Experimental Thermal and Fluid Science最新文献_第2页

Wind tunnel experimental study on drag reduction characteristics and mechanism of a wing with porous surface integrated with micro-blowing 多孔表面微吹一体化机翼减阻特性及机理的风洞试验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-04-01 Epub Date: 2026-01-17 DOI: 10.1016/j.expthermflusci.2026.111699

Hai Du , Yuhang Wei , Yang Zhao , Jiang Xu , Dongsheng Gong , Qiushi Li , Yunao He

Approximately 50% of the aerodynamic drag of an aircraft originates from viscous drag, within which skin-friction drag is the dominant component. Therefore, research on turbulent drag reduction holds both substantial economic value and scientific significance. In this study, the NASA SC (2)-0714 airfoil is selected as the research model, with porous media installed at the trailing edge. A combination of static force measurements and PIV experiments is employed to investigate the drag-reduction mechanism of a passive–active hybrid control strategy that integrates porous media with micro-blowing. Experimental results show that when only porous media are applied, the total drag of the airfoil decreases by 17.6% and the lift-to-drag ratio increases by 18.1%. With the addition of micro-blowing, the total drag reduction further reaches 20.1% and the lift-to-drag ratio improves by 20.8%. The local maximum drag reduction on the porous-wall surface of the airfoil reaches 33.4%, and is further enhanced to 40.2% under the influence of micro-blowing. Flow-field analysis reveals that the proposed passive–active hybrid control not only significantly reduces skin-friction drag, but also thickens the shear layer and decreases wall shear stress. Specifically, the average shear-layer thickness on the airfoil surface increases by 36.8% with porous media and further rises to 47.3% when combined with micro-blowing. In addition, this control strategy is capable of breaking up and lifting the vortex structures within the separation region, thereby substantially improving the overall aerodynamic performance.

飞机大约50%的气动阻力来自于粘性阻力，其中表面摩擦阻力是主要的组成部分。因此，湍流减阻研究具有重要的经济价值和科学意义。在本研究中，选择NASA SC(2)-0714翼型作为研究模型，在后缘安装多孔介质。采用静力测量和PIV实验相结合的方法，研究了多孔介质与微吹气相结合的被动-主动混合控制策略的减阻机理。实验结果表明，仅采用多孔介质时，翼型总阻力降低了17.6%，升阻比提高了18.1%。加入微吹后，总阻力进一步降低20.1%，升阻比提高20.8%。在翼型多孔壁面的局部最大减阻达到33.4%，在微吹的影响下进一步提高到40.2%。流场分析表明，被动-主动混合控制不仅能显著降低摩擦阻力，还能增厚剪切层，降低壁面剪应力。其中，多孔介质条件下翼型表面剪切层平均厚度增加36.8%，微吹风条件下翼型表面剪切层平均厚度增加47.3%。此外，该控制策略能够分解和提升分离区域内的涡结构，从而大大提高整体气动性能。

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引用次数: 0

Experimental study on the influence of multi-row vortex generators on static hydrofoil 多排涡发生器对静态水翼影响的实验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-04-01 Epub Date: 2026-01-23 DOI: 10.1016/j.expthermflusci.2026.111703

Pengzhong Wang , Zhenyu Su , Lan Ding , Lu Wang , Hongyang Zhao , Bin Huang

Vortex generators (VGs) suppress flow separation by introducing high-momentum fluid into the boundary layer, a technique that has been successfully implemented in aircraft and wind turbines. In hydraulic applications, VGs have also demonstrated effectiveness in controlling cloud cavitation. Previous research has primarily focused on single-row VG configurations, with limited studies on dual-row arrangements in wind turbines. Investigations into the effects of multi-row VGs (exceeding two rows) on flow field characteristics remain notably scarce. This study experimentally examines the cavitation and non-cavitation characteristics of a NACA63820 hydrofoil equipped with five-row micro vortex generators (mVGs), with particular emphasis on their influence on the hydrodynamic performance of stationary hydrofoils under both cavitating and non-cavitating conditions. The results reveal three key findings. First, regarding hydrodynamic torque, the multi-row mVGs exhibit negligible effects on the torque coefficient under non-cavitating conditions. However, under cavitating conditions, they significantly reduce the torque at angles of attack (AoA) below 6° compared to a smooth hydrofoil, while inducing higher torque at AoA exceeding 6°. Second, for cavitation-induced flow noise, the multi-row VGs effectively reduce the total sound pressure level (TSPL) at AoA below 6°, but substantially amplify hydrofoil-generated noise at higher AoA. Third, concerning cavitation patterns, the multi-row VGs modify the spatial distribution of surface cavitation, resulting in more uniform coverage while simultaneously increasing the frequency of cavitation shedding.

