Air bubbles in the sea water have smaller particle sizes and are less released from thw water than those in fresh water. Even if they reach the water surface, they tend to stay there as foams. This paper treats the phenomena of advection and diffusion of buoyant air bubbles in open channel flows by both Eulerian approach and Lagrangian one. Through the Eulerian method, the effects of hydraulic parameters to air bubble behaviour are examined. A Lagrangian model is also presented, whose simulation results are compared with Eulerian ones and their differences are discussed.

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Strong vortex convection can be generated by placing a V-shaped plate in a horizontal flow. Experimental investigation was conducted in linear stratified flow under variation of Reynolds numberRe, Richardson numberRi and dihedral angle of the V-plate. It was found that the maximum vortex rising height can be attained with a dihedral angle of about 90°. Large eddy simulation model with non-uniform mesh and non-staggered grid scheme was used to study the flow structure that shed from the plate. Experimental and numerical results conclude that the rising height of produced vortices may reach 6 times the plate height and weakly depends on Reynolds number in homogeneous flow. It has reduced in stratified flow to 4 times of the plate height withRi=0.12 and smaller than 3 times with Ri larger than 0.4. The simple V-shaped structure efficiently generated upwelling current that can be used as mixing for environment purpose

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Water pollution in a semi-enclosed sea area such as a bay or a fishing port due to stagnancy of water has been a serious problem on water environment. We proposed a new method to activate the tidal exchange between an inner and an outer sea area by creation and control of a tidal residual current. In this new method, the tidal residual current is produced and controlled by artificial structures, which change properties of resistance according to a direction of flow, set on the bottom. In this study, several tidal current and particle movement simulations with various arrangements of artificial bottom roughness in a semi-enclosed model bay were carried out. As a result of many kinds of numerical experiments, it becomes clear that it is possible to generate the tidal residual current and to activate the tidal exchange by only operation of bottom roughness.

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In this paper, we compared the numerical values with the observed values of the wind system at the summer season on the southern region of Nagasaki Prefecture. And we investigated the characteristics of the wimd system. On the summer season, it is noted by observation that land and sea breeze is almost prominent all over the above mentioned region.
The numerical calculation shows a liitel larger wind speed than observed, but the shape of hodograph of wind agrees with the observation except in the mid night.

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Central regions of big cities are becoming warmer and wamer due to the construction of tall buildings and paved roads and the reduction of green and water area; i. e. the formation of “HEAT ISLANDS”. In order to evaluate the effects of vegetation in the thermal environment of urban region, numerical simulations of air flow and thermal condition have been performed, applying LES turbulence model to show the mitigation effects by the evapotranspiration of plants.

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Very high resolution NDVI distributions for single tree were measured by an airplane MSS sensor at Tama Central Park in summer. From these NDVI distributions, Leaf Area Index and Leaf Area Density distributions for single tree, and characteristics of the shape for several kinds of tree were given. These results will be used as calibration data for the numerical model or existing Satellite Data.

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Field observations in a dense residential area near lake Biwa lasted over 3 days in summer. The measurements were carried out for air temperature; relative humidity; wind vector; solar and atmospheric radiation; roof temperature; and road temperature. Also, vertical air temperature and relative humidity profiles up to 60m were continuously measured at the center of city. Roof temperature reached a maximum value more than the road, and roof was the main factor to form diurnal sub-urban boundary layer, since the total roof area covered about 50 percent of the site. Lake-land breeze were clearly appeared during the observations. However, heat mitigation effect by lake breeze were not cleared. Urban Canopy blocks advection effects from the lake, and maintains high temperature due to a large quantity of sensible heat flux from the surface.

