浮式风电装备动态响应敏感性参数分析

为研究各参数对浮式风电装备动态响应的影响程度,寻找响应变化规律和设计优化方向,根据海装6.2 MW浮式风电装备参数进行一体化仿真。结合规范要求、设计经验和环境条件特点,针对不同环境条件的重现期、风谱类型、波浪谱类型、极端阵风周期进行参数敏感性分析,得到浮式风电装备不同部分动态响应结果。结果表明：不同环境条件的重现期和组合方式对运动响应和锚链张力影响十分明显,对机组载荷的影响则与机组所处状态相关;风谱类型主要影响机组载荷,对平台运动和锚链张力影响不大,考虑空间相干性的湍流风谱结果最危险;波浪谱类型对运动幅值和锚链张力极值影响较大,在发电工况下对机组载荷的影响较小,但在空转工况下对机组载荷的影响较大;阵风周期对运动响应、塔筒载荷、机舱加速度影响相对明显,但对轮毂载荷、锚链张力影响不大。     

半潜式钻井平台内波工况定位能力

采用MOSES软件建立动力定位半潜式钻井平台分析模型,在时域内模拟平台在钻井作业过程中遭遇内波作用的耦合动力特性,分析平台在不同流速内波作用下的定位能力,并对动力定位系统的关键因素进行敏感性分析。研究结果显示：在同等环境载荷强度下,平台在船宽方向出现最大偏移;当内波流速小于1.0 m/s时,平台可基本满足钻井作业的定位要求,而当内波流速达2.0 m/s时,平台出现大幅值的水平偏移和倾角,需要解脱隔水管系统;提升推进器推力和增加推力敏感因子都有助于提升平台的抗内波能力,但都无法明显减小平台的水平偏移。因此,在遭遇高流速内波作用时,推荐平台撤离或调整船体首向。     

海上风电单桩基础服役状态现场监测

为了解风电结构在复杂环境中的真实服役状态,对2个风电单桩基础机位先后开展结构振动监测和水下地形扫测,通过分析现场实测数据,分析包含振动特性和冲刷情况在内的风机支撑结构服役状态,并结合设计数据对实测结果进行讨论。现场测试分析结果可为海上风电结构的服役状态监测和设计优化研究提供参考。     

考虑基于变分模态分解的冲击载荷截止因数影响的管系响应

针对海上浮式装置力学分析中选用不同截止频率阈值得到重构的冲击载荷对结构响应结果有较大影响的问题,采用变分模态分解(Variable Mode Decomposition, VMD)方法得到冲击载荷各本征模态函数、对应频谱的特征频率和最大加速度幅值。选取不同的截止因数,重构得到不同的冲击载荷。数值仿真结果表明：当截止因数为0.01时,重构的冲击载荷动力学响应与原始冲击载荷动力学响应基本保持一致;在保证足够的安全裕度的前提下,当截止因数选0.20时,可获得更低的截止频率。     

基于ARID控制系统的固定式海洋风机纵摇控制

针对固定式海洋风机在随机风浪载荷及其联合作用下产生的具有倒立摆运动特征的纵摇,研究采用主动转动惯量驱动系统(Active Rotary Inertia Driver, ARID)对海洋风机纵摇进行控制的问题。ARID控制系统通过伺服电机驱动转动惯性质量产生控制结构摆动的最优力矩,从而减小海洋风机的纵摇运动。基于拉格朗日原理建立海洋风机-ARID控制系统的理论分析模型;采用Simulink对海洋风机-ARID控制系统的有效性进行验证,并分析系统参数(控制算法参数、转动惯量比等)对控制效果的影响规律;设计海洋风机-ARID控制系统的振动台试验,设置多种载荷激励形式,验证控制系统的稳定性与广谱有效性。数值模拟和试验结果均验证了所建立的分析模型的正确性,表明ARID控制系统对风机的纵摇运动具有显著的控制作用,为ARID控制系统在具有倒立摆运动规律的工程结构中的应用奠定理论基础。     

环氧类玻璃高分子材料的热回收性能研究

采用动态交联技术制备了环氧类玻璃高分子材料（EPV）,将其制得的片材在不同模压条件下进行重复加工,考察了模压温度、模压时间和模压压力对EPV回收材料性能的影响。结果表明：重复加工没有造成EPV回收材料的降解;模压温度越高,模压时间越长,模压压力越大,越有利于EPV的愈合和重塑;在模压温度为180℃,模压压力为20 MPa,模压时间为10 min的较佳条件下,重复加工的EPV回收材料力学性能与初始EPV片材的接近。     

