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.
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：
<jats:p>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.</jats:p>
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.
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。
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.
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 Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.;[Jiang, Changbo; Wu, Zhiyuan; Chen, Jie] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.
通讯机构：
[Jie Chen] S;School of Hydraulic and Environmental Engineering, Changsha University of Science & Technology, Changsha, 410114, China<&wdkj&>Key Laboratory of Dongting Lake Aquatic Eco-Environmental Control and Restoration of Hunan Province, Changsha, 410114, China<&wdkj&>Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province, Changsha, 410114, China
