Experimental Thermal and Fluid Science最新文献_第6页

Nanofluids mixed convection, heat transfer characteristics and effects of volume concentrations in the thermally developing region 纳米流体混合对流、传热特性及热发育区体积浓度的影响

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-30 Epub Date: 2025-10-21 DOI: 10.1016/j.expthermflusci.2025.111626

Ibrahim Umar Ibrahim , Mohsen Sharifpur , Josua P. Meyer

The vast majority of research on nanofluids only focuses on the heat transfer enhancement and pressure drop characteristics of these fluids. But apart from that, there are other intricate and complex phenomena that are very critical to the understanding of these fluid’s characteristics. The effects of free convection, entrance effects, and the influence of volume concentration on boundary conditions (i.e., laminar start and end, transition and turbulence) were often neglected. This limits our knowledge of these fluids. These phenomena were critical to understanding and fully utilising nanofluid potentials. Therefore, this research experimentally investigated the force and mixed convection of Al₂O₃ − MWCNT/water hybrid nanofluids. Three different concentrations of 0.30, 0.20, and 0.10 were prepared using the two-step method. Results show that an increase in volume concentration significantly affects nanofluid transition boundaries. Because critical Reynolds numbers for all the volume concentrations varied significantly, results show that critical Reynolds numbers of 0.3, 0.2 and 0.1 vol concentrations are Recr_. = 2140, 2200, and 2330, respectively. Thermal entrance influences were found to decrease with the increase in volume concentration. Mixed convection effects were increased with a decrease in volume concentration. Results also revealed that the Nusselt number of 0.3 vol concentration at Re = 1000 was enhanced by about 50 % within the thermal entrance length. In contrast, it was enhanced by about 48.84 % due to mixed convection. It was concluded that heat transfer enhancement was much better due to thermal entrance effects than with mixed convection. Also, the fluid viscosity depends on transition region boundaries, thermal entrance effects, and mixed convection heat transfer characteristics. Also, their characteristics often differ at different axial positions.

绝大多数关于纳米流体的研究只集中在纳米流体的强化传热和压降特性上。但除此之外，还有其他错综复杂的现象对理解这些流体的特性至关重要。自由对流、入口效应和体积浓度对边界条件（即层流开始和结束、过渡和湍流）的影响往往被忽略。这限制了我们对这些液体的了解。这些现象对于理解和充分利用纳米流体电位至关重要。因此，本研究通过实验研究了Al2O3 - MWCNT/水混合纳米流体的作用力和混合对流。采用两步法制备了0.30、0.20和0.10三种不同浓度。结果表明，体积浓度的增加显著影响纳米流体的过渡边界。由于不同体积浓度下的临界雷诺数变化很大，结果表明，0.3、0.2和0.1体积浓度下的临界雷诺数是最小的。= 2140、2200和2330。热入口的影响随着体积浓度的增加而减小。混合对流效应随体积浓度的降低而增强。结果还表明，在Re = 1000时，0.3 vol浓度的努塞尔数在热入口长度范围内提高了约50%。相比之下，混合对流使其增强约48.84%。结果表明，热入口效应比混合对流强化传热效果更好。此外，流体粘度取决于过渡区边界、热入口效应和混合对流换热特性。此外，在不同的轴向位置，它们的特性往往不同。

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引用次数: 0

Experimental investigation of turbulence in non-Newtonian fluids using ultrasound velocity profiling 非牛顿流体湍流的超声速度谱实验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-30 Epub Date: 2025-11-24 DOI: 10.1016/j.expthermflusci.2025.111665

B.K. Yusufi, Z. Kapelan , D. Mehta

Transportation of non-Newtonian fluids (NNFs) through pipelines is a cornerstone of modern infrastructure. While the laminar and transitional flows have been extensively studied, the turbulent behavior of NNFs remains poorly understood. This study investigates large-scale pipe-loop experiments on clay–water slurries, spanning Reynolds numbers

