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Simultaneous measurement of velocity field of liquid–solid particle flow in pipelines and analysis of flow characteristics 同时测量管道中液固颗粒流动的速度场并分析流动特性
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-11 DOI: 10.1016/j.expthermflusci.2024.111268

The liquid–solid particle flow within a horizontal pipeline is a typical particle-laden flow. The interplay between loaded particles and carrier phase engenders significant complexities in the dynamic behavior of such flows. We investigated the dynamics of a liquid–solid particle flow featuring dilute, slightly buoyant, hundred-micron-sized spherical particles fully suspended in the turbulent flow in a pipe, where Re is 7038. Cases with solid volume fractions of 0, 2.67 × 10-4, 5.33 × 10-4, 8.00 × 10-4, 1.07 × 10-3 and 1.33 × 10-3 were considered in this study. Experimental measurement techniques were utilized to acquire images of particles in the two-phase flow across the entire flow field via optical field feedback. Particle image velocimetry (PIV) and particle tracking velocimetry (PTV) were employed to simultaneously obtain liquid-phase velocity fields and particle trajectories. This approach allowed for a comprehensive depiction of the velocity field of each phase. Subsequently, a detailed explanation and analysis of the flow characteristics of the liquid–solid particle flow were provided based on the distribution of macroscopic velocity fields, the microscopic vorticity field, particle velocity vectors, and velocity slip. As a result, it was found that with the addition of solid particles and an increase in volume concentration, the drag effect of the solid phase and the trend of accumulation near the lower wall caused a decrease in the liquid phase velocity profile and deformation of the parabolic shape. In the liquid–solid particle flow with a volume concentration of 1.33 × 10-3, compared to the single-liquid phase flow, the standard deviation of velocity in the central region increased from 0.0097 m/s to 0.0159 m/s, and in the near-wall region, it increased from 0.0257 m/s to 0.0347 m/s, representing increases of 1.54 times and 1.26 times respectively. The proportion of medium vortices increased from 17 % to 30 %, nearly doubling. This study actively explores the concurrent measurement and flow characteristics of liquid–solid particle flow.

水平管道内的液固颗粒流是一种典型的颗粒负载流。负载颗粒与载相之间的相互作用导致此类流动的动态行为非常复杂。我们研究了一种液固粒子流的动力学特性,即稀释、微浮力、百微米大小的球形粒子完全悬浮在管道内的湍流中,Re 为 7038。本研究考虑了固体体积分数为 0、2.67 × 10-4、5.33 × 10-4、8.00 × 10-4、1.07 × 10-3 和 1.33 × 10-3 的情况。利用实验测量技术,通过光场反馈获取两相流中颗粒在整个流场中的图像。粒子图像测速仪(PIV)和粒子跟踪测速仪(PTV)被用来同时获得液相速度场和粒子轨迹。这种方法可以全面描述各相的速度场。随后,根据宏观速度场、微观涡度场、粒子速度矢量和速度滑移的分布,详细解释和分析了液固粒子流的流动特性。结果发现,随着固体颗粒的加入和体积浓度的增加,固相的阻力效应和在下壁附近的堆积趋势导致液相速度剖面下降和抛物线形状变形。在体积浓度为 1.33 × 10-3 的液固颗粒流中,与单液相流相比,中心区域的速度标准偏差从 0.0097 m/s 增加到 0.0159 m/s,近壁区域的速度标准偏差从 0.0257 m/s 增加到 0.0347 m/s,分别增加了 1.54 倍和 1.26 倍。介质涡的比例从 17% 增加到 30%,几乎翻了一番。这项研究积极探索了液固颗粒流动的同步测量和流动特性。
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引用次数: 0
Experimental investigation on seeping gas film effectiveness in supersonic flow downstream of a porous injector 多孔喷射器下游超音速气流中渗出气膜有效性的实验研究
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-11 DOI: 10.1016/j.expthermflusci.2024.111267

