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Joon Gu Kang - One of the best experts on this subject based on the ideXlab platform.
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An Experimental Study on Flow Characteristics for Optimal Spacing Suggestion of 45° Upward Groynes
Journal of Korea Water Resources Association, 2014Co-Authors: Sung Joong Kim, Joon Gu Kang, Hongkoo YeoAbstract:Groyne to control the direction and velocity of flow in rivers is generally installed for the purpose of protecting riverbanks or embankments from erosion caused by running water. In particular, as interest in river restoration and natural river improvement increases, Groynes are proposed as a key hydraulic structure for local flow control and riparian habitat establishment. Groynes are installed mainly in groups rather than as individual structures. In case of Groynes installed as a group, flow around the Groynes change according to spacing in between the Groynes. Therefore, Groyne spacing is regarded as the most important factor in Groyne design. This study aimed at examining changes of flows around and within the area of Groynes that take place according to the spacing of Groynes installed in order to propose the optimal spacing for upward Groynes. To examine flow characteristics around Groynes, this study looked at flows in main flow area and recirculation flow area separately. In main flow area, it examined the impact of flow velocity increasing as a result of conveyance reduction that is exerted on river bed stability in relation to changes in the maximum flow velocity according to installation spacing. As a factor causing impacts on scouring and sedimentation within the area of Groynes, recirculation flow in the Groyne area can lead problems concerning flow within the area and stability of embankment. As for recirculation area, an analysis was conducted on the scale of rotational flow and the flow around embankment that exerts impacts on stability of the embankment. In addition, a compara- tive analysis was carried with reference to changes of the central point of rotational flow that occur within the area of Groynes. As a result of compositely examining the results, the appropriate installation spacing is proposed as min. four times-max. six times considering a decrease in flow velocity according to the installation of upward Groynes, river bed stability and stability of embankments against counterflow within the area of Groynes.
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Assessment of Habitats According to Groyne Types (Using Pale Chub)
Engineering, 2013Co-Authors: Joon Gu Kang, Hongkoo Yeo, Changsung KimAbstract:A Groyne zone formed by installing Groynes functions as habitat or shelter for aquatic organisms during a flood. Since flow characteristics over a Groyne zone are affected directly by Groynes, understanding flow patterns due to shapes and types of Groynes is of importance for designing Groynes. In order to use Groynes as an eco-friendly river structure, the ecological effects should also be considered at the design stage. In Korea, the ecological effects of Groynes have rarely been examined or included for the actual design. In this study, a set of experiments were carried out to investigate flow pattern changes depending on different types of Groynes. Based on the flow characteristics in the Groyne zone, the scales of habitats and shelters by the Groyne types were estimated. In addition, to test the applicability of a habitat evaluation model to the ecological design of Groynes, River2D was used for a virtual river. For assessment of the Groyne’s function of ecological habitat, the suitability index of a habitat for pale chub, one of the popular fishes in Korea, was used and the habitat areas by the Groyne types were analyzed. The flow changes depending on the Groyne types simulated by River2D show the applicability for the simulation of an ecological habitat to the Groyne design.
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An Experimental Study on a Characteristics of Flow around Groyne Area by Install Conditions
Engineering, 2012Co-Authors: Joon Gu Kang, Hongkoo Yeo, Changsung KimAbstract:In designing group Groynes, the space of the Groynes is an important factor, and the flow between the Groyne areas will vary along the space. Since the flow in the Groyne field significantly affects the flow change, the bed change, the bank erosion and the condition of the habitat, an assessment of the flow along the space of the Groynes will yield important data needed to diversify the object of the Groyne installation. To provide basic data for the determination of the proper space of Groynes in a Groyne group, the flow in the channel and Groyne field, which varies with the installation of the Groyne, is herein analyzed. The space of the Groynes was set from the same length to 12 times the length of the Groyne, and the flow range was measured using the LSPIV method and ADV. The influence of the angle of the installation was also analyzed. As a result, through the flow configuration in the Groyne field and the flow range at the center of the Groyne field against the space of the Groyne, the decreasing influence of Groyne erosion was suggested by the analysis of the shelter effect of aquatics and the countercurrent in the bank line.
