An analytical soultion of diffusion equation is obtained under arbitrary initial condition on non-steady uniform flow field. It is caluculated that concentration in a cubic cell diffuses into surrounding N cells by the rates of influence coefficients. These coefficients are determined by the analytical solution and to satisfy the mass conservation law in surrounding N cells. The presented method is explicit and absolutely stable, and is able to make highly accurate calculations for the diffusion number greater than 0.5 and the Courant number even larger than 1.

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A numerical analysis is conducted for describing the bed-load layer as a solid/liquid two phase flow. The irregular successive saltation model for the solid phase is coupled with the k-ε model of turbulence for the liquid phase by considering the interphase momentum transport with the aid of the PSI-cell model. The present simulation estimate the velocity, the existing probability density and other characteristics of the bed-load motion: the height and length of saltation and so on. They are compared with the simulation under the clear-water assumption. Results of the present simulation show better agreements with the experiment than that of the simulation under the clear-water assumption.

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In this paper, the experiments of varied flow in a rectangular open channel were carried out using the mixtures of water and bentonite which were regarded as the Bingham fluid and the manner in which the flow over a dam and the hydraulic jump were varied by concentration of the mixtures. As a result, it was shown that experimental results to mixtures with volumetric concentration less than 2.6% (yield stress τ_f<0.38Pa, plastic viscosity η_pl<23mPa·s) satisfied the existing formulas regarding the hydraulic jump. And it was shown that when the concentraion was over 3.0% (τ_f>1.2Pa, η_pl>46mPa·s), the critical depth increased dramatically, and about 10% of the critical depth was the depth of plug flow at concentration 4.0% (τ_f=19Pa, η_pl=364mPa·s).

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A turbulence model is developed in order to investigate turbulence properties in the two types of free convection systems. A special formulation for low Reynolds number turbulence is devised so that heat transfer from the wall boundaries could be accurately reproduced. The present model well reproduces convective turbulence structure. The analysis could be applied to many kinds of practical issues in which free convection concerns; they are, for instance, assessment of thermal environment in heated urban areas, examination of heat and mass transport across the air-water interface, development of high performance heat exchanger, and so on.

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This paper presents the results of the study on a new synthetic model which can be used for predicting state of sedimentation in a whole mountainous river system. First, a new model of sedimentation using the pseudo channel network obtained from DEM (Digital Elevation Model) is proposed in order to take distibutions of slopes and hydrological conditions in a river basin into account. Next, the new model is applied to the small basin, Haruki River basin (21km²), then capabilities of the model for extending to more large and complex river basins are discussed. Finally, the new model is improved for applying to the whole Hayakawa River system (509km²) considering the spatial distrubution of rainfall, effects of Sabo dams and so on. The results of the simulation of river bed variation show that potential of the new model is very high.

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A numerical analysis has been performed for fully developed turbulent flow in a straight duct with an aspect ratio of 5:1 by using Reynolds stress model. The calculated results are compared with the experimental data available. As a result of this examination, it was made clear that the present method was able to predict cellular secondary currents, which were induced by anisotropy turbulence, and the experimental results of Reynolds stresses without great discrepancy. Moreover, numerical simulation has been carried out in order to make the relationship between sand ridges and secondary currents clear. The calculation results suggest that the generation of sand ridges and secondary currents toward the duct central region is caused by alternate location of rough wall and smooth wall.

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To determine the layout method of vane works for preventing bank erosion in bend river, secondary currents and bed profiles in the stream where vanes are installed in various layout are investigated. Based on experimental and analytical results, vane design method is proposed. It is shown that vanes works are useful through the field execution and layout method presented here is appropriate.

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A field survey of velocity and temperature fields is carried out in a stratified reservoir. Correlations between wind-driven internal motions and wind velocity and/or direction are examined. A stochastic analysis of temperature time series is performed to obtain information on dynamic properties of internal wave motions. An internal wave theory is combined with Fourier expansion technique in order to theoretically reproduce internal wave motions composed of complicated modal structure which are found in a density field of arbitrary vertical profiles. The theoretical reproduction of time series as well as spectrum of internal motions shows well agreement with the observed ones.

