represented by conventional advection-dispersion equation. For large time, transport process becomes Fickian type, macroscopic-dispersion coefficients approach continuously to a asymptotic value. Microscopic-dispersion coefficients measured in the laboratory tracer tests may be inadequate for predicting dispersive transport in the stratified aquifer.

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A stochastic single storm pattern with a peak of rainfall is theoretically derived from the bivariate exponential probability density function defined by Freund. Two typical design storm patterns: backward peaked type and central peaked type are prescribed by three parameters: the reduced variate y_P of the peak rainfall intensity, the autocorrelation index k, and the conditional probability F. A new conditional probability intensity-duration formula is proposed by integrating the given design storm hyetograph. Furthermore, a practical estimation method of the three parameters prescribing the design storm and the intensity-duration curve is clearly shown and demonstrated using actual rainfall data.

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It may be quite reasonable to consider that the generation in severe hydrologic events of basic elements in water-works design is an uncertain quantity swayed by many physical and probable elements in nature. Therefore, under present conditions, water-works design must be framed on various assumptions. In this paper, the authors assume that the probability of generation in severe hydrologic events has Poisson distribution, and study on making use of Bayes' theorem in regard to the recurrence intervals of large severe hydrologic events like the heavy rain etc., further, try evaluations of the security or the risk on water-works design.

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The authors have presented the equi-risk line theory for storage facilities with the constant release rule. It is extended to be applicable to those with the following general storage-release relation: q=az′^p, where q is the release discharge, and z′the volume of stored water. The release rule is characterized by the value of p. The shape parameter of the equi-risk line is expressed in terms of p.
A standard equi-risk line for urban flood control systems is proposed, which can be applicable in common within a basin to calculate the necessary and sufficient capacities of any kind of flood control facilities, regardless of their location.

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The authors have presented a probability density function of total rainfall depth of a single storm. It is expressed in terms of the second kind modified Bessel's function. Using the asymptotic expansion of the function, a simple probability density function of the annual maximum precipitation depth is derived. which is named “SQRT-exponentialtype distribution of maximum” The p. d. f. is long-tailed compared with the Gumbel's distribution, which suggests higher probability of the occurrence of record-breaking large precipitations or so-called outliers. For example, the historical maximum 24-hour precipitation at Osaka (283.7mm) is reasonably evaluated by means of the p. d. f. as once a 214-year precipitation, while Gumbel's distribution evaluates it as once a 955-year precipitation, which is apparently unrealistic.

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In order to establish the optimal flood control system with the comprehensive criteria on the whole river basin, it is necessary to examine the effects of flood control projects in the system consisting of multi-subbasins and multi-defence points on the flood inundation probability in time and space. In this paper, firstly, the flood probabilities in time and space among the subbasins are assumed through the stochastic structures of hourly rainfall and the runoff system model. Secondly, their probabilities are transformed into the flood inundation probabilities at multi-defence points in the river basin based on the flood routing model including the effect of dam control and overflow at the point being lack of river capacity, and the shift operation on non-homogeneous finite state Markov chain. Those estimated flood inundation probabilities will be introduced into the decision model of flood control system.

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This paper presents a numerical model of nearshore currents taking into account the wave nonlinearity, in which a cnoidal wave theory is used for the estimation of wave characteristics. The model is applied to the computation of wave transformation and nearshore currents across the surf zone on a uniformly sloping beach and on model topographies, and the results are compared with those obtained by a linear model. The comparison shows that the wave nonlinearity has a strong influence on the offshore distributions of wave height, wave direction and mean water level, and the peak position of longshore currents, but that it does not have much effect on the longshore current profile itself. It is also found that the wave nonlinearity acts to suppress the formation and growth of nearshore circulation currents.

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A numerical wave prediction model based on the radiative transfer equation is applied to the estimation of the sheltering effects of Sado Island on ocean waves off the Hokuriku Coast. The model is operated in two steps. First, ocean waves in the Japan Sea are computed on a coarse mesh during a period of severe seasonal wind. The wind distribution is given from a weather map analysis based on the spline function approximation to isobars. Next, ocean waves off the Hokuriku Coast are hindcasted on a fine mesh by giving the computed results on a coarse mesh as the inflow boundary condition on the open boundary. The computations show a satisfactory agreement with the observations along the Japanese coast. The sheltering effect of Sado Island is estimated from a comparison with the computation neglecting the island.