\approx 1.1 \times 1 0^{4} – 1.75 \times 1 0^{5}

in a 100-mm diameter facility. Using non-invasive ultrasound velocity profiling (UVP) together with wall shear stress measurements, we characterize flows ranging from weakly to highly non-Newtonian conditions with concentrations up to 19%(w/w). The experiments show that the transition to the log-law region is delayed and the log-law intercept shifts upward with increasing concentration, reflecting the redistribution of stresses as shear-thinning and yield effects become more pronounced. To further interpret these findings, the experimental observations were compared with established modeling approaches. Semi-empirical correlations exhibited intermediate performance (mean absolute error, MAE, up to 0.55 Pa for wall shear stress and 0.15 m/s for velocity), while the Launder–Spalding wall function performed worst due to its assumption of constant viscosity (MAE

\approx

1.48 Pa and 0.08 m/s). In contrast, the rheology-based wall function achieved the most reliable predictions, with minimal deviations from experiments (MAE

\approx

0.20 Pa for wall shear stress and 0.06 m/s for velocity). Overall, this work provides a comprehensive experimental and modeling assessment of turbulent non-Newtonian pipe flow at an industrial scale, yielding new insights into flow physics and establishing a valuable reference for future experimental and computational studies.

通过管道输送非牛顿流体（NNFs）是现代基础设施的基石。虽然层流和过渡流已经被广泛研究，但nnf的湍流行为仍然知之甚少。本研究在一个直径为100毫米的设备中，研究了粘土-水泥浆的大规模管环实验，其雷诺数≈1.1×104-1.75×105。利用无创超声速度剖面（UVP）和壁面剪切应力测量，我们描述了从弱到高度非牛顿条件下的流动，浓度高达19%（w/w）。实验表明，随着浓度的增加，向对数律区域的过渡延迟，对数律截距向上移动，反映了剪切减薄和屈服效应更加明显时应力的重新分布。为了进一步解释这些发现，将实验观察结果与已建立的建模方法进行了比较。半经验相关性表现出中等的表现（平均绝对误差，MAE，墙剪应力高达0.55 Pa，速度高达0.15 m/s），而laaid - spalding墙函数由于其恒定粘度的假设而表现最差（MAE≈1.48 Pa和0.08 m/s）。相比之下，基于流变学的壁面函数实现了最可靠的预测，与实验偏差最小（壁面剪切应力MAE≈0.20 Pa，速度MAE≈0.06 m/s）。总的来说，这项工作为工业规模的非牛顿管道湍流提供了全面的实验和建模评估，为流动物理提供了新的见解，并为未来的实验和计算研究奠定了有价值的参考。

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引用次数: 0

Quantification and mitigation of uncertainties in thermal conductivity measurements using a modified ASTM D5470 thermal resistance tester 使用改进的ASTM D5470热阻测试仪对热导率测量中的不确定性进行量化和降低

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-30 Epub Date: 2025-11-01 DOI: 10.1016/j.expthermflusci.2025.111636

Chinmaya Joshi , Clancy Milam , Stephen Pierson , Ying Sun , Jared Berg , Han Hu

In this paper, we have investigated the effect of thermal interface materials (TIMs) on the accuracy and uncertainty of thermal conductivity measurements. A modified ASTM D5470 thermal resistance tester (TRT) has been developed to measure the out-of-plane thermal conductivity of pyrolytic graphite (PG) and titanium grade 2 (TiG2) with and without TIMs. Compared to the ASTM D5470 standard, this modified design uses three thermocouples per side to support regressive analysis of the temperature profile and quantifies the uncertainty of the measurements with and without TIMs. Nine PG samples and four TiG2 samples of varying thickness have been tested to obtain thermal resistance as a function of sample thickness. The steady-state temperature profiles were used for heat flux and thermal resistance calculation. The results reveal that TIMs significantly reduce measurement uncertainty for both samples, i.e., 38.8 % for TiG2 and 27.8 % for PG. The effect of TIMs on the measurement accuracy diverges, with a far more pronounced effect on TiG2 than PG. This can be owed to the higher out-of-plane thermal conductivity of TiG2 (∼16.2 W/m-K) than PG (∼2 W/m-K). Contact resistance is expected to play a more critical role in tests of materials with higher thermal conductivity, and TIMs can effectively mitigate contact resistance. For lower conductivity materials, the weight of contact resistance is lower, and the effect of TIMs is thus less pronounced. This work establishes a robust framework for quantifying and mitigating uncertainties in thermal conductivity measurements, which will lead to more accurate characterization of materials for the design and qualification of advanced thermal management systems in aerospace, electronics, and energy applications.