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Outdoor experiments and numerical analysis were carried out to investigate the effects of various pavement materials on the microscale thermal environment. It was found that the ceramic porous pavement, with small inside pores, can absorb a large amount of water after a rainfall or from the underlying soil. The water contained in the pavement is later evaporated and helps to keep the pavement surface temperature much lower than that of the normal porous pavement.
A numerical model of the large eddy simulation type was developed to study the impact of pavement samples on the micro scale thermal environment. The computational domain consists of a pavement surface with a building at its center. Computations were performed for two cases: the ground surface is covered by the asphalt pavement and the ground surface is covered by the ceramic pavement. Results of the computations reveal that the evaporation at the ceramic pavement surface is the most important reason for making its surface temperature lower than that of asphalt pavement. At 2 p.m., air temperature at 3.5m above the asphalt pavement is about 1.5K higher than that above the ceramic pavement. At 8 p.m., this difference is less than 1K.

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Characteristics of heat and moisture transfer between bridge road and atmosphere caused by micro meteorology over bridge is explored from not only field surveys at a bridge but also indoor experiments. Indoor experiments give a relation between dew freezing density and friction resistance of an asphalt plate. It is seen from the outdoor surveys at the bridge that the surface temperature of bridge road is apt to fall below zero and to be lower than the atmospheric temperature in the night. The temperature profiles in the pavement of bridge, obtained by the survey, agree with numerical results.

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Levee slope protection by use of vegetation is more economical and suitable for river enviroment than ordinary protection constructed by concrete blocks. It is important for practical use of protection by use of vegetation to clarify the relation between erosion resistance and vegetation management. In this study, erosion resistance of the levee slopes covered by vegetation which is carried out most popular vegetation management, two cuttings per year, was estimated on the basis of results of levee survey which was conducted at six different rivers. Futhermore estimation method of frequency of cuttings per year was proposed to maintain higher resistance to erosion.

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A full vegetation survey was carried out on two neighboring alternating bars formed in the Yoshino River, Shikoku, Japan. Detailed vegetation maps are presented in regard to four woody and eight herbaceous plant communities. Typical features and similarity of the plant distribution are pointed out. Several indixes representing prior fluvial process of the bars are evaluated and their community-specific properties are discussed. Moreover, site-specific cover rates of typical kinds of plant communities and bare beds are related to the indixes through regression analysis.

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This paper presents the measurement results of turbulent velocity fields for flows in a deep open experiment channel with dense vegetation. The flows showed the strong 3-dimensional properties that the maximum flow directional velocity appears near the 1/3 water depth from the bottom and Reynolds stress become negative over the 2/3 water depth area. For the cause of the phenomena, transport of low velocity fluid by strong boils to go upward from the bottom near vegetation boundary was suggested from the distribution of turbulent flow energy.

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The natural hydrology has decisive influence on waterways in South-East Asia. Many rivers in the region take meandering courses in their low reaches. The natural bed topography with alternative bar of the meandering rivers was considered from the navigation point of view. The Ikeda and Nishimura's mathematical model (1986) was applied to define the lateral bed topography in three case studies for Irrawaddy river, Chao Phraya river and Mekong river. It was found that the water level available for navigation in dry season could not afford to full load of the operating vessels. The payload of operating vessels over the year before and after local dredging has been predicted.

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For water purification of man-made lakes and reservoirs, we propose a method to make an one directional flow by making use of natural wave energy. A devised artificial floating structure has a dam with a slope to activate the wave overtopping and to gain effectively the head difference. How much the volume of overtopping is gained has been investigated. The volume obtained and sent to a bottom layer is estimated briefly for the water purification. It is shown that the wave energy in man-made lakes seems to be large enough to be used for the water purification.

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An optical sensor was used for the measurement of chl-a concentration in the Shichigashuku Reservoir in order to clarify the growth and decay of phytoplankton bloom which is highly unsteady and non-uniform phenomenon. The measurement shows the followings: The plankton was stratified just above the thermocline, going down with their growth by the displacement of the thermocline. The period of the bloom was only one week and it was concentrated in a rather shallow area where nutrient may be supplied from the bottom.
Total mass of Chl-a integrated in the reservoir is compared with the time variation of phosphorus (P) which was estimated from water quality analysis. The result shows that most of P is consumed at the end of the bloom and that (P/chl-a) ratio of phytoplankton was almost unity which is consistent with the value of the ratio shown in a literature.

