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Compact Heat-EXchanger reactors (HEX) are an important part of process intensification technology. However, most of the existed research dealing with such type of equipment has been focused on the application of one-phase reactive flows. For gas-liquid reactions, few investigations have been out carried. This thesis aims at locally studying gas-liquid mass transfer around Taylor bubbles flowing in straight and meandering millimetric channels using a colorimetric method; this is a preliminary step essential before implementing two-phase reactive systems. Firstly, the occurrence of a possible enhancement of the gas-liquid mass transfer by the chemical reaction involved was investigated. Secondly, the gas-liquid mass transfer occurring in Taylor flows right after the bubble formation stage in a microreactor was studied. Thirdly, the gas-liquid hydrodynamics were characterized and the effects of bends on the mass transfer mechanism were locally investigated in a millimetric meandering channel. At last, a rigorous comparison could be made between the meandering and straight channels. It showed how and why the meandering geometry leads to intensify gas-liquid mass transfer. All these findings enabled to formulate a scaling law, expressed in terms of Sherwood, Graetz and Péclet numbers, able to describe the evolution of gas-liquid mass transfer as a function of axial position and operating conditions.; Les réacteurs-échangeurs à plaques (HEX) sont une technologie clé en intensification des procédés. Cependant, la plupart des recherches existantes portant sur ce type d'équipement ont été réalisées dans le cas d’écoulements monophasiques. Pour les réactions gaz-liquide, peu d'études ont été conduites. Cette thèse a pour objectif d’étudier localement le transfert de matière gaz-liquide autour de bulles de Taylor en écoulement dans des canaux millimétriques droits et ondulés par une méthode dite colorimétrique. Ceci constitue une étape préliminaire indispensable avant la mise en œuvre de systèmes réactifs diphasiques. Il a d’abord déterminé si une possible accélération du transfert de matière gaz-liquide pouvait avoir lieu en présence de la réaction chimique utilisée. La deuxième phase de ce travail s’est focalisée sur l'étape de formation des bulles de Taylor dans un microréacteur. Ensuite, l'hydrodynamique gaz-liquide a été caractérisée et les effets des coudes sur le mécanisme de transfert de masse ont été étudiés localement dans un canal carré millimétrique ondulé. Enfin, une comparaison rigoureuse a pu être effectuée entre les différentes géométries de canaux (ondulé et droit). Elle a permis de montrer comment et pourquoi une géométrie ondulé permet d’intensifier le transfert de masse gaz-liquide (notamment en terme d’efficacité de transfert). L’ensemble de ces résultats ont conduit à la formulation une loi d'échelle, exprimée en termes de nombres de Sherwood, de Graetz et de Péclet, capable de décrire l'évolution du transfert de matière gaz-liquide en fonction de la position axiale dans le canal et des conditions opératoires mises en œuvre.

Natural rivers are characterized by continuous variations in bed topography, especially along curved reaches. High resolution topographic data are necessary to analyze the mutual interactions between the downstream flow and the cross-stream flow, which determine the distribution of the bed-shear stress along the channel. Because of the difficulty in acquiring good and accurate data in rivers, the major part of studies have been conducted in laboratory flumes. This paper reports on a laboratory study in which the automatic digital photogrammetric survey was applied to derive the high-resolution Digital Surface Model (DSM) of the bed topography in a large amplitude meandering flume. In order to assess the advantages of the procedure, the bed profiles obtained by the DSM have been compared with those obtained using a servo-controlled vertical profiler (PV09) has been operated and discussed.

After impoundment of the Three Gorges Reservoir, Jingjiang reach, in the middle of the Yangtze River, has gradually shown a series of atypical fluvial features, adversely affecting the maintenance of waterways. Citing the Laijiapu Waterway, a meandering segment in the lower Jingjiang for example, this paper compared the fluvial features of the channel before and after the impoundment, summed up its navigation-obstructing features, and proposed guarding the point bar on the convex bank and channel bar in the widening section as a key to maintaining the stability of the navigation channels.