本文研究了热界面材料（TIMs）对导热系数测量精度和不确定度的影响。研制了一种改进的ASTM D5470热阻测试仪（TRT），用于测量有或没有TIMs的热解石墨（PG）和2级钛（TiG2）的面外导热系数。与ASTM D5470标准相比，这种改进的设计每侧使用三个热电偶来支持温度分布的回归分析，并量化有和没有TIMs的测量的不确定性。对9个不同厚度的PG样品和4个不同厚度的TiG2样品进行了测试，得到了热阻与样品厚度的关系。用稳态温度曲线计算热流密度和热阻。结果表明，TIMs显著降低了两种样品的测量不确定度，即TiG2的测量不确定度为38.8%，PG的测量不确定度为27.8% . TIMs对测量精度的影响存在差异，TiG2的影响远比PG的明显，这可能是由于TiG2的面外导热系数（~ 16.2 W/m-K）高于PG （~ 2 W/m-K）。接触电阻有望在高导热材料的测试中发挥更关键的作用，而TIMs可以有效地降低接触电阻。对于电导率较低的材料，接触电阻的重量较低，因此TIMs的影响不太明显。这项工作为量化和减轻热导率测量中的不确定性建立了一个强大的框架，这将导致更准确的材料表征，用于航空航天，电子和能源应用中的先进热管理系统的设计和鉴定。

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引用次数: 0

Examination of urea water solution spray characteristics in hot cross flow 热交叉流中尿素水溶液喷射特性的检验

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-30 Epub Date: 2025-10-24 DOI: 10.1016/j.expthermflusci.2025.111635

P. Senthilkumar , T.N.C. Anand

Injecting Urea-Water sprays at low pressure into the hot exhaust gas flow stream in the presence of catalysts is one of the most effective ways to reduce NO

_{X}

emissions in diesel engines. The effectiveness of NO

_{X}

conversion is greatly impacted by spray parameters such as droplet size, velocity, dispersion, and homogeneity upstream of the catalyst. For estimating droplet size, Particle/Droplet Image Analysis (PDIA) is a reliable technique, and it has numerous benefits, including the ability to visualize the droplet shape and quantify non-spherical droplets. In this present study, the PDIA and Particle Tracking Velocimetry (PTV) techniques with high pixel resolution were used to look at the size and velocity of the droplets of the urea-water solution (UWS) spray in a heated cross-flow. The results indicate that smaller spherical droplets are located at the top of the spray, whereas the majority of the bigger droplets are non-spherical and present at the bottom. Droplet size decreases as injection pressure and air velocity rise due to improved atomization. Droplet velocity in the flow direction increases with air velocity and decreases with size. The PDIA method has the ability to measure both spherical and non-spherical droplets. When non-spherical droplets are excluded from droplet size measurements, there is a significant difference in the SMD measured, highlighting the importance of using a technique which can measure non-spherical droplets in such sprays. However, since the PDIA method is usually used with low repetition rate cameras, droplets must be captured over a range of imaging times, from the time they begin to appear in the field of view to the time they eventually disappear.

