International Journal of Heat and Fluid Flow最新文献_第10页

Multi-physics field simulation study on in-situ pyrolysis characteristics of fractured tar-rich coal seam 裂隙型富焦油煤层原位热解特征多物理场模拟研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-25 DOI: 10.1016/j.ijheatfluidflow.2025.110155

Hong Liu, Zibo Huang, Mingjie Li, Jinjia Wei

In-situ pyrolysis of tar-rich coal refers to the process of extracting tar and gas through underground in-situ modification and heating of coal seams. This technology offers advantages such as a small land footprint, a wide range of resource extraction depths, and no surface subsidence. It represents a new clean and low-carbon utilization technology for coal resources. In this study, thermogravimetric experiment was firstly conducted to obtain the kinetic parameters of coal sample. Subsequently, the pyrolysis effects with and without hydraulic fractures were compared. And then, the in-situ pyrolysis characteristics of a 10 m × 10 m square coal seam under multi-physics field coupling with different hydraulic fracture parameters were investigated by numerical simulation. The effects of varying hydraulic fracture numbers and spacings on the flow heat transfer, structural evolution and product generation performance were analyzed. The results reveal that hydraulic fracturing can notably achieve higher permeability of coal seam, enhance the flow diversion capacity, produce more tar in the same period of time. When the coal seam contains three hydraulic fractures, it undergoes complete transformation earlier than that with one or five hydraulic fractures. The results suggests that more hydraulic fractures do not necessarily produce better outcomes, which is precisely conducive to balancing benefits and costs. All conditions stimulated with hydraulic fractures produce more than 8000 kg of tar within one year. At the beginning of pyrolysis, the smaller hydraulic fracture spacing leads to a relatively rapid increase in every indicator. With the progress of pyrolysis, the larger the hydraulic fracture spacing, the more these performance indicators improve, indicating that a larger fracture spacing facilitates rapid pyrolysis, fluid transportation, heat exchange and products output. The research results can provide a reference for the underground pyrolysis scheme of coal seams with fractures and offer guidance for the efficient and sustainable utilization of tar-rich coal.

富焦油煤原位热解是指对煤层进行地下原位改造和加热，提取焦油和天然气的过程。该技术具有占地面积小、资源开采深度广、地面不沉降等优点。它代表了一种新的煤炭资源清洁低碳利用技术。本研究首先进行了热重实验，获得了煤样的动力学参数。随后，对比了有无水力裂缝的热解效果。然后，通过数值模拟研究了10 m × 10 m方煤层在不同水力压裂参数下多物理场耦合作用下的原位热解特性。分析了不同水力裂缝数和裂缝间距对流动换热、结构演化和产品生成性能的影响。结果表明，水力压裂能显著提高煤层渗透率，增强导流能力，在同一时间内产生更多的焦油。当煤层含有3条水力裂缝时，其完全转化时间比含有1条或5条水力裂缝时要早。结果表明，更多的水力压裂并不一定产生更好的结果，这恰恰有利于平衡效益和成本。所有条件下的水力压裂在一年内都会产生超过8000公斤的焦油。在热解开始时，水力裂缝间距越小，各项指标的增加速度越快。随着热解过程的进行，水力裂缝间距越大，上述性能指标提高越多，说明裂缝间距越大，有利于快速热解、流体输运、换热和产物产量。研究结果可为裂隙煤层地下热解方案提供参考，为富焦油煤的高效可持续利用提供指导。

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引用次数: 0

Assessment of behavioural modification techniques on particle-laden turbulent pipe flows 含颗粒湍流管道流动行为改变技术的评估

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-25 DOI: 10.1016/j.ijheatfluidflow.2025.110144

B. Wolde, L.F. Mortimer, M. Fairweather

In this study, particle-laden turbulent pipe flows are predicted using direct numerical simulation of the fluid flow in combination with Lagrangian particle tracking and a deterministic energy-based particle agglomeration model, with a particular focus on predicting and elucidating the dynamics of particle–particle interactions. The models used, which were developed and validated in the present work, enhance our understanding of these flows, particularly in regards to the processes which lead to particle collision and agglomeration. The energy-based agglomeration technique is used together with four-way coupling between the particles and the fluid flow to predict particle aggregation due to collision interactions within the flow. Additionally, the impact of behavioural modification techniques, which influence particle dispersion, agglomeration and ultimately particle deposition, is investigated by varying influential parameters such as the temperature and Reynolds number of the flow, and the reduced surface potential, inverse Debye length, Hamaker constant and coefficient of restitution which govern particle–particle interactions. It is concluded that electric double layer repulsion exerts little influence on collision and agglomeration behaviour, attributable to the particle diameters examined being higher in comparison to the effective range of these forces. The study further demonstrates that the restitution coefficient has a significant influence on the behaviour of particle agglomeration, with a decrease in the coefficient resulting in increased aggregation rates. Hamaker constant and Reynolds number variations also both lead to major impacts on particle–particle interaction, with collision and agglomeration events occurring more frequently for increased Hamaker constant and Reynolds number.

