Pub Date : 2021-10-30DOI: 10.20481/kscdp.2021.8.4.307
Gweon-su Kim, Ha-sang Ryu, Sanghuk Kim
In order to solve the difficulty of performing a numerical model using a long-term wave time series, a method of reducing wave time series was considered. And Numerical simulation of the sediment by the Delft3d model at the Maengbang Beach was conducted to verify the validity of the method. NOAA wave data were collected for about 40 years from January 1979 to May 2019. Among them, waves, which are judged to have insignificant effect on the beach, were removed and the wave time series was reduced. To this end, the entire wave time series was graded at intervals of 0.5m, period 2sec, and wave direction 10° to generate a total of 749 representative waves, and a numerical simulation of sediment was performed for each representative wave for 1 day. When the maximum sediment height was less than 0.01m/day, it was assumed that the influence of the representative wave on the area was negligible. As a result of conducting numerical simulation of the sediment using the 23-month real-time waves and the wave by the reduced time series, the difference between the two simulation results indicates a local sedimentation difference of 0.1 to 0.5 m near Deokbongsan. There is a difference in sedimentation of 0.01 to 0.1m overall, and the pattern of repeated erosion and sedimentation along the entire coast is very similar to both real-time waves and reduced time series waves.
{"title":"A Method to Reduce the Calculation Time of Sediment Simulation by Controlling the Number of Long-term Wave Data","authors":"Gweon-su Kim, Ha-sang Ryu, Sanghuk Kim","doi":"10.20481/kscdp.2021.8.4.307","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.4.307","url":null,"abstract":"In order to solve the difficulty of performing a numerical model using a long-term wave time series, a method of reducing wave time series was considered. And Numerical simulation of the sediment by the Delft3d model at the Maengbang Beach was conducted to verify the validity of the method. NOAA wave data were collected for about 40 years from January 1979 to May 2019. Among them, waves, which are judged to have insignificant effect on the beach, were removed and the wave time series was reduced. To this end, the entire wave time series was graded at intervals of 0.5m, period 2sec, and wave direction 10° to generate a total of 749 representative waves, and a numerical simulation of sediment was performed for each representative wave for 1 day. When the maximum sediment height was less than 0.01m/day, it was assumed that the influence of the representative wave on the area was negligible. As a result of conducting numerical simulation of the sediment using the 23-month real-time waves and the wave by the reduced time series, the difference between the two simulation results indicates a local sedimentation difference of 0.1 to 0.5 m near Deokbongsan. There is a difference in sedimentation of 0.01 to 0.1m overall, and the pattern of repeated erosion and sedimentation along the entire coast is very similar to both real-time waves and reduced time series waves.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127596985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-30DOI: 10.20481/kscdp.2021.8.4.323
Jaeik Lee, Suchan Lee, Jong-min Jeong, Yongchim Min, Jin-Yong Jeong, Y. Kim
The importance of salinity has been highlighted to cope with climate changes and disaster prevention. The salinity of accuracy up to 0.005 is normally required in an open ocean to understand various oceanic and climatic phenomena; however, the reliability of salinity measured on the coast and open seas around Korea was low due to the lack of a standardized observation system and post-processing of quality verification. Korea Ocean Research Stations (KORS) has been producing salinity time series since 2003 through the Aanderaa conductivity-temperature (CT) 3919 inductive sensors, which have an advantage of on-site maintenance but tend to drift toward a lower conductivity because of biological attachments to the sensor. This study applied copper taping and UV light exposure techniques to the sensors and then compared its salinity measurements with RBR CTD mooring observations and SeaBird19 CTD profiles to assess a biofouling effect on salinity observations. This experiment shows that the salinity from the CT sensor without biofouling prevention starts to drift in a week, particularly for a surface sensor. This biofouling induced the decrease of salinity up to 10 in a month. The copper taping methodology efficiently suppressed the biological attachment but disturbed an electromagnetic field around the sensor, thus resulting in unrealistic salinity values. When UV light was periodically exposed at a distance of about 5 cm away from the CT sensor, relatively stable salinity could be observed without significant drift at least in two months. Besides, the SBE37 CTD, an electrode-type sensor, seems to be relatively free from biofouling but has difficulties in sensor maintenance and a sensor calibration process. Our results underline a double installation of salinity observation equipment with UV light exposure. In addition, the pre-calibration of a CT(D) sensor and post-verification should be included in a standard procedure for high-quality salinity measurement.