在催化剂存在的情况下，向热废气流中低压注入尿素水喷雾是减少柴油机NOX排放的最有效方法之一。催化剂上游的液滴大小、速度、分散性和均匀性等喷雾参数对NOX转化的有效性有很大影响。对于估计液滴大小，颗粒/液滴图像分析（PDIA）是一种可靠的技术，它有许多优点，包括能够可视化液滴形状和量化非球形液滴。在本研究中，采用高像素分辨率的PDIA和粒子跟踪测速（PTV）技术观察了尿素-水溶液（UWS）喷雾在加热交叉流中的液滴大小和速度。结果表明，较小的球形液滴位于喷雾的顶部，而大多数较大的液滴是非球形的，存在于喷雾的底部。由于雾化效果的改善，液滴尺寸随着喷射压力和空气速度的增加而减小。液滴在气流方向上的速度随气流速度的增大而增大，随粒径的增大而减小。PDIA方法能够同时测量球形液滴和非球形液滴。当在液滴尺寸测量中排除非球形液滴时，测量的SMD存在显着差异，突出了使用一种可以测量此类喷雾中非球形液滴的技术的重要性。然而，由于PDIA方法通常与低重复率相机一起使用，因此必须在一定的成像时间范围内捕获液滴，从它们开始出现在视场中到它们最终消失的时间。

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引用次数: 0

Laser induced cavitation bubble and shockwave measurements with fiber optical hydrophone very close to origin 激光诱导空化泡和冲击波的近源光纤水听器测量

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-30 Epub Date: 2025-11-07 DOI: 10.1016/j.expthermflusci.2025.111655

Ž. Lokar, J. Petelin, D. Horvat, V. Agrež, R. Petkovšek

Laser induced breakdown in water generates shockwaves and cavitation bubble, both originating from the breakdown of the plasma. The dynamics of a shockwave propagating from a point source changes significantly with distance. In spherical geometry without energy loss, the energy spreads out in accordance with the inverse square law, the pressure decreases proportionally with distance. Thus, closer to the shockwave source a more pronounced shockwave dynamics is expected. A fast, robust and precisely positioned sensor with a small detection area is needed to accurately measure the shockwave pressure in such conditions. A single mode optic fiber-based hydrophone meets these requirements. In addition to measuring the shockwave induced change in light reflectance from the fiber tip, the fiber optic hydrophone, when positioned very close to the breakdown bubble, picks up some of the light which exits the sensor and is reflected from the bubble wall. Due to bubble growth, this results in an oscillating interference signal. We introduce signal processing to distinguish between the two signals, originating from different phenomena but captured in a single oscilloscope trace. While using only FFT processing to remove the oscillations from the signal does not preserve the shockwave properties properly, the introduced local filtering procedure allows for correct separation of the two overlapping contributions to the waveform. The transient interference signal allowed for extraction of tens of bubble wall velocity data points in the first 100 ns of a single bubble growth event, showing the very early bubble growth behaviour. After this contribution was eliminated from the signal, the shockwave pressure trace was successfully assessed at very small distances, down to the situation where the hydrophone nearly touched the plasma edge. Pressure trace allowed for extraction of various parameters such as maximum pressure, risetime, shockwave energy and pressure impulse. The shockwave energy was measured to decay as 6.5 dB/mm for distances above 50 μm.

激光在水中的击穿产生冲击波和空化泡，两者都源于等离子体的击穿。从点源传播的冲击波的动力学随距离的变化而显著变化。在无能量损失的球面几何中，能量按平方反比定律扩散，压力随距离成比例减小。因此，在靠近激波源的地方，预期会有更明显的激波动力学。在这种条件下，需要一种快速、坚固、定位精确、检测面积小的传感器来精确测量冲击波压力。单模光纤水听器可以满足这些要求。除了测量来自光纤尖端的冲击波引起的光反射率变化外，当光纤水听器非常靠近破裂气泡时，它还会拾取一些从传感器流出并从气泡壁上反射的光。由于气泡生长，这导致振荡干扰信号。我们引入信号处理来区分两种信号，这两种信号来自不同的现象，但在单个示波器跟踪中被捕获。虽然仅使用FFT处理从信号中去除振荡并不能正确地保留冲击波特性，但引入的局部滤波过程允许正确分离对波形的两个重叠贡献。瞬态干扰信号允许在单个气泡生长事件的前100纳秒内提取数十个气泡壁速度数据点，显示出非常早期的气泡生长行为。从信号中消除这一贡献后，在非常小的距离内成功地评估了冲击波压力轨迹，直到水听器几乎接触等离子体边缘的情况。压力跟踪允许提取各种参数，如最大压力，上升时间，冲击波能量和压力脉冲。在距离大于50 μm时，冲击波能量衰减为6.5 dB/mm。