In this article the influence of beavers activity on the fluvial processes in lowland rivers has been discussed. Beavers were introduced to the middle Rawka in 1983 and sites of their activity were found in the Bzura river in 1996. General zoological papers emphasise the fact that beavers live in burrows. Nowadays, beavers in Central Poland live mostly in lodges dug in high river banks. Detailed research has been conducted in selected sectors of lowland rivers on the Łowicz-Błonie Plain: in the regulated channel of big river (Bzura), meandering channel of a medium-size river (Rawka) and in the regulated channel of a small river (Igla). Beavers mostly influence fluvial processes and alter valley floors because they construct dams and thus create ponds in small valleys. In small rivers and valleys beaver activity results in retention of large volumes of water and produces a local rise of water level. In the case of large rivers the environment is transformed only locally in the immediate vicinity of the bank with lodges. Beaver activity in a meandering river is limited to slowing down the water-flow and weakening of lateral erosion – often only in a single river bend. At a different location beavers’ activity accelerated the cutting of a meander neck, cutting off of the bend and the creation of an oxbow lake. At a straight river, in favourable conditions, they may initiate the process of lateral erosion. Artykuł przedstawia wpływ działalności bobrów na przebieg procesów fluwialnych w rzekach nizinnych. W 1983 r. bobry sprowadzono do środkowego odcinka Rawki, a w 1996 r. ślady działalności zwierząt zaobserwowano w Bzurze. W ogólnych pracach zoologicznych podkreślany jest fakt mieszkania przez bobry w żeremiach. Natomiast zebrany materiał wskazuje, że współcześnie w Polsce Środkowej bobry mieszkają głównie w norach wykopanych w brzegu. Szczegółowe badania przeprowadzono w wybranych odcinkach rzek nizinnych w obrębie Równiny Łowicko-Błońskiej: w uregulowanym korycie dużej rzeki (Bzura), w meandrującym korycie średniej rzeki (Rawka) i uregulowanym korycie małej rzeki (Igla). Największy wpływ na procesy fluwialne miały wybudowane tamy i stawy na małej rzece. Tylko w małych rzekach i ich dolinach, działalność bobrów powoduje zatrzymanie dużej ilości wody i przyczynia się do lokalnego wzrostu jej poziomu. W dużych rzekach, środowisko jest przekształcone tylko lokalnie w sąsiedztwie brzegu z norami. Działalność bobrów w rzece meandrującej ogranicza się do zmniejszenia prędkości przepływu wody i osłabienia procesów erozji bocznej, często tylko w jednym zakolu meandrowym. W jednym przypadku działalność bobrów przyspieszyła przecięcie szyi meandrowej i utworzenie starorzecza. W dużej, uregulowanej rzece w dwóch przypadkach zaobserwowano inicjalną erozję boczną.

The two-dimensional (2D) depth-averaged river model Finite-Element Surface-Water Modeling System (FESWMS) was used to simulate the hydraulic conditions at a contracted bridge site. The site studied was the James River bridges near Mitchell, South Dakota. The parallel bridges are located in a crossing between the two bends of a meander. The floodplain alignment relative to the channel and skewed bridges produces complex 2D flow patterns that cannot be predicted accurately by using a one-dimensional (1D) river model. The 2D model was validated by using flow measurements collected by the USGS during three high-flow events with return periods ranging from 25 to 100 years. The validated model was used to examine the site characteristics that influence the concentrated flow on the right side of the main channel and the exchange of flow between the main channel and floodplains. The rating curves derived from the 2D model and the results of soil erosion tests were used to evaluate live-bed and clear-water...