Based on seepage flow through porous media, the seeping gas film cooling method is an effective means to protect large areas of optical windows and other hot components of hypersonic vehicles. Here, the pressure-sensitive paint (PSP) technique was applied and experiments were conducted on seeping gas film effectiveness downstream of a porous injector. A Mach 3 wind tunnel was used to explore the influence of different cooling gas blowing ratios, gas types, and incoming boundary-layer conditions on film effectiveness. Results show film effectiveness decreases monotonically along the downstream wall; however, with blowing ratio increases the film effectiveness increases linearly. Once the blowing ratio exceeds 0.4% film effectiveness ascends nonlinearly, indicating that the contribution to film effectiveness per unit mass flow-rate promotion gradually decreases. In contrast, the non-uniformity of the film coverage on the downstream wall in the spanwise direction becomes more significant at a higher blowing ratio. For the same blowing ratio, helium, with a low molecular weight has a higher film effectiveness compared to nitrogen and carbon dioxide. With blowing ratio less than 0.4 %, the film effectiveness downstream of the porous injector under laminar flow conditions is almost twice that of turbulent flow. However, with blowing ratio above 0.5 %, the growth rate of the film effectiveness decreases dramatically to 50 %. Preliminary analysis suggests that this is caused by the complete transition of the laminar boundary layer to turbulent flow after passing through the porous wall under high blowing ratios, where the mixing effect of turbulence is fully manifest.

基于多孔介质的渗流,渗流气膜冷却方法是保护高超音速飞行器大面积光学窗口和其他热部件的有效手段。本文应用压敏涂料(PSP)技术,对多孔喷射器下游的渗流气膜效果进行了实验。实验采用马赫数为 3 的风洞,探讨了不同冷却气体吹气比、气体类型和进入边界层条件对薄膜效果的影响。结果表明,薄膜效果沿下游壁单调递减;然而,随着吹气比的增加,薄膜效果呈线性增长。当吹气比超过 0.4% 时,薄膜效率呈非线性上升,这表明单位质量流量对薄膜效率的贡献逐渐降低。相反,当吹气比越大时,下游壁上薄膜在跨度方向上覆盖的不均匀性就越明显。在相同的吹气比下,与氮气和二氧化碳相比,低分子量的氦气具有更高的薄膜效率。当吹气比小于 0.4 % 时,层流条件下多孔喷射器下游的膜效率几乎是紊流条件下的两倍。然而,当吹气比高于 0.5 % 时,薄膜效率的增长率急剧下降至 50 %。初步分析表明,这是由于在高吹气比条件下,层流边界层穿过多孔壁后完全过渡到湍流,湍流的混合效应在此得到充分体现。
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引用次数: 0
Air injector geometry affects passive bubble acoustic signatures 空气喷射器的几何形状会影响被动气泡声学特征
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-09 DOI: 10.1016/j.expthermflusci.2024.111265
A. Vazquez , R.M. Del Castillo , R. Manasseh , B. Roche

Understanding the passive acoustic signals of gas bubbles has become increasingly imporant due to their growing relevance in ambient marine acoustics and medical areas, as well as the recent search for dark matter by Bubble Chamber Detectors. Here the acoustic signatures of 2.24, 1.83, 1.75, 1.66 and 1.43 mm radii bubbles are reported experimentaly. They were generated by two different air injectors in a quiescent liquid, a standard plastic syringe tube and 97 degrees-rotated metallic needles. The evolution of the sound pulse over time is presented alongside simultaneous images of the bubbles detaching from the injector and moving freely in the liquid. The beat-wave phenomenon is the standard interference pattern between two sounds of slightly different frequencies, generating a beat-period envelope of “rosary chain” form. In this study, beats are observed when the bubble exhibits changes in its shape through Cassini-oval, trapezoid, ‘guitar pick’, ellipsoid and oblate shapes, which is in agreement with earlier results on bubble fragmentation in a locally sheared flow. Finally, theoretical curve fits of freely-oscillating, lightly-damped bubble sound emissions confirm that the beats are due to changes in the bubble shapes.