在本研究中，采用流体流动的直接数值模拟，结合拉格朗日粒子跟踪和基于确定性能量的粒子聚集模型，预测和阐明了粒子-粒子相互作用的动力学，预测了颗粒负载的湍流管道流动。所使用的模型在目前的工作中得到了发展和验证，增强了我们对这些流动的理解，特别是在导致粒子碰撞和聚集的过程方面。利用基于能量的团聚技术，结合颗粒与流体之间的四向耦合，预测了流动中由于碰撞相互作用而产生的颗粒聚集。此外，影响颗粒分散、团聚和最终颗粒沉积的行为改变技术的影响，通过改变影响参数，如流动的温度和雷诺数，以及控制颗粒-颗粒相互作用的减少的表面电位、逆德拜长度、Hamaker常数和恢复系数，进行了研究。结果表明，电双层斥力对碰撞和团聚行为的影响很小，这是由于所检测的粒子直径比这些力的有效范围要大。研究进一步表明，恢复系数对颗粒团聚行为有显著影响，恢复系数的减小导致团聚速率的增加。Hamaker常数和雷诺数的变化也会对粒子间相互作用产生重大影响，随着Hamaker常数和雷诺数的增加，碰撞和团聚事件的发生频率更高。

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引用次数: 0

Development of explicit algebraic LES wall models using consistent CFD-driven Machine Learning 使用一致的cfd驱动机器学习开发显式代数LES壁模型

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-25 DOI: 10.1016/j.ijheatfluidflow.2025.110157

Arthur Shiniti Cato, Melissa Kozul, Richard Sandberg

A new consistent Machine Learning methodology to develop explicit algebraic wall models for Large Eddy Simulation (LES) is presented. Crucially, the wall models are trained using quantities from wall-modeled LES as inputs, and not filtered variables from a database, thus ensuring that resulting models are consistent with their final application environment. This is achieved by implementing the candidate wall models, created by the symbolic regression technique Gene-Expression Programming (GEP), into an LES solver and using the wall-modeled CFD outputs to construct the training cost function. The resulting models are explicit algebraic expressions and human-interpretable. Another benefit of this procedure is that it does not require dense high-fidelity data sets, although training is more computationally expensive. The framework was tested and validated using the well-established periodic hills case. Two cost functions were used separately: the mean skin friction coefficient distribution and a limited number of mean velocity profiles distributed over the domain. The wall models trained by the GEP algorithm were able to reconstruct the flow even with very under-resolved grids close to the wall for both scenarios. Despite the focus of the work being the Machine Learning method, we also tested the GEP model for other cases with similar physical features to analyze the flexibility of the model. The results are encouraging and show the potential of the developed training framework. An additional direct numerical simulation (DNS) is conducted of the periodic hills case to provide filtered ‘truth’ data. Comparing the inputs the wall model is provided from wall-modeled LES or from the filtered DNS data reveals substantial differences, both in terms of absolute values and range. This further justifies the present consistent approach of in situ wall-model training.

提出了一种新的一致机器学习方法，用于开发大涡模拟（LES）的显式代数壁面模型。至关重要的是，墙壁模型是使用来自墙壁建模的LES的数量作为输入来训练的，而不是使用从数据库中过滤的变量，从而确保生成的模型与其最终的应用程序环境一致。这是通过将由符号回归技术Gene-Expression Programming （GEP）创建的候选壁模型实现到LES求解器中，并使用壁模型CFD输出来构建训练成本函数来实现的。所得到的模型是显式的代数表达式和人类可解释的。这个过程的另一个好处是，它不需要密集的高保真数据集，尽管训练的计算成本更高。使用已建立的周期丘陵案例对该框架进行了测试和验证。分别使用两个成本函数：平均表面摩擦系数分布和分布在域上的有限数量的平均速度剖面。在这两种情况下，通过GEP算法训练的壁面模型即使在靠近壁面的网格分辨率非常低的情况下也能够重建流动。尽管工作的重点是机器学习方法，但我们也测试了具有类似物理特征的其他情况下的GEP模型，以分析模型的灵活性。结果令人鼓舞，并显示出已开发的培训框架的潜力。另外，对周期丘陵情况进行直接数值模拟（DNS），以提供过滤后的“真值”数据。比较wall模型由wall- modelles提供的输入和过滤后的DNS数据提供的输入，可以发现在绝对值和范围方面存在巨大差异。这进一步证明了目前一致的现场墙模型训练方法是正确的。

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引用次数: 0

Sustainable solar desalination via surface tension manipulation: Experimental analysis of charcoal powder in hemispherical stills 通过表面张力操纵的可持续太阳能脱盐：半球形蒸馏器中木炭粉的实验分析

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-25 DOI: 10.1016/j.ijheatfluidflow.2025.110150

Moataz M. Abdel-Aziz , Abd Elnaby Kabeel , Mohammed El Hadi Attia

This study introduces a novel approach for enhancing solar water distillation by manipulating the surface tension of basin water through the addition of coal powder in hemispherical solar stills. Unlike previous improvement techniques that primarily relied on phase change materials, nanoparticles, or geometric modifications, the present work focuses on modifying the interfacial properties of water to accelerate evaporation. Experimental investigations conducted under El-Oued, Algeria’s climatic conditions demonstrated that the coal powder significantly reduced the surface tension of saline water by 0.87 %, which in turn increased the evaporation rate and freshwater productivity. The modified hemispherical still produced 6.80 L/m2 of distilled water per day representing a 41.67 % increase compared with the conventional still and achieved 41.12 % higher daily efficiency with a 63.16 % reduction in production cost. The shortened recovery period of only 19 days highlights the economic feasibility of this surface-tension-driven approach. This work establishes coal powder as a sustainable, low-cost, and scalable enhancement for solar desalination systems, introducing a new mechanism of performance improvement based on interfacial thermodynamics rather than purely thermal energy storage.

本研究介绍了一种通过在半球形太阳能蒸馏器中加入煤粉来控制盆水表面张力的新方法。与之前主要依赖于相变材料、纳米颗粒或几何修饰的改进技术不同，目前的工作重点是改变水的界面特性以加速蒸发。在阿尔及利亚El-Oued的气候条件下进行的实验调查表明，煤粉显著降低了咸水的表面张力0.87%，这反过来又增加了蒸发速率和淡水生产力。改进后的半球形蒸馏器每天蒸馏水产量为6.80 L/m2，比传统蒸馏器提高41.67%，日效率提高41.12%，生产成本降低63.16%。回收周期缩短至19天，突出了这种表面张力驱动方法的经济可行性。这项工作确立了煤粉作为太阳能海水淡化系统的可持续、低成本和可扩展的增强剂，引入了一种基于界面热力学而不是纯粹的热能储存的性能改进新机制。

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引用次数: 0

Three-dimensional numerical investigation on the heat transfer and bypass flow characteristics in a pebble-bed high temperature gas-cooled reactor 球床高温气冷堆传热及旁通流动特性的三维数值研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-25 DOI: 10.1016/j.ijheatfluidflow.2025.110161

Wei Liu , Jin Shi , Shang-Zhen Yu , Qi Guo , Zi-Xuan Liu , Jin-Song Guo , Xue-Lin Li , Zeng-Yao Li

The pebble-bed high temperature gas-cooled reactor (HTGR) is a type of the Generation IV reactor. For the necessary thermal and radiation protection, the walls around the pebble bed are stacked with the graphite reflector layer and the carbon bricks. The bypass flow fails to effectively cool the fuel pebbles in the pebble bed and thus influences the efficiency and safety of HTGR. In this paper, a comprehensive three-dimensional model for HN-750 self-designed by HUANENG Group of China is established. A physically realistic mathematical model is proposed to investigate the convective heat transfer and the bypass flow characteristics in HN-750. The results indicate that the maximum temperature of the pebble bed with bypass flow is about 200 K higher than that without bypass flow, while the pressure drop in pebble bed is about 13 kPa lower than that without bypass flow. The bypass flow accounts for 29.25 % of the total helium flow, 24.43 % of which is the vertical gap bypass flow. The synergistic combination of square keys and sealing strips can effectively block nearly half of the vertical gap bypass flow. The present large-scale three-dimensional numerical calculations can support the thermal–hydraulic optimization and safety analysis of pebble-bed HTGRs.

