摘要：
The impact of the South China Sea (SCS) to the super typhoon Mangkhut (2018) and the air-sea interaction are evaluated through COAWST model in this study which fully coupled with the atmosphere model (WRF), the ocean model (ROMS), and the wave model (SWAN). A comparison of our modeled results with several buoys and tide stations revealed remarkable consistency, the minimum root mean square error (RMSE) for wind speed, significant wave height, and water level are 3.013 m/s, 0.641m, 0.007m. During the development and dissipation of super typhoon Mangkhut, the Coriolis force caused the typhoon wind field to exhibit a pronounced rightward deflection. The characteristics of the significant wave height field are generally similar to those of the wind field, although there is a temporal lag of several hours. Moreover, we researched on the spatiotemporal variations of sea surface temperature (SST) impact by the Mangkhut’s passage, and found that it exhibits two main characteristics: spatial asymmetry and temporal lag. The spatial asymmetry is primarily governed by typhoon-generated wind fields, while the temporal lag is mainly controlled by upwelling and vertical mixing processes during the typhoon’s passage, with Ekman pumping playing a pivotal role in these dynamics. This study mainly concentrates on investigating the dynamic and thermodynamic responses of the ocean during extreme weather conditions by using COAWST model.
摘要：
There has been significant interest in post-tsunami surveys regarding how effective fringing reefs are at protecting coastlines from inundation caused by tsunamis. Limited attention has been given to the wave transformation characteristics and wave run-up dynamics within a complex reef-lagoon-channel system compared to the extensively studied two-dimensional horizontal fringing reefs. In response to this research gap, a three-dimensional numerical wave tank has been created, incorporating the incompressible Reynolds-averaged Navier-Stokes equations accompanied with k-ω SST turbulence model. The volume of fluid (VOF) strategy is employed to track the free surface, accompanied by advanced grid cascading encryption technology. Laboratory measurements (Swigler, 2009; Briggs et al., 1995) of the waves are utilized for model validation. The influence of incident wave height, reef flat submergence, fore-reef slope, and channel width on wave propagation characteristics were examined. The results reveal that the relative run-up decreases with larger wave heights and decreases near channels as reef flat submergences rise. Initially, smaller channels reduce relative run-up, but it increases again with widening, shifting the maximum relative run-up location away from the channel, while fore-reef slope changes minimally affect run-up.
There has been significant interest in post-tsunami surveys regarding how effective fringing reefs are at protecting coastlines from inundation caused by tsunamis. Limited attention has been given to the wave transformation characteristics and wave run-up dynamics within a complex reef-lagoon-channel system compared to the extensively studied two-dimensional horizontal fringing reefs. In response to this research gap, a three-dimensional numerical wave tank has been created, incorporating the incompressible Reynolds-averaged Navier-Stokes equations accompanied with k-ω SST turbulence model. The volume of fluid (VOF) strategy is employed to track the free surface, accompanied by advanced grid cascading encryption technology. Laboratory measurements (Swigler, 2009; Briggs et al., 1995) of the waves are utilized for model validation. The influence of incident wave height, reef flat submergence, fore-reef slope, and channel width on wave propagation characteristics were examined. The results reveal that the relative run-up decreases with larger wave heights and decreases near channels as reef flat submergences rise. Initially, smaller channels reduce relative run-up, but it increases again with widening, shifting the maximum relative run-up location away from the channel, while fore-reef slope changes minimally affect run-up.
摘要：
Repeatedly solving flow around structures with varying parameters using computational fluid dynamics (CFD) is often essential for structural design. This study proposes a boundary-assimilation Fourier neural operator (BAFNO) method to address the challenges of manually setting initial conditions for CFD. The focus of the BAFNO is on the generalization ability to predict initial flow fields without relying on observational data. BAFNO addresses the boundary constraint requirements of the existing physics-informed neural operator models in parametric geometries. Inspired by the ghost node method, the domain boundary conditions are assimilated into the loss function instead of adding penalty terms. Meanwhile, the structure boundaries are assimilated into a damping source term using a level set function. BAFNO can flexibly handle parametric geometries with different shapes and quantities. Subsequently, a series of numerical experiments for flow-around structures are conducted to confirm the performance of the BAFNO. The results indicate that the BAFNO has strong generalization capability, and the BAFNO + CFD can obtain dynamic stable fields faster than the direct CFD.
摘要：
Floods are one of the most destructive disasters and require a range of structural and non-structural measures to reduce their impacts. Evacuation is an effective non-structural measure to increase the resilience of flood-affected areas. This study aims to provide a systematic overview of evacuation planning for urban flood scenarios in terms of theories, methods, models, and techniques for both pedestrians and vehicles. The review addresses key components such as flood simulation modelling, flood hazard assessment methods, shelter identification, evacuation route development, and evacuee movement modelling. Among these, we highlight the comparison and analysis of flood hazard assessment methods, shelter optimisation and route optimisation. Additionally, a systematic analysis and comparison of evacuation shelters, evacuation route algorithms, and evacuee movement models are presented. Meta-heuristic algorithms have been shown to perform well for evacuation routes. Finally, the insights into four recent directions for enhancing evacuation plans include consideration of pedestrian and vehicle movement speeds, evacuee psychology, multimodal emergency evacuation, and the effect of overhead power lines on rescue operations.
Floods are one of the most destructive disasters and require a range of structural and non-structural measures to reduce their impacts. Evacuation is an effective non-structural measure to increase the resilience of flood-affected areas. This study aims to provide a systematic overview of evacuation planning for urban flood scenarios in terms of theories, methods, models, and techniques for both pedestrians and vehicles. The review addresses key components such as flood simulation modelling, flood hazard assessment methods, shelter identification, evacuation route development, and evacuee movement modelling. Among these, we highlight the comparison and analysis of flood hazard assessment methods, shelter optimisation and route optimisation. Additionally, a systematic analysis and comparison of evacuation shelters, evacuation route algorithms, and evacuee movement models are presented. Meta-heuristic algorithms have been shown to perform well for evacuation routes. Finally, the insights into four recent directions for enhancing evacuation plans include consideration of pedestrian and vehicle movement speeds, evacuee psychology, multimodal emergency evacuation, and the effect of overhead power lines on rescue operations.
摘要：
洞庭湖水体面积动态变化监测对防洪、维系生态系统的稳定及生物多样性具有重要意义。以经典Unet网络模型和创新性HRNet网络模型为代表的深度学习技术已成为遥感图像信息获取的高效途径，实验以Sentinel-1A SAR影像为主要数据源，定性、定量地分析了Sentinel-1双极化水体指数法（Sentinel-1 Dual-Polarized Water Index，SDWI）、面向对象分类法、UNet网络模型和HRNet网络模型4种方法的水体提取效果，并基于最佳水体提取方法对洞庭湖2016~2021年汛期（4~10月）水体面积进行时空变化特征分析。结果表明：①HRNet和Unet网络模型较传统方法具有更优的水体提取效果，其中，HRNet网络模型在抑噪、抗阴影等方面表现更佳，F1分数、误判率和平均交并比分别为0.961 6、0.007 8和0.958 6；②汛期洞庭湖水体面积在月际变化上呈现出“涨—丰—退”的变化特征，湖面从4~5月份开始扩张，6~8月份水域面积维持在较高水平，此后由于来水减少，9~10月的水体面积逐步减小。研究期间所监测到的最大水体面积为2020年7月30日的2 263.90 km 2 ；③洞庭湖汛期的水体淹没频率从湖体中心和干流向外逐渐降低，不同湖区的淹没频率分布格局不同，东洞庭湖 “湖心高四周低”，南洞庭湖和西洞庭湖“南高北低”。综上所述，Sentinel-1A SAR影像与深度学习技术的结合应用可以实现洞庭湖水体信息高效获取与水面面积高频监测，为高动态湖泊水域监测提供了一种新思路。 您的浏览器不支持 audio 元素。 AI语音播报 Monitoring the dynamic changes of water area in Dongting Lake is of great significance for flood control， ecosystem stability and biodiversity. The deep learning algorithm represented by the classic Unet the innovative HRNet has become an efficient way to obtain remote sensing image information. Taking Sentinel-1A SAR image as the main data source， this paper qualitatively and quantitatively analyzes the water extraction results of SDWI index method （Sentinel-1 Dual-Polarized Water Index，SDWI）， object-oriented classification method， UNet network model and HRNet network model. Based on the best water extraction method， the temporal and spatial variation characteristics of water area in the flood season （April to October） of Dongting Lake from 2016 to 2021 are analyzed. The results show that ： ① The deep learning algorithm represented by HRNet and Unet has better water extraction effect than traditional methods. Among them， HRNet has superior performance in noise suppression and shadow resistance， and the F1 score， MRate and MIoU are 0.961 6， 0.007 8 and 0.958 6， respectively. ② During the flood season， the water area of Dongting Lake shows the characteristics of “ increase-full-decrease ” in the monthly variation. The lake surface begins to expand from April to May， and the water area maintained at a high level from June to August. Since then， due to the decrease of inflow， the water area gradually decreases from September to October. The 2 263.90 km 2 at July 30， 2020 is the largest water area monitored during the study period. ③ The submerged frequency of water body in flood season of Dongting Lake gradually decreases from the center of the lake body and the main stream. The distribution patterns of submerged frequency in different lake areas are different. The submerged frequency of East Dongting Lake is higher than that of South Dongting Lake and West Dongting Lake. In summary， the combination of Sentinel-1A SAR image and deep learning technology can realize the efficient acquisition of water information and high-frequency monitoring of the water surface area at Dongting Lake， providing a new idea for the high dynamic lake water monitoring.
期刊：
Journal of Fluid Mechanics,2024年990:A15 ISSN：0022-1120
通讯作者：
He, F
作者机构：
[Yao, Zhen; Long, Yuannan; Bian, Cheng; Jiang, Changbo; Jiang, Chao; Wu, Zhiyuan; Deng, Bin; Chen, Jie] Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;[Long, Yuannan; Jiang, Changbo; Wu, Zhiyuan; Deng, Bin; Chen, Jie] Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.;[Long, Yuannan; Jiang, Changbo; Wu, Zhiyuan; Deng, Bin; Chen, Jie] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.;[He, Fei] Univ Western Australia, Sch Engn, 35 Stirling Highway, Crawley, WA 6009, Australia.