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experimental study on the flow characteristics of type Groyne
Engineering, 2011Co-Authors: Joon Gu Kang, Hongkoo YeoAbstract:A hydraulic model test for ￢-type Groynes (with “￢” shape) was conducted to analyze the flow characteristics around these Groynes. The results of the model tests are expected to be used as fundamental information in designing the ￢-type Groyne constructed in the field. Main hydraulic factors such as velocity and thalweg line changes in the main channel and separation area were analyzed in this study. The thalweg line is a stream line where the maximum velocity occurs, whereas the separation area is the boundary between the main flow and the recirculation zone. Model tests with 5 different arm lengths of the ￢-type Groynes were conducted by changing the velocity. The LSPIV (Large-Scale Particle Image Velocimetry) technique was used to measure and analyze flow variation around the ￢-type Groynes. The velocity in the main channel measured to be increased by 1.5 times. The velocity variation on Groyne arm length is little. The width of the thalweg lines (TCL) was changed to 55 - 57% of the channel width. The Froude number did not affect the thalweg line (TCL) and separation line (Sh) changes, however.
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Experimental Study on the Flow Characteristics around the Refraction Groyne
Engineering, 2011Co-Authors: Joon Gu Kang, Hongkoo Yeo, Sungjung KimAbstract:The refraction Groyne is a complex structure consisted with Groyne and Groyne’s arm. This study conducted a experiment on the flow influences around the refraction Groyne due to changes in the arm angle (θ) and length (AL). Results of experiment were analyzed on the impacts of the refraction Groyne according to the projection length (L’). Velocity increase in main channel occurred greater the upward Groynes than downward Groynes. The vortices occurring at recirculation area of the upward and downward refraction Groynes were formed in different shapes. The thalweg height did not have great impact vis-a-vis the extended arm length ratio and refraction angle change. The length of the recirculation area showed a gradual uptrend as the arm length of the Groyne increased. Such area was formed at the range of 29% - 47%. For the length of the recirculation area, it was observed to be 10.2 - 14.7 times (URG), 8.4 - 12.7 times (DRG), and 10.6 - 13.8 times (right angle Groyne) the projection length (L’) incensement.
Hongkoo Yeo - One of the best experts on this subject based on the ideXlab platform.
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An Experimental Study on Flow Characteristics for Optimal Spacing Suggestion of 45° Upward Groynes
Journal of Korea Water Resources Association, 2014Co-Authors: Sung Joong Kim, Joon Gu Kang, Hongkoo YeoAbstract:Groyne to control the direction and velocity of flow in rivers is generally installed for the purpose of protecting riverbanks or embankments from erosion caused by running water. In particular, as interest in river restoration and natural river improvement increases, Groynes are proposed as a key hydraulic structure for local flow control and riparian habitat establishment. Groynes are installed mainly in groups rather than as individual structures. In case of Groynes installed as a group, flow around the Groynes change according to spacing in between the Groynes. Therefore, Groyne spacing is regarded as the most important factor in Groyne design. This study aimed at examining changes of flows around and within the area of Groynes that take place according to the spacing of Groynes installed in order to propose the optimal spacing for upward Groynes. To examine flow characteristics around Groynes, this study looked at flows in main flow area and recirculation flow area separately. In main flow area, it examined the impact of flow velocity increasing as a result of conveyance reduction that is exerted on river bed stability in relation to changes in the maximum flow velocity according to installation spacing. As a factor causing impacts on scouring and sedimentation within the area of Groynes, recirculation flow in the Groyne area can lead problems concerning flow within the area and stability of embankment. As for recirculation area, an analysis was conducted on the scale of rotational flow and the flow around embankment that exerts impacts on stability of the embankment. In addition, a compara- tive analysis was carried with reference to changes of the central point of rotational flow that occur within the area of Groynes. As a result of compositely examining the results, the appropriate installation spacing is proposed as min. four times-max. six times considering a decrease in flow velocity according to the installation of upward Groynes, river bed stability and stability of embankments against counterflow within the area of Groynes.
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Assessment of Habitats According to Groyne Types (Using Pale Chub)
Engineering, 2013Co-Authors: Joon Gu Kang, Hongkoo Yeo, Changsung KimAbstract:A Groyne zone formed by installing Groynes functions as habitat or shelter for aquatic organisms during a flood. Since flow characteristics over a Groyne zone are affected directly by Groynes, understanding flow patterns due to shapes and types of Groynes is of importance for designing Groynes. In order to use Groynes as an eco-friendly river structure, the ecological effects should also be considered at the design stage. In Korea, the ecological effects of Groynes have rarely been examined or included for the actual design. In this study, a set of experiments were carried out to investigate flow pattern changes depending on different types of Groynes. Based on the flow characteristics in the Groyne zone, the scales of habitats and shelters by the Groyne types were estimated. In addition, to test the applicability of a habitat evaluation model to the ecological design of Groynes, River2D was used for a virtual river. For assessment of the Groyne’s function of ecological habitat, the suitability index of a habitat for pale chub, one of the popular fishes in Korea, was used and the habitat areas by the Groyne types were analyzed. The flow changes depending on the Groyne types simulated by River2D show the applicability for the simulation of an ecological habitat to the Groyne design.
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An Experimental Study on a Characteristics of Flow around Groyne Area by Install Conditions
Engineering, 2012Co-Authors: Joon Gu Kang, Hongkoo Yeo, Changsung KimAbstract:In designing group Groynes, the space of the Groynes is an important factor, and the flow between the Groyne areas will vary along the space. Since the flow in the Groyne field significantly affects the flow change, the bed change, the bank erosion and the condition of the habitat, an assessment of the flow along the space of the Groynes will yield important data needed to diversify the object of the Groyne installation. To provide basic data for the determination of the proper space of Groynes in a Groyne group, the flow in the channel and Groyne field, which varies with the installation of the Groyne, is herein analyzed. The space of the Groynes was set from the same length to 12 times the length of the Groyne, and the flow range was measured using the LSPIV method and ADV. The influence of the angle of the installation was also analyzed. As a result, through the flow configuration in the Groyne field and the flow range at the center of the Groyne field against the space of the Groyne, the decreasing influence of Groyne erosion was suggested by the analysis of the shelter effect of aquatics and the countercurrent in the bank line.
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experimental study on the flow characteristics of type Groyne
Engineering, 2011Co-Authors: Joon Gu Kang, Hongkoo YeoAbstract:A hydraulic model test for ￢-type Groynes (with “￢” shape) was conducted to analyze the flow characteristics around these Groynes. The results of the model tests are expected to be used as fundamental information in designing the ￢-type Groyne constructed in the field. Main hydraulic factors such as velocity and thalweg line changes in the main channel and separation area were analyzed in this study. The thalweg line is a stream line where the maximum velocity occurs, whereas the separation area is the boundary between the main flow and the recirculation zone. Model tests with 5 different arm lengths of the ￢-type Groynes were conducted by changing the velocity. The LSPIV (Large-Scale Particle Image Velocimetry) technique was used to measure and analyze flow variation around the ￢-type Groynes. The velocity in the main channel measured to be increased by 1.5 times. The velocity variation on Groyne arm length is little. The width of the thalweg lines (TCL) was changed to 55 - 57% of the channel width. The Froude number did not affect the thalweg line (TCL) and separation line (Sh) changes, however.
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Experimental Study on the Flow Characteristics around the Refraction Groyne
Engineering, 2011Co-Authors: Joon Gu Kang, Hongkoo Yeo, Sungjung KimAbstract:The refraction Groyne is a complex structure consisted with Groyne and Groyne’s arm. This study conducted a experiment on the flow influences around the refraction Groyne due to changes in the arm angle (θ) and length (AL). Results of experiment were analyzed on the impacts of the refraction Groyne according to the projection length (L’). Velocity increase in main channel occurred greater the upward Groynes than downward Groynes. The vortices occurring at recirculation area of the upward and downward refraction Groynes were formed in different shapes. The thalweg height did not have great impact vis-a-vis the extended arm length ratio and refraction angle change. The length of the recirculation area showed a gradual uptrend as the arm length of the Groyne increased. Such area was formed at the range of 29% - 47%. For the length of the recirculation area, it was observed to be 10.2 - 14.7 times (URG), 8.4 - 12.7 times (DRG), and 10.6 - 13.8 times (right angle Groyne) the projection length (L’) incensement.