This paper presents a practical method to predict lateral depth-averaged velocity distribution in trapezoidal meandering channels. Flow structure in meandering channels is more complex than straight channels due to three-dimentional nature of flow. Continuous variation of channel geometry along the flow path associated with secondary currents makes the depth-averaged velocity computation difficult. Design methods based on straight-wide channels incorporate large errors while estimating discharge in meandering channel. Hence, based on the present experimental results, a non-linear form of equation involving three parameters for estimating lateral depth-averaged velocity is formulated. The present experimental meandering channel is wide (aspect ratio = b/h > 5) and with high sinuosity of 2.04. The study serves for a better understanding of the flow and velocity patterns in trapezoidal meandering channel.

Drainage problem of inundated water on the lower Chao Phraya River in Thailand is introduced. Furthermore, drainage methods of inundated water on low flat land areas have been discussed by use of horizontal two dimensional bed deformation analysis. Construction of shortcut channel in the fully developed meandering channel can decrease the water surface elevation in the upstream area of the shortcut channel. Furthermore, drainage of inundated water from the irrigation channel to main channel will increase, if the connection points between the main flow and irrigation channels are located along the inner bank. Furthermore, a groin at the upstream of the connection points between the main channel and irrigation channels can decrease the water surface level at the connection points between the main and irrigation channels. As a result, drainage discharge of inundated water from the irrigation channel to the main channel increases.

The velocity distribution and bed deformation patterns in a meandering channel with consecutive bends were investigated by using both an experimental study and a 3-D flow and sediment transport model. The simulated results from the 3-D model agree well with the experimental data. The flow structure and bed deformation patterns in channel bends with different flow conditions were analyzed. Modeled results demonstrated that the velocity distribution and bed deformation in the meandering channel depend mostly on the flow regimes. For the case of small flow discharge, the maximum velocity occurs in the vicinity of concave bank. For the case of large discharge, the maximum velocity occurs near the center part of the channel. Consequently, bed deformation patterns in meandering channels will be influenced by the flow conditions.

The environment of major sediments of eastern China oilfields is a meandering river where mud drapes inside point bar sand occur and are recognized as important factors for underground fluid flow and distribution of the remaining oil. The present detailed architectural analysis, and the related mud drapes’ modeling inside a point bar, is practical work to enhance oil recovery. This paper illustrates a new stochastic modeling of mud drapes inside point bars. The method is a hierarchical strategy and composed of three nested steps. Firstly, the model of meandering channel bodies is established using the Fluvsim method. Each channel centerline obtained from the Fluvsim is preserved for the next simulation. Secondly, the curvature ratios of each meandering river at various positions are calculated to determine the occurrence of each point bar. The abandoned channel is used to characterize the geometry of each defined point bar. Finally, mud drapes inside each point bar are predicted through random sampling of various parameters, such as number, horizontal intervals, dip angle, and extended distance of mud drapes. A dataset, collected from a reservoir in the Shengli oilfield of China, was used to illustrate the mud drapes’ building procedure proposed in this paper. The results show that the inner architectural elements of the meandering river are depicted fairly well in the model. More importantly, the high prediction precision from the cross validation of five drilled wells shows the practical value and significance of the proposed method.

The discharge process influences the morphological evolutions of alluvial rivers, even the channel pattern evolutions. The impacts of discharge processes on morphological evolutions in an experimental channel were investigated by a 3-D mathematical model, in which turbulence flow and sediment transport as well as bank erosion were modeling. The simulated results demonstrated that the discharge process had significant effects on morphological changes. Planfrom evolution in the period with large discharge was much more notable than that with small discharge. Different discharge processes may lead to different channel patterns. A single meandering channel was formed under steady flow condition. A braided channel was observed with unsteady flow condition.

Reliable estimates of discharge capacity in open channels are essential for the design, operation and maintenance of open channels, and more importantly the prediction of flood, water level management and flood design. The methods of discharge estimation that are used in the available river modelling software are principally based on historic hand-calculation formulae, with little or no account taken of the more recent advances in knowledge and understanding. The paper describes some of the conclusions of predicting discharge in meandering and straight compound channels with the proposed method by authors, the diversity of current knowledge and the outline of the targeted program of research that is now underway to produce an improved discharge estimation system. Particular issues of concern are the effects of the interaction between river channels and floodplain.