球床高温气冷堆（HTGR）是第四代反应堆的一种。为了必要的热和辐射防护，卵石床周围的墙壁上堆放着石墨反射层和碳砖。旁路流动不能有效冷却球床内的燃料卵石，影响HTGR的效率和安全性。本文建立了华能集团自主设计的HN-750的综合三维模型。提出了一个物理上真实的数学模型来研究HN-750的对流换热和旁通流动特性。结果表明：有旁路流动时球床最高温度比无旁路流动时高约200 K，而球床压降比无旁路流动时低约13 kPa。旁路流量占总氦气流量的29.25%，其中垂直间隙旁路流量占24.43%。方键与密封条的协同组合，可有效阻断近一半的垂直间隙旁通流量。目前的大尺度三维数值计算可以为球床高温堆热工水力优化和安全性分析提供支持。

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引用次数: 0

A parametric study for a cascaded pin finned heat sink filled with phase change material of low melting point type 低熔点相变材料填充级联引脚翅片散热器的参数化研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-24 DOI: 10.1016/j.ijheatfluidflow.2025.110160

Sherin Moustafa , Gaosheng Wei , M. Abd El-Hamid

This study investigates the thermal performance of phase change material (PCM)-based heat sinks for portable electronic devices using ANSYS FLUENT. A novel multilayered PCM heat sink with pin fins is proposed, incorporating low melting point alloys (LMPA), paraffin, and both. The research compares single-layered and multilayered configurations, evaluating their performance under varying pin–fin volume fractions, heat sink orientations, PCM fill ratios, and heat flux values. The findings highlight significant thermal improvements, with multilayered PCM achieving an enhancement ratio of up to 1.12 compared to single-layered modules (1.03, 1.027, and 0.96). Increasing pin–fin volume fractions over fin thickness notably boosts performance, while a PCM fill ratio of 100 % at a high heat flux of 5000 W/m² extends melting time by 2.97 times compared to 25 %. Inclination angles of 30° deliver the lowest average temperatures and longest melting durations. Additionally, a 4 % fin volume fraction results in lower base temperatures than 16 % and 9 % at equivalent fin thickness. This research demonstrates the potential of multilayered PCM heat sinks with pin fins for enhancing thermal regulation in electronics, making them a promising solution for efficient heat dissipation under high-performance demands.

本研究利用ANSYS FLUENT对便携式电子器件用相变材料（PCM）散热器的热性能进行了研究。采用低熔点合金（LMPA）和石蜡（两者兼有），设计了一种新型的带针翅的多层PCM散热器。研究比较了单层和多层结构，评估了它们在不同鳍片体积分数、散热器方向、PCM填充比和热通量值下的性能。研究结果强调了显著的散热改善，与单层模块（1.03、1.027和0.96）相比，多层PCM实现了高达1.12的增强比。增加针翅体积分数比翅片厚度显著提高性能，而在5000 W/m2的高热流密度下，PCM填充率为100%，与25%相比，熔化时间延长了2.97倍。30°的倾角提供最低的平均温度和最长的融化持续时间。此外，在相同的鳍片厚度下，4%的鳍片体积分数比16%和9%的鳍片体积分数更低。本研究证明了带引脚鳍的多层PCM散热器在增强电子器件热调节方面的潜力，使其成为高性能要求下高效散热的有前途的解决方案。

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引用次数: 0

Buoyancy opposed flow over a heated hollow sphere 浮力在加热的空心球体上与气流相反

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-24 DOI: 10.1016/j.ijheatfluidflow.2025.110137

Saykat Kumar Biswas , R. Chavez , N.K. Anand , Shuiwang Ji , Yassin A. Hassan

This study investigates the buoyancy-opposed turbulent flow over a heated hollow sphere placed inside a circular pipe by performing Large Eddy Simulation (LES). The Reynolds number (

R e

), based on the sphere diameter, and inlet velocity, was fixed at 16,000, while the Richardson number (

R i

) was varied from 0 to 2.21 to include both forced and mixed convection conditions. Argon was selected as the working fluid at an operating pressure of 3 MPa to reflect conditions relevant to the experimental data used for comparison. LES predictions were compared with available experimental and Numerical data. Detailed analysis was conducted on key flow and thermal characteristics, including the non-dimensional reattachment length (

