Article
Optics
X. I. N. H. A. O. Wang, Y. I. N. G. C. H. U. N. Wu, D. O. N. G. Y. A. N. Xu, B. O. T. O. N. G. Wen, Q. I. M. E. N. G. Lv, X. U. E. C. H. E. N. G. Wu
Summary: This work proposes a synthetic aperture rainbow refractometry (SARR) by synthesizing rainbow signals of the same droplet with dual-wavelength laser beams to increase the aperture of rainbow refractometry. The feasibility and accuracy of SARR are successfully demonstrated for measuring droplet refractive index and size.
Article
Optics
Can Li, Wenmin Peng, Yang Kang, Xudong Fan, Xiaolong Huang, Ning Li, Chunsheng Weng, Cameron Tropea
Summary: Rainbow refractometry has been developed for spray measurement applications, allowing simultaneous measurement of refractive index and droplet size. This study investigates the feasibility and accuracy of using incomplete rainbow signals for measurement. The newly defined dimensionless signal partial ratio (SPR) quantifies the degree of incompleteness. Simulation and inversion experiments were conducted, and the results showed that inversion using signal fitting is more accurate than using specific characteristic points. Laboratory experiments also verified these findings. For SPR <= 1, rainbow refractometry achieves errors within 6 x 10-4, 3% for monodisperse droplets and 2 x 10-4, 8% for spray droplets in terms of refractive index and size.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Engineering, Chemical
Yingchun Wu, Qimeng Lv, Xuecheng Wu, Xinhao Wang, Linghong Chen, Kefa Cen
Summary: The oscillation of micron-sized liquid droplets can be measured using time-resolved rainbow refractometry to determine surface tension and viscosity. The method shows potential for improving experimental validation and reducing measurement errors, with relative errors of less than 5% for surface tension and 10% for viscosity.
Article
Optics
Qimeng Lv, Yingchun Wu, Xuecheng Wu
Summary: Rainbow refractometry is used to measure the temperature and size of transparent spherical particles. However, there are limitations in its application when heating and cooling droplets, as the measured temperature is not the average, surface, or core temperature of the droplet. This study exploits the technique to determine the surface temperature of droplets by measuring the surface tension through detecting the evolution of interference fringes. The relationship between surface tension and temperature enables the study of the surface temperature of evaporating droplets over time. The capabilities and limitations of rainbow refractometry are verified by comparing the directly measured droplet temperature values with the surface temperature.
Article
Mathematics, Applied
Zhongmei Qin, Shasha Li, Yongxin Lan, Jun Yue
Summary: This paper focuses on rainbow numbers of paths in plane triangulations, providing improvements and accurate values or bounds of the results, as well as discussing upper and lower bounds of rainbow numbers for wheel graphs and paths.
APPLIED MATHEMATICS AND COMPUTATION
(2021)
Article
Optics
Wenmin Peng, Can Li, Tianchi Li, Linbin Huang, Ning Li, Chunsheng Weng
Summary: This study simulated and experimentally evaluated the effect of signal noise on the inversion accuracy of global rainbow signals of droplets with different size distributions. It used a local minimum-based algorithm for parameter retrieval and empirical mode decomposition for denoising. The results showed that the inversion algorithm had the highest accuracy for noise-free signals, while the empirical mode decomposition effectively reduced the errors of droplet size and refractive index even under low signal-to-noise ratios. The experimental results further confirmed the feasibility and effectiveness of the proposed processing procedures.
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
(2023)
Article
Thermodynamics
Qimeng Lv, Yingchun Wu, Xinhao Wang, Lei Zeng, Xuecheng Wu
Summary: This study experimentally investigates the evaporation characteristics of fuel droplets under the combined effects of ambient pressure, temperature, droplet size, and spacing. The results show that the evaporation rate of droplets is influenced by both ambient conditions and droplet interactions. Furthermore, the study reveals the correlations between Nusselt and Sherwood numbers through parametric analysis.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
Zhaojing Ni, Camille Hespel, Kai Han, Fabrice Foucher
Summary: The evaporation behavior of binary droplets consisting of ethanol and heptane was studied experimentally and through simulation. The study found that the heavier component preferentially evaporates when the lighter component dominates the liquid mixture. The refractive index of the droplets is influenced by temperature and composition, and a linear relationship between the refractive index gradient and the deviations from the center refractive index was proposed. The accuracy of a non-ideal equilibrium model for predicting the diameter, temperature, and concentration of binary droplets was validated for the first time.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2022)
Article
Engineering, Chemical
Can Li, Qimeng Lv, Ning Li, Yingchun Wu, Xuecheng Wu, Chunsheng Weng, Cameron Tropea
Summary: There is significant interest and demand for the multi-parameter characterization of colloidal droplets. However, optical in-situ characterization of such droplets poses a challenge due to their heterogeneous and multi-scale nature. This study proposes an analytical model for dual-wavelength extinction rainbow refractometry, which allows for the simultaneous measurement of inclusion concentration, particle size, refractive index, and droplet diameter. Validation experiments demonstrate the effectiveness of this method, and the measurement errors and limitations are analyzed.
Article
Engineering, Chemical
Yingchun Wu, Xinhao Wang, Dongyan Xu, Xuecheng Wu
Summary: Synthetic aperture rainbow refractometry (SARR) is a method proposed for characterizing the optical properties of droplets and sprays at a long stand-off distance. It utilizes multiple crossing laser beams and color imaging to synthesize rainbow signals and enlarge the aperture of the imaging system. The method has been validated with simulations and experiments, and shows great potential for large scale industrial applications.