Ext reme co mplexit ies present in flow behavior of meandering compound channels necessitate the study and analysis of such channels under different geometric and hydraulic condition to further our knowledge in understanding the dependency of flo w characteristics e.g. velocity, boundary shear etc. on d ifferent sectional parameters like width rat io, aspect ratio and hydraulic parameter such as relative depth. The present paper draws on our investigations on a meandering compound channel,where physical experiments were conducted on a smooth sine generated trapezoidal main channel flanked on both sides by wide flood plainsunder different relative depths. A 2dimensional hydrodynamic model CCHE2D and another quasi1D model Conveyance estimation System (CES) were then applied in turn to the same test cases to numerically investigate the flow in the co mpound meandering channel. The results of such investigations were then compared for validation purpose with observed experimental values of important flow parameters like depth averaged velocity and boundary shear distribution across the channel cross section. It is seen that CCHE2D is quite capable of producing results in agreement with their physical values and also it partly agrees with results of CES.It is expected that the results shown in this paper would enrich the research data base in the field of co mpound channels and help the scientists in using the numerical model CCHE2D, as a viable research tool in the field of river engineering.

The braided Jamuna River frequently changes its courses. Sometimes the secondary channel in a braided river acts as a single thread meandering channel. In the present study an attempt has been made to investigate the flow patterns and to estimate the rate of bank erosion in a bend along the Jamuna River. The three dimensional (3D) flow velocities were measured using Acoustic Doppler Current Profiler (ADCP). It is found that the near bank velocity is amplified by 1.1 to 1.3 times as compared with the section averaged velocity. A dominant secondary current is found in the upstream bend. The evolution as well as decay of the secondary current is not as clear as it is found in the laboratory experiments. It is revealed from the analysis of the flow process that the causes of higher rate of erosion at the study bend are the oblique flow near bankline, six times amplified shear velocity than critical shear velocity near bankline and the secondary current which acts as a sediment transporting agent from the outer bank towards the inner bank or the sand bar. Based on the flow processes, a simplified erosion prediction model is developed and applied to estimate the rate of erosion at a selected bend. Finally the predicted results have been compared with the observed data at the bend and all the available data at other bends along the Jamuna River.

For preserving a comfortable river ecosystem, it is important to protect and restore the riffle and pools within engineered channels, where should play a role in the habitat diversity and complexity. It will be no easy task to restore and preserve the pool-riffle in flat rock-bed river which is lightly covered with gravels, as contrasted with in the gravel river. In the Abashiri River, the improvement by channel deepening projects with rock-bed has been carried out, in which was introduced to construct artificial pools. We investigate the restoration of the riffle and pools by constructing artificial pools. By field survey in the Abashiri River, the state of sediment on the improved channel is indicated. By undistorted model experiment, we investigate the deposition of artificial pools. As a result, it shows that the artificial constructed pools are corresponded to the location of generated ones in a mobile bed.

The present paper reports the findings of a study in which the appropriateness of using two-dimensional (2D) and three-dimensional (3D) numerical modelling in order to simulate the flow in a small reach of the river Blackwater, UK, was examined. The numerical simulations were compared with data obtained from a 1 : 5 scale physical model of the reach. A variety of turbulence models were used in order to evaluate their suitability and assess their impact on the simulations. In order to enable direct comparisons, all of the simulations were undertaken using a single modelling code, Delft3D. It was shown that 3D models offer significant advantages over 2D when applied to a meandering channel and that this choice outweighs the choice of turbulence model.

