Hydrodynamics

流体力学
  • 文章类型: Journal Article
    气液旋流器的井下环境中会出现复杂的振动现象,影响水力旋流器内的流场。为了研究振动对水力旋流器分离的影响,在振动耦合条件下,对井下气液旋流器的流场特性进行了分析和研究。基于计算流体动力学(CFD)计算固体力学方法(CSM)和流固耦合方法,建立了气液旋流器的流固耦合力学模型。发现在振动耦合条件下,水力旋流器流场三个方向的速度分量变化明显。切向速度和轴向速度的峰值减小,并且径向速度的不对称性增加。溢流管内涡度和湍流强度的分布规律变差。其中,溢流管的涡度强度明显增强,壁附近湍流强度越高,占据的面积分布范围越大。水力旋流器的气液分离效率会随着螺杆泵转速的增加而降低,还原程度可达10%以上。然而,这种效应会随着螺杆泵转速的增加而减小,因此,由转速引起的激励效应对流场具有最大限制。
    The complex vibration phenomenon occurs in the downhole environment of the gas-liquid hydrocyclone, which affects the flow field in the hydrocyclone. In order to study the influence of vibration on hydrocyclone separation, the characteristics of the flow field in the downhole gas-liquid hydrocyclone were analyzed and studied under the condition of vibration coupling. Based on Computational Fluid Dynamics (CFD), Computational Solid Mechanics Method (CSM) and fluid-solid coupling method, a fluid-solid coupling mechanical model of a gas-liquid cyclone is established. It is found that under the condition of vibration coupling, the velocity components in the three directions of the hydrocyclone flow field change obviously. The peak values of tangential velocity and axial velocity decrease, and the asymmetry of radial velocity increases. The distribution regularity of vorticity and turbulence intensity in the overflow pipe becomes worse. Among them, the vorticity intensity of the overflow pipe is obviously enhanced, and the higher turbulence intensity near the wall occupies more area distribution range. The gas-liquid separation efficiency of the hydrocyclone will decrease with the increase of the rotational speed of the screw pump, and the degree of reduction can reach more than 10%. However, this effect will decrease with the increase of the rotational speed of the screw pump, so the excitation effect caused by the rotational speed has a maximum limit on the flow field.
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  • 文章类型: Journal Article
    目前对质量和热量传递的检查着眼于感应磁场的影响,可变热导率,以及二阶液体在拉伸表面上流动的活化能。还使用广义傅里叶和菲克定律模型处理了质量-传热。根据需要对模型方程进行转换,以产生非线性ODE系统,然后在BVP4C集成MATLAB方法的帮助下进行数值求解。通过表格和图形分析热质量流量参数。带有磁场参数(M)的二级流体参数(β)的估计值增加了速度草图。对于施密特数(Sc)的更强估计,磁场参数(M)和Eckert数(Ec)在温度曲线上具有增长行为。
    The present examination of mass and heat communication looks at the impact of induced magnetic field, variable thermal conductivity, and activation energy on the flow of second-order liquid across a stretched surface. The mass-heat transfer is also treated using the Model for generalized Fourier and Fick\'s Laws. The model equations are transformed as needed to produce a system of nonlinear ODEs, which are then numerically solved with the help of BVP4C integrated MATLAB approach. The heat-mass flow parameters are analyzed by the table and graphs. An increment in the estimations of 2nd grade fluid parameter (β) with magnetic field parameter (M) increase the speed sketch. For the stronger estimations of Schmidt number (Sc), parameter of magnetic field (M) and Eckert number (Ec) have the growing behavior on the temperature profile.