了解气泡的被动声学信号变得越来越重要,这是因为气泡在环境海洋声学和医学领域的相关性越来越大,而且最近气泡腔探测器也在寻找暗物质。这里报告的是 2.24、1.83、1.75、1.66 和 1.43 毫米半径气泡的声学特征。它们是由静态液体中的两种不同空气注入器、标准塑料注射管和旋转 97 度的金属针头产生的。声脉冲随时间的演变与气泡脱离喷射器并在液体中自由移动的同步图像同时呈现。节拍波现象是频率略有不同的两种声音之间的标准干涉模式,产生 "念珠链 "形式的节拍周期包络。在这项研究中,当气泡的形状发生变化时,就会出现节拍,包括卡西尼椭圆形、梯形、"吉他拨片 "形、椭圆形和扁球形,这与早先关于局部剪切流中气泡破碎的研究结果一致。最后,对自由振荡的轻阻尼气泡声发射进行的理论曲线拟合证实,节拍是由气泡形状的变化引起的。
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引用次数: 0
Comparative experimental study of the effect of loading rate on the typical mechanical properties of bubble and clear ice cubes 加载速率对气泡冰块和透明冰块典型机械特性影响的对比实验研究
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-06 DOI: 10.1016/j.expthermflusci.2024.111264

Icing is a common liquid–solid phase change process that usually has negative effects. Bubbles will form in ice since air is significantly less soluble in ice than it is in water and these bubbles will affect the mechanical properties of ice cubes. To quantitatively investigate the effect of air bubbles on the mechanical strength of ice cubes, an experimental setup is built to explore the mechanical strength and modulus of clear and bubble ice cubes at different loading rates. The results show that even a low volume fraction of air bubbles in the ice cubes as low as 1.98% can have a significant effect on their mechanical properties. The weakening of tensile, compressive and bending strengths by air bubbles is almost less than 20%, while the weakening of shear strength by air bubbles reaches almost 60%. The effect of air bubbles on the four typical mechanical moduli does not exceed 20%. This research helps to optimize the de-icing technique and also provides methods and ideas for preparing ice.

结冰是一种常见的液固相变过程,通常会产生负面影响。由于空气在冰中的溶解度明显低于在水中的溶解度,因此冰中会形成气泡,这些气泡会影响冰块的机械性能。为了定量研究气泡对冰块机械强度的影响,我们建立了一个实验装置,探索不同加载速率下透明冰块和气泡冰块的机械强度和模量。结果表明,即使冰块中气泡的体积分数低至 1.98%,也会对其机械性能产生显著影响。气泡对拉伸、压缩和弯曲强度的削弱几乎小于 20%,而气泡对剪切强度的削弱几乎达到 60%。气泡对四种典型机械模量的影响不超过 20%。这项研究有助于优化除冰技术,也为制冰提供了方法和思路。
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引用次数: 0
Boiling induced atomization of liquid film produced by oblique jet impingement on superheated wall 倾斜射流撞击过热壁产生的沸腾诱导液膜雾化
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-05 DOI: 10.1016/j.expthermflusci.2024.111262
Noritaka Sako , Jun Hayashi , Chihiro Inoue , Hiroshi Kawanabe , Yu Daimon

For the thermal management of industrial devices, a reduction in the net coolant flow rate by droplet dispersion from a liquid film is important because it can cause unexpected thermal failure. To understand the process of droplet dispersion from a liquid film better, we experimentally and theoretically evaluated the characteristics of boiling-induced atomization in a liquid film formed by oblique jet impingement on a superheated wall. Atomization processes were visualized using magnified high-speed imaging using a backlight technique. In this study, two types of droplets were observed using high-speed-magnification imaging. These were large droplets that disintegrated from the ligament formed on a relatively high-temperature wall, and small droplets from the ligament formed via bubble bursting in the nucleate boiling regime. For the atomization induced by nucleate boiling, larger droplets were produced via bubble bursting further downstream from the impingement point because the bubble size and liquid film thickness increased. Finally, the total volume of the droplets produced by nucleate boiling was estimated from the frequency of bubble bursting and droplet size measured from the visualization results. The estimation results suggest that the ratio of the total volume flow rate of the ejected droplets to the injection flow rate of the liquid was negligible (2%). Thus, most of the injected liquid eventually reached the wetting front of the sheet, separating it from the wall before drying out.