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Outbreaks of Chattonella antiqua (Hada) Ono (Raphidophyceae) red tides usually occur as a consequence of phytoplankton spices succession which is a result of competitions. C. antiqua is a motile phytoplankton and capable of diel vertical migration and nocturnal nutrient uptake. On the other hand, diatoms are not motile and settle when the mixing is suppressed. We have developed a model to simulate the succession and competition between C. antiqua and Skeletonema costatum (diatom) with taking these different features of two species into account.
The effect of vertical mixing and nutricline depth on above two species was estimated in this paper. Simulation results showed the absence of mixing is necessary for C. antiqua to be dominant. Since our model considered the ecological features of different phytoplanktons properly, it is able to explain the succession due to physical condition effects. Our model showed the potential to simulate the plankton species succession depending on environmental changes.

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A numerical model has developed to simulate water quality and algal species composition in a lake. As artificial destratification is widely used in the lakes, a bubble plume model has incorporated with the ecological model to simulate the dynamic responses of individual species under artificial mixing. Ecological model predicts concentrations of phosphate-phosphorus, ammonia nitrogen, nitrate nitrogen, dissolved oxygen and pH, which may have significant effect on the growth of certain species. Model was validated using data of U Lake (Japan).

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As one of the ways of reducing algal blooming in T-Dam reservoir, two vertical curtains, having depths to cover the epilimnion thickness, are installed across the reservoir in order to curtail the nutrient supply from nutrient-rich inflow to the downstream epilimnion of the reservoir. The physical and biological process in the reservoire cosystemh ave been modelled, b y assumings tratifiedl ayereda nd parcels structure, t o predictt he water qualitya nd algal speciesc ompositionin the reservoir. The state variables, temperature, four types of phytoplankton as chlorophyll-α, soluble phosphorus, nitrate, ammonium, dissolved oxygen, biochemical oxygen demand, internal nitrogen, internal phosphorus, and when diatoms are modelled explicitlys ilica, are consideredin the model.

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An eutrophication model, incorporating phytoplankton, submerged macrophytes and nutrient dynamics in sediments was developed to be a functional tool for understanding the effects of macrophytes on algal blooming in shallow lakes. The model was applied to the Lake Veluwe experiment, successfully reproducing seasonal change in the lake, such as the transition of the dominant species of phytoplankton from diatom during spring, green algae in summer, and to blue green in late autumn depending on the nutrient and light condition, nutrient concentration in the water, as well as the yearly life-cycle of macrophytes.

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A long term computational results and sensitivity analysis of the eutrophication model, incorporating phytoplankton, submerged macrophytes and nutrient dynamics in sediments were performed for understanding the effects of macrophytes on algal blooming in shallow lakes. The model was successfully reproducing long term change experienced in Lake Veluwe (The Netherlands). The model also described the reduction of phosphate return flux from the sediment and phytoplankton biomass and the resulting development of macrophytes under improved light condition after restoration measurement of the lake by artificial flushing of nitrate rich water into the lake and reduction of external phosphorus loading. Numerical experiments reproduced the following phenomena successfully: the blooming after the initiation of macrophyte growth has a remarkable effect on the following macrophyte development, thus with higher nutrient load, the macrophytes are significantly depressed. Sensitivity analysis of important coefficients show that the maximum photosynthesis rate, the conversion rate from oxygen to ash free dry weight are most sensitive parameters for macrophyte and algal development.

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Three kinds of experimental methods are proposed to investigate nutrient release rate fbom the sediment and sediment oxygen demand (SOD). The first method is a continuous-flow incubation method with non-disturbed core sample of the sediment, and is suitable for conventionai use. The second is perfomed with a rectangular, closed nume, which should be used for fundamental research to investigate, i. e., hydrodynamic control of mass transfbr. The third one consists of a rectangular flume and a non-disturbed core sample, which addresses an accurate, standard method and is coupled to measurements widl microelectrodes. Advantages and disadvantages of these methods are discussed.