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  • 文章类型: Journal Article
    全球流域快速和不受控制的城市增长和土地利用变化导致大都市地区的地表径流增加,再加上气候变化,在雨季给居民带来风险。圣路易斯波托西市也不例外。一个受影响的水道是加丽塔溪流,在城市化附近的城市内部流动。根据该镇的历史降水数据,必须分析城市蔓延对这条河流的影响。进行这项研究需要水文和地形信息。流域的水文研究涉及分析该地区的地貌和历史气候数据。对于溪流的地形,使用无人驾驶飞行器(UAV)和全球导航卫星系统(GNSS)设备的航空摄影测量被用来在该地区进行地形测量。为了找出Garita溪流何时会溢出以及哪些地区最有可能被洪水淹没,使用1D进行数值建模,2D,和3D程序,如SWMM5(雨水管理模型),HEC-RAS(水文工程中心河流分析系统),和EDFC浏览器(环境流体动力学代码)。这些模型模拟了不同的重现期及其与该地区记录的当前洪水事件的相关性,从而进一步提出解决方案以减轻溢出问题。通过进行这些模拟和分析结果,可以根据GaritaStream引起的各种重现期的历史洪水事件,提出解决方案来解决该地区的溢出问题。
    Rapid and uncontrolled urban growth and land use changes in watersheds worldwide have led to increased surface runoff within metropolitan areas, coupled with climate change, creating a risk for residents during the rainy season. The city of San Luis Potosí is no exception to this phenomenon. One affected watercourse is the Garita Stream, which flows inside the city near urbanization. It is essential to analyze the effects of urban sprawl on this stream based on historical precipitation data for the town. Hydrological and topographical information were required to conduct this research. The hydrological study of the basin involved analyzing the region\'s geomorphology and historical climatological data. For the stream\'s topography, aerial photogrammetry using an unmanned aerial Vehicle (UAV) and Global Navigation Satellite System (GNSS) equipment was employed to conduct topographic surveys in the area. To find out when the Garita stream would overflow and which areas are most likely to flood, numerical modeling was done using 1D, 2D, and 3D programs like SWMM5 (Storm Water Management Model), HEC-RAS (Hydrologic Engineering Center\'s River Analysis System), and EDFC Explorer (Environmental Fluid Dynamics Code). These models simulated different return periods and their correlation with current flooding events recorded in the area, thereby further proposing solutions to mitigate overflow issues. By conducting these simulations and analyzing the results, solutions can be suggested to address the overflow problems in the area based on historical flood events at various return periods caused by the Garita Stream.
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  • 文章类型: Journal Article
    最近的COVID-19大流行引起了人们对有效空气消毒解决方案的兴趣。杀菌紫外线(GUV)辐射的应用是防止COVID-19空气传播以及其他现有和未来传染性空气传播疾病的绝佳竞争者。虽然GUV已被证明可有效灭活SARS-CoV-2,但有关紫外线敏感性和剂量要求的定量数据,需要预测和优化GUV解决方案的性能,仍然有限。在这项研究中,研究了雾化SARS-CoV-2对254nm紫外线(UV)辐射的紫外线敏感性。这是通过在配备有上层UV-C照明器的测试室中采用基于3D计算流体动力学的SARS-CoV-2灭活模拟并将结果与在同一测试室中执行的先前发布的测量进行比较来完成的。在这项研究中发现的紫外线敏感性为(0.6±0.2)m2/J,这相当于在3和6J/m2之间的D90剂量。这些值与基于文献中报道的其他电晕病毒和灭活数据的先前估计在相同的范围内。
    The recent COVID-19 pandemic has raised interest in efficient air disinfection solutions. The application of germicidal ultraviolet (GUV) irradiation is an excellent contender to prevent airborne transmission of COVID-19, as well as other existing and future infectious airborne diseases. While GUV has already been proven effective in inactivating SARS-CoV-2, quantitative data on UV susceptibility and dose requirements, needed to predict and optimize the performance of GUV solutions, is still limited. In this study, the UV susceptibility of aerosolized SARS-CoV-2 to 254 nm ultraviolet (UV) irradiation is investigated. This is done by employing 3D computational fluid dynamics based simulations of SARS-CoV-2 inactivation in a test chamber equipped with an upper-room UV-C luminaire and comparing the results to previously published measurements performed in the same test chamber. The UV susceptibility found in this study is (0.6 ± 0.2) m2/J, which is equivalent to a D90 dose between 3 and 6 J/m2. These values are in the same range as previous estimations based on other corona viruses and inactivation data reported in literature.