L r / D

), separation angle (

θ_{s}

), measured from the upstream stagnation point, turbulent kinetic energy (

T K E / U_{\infty}^{2}

), Nusselt number (

N u

), and Strouhal number (

S t

). Moreover, Power Spectral Density (PSD) was performed on the co-efficient of lift (

C_{l}

) to determine the vortex shedding frequency (

f_{v s}

). The results demonstrated that, as

R i

increased, buoyancy effects increasingly opposed the main flow, resulting in longer reattachment lengths, shorter separation angles, and slightly smaller

S t

. This indicated that buoyancy caused the wake region to expand both in length and width. Furthermore, Proper Orthogonal Decomposition (POD) was performed on streamwise and cross-stream velocity components and it was found that the first 159 modes contained 90% of the total energy for

R i = 1.84

. Further analysis suggested that variation in

R i

has little effect on the system’s dimensionality.

本文采用大涡模拟（LES）的方法研究了放置在圆管内的加热空心球体上的浮力反方向湍流。基于球体直径和入口速度的雷诺数（Re）固定为16,000，而理查德森数（Ri）在0到2.21之间变化，包括强制对流和混合对流条件。选择氩气作为工作流体，工作压力为3 MPa，以反映对比实验数据的相关情况。将LES预测与现有的实验和数值数据进行了比较。对关键的流动和热特性进行了详细分析，包括无因次再附着长度（Lr/D）、上游滞止点测得的分离角（θs）、湍流动能（TKE/U∞2）、努塞尔数（Nu）、斯特劳哈尔数（St）。利用升力系数（Cl）的功率谱密度（PSD）来确定旋涡脱落频率（fvs）。结果表明，随着Ri的增加，浮力作用越来越与主流相反，导致再附着长度变长，分离角变短，st略小，这表明浮力使尾迹区域的长度和宽度都有所扩大。此外，对流向和横流速度分量进行适当正交分解（POD），发现Ri=1.84时，前159阶模态占总能量的90%。进一步分析表明，Ri的变化对体系的维数影响不大。

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引用次数: 0

Flow-induced vibration of an elastically mounted oblate spheroid with variable mass ratio 变质量比弹性椭球体的流激振动

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-24 DOI: 10.1016/j.ijheatfluidflow.2025.110129

Adrian Cordero Obando , Kerry Hourigan , Mark C. Thompson , Jisheng Zhao

<div><div>This study experimentally investigates the cross-flow flow-induced vibration (FIV) of an elastically mounted oblate spheroid with an aspect ratio of 2. The aspect ratio is defined as the ratio of the major diameter (<span><math><mi>b</mi></math></span>) in the cross-flow direction to the minor diameter (<span><math><mi>a</mi></math></span>) in the streamwise direction, namely <span><math><mrow><mi>ϵ</mi><mo>=</mo><mi>b</mi><mo>/</mo><mi>a</mi></mrow></math></span>. The FIV response was characterised over a range of reduced velocity, <span><math><mrow><mn>3</mn><mo>.</mo><mn>0</mn><mo>⩽</mo><msup><mrow><mi>U</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>=</mo><mi>U</mi><mo>/</mo><mrow><mo>(</mo><msub><mrow><mi>f</mi></mrow><mrow><mi>n</mi><mi>w</mi></mrow></msub><mi>b</mi><mo>)</mo></mrow><mo>⩽</mo><mn>12</mn><mo>.</mo><mn>0</mn></mrow></math></span>, where <span><math><mi>U</mi></math></span> is the free-stream velocity and <span><math><msub><mrow><mi>f</mi></mrow><mrow><mi>n</mi><mi>w</mi></mrow></msub></math></span> is the natural frequency of the system in quiescent water. The corresponding Reynolds number varied over the range <span><math><mrow><mn>5000</mn><mo>⩽</mo><mi>R</mi><mi>e</mi><mo>=</mo><mi>U</mi><mi>b</mi><mo>/</mo><mi>ν</mi><mo>⩽</mo><mn>20</mn><mspace></mspace><mn>000</mn></mrow></math></span>, with <span><math><mi>ν</mi></math></span> denoting the kinematic viscosity of the fluid. The mass ratio of the hydro-elastic system, defined as the ratio of the total oscillating mass (<span><math><mi>m</mi></math></span>) to the displaced fluid mass (<span><math><msub><mrow><mi>m</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span>), namely <span><math><mrow><msup><mrow><mi>m</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>=</mo><mi>m</mi><mo>/</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>d</mi></mrow></msub></mrow></math></span>, was varied from 32 to 250, while the mass-damping parameter <span><math><mrow><mrow><mo>(</mo><msup><mrow><mi>m</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>+</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>A</mi></mrow></msub><mo>)</mo></mrow><mi>ζ</mi></mrow></math></span> was kept almost constant at 0.20 for all the <span><math><msup><mrow><mi>m</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span> values tested, with <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>A</mi></mrow></msub></math></span> being the potential added-mass coefficient. The results reveal that the dynamic response exhibits two distinct FIV phenomena: vortex-induced vibration (VIV) and galloping-like vibration. The VIV region is characterised by a roughly bell-shaped and bounded amplitude of vibration response as a function of reduced velocity. The peak normalised vibration amplitude was observed to be <span><math><mrow><msubsup><mrow><mi>A</mi></mrow><mrow><mn>10</mn></mrow><mrow><mo>∗</mo></mrow></msubsup><mo>=</mo><mn>0</mn><mo>.</mo><mn>70</mn></mrow></math></span>. On the other hand, the galloping region is characterised by a

实验研究了长径比为2的弹性椭球体的横流流激振动。纵横比定义为横流方向的大直径(b)与顺流方向的小直径(a)之比，即λ =b/a。FIV响应的特征是在一个降低的速度范围内，3.0≤U∗=U/(fnwb)≤12.0，其中U为自由流速度，fnw为静水中系统的固有频率。对应的雷诺数在5000≤Re=Ub/ν≤20000范围内变化，ν表示流体的运动粘度。水弹性系统的质量比，定义为总振荡质量(m)与位移流体质量（md）之比，即m∗=m/md，从32变化到250，而质量阻尼参数(m∗+CA)ζ在所有测试的m∗值中几乎保持恒定在0.20，CA是潜在的附加质量系数。结果表明，动态响应表现出两种不同的FIV现象：涡激振动和驰动振动。VIV区域的特征是振动响应的大致钟形和有界振幅作为降低速度的函数。峰归一化振动幅值为A10 * =0.70。另一方面，驰骋区域的特征是振幅响应随U∗的增加而线性增加，超过临界值U∗=7.0，在测试的最高减速速度U∗=12时达到最大值A10∗≈2。有趣的是，保持(m∗+CA)ζ的恒定值而改变m∗会导致在m∗的大范围内几乎相同的最大振幅响应，类似于圆柱体的VIV。此外，发现m∗=32显示出硬策动样（即由有限幅度干扰触发的振动的开始）响应，而对于m∗大于或等于50的响应的特征是软策动样（即来自静止的小幅度激励）响应。

引用次数: 0

Optimization of nanofluid impinging jet systems for advanced electronic cooling: A critical review 用于先进电子冷却的纳米流体冲击射流系统的优化：综述

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-24 DOI: 10.1016/j.ijheatfluidflow.2025.110149

P. Balakrishnan

This review critically examines the integration of nanofluid properties and impinging jet configurations for enhanced electronic cooling applications, addressing thermal management challenges in an electronics market projected to reach USD 1,406.47 billion by 2034, where more than 55 % of failures are heat-related. The synergistic potential of Al₂O₃, CuO, TiO₂, SiC, and hybrid nanofluids is analysed, revealing heat transfer enhancements of 15–72 %, although performance strongly depends on operational parameters. Single jet systems deliver concentrated cooling with optimal efficiency at H/D ratios of 5–8, achieving peak Nusselt numbers near 7–8, whereas multiple jets ensure more uniform heat dissipation at lower H/D ratios (≈2) and intermediate S/D ratios (≈3), achieving a balanced trade-off between turbulence intensity, jet interaction, and surface cooling uniformity. However, multiple jets face challenges related to flow distribution and pressure drop. Hybrid nanofluids, particularly Al₂O₃–Cu combinations, exhibit Nusselt number increases of 63.5 % at Re = 24,000, demonstrating favourable performance–stability trade-offs. Nanoparticle characteristics significantly influence system behaviour, with optimal concentrations between 0.5–2 % required to balance enhanced thermal conductivity and fluid stability. The findings highlight the potential of optimized nanofluid impinging jets to overcome critical electronic thermal bottlenecks. However, practical implementation faces challenges related to increased viscosity and pumping power, along with long-term stability issues, high synthesis costs, and environmental concerns in large-scale deployment. Addressing these challenges requires focused research on standardized nanofluid preparation protocols, improved stability and scalability, and comprehensive life-cycle assessments of hybrid nanofluids and advanced jet configurations.