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Laboratory experiments are carried out in order to investigate the relationship between the mechanism of dissolved oxygen (DO) consumption by the bottom sediment and time-varying process of DO consumption in static water, and the factors which influence DO consumption are examined. The experimental results have shown that DO in water decreases at the initial stage and the rate of DO consumption becomes small with time. It is also found that DO consumption increases when the chasms or holes are formed on the surface of bottom sediment and the sediment volume expands due to generation of nitrogen, hydrogen sulfide or methane gas.

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The eluating rate of nutrients from bottom mud in a lake are influenced by dissolved oxygen. Especially the eluating rare of phosphorus under the anaerobic condition is much bigger than that under the aerobic condition. Therefore, it is very important to investigate the characteristics of concentration of dissolved oxygen in a lake, especially period and area of anaerobic condition at the bottom of the lake. Therefore, in Koyama lake, the long time continuos observations of dissolved oxygen were carried out during summer season. Form the observed data, it is found that the anaerobic condition will be able to occur after 2 or 3 days under weak wind condition.

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This study deals with effects of wind on flow dynamics and water quality in upstream area of Nagaragawa Estuary Barrage. Numerical analysis by one-dimensional multi-layered model is executed under various boundary conditions of wind stress and discharge. The simulation results indicate that the effects of the wind stress on the flow behavior and water quality change vary with the wind direction, the wind velocity and discharge conditions due to the barrage gate operation. The phenomena in the real field are also explaned by the simulation results.

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For investigating water quality change around the Isahaya Bay with the progress of a sea dyke construction, successive field observations and numerical simulations have been conducted. Observed data indicate clearly that water quality indices closely related to the tidal motion, and the biochemical oxygen demand varies as the change of the suspended solids (SS). Therefore, the numerical modelling of the SS is designed regarding to the resuspension and the deposition of particles. Calculated results show that current and wetland area in the bay reduce gradually as the on-going project, and the effect of deposition is dominant in the newly appeared pond. It suggests that the deterioration of water qualityo ccurred from the bottom layer, and the attention must be paid to maintain a good water environmenta round the Isahaya Bay.

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Thermal step structure bounded by stable/unstable interface is formed in lakes due to saline or turbid intrusion. Both thermal and solutal/turbid Rayleigh numbers were estimated for field and experimental staircases, among which, minor difference between silt and salt fingers was noticed as long as the particle size was less than ten microns. Rapid fingers forming a staircase with larger temperature jumps observed in a lake were found to be in the regime of salt fingers in deep oceans. Unstable staircase with thermal oscillation, moved downward in thermo-turbid diffusive regime with a settling rate, while it was static in thermo-solutal case. Turbidity Rayleigh number is usually smaller than salinity one, but strong thermohaline also moved down at the merginal stability.

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We have conducted a continuous measurement of temperature and water quality in a littoral zone of a brackish lake, Lake Shinji, where filter-feeding bivalves (Corbicula japonica) are densely populated. Daytime heating and nighttime cooling created density gradients that drove strong horizontal mass exchange. Simultaneous measurement of Chlorophyl a. concentration suggests that this circuration, especially during cooling period, mainly supports feeding of phytoplankton by bivalves which are habited at the lake bottom, and thus controls natural purification process through benthic-pelagic coupling.

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Continuous observation of density (water temperature and salinity), horizontal velocity and turbidity was performed in a brackish lake, Lake Shinji. Response of velocity field and mixing events in the bottom layer of the lake were observed during a severe storm passage. In the former period just after the strong wind started to blow, active entrainment was observed, while in the latter period, weaker entrainment was found accompanied with circulations separately developed in the upper and lower layers due to the wind set-up of the density interface. Turbidity maximum during the latter period suggests that a large amount of resuspension occurred due to wave motion even under stratified conditions.