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  • 文章类型: Journal Article
    水温调节设备的选择在车间设计中起着至关重要的作用。目前,水温控制设备的选择通常是根据鱼塘的容积和热参数计算,结合水产养殖经验。由于环境等因素,经验公式仅在特定条件下有效,气候,和鱼类类型,导致设备选择结果不准确。认识到这一限制,本文提出应用温度场的CFD模拟精确计算室内空气与水的热交换值,从而预测水产养殖车间水产养殖活动期间的热交换值。为设备选型提供了新的途径。本文选取大连某河豚养殖车间为模拟对象,建立三维非稳态计算流体动力学模型。该模型考虑了室外温度,太阳辐射,和水中相变传热。与实验数据的比较显示,模拟结果的均方根误差为0.46°C。在夏天,最高的冷却负荷发生在16:00,达到94.6千瓦。建议采用大金GCHP-40MAH地源热泵作为水温控制设备。CFD模拟验证了其在安装后塑造室内温度场的有效性。可以在一定程度上减少对水温控制设备的投资。这为水产养殖车间水温设备的选择提供了参考价值。
    The selection of water temperature regulation equipment plays a crucial role in the design of workshops. At present, the choice of water temperature control equipment is usually based on the volume of the fish pond and thermal parameter calculation, combined with aquaculture experience. Empirical formulas only work in specific conditions due to factors like the environment, climate, and fish types,resulting in inaccurate equipment selection outcomes. Recognizing this limitation, this paper proposes to apply CFD simulation of the temperature field to accurately calculate the heat exchange value between indoor air and water, thereby predicting the heat exchange values during aquaculture activities in the aquaculture workshop. providing a new approach for equipment selection. This paper selects a puffer fish breeding workshop in Dalian as the simulation object, establishing a 3D unsteady-state Computational Fluid Dynamics model. The model considers outdoor temperature, solar radiation, and phase-change heat transfer in water. Comparison with experimental data reveals a root mean square error of 0.46°C for the simulated results. During summer, the highest cooling load occurs at 16:00, reaching 94.6 kW. It is recommended to employ the Daikin GCHP-40MAH ground source heat pump as the water temperature control equipment. CFD simulation validates its effectiveness in shaping the indoor temperature field post-installation. the investment in water temperature control equipment can be reduced to a certain degree. This provides a reference value for the selection of water temperature equipment in aquaculture workshops.
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  • 文章类型: Journal Article
    有效的保护区网络中的海洋学连通性对于恢复和稳定海洋种群至关重要。然而,连通性的时间变化很少被认为是设计和评估海洋保护规划的标准。在这项研究中,定义了指标来表征发生的时间变异性,通量,以及地中海西北部地区的连通性频率。在气候年和2006-2020年之间的三年中,对被动粒子传输模型的运行提供的半理论估计的连接进行了测试,表明与气候年的偏差很大。这些指标允许比较四个区域连通性的时间变化,强调了由于它们的位置和中尺度流体动力学而导致的连通性差异,并确定了需要进一步调查的领域。这三个指标还表明,连通性的时间变异性受到粒子传输持续时间和深度的影响,尽管在比较区域的指标变化中未观察到一致的模式。前提是在参数化运输模型时将给出具体目标(即,焦点物种和时间段的选择),连通性的时间变异性指标有可能支持空间保护规划,优先保护海洋资源,并衡量海洋保护区的有效性,符合海洋管理的长期愿景。
    Oceanographic connectivity in an effective network of protected areas is crucial for restoring and stabilising marine populations. However, temporal variability in connectivity is rarely considered as a criterion in designing and evaluating marine conservation planning. In this study, indicators were defined to characterise the temporal variability in occurrence, flux, and frequency of connectivity in a northwestern Mediterranean Sea area. Indicators were tested on semi-theoretically-estimated connections provided by the runs of a passive particle transport model in a climatological year and in three years between 2006-2020, showing large deviation from the climatological year. The indicators allowed comparing the temporal variability in connectivity of four zones, highlighted differences in connectivity due to their locations and the mesoscale hydrodynamics, and identified areas that require further investigation. The three indicators also showed that the temporal variability in connectivity was influenced by the duration and depth of particle transport, although no consistent pattern was observed in the indicator variations of the compared zones. Provided that specific objectives will be given when parameterising transport models (i.e., selection of focus species and time period), indicators of temporal variability in connectivity have potential to support spatial conservation planning, prioritise the protection of marine resources, and measure the effectiveness of Marine Protected Areas, in line with a long-term vision of ocean management.