{"title":"Salinity drift prevention experiments in the Korea ocean research stations and suggestions for high quality salinity observation","authors":"Jaeik Lee, Suchan Lee, Jong-min Jeong, Yongchim Min, Jin-Yong Jeong, Y. Kim","doi":"10.20481/kscdp.2021.8.4.323","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.4.323","url":null,"abstract":"The importance of salinity has been highlighted to cope with climate changes and disaster prevention. The salinity of accuracy up to 0.005 is normally required in an open ocean to understand various oceanic and climatic phenomena; however, the reliability of salinity measured on the coast and open seas around Korea was low due to the lack of a standardized observation system and post-processing of quality verification. Korea Ocean Research Stations (KORS) has been producing salinity time series since 2003 through the Aanderaa conductivity-temperature (CT) 3919 inductive sensors, which have an advantage of on-site maintenance but tend to drift toward a lower conductivity because of biological attachments to the sensor. This study applied copper taping and UV light exposure techniques to the sensors and then compared its salinity measurements with RBR CTD mooring observations and SeaBird19 CTD profiles to assess a biofouling effect on salinity observations. This experiment shows that the salinity from the CT sensor without biofouling prevention starts to drift in a week, particularly for a surface sensor. This biofouling induced the decrease of salinity up to 10 in a month. The copper taping methodology efficiently suppressed the biological attachment but disturbed an electromagnetic field around the sensor, thus resulting in unrealistic salinity values. When UV light was periodically exposed at a distance of about 5 cm away from the CT sensor, relatively stable salinity could be observed without significant drift at least in two months. Besides, the SBE37 CTD, an electrode-type sensor, seems to be relatively free from biofouling but has difficulties in sensor maintenance and a sensor calibration process. Our results underline a double installation of salinity observation equipment with UV light exposure. In addition, the pre-calibration of a CT(D) sensor and post-verification should be included in a standard procedure for high-quality salinity measurement.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122577834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-30DOI: 10.20481/kscdp.2021.8.4.237
Y. Cho
Lately, many efforts have been made to address the problem concerned with deterministic design using reliability-based design, and the research results are significant. However, there is considerable confusion in the design practice regarding how to use failure probability, the main output of reliability-based design. In this rationale, this study aims to develop a robust hybrid deterministic design method for outer port facilities using the failure probability. To this end, we first reviewed the design process of Eulleungdo East Breakwater, some of which were recently damaged. It was revealed that the exceeding probability of design wave height of 5.2 m was merely 0.65, which corresponds to a return period of 1.53 years, showing that the outer port facilities of Ulleungdo were considerably underdesigned. In an effort to find an alternative that can overcome the limitations of the deterministic design method, which is highly likely to involve subjective judgment, a Level III reliability design was carried out. In doing so, tri-modal Gaussian wave slope distribution was used as a probabilistic model for wave slope. Numerical results show that failure probability was excessively estimated in the Gaussian distribution, and even if the TTP size was slightly reduced, the failure probability increased rapidly. Although failure probability is sensitive to the change in nominal diameter, there is a gradually increasing zone where the failure probability change rapidly decreases when the nominal diameter is larger than the critical value. The presence of a Gradually Increasing Zone mentioned above implies that it is uneconomical and has no physical background to adjust the nominal diameter to be larger than the critical value. Therefore, it can be easily conceived that outer port facility design should be performed using a failure probability provided by Level III reliability-based design.