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In recent years, Lake Abashiri has been confronted with serious problems due to water accidents induced by aoshio and eutrophication. By using a fish detector and ADCP, we could make clear the spatial and temporal structure of density stratified flow, theshort-term behaviors of salinocline (halocline) just after the occurrence of aoshio, and the overall characteristics of the flow in this lake. Based on the results of the observation, we carried out the numerical analysis regarding to the time-varying behaviors of the density interface and the wind-driven flow. Comparing the calculation results with field data, we could evaluate the influence of wind, the horizontal and vertical structure of the lake on the flow and the behaviors of salinocline.

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Several layers with high turbidity were observed in the seasonal thermocline of Lake Biwa. These layers were generated by the turbidity intrusion following the boundary mixing and the resuspension of sediments on the shore slope. The process should contribute to the vertical mixing, diffusion and redistribution of matters in stratified lakes. An intermediate nepheloid layer was found to be generated within one day, and moved vertically by the internal seiche. To investigate the mixing phenomena near a sloping boundary and turbidity intrusion into a stratified fluid, laboratory experiments were conducted using a stirring rotor and a two layer stratified water tank with a partial slope at one side. After a mixing region was developed, mixed fluid intruded horizontally into the thermocline. The behavior was discussed referring to the density difference of two layers.

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It was clear through our investigation that the water level in connected waters changed with condition of climate or atmospheric phenomena. In this paper, the relation between pressure distribution-wind field-water level change-internal flow were studied. The wind field and sea water level change were strongly effected by pressure distribution. And moreover, water level each lake was influenced by the change of sea water level. So, difference of water level grew among connected waters. This phenomena and wind field were combined and then currents in enclosed brackish waters occurred.

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Observations for the movement of salt water were carried out in Jyusan Lake for two years from 1995. From this observations, we show the correlation between the flow velocity of stratified fluid and the generation and the disappear of salt wedge, and the motion of salt and fresh water in the lake. Then, we discuss the dynamics of salt water motion and the diffusion process of salt.

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This paper deals the computation and observation results concerning density current in Abashiri River, which is a tidal river. Three-dimensional numerical simulation of salinity intrusion was carried out. And a new computational technique is proposed. The calculated vertical profiles of velocity and density represent good agreement qualitatively with the results observed in Abashiri River. We proposed the instability condition of salt wedge under the influence of tidal motion. We found that the condition could apply to the salt wedge observed in Abashiri River.

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The experiments are performed to study the mixing characteristics of the density current in the compound channel which is model of the Takase River estuary. The surface flow velocity and the salinity are measured in the experiment. The results of the experiments are compared with those in the single section channel The results of this study showed that the density current in the compound channel was more mixed than that in the single section channel. The results also indicated that the mixing quantity had correlation with the horizontal shear.

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To elucidate the ocean current in connection with global warming and to prevent marine disaster and pollution problems, development of the ocean circulation model in the North Pacific Ocean has been called for. Numerical analyses were conducted in the Pacific Ocean areas to examine the effectiveness of data assimilations on circulation flow systems.
The results of analysis indicate a high reproducibility as compared with the existing data on surface current. The results by tracking water particles could approximately reproduce the tracking of Algos-buoys which was carried out in the past.

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Matter dispersion due to the shear effect of currents is investigated theoretically as one of the mixing dilution processes. The shear is generated in the boundary layer as Stokes or Ekman layer which is given by motion equations. Dispersion of suspended matter with its own settling velocity is also analyzed besides that of passive matter. Both kinds of matter are strongly dispersed only in the boundary layers at the initial stage. As the time proceeds, the dispersion coefficient of passive matter gets inversely proportional to the water depth in the oscillatory current, while that of suspended one with a certain settling velocity is independent of the depth and fairly larger than that of passive one. However the dispersion coefficient of suspended matter gets slightly larger with increase of the water depth although that of passive one is not so dependent on it as suspended one.