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  • 文章类型: Journal Article
    在过去的一个世纪中,切萨皮克湾内的牡蛎数量已经大幅减少,主要是由于不受管制的人类活动和疾病。法规和恢复工作的重点是恢复牡蛎种群,同时考虑其提供生态系统服务的能力,例如海岸保护和水质改善,在其他人中。为了促进牡蛎的生长和新种群的定居,最近在美国东海岸采用的技术是使用牡蛎城堡(OC)。事实证明,OC可以有效地招募和保留牡蛎,并促进牡蛎栖息地的垂直生长和水平扩展。OCs广泛用于沿海保护,作为常见工程解决方案的绿色替代方案。我们量化了在早期阶段(即没有牡蛎的城堡)围绕这些OC发生的流体动力学差异,并通过一系列实验室实验,充分开发的牡蛎覆盖了城堡的表面。实验是在伊利诺伊大学生态水力学和生态形态动力学实验室(EEL)的循环Odell-Kovasznay型通道中进行的。OCs(有和没有牡蛎)以1:7的比例进行3D打印以适应运河,和粒子图像测速(PIV)用于二维流动表征。数据显示,当覆盖有牡蛎时,城堡顶部的流动加速度存在明显差异,以及在牡蛎覆盖的城堡顶部和周围的湍流动能的产生和分布增加。在淹没和接近紧急情况下,牡蛎的存在也会影响雷诺应力的大小和空间分布。与灰色和牡蛎覆盖的OC的阻力系数估计相关的挑战强调了除了中心线2DPIV输出之外还需要更多数据。进一步研究涉及流动的整个三维结构,在单向和振荡条件下,将使我们能够提供有关牡蛎密集的防波堤的设计和使用的相关指南,作为在低能耗环境中进行沿海保护的可行的基于自然的解决方案。
    Oyster populations within the Chesapeake Bay have been drastically reduced over the last century mainly due to unregulated human activities and diseases. Regulations and restoration efforts have focused on restoring oyster populations while also considering their ability to provide ecosystem services, such as coastal protection and water quality improvement, among others. To promote oyster growth and the settlement of new populations, a recent technique adopted along the east coast of the US is the use of oyster castles (OCs). OCs have proven effective in recruiting and retaining oysters and in promoting both vertical growth and horizontal expansion of oyster habitats. OCs are widely used in coastal protection as greener alternative to common engineering solutions. We quantified hydrodynamic differences that occur around these OCs during their early stage (i.e. castles without oysters), and with fully developed oysters covering the surface of the castles through a series of laboratory experiments. The experiments were conducted in a recirculating Odell-Kovasznay type channel at the Ecohydraulics and Ecomorphodynamics Laboratory (EEL) at the University of Illinois. OCs (both with and without oysters) were 3D printed at 1:7 scale to fit the canal, and Particle Image Velocimetry (PIV) was used for 2D flow characterization. Data showed noticeable differences in flow acceleration atop the castles when covered with oysters, as well as an increase in the generation and distribution of turbulent kinetic energy atop and around the oyster-covered castles. Magnitudes and spatial distribution of Reynolds stresses were also affected by the presence of oysters in both submerged and near-emergent conditions. Challenges associated with the estimation of the drag coefficient for both gray and oyster-covered OCs highlighted the need for more data besides the centerline 2D PIV output. Further research involving the whole three-dimensional structure of the flow, in both unidirectional and oscillatory conditions, will allow us to provide relevant guidelines on the design and use of oyster-populated breakwaters as a viable nature-based solution for coastal protection within low-energy environments.
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  • 文章类型: Journal Article
    对非周期性能量输入的周期性响应,比如振荡,是生命系统的标志。基于纳米颗粒的系统在振荡特征的产生中很大程度上仍未被探索。这里,我们展示了一个具有对光的分层响应的纳米系统,其中热等离子体效应和可逆DNA杂交产生热对流力,最终,振荡流体动力流。金纳米粒子(AuNPs)的缓慢聚集作为正反馈,而快速光热拆卸作为负反馈。这些非对称反馈回路,结合时间延迟的热滞后,是协调振荡反应的基本要素。
    Periodic responses to nonperiodic energy inputs, such as oscillations, are hallmarks of living systems. Nanoparticle-based systems have largely remained unexplored in the generation of oscillatory features. Here, we demonstrate a nanosystem featuring hierarchical response to light, where thermoplasmonic effects and reversible DNA-hybridization generate thermal convective forces and ultimately, oscillatory hydrodynamic flows. The slow aggregation of gold nanoparticles (AuNPs) serves as a positive feedback, while fast photothermal disassembly acts as negative feedback. These asymmetric feedback loops, combined with thermal hysteresis for time-delay, are essential ingredients for orchestrating an oscillating response.