{"title":"Proposal on Hybrid Design Method of Outer Port Facilities Using Failure Probability","authors":"Y. Cho","doi":"10.20481/kscdp.2021.8.4.237","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.4.237","url":null,"abstract":"Lately, many efforts have been made to address the problem concerned with deterministic design using reliability-based design, and the research results are significant. However, there is considerable confusion in the design practice regarding how to use failure probability, the main output of reliability-based design. In this rationale, this study aims to develop a robust hybrid deterministic design method for outer port facilities using the failure probability. To this end, we first reviewed the design process of Eulleungdo East Breakwater, some of which were recently damaged. It was revealed that the exceeding probability of design wave height of 5.2 m was merely 0.65, which corresponds to a return period of 1.53 years, showing that the outer port facilities of Ulleungdo were considerably underdesigned. In an effort to find an alternative that can overcome the limitations of the deterministic design method, which is highly likely to involve subjective judgment, a Level III reliability design was carried out. In doing so, tri-modal Gaussian wave slope distribution was used as a probabilistic model for wave slope. Numerical results show that failure probability was excessively estimated in the Gaussian distribution, and even if the TTP size was slightly reduced, the failure probability increased rapidly. Although failure probability is sensitive to the change in nominal diameter, there is a gradually increasing zone where the failure probability change rapidly decreases when the nominal diameter is larger than the critical value. The presence of a Gradually Increasing Zone mentioned above implies that it is uneconomical and has no physical background to adjust the nominal diameter to be larger than the critical value. Therefore, it can be easily conceived that outer port facility design should be performed using a failure probability provided by Level III reliability-based design.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126969648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-30DOI: 10.20481/kscdp.2021.8.4.297
Eun-ji Kang, Hyeong-Tak Lee, Ik-Soon Cho
The berthing velocity is the factor that has the greatest influence on the berthing energy. For the vessel to berth safely, it should not exceed the appropriate berthing velocity. In addition, when the vessel is berthing, it should be berthed with berthing energy smaller than the energy absorption of the fender. This study intends to derive the allowable berthing velocity by ship size considering the berthing capacity. When a small vessel berth, the allowable berthing velocity is greater than when a relatively large vessel berths. In this study, the extrapolated velocity is defined as the relative value of the ship’s berthing velocity when considering the ship's size and the berthing capacity. A regression equation for the allowable berthing velocity by ship size was derived by calculating the designed berthing energy for each fender performance. It was also verified whether any ships were exceeding the allowable berthing velocity by comparing it with the measured data for each jetty. In addition, the extrapolated velocity was proposed using the regression equation, and as a result of applying the measured data, 11 ships exceeded the designed velocity in jetty 1, but it was confirmed that all ships were safely berthed in jetty 2,3. Therefore, the target pier of this study was evaluated as a pier where ships can be berthed safely. A safer berthing velocity operation guideline can be suggested if the allowable berthing velocity by ship size is analyzed and utilized at various piers. Extrapolated velocity can also be used for risk analysis of berthing.