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The dynamics of inclined thermals with suspended solid particles are investigated experimentally and theoretically. The inclined thermals with suspended solid have two stages; one is an accel-erating stage and the other is a deccerating stage. The deccelerating stage is formed when the initial concentation and/or the initial speed is relatively low. For this case, the solid particles in the thermal are deposited onto the bed and the buoayncy force decreases in the flow direction. The mixture of water and the barium sulfate particles is used for the experiments. The variations of the speed and the height of the thermals are measured using the video camera. Then, the numerical analysis is carried out. The numerical solusions can explain well the experimental results of the height and speed of inclined thermals.

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Front-end condition of oil slick propagating on the surface of calm water is studied by examining the existing experimental data on the front speed and carefully determined front depth. As a result, plots of the front Froude number and front Reynolds number showed almost straight line on the log-log paper. The result is applied to the two-layer model to predict the spread of oil slick propagation. Also the initial and boundary conditions of the computation for the case of instantaneous spill are inspected by referring to the shape of interface observed immediately after release in the experiments. Computed result of the front propagation is compared with the experiments of instantaneous spill.

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To evaluate the permeability of bedrock of Misogawa Dam, water quality of seepage water was measured at the initial filling of the reservoir. The variation of ion concentration showed that the reservoir water has not yet arrived at the collecting weirs. The travel time to the collecting weir of PW3 for river bed seepage estimated from the variation of ion concentration is more than 3 years. This travel time is longer than the travel time of 8 months obtained from the unsteady seepage analysis using particle tracking method. So, we can conclude that the foundation bedrock of Misogawa Dam was grouted sufficiently.

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The dispersion phenomena of the convective-dispersive transport of solutes through a porous medium is usually discussed by mechanical dispersion. However, experimental results of Matsubayashi et al.(1995) showed that both longitudinal dispersion and turbulent diffusion occurred simultaneously in the porous medium having large sized grain. To gain more understanding on dispersion, a new experiment was conducted using a single path of the porous media. In this study, it is observed that the dispersions change their characteristic whether the flow is laminar or turbulent. It is also found that Taylor's coefficient of longitudinal dispersion is applicable in this case.

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The retardation coefficient due to the sorption from gaseous volatile organic compounds (VOCs) to soil is important to predict the VOCs gas behavior in the unsaturated zone. The formulation and two types of experiments were done to evaluate the effect of sorption from gas to soil. The values of sorption coefficient and the retardation coefficient on the model soils are 0.03-203.78 and 1.13-114.62, respectively. Considering by the retardation coefficient, model simulation could result in good agreement with the experiment results.

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Chlorinated hydrocarbons (CHCs) are highly volatile and little soluble in water, and can exist in unsaturated zone as vaporized, dissolved and undiluted non-aqueous phases. Therefore, it is of great importance to understand transport mechanism of CHCs with gas advection and diffusion in unsaturated zone, and then numerical analysis for vertical transport of CHCs in unsaturated zoneincluding effect of rainfall was conducted. Vertical one-dimensional fluid flow equations and mass transport equations for water and gas phases, and two layer model for mass transfer between the phases were employed in the model presented. The results showed that, though gas phase transport is usually dominant during dry period in unsaturated zone, transport in water phase overcomes that in gas phase during rainwater percolating period.

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Large amounts of nitrogen fertilizers were applied into the soil in a tea plantation. The pH values of spring and well water originated from the tea plantation were below 7. Although acidic spring water flowed into a local pond, the pH value of the pond water remained above 7. The increase in pH values within the pond was associated with an increase in DO (dissolved oxygen) and δ ¹⁵N values and the partial disappearance of NO₃^-. As DO values within the pond remained high and nitrogen assimilation was associated with the production of oxygen by the photosynthesis of algae, nitrogen assimilation was concluded to give rise to increases in pH values within the pond.

