In hot-dip galvanizing lines, undesirable vibration of the moving steel strip occurs due to the impingement of the high-speed turbulence jet, which leads to non-uniformity of zinc thickness, as well as splash of the l...In hot-dip galvanizing lines, undesirable vibration of the moving steel strip occurs due to the impingement of the high-speed turbulence jet, which leads to non-uniformity of zinc thickness, as well as splash of the liquid zinc. In this paper, the turbulent jet flow field is firstly numerically obtained using the CFD method. Then, the influence of the turbulent jet flow on the steel strip is simplified as a harmonic force at the impingement line, and the response of the steel strip is obtained by means of finite element analysis for different strip lengths, thickness and pretension forces. Influences of impingement distance, air knife slot gap and jet pressure, on vibration of the steel strip are also analyzed. The results will provide theoretical basis for the reduction of steel strip vibration in continuous hot-dip galvanizing process.展开更多
In this paper the database obtained from LES is used to examine the algebraicturbulence model in Demuren and Rodi’s work. The results show that the prediction ofnormal Reynolas stresses and turbulence energy by means...In this paper the database obtained from LES is used to examine the algebraicturbulence model in Demuren and Rodi’s work. The results show that the prediction ofnormal Reynolas stresses and turbulence energy by means of turbulence modeling isbetter than that of shear Reynolde stresses. The comparison shows the LES methodcan be used to examine turbulence modelling.展开更多
风电场空气动力场是以涡流形式产生和演变,采用能够提供涡流演变细节特征的大涡模拟(Large eddy simulation,LES)方法模拟典型山丘地形的涡流结构,通过风洞试验数据验证湍动能输运(Kinetic energy transport,KET)模型模拟结果的准确性,...风电场空气动力场是以涡流形式产生和演变,采用能够提供涡流演变细节特征的大涡模拟(Large eddy simulation,LES)方法模拟典型山丘地形的涡流结构,通过风洞试验数据验证湍动能输运(Kinetic energy transport,KET)模型模拟结果的准确性,并探讨不同入流风速对山丘地形风电场瞬时特性的影响。随后探索地形诱导涡与风力机尾涡耦合的时空演化机制,发现单台风力机与两台并列风力机工况的尾涡结构的耦合演变机理存在差异,单台风力机工况是由于二次涡的形成及其与尾涡的耦合作用,两台并列风力机则归因于二次涡与尾涡的耦合及两机组间涡流耦合的共同作用。针对复杂地形涡流演变的研究可以为风电场规划设计与运行提供参考。展开更多
Molecular identification methods,in particular high-throughput sequencing tools,have greatly improved our knowledge about fungal diversity and biogeography,but many of the recovered taxa from natural environments cann...Molecular identification methods,in particular high-throughput sequencing tools,have greatly improved our knowledge about fungal diversity and biogeography,but many of the recovered taxa from natural environments cannot be identified to species or even higher taxonomic levels.This study addresses the phylogenetic placement of previously unrecognized fungal groups by using two complementary approaches:(i)third-generation amplicon sequencing analysis of DNA from global soil samples,screening out ITS reads of<90%similarity to other available Sanger sequences,and(ii)analysis of common fungal taxa that were previously indicated to be enigmatic in terms of taxonomic placement based on the ITS sequences alone(so-called top50 sequences).For the global soil samples,we chose to amplify the full rRNA gene operon using four partly overlapping amplicons and multiple newly developed primers or primer combinations that cover nearly all fungi and a vast majority of non-fungal eukaryotes.We extracted the rRNA 18S(SSU)and 28S(LSU)genes and performed phylogenetic analyses against carefully selected reference material.Both SSU and LSU analyses placed most soil sequences and top50 sequences to known orders and classes,but tens of monophyletic groups and single sequences remained outside described taxa.Furthermore,the LSU analyses recovered a few small groups of sequences that may potentially represent novel phyla.We conclude that rRNA genes-based phylogenetic analyses are efficient tools for determining phylogenetic relationships of fungal taxa that cannot be placed to any order or class using ITS sequences alone.However,in many instances,longer rRNA gene sequences and availability of both SSU and LSU reads are needed to improve taxonomic resolution.By leveraging third-generation sequencing from global soil samples,we successfully provided phylogenetic placement for many previously unidentified sequences and broadened our view on the fungal tree of life,with 10-20%new order-level taxa.In addition,the PacBio sequence data greatly extends fungal class-level information in reference databases.展开更多
文摘In hot-dip galvanizing lines, undesirable vibration of the moving steel strip occurs due to the impingement of the high-speed turbulence jet, which leads to non-uniformity of zinc thickness, as well as splash of the liquid zinc. In this paper, the turbulent jet flow field is firstly numerically obtained using the CFD method. Then, the influence of the turbulent jet flow on the steel strip is simplified as a harmonic force at the impingement line, and the response of the steel strip is obtained by means of finite element analysis for different strip lengths, thickness and pretension forces. Influences of impingement distance, air knife slot gap and jet pressure, on vibration of the steel strip are also analyzed. The results will provide theoretical basis for the reduction of steel strip vibration in continuous hot-dip galvanizing process.