涡旋发生器（vg）通过将高动量流体引入边界层来抑制流动分离，该技术已成功应用于飞机和风力涡轮机。在水力应用中，VGs在控制云空化方面也证明了有效性。以往的研究主要集中在单排涡发生器配置上，对风力涡轮机双排涡发生器配置的研究有限。关于多排涡发生器（超过两排）对流场特性影响的研究仍然非常少。实验研究了配备五排微涡发生器（mvg）的NACA63820型水翼船的空化和非空化特性，重点研究了空化和非空化条件下对固定水翼船水动力性能的影响。研究结果揭示了三个关键发现。首先，对于流体动力扭矩，在非空化条件下，多排mVGs对扭矩系数的影响可以忽略不计。然而，在空化条件下，与光滑水翼相比，它们在攻角（AoA）低于6°时显著降低扭矩，而在攻角超过6°时产生更高的扭矩。其次，对于空化引起的流动噪声，多排VGs在AoA低于6°时有效降低了总声压级（TSPL），但在更高AoA时大幅放大了水翼产生的噪声。第三，在空化形态方面，多排VGs改变了表面空化的空间分布，使其覆盖更加均匀，同时也增加了空化脱落的频率。

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引用次数: 0

Heat transfer mechanism of vortex structure evolution in dual synthetic jets over a heating plate 加热板上双合成射流涡结构演变的传热机理

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-04-01 Epub Date: 2026-01-05 DOI: 10.1016/j.expthermflusci.2026.111689

Yuanyuan Liu, Xinyu Liang, Wenqiang Peng, Zhenbing Luo, Xinyu Xie, Xiong Deng

Multiple-orifice synthetic jets have garnered significant attention in recent research due to their exceptional heat transfer performance in small installations. To achieve a larger heat dissipation area while minimizing installation height, this study employs dual synthetic jets impinging on a heated plate and investigates the influence of installation height (h_i/w_o) on the heat transfer characteristics. The heat transfer mechanisms associated with vortex structure evolution are analyzed using particle image velocimetry (PIV) and an infrared camera, thereby facilitating a deeper understanding of flow-thermal coupling behavior. It was found that h_i/w_o significantly alters the evolution of vortex structures at a nearly constant jet Reynolds number (Re_j ≈ 1600). The optimal heat transfer performance (Nu_max ≈ 136) was achieved at h_i/w_o = 2–3, balancing the unsteady benefit and near-wall flow enhancement. At this installation height, the inner primary vortex (IPV) rolls up moderately and partially merges its vorticity with the wall shear layer (WSL), while secondary vortices (SVs), SV-1 and SV-2, emanate from the outer primary vortex (OPV). The appropriate vorticity distributions of SV-1 and SV-2 promote the entrainment of ambient fluid and fluctuate the WSL. The spectral analysis further substantiates the presence of unsteady benefit. Both Welch spectra and Spectral POD mode confirmed that h_i/w_o = 2–3 delivers the best coherence maintenance, indicating an overall optimal benefit from heat transfer. Conversely, an insufficient installation height (h_i/w_o = 0–1) mitigated IPV roll-up. Although higher momentum flux and periodic kinetic energy were attained near the orifice, the convective heat transfer coefficient decayed rapidly. Excessive installation height (h_i/w_o = 4) allowed complete IPV roll-up. IPV breaks down into secondary vortices before merging into the WSL, resulting in deteriorated heat transfer performance.