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A new numerical algorithm for the Lagrangian treatment of incompressible fluid flows with free surface has been developed. The novel feature of this new algorithm is the use of the Lagrangian finite element method together with the velocity correction technique. Lagrangian specification permit the favorable treatment of free surfaces, whilst the velocity correction approach greatly simplifies computation in terms of algorithmic structure. Numerical example illustrates the properties of this technique.

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Wave reflection and transmission by an infinite array of cylinders of arbitrary crosssection and water particle velocities through the slits of the array are analyzed as a boundary-value problem. The method of matched asymptotic expansions is employed. For the case of flat plates, calculation were done for two different types of the inner solution, and the difference of the final solutions is discussed. The comparison of the results with experimental data shows that the present linear theory, which does not account for the quadratic energy loss effect at slits, predicts well the reflection and the water particle velocities, while it overestimates the transmission due to not taking the energy loss effect into account. In the case of flat plates and the case of circular cylinders, the results coincide with existing theoretical results.

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Six equations of higher order approximation derived for U_r>>1 and U_r-1 are examined numerically in comparison with the MAC method, with an emphasis on the development of soliton fission. The reason why the exsisting theories such as the KdV, Boussinesq and Peregrine equations give a more rapid growth than hydraulic experiment is explained. The best fit is obtained with an equation for U_r>>1.

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Wave hindcast during typhoon 7916 in the Osaka Bay connected with the Kii channel is carried out to investigate the applicability of our shallow water prediction model. To estimate the effect of swells propagating into the area from the Pacific Ocean, deep water waves in the open sea are sequentially computed on a coarse mesh including a part of the Pacific Ocean and on a medium mesh off Shikoku Island, in cases where wind fields are generated by a typhoon model. Next, shallow water waves in the concerned area are hindcasted on a fine mesh, in case where wind fields are estimated through spatial interpolation of the observed winds. The results of computation on each mesh showed reasonable agreement with those of observation in wave heights, and frequency and directional ispectra.

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As a basic study to establish an analytical method about dynamic behaviours of various kind of pile structures and to clarify their characteristics of dynamic response to waves, a theoretical solution has been derived about the vibrations of a small diameter pile due to small amplitude waves. The solution presented here is more concise than the methods of numerical analysis, whereas the integral constants contained in this solution must be determined to satisfy the boundary conditions according to each situation. This paper treats the vertical pile both elongated from the bottom to the water surface and pierced the water surface. For the latter case, the validity of this solution has been verified by comparing the experimental data of the displacement.

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This paper deals with the loop analysis for efficiently solving the steady flow in large pipe network system. (1) The analysis having not flow rates through co-trees but around loops (or meshes) as independent variables is graph-theoretically formulated. (2) The calculation algorithm using the conjugate gradient method is shown to solve the nonlinear optimization problem based on the principle of minimum dissipative energy. (3) For practical and efficient calculations of sparse matrices how to number nodes, trees, and fundamental loops is made clear. And (4) the method due to the minimization is compared with other excellent methods based on the Newton-Raphson algorithm.

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As one of the utlization of sewage sludge, we should try to let it to be fertilization and soil reformation. The natural sewage sludge is not suited to effective use in many standpoints of view, especially in the case of utilization as a fertilizer. On the treated sludge by Fluoride Electrolysis, the most defect above shown has been succesflly get rid of in our recent papers. Nothing remains but stopping on excess of nitrogen in water by rapid decomposition of organic matter, yet. In this report, material (especially nitrogen and phosphate) being contained within treated sludge could be dissolved rarely in water and so become to be too slowly and usually effective fertilizer. Moreover the organic fibers (principally made of protein) made to combine soil particles each other and soil has more permeability. According, floating soil are prevented and the granulation makes it to be stabilized and organized.

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Many numerical, hydrological and chemical techniques have been developed to separate each run-off component from discharge. In this study, filter separation method is applied to separate the concentration of water quality of surface and ground-water flow.
The concentration of ground-water flow (C_g), estimated by this method, seems to be constant during a short period of one or two months. During a long term, however, the value of C_g varies seasonally. As the concentration of surface flow (C_s) is influenced by many factors, such as season, water quality, discharge and so on, the value of C_s varies a great deal. And C_s can be expressed as various functions of the value of surface flow (Q_s).
We propose here a new method to separate graphically each quality by using the relationship between the water quality (C) and the ratio of discharge (Q_s/Q) based on the chemical mass-balance equation. It enables us to separate the quality of C_g and C_s, and to estimate its fluctuation characteristics.

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A model of estimating the volume fraction of a multi-species bed of particles was derived by extending the model for a two species bed. By the proposed model, the volume fraction of a bed can be computed with each diameter, mixing ratio and volume fraction of particles.
The validity of this model was verified by comparing computed volume fractions with experimental results of 3-6 different size glass beads and 2-8 different size sand particles mixtures.

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Various pollutants which caused by human activities are accumulated in our environment, and the accumulated pollution loads have a great amount of potential for the water pollution. These pollution loads are flushed out by rainfall through a road surface and gutters etc., and directly flowed into the receiving water. For this reason, the pollution loads in receiving water are increasing. For the purpose of reducing these non-point pollution loads, we must survery the characteristics of runoff loads from these pollution sources. In this paper, we derived the model for runoff loads of storm drain which is one of non-point pollution sources. And we applied these models to six drainage areas where separate sewer system are provided. From these examinations, it becomes clear that our model represents these runoff patterns and characteristics properly and it is useful for preliminary surveying of runoff loads.

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In order to investigate the behavior of the organic halides precursor in the activated sludge process, bench scale reactors were operated at various organic loadings. Trihalomethane formation potential (THMFP) and total organic halides formation potential (TOXFP) were measured as the organic halides precursor. The effluent from the reactor fed by potato starch which has not THMFP produced THMs with the reaction of chlorine. In the experiments using primary settled municipal sewage or its 8μm filtrate, the removal of THMFP was mainly associated with the removal of particulate precursor. THMFP of the effluent was related with a hard biodegrable organics in the influent and biological metabolic by-products. The ratio of THMFP/TOC of the effluent was increased than that of the influent, since the removal efficiency of THMFP was lower than that of TOC. TOXFP removal efficiency was almost the same as TOC removal efficiency.

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Moisture content is usually used to evaluate the state of water in compost and it is a useful operational parameter. However it does not describe the state of water in terms of microbial activity, hence the upper and lower moisture limits for composting are indefinite.
In this paper, relationship between water activity (a_w), which is numerically equal to the equilibrium relative humidity expressed as a decimal fraction, and respiratory activity was experimentally examined with several materials. The results show that water activity is useful as an index of lower moisture limit and a common standard, a_w=0.94, is proposed. Air flow tests were also performed with the materials of different moisture content. The results indicate the moisture content which causes clogging of air supply in compost layer is an upper moisture limit.

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In order to clarify the mechanism of interaction between flood flow and storm surge in a river channel, the authors make the theoretical investigations on the water waves with very long period running up the river. Sinusoidal waves are given at the downstream end of the river as substitute for storm surges, and the analytical solutions are presented for the water levels and the flow velocities at various locations along the river channel. From those solutions, the approximate solution for the highest water level is derived, and can make clear its relations to the amplitude and the period of waves and the river discharge. The other basic characteristics of propagation of the waves are also revealed based on the obtained analytical solutions.

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Stability analysis of slope, based on the assumption of uniform field, cannot estimate two-dimensional scale of failure. On the other side, the depth of sub-surface flow which is highly related to slope failure is never considered uniform at natural slope. Paticularly, at a V-shaped micro configuration of the ground, the rise of sub-surface flow depth must be rapid and the failure will occur first at there. This paper proposes a model which estimates two-dimensional scale of failure occurred at such a not uniform field. The model consists of two parts, one is configuration model as shown in Fig. 1-Fig. 3 and one is stability analysis model. The stability analysis model is based on circular arc method, which introduces cohesion on the side of circular arc in addition to the bottom of the arc.

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A conformal mapping of a finite region bounded by wavy boundaries is proposed. A modification leads to a transform function of the semi-infinite region over an asymmetric rippled bed. The technique can be extensively applied to the analysis of the two-dimensional fluid motion bounded by wavy boundaries.

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