Separation of propylene and propane with a microporous metal–organic framework via equilibrium-kinetic synergetic effect

Adsorption separation of olefin and paraffin can greatly lower the energy consumption associated with the currently utilized distillation technique but remains a great challenge. Herein, we report the efficient separation of propylene (C₃H₆) and propane (C₃H₈) in a phosphate anion-functionalized metal–organic framework (MOF) ZnAtzPO₄ by synergetic effect of equilibrium and kinetics. The material features periodically expanded and contracted apertures decorated with electronegative groups, offering eligible pore shape and pore chemistry to effectively trap C₃H₆ under moderate isosteric heat of adsorption (27.5 kJ mol⁻¹) while obstruct the diffusion of C₃H₈. It simultaneously combines excellent thermodynamic selectivity (uptake ratio of 1.71) and kinetic selectivity (~31) for C₃H₆/C₃H₈ separation, meanwhile can be easily regenerated. Breakthrough experiment for C₃H₆/C₃H₈ gas mixture was conducted and confirmed the outstanding separation capability of ZnAtzPO₄. The equilibrium and kinetics cooperative C₃H₆/C₃H₈ adsorption separation was for the first time found in anion-functionalized MOFs, and further confirmed by computational studies.     

Competitive Cr3+ occupation in persistent phosphors toward tunable traps distribution for dynamic anti-counterfeiting

Red/near infrared (NIR) long persistent phosphors have received extensive attentions in biomedical, food inspection, iris recognition, biological imaging, etc. Herein, a new phosphor, Li₂ZnGe₃O₈:Cr³⁺, is reported with deep red persistent luminescence peaking at 708 nm. By adjusting the Cr³⁺ doping concentration, the competitive site occupation at [ZnO6] and [GeO6] polyhedral enables different traps behaviors including trap types, trap concentration and trap depth, which in turn leads to different afterglow duration time from 2 to 20 h. The persistent luminescence mechanisms originated from different trap models have been discussed, and it is found that they can cooperate or inhibit each other, enabling different luminescence depending on time. The dynamic anti-counterfeiting applications have been demonstrated, which provides a new way to rationally designing for multi-functional luminescent materials.     

Method for calculating dynamic yield stress of fresh cement pastes using a coaxial cylinder system

The calculation of the rheological parameters of fresh cement pastes plays a key role in understanding the rheology of cement-based mixes. Because cement paste is not a simple Bingham fluid, a suitable nonlinear model must be found for characterizing its flow. A test system in which the rotational speed or shear rate can be changed in multiple steps is regarded as a suitable rheological test protocol because the paste reaches a steady state. Furthermore, theoretical derivations show that the solution of the Couette inverse problem corresponding to the modified Bingham model and the Herschel–Bulkley (H-B) model is complex. However, a comparative analysis revealed that the yield stress of fresh paste could easily be obtained through a calculation process based on a Parabolic model. This study presents the complete calculation procedure for this model. The influence of the plug flow is considered, and test points with low minimum shear stress (τ_min) are excluded. Finally, the accuracy of the proposed method is verified through comparisons with the results obtained using mini-cone slump tests. These results show that the dynamic yield stress calculated using the expression of the Couette inverse problem based on the Parabolic model in consideration of the plug flow is very close to the yield stress obtained using the mini-cone slump flow test. This proves that the proposed method could precisely characterize the dynamic yield stress of cement pastes.     

The Impact of Fluid Dynamic Stress in Stirred Bioreactors – The Scale of the Biological Entity: A Personal View

From the start of industrial biotechnology, there has been a perception that biological entities are damaged by stirring, so-called ‘shear damage'. Often, it was the soft option to explain a loss of performance when it was due to other factors, such as bubble ingestion with proteins or on scale-up, where tip speed increased when it was due to decreased homogeneity, especially in pH. For many years, poor control and the range of analytical tools available made a more in-depth explanation difficult; and the concepts of ‘high' and ‘low shear' impellers, now largely disproven, increased it. Here, the size of the biological entity is compared to the Kolmogorov microscale of turbulence leading to a reasonably clear picture emerging. The article starts with the author's introduction to the issue approximately 42 year ago with enzymes, conveniently also the smallest entity; and finishes with the largest, filamentous fungi.