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In order to investigate the effect of the drop-phase oxidation on the acid rain formation by co-washout of SO₂ (g) and H₂O₂ (g), a physico-chemical mathematical model which can consider the dissociation and oxidation process and the pollutant gas transfer rate from the air to the rain drop has been constructed. The results of the numerical simulation with the model show that the contribution of SO₄^2- due to the drop-phase oxidation of HSO₃^- by H₂O₂·H₂O greatly increases with decrese in drop size. This accords with frequent observations of very low pH drops in drizzle events.

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Borehole Heat Exchange System (BHES) is introduced to control car park temperature, i. e. improvement of thermal environment at a car park in the campus of Fukui university. BHES consists of a borehole and pavement, which has an asphalt layer covering 12 concrete panels installed heat exchange piping. The borehole is 70m length and comprises outer and inner pipe. Diameters of the outer and inner pipe are 90mm and 56mm, respectively.
Thermal flow circulates in a closed loop connecting between the pavement and borehole to sustain ground water quality.
The efficiency and performance of BHES are evaluated experimentally and theoretically from viewpoint of seasonal thermal energy storage.
It is shown that BHES can suppress the rise of the pavement temperature of the park in summer and melt the snow on the same car park in winter using only geothermal heat.

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Aquifer thermal energy storage (ATES) is recognized as the storage of local and seasonal thermal energy, such as summer heat, winter chill, and industrial waste heat. ATES closed by water proof walls (Closed ATES, CATES) prevents the spread of water quality pollution caused by thermal, biological and chemical change. Especially, the use of ATES in a shallow aquifer will provide low construction costs, reduction of heat transfer loss and easy maintenance besides seasonal extraction of stored thermal energy. ATES in a shallow aquifer, however, should be sensitive to seasonal meteorological changes, so that it involves many uncertainties for seasonal thermal energy storage.
This paper describes characteristics of CATES in a shallow aquifer which is subjected to seasonal meteorological changes, by a numerical computation model.

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Cold water release from a dam is a problem awaiting solution: specially for river fisheries, this is an urgent problem. Some facilities capable of effective use of sunshine to warm up water y be one of the solutions. From this standpoint, this paperma aims at making clear the formation process of river water temperature laying errphasis on the effect of day-light. We carried out simutations together with observations of river water tenperature and related weather conditions. As a results, we concluded that the absorption ratio of day-light within a water coluim is nearly 1.0, even if water depth is less than 30cm.

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Water temperature of a small river basin is predicted by applying a chaos analysis. Embedding observed data vectors generated from the data, a trajectory space is reconstructed and chaotic behaviors of time series are examined. Temperature time series is predicted, by applying a linear prediction scheme proposed by Sano and Sawada. The present analysis is verified by applying it to describe the logistic mapping function which is known as one of dynamic chaotic processes and whose governing equation is already known. Through comparison between the field data of river temperature and the analysis it is investigated how long prediction duration is possible and how much dimension of observed data vectors is necessary for water temperature prediction with desired accuracy. The present method is expected to be a useful measure for prediction of hydrological phenomena governed by some non-linear deterministic processes.

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Numerical calculation of flow including shock wave is one of the important tools in the practical river engineering works. Flux Difference Splitting, FDS, scheme is one of the numerical method to simulate the flow with shock wave. In this method, the theory of nonlinear characteristic wave and the concept of numerical flux are taken in account and it is very easy to be applied to various condition of open channel flow. In this paper, a numerical model using FDS scheme for two dimensional open channel flow is developed and was applied to several different hydraulic conditions. The calculated results are compared with the theoretical and experimental results and good agreement is obtained.

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A numerical prediction method has been developed for threedimensional flows having oscillating free-surfaces. On the basis of the arbitrary Lagrangian Eulerian (ALE) method, the profiles of freesurfaces are represented by three-dimensional body-fitted coordinates, which are regenerated in each computational step using cubic spline functions. Navier-Stokes equations are discretized on a Lagrangian scheme in the transformed space with sufficient numerical accuracy. The present computational technique has been applied to threedimensional non-linear sloshing in a cylindrical tank. As a result, it is concluded that the reasonable numerical results are obtained by the present method.

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