This paper is concerned with the numerical solution of two-dimensional flows in a rectangular meandering channel. The technique of boundary-fitted coordinate system is used to overcome the difficulties resulting from the complicated shape of natural river boundaries; the method of physical fractional steps is used to solve the partial differential equations in the transformed plane. Comparison between computed and experimental data shows a satisfactory agreement.

After a half century of exploration, the Malay Basin, a mature hydrocarbon province in SE Asia, faces common challenge that most of the conventional structural reservoirs have been drilled out. As a result, the high-risk stratigraphic traps are considered as viable alternative to boost the dwindling oil reserves. In Y field, the discovery of Early Miocene Group I meander belt channel sands outside the low-relief anticlinal closure is seemed to have made substantial contributions to the later oil production. This sparks the inspiration to develop a practical workflow in visualizing the subtle, yet productive channel systems through integration of multidisciplinary datasets. Results have proven that the co-rendering of multi-attributes could effectively delineate the channel edges and reflection strength of sand bodies. Moreover, through the application of neural network techniques on the extracted waveform shape of seismic attribute, a supervised hierarchical lithofacies map was generated. This can help to create a better linkage between the seismic waveform patterns and lithological details of subsurface features. Wireline log analysis was also performed to verify the hydrocarbon potential of Group I sands. This integrated approach may adopted as a reliable best practice in near-field exploration program, especially in proving up the channel-sand stratigraphic play.

Studies were carried out to understand the effect of floodplain roughness on flow structures, sediment transport rates and bedforms in a mobile meandering channel with overbank flows. Three floodplain roughnesses were examined in this study. Flow structures and bedforms were measured using a three component laser Doppler anemometer (LDA) system and digital photogrammetry, respectively. Comparisons of flow structures and bedforms between different floodplain rougheness are made. Considerable changes in the flow structure and bed form were observed. In particular, multiple secondary flow cells along the meandering channel occur at deeper water depths as the floodplain roughness increases. These cells also cause a series of wavy bedforms along the meandering channel. This paper is separated into two parts. Part I concentrates, in detail, on the flow structure with bedforms in the meandering channel for overbank flow as to change of floodplain roughness. The sister paper, Part II, concentrates on bed form for...

The purpose of this study is to investigate the characteristics of the flow through the Jonangu channel which is used for ceremonial game called as 'Kyokusui-no-En' in Japanese. The geometry of the channel is measured, a visualization technique is used to measure the actual flow characteristics, and then a numerical flow model is used to represent the flow including unsteady flow characteristics. Numerical model of drifting cup is introduced to investigate an interaction between flow and motion of the cup. Finally, the intention of the channel design is interpreted from the viewpoint of fluid mechanics using observed and calculated results.

The overflow discharges, under the overflow as well as submerged overflow conditions, from a meandering channel with or without retarding plantations into a flood plain are investigated experimentally and numerically. The analysis is directed toward the examination of the overflow discharges by the overflow discharge formula as well as the numerical analysis, simultaneously solving flows in a channel and inundation flows in a flood plain. The dynamic inundation analysis model used in the analysis comprises the finite volume method on unstructured grid using fluxdifference splitting (FDS) technique. We found that the model is much superior to the formula in predicting the overflow discharges with or without retarding plantations.

This study analyzed two dimensions hydraulic characteristic for actual flood events in steep meandering channel. It could get analysis results as follows; A water level difference of downstream more great than one of upstream at inner and outer of meandering channel. It judged that a significance of downstream level could appear more greatly in meandering channel bank, hydraulic structure and flood inundation analysis. As velocity and depth analysis was shown that much amount flow passing fast velocity happened in meandering channel, it could help establishment of meandering channel bank. In this study, the results of two dimension hydraulic analysis results could help a counterpaln establishment for the flood inundation and bank collapse.