{"title":"Analysis of Allowable Berthing Velocity by Ship Size considering Designed Energy","authors":"Eun-ji Kang, Hyeong-Tak Lee, Ik-Soon Cho","doi":"10.20481/kscdp.2021.8.4.297","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.4.297","url":null,"abstract":"The berthing velocity is the factor that has the greatest influence on the berthing energy. For the vessel to berth safely, it should not exceed the appropriate berthing velocity. In addition, when the vessel is berthing, it should be berthed with berthing energy smaller than the energy absorption of the fender. This study intends to derive the allowable berthing velocity by ship size considering the berthing capacity. When a small vessel berth, the allowable berthing velocity is greater than when a relatively large vessel berths. In this study, the extrapolated velocity is defined as the relative value of the ship’s berthing velocity when considering the ship's size and the berthing capacity. A regression equation for the allowable berthing velocity by ship size was derived by calculating the designed berthing energy for each fender performance. It was also verified whether any ships were exceeding the allowable berthing velocity by comparing it with the measured data for each jetty. In addition, the extrapolated velocity was proposed using the regression equation, and as a result of applying the measured data, 11 ships exceeded the designed velocity in jetty 1, but it was confirmed that all ships were safely berthed in jetty 2,3. Therefore, the target pier of this study was evaluated as a pier where ships can be berthed safely. A safer berthing velocity operation guideline can be suggested if the allowable berthing velocity by ship size is analyzed and utilized at various piers. Extrapolated velocity can also be used for risk analysis of berthing.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126372110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-30DOI: 10.20481/kscdp.2021.8.4.221
Ju-Han Park, Ho-Kun Jeon, Chan-Su Yang
Illegal fishing has been a serious threat to the conservation of seafood resources and provoked the importance of marine surveillance. There are several types of fishing vessel monitoring systems operated by Republic of Korea, for example, Vessel Monitoring System(VMS), Automatic Identification System (AIS), V-Pass and VHF-DSC. However, those methods are not adaptable directly to fishing activity monitoring. The limitation requires more human resources to determine fishing status. Thus, this study proposes a method of estimating fishing activity from V-Pass, fishing vessel position reporting system, using Hidden Markov Model (HMM). HMM is a model to determine status through probability distribution for a sequence of time-series data. First of all, fishing activity status was labeled on V-Pass data. The distribution of speed on fishing activity was computed from the labeled data and HMM was constructed from the data obtained at Socheongcho Ocean Research Station (SORS). The model was first applied to the data of SORS for a test, and then Busan for validation. The model showed 99.4% and 89.6% as test and validation accuracy, respectively. It is concluded that the HMM can be applicable to predict a fishing activity from vessel tracks.
{"title":"Hidden Markov Model(HMM)-Based Fishing Activity Prediction Using V-Pass Data","authors":"Ju-Han Park, Ho-Kun Jeon, Chan-Su Yang","doi":"10.20481/kscdp.2021.8.4.221","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.4.221","url":null,"abstract":"Illegal fishing has been a serious threat to the conservation of seafood resources and provoked the importance of marine surveillance. There are several types of fishing vessel monitoring systems operated by Republic of Korea, for example, Vessel Monitoring System(VMS), Automatic Identification System (AIS), V-Pass and VHF-DSC. However, those methods are not adaptable directly to fishing activity monitoring. The limitation requires more human resources to determine fishing status. Thus, this study proposes a method of estimating fishing activity from V-Pass, fishing vessel position reporting system, using Hidden Markov Model (HMM). HMM is a model to determine status through probability distribution for a sequence of time-series data. First of all, fishing activity status was labeled on V-Pass data. The distribution of speed on fishing activity was computed from the labeled data and HMM was constructed from the data obtained at Socheongcho Ocean Research Station (SORS). The model was first applied to the data of SORS for a test, and then Busan for validation. The model showed 99.4% and 89.6% as test and validation accuracy, respectively. It is concluded that the HMM can be applicable to predict a fishing activity from vessel tracks.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129655964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-30DOI: 10.20481/kscdp.2021.8.4.255
Soon-mi Hwang, Hyung-Min Oh, Soo-Yong Nam, T. Kang
In the vicinity of the coast, there is a risk of complex disasters in which inland flooding, wave overtopping, storm surge, and tsunami occur simultaneously. In order to prepare for such complex disasters, it is necessary to set priorities for disaster preparedness through risk assessment and establish countermeasures. In this study, risk assessment is carried out targeting on Marine city, Centum city, and Millak waterside parks in Busan, where complex disasters have occurred or are likely to occur. For risk assessment, inundation prediction map constructed by the Ministry of Public Administration and Security in consideration of sea level rise, rainfall and storm surge scenarios and authorized data on social and economic risk factors were collected. The socioeconomic risk factors selected are population, basements, buildings, sidewalks, and roads, and the risk criteria for damage targets are set for each risk factors. And it was assessed considering the maximum inundation depth and maximum flow velocity of the inundation prediction map. Weights for each factor were derived through expert questionnaires. The risk assessment index that was finally evaluated by calculating the risk index for each element and applying weights was expressed as a risk map by different colors into four levels of attention, caution, alert and danger.