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  • 文章类型: Journal Article
    了解屏障环境中的水力线索如何影响鱼类航行对于大坝河流中的鱼类迁徙至关重要。然而,目前关于水力线索对鱼类航行影响的研究大多集中在单一水力参数对鱼类迁徙的影响上,往往忽略了鱼类的感官知觉和游泳能力。本研究提出了一种有效的方法,将河流的计算流体动力学模型与鱼类行为模型相结合,通过模拟鱼类对流动方向的感知及其对多个水力参数的调节,阐明屏障环境中水力线索对鱼类迁徙路径和策略的影响。对大坝的四种释放方案进行了审查,并确定建模的鱼类运动真实地反映了实际观察结果。在各种情况下,目标鱼(Schizothoraxchongi)设法向上游移动到大坝下游的尾水,尽管河流主干区形成了水力障碍;他们通过利用主干区两侧和河流边界层的低速带克服了这一障碍。在上游移动期间,目标鱼首选流速在0.7至1.0m/s之间,湍流动能小于0.3m2/s2的区域,以维持有氧活动。此外,审查了替代涡轮释放策略对目标鱼精细运动的影响,并提供了一种优化策略,该策略可以将进入鱼类通道设施的目标鱼的比例从原来的0%提高到53.8%,提高到82.6%。该研究为复杂水流环境下鱼类精细运动的模拟提供了一种可行的方法,也为堰塞河鱼类资源管理提供了科学依据。
    Understanding how hydraulic cues in the barrier environment affect fish navigation is critical to fish migration in dammed rivers. However, most of the current research on the effects of hydraulic cues on fish navigation focuses on the effects of a single hydraulic parameter on fish migration and usually ignores fish sensory perception and swimming ability. This study presents an effective approach that combines a computational fluid dynamics model of a river with a model of fish behaviour to elucidate the effects of hydraulic cues in the barrier environment on fish migration paths and strategies by simulating the fish\'s perception of flow direction and their regulation of multiple hydraulic parameters. Four release scenarios for the dam were reviewed and it was determined that the modelled fish movements realistically reflected actual observations. In various scenarios, the target fish (Schizothorax chongi) managed to move upstream to the tailrace downstream of the dam, despite the hydraulic barrier created by the mainstem area of the river; they overcame this obstacle by exploiting low-velocity zones on both sides of the mainstem and in the river\'s boundary layer. During upstream movement, the target fish preferred areas with flow velocities between 0.7 and 1.0 m/s and a turbulent kinetic energy of less than 0.3 m2/s2 to maintain aerobic activity. Additionally, the effects of alternative turbine release strategies on the fine-motor movement of target fish were reviewed and an optimised strategy was provided that could increase the proportion of target fish entering the fish passage facility from 0% to 53.8% in the original scenario to 82.6%. This study provides a feasible method for the simulation of fish fine motion in complex flow environments as well as a scientific basis for the management of fish resources in dammed rivers.
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  • 文章类型: Journal Article
    水通道蛋白(AQP),特别是AQP4,在调节大脑中的流体动力学中起着至关重要的作用,影响创伤性脑损伤(TBI)后水肿的发展和解决。这篇综述探讨了损伤后AQP表达和定位的变化。探讨其对脑水肿和整体损伤结局的影响。我们讨论了调节AQP表达的潜在分子机制,强调调节AQP功能的潜在治疗策略。这些见解提供了对TBI中AQPs的全面理解,并提出了通过有针对性的干预措施改善临床结果的新方法。
    Aquaporins (AQPs), particularly AQP4, play a crucial role in regulating fluid dynamics in the brain, impacting the development and resolution of edema following traumatic brain injury (TBI). This review examines the alterations in AQP expression and localization post-injury, exploring their effects on brain edema and overall injury outcomes. We discuss the underlying molecular mechanisms regulating AQP expression, highlighting potential therapeutic strategies to modulate AQP function. These insights provide a comprehensive understanding of AQPs in TBI and suggest novel approaches for improving clinical outcomes through targeted interventions.
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