Disasters causedby torrential downpours have recently been increasing throughout ournation. Inparticular, there have been many cases of flood damage on small and medium-sized rivers with relatively small design flood discharge in valley flats. Specific instances of this type damage include that which occurred in Tochigi Prefecture's Yosasa River in 1998, the Appetsu River in Hokkaido in 2003. These disasters are characterized by the flow of flood waters that were not confined to the river channel and caused damage to many houses, roads and bridges. In this study, we examined a method for adopting double Fourier analysis, which is used for shape analysis of the results of experiments on sediment hydraulics, to assess the flow channel geometry of an actual valley flat. The originof the terrain of the valley flat was estimated based on the results of sediment hydraulic studies, including experiments on compound meandering channel anddouble-row bar. The potential for utilizing the estimate results to predict the flow of flood waters and measures to reduce the impact of disasters at times of large-scale flooding in a valley flat was then indicated.

It is very important to reveal the coherent structure in meandering compound open-channel flows for predicting the transport properties of suspended sediments in rivers in flood. However, flow-visualization techniques such as PIV and PTV, have not sufficiently been applied to such flows in previous studies, and thus, there is almost no detailed information on coherent turbulence in meandering compound open-channel flows. Therefore, in this study, we conducted some PIV measurements with high-speed CMOS camera. As the results, the time-averaged velocity properties and coherent turbulence structure were investigated and discussed.

Qualitative and quantitative taphonomic data for the freshwater mollusk shells from death assemblages found in straight and meandering fluvial channels of the Touro Passo Stream, southern Brazil, are here presented. A total of 245 gastropod and 485 bivalve shells were collected and analyzed. Complete valves, showing small chipped margins, dominated the studied shell material. The periostracum was present in the great majority of the mollusk shells, and the ligament was preserved in more than 50% of the studied bivalves. Gastropod shells were intensively (50% to 80%) encrusted by periphyton and Potamolithus egg capsules. Corrasion is one of the main taphonomic signatures exhibited by the mollusk shells, and are represented by small to large pits and holes found in the internal and external shell surfaces. Some evidences indicate that these were acquired soon after death or even during life. Clearly, the presence/absence and the degree of taphonomic alteration of the shells were mediated by intrinsic factors. Some life habits make difficult the determination of post-mortem nature of some taphonomic signatures. In addition, taphonomic signatures do not vary predictably in shells from thanatocoenoses found in the straight or meandering channels. In part, this is due to the reworking of the Pleistocene mollusk shells from fossil-rich layers found in the sandstones of point bar deposits of the meandering channel. Some qualitative and quantitative data are very similar to those found in shells from muddy, organic rich marine bottoms, where acid conditions prevail. In fact, dissolution seems to be the main taphonomic process affecting the shells from the Touro Passo Stream assemblages. However, abrasion is also important in shell damage and roundness, especially in the shells found in assemblages of the straight channel. The spatial mixing and reworking of shells from the studied fluvial subenvironments, the mixture of recently dead shell with fossil remains, and the complex origin of some taphonomic signatures indicate that paleoenvironmental reconstructions, based on freshwater mollusks shells, must be carefully achieved and complemented by sedimentologic and stratigraphic data, even when conducted in typical potamic areas. RESUMO - Dados tafonomicos qualitativos e quantitativos para conchas de moluscos de aguas doces, encontrados em canais fluviais retilineos e meandrantes, do riacho Touro Passo, sul do Brasil, sao aqui apresentados. No total, 245 conchas de gastropodes e 485 conchas de bivalves foram coletadas e analisadas. Conchas completas, com margens lascadas dominam as assembleias estudadas. Periostraco esta presente na grande maioria das conchas examinadas e o ligamento esta preservado em cerca de 50% das conchas de bivalves estudados. Conchas de gastropodes estao intensamente (50% a 80%) cobertas por perifiton e capsulas de ovos de Potamolithus. Corrosao e a principal assinatura tafonomica exibida pelas conchas de moluscos, sendo representada por perfuracoes de pequeno a grande porte, encontradas tanto na superficie externa, como interna das conchas. Algumas evidencias indicam que estas feicoes foram adquiridas rapidamente apos a morte ou mesmo em vida. Claramente, a presenca/ausencia e o grau de alteracao tafonomica de muitas conchas foram influenciados por fatores intrinsecos. Alguns modos de vida, como o de epifauna, tornam dificil a determinacao do carater post-mortem de algumas assinaturas tafonomicas (e.g., incrustacao, abrasao). Ainda, as assinaturas tafonomicas nao variam previsivelmente segundo os subambientes estudados (lotico e lentico). Em parte, tal fato decorre do retrabalhamento e mistura de conchas de moluscos pleistocenicos, dada a erosao de arenitos fossiliferous, em depositos de barras de pontal, junto ao canal meandrante. Alguns dados qualitativos e quantitativos (e.g., alta proporcao de conchas com dissolucao) sao similares aos verificados em ambientes marinhos, com substratos argilosos, ricos em material orgânica e agua intersticial acida. De fato, dissolucao/corrosao sao os principais agentes tafonomicos de alteracao das conchas das assembleias do rio Touro Passo. A abrasao e tambem um agente tafonomico importante, especialmente no canal retilineo. A mistura espacial e o retrabalhamento de conchas entre os subambientes amostrados, a mistura de conchas recentemente mortas, com restos esqueletais pleistocenicos e subfosseis, e a complexa origem de algumas assinaturas tafonomicas indicam que as reconstrucoes paleoambientais fundamentadas em assembleias de moluscos de aguas doces deve ser feita com cautela e complementadas por dados sedimentologicos e estratigraficos, mesmo quando em ambientes potâmicos.

A computer model was proposed to simulate channel changes and bed material sorting of the meandering channels with different grain size in time and space simultaneously. The bed at the outside of the meandering channel with mixed sediments was scoured deeply and composed of coarser materials, and at the inside was aggradated and composed of finer materials. The sorting process started at the upstream inflection point and was finished at the downstream inflection point. At the natural with complicated boundaries and non-uniform grain sizes, the bed near the outside at the bend and narrow width was scoured deeper with coarse materials than in the channel with uniform grain sizes. The point bars showed lip at the inside near the bend and the bed materials were finer The bed at the outside near the bend and in the narrow width was scoured deeply with the coarser materials.

It is important to evaluate the effect of vane works not only in the simple uniform bend but also in the reach of various forms in river. In this study we investigate the effects of vane works reducing scour depth in the compound channel whose plan form changes longitudinally. In this paper, at first we describe the idea of the design of vane works based on the recent topics of the flow and bed topography characteristics in a compound meandering channel, and show vane works fulfill their functions through flood from vane's effects in simple and compound channel flows. Bed variation in a channel with vane works is reproduced by using 3D-flow model considering drag and lift forces exerting on vanes.

In the previous studies on compound channel flows, experimental channels of simplified plan shape, straight or uniform sinuosity have been used. However, rivers generally consist of reaches of different plan shapes continuously. Therefore, it is important to clarify as a whole effect of channel shape and hydraulic condition on flow and bed formation. In this paper, effects of plan shape and relative depth on sediment discharge were examined And characteristics of flow and bed topography were investigated in a compound channel consisting of different plan shape (straight, curved and meandering). As the results, sediment discharge in compound straight and meandering channel showed a different manner with relative depth variation. And flow and bed topography were affected mainly by the upstream channel shape. Especially, at transition section from straight to meandering maximum scouring occurred due to non-equilibrium of sediment discharge with large relative depth.

The experimental study reported herein was carried out in a meandering flume with three consecutive bends. The radius-width ratio was 3 and the arc angles of each bend were 40°, 80° and 40° respectively. The study was performed for various cases of with and without structures. Non-submerged spur dikes were placed as river training structure in concave part of the bend entrance. The flow field without spur dikes, with one, two and three spur dikes was measured under similar flow condition in order to assess the influence of the structures on flow pattern. For the sake of comparability, the velocity field throughout the bend reach has been measured in all cases and depicted in non-dimensional form. Some specific features associated with the flow processes in a mildly meandering channel were observed. Of most notable observation in this study is the existence of a dead region near the outer part of subsequent bend induced by the structures placed in bend entrance.