对于工业设备的热管理而言,液膜液滴分散导致的净冷却剂流速降低非常重要,因为它可能导致意想不到的热故障。为了更好地理解液膜的液滴分散过程,我们通过实验和理论评估了沸腾诱导雾化在液膜中的特性,液膜是由斜向射流撞击过热壁形成的。雾化过程是通过使用背光技术的放大高速成像进行可视化的。在这项研究中,利用高速放大成像技术观察到了两种液滴。它们是在相对高温的壁面上形成的韧带瓦解的大液滴,以及在成核沸腾状态下通过气泡破裂形成的韧带小液滴。对于由成核沸腾引起的雾化,由于气泡尺寸和液膜厚度增加,在撞击点下游通过气泡破裂产生了更大的液滴。最后,根据气泡破裂的频率和可视化结果测得的液滴大小,估算了成核沸腾产生的液滴的总体积。估算结果表明,喷射液滴的总体积流量与液体喷射流量之比可以忽略不计(2%)。因此,大部分注入的液体最终到达了薄片的润湿前沿,在干燥之前将薄片与壁分离。
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引用次数: 0
Analysis of stability and internal flow mechanisms in spiral annular flow with different swirlers 带不同漩涡的螺旋环形流的稳定性和内部流动机制分析
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-04 DOI: 10.1016/j.expthermflusci.2024.111263
Haoyu Wang, Yang Yang, Bin Yang, Yu Tang, Wenjie Jing

Spiral annular flow within ducts is widely utilized in modern industry, with the swirler serving as a critical component in generating such flow patterns. The structure of the swirler significantly influences the generation and stability of the spiral annular flow. This study selected four different swirler structures with outstanding performance from previous research and analyzed their characteristics through visual image processing combined with numerical simulations. By analyzing the amplitude information of the wave fluctuations in the annular swirling flow liquid film under different operating conditions using probability density functions, it was found that the swirler A(Flat-vane swirler) and swirler B(Flat-vane swirler with hub) produced smaller fluctuations in the annular swirling flow liquid film, indicating better stability compared to the swirler C(Arc-vane swirler) and swirler D(Spiral-vane swirler), which exhibited poor performance. Combining the numerical simulation results with the analysis of the internal mechanism of the swirlers, it was discovered that within the swirler A and swirler B, the fluid between the swirler vanes experienced a larger pressure gradient, resulting in phenomena such as “jump” and “pull” under this pressure gradient. This, in turn, contributed to the generation of greater tangential velocity and radial pressure gradient after the fluid exited the swirler. Due to the influence of the swirler structure, the swirler A and swirler B did not completely separate the fluid region into four independent spaces. Instead, in the central connection area of the rear section of the swirler, the gas phase components aggregated earlier, greatly promoting the downstream generation of spiral annular flow. This study analyzed the two-phase flow process and mechanism inside the swirler, filling a gap in previous research and providing important references for the optimization and selection of swirlers.