文摘In this paper the database obtained from LES is used to examine the algebraicturbulence model in Demuren and Rodi’s work. The results show that the prediction ofnormal Reynolas stresses and turbulence energy by means of turbulence modeling isbetter than that of shear Reynolde stresses. The comparison shows the LES methodcan be used to examine turbulence modelling.
文摘风电场空气动力场是以涡流形式产生和演变,采用能够提供涡流演变细节特征的大涡模拟(Large eddy simulation,LES)方法模拟典型山丘地形的涡流结构,通过风洞试验数据验证湍动能输运(Kinetic energy transport,KET)模型模拟结果的准确性,并探讨不同入流风速对山丘地形风电场瞬时特性的影响。随后探索地形诱导涡与风力机尾涡耦合的时空演化机制,发现单台风力机与两台并列风力机工况的尾涡结构的耦合演变机理存在差异,单台风力机工况是由于二次涡的形成及其与尾涡的耦合作用,两台并列风力机则归因于二次涡与尾涡的耦合及两机组间涡流耦合的共同作用。针对复杂地形涡流演变的研究可以为风电场规划设计与运行提供参考。
基金funded by the Estonian Science Foundation(Grants PUT1399,PRG632,MOBERC21)。
文摘Molecular identification methods,in particular high-throughput sequencing tools,have greatly improved our knowledge about fungal diversity and biogeography,but many of the recovered taxa from natural environments cannot be identified to species or even higher taxonomic levels.This study addresses the phylogenetic placement of previously unrecognized fungal groups by using two complementary approaches:(i)third-generation amplicon sequencing analysis of DNA from global soil samples,screening out ITS reads of<90%similarity to other available Sanger sequences,and(ii)analysis of common fungal taxa that were previously indicated to be enigmatic in terms of taxonomic placement based on the ITS sequences alone(so-called top50 sequences).For the global soil samples,we chose to amplify the full rRNA gene operon using four partly overlapping amplicons and multiple newly developed primers or primer combinations that cover nearly all fungi and a vast majority of non-fungal eukaryotes.We extracted the rRNA 18S(SSU)and 28S(LSU)genes and performed phylogenetic analyses against carefully selected reference material.Both SSU and LSU analyses placed most soil sequences and top50 sequences to known orders and classes,but tens of monophyletic groups and single sequences remained outside described taxa.Furthermore,the LSU analyses recovered a few small groups of sequences that may potentially represent novel phyla.We conclude that rRNA genes-based phylogenetic analyses are efficient tools for determining phylogenetic relationships of fungal taxa that cannot be placed to any order or class using ITS sequences alone.However,in many instances,longer rRNA gene sequences and availability of both SSU and LSU reads are needed to improve taxonomic resolution.By leveraging third-generation sequencing from global soil samples,we successfully provided phylogenetic placement for many previously unidentified sequences and broadened our view on the fungal tree of life,with 10-20%new order-level taxa.In addition,the PacBio sequence data greatly extends fungal class-level information in reference databases.