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引用次数: 0

Experimental investigation of the cooling effectiveness of a leading-edge showerhead configuration with counter-inclined compound holes under the influence of freestream turbulence 自由流湍流影响下反倾斜复合孔前缘花洒冷却效果的实验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-30 Epub Date: 2025-11-07 DOI: 10.1016/j.expthermflusci.2025.111638

Xiyuan Liang , Tong Ye , Xinyu Wang , Lin Ye , Cunliang Liu , Xiying Niu

To enhance the film cooling effectiveness of the leading-edge showerhead on turbine vanes, combined compound angle configurations of film holes were incorporated into the cooling structure design. Pressure-sensitive paint (PSP) technology was used to measure the film cooling effectiveness under various momentum flux ratios ranging from 0.09 to 6.04 and the mainstream turbulence intensity ranging from 2.03 %∼23.58 %. The effects of the momentum flux ratio and mainstream turbulence intensity were compared. The results revealed that the effect of the mainstream turbulence intensity on the film cooling effectiveness at the leading-edge was related to the momentum flux ratio. For the vane leading-edge pressure side, the effect of mainstream turbulence intensity on the film cooling effectiveness was related to the momentum flux ratio. Under a low momentum flux ratio, an increase in mainstream turbulence intensity led to a sharp decline in the film cooling effectiveness, resulting in a maximum reduction of 52.5 % in the area-averaged film cooling effectiveness on the pressure side. When the momentum flux ratio was high, the increased mainstream turbulence intensity enhanced the energy dissipation of the cooling jet, thereby improving the film cooling performance in this region, with a maximum increase of 13.8 % in the film cooling effectiveness. As for the vane leading-edge suction side, the film cooling effectiveness decreases with increasing mainstream turbulence intensity, with a maximum reduction of 36.9 %. Moreover, within the varied range of mainstream turbulence intensities and momentum flux ratios studied in this paper, an increase in the film hole compound angle improved the film cooling effectiveness and relieved the degree of reduction in the film cooling effectiveness caused by the film jet blown off. However, for the pressure side, excessively large film hole compound angle did not significantly improve the film cooling effectiveness. In contrast, to ensure good film cooling characteristics, larger compound-angle film holes can be designed on the vane leading-edge suction side, whereas smaller compound-angle film holes can be created on the vane leading-edge pressure side.

为了提高涡轮叶片前缘淋喷头的气膜冷却效果，在冷却结构设计中采用复合角度的膜孔组合形式。在动量通量比为0.09 ~ 6.04，主流湍流强度为2.03% ~ 23.58%的条件下，采用压敏涂料（PSP）技术测量了气膜冷却效果。比较了动量通量比和主流湍流强度的影响。结果表明，主流湍流强度对前缘气膜冷却效果的影响与动量通量比有关。对于叶片前缘压力侧，主流湍流强度对气膜冷却效果的影响与动量通量比有关。在低动量通量比下，主流湍流强度的增加导致气膜冷却效率急剧下降，压力侧面积平均气膜冷却效率最大下降52.5%。当动量通量比较高时，主流湍流强度的增加增强了冷却射流的能量耗散，从而改善了该区域的气膜冷却性能，气膜冷却效率最大提高了13.8%。叶片前缘吸力侧的气膜冷却效率随着主流湍流强度的增加而降低，最大降幅为36.9%。此外，在本文研究的不同主流湍流强度和动量通量比范围内，增大膜孔复合角提高了膜冷却效率，缓解了被吹出的膜射流导致的膜冷却效率降低的程度。而对于压力侧，过大的膜孔复合角并没有显著提高膜冷却效果。为了保证良好的气膜冷却特性，可以在叶片前缘吸力侧设计较大的复合角膜孔，在叶片前缘压力侧设计较小的复合角膜孔。