Huib J. De Vriend - One of the best experts on this subject based on the ideXlab platform.
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Flow Details near River Groynes: Experimental Investigation
Journal of Hydraulic Engineering, 2011Co-Authors: M.f.m. Yossef, Huib J. De VriendAbstract:Experiments have been carried out in a fixed-bed flume for a schematized straight river reach with Groynes on one side to study the dynamics of the flow near Groynes. The flume had a geometrical scale of 1:40, based on typical dimensions of the Dutch River Waal. Both emergent and submerged Groynes were studied. The measurements demonstrate the differences in the nature of the turbulence between submerged and emerged Groynes stages; and provide insight into the flow pattern in the vicinity of Groynes, the shape and the extent of the mixing layer at different flow stages, and the dynamic behavior of the velocity along the mixing layer between the main channel and the Groyne fields. A parameterization of the turbulence characteristics of the flow near Groynes is presented. Large-scale velocity fluctuations are found in all test cases, with timescales that vary with the flow stage. The large-scale u and v velocity fluctuations are in phase in the center of the mixing layer and out of phase for the points on the boundaries of the mixing layer.
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sediment exchange between a river and its Groyne fields mobile bed experiment
Journal of Hydraulic Engineering, 2010Co-Authors: M.f.m. Yossef, Huib J. De VriendAbstract:Experiments have been carried out in a mobile-bed laboratory flume in order to study the sediment exchange process between the main channel and the Groyne fields. The flume represented half the width of a schematized river reach with a series of Groynes. The experiment was designed to represent typical dimensions of the Dutch River Waal at a geometrical scale of 1:100. The conditions were set to guarantee bed load as well as suspended load sediment transport. Conditions with submerged and emerged Groynes were investigated. In addition to traditional measurements, viz., bed-level changes, suspended sediment concentrations, and flow velocities, bed-form propagation was measured in two dimensions using a the particle image velocimetry technique. The results were analyzed with focus on sediment exchange mechanisms and sediment transport patterns. The results demonstrate that under all flow conditions there is a net import of sediment into the Groyne fields. The prevailing transport mechanisms vary with the fl...
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Mobile-bed experiments on the exchange of sediment between main channel and Groyne fields
2004Co-Authors: M.f.m. Yossef, Huib J. De VriendAbstract:The estimates of the sediment balance for the Rhine branches in the Netherlands during the last three decades and particularly during the high water period of 1995 shows that erosion/sedimentation in the Groyne fields plays a major role in the total sediment balance of the river (ten Brinke et al., 2001). In the present modelling practice, this role is not included in morphological predictions. To include the contribution of the Groyne fields in the total sediment balance of the river, we need to further understand the sediment exchange process between the main channel and the Groyne fields. For this reason, experiments have been conducted in a mobile-bed flume. The flume represents half the width of a schematised river reach with Groynes at the left side. The geometrical scale is 1:100, based on typical dimensions of the River Waal. The bed material was scaled to have bed load as well as suspended sediment transport. The flow conditions covered one situation with emerged Groynes and three with submerged Groynes. Bed level changes, suspended sediment concentrations, and flow velocities were measured. The results show that there is sediment deposition in the Groyne fields under emerged as well as submerged conditions. Furthermore, the results demonstrate the differences between the erosion and deposition patterns in the Groyne fields for the different flow conditions.
M.f.m. Yossef - One of the best experts on this subject based on the ideXlab platform.