通讯机构：
[He, F ] U;Univ Western Australia, Sch Engn, 35 Stirling Highway, Crawley, WA 6009, Australia.
关键词：
sediment transport
摘要：
Understanding settling motion of coral grains is important in terms of protection of coral reef systems and resotoration of the associated ecosystems. In this paper, a series of laboratory experiments was conducted to investigate the settling motion, using optical microscopy to measure shape parameters of coral grains and the particle-filtering-based object tracking to reconstruct the three-dimensional trajectory. Three characteristic descent regimes, namely, tumbling, chaotic and fluttering, are classified based on the three-dimensional trajectory, the spiral radius variation and the velocity spectrum. It is demonstrated that if one randomly picks up one coral grain, then the probabilities of occurrence of the three regimes are approximately $26\,\%$ , $42\,\%$ and $32\,\%$ , respectively. We have shown that first, the dimensionless settling velocity generally increases with the non-dimensional diameter and Corey shape factor and second, the drag coefficient generally decreases with the Reynolds number and Corey shape factor. Based on this, the applicability of existing models on predicting settling velocity and drag coefficient for coral grains is demonstrated further. Finally, we have proposed extended models for predicting the settling velocity. This study contributes to better understanding of settling motion and improves our predictive capacity of settling velocity for coral grains with complex geometry.
通讯机构：
[Chen, J ] C;Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.;Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.
关键词：
reef islands;coral sand beach;equilibrium beach profile;coral sand bar
摘要：
This study utilized 50 laboratory experiments to document the evolution of coral beaches under varying regular wave conditions, including five distinct wave periods and ten wave heights. Both the type of equilibrium beach and the shape of sand bars were used to represent beach evolution. The evolution of coral sand beaches was then compared to quartz sand beaches. The experimental results show that the predicted (modeled) equilibrium profile of a quartz sand beach was not applicable to coral sand beaches. Compared to sand bars on quartz sand beaches, the distance from bar crests to the beach berm in coral sand beaches was greater, whereas the erosional depth of sand troughs was deeper. However, the grain size distribution of sand associated with the coral sand beach under wave action was consistent with Celikoglu’s law. Both an equilibrium beach profile classification model and a sand bar shape prediction model for coral sand beaches were developed based on the experimental data.
期刊：
Journal of Marine Science and Engineering,2024年12(5):820- ISSN：2077-1312
通讯作者：
Chen, J
作者机构：
[Yao, Zhen; Bian, Cheng; Jiang, Changbo; Wu, Zhiyuan; Chen, Jie; Liu, Jiaxiang] Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;[Jiang, Changbo; Wu, Zhiyuan; Chen, Jie] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.;[Jiang, Changbo; Wu, Zhiyuan; Chen, Jie] Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.
通讯机构：
[Chen, J ] C;Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Peoples R China.;Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.;Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.
关键词：
bivalve shells;gastropod shells;final orientation;incipient mean velocity;motion thresholds
摘要：
Understanding the motion thresholds of shells is important, as shell motion allows the analysis of beach profiles, prevents excessive erosion of the coastline, and helps to resource the use of discarded shells, providing new ideas for the protection of beaches. In this study, the orientational motions and motion thresholds of two types of typical molluscan shells, bivalve and gastropod shells, were investigated by means of flume experiments. The final orientations with the statistically highest number of occurrences during the orientational motions of each shell were used as the initial orientations for the respective threshold flow velocity measurements. The critical Shields parameter and the incipient mean velocity of the flow were used to represent the critical threshold of the motion. The critical Shields parameters for bivalve shells in the convex upward position were overall higher on average than those for gastropod shells. The experimental data showed that the incipient mean flow velocities of bivalve shells in the convex upward position were about 1.4–2.8 times larger than those in the convex downward position. The incipient mean velocity data were regressed to obtain the motion threshold equations applicable to bivalve shells in the convex upward and convex downward positions as well as gastropod shells under different final orientations.
摘要：
基于气液两相流模型建立二维数值风浪水槽，采用VOF（Volume of Fluid）模型捕捉自由液面，研究了风作用下规则波在岸礁地形上的水动力特性。将计算结果与实验数据对比，证明了该模型计算风作用下波浪传播的准确性，并进一步分析了不同风速对规则波在岸礁地形上水动力特性影响。结果表明：有风作用时，破碎区的波峰高于无风作用时，冲泻区的波峰低于无风作用时，在风速0～8 m/s范围内，风的作用不会改变波浪在岸礁地形上的破碎类型，但会导致波浪提前破碎并影响破碎波形态变化过程。风的作用会改变波浪在岸礁地形上传播时各断面水平时均流速沿水深分布结构，并且会导致水气交界面附近水质点的速度增大，影响范围随着风速的增大而增大。