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引用次数: 0

Investigation into the bag breakup and sub-droplet size distribution of tandem water droplet pair in an elevated-temperatures continuous airflow 高温连续气流中串联水滴对破袋及亚滴粒径分布的研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-15 Epub Date: 2025-10-04 DOI: 10.1016/j.expthermflusci.2025.111625

Ke Zheng , Yufei Zhu , Zhiwen Gan

Understanding droplet interaction mechanisms in dense sprays requires investigation of tandem droplet pair fragmentation. This investigation uses a high-speed camera to examine the fragmentation phenomena and sub-droplet distribution of tandem water droplet pair with separation distances (S) ranging from 1.9 to 13.3 under airflow temperatures between 293 K and 493 K. The separation distance is the ratio of the actual spacing to the droplet diameter. Within a critical separation distance, the bag breakup of the lead droplet is influenced by collision with the trailing droplet. The critical separation distance for the lead droplet bag breakup decreases with airflow temperature. Separation distance and airflow temperature influence the trailing droplet bag breakup through the collision with the lead droplet, the lead droplet shielding effect, and the airflow velocity dissipation. Further, the sub-droplet size distribution of the broken lead droplet is analyzed by dividing the broken droplet into three parts: bag, rim, and node. The correlation length governing the bag sub-droplet size primarily depends on the bag thickness, while the rim and node sub-droplet sizes depend on the liquid ring thickness. Separation distance and airflow temperature affect the sub-droplet size distributions by altering the volume fractions of the bag, rim, and node, as well as their correlation lengths. A semi-empirical model for predicting the Sauter mean diameter (SMD) of the sub-droplet of the broken lead droplet is proposed based on the volume fractions of different parts (bag, rim, and node) and their correlation lengths. The predictions align well with the experimental data among across a wide range in this investigation. This investigation can provide experimental data and theoretical references for understanding the droplet interaction mechanisms within dense sprays.

了解密集喷雾中液滴的相互作用机制需要对串联液滴对破碎进行研究。利用高速摄像机研究了在293 ~ 493 K气流温度下，分离距离(S)为1.9 ~ 13.3的串联水滴对的破碎现象和亚滴分布。分离距离是实际间距与液滴直径之比。在一定的临界分离距离内，铅滴破袋受尾滴碰撞的影响。铅滴破袋的临界分离距离随气流温度的升高而减小。分离距离和气流温度通过与铅滴的碰撞、铅滴的屏蔽作用和气流速度耗散影响尾滴袋破碎。进一步，通过将破铅液滴分为袋、边缘和节点三部分，分析破铅液滴的子液滴尺寸分布。控制袋状子液滴大小的相关长度主要取决于袋状厚度，而边缘和节点子液滴大小则取决于液环厚度。分离距离和气流温度通过改变袋状、边缘状和结状的体积分数及其相关长度来影响子液滴粒径分布。提出了一种基于不同部位（包、边缘和节点）的体积分数及其相关长度预测破铅液滴子液滴Sauter平均直径（SMD）的半经验模型。这些预测与本研究中广泛范围内的实验数据吻合得很好。该研究可为深入了解致密雾剂中液滴相互作用机理提供实验数据和理论参考。

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引用次数: 0

Dynamic behavior of surface frosting and droplet impact on the frosting superhydrophobic surface 表面结霜的动力学行为及液滴对结霜超疏水表面的影响

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-15 Epub Date: 2025-10-18 DOI: 10.1016/j.expthermflusci.2025.111634