在最近的研究中，由于多孔合成射流在小型装置中具有出色的传热性能，因此引起了人们的极大关注。为了在最小化安装高度的同时获得更大的散热面积，本研究采用双合成射流冲击加热板，研究安装高度（hi/wo）对传热特性的影响。利用粒子图像测速（PIV）和红外相机分析了与涡结构演变相关的传热机制，从而有助于更深入地了解流-热耦合行为。研究发现，在近似恒定的射流雷诺数（Rej≈1600）下，hi/wo显著改变了涡结构的演化。在hi/wo = 2-3时，获得了最佳换热性能（Numax≈136），平衡了非定常效益和近壁面流动增强。在该安装高度，内主涡（IPV）适度卷起并与壁面剪切层（WSL）部分合并，次涡（sv） SV-1和SV-2由外主涡（OPV）发出。SV-1和SV-2适当的涡度分布促进了周围流体的夹带，使WSL波动。谱分析进一步证实了非定常效益的存在。韦尔奇光谱和光谱POD模式都证实，hi/wo = 2-3提供了最佳的相干维持，表明传热的整体最佳效益。相反，安装高度不足（hi/wo = 0-1）会减少IPV的上卷。虽然在孔口附近获得了较高的动量通量和周期动能，但对流换热系数衰减很快。过高的安装高度（hi/wo = 4）允许完全卷起IPV。IPV在合并到WSL之前分解成二次涡，导致换热性能恶化。

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引用次数: 0

Mixing and combustion of methanol and ethanol high-pressure sprays 甲醇和乙醇高压喷雾的混合和燃烧

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-04-01 Epub Date: 2026-01-20 DOI: 10.1016/j.expthermflusci.2026.111704

Kevin Wan , Junghwa Yi , Lyle Pickett , Julien Manin

Time-resolved liquid and vapor mixing and combustion of methanol and ethanol from high-pressure sprays are measured by employing simultaneous high-speed diffuse-back illumination extinction imaging (DBI-EI), Rayleigh scattering, and OH* chemiluminescence. The experiments are performed in a constant-volume vessel at 22.8 kg/m

^{3}

and 800–1200 K. Methanol exhibits a longer liquid length and slightly faster vapor penetration than ethanol. Methanol liquid droplets suspected to be nanometer-scale, invisible to the DBI-EI diagnostic, are observed via scattering several millimeters downstream of the extinction-measured liquid length. On the other hand, the DBI-EI technique appears suitable for measuring ethanol liquid length at these conditions. A 1-D adiabatic jet mixing model and vapor–liquid equilibrium approximations shed insights on differences in mixing and evaporation. Methanol is shown to be the most sensitive to perturbations from equilibrium. The alcohols require relatively little mixing to approach near-stoichiometric conditions and are thus weakly sensitive to ambient oxygen levels, but fail to ignite below 1000 K ambient temperature, at least 200 K higher than needed for typical diesel-representative hydrocarbons such as n-dodecane. Instead, they require strong mixing to reach sufficient temperatures for ignition to counteract the strong evaporative cooling effects. The effect of 5% EHN is mild under these conditions, as it was estimated to lower the ignition temperature threshold by 40 K at most.

采用高速反向扩散消光成像（DBI-EI）、瑞利散射和OH*化学发光同时测量高压喷雾中液体和蒸汽的混合以及甲醇和乙醇的燃烧。实验在定容容器中进行，温度为22.8 kg/m3，温度为800-1200 K。甲醇表现出比乙醇更长的液体长度和稍快的蒸汽渗透。甲醇液滴被怀疑是纳米级的，DBI-EI诊断不可见，通过在消光测量的液体长度下游几毫米的散射观察到。另一方面，DBI-EI技术似乎适合在这些条件下测量乙醇液体长度。一维绝热射流混合模型和汽液平衡近似揭示了混合和蒸发的差异。甲醇对平衡态的扰动最敏感。在接近化学计量的条件下，酒精需要相对较少的混合，因此对环境氧水平不太敏感，但在1000 K的环境温度下无法点燃，至少比典型柴油代表碳氢化合物（如正十二烷）的温度高200 K。相反，它们需要强烈的混合以达到足够的点火温度，以抵消强烈的蒸发冷却效应。在这些条件下，5% EHN的影响是温和的，因为据估计它最多可以降低40 K的点火温度阈值。

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引用次数: 0

Droplet impact dynamics of spray coated superhydrophobic metal surfaces at various inclinations 不同倾角下喷涂超疏水金属表面的液滴冲击动力学

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-04-01 Epub Date: 2026-01-16 DOI: 10.1016/j.expthermflusci.2026.111697

B.V.R. Sai Krishna , Manas Kumar Pal

The wetting dynamics and impact behavior of water droplets on super hydrophobic (SHB) surfaces play a crucial role across wide range of applications. Hence several methods are developed for manufacturing of SHB surfaces. Among them, spray coating technique is quick, efficient and cost effective. In this study, three metal substrates are modified to exhibit superhydrophobic (SHB) properties via a unique spray coating. Droplet impact dynamics are investigated on both normal and SHB surfaces at various impact velocities (0.44–0.99 m/s) and surface inclinations (0°–60°). Key parameters including sliding length, maximum spreading factor (

β_{m a x}

), rebound height, contact time, coefficient of restitution (CR), and droplet detachment time are systematically analyzed.

Results show a notable reduction in

β_{m a x}

on SHB surfaces compared to normal ones, with

β_{m a x}

increasing with higher impact velocity and decreasing with increasing surface inclination. Empirical correlations for

β_{m a x}

as a function of Weber number are developed for both surface types, achieving prediction accuracies within

\pm 7 %

. On SHB surfaces, droplet rebound is observed, where rebound height increases and CR decreases with increase in impact velocity. Correlations for dimensionless contact time are also proposed, with similar predictive accuracy.

水滴在超疏水（SHB）表面的润湿动力学和冲击行为在广泛的应用中起着至关重要的作用。因此，开发了几种加工SHB表面的方法。其中，喷涂技术快速、高效、性价比高。在这项研究中，通过一种独特的喷涂涂层，对三种金属基板进行了改性，使其具有超疏水（SHB）性能。在不同的冲击速度（0.44-0.99 m/s）和表面倾角（0°-60°）下，研究了液滴在正常和SHB表面的冲击动力学。对滑动长度、最大扩散系数（βmax）、回弹高度、接触时间、恢复系数（CR）、液滴脱离时间等关键参数进行了系统分析。结果表明，与普通表面相比，SHB表面βmax显著降低，βmax随冲击速度的增加而增加，随表面倾角的增加而减小。对于这两种表面类型，βmax作为韦伯数函数的经验相关性都得到了发展，预测精度在±7%以内。在SHB表面观察到液滴的回弹，随着冲击速度的增加，回弹高度增加，CR减小。无因次接触时间的相关性也被提出，具有相似的预测精度。

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引用次数: 0

Combined effects of fine particles and surfactant on bubble and bubbly flow characteristics in a narrow rectangular column 细颗粒和表面活性剂对窄矩形柱内气泡和气泡流动特性的联合影响

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-04-01 Epub Date: 2026-01-19 DOI: 10.1016/j.expthermflusci.2026.111702

Ryo Kurimoto , Soichiro Horita , Kota Haruna , Kosuke Hayashi

Combined effects of fine particles and surfactant on bubbles and overall bubbly flows were investigated using image processing techniques. The distribution of bubble diameter d in the particle-laden surfactant solution shifted to larger diameter region with increasing measurement heights z due to bubble coalescence and lay between that in water and that in the particle-laden water. The distribution of the bubble aspect ratio E in the particle-laden surfactant solution did not vary with increasing z in contrast to that in the surfactant solution. The surfactant concentration available for adsorption onto the bubble interface was estimated by measuring the surface tension and was much lower than the setting value in the particle-laden surfactant solution due to surfactant adsorption onto particle surfaces. Additional measurements of d confirmed that the estimated concentration was adequate to inhibit bubble coalescence, while being inadequate to affect E. The distributions of the bubble velocity and gas holdup were also measured. In the particle-laden surfactant solution, the bubble velocity decreased while the gas holdup increased compared with those in the particle-laden water. This was attributed to the ratio of large d bubbles.