{"title":"A study on risk assessment of complex disasters in Busan coast","authors":"Soon-mi Hwang, Hyung-Min Oh, Soo-Yong Nam, T. Kang","doi":"10.20481/kscdp.2021.8.4.255","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.4.255","url":null,"abstract":"In the vicinity of the coast, there is a risk of complex disasters in which inland flooding, wave overtopping, storm surge, and tsunami occur simultaneously. In order to prepare for such complex disasters, it is necessary to set priorities for disaster preparedness through risk assessment and establish countermeasures. In this study, risk assessment is carried out targeting on Marine city, Centum city, and Millak waterside parks in Busan, where complex disasters have occurred or are likely to occur. For risk assessment, inundation prediction map constructed by the Ministry of Public Administration and Security in consideration of sea level rise, rainfall and storm surge scenarios and authorized data on social and economic risk factors were collected. The socioeconomic risk factors selected are population, basements, buildings, sidewalks, and roads, and the risk criteria for damage targets are set for each risk factors. And it was assessed considering the maximum inundation depth and maximum flow velocity of the inundation prediction map. Weights for each factor were derived through expert questionnaires. The risk assessment index that was finally evaluated by calculating the risk index for each element and applying weights was expressed as a risk map by different colors into four levels of attention, caution, alert and danger.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129059104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-30DOI: 10.20481/kscdp.2021.8.3.151
Y. Cho
Among the many scouring-protection works near a rubble mound breakwater, stacking armoring rocks in multiple or single layers are most popular. The rationale of these scouring-protection works is based on the Equilibrium regime or the maximum scouring depth. However, considering natural beaches, which constantly change their shape according to sea waves conditions, the equilibrium regime or the maximum scouring depth mentioned above seems to foot on the fragile physical background. In this study, in order to test the above hypothesis, numerical simulations were carried out on the partial reflection from the slopes of rubble mound breakwater, and its ensuing standing waves formed in the front seas of a breakwater, the change in the bed profiles due to the formation of standing waves, and scouring depth at the base of a rubble mound breakwater. In doing so, numerical simulations were implemented using OlaFoam, an OpenFoam-based toolbox, and SeoulFoam (Cho, 2020), a physics-based morphology model. Numerical results show that the wave length of sand waves is closely linked with the incoming wave period, while amplitudes of sand waves are determined by incoming wave height. Moreover, the seabed profiles underwent significant changes due to the presence of a rubble mound breakwater. It was shown that the size of sand waves increased when compared before the installation, and the shape of sand waves is getting skewed toward the shore direction. It was also shown that as exposure time to standing waves increased, the amplitude of sand waves also increased, and the scouring depth near the base of a breakwater increased. These results are contrary to the Equilibrium regime, and the scouring prevention works based on the stacking of armoring rocks should be re-evaluated.