Bin Ding , Ren-tao He , Wen-hao Song , Zhi-qiang Gong , Jie Zhou , Hao Feng

Although superhydrophobic surfaces have the ability to delay the growth of frost crystals, they still cannot completely prevent frosting at low-temperature environments, which in turn affects the dynamic behavior of droplet impacts on frosting surfaces. Here, the frosting behavior of superhydrophobic surfaces and the dynamic behavior of droplet impact on frosting surfaces were explored through visualization experiments. Firstly, the frost formation behavior of hydrophilic and superhydrophobic surfaces under different humidity conditions was investigated, and the influence of surface wettability and relative humidity on the surface frosting characteristics were analyzed. Then, the dynamic behavior of droplet impacts on frosting superhydrophobic surfaces was studied. And the differences in the dynamic behavior of droplet impacts on supercooled surfaces and frosting superhydrophobic surfaces were compared and analyzed. Finally, the influence of impact velocity on the dynamic behavior of droplet impact frosting superhydrophobic surfaces was explored. The results show that an increase in impact velocity would prolong the duration of the spreading stage, and the processes of droplet retraction, rebound and separation are all completely inhibited with the surfaces temperature decreases. The findings provide experimental evidence for revealing the physical mechanism of the interaction between droplets and frosting superhydrophobic surfaces, which is of great significance for promoting the application of superhydrophobic anti-frosting materials in the industrial field.

虽然超疏水表面具有延缓霜晶生长的能力，但仍不能完全防止低温环境下的结霜，从而影响液滴撞击结霜表面的动态行为。通过可视化实验，研究了超疏水表面的结霜行为和液滴撞击结霜表面的动力学行为。首先，研究了不同湿度条件下亲水性和超疏水性表面的结霜行为，分析了表面润湿性和相对湿度对表面结霜特性的影响。然后，研究了液滴在结霜超疏水表面上的动力学行为。对比分析了液滴在过冷表面和结霜超疏水表面上撞击动力学行为的差异。最后，探讨了冲击速度对液滴冲击磨砂超疏水表面动力学行为的影响。结果表明：随着冲击速度的增加，扩散阶段的持续时间延长，液滴的缩回、回弹和分离过程都随着表面温度的降低而被完全抑制；研究结果为揭示液滴与结霜超疏水表面相互作用的物理机制提供了实验依据，对促进超疏水防霜材料在工业领域的应用具有重要意义。

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引用次数: 0

An experimental investigation of transient ice accretion process on a high-lift airfoil model for UAV applications 无人机大升力翼型模型瞬态结冰过程的实验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-15 Epub Date: 2025-09-13 DOI: 10.1016/j.expthermflusci.2025.111612

Manaf Muhammed , Anvesh Dhulipalla , Harsha Sista , Hassan A. Khawaja , Muhammad S. Virk , Hui Hu

An experimental study is performed to investigate the transient ice accretion process along the surface of a high-lift, S1223 airfoil model, and the icing-induced aerodynamic performance degradation. The UAV airfoil model was exposed to typically glaze and rime icing conditions encountered by UAVs flying in low-altitude airspace. While the rime ice accretion was found to conform with the original profile of the UAV airfoil model well in general, substantial “feather-like” ice roughness elements were observed to grow rapidly over both the suction-side and pressure-side surfaces near the airfoil leading edge. The glaze ice accretion process was featured by obvious wind-driven water runback to transport the unfrozen water mass from the airfoil frontal surface to further downstream locations, causing the formation of complex rivulet-shaped ice structures and growth of ice “horns” along the leading edge and “finger-liked icicles” near the trailing edge. The aerodynamic performance of the UAV airfoil was found to degrade continuously with the increasing ice accretion time. The ice accretion over a period of 463 s was found to reduce UAV endurance from 18% to 46 % and diminish the UAV flying range by 13 % to 40 %, depending on the nature of ice accreted. The acquired ice accretion images were coordinated with the aerodynamic force measurements to gain further insight into the underlying physics for a better understanding of the UAV inflight icing phenomena.