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Flow Details near River Groynes: Experimental Investigation
Journal of Hydraulic Engineering, 2011Co-Authors: M.f.m. Yossef, Huib J. De VriendAbstract:Experiments have been carried out in a fixed-bed flume for a schematized straight river reach with Groynes on one side to study the dynamics of the flow near Groynes. The flume had a geometrical scale of 1:40, based on typical dimensions of the Dutch River Waal. Both emergent and submerged Groynes were studied. The measurements demonstrate the differences in the nature of the turbulence between submerged and emerged Groynes stages; and provide insight into the flow pattern in the vicinity of Groynes, the shape and the extent of the mixing layer at different flow stages, and the dynamic behavior of the velocity along the mixing layer between the main channel and the Groyne fields. A parameterization of the turbulence characteristics of the flow near Groynes is presented. Large-scale velocity fluctuations are found in all test cases, with timescales that vary with the flow stage. The large-scale u and v velocity fluctuations are in phase in the center of the mixing layer and out of phase for the points on the boundaries of the mixing layer.
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sediment exchange between a river and its Groyne fields mobile bed experiment
Journal of Hydraulic Engineering, 2010Co-Authors: M.f.m. Yossef, Huib J. De VriendAbstract:Experiments have been carried out in a mobile-bed laboratory flume in order to study the sediment exchange process between the main channel and the Groyne fields. The flume represented half the width of a schematized river reach with a series of Groynes. The experiment was designed to represent typical dimensions of the Dutch River Waal at a geometrical scale of 1:100. The conditions were set to guarantee bed load as well as suspended load sediment transport. Conditions with submerged and emerged Groynes were investigated. In addition to traditional measurements, viz., bed-level changes, suspended sediment concentrations, and flow velocities, bed-form propagation was measured in two dimensions using a the particle image velocimetry technique. The results were analyzed with focus on sediment exchange mechanisms and sediment transport patterns. The results demonstrate that under all flow conditions there is a net import of sediment into the Groyne fields. The prevailing transport mechanisms vary with the fl...
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Mobile-bed experiments on the exchange of sediment between main channel and Groyne fields
2004Co-Authors: M.f.m. Yossef, Huib J. De VriendAbstract:The estimates of the sediment balance for the Rhine branches in the Netherlands during the last three decades and particularly during the high water period of 1995 shows that erosion/sedimentation in the Groyne fields plays a major role in the total sediment balance of the river (ten Brinke et al., 2001). In the present modelling practice, this role is not included in morphological predictions. To include the contribution of the Groyne fields in the total sediment balance of the river, we need to further understand the sediment exchange process between the main channel and the Groyne fields. For this reason, experiments have been conducted in a mobile-bed flume. The flume represents half the width of a schematised river reach with Groynes at the left side. The geometrical scale is 1:100, based on typical dimensions of the River Waal. The bed material was scaled to have bed load as well as suspended sediment transport. The flow conditions covered one situation with emerged Groynes and three with submerged Groynes. Bed level changes, suspended sediment concentrations, and flow velocities were measured. The results show that there is sediment deposition in the Groyne fields under emerged as well as submerged conditions. Furthermore, the results demonstrate the differences between the erosion and deposition patterns in the Groyne fields for the different flow conditions.
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The effect of Groynes on rivers: Literature review
2002Co-Authors: M.f.m. YossefAbstract:Groynes are structures constructed at an angle to the flow in order to deflect the flowing water away from critical zones. They are made of stone, gravel, rock, earth, or piles, beginning at the riverbank with a root and ending at the regulation line with a head. They serve to maintain a desirable channel for the purpose of flood control, improved navigation and erosion control. In the River Rhine, which is considered the backbone of North-western European waterways network, the primary objective of Groynes is to provide a fairway of sufficient depth and width. For example the River Waal, the most important branch of the Rhine River in the Netherlands is regulated by around 500 Groyne. Within the framework of the research project "Space for the Rhine Branches" several measures have been devised to achieve a decrease of the water levels at peak discharges, one of those measures, is lowering of the existing Groynes. The rationale behind this proposal is that; due to large-scale erosion of the low-water bed through the past decades, the Groynes are now higher than necessary for keeping the main channel at depth. Lowering the Groynes along certain reaches of the river would result in a reduction of the effective roughness during high water conditions thus, increasing the river's flood conveyance capacity. If the Groynes are lowered, however, the balance of hydrodynamic forces acting on the Groyne-fields will change, and there will be a large-scale morphological impact. To identify this impact, a thorough understanding to the effect o f Groynes on the morphology of the river is necessary. The sediment exchange between the Groyne-fields and the main channel needs to be more comprehensible. The purpose of this report is to acquire the background knowledge required to study the effect of Groynes on a river. The characteristics of the existing Groyne-fields along the Waal River are presented. The hydrodynamic and morphological impact of Groynes on a river is described. Moreover, because navigation plays an important role in the interaction between the Groyne fields and the main channel, the navigation induced water motion and its effect on the flow in Groyne-fields is described. Finally, a review of some prediction attempts to the interaction between the Groyne-fields and the main channel is presented.