Article
Physics, Multidisciplinary
Can Li, Wenmin Peng, Tianchi Li, Ning Li
Summary: This study investigates the feasibility and accuracy of rainbow refractometry using the incomplete rainbow signal on the right side. Through comprehensive analysis and simulations, the study explores the utilization of refractive index, droplet diameter, and size distributions retrieved from partial rainbow signals. Laboratory experiments confirm the effectiveness of employing right partial rainbow signals in rainbow refractometry.
FRONTIERS IN PHYSICS
(2023)
Article
Mathematics, Applied
Zemin Jin, Huawei Ma, Rui Yu
Summary: In this paper, we investigate the existence of rainbow matchings in maximal bipartite planar graphs. We determine the maximum number of colors that can appear in an edge-coloring of maximal bipartite planar graphs with a Hamilton cycle that does not contain any rainbow k-matching. The bounds provided are optimal.
APPLIED MATHEMATICS AND COMPUTATION
(2022)
Article
Optics
M. F. B. Stodt, T. Wriedt, J. Kiefer, U. Fritsching
Summary: This study investigates the application of global rainbow refractometry to sprays with droplets as small as 1 - 30 µm in diameter, evaluating the influence of varying droplet size distributions and refractive indexes on the global rainbow. The results suggest that GRR experiments in polydisperse applications should be accompanied with an accurate sizing technique.
JOURNAL OF MODERN OPTICS
(2021)
Article
Chemistry, Physical
Melisa Nyakuchena, Cory Juntunen, Peter Shea, Yongjin Sung
Summary: The refractive index is a significant optical property for measuring light scattering and label-free imaging, and various methods have been developed to characterize different sample types. This paper demonstrates a technique using synthetic phase microscopy (SPM) and least-squares fitting to measure the refractive index of homogeneous microspheres and liquids in the short-wave infrared range. The method was applied to determine the refractive index dispersion of different polymer and glass microspheres, as well as microscopy mounting media in the SWIR range of 1100-1650 nm.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Applied
Almas Mukhametov, Laura Mamayeva, Assemay Kazhymurat, Togzhan Akhlan, Moldir Yerbulekova
Summary: The aim of this study was to compare vegetable oils and their two-component blends using infrared spectroscopy and refractometry. The research was conducted in Almaty, Kazakhstan in 2020. A total of 44 samples of vegetable oils and their blends were examined. The properties of the blended vegetable oils were investigated using refractometry and infrared spectroscopy, and parameters such as fatty acid fraction, iodine number, and index of refraction were calculated. The spectrograms of the blends were analyzed, and it was found that the intensity difference of weak bands and the band expansion at 722 cm-1 indicated greater expressiveness. The level of unsaturated fatty acids increased in the blend when low-intensity bands (1653 cm-1) became more distinct due to vibrations of double carbon bonds (C-bonds).
Article
Engineering, Environmental
L. M. Reitter, H. Lohmann, M. Schremb, I. Roisman, J. Hussong, C. Tropea
Summary: Ice particle impact causes deformation and fragmentation, leading to the formation of a residual ice cone. High-speed video system is used to observe the impact, deformation, and fragmentation of nearly spherical ice particles, as well as measuring the size and mass of the residual ice cone. A theoretical model based on fluid dynamics is used to estimate the size of the residual ice cone, which can predict the maximum radius of impression and collision duration.
COLD REGIONS SCIENCE AND TECHNOLOGY
(2022)
Article
Optics
Wenting Wang, Haitao Yu, Jianqi Shen, Cameron Tropea
Summary: Rainbow scattering can provide information about the size, refractive index, temperature, and composition of droplets. Using a highly focused Gaussian illumination beam can improve the spatial resolution in dense spray situations. This study investigates rainbow scattering from spherical droplets and explores different inversion algorithms and the effect of beam incident position on droplet characterization. For water droplets in the size range of 50-200 μm, high accuracy in measuring the relative refractive index and small relative error in size can be achieved.
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
(2022)
Article
Engineering, Chemical
Can Li, Qimeng Lv, Ning Li, Yingchun Wu, Xuecheng Wu, Chunsheng Weng, Cameron Tropea
Summary: There is significant interest and demand for the multi-parameter characterization of colloidal droplets. However, optical in-situ characterization of such droplets poses a challenge due to their heterogeneous and multi-scale nature. This study proposes an analytical model for dual-wavelength extinction rainbow refractometry, which allows for the simultaneous measurement of inclusion concentration, particle size, refractive index, and droplet diameter. Validation experiments demonstrate the effectiveness of this method, and the measurement errors and limitations are analyzed.
Editorial Material
Engineering, Mechanical
Alexander Yarin, Ilia V. Roisman, Hyoungsoo Kim, Cameron Tropea
EXPERIMENTS IN FLUIDS
(2022)
Article
Engineering, Environmental
M. Gloerfeld, M. Schremb, I. V. Roisman, J. Hussong, C. Tropea
Summary: The initial stage of solidification of a free supercooled water drop involves the formation of dendritic structures surrounded by liquid water. However, the impact dynamics and material properties of these partially frozen water drops have not been thoroughly studied. This study examines the kinematics of spreading and the geometry of the residual splat during the impact of dendritically frozen water drops. A theoretical model is then used to simulate the impact process, assuming plastic flow in the mushy drop. The model provides insights into the fluid flow near the impact axis and allows estimation of the apparent yield strength of the solid-liquid mixture for different initial temperatures.
COLD REGIONS SCIENCE AND TECHNOLOGY
(2023)
Article
Mechanics
Bastian Stumpf, Ilia V. V. Roisman, Alexander L. L. Yarin, Cameron Tropea
Summary: Drop impact on a liquid film results in a new mode of splash called simultaneous corona detachment, which is caused by the breakup of the wall film. The sudden displacement of the film leads to the thinning and rupture of the corona wall, triggