Complex flow around floating structures is a highly nonlinear problem,and it is a typical feature in ship and ocean engineering.Traditional experimental methods and potential flow theory have limitations in predicting...Complex flow around floating structures is a highly nonlinear problem,and it is a typical feature in ship and ocean engineering.Traditional experimental methods and potential flow theory have limitations in predicting complex viscous flows.With the improvement of high-performance computing and the development of numerical techniques,computational fluid dynamics(CFD)has become increasingly powerful in predicting the complex viscous flow around floating structures.This paper reviews the recent progress in CFD techniques for numerical solutions of typical complex viscous flows in ship and ocean engineering.Applications to free-surface flows,breaking bow waves of high-speed ship,ship hull-propeller-rudder interaction,vortexinduced vibration of risers,vortex-induced motions of deep-draft platforms,and floating offshore wind turbines are discussed.Typical techniques,including volume of fluid for sharp interface,dynamic overset grid,detached eddy simulation,and fluid-structure coupling,are reviewed along with their applications.Some novel techniques,such as high-efficiency Cartesian grid method and GPU acceleration technique,are discussed in the last part as the future perspective for further enhancement of accuracy and efficiency for CFD simulations of complex flow in ship and ocean engineering.展开更多
Sea cucumber Apostichopus japonicus is an ideal model organism for marine invertebrate aestivation;it annually enters a“sleeping state”for nearly 3 months when ambient water temperature range is 25–30℃.The natural...Sea cucumber Apostichopus japonicus is an ideal model organism for marine invertebrate aestivation;it annually enters a“sleeping state”for nearly 3 months when ambient water temperature range is 25–30℃.The natural fasting is accompanied by remodeling the intestinal biota and function,which is a part of host biology and could affect the gut microbiota.We investigatesd the impact of annual aestivation on gut microbiota using high-throughput sequencing of 16S rRNA amplicons.Results reveal a notable alteration in the composition of gut bacteria during aestivation during which various indigenous families and genera that exhibit a preference for dietary glycans(e.g.,family Rhodobacteraceae and Flavobacteriaceae)decreased,while the taxa capable of utilizing substrates derived from the host(e.g.,genus Akkermansia and Prevotella)increased,and so did certain opportunistic pathogenic bacteria.Moreover,the investigation delved into the gut morphology and immunity response of A.japonicus and reveal that the intestine of A.japonicus undergoes substantial atrophy and degeneration during aestivation.However,there was an observed augmentation in the levels of acid and neutral mucin within mucous cells,as well as an enhanced immune defense response(as evidenced by increased gene expression of AjTLR3,LITAF,Ajp105,and LYZ).These results imply that the composition of sea cucumber gut microbiota differed between aestivation and active periods,which potentially affects the intestinal functions of the host and the symbiotic relationship between host and its microbiota over the activeaestivation cycle.展开更多
基金supported by the National Natural Science Foundation of China(51809169,51879159)Chang Jiang Scholars Program(T2014099)+2 种基金Shanghai Excellent Academic Leaders Program(17XD1402300)Innovative Special Project of Numerical Tank of Ministry of Industry and Information Technology of China(2016-23/09)National Key Research and Development Program of China(2019YFB1704203,2019YFC0312400).
文摘Complex flow around floating structures is a highly nonlinear problem,and it is a typical feature in ship and ocean engineering.Traditional experimental methods and potential flow theory have limitations in predicting complex viscous flows.With the improvement of high-performance computing and the development of numerical techniques,computational fluid dynamics(CFD)has become increasingly powerful in predicting the complex viscous flow around floating structures.This paper reviews the recent progress in CFD techniques for numerical solutions of typical complex viscous flows in ship and ocean engineering.Applications to free-surface flows,breaking bow waves of high-speed ship,ship hull-propeller-rudder interaction,vortexinduced vibration of risers,vortex-induced motions of deep-draft platforms,and floating offshore wind turbines are discussed.Typical techniques,including volume of fluid for sharp interface,dynamic overset grid,detached eddy simulation,and fluid-structure coupling,are reviewed along with their applications.Some novel techniques,such as high-efficiency Cartesian grid method and GPU acceleration technique,are discussed in the last part as the future perspective for further enhancement of accuracy and efficiency for CFD simulations of complex flow in ship and ocean engineering.