Tetsuro Tsujimoto - One of the best experts on this subject based on the ideXlab platform.
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Optimum configuration of Groynes for stabilization of alluvial rivers with fine sediments
International Journal of Sediment Research, 2012Co-Authors: Mohammed Alauddin, Tetsuro TsujimotoAbstract:Abstract Severe bank erosion at lowland rivers in Bangladesh devours vast tract of lands and renders thousands of people homeless at high flood; also, rapid deposition changes bed topographies and seriously reduces navigability at low flow time. Conventional Groynes and revetments are used to mitigate these problems, but the targeted goal is not achieved as expected. This study investigates the optimum configuration of a Groyne to improve Groyne performances at both high flow and low flow. RIC-Nays, a two-dimensional model for flow and morphology, is utilized in this study upon confirmation through the detailed experimental data. The channel and flow parameters are taken conforming to a typical river of Bangladesh. Three different configurations are compared to obtain the optimum one. The performance of a Groyne is evaluated through three key features – erosion in channel bed (thalweg), deposition in Groyne field, and scour near Groynes. The computation reveals that the modified Groynes function better than the conventional ones in respect of maintenance of navigation channel at low flow and bank protection at high flood as well.
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Design of Groynes modified with both alignment and permeability for lowland river problems
Journal of Japan Society of Civil Engineers Ser. A2 (Applied Mechanics (AM)), 2011Co-Authors: M. Alauddin, Takashi Tashiro, Tetsuro TsujimotoAbstract:A Groyne is an important river restoration structure. Although its history is for long and widespread use, optimized design of new Groynes is not attempted much, which is very important to treat the highly unstable lowland river channels. A completely blocked impermeable Groyne suffers from instability of the structure itself; whereas, fully permeable structure can not divert the flow rightly. Considering the present demands, four different Groyne structures including modified combined and bandal-structures are examined in the laboratory channel to recognize their fluvial responses, incorporation with some field information. The performance of a Groyne is confirmed through three key features: scour near Groynes (structure stability), deposition in the Groyne field (bank stability) and erosion in channel bed (navigability). Analyses of data show that the combined Groynes cause gradual deceleration of flow towards the land and minimize local scour compared with the conventional impermeable ones. Also two other important features: deposition near bank and channel erosion, are better responded from modified bandal-structures and modified combined Groyne.
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OPTIMUM DESIGN OF GroyneS FOR STABILIZATION OF LOWLAND RIVERS
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 2011Co-Authors: M. Alauddin, Tetsuro TsujimotoAbstract:Alluvial rivers at low land as in Bangladesh are highly dynamic in nature; where huge landloss due to severe bank erosion at high flood as well as repeated interruptions of navigation system due to rapid sedimentation at low flow are very common. Groynes, revetments etc. are typically used to overcome these problems, but the goals are not achieved as expected. This study investigates the optimum design of a Groyne for its effective functioning. A 2D model, RIC-Nays is utilized in this study upon confirmation. The channel and flow parameters are based on conformity to a typical river of Bangladesh. Four orientations and three configurations of Groynes are considered here. The performance of Groynes is evaluated through three key indices erosion in channel bed (thalweg), deposition in Groyne field, and scour near Groyne-tip. Computations reveal that a modified Groyne functions better over the straight ones through protection of channel bank from erosion and maintenance of navigation channel as well.
