The objective of this study was to examine the flow characteristic by changing the length of groyne in the degree of -20%, -10%, +10%, and +20% with standard groyne (55m) as its reference by applying 2D flow analysis model SMS RMA-2 model with 5 sections of naturally curved channel as its subject. P...
The objective of this study was to examine the flow characteristic by changing the length of groyne in the degree of -20%, -10%, +10%, and +20% with standard groyne (55m) as its reference by applying 2D flow analysis model SMS RMA-2 model with 5 sections of naturally curved channel as its subject. Parameter calibration was conducted in order to examine the compatibility of model. In regards to flux applied to groyne flow was selected as hydrologic condition of water reserve and design flood level (100yr). Then, analysis was conducted on the distribution of velocity and sedimentation occurrence point based on change in length of groyne. The result of analyzing hydraulic characteristic generated from groyne group and adjacent part is as following. Impermeable groyne was used this in this study and it was revealed that there was an increase in upstream and downstream flow of channel installed with groyne. It was revealed to be 0.001m/s∼0.234m/s in case of standard groyne installation at natural channel. With the change in degree of -20%, -10%, +10%, and +20%, the flow was 0.227m/s, 0.231m/s, 0.238m/s, and 0.241m/s respectively presenting the change of about -3%, -1.3% +1.7%, and 2.9%. With the decrease in length of groyne, there was an increase in cross-section of channel. With the increase in length of groyne, there was an increase in flow followed by reduction in water flow cross section. It was revealed that there is a dramatic increase in flow toward exterior of river cross-sectional area with the increase in length of naturally curved channel. Therefore, it was determined that short length of groyne has more advantages in aspect of river bed stability. The sedimentation was occurred at all sections between groynes when installing groyne at curved channel. There was a decrease in sedimentation section toward lower stream. It was analyzed that there is an occurrence of scouring rather than sedimentation in direct downstream exterior of last groyne toward downstream. It was revealed that more sedimentation occurs in order of outlet section, middle section, and entrance section of groyne upon shortening of groyne's length. Also, it was examined that there is an increase in flow change between groynes with the shortening of groyne's length. Although there was an increase in sedimentation point between first groyne with the decrease in length of groyne at the point where channel presents long river valley length, it was analyzed that there is a decrease in length of sedimentation at second section. With the decrease in sinuosity, there was a high degree of change in length at the point of sedimentation for groyne with increase in length. When groyne was installed at curved part, swirl was formed in all groynes at about 3/4 point toward center from bank and end of groyne. Primary swirl was presented for standard groyne and groynes with length change of -10% and -20% and two swirls were generated with the increase in length of groyne by +10% and +20%. Although there was a high probability of channel erosion, scouring, sandbar phenomenon, sedimentation, and others before installation of groyne at naturally curved channel, consistent and balanced channel flow has occurred at curved part with installation of groyne. Therefore, it was determined that high level of contribution could be made to river environment before groyne installation to curved part with the protection of river bed, stability of bank protection, and sedimentation at emergency compared to before groyne installation.
The objective of this study was to examine the flow characteristic by changing the length of groyne in the degree of -20%, -10%, +10%, and +20% with standard groyne (55m) as its reference by applying 2D flow analysis model SMS RMA-2 model with 5 sections of naturally curved channel as its subject. Parameter calibration was conducted in order to examine the compatibility of model. In regards to flux applied to groyne flow was selected as hydrologic condition of water reserve and design flood level (100yr). Then, analysis was conducted on the distribution of velocity and sedimentation occurrence point based on change in length of groyne. The result of analyzing hydraulic characteristic generated from groyne group and adjacent part is as following. Impermeable groyne was used this in this study and it was revealed that there was an increase in upstream and downstream flow of channel installed with groyne. It was revealed to be 0.001m/s∼0.234m/s in case of standard groyne installation at natural channel. With the change in degree of -20%, -10%, +10%, and +20%, the flow was 0.227m/s, 0.231m/s, 0.238m/s, and 0.241m/s respectively presenting the change of about -3%, -1.3% +1.7%, and 2.9%. With the decrease in length of groyne, there was an increase in cross-section of channel. With the increase in length of groyne, there was an increase in flow followed by reduction in water flow cross section. It was revealed that there is a dramatic increase in flow toward exterior of river cross-sectional area with the increase in length of naturally curved channel. Therefore, it was determined that short length of groyne has more advantages in aspect of river bed stability. The sedimentation was occurred at all sections between groynes when installing groyne at curved channel. There was a decrease in sedimentation section toward lower stream. It was analyzed that there is an occurrence of scouring rather than sedimentation in direct downstream exterior of last groyne toward downstream. It was revealed that more sedimentation occurs in order of outlet section, middle section, and entrance section of groyne upon shortening of groyne's length. Also, it was examined that there is an increase in flow change between groynes with the shortening of groyne's length. Although there was an increase in sedimentation point between first groyne with the decrease in length of groyne at the point where channel presents long river valley length, it was analyzed that there is a decrease in length of sedimentation at second section. With the decrease in sinuosity, there was a high degree of change in length at the point of sedimentation for groyne with increase in length. When groyne was installed at curved part, swirl was formed in all groynes at about 3/4 point toward center from bank and end of groyne. Primary swirl was presented for standard groyne and groynes with length change of -10% and -20% and two swirls were generated with the increase in length of groyne by +10% and +20%. Although there was a high probability of channel erosion, scouring, sandbar phenomenon, sedimentation, and others before installation of groyne at naturally curved channel, consistent and balanced channel flow has occurred at curved part with installation of groyne. Therefore, it was determined that high level of contribution could be made to river environment before groyne installation to curved part with the protection of river bed, stability of bank protection, and sedimentation at emergency compared to before groyne installation.
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