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Stochastic simulation of bed-load transport, in which the saltating particles are traced independently one another by a Lagrangian model, neglects the interparticle collision explicitly. Refined simulation of bed-load particles as granular assembles is proposed to investigate the detail structure of the bed-load layer; the motion of bed-load particles is traced simultaneously in streamwise and vertical two-dimensional plane with considering particle/particle interactions. Important role of interparticle collision is demonstrated through a series of snapshots of the instantaneous motion of moving particles; and statistical characteristics of the geometrical parameters of saltation. Good agreements between the present simulation and experiments on the existing probability density and the velocity profile of moving particles indicate the importance of the interparticle collision in bed-load layer.

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Numerical analysis is performed on the mixing process of two-layerd stratification by a hydraulic gun system with air bullets. The hollow system is analyzed by dividing into two parts; lifting of the hypolimnitic water and destratification by the flow from the gun-outlet. Lifting discharge of the hypolimnitic water is formulated only with the air volume rate and the volume ratio of a bullet, which leads to practicable estimation of lifting efficiency and good agreement with the results of a field experiment. On the destratification by the negatively buoyant jet from the gun-outlet, it is shown that the destratification efficiency is dominated by two parameters; non-dimensional air volume rate and stratification intenity with using an equivalent density gradient.

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A time-dependent wave equation is developed for waves propagating over a porous rippled layer, with rapid undulations about the mean depth satisfying the mild slope assumption, on an impermeable slowly varying depth also satisfying the mild slope assumption. The ripples are assumed to have wavelengths of the same order as those of surface gravity waves. The equation developed here contains the existing theories of Berkhoff (1972) and Kirby (1986). The rates of both reflection and transmission over porous rippled beds become smaller than those over impermeable rippled beds, due to the energy dissipation in porous layer.

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Macroscopic laws of unsteady fluid motions through a porous media yields a nonlinear complex valued differential equation, whose coefficients can be determined from the experiment of oscillatory flows using U-shaped channel, incorpolating the phase shift between the pressure gradient and the averaged velocity. Using present equation, the reflection and the amplitudee decay of waves through the breakwater with a vertical wall are calculated and compared with experiments. Then, it is shown that the energy loss of an inlet of breakwater and the phase shift at the boundary should be considered as the boundary effects of porous media.

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A generalized method has been developed for the dynamic response of airbitrarily shaped offshore 3-D structures subjected to horizontal ground excitations. Boundary integral method is applied for fluid domain and, the motion of a structure is idealized as a lumped-mass model, then they are combined at the structure surface boundary. The responce of twin towers with a elliptical cross-section are analyzed for the investigating torsional vibrations, and some important points concerning to the design of offshore structures are discussed.

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Either of two different hydraulic parameters is incooperated into K_L-predicting equations. They are energy dissipation and turbulence intensity. We examine K_L-temperature dependency and velocity-temperature dependency in a stirred vessel and compare K_L-predicting equations by checking whether they produce a temperature coefficient falling within an observed range. It turns out that K_L-predicting equations which include tubulence intensity as a hydraulic parameter give temperature coefficients close to observed values in stirred vessels and a temperature coefficient for rivers is indicated.

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Effect of the emersed plants and submerged plants on the river water quality was estimated based on the field survey. Concerning the emersed plants, it was revealed that they didn't purify the river water in ordinary water discharge period. The main cause of purification by the plants was the sedimentation in flood period. On the other hand, the submerged plants purified the river water in ordinary water discharge period. In flood period, however, they came off from the river bed and caused pollutant loads to the lower reaches. The merit of existence of aquatic plants in the river bed should not be estimated from the view point of water quality purification but from the view point of ecosystem conservation.

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In order to determine whether the local energy loss of the transition of full pipe flow to free surface flow and vice versa should be involved or not in the calculation of the urban storm water collection network, experiments on the flow in a circular pipe with transition were performed under a steady and subcritical flow condition.
Comparisons of the observed water depth and computed results, and estimated friction factor of the transition showed that neglecting this energy loss might not introduce a significant error.

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