现代工业中广泛使用管道内的螺旋环形流,漩涡器是产生这种流动模式的关键部件。漩涡器的结构对螺旋环形流的产生和稳定性有很大影响。本研究从以往的研究中选取了四种性能优异的不同漩涡结构,并通过视觉图像处理和数值模拟对其特性进行了分析。通过使用概率密度函数分析不同工况下环形漩涡流液膜的波幅信息,发现漩涡器 A(平叶片漩涡器)和漩涡器 B(带轮毂的平叶片漩涡器)在环形漩涡流液膜中产生的波动较小,与性能较差的漩涡器 C(弧叶片漩涡器)和漩涡器 D(螺旋叶片漩涡器)相比,稳定性更好。结合数值模拟结果和对漩涡器内部机理的分析,发现在漩涡器 A 和漩涡器 B 中,漩涡器叶片之间的流体经历了较大的压力梯度,在此压力梯度下产生了 "跳跃 "和 "拉动 "等现象。这反过来又促使流体在离开漩涡器后产生更大的切向速度和径向压力梯度。由于漩涡器结构的影响,漩涡器 A 和漩涡器 B 并没有将流体区域完全分离成四个独立的空间。相反,在漩涡器后部的中央连接区域,气相成分聚集较早,极大地促进了螺旋环形流的下游生成。该研究分析了漩涡器内部的两相流动过程和机理,填补了以往研究的空白,为漩涡器的优化和选型提供了重要参考。
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引用次数: 0
Effect of inlet flow turbulence on hydro–acoustic coupling and flame–vortex interactions in a premixed dump combustor 进气湍流对预混合倾卸式燃烧器中水声耦合和火焰涡流相互作用的影响
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-04 DOI: 10.1016/j.expthermflusci.2024.111260
Pankaj Pancharia, Vikram Ramanan, S.R. Chakravarthy

The present work examines the effect of inlet flow turbulence on the flame–vortex modulations, hydro–acoustic coupling and recirculation zone dynamics at the onset of instability. The flow turbulence intensity varied using a custom-designed turbulence generator with different slot-width blockage plates placed upstream to the nominal flame-stabilization zone. The high-speed recordings of the CH*/OH* chemiluminescence and particle image velocimetry are used to deduce the relation between the flame–acoustic, flame–vortex and hydrodynamic–acoustic features during the unsteady combustion. The bifurcation analysis map revealed the effect of high inlet flow turbulence on postponing the onset of instability to higher inlet flow parameters. The initial observations showed potential changes in the acoustic behaviour and dynamical state of premixed turbulent combustion with an increase in inlet flow turbulence. The spatial Rayleigh index map illustrates a significant change in the acoustic driving region at high inlet flow turbulence based on the flame stabilization, heat release zone and flame–acoustic modulation in the shear layer and recirculation zone. The velocity spectral analysis and dynamic mode decomposition (DMD) spectrum suggested a correlation between the acoustic modulation and hydrodynamic instabilities, resulting in higher heat release rate oscillations. The high inlet flow turbulence modulates the vertical flapping motion of the flame front and flame roll-up in the recirculation region as evident by DMD spectrum and spatial modes. The flame–vortex dynamics during the dynamic transition events showed that the high inlet flow turbulence influenced the vortex shedding along the shear layer and recirculation zone dynamics. At low turbulence intensity, the vortex, in turn, supports the bulk flame movement through the induced velocity, which interacts with the free stream to create regions of low velocity. In contrast, the vortex in the shear layer and flame resides along the shear layer at higher turbulence. The paper concludes that at higher inlet flow turbulence, the recirculating flame reduces the hydro–acoustically modulated flow velocity fluctuations, which significantly affect the upstream flame propagation propensity.

本研究探讨了入口湍流对火焰涡旋调制、水声耦合和不稳定开始时再循环区动力学的影响。使用定制设计的湍流发生器,在名义火焰稳定区上游放置不同槽宽的阻挡板,以改变流动湍流强度。利用高速记录的 CH*/OH* 化学发光和粒子图像测速仪来推断非稳定燃烧过程中火焰-声学、火焰-漩涡和流体动力-声学特征之间的关系。分岔分析图显示了高入口流湍流对将不稳定性推迟到更高入口流参数的影响。初步观测结果表明,随着进气流湍流的增加,预混湍流燃烧的声学行为和动力学状态可能会发生变化。空间瑞利指数图显示,在火焰稳定区、热释放区以及剪切层和再循环区的火焰声学调制的基础上,高入口流湍流的声学驱动区发生了显著变化。速度频谱分析和动态模式分解(DMD)频谱表明,声学调制与流体力学不稳定性之间存在相关性,从而导致较高的热释放率振荡。从 DMD 频谱和空间模式可以看出,高进气湍流调节了火焰前沿的垂直拍动运动和再循环区域的火焰翻滚。动态过渡事件期间的火焰涡旋动力学表明,高进气湍流影响了沿剪切层的涡旋脱落和再循环区动力学。在低湍流强度下,漩涡反过来通过诱导速度支持体火焰运动,诱导速度与自由流相互作用产生低速区域。相反,在湍流强度较高时,剪切层中的漩涡和火焰沿剪切层驻留。本文的结论是,在较高的进气湍流度下,再循环火焰会降低水声调制的流速波动,从而显著影响上游火焰的传播倾向。
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引用次数: 0
Flow periodicity in microchannels with fin arrays: Experimental validation 带鳍阵列微通道中的流动周期性:实验验证
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-07-03 DOI: 10.1016/j.expthermflusci.2024.111261
Pinar Eneren, Arthur Vangeffelen, Yunus Tansu Aksoy, Maria Rosaria Vetrano