利用图像处理技术研究了细颗粒和表面活性剂对气泡和整体气泡流动的联合影响。随着测量高度z的增加，颗粒表面活性剂溶液中气泡直径d的分布由于气泡聚结而向直径较大的区域移动，位于水中和颗粒表面活性剂溶液中气泡直径d的分布之间。与表面活性剂溶液相比，颗粒表面活性剂溶液中气泡长径比E的分布不随z的增加而变化。通过测量表面张力来估计表面活性剂在气泡界面上的吸附浓度，由于表面活性剂在颗粒表面上的吸附作用，表面活性剂在颗粒表面上的吸附浓度远低于颗粒表面活性剂溶液的设定值。对d的额外测量证实，估计的浓度足以抑制气泡合并，而不足以影响e。气泡速度和气体含率的分布也被测量。在含颗粒表面活性剂溶液中，气泡速度比含颗粒水降低，气含率增加。这归因于大气泡的比例。

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引用次数: 0

Refuse derived fuels: Using near-infrared spectroscopy and machine learning to predict moisture content and dry particle spectra 垃圾衍生燃料：使用近红外光谱和机器学习来预测水分含量和干燥颗粒光谱

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-02-01 Epub Date: 2025-11-29 DOI: 10.1016/j.expthermflusci.2025.111678

J. Fischer , T. Kunz , K. Treiber , V. Scherer

Refuse derived fuel (RDF) sourced from industrial and municipal waste contains primarily plastics, paper/cardboard and textiles. Since RDF has high heating values and low prices, it is used as alternative fuel to coal in cement production, offering CO₂ reductions. However, the cement industry currently lacks real-time quality control of RDF, resulting in unnoticed reductions in heating value caused by elevated moisture content. Moisture content determination by drying takes up to 4 h, which does not allow for quick reactions in operation of the cement kiln.

This study addresses the challenge by applying near-infrared spectroscopy (NIRS) to predict the moisture content of paper and cardboard particles, which retains most moisture in RDF. The particles were moisturized by different methods with NIRS measurements at each stage. For the prediction, different approaches ranging from linear regression of selected wavelength absorptions to multiple machine learning regression techniques like ridge, lasso and multilayer perceptron are compared in accuracy and feature representation. The multilayer perceptron showed accurate results and robust feature selection, although also simple linear regression at selected wavelength gave adequate accuracy.

In a second step, moisture content and spectra of wet particles were used to predict the spectra of dry particles. These spectra are essential to correctly identify particle types or predict heating values, since training data consists of dry particle data. While linear models are not reaching acceptable results, both an autoencoder and a random forest regressor yielded spectra with correct shapes, which is sufficient for classification with derivative spectra.

来自工业和城市废物的垃圾衍生燃料（RDF）主要含有塑料、纸/纸板和纺织品。由于RDF具有高热值和低价格，它被用作水泥生产中煤炭的替代燃料，可以减少二氧化碳。然而，水泥行业目前缺乏RDF的实时质量控制，导致由于含水率升高而引起的热值未被注意到的降低。通过干燥来测定水分含量需要长达4小时，在水泥窑的操作中不允许快速反应。本研究通过应用近红外光谱（NIRS）来预测纸张和纸板颗粒的水分含量，这在RDF中保留了大部分水分。采用不同的方法对颗粒进行润湿，并在每个阶段进行近红外测量。对于预测，从选择波长吸收的线性回归到多机器学习回归技术（如ridge， lasso和多层感知器）的不同方法在准确性和特征表示方面进行了比较。多层感知器显示出准确的结果和鲁棒的特征选择，尽管在选择的波长上也有简单的线性回归给出了足够的精度。第二步，利用湿颗粒的水分含量和光谱来预测干颗粒的光谱。这些光谱对于正确识别颗粒类型或预测热值至关重要，因为训练数据由干燥颗粒数据组成。虽然线性模型没有达到可接受的结果，但自动编码器和随机森林回归器都产生了具有正确形状的光谱，这足以用于导数光谱的分类。

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引用次数: 0

Research on the atomization characteristics and influencing factors of tangential centrifugal nozzles 切向离心喷嘴雾化特性及影响因素研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-02-01 Epub Date: 2025-12-02 DOI: 10.1016/j.expthermflusci.2025.111679