A project of river channel restoration has been promoted in the Shibetsu River, that attempts to restore the natural meander channel remained as a oxbow lake by letting the river water run through. In this project, it is intended that water streams into both the restored meandering channel and the straightened current river course by a small dam constructed downstream of the bifurcation point. But there are few papers treating the relationship between bifurcated flow ratio and the height of a dam in such complex channel system. This study is devoted to investigate the regulation function of a dam for bifurcated flow rate into an oxbow channel. Theoretical solutions for the flow rate are derived from the momentum balance of the several controlvolume sections of the bifurcated area. The results are compared with observed data in model tests and in field survey at a study section of the Shibetsu River to show good agreement.

Laboratory experiments were carried out to elucidate the influence of riparian vegetation on braided rivers with unconstrained banks. One run for barided river without vegetation from initial straight channel and two kinds of runs for the river with vegetation were conducted. For the vegetated braided river alfalfa seed was introduced to the channel by controlling the density. In this study, flow characteristics and channel evolution to explain vegetation effects in braided river were investigated. Especially in morphological behavior, a primary channel was developed to a high meandering channel and bifurcated to two channels due to vegetation on the bed and banks. And numerical model is applied to investigate the effect of vegetation in braided river with and without vegetation and the results are discussed.

北海道東部の音更川では、平成23年9月および平成28年9月の出水において堤防の流出や大規模な河岸浸食が生じた．洪水後の調査により大規模な河岸浸食の多くは蛇行流路の発達によるものと推定され，蛇行流路の発達には砂州と呼ばれる中規模河床波の形成が大きく関わっているものと考えられるものの，実河川における出水時の中規模河床波の形成過程に関する知見はその複雑性ゆえに未だ十分ではない． よって本研究では，音更川の既往の4つの主要出水を対象として非定常流下における線形安定解析を適用し，出水中における単列砂州と複列砂州の増幅率の関係から中規模河床波の発達特性を示したほか，蛇行流路の発達は中規模河床波の形態に大きく影響を受けていることを示した．, Four large-scale floods (1981-Flood, 2003-Flood, 2011-Flood and 2016-Flood) have attacked the Otofuke River in these 40 years. By each flood, the responses of the river channel differed greatly. It was assumed that the difference of responses were caused by the difference of bar formation during floods. In this study, linear stability analysis on bar formation under unsteady flow conditions using the data at 4 floods. The results of analysis are reproducing the situation of the 4 floods. As a result, it became clear that the river management fully needs to understand the bar formation process at the descending period of floods.

The meandering process has always been the topic through years and still remains a lot of unsolved mysteries. One of the most important focus is the migration architectures and models that the meandering channels follow. This article chooses the Nowitna River as the study object of the typical meandering river with high migratory processes. Though the high-resolution historical satellite images by the techniques of Google Earth and ACME Mapper, 50 meanders in the river is studied and 6 of which are chosen for meticulous characterization. During the process, the planform structure of meandering channel is re-examined and 29 kinds of architecture elements are systematically established. More importantly, in order to make a fine quantitative characterization of the channel structure of meandering river, 5 kinds of characterization parameters are proposed, extraordinarily, the parameters of the difference of along-current deflection angle, a difference of counter-current deflection angle, and expansion coefficient, these three are firstly brought forward and applied introduction. In addition, the conception of sinuosity index and curvature are also different from the original definition. Though these architectures elements the meandering process and migration structure of the Nowitna River is demonstrated. 6 kinds of planform migration structures is revealed with the quantitative characterization of characterization parameters and 9 species of meandering channel migration patterns are concluded and discussed.