Investigation of the hydrodynamics within microfluidic chips is crucial for cutting-edge integrated liquid cooling systems due to the coupling between the temperature and velocity fields. Therefore, in this experimental work, we examine the spatial periodicity of the laminar velocity fields and pressure drops inside offset strip fin (OSF) and square pin fin (SPF) arrays at Reynolds numbers between 50 and 292 under isothermal conditions. The velocity fields are characterized using the μPIV technique, and an advanced image stitching algorithm is applied to obtain the streamwise velocity fields. These stitched velocity fields serve two key purposes: evaluation of the flow development length and validation of the flow periodicity due to the periodic nature of the fin arrays. The velocity measurements are compared to the DNS results, and the friction factors acquired from pressure drop measurements are accurately predicted by the correlations based on the periodic flow assumption owing to the rapid flow development. For the first time, to the authors’ knowledge, the consistent monotonic decay of flow perturbations is experimentally evidenced to occur via a single exponential mode. Finally, based on our validation, we confirm the feasibility of using the unit-cell approach to significantly reduce the computational costs compared to simulations that resolve the entire geometry.

由于温度场和速度场之间的耦合关系,研究微流控芯片内的流体力学对于尖端集成液体冷却系统至关重要。因此,在本实验中,我们研究了在等温条件下,雷诺数介于 50 和 292 之间时,偏置条形鳍片(OSF)和方形针形鳍片(SPF)阵列内层流速度场和压降的空间周期性。采用 μPIV 技术对速度场进行表征,并应用先进的图像拼接算法获得流向速度场。这些拼接的速度场有两个主要用途:评估流动发展长度和验证鳍片阵列的周期性所导致的流动周期性。速度测量结果与 DNS 结果进行了比较,由于流动发展迅速,基于周期性流动假设的相关性可以准确预测通过压力降测量获得的摩擦系数。据作者所知,这是第一次通过实验证明流动扰动的单调衰减是通过单一指数模式发生的。最后,基于我们的验证,我们证实了使用单元单元方法的可行性,与解析整个几何形状的模拟相比,单元单元方法可显著降低计算成本。
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引用次数: 0
Comprehensive study on collision patterns of viscous droplets impacting on a heated particle 粘性液滴撞击受热颗粒的碰撞模式综合研究
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-06-28 DOI: 10.1016/j.expthermflusci.2024.111259
Zhiheng Fan, Daoyin Liu, Cai Liang, Xiaoping Chen

The collision process involving droplets and heated particles has gained significant attention due to its wide industrial relevance. This study utilizes a high-speed photography to investigate the collision dynamics between viscous droplets and heated particles. The research identifies six distinct collision patterns. In the bubble-breakup mode, the particle experiences the greatest temperature drop, resulting in the most substantial heat transfer. The particle temperature plays a crucial role in determining collision behavior when the Reynolds number exceeds 100 and the Weber number exceeds 55. The maximum spreading area demonstrates a linear relationship with the Weber number, while it reaches a peak and stabilizes with Reynolds numbers in the deposition regime. Contact angle fluctuations are caused by the instability of the contact line. The liquid film thickness exhibits linear and power growth phases, followed by a rapid decrease in the bubble-breakup regime. While the branch-breakup pattern sees smaller fragmented droplet sizes, the atomization-breakup pattern sees flow velocity rise with both Reynolds and Weber numbers. The predicted wavelength of the disturbance in the atomization regime, based on Rayleigh-Taylor instability theory, aligns well with the experimental measurements. The residence time correlates positively with the Weber number.