Changchun Liu , Cheng Xu , Kaiyang Wu , Haoyue Xi , Shijie Xin , Lei Bai

Understanding the atomization characteristics of tangential centrifugal nozzles is crucial for optimizing applications in combustion, fire suppression, and cooling. This study experimentally investigates the P-Q curves, droplet size distribution, spray cone angle, and velocity vector field of eight nozzles, which were experimentally measured. The calculation method of the swirl number (S_n) in tangential centrifugal atomizing nozzles was systematically established. The flow coefficient (C_D) of various nozzles and its mathematical relationship with the swirl number, inlet and outlet diameters, and Reynolds number were determined. Additionally, a dimensionless parameter (Π), characterizing the Sauter Mean Diameter (SMD), was constructed based on the Reynolds number and swirl number. Both the inlet Reynolds number (Re_in) and swirl intensity govern droplet size. SMD demonstrates a characteristic U-shaped dependency on Π, with minimum values occurring at 0.4 < Π < 1.2. Furthermore, higher pressures produce smaller SMD values. Swirl intensity significantly impacts the spray cone angle, with larger swirl numbers leading to wider angles. It was also observed that the spray cone angle produced by the nozzle is not strictly symmetrical about the outlet’s center axis but exhibits a certain offset angle. Particle Image Velocimetry (PIV) measurements revealed that droplets at higher swirl numbers (S_n ≥ 2.5) are predominantly concentrated on both sides of the flow field. In contrast, at lower swirl numbers (S_n < 2.5), the flow field becomes more sensitive to pressure changes, promoting droplet accumulation in the central region of the nozzle outlet axis.

了解切向离心喷嘴的雾化特性对于优化其在燃烧、灭火和冷却方面的应用至关重要。本文对实验测量的8个喷嘴的P-Q曲线、液滴尺寸分布、喷射锥角和速度矢量场进行了实验研究。系统地建立了切向离心雾化喷嘴内旋流数Sn的计算方法。确定了不同喷嘴的流量系数及其与旋流数、进出口直径和雷诺数之间的数学关系。此外，基于雷诺数和旋流数构建了表征Sauter平均直径（SMD）的无量纲参数（Π）。入口雷诺数（Rein）和涡流强度都决定了液滴的大小。SMD表现出对Π特有的u形依赖，最小值出现在0.4 <； Π < 1.2。此外，较高的压力产生较小的SMD值。旋流强度对喷淋锥角有显著影响，旋流数越大，喷淋锥角越大。还观察到喷嘴产生的喷锥角并非严格对称于出口中心轴，而是存在一定的偏置角。粒子图像测速（PIV）显示，高旋流数（Sn≥2.5）的液滴主要集中在流场两侧。相比之下，在较低的旋流数（Sn < 2.5）下，流场对压力变化更加敏感，促使液滴在喷嘴出口轴中心区域积聚。

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引用次数: 0

A theoretical and experimental study on CCFL in a scaled-down model of a small modular reactor (SMR) hot leg 小型模块化反应堆热腿缩比模型中CCFL的理论与实验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-02-01 Epub Date: 2025-11-23 DOI: 10.1016/j.expthermflusci.2025.111664

Jie Wan , Xin Ma , Huafa Chen , Wan Sun , Yang Liu , Ren Liang , Longxiang Zhu , Luteng Zhang , Qiang Lian , Simiao Tang , Liang-Ming Pan

The Counter-Current Flow Limitation (CCFL) phenomena in horizontal and horizontal-inclined pipes have been extensively studied in the past. In recent years, small modular reactors (SMR) have attracted widespread attention as an ideal energy source for offshore development, which have a compact design with a small length-to-diameter ratio of the hot leg. Therefore, in this study, air–water CCFL visualization experiments were conducted in a scaled-down model of a SMR hot leg. The results indicated that, as the gas flow rate increases, the flow can be divided into three distinct regions: the stratified-entrainment region, the liquid-level rising region, and the liquid-level falling region, with CCFL occurring in the liquid-level rising region. A sudden decrease in the liquid penetration flow rate, which was measured by weighing method, was adopted as the criterion for the onset of CCFL, and then the CCFL characteristic curve was obtained. The mechanisms of CCFL were investigated over different ranges of liquid flow rates based on the characteristic curve and the results of the visualization experiment. Finally, a force analysis of the gas–liquid counter-current flow was performed based on the experimental results, and the momentum equations for gas and liquid phases were established to develop a CCFL prediction model. In addition, to complete the new model, several existing interfacial friction factor models were evaluated, and a modified interfacial friction factor model was developed.