这篇综述批判性地研究了纳米流体特性和冲击射流配置的集成，以增强电子冷却应用，解决电子市场的热管理挑战，预计到2034年将达到1,4064.7亿美元，其中55%以上的故障与热相关。分析了Al2O3、CuO、TiO2、SiC和混合纳米流体的协同潜力，揭示了15 - 72%的传热增强，尽管性能在很大程度上取决于操作参数。单射流系统在H/D比为5-8时提供最佳效率的集中冷却，峰值努塞尔数接近7-8，而多射流在较低的H/D比（≈2）和中间的S/D比（≈3）下确保更均匀的散热，实现湍流强度、射流相互作用和表面冷却均匀性之间的平衡。然而，多喷嘴面临着与流动分布和压降相关的挑战。杂化纳米流体，特别是Al2O3-Cu组合，在Re = 24000时，努塞尔数增加了63.5%，表现出良好的性能稳定性权衡。纳米颗粒的特性显著影响系统行为，最佳浓度在0.5 - 2%之间，以平衡增强的导热性和流体稳定性。这些发现突出了优化的纳米流体撞击射流在克服关键的电子热瓶颈方面的潜力。然而，在实际应用中面临着粘度和泵送功率增加、长期稳定性问题、高合成成本以及大规模部署时的环境问题等挑战。解决这些挑战需要集中研究标准化的纳米流体制备方案，提高稳定性和可扩展性，以及混合纳米流体和先进射流配置的全面生命周期评估。

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引用次数: 0

Effects of air-injection pressure and nozzle diameter on flow and cavitation characteristics of aerated submerged waterjet 喷气压力和喷嘴直径对加气水下水射流流动和空化特性的影响

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-11-23 DOI: 10.1016/j.ijheatfluidflow.2025.110154

Shifeng Yan , Can Kang , Haixia Liu , Guangxin Ding , Hyoung-Bum Kim

The present study aims to elucidate flow and cavitation characteristics of the aerated submerged waterjet. A numerical study is conducted using the method incorporating the large eddy simulation (LES) and Schnerr-Sauer cavitation models. The numerical scheme is validated through an experimental work of visualizing cavitation clouds in submerged waterjet. With two nozzles of 2.0 and 4.0 mm in diameter, evolution of cavitation clouds is illustrated and compared under non-aeration and different air-injection pressures. The results show that cavitation intensity and air-injection pressure are not monotonically related. For the nozzle of 4.0 mm in diameter, the cavitation volume fraction reaches its maximum at an air-injection pressure of 0.3 MPa and declines drastically with further increasing the air-injection pressure. The shedding frequency of cavitation clouds varies inversely with the air-injection pressure. When increasing air-injection pressure, vortex structures remain similar for the nozzle of 2.0 mm in diameter, while for the larger nozzle, long and straight vortex structures prevail. Integrity of vorticity rings attenuates continuously with increasing air-injection pressure. The conclusions are expected to shed light on the mechanisms underlying cavitation evolution and inter-phase interactions in the aerated submerged waterjet.

本研究的目的是研究加气水下水射流的流动和空化特性。采用大涡模拟（LES）和Schnerr-Sauer空化模型相结合的方法进行了数值研究。通过水下水射流中空化云的可视化实验验证了该方法的有效性。以直径为2.0 mm和4.0 mm的两种喷嘴为例，对比了在不充气和不同喷气压力下空化云的演变过程。结果表明，空化强度与空气注入压力不是单调相关的。对于直径为4.0 mm的喷嘴，空化体积分数在喷气压力为0.3 MPa时达到最大值，随着喷气压力的进一步增大，空化体积分数急剧下降。空化云的脱落频率与空气注入压力成反比。增大喷气压力时，直径为2.0 mm的喷嘴涡结构基本保持不变，而较大的喷嘴涡结构以长而直的涡结构为主。涡度环的完整性随着喷气压力的增加而不断衰减。这些结论有望揭示水下加气水射流中空化演化和相间相互作用的机制。

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