{"title":"Numerical Analysis of Modified Bed-profiles due to the Presence of a Rubble Mound Breakwater using Physics-Based Morphology Model[SeoulFoam]","authors":"Y. Cho","doi":"10.20481/kscdp.2021.8.3.151","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.3.151","url":null,"abstract":"Among the many scouring-protection works near a rubble mound breakwater, stacking armoring rocks in multiple or single layers are most popular. The rationale of these scouring-protection works is based on the Equilibrium regime or the maximum scouring depth. However, considering natural beaches, which constantly change their shape according to sea waves conditions, the equilibrium regime or the maximum scouring depth mentioned above seems to foot on the fragile physical background. In this study, in order to test the above hypothesis, numerical simulations were carried out on the partial reflection from the slopes of rubble mound breakwater, and its ensuing standing waves formed in the front seas of a breakwater, the change in the bed profiles due to the formation of standing waves, and scouring depth at the base of a rubble mound breakwater. In doing so, numerical simulations were implemented using OlaFoam, an OpenFoam-based toolbox, and SeoulFoam (Cho, 2020), a physics-based morphology model. Numerical results show that the wave length of sand waves is closely linked with the incoming wave period, while amplitudes of sand waves are determined by incoming wave height. Moreover, the seabed profiles underwent significant changes due to the presence of a rubble mound breakwater. It was shown that the size of sand waves increased when compared before the installation, and the shape of sand waves is getting skewed toward the shore direction. It was also shown that as exposure time to standing waves increased, the amplitude of sand waves also increased, and the scouring depth near the base of a breakwater increased. These results are contrary to the Equilibrium regime, and the scouring prevention works based on the stacking of armoring rocks should be re-evaluated.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128646384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-30DOI: 10.20481/kscdp.2021.8.3.181
Y. Cho
Curved slit caisson has been the preferred structural type of breakwater in South Korea, and effective control of stem waves is a crucial design factor significantly affecting the performance of a curved slit caisson breakwater. Most of the past studies on stem waves heavily relied on wave drivers like the cubic Schrödinger Eq. due to the intrinsic difficulties in analyzing stem waves. However, considering the perturbation method evoked in the derivation of cubic Schrödinger Eq., the wave driver mentioned above could give erroneous results in the rough sea due to the higher-order waves that appeared in the wave field by resonance wave-wave interaction. In this rationale, in this study, the numerical simulation was implemented to verify the stem wave control effect of curved slit caisson using the ihFoam, toolbox having its roots on OpenFoam. It was shown that curved slit caisson breakwater effectively alleviates the scope and height of stem waves.
{"title":"Numerical Analysis of Stem Wave Control Effect of a Curved Slit Caisson Breakwater","authors":"Y. Cho","doi":"10.20481/kscdp.2021.8.3.181","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.3.181","url":null,"abstract":"Curved slit caisson has been the preferred structural type of breakwater in South Korea, and effective control of stem waves is a crucial design factor significantly affecting the performance of a curved slit caisson breakwater. Most of the past studies on stem waves heavily relied on wave drivers like the cubic Schrödinger Eq. due to the intrinsic difficulties in analyzing stem waves. However, considering the perturbation method evoked in the derivation of cubic Schrödinger Eq., the wave driver mentioned above could give erroneous results in the rough sea due to the higher-order waves that appeared in the wave field by resonance wave-wave interaction. In this rationale, in this study, the numerical simulation was implemented to verify the stem wave control effect of curved slit caisson using the ihFoam, toolbox having its roots on OpenFoam. It was shown that curved slit caisson breakwater effectively alleviates the scope and height of stem waves.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123583137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-30DOI: 10.20481/kscdp.2021.8.3.141
Yeon-Joong Kim, Jong-sung Yoon, M. Hasegawa, Jae-Hoon Jeong
The swash zone is an area that causes a change in the shape of a beach by generating sediment transport under the influence of intermittent waves, where wave run-up and run-down are infinitely repeated in the final stage of the shoaling process. However, the ability to predict the sediment transport is extremely poor despite the swash zone being an extremely important area in terms of offshore disaster prevention. In particular, many researchers are conducting studies on the development of various types of observation equipment and analysis techniques because the turbulent flow of active fluid dominates the sediment transport and is an extremely important parameter for the analysis of the transport mechanism. However, in flow velocity measurement, it is difficult to measure a quantitative representative flow velocity over time because the swash zone has a shallow water depth and an active turbulent flow. Expensive equipment and short-time measurement are also limitations. Therefore, the purpose of this study was to evaluate the applicability of nonintrusive space-time image velocimetry(STIV) to analyze the flow characteristics of fluid in the swash zone, such as the movement velocity and period of intermittent waves in the shoaling process. The prediction accuracy was improved by removing various noises included in the images with the introduction of artificial intelligence for immediate and accurate calculation of the representative flow velocity using images that can be obtained easily. Consequently, it was discovered that the spatial representative flow velocity occurring in the swash zone, change in the wave period according to the shoaling effect, rip current and surface velocity can be measured.