通过实验研究了高升力S1223翼型模型表面瞬态结冰过程以及结冰引起的气动性能下降。无人机翼型模型暴露在无人机在低空空域飞行时遇到的典型釉和霜结冰条件下。而时间冰的增加被发现符合无人机翼型模型的原始轮廓很好，在一般情况下，大量的“羽状”冰粗糙度元素被观察到在吸侧和压力侧表面附近翼型前缘迅速增长。釉面结冰过程的特点是明显的风驱动水倒流，将未冻结的水团从翼型前表面输送到更下游的位置，形成复杂的小溪状冰结构，前缘形成冰“角”，后缘附近形成“指状冰柱”。研究发现，随着结冰时间的增加，无人机翼型的气动性能不断下降。在463秒期间的冰的增加被发现减少无人机的续航力从18%到46%并且减少无人机的飞行距离13%到40%，这取决于冰的增加的性质。获取的冰积图像与气动力测量相协调，以进一步了解潜在的物理现象，以便更好地理解无人机飞行结冰现象。

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引用次数: 0

Experimental study on the effects of fuel properties on spray macroscopic characteristics, particle size distribution, and velocity field in a constant volume chamber 定容室中燃料性质对喷雾宏观特性、粒径分布及速度场影响的实验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2026-01-15 Epub Date: 2025-08-27 DOI: 10.1016/j.expthermflusci.2025.111602

Tangsong Guo , Guoxiu Li , Hongmeng Li , Haobo Huo , Xiaoqin Zhang , Zhanguang Wang , Honglin Bai

With the growing energy crisis, clarifying the effects of fuel properties on the engine spray process is one of the critical researches to find new alternative fuels for engines. In this study, the spray macro characteristics, spray particle size distribution, and spray velocity field of various fuels (diesel/biodiesel/coal-to-liquids/aviation kerosene) in a constant volume chamber under different injection pressures and environmental conditions were studied using a spray visualization test platform. The effects of fuel properties such as density, kinematic viscosity, surface tension, and evaporation characteristics on spray parameters, particle size distributions, and velocity distributions were analyzed. The results showed that the physical properties of the fuels under different evaporation conditions affected the spray process to different degrees. The effect of kinematic viscosity was significant under low evaporation conditions. As the kinematic viscosity decreased, the fuel spread more easily, and the fuel spray velocity distribution was more uniform. The effect of fuel volatility on the spray process was enhanced in the presence of significant evaporation. The effects of spray conditions, environmental conditions, and fuel properties on the spray performance were synthesized, and the expression of SMD with respect to the dimensionless parameters We and Re was obtained. With the increase in We and Re, the kinetic energy of the fuel development increased, the jet was more easily broken, and the fuel was better atomized. The experimental analysis results provided in this study illustrate the influence mechanism of fuel physical properties on the fuel spray process, which can provide theoretical support for the improvement of engine fuel adaptability and can also provide ideas for the development of new fuels.

随着能源危机的日益加剧，弄清燃料性质对发动机喷雾过程的影响是寻找新型发动机替代燃料的关键研究之一。本研究利用喷雾可视化测试平台，研究了不同喷射压力和环境条件下，不同燃料（柴油/生物柴油/煤制油/航空煤油）在定容室内的喷雾宏观特性、喷雾粒径分布和喷雾速度场。分析了燃料的密度、运动粘度、表面张力和蒸发特性对喷雾参数、粒径分布和速度分布的影响。结果表明，不同蒸发条件下燃料的物理性质对喷雾过程有不同程度的影响。在低蒸发条件下，运动粘度的影响是显著的。运动粘度越小，燃油越容易扩散，燃油喷射速度分布越均匀。燃油挥发性对喷雾过程的影响在显著蒸发的情况下得到增强。综合了喷雾条件、环境条件和燃料性能对喷雾性能的影响，得到了SMD与无因次参数We和Re的表达式。随着We和Re的增加，燃料发展的动能增加，射流更容易破碎，燃料的雾化效果更好。本研究提供的实验分析结果阐明了燃油物理性质对燃油喷射过程的影响机理，可为提高发动机燃油适应性提供理论支持，也可为新燃料的开发提供思路。

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引用次数: 0