在过去，人们对水平和水平倾斜管道中的逆流限流现象进行了广泛的研究。近年来，小型模块化反应堆（SMR）由于其设计紧凑、热腿长径比小，作为海上开发的理想能源而受到广泛关注。因此，在本研究中，在SMR热腿的缩小模型中进行了空气-水CCFL可视化实验。结果表明：随着气体流量的增大，气流可分为层状夹带区、液面上升区和液面下降区3个明显的区域，其中CCFL发生在液面上升区；采用称重法测量液体穿透流速的突然下降作为CCFL发生的判据，得到CCFL特性曲线。根据特性曲线和可视化实验结果，研究了不同液体流量范围内CCFL的机理。最后，基于实验结果对气液逆流流进行了受力分析，建立了气液相动量方程，建立了CCFL预测模型。此外，为了完善新模型，对现有的几种界面摩擦因子模型进行了评价，并建立了一个改进的界面摩擦因子模型。

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引用次数: 0

Experimental ‘In-situ’ Bayesian Active Learning: Sampling flow fields with a purpose 实验“原位”贝叶斯主动学习：有目的的采样流场

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-02-01 Epub Date: 2025-12-29 DOI: 10.1016/j.expthermflusci.2025.111688

Gonçalo G. Cruz , Xavier Ottavy , Fabrizio Fontaneto

Accurately characterizing complex flow fields often requires dense measurement grids. This paper presents an active learning methodology that enables efficient and targeted flow field characterization by dynamically guiding the selection of measurement locations while sampling the flow fields. The approach leverages a Gaussian Process model to represent the flow field and its uncertainty, while the Maximize Expected Prediction Error (MEPE) acquisition function balances exploration of undersampled high uncertainty regions with exploitation in areas of potential error. The active learning methodology is validated on the engineering relevant test case of the ECL5 Ultra-High Bypass Ratio (UHBR) fan, using experimental data acquired at the outlet measurement plane. The results demonstrate that the active learning approach can accurately capture all relevant flow features, including the hub corner separation and wake structures, using only 400 measurements, which is half the number of measurements that were sampled in traditional reference tests. This reduction in measurement effort resulted in a time saving of approximately one hour compared to the three-hour reference data acquisition. Furthermore, the methodology offers researchers flexibility in customizing the data acquisition process to their specific goals through the selection of appropriate stopping criteria. By strategically combining uncertainty and error thresholds, the active learning process can be adapted to achieve a desired balance between measurement effort, accuracy, and uncertainty levels. These findings highlight the possibilities of active learning to significantly enhance the efficiency and cost-effectiveness of experimental fluid mechanics research.

准确表征复杂流场往往需要密集的测量网格。本文提出了一种主动学习方法，通过在流场采样时动态指导测量位置的选择，实现高效和有针对性的流场表征。该方法利用高斯过程模型来表示流场及其不确定性，而最大期望预测误差（MEPE）获取函数平衡了对欠采样高不确定性区域的探索和对潜在误差区域的开发。在ECL5超高涵道比（UHBR）风机的工程相关测试用例上，利用出口测量平面采集的实验数据对主动学习方法进行了验证。结果表明，主动学习方法可以准确捕获所有相关的流动特征，包括轮毂角分离和尾迹结构，仅使用400次测量，这是传统参考测试中采样测量次数的一半。与3小时参考数据采集相比，测量工作量的减少节省了大约1小时的时间。此外，该方法通过选择适当的停止标准，为研究人员提供了定制数据采集过程的灵活性。通过战略性地结合不确定性和错误阈值，主动学习过程可以适应于在测量工作量、准确性和不确定性水平之间实现所需的平衡。这些发现突出了主动学习显著提高实验流体力学研究效率和成本效益的可能性。

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