{"title":"Evaluation of the Applicability of STIV to Wave Characteristic Measurement in the Swash Zone","authors":"Yeon-Joong Kim, Jong-sung Yoon, M. Hasegawa, Jae-Hoon Jeong","doi":"10.20481/kscdp.2021.8.3.141","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.3.141","url":null,"abstract":"The swash zone is an area that causes a change in the shape of a beach by generating sediment transport under the influence of intermittent waves, where wave run-up and run-down are infinitely repeated in the final stage of the shoaling process. However, the ability to predict the sediment transport is extremely poor despite the swash zone being an extremely important area in terms of offshore disaster prevention. In particular, many researchers are conducting studies on the development of various types of observation equipment and analysis techniques because the turbulent flow of active fluid dominates the sediment transport and is an extremely important parameter for the analysis of the transport mechanism. However, in flow velocity measurement, it is difficult to measure a quantitative representative flow velocity over time because the swash zone has a shallow water depth and an active turbulent flow. Expensive equipment and short-time measurement are also limitations. Therefore, the purpose of this study was to evaluate the applicability of nonintrusive space-time image velocimetry(STIV) to analyze the flow characteristics of fluid in the swash zone, such as the movement velocity and period of intermittent waves in the shoaling process. The prediction accuracy was improved by removing various noises included in the images with the introduction of artificial intelligence for immediate and accurate calculation of the representative flow velocity using images that can be obtained easily. Consequently, it was discovered that the spatial representative flow velocity occurring in the swash zone, change in the wave period according to the shoaling effect, rip current and surface velocity can be measured.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116532193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-30DOI: 10.20481/kscdp.2021.8.3.127
Insik Chun, In-ki Min, Yongchim Min, Byungcheol Oh, J. Shim
The prediction of the performance of a wave observation buoy is very important to acquire both in-situ security and good observation quality. In the present study, a numerical method was set up to analyze the dynamic interaction of a spherical buoy with its single point mooring line subject to regular wave conditions. The method was applied to the condition of an existing hydraulic experiment, producing results that are well compatible with experimental results within the limited accuracy of the available data. It was argued that some discrepancies between the numerical and experimental results might be due to the uncertainties of the wave exciting forces acting on the buoy and the experimental conditions of mooring line. The method was finally applied to demonstrate two practical issues related to in-situ wave height measurements; the effect of buoy size on resulting heave motion and the aspect of the numerical integration of heave acceleration to get wave profile.
{"title":"Numerical Analysis for Predicting the Performance of Wave Observation Buoy: Dynamic Analysis under Regular Wave","authors":"Insik Chun, In-ki Min, Yongchim Min, Byungcheol Oh, J. Shim","doi":"10.20481/kscdp.2021.8.3.127","DOIUrl":"https://doi.org/10.20481/kscdp.2021.8.3.127","url":null,"abstract":"The prediction of the performance of a wave observation buoy is very important to acquire both in-situ security and good observation quality. In the present study, a numerical method was set up to analyze the dynamic interaction of a spherical buoy with its single point mooring line subject to regular wave conditions. The method was applied to the condition of an existing hydraulic experiment, producing results that are well compatible with experimental results within the limited accuracy of the available data. It was argued that some discrepancies between the numerical and experimental results might be due to the uncertainties of the wave exciting forces acting on the buoy and the experimental conditions of mooring line. The method was finally applied to demonstrate two practical issues related to in-situ wave height measurements; the effect of buoy size on resulting heave motion and the aspect of the numerical integration of heave acceleration to get wave profile.","PeriodicalId":326564,"journal":{"name":"Korea Society of Coastal Disaster Prevention","volume":"172 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123018908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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