液滴与加热颗粒的碰撞过程因其广泛的工业相关性而备受关注。本研究利用高速摄影来研究粘性液滴与加热颗粒之间的碰撞动力学。研究发现了六种不同的碰撞模式。在气泡破裂模式中,颗粒经历的温度下降最大,导致的热量传递也最多。当雷诺数超过 100 和韦伯数超过 55 时,颗粒温度对碰撞行为起着至关重要的作用。最大铺展面积与韦伯数呈线性关系,而在沉积模式下,随着雷诺数的增加,最大铺展面积达到峰值并趋于稳定。接触角波动是由接触线的不稳定性引起的。液膜厚度呈现线性和功率增长阶段,随后在气泡破裂状态下迅速下降。在分支破裂模式中,破碎液滴的尺寸较小,而在雾化破裂模式中,流速随着雷诺数和韦伯数的增加而上升。根据雷利-泰勒不稳定性理论预测的雾化状态下的扰动波长与实验测量结果非常吻合。停留时间与韦伯数呈正相关。
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引用次数: 0
Child droplet compositions produced by puffing and micro-explosion of two-liquid parent droplets 双液母液滴的膨化和微爆产生的子液滴成分
IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Pub Date : 2024-06-26 DOI: 10.1016/j.expthermflusci.2024.111258
D.V. Antonov, R.M. Fedorenko, P.A. Strizhak

The paper presents the experimental research findings on the compositions of child droplets produced by puffing and micro-explosion of parent two-liquid droplets. The droplets under study consisted of water and rapeseed oil. The research was carried out with varying concentrations of liquids in droplets, ambient temperatures, heating arrangements and initial sizes of two-liquid droplets. Parent droplets were heated in a flame, in a muffle furnace, and on a heated substrate. Child droplet compositions were identified using Laser Induced Fluorescence. Compositions were separated based on the difference in the fluorescence of liquids in child droplets exposed to laser radiation. Typical distributions of child droplets by size were obtained for water and rapeseed oil during parent droplet fragmentation when there was a group of contributing factors. The child droplet sizes were measured for water and rapeseed oil. Laser Induced Fluorescence was successfully used to identify different liquids in child droplets following the micro-explosive fragmentation of two-liquid droplets. The experimental data were processed to establish functional relationships between the main factors, parameters and integral characteristics of the investigated processes. Dimensionless criterion relationships and mathematical expressions were proposed for transferring the experimental results to different scales and conditions for heating two-liquid droplets. The applicability of this approach was described. Guidelines were provided on developing the proposed approach for heterogeneous compositions of parent droplets.

本文介绍了对双液母液滴通过膨化和微爆产生的子液滴成分的实验研究结果。所研究的液滴由水和菜籽油组成。研究是在液滴中液体浓度、环境温度、加热方式和双液液滴初始大小各不相同的情况下进行的。母液滴在火焰中、马弗炉中和加热基底上加热。使用激光诱导荧光鉴定子液滴成分。根据子液滴中液体在激光辐射下的荧光差异来分离成分。在母液滴破碎过程中,当存在一组促成因素时,水和菜籽油的子液滴按大小的典型分布情况。测量了水和菜籽油的子液滴尺寸。激光诱导荧光成功地用于识别双液液滴微爆破碎后子液滴中的不同液体。对实验数据进行了处理,以建立所研究过程的主要因素、参数和整体特征之间的函数关系。提出了无量纲标准关系和数学表达式,以便将实验结果转移到不同尺度和条件下的双液滴加热过程中。介绍了这种方法的适用性。为开发适用于母液液滴异质成分的拟议方法提供了指导。
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Experimental Thermal and Fluid Science
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