基金Supported by the National Natural Science Foundation of China(No.41906098)the NSFC-Shandong Joint Fund(No.U2106208)the Development Plan of Youth Innovation Team in Colleges and Universities of Shandong Province(No.2022KJ269)。
文摘Sea cucumber Apostichopus japonicus is an ideal model organism for marine invertebrate aestivation;it annually enters a“sleeping state”for nearly 3 months when ambient water temperature range is 25–30℃.The natural fasting is accompanied by remodeling the intestinal biota and function,which is a part of host biology and could affect the gut microbiota.We investigatesd the impact of annual aestivation on gut microbiota using high-throughput sequencing of 16S rRNA amplicons.Results reveal a notable alteration in the composition of gut bacteria during aestivation during which various indigenous families and genera that exhibit a preference for dietary glycans(e.g.,family Rhodobacteraceae and Flavobacteriaceae)decreased,while the taxa capable of utilizing substrates derived from the host(e.g.,genus Akkermansia and Prevotella)increased,and so did certain opportunistic pathogenic bacteria.Moreover,the investigation delved into the gut morphology and immunity response of A.japonicus and reveal that the intestine of A.japonicus undergoes substantial atrophy and degeneration during aestivation.However,there was an observed augmentation in the levels of acid and neutral mucin within mucous cells,as well as an enhanced immune defense response(as evidenced by increased gene expression of AjTLR3,LITAF,Ajp105,and LYZ).These results imply that the composition of sea cucumber gut microbiota differed between aestivation and active periods,which potentially affects the intestinal functions of the host and the symbiotic relationship between host and its microbiota over the activeaestivation cycle.
文摘红藻真江蓠(Gracilaria vermiculophylla)是西北太平洋地区特有种,但在过去100年间它借助海运(太平洋牡蛎养殖)快速入侵到北美、欧洲和地中海等沿海栖息地,对当地的生物多样性、海洋环境和生态系统等造成重大影响。为从分子水平初步了解真江蓠成功入侵的潜在机制,文章对其入侵起源地——日本北部的真江蓠及非入侵种——绳状龙须菜(Gracilariopsis chorda)进行了同质园实验(common garden experiment)处理后的比较转录组研究,以探究该地区入侵属性不同的两种红藻间的基因表达差异。结果表明,真江蓠和绳状龙须菜共有基因序列集(Universal Gene,unigene)主要集中在核糖体、嘌呤和嘧啶代谢等通路。其中,在真江蓠中光系统II反应中心蛋白D1(photosystem II reaction center protein D1)、细胞色素P450单加氧酶(cytochrome P450 monooxygenase)和核酮糖1,5二磷酸羧化酶大亚基(Ribulose bisphosphate carboxylase large subunit,rbcL)等基因的表达量显著上调,而逆转录转座子蛋白(retrotransposon protein)、细胞壁相关的水解酶(cell wall-associated hydrolase)和金属离子转运蛋白Nramp5的表达既上调也下调。与光合作用过程相关基因的大量表达可能有助于真江蓠应对逆境胁迫,特别是光系统ⅡD1反应中心蛋白表达量升高可能有助于藻体修复光系统Ⅱ复合体,从而制造更多的有机物以备藻体生长所需。而金属离子转运蛋白Nramp5等的上调和下调则表明江蓠等红藻可能通过某些基因表达量的增减对不同的环境变动作出响应。总体而言,代谢过程中的资源再分配很可能是驱动真江蓠适应和耐受新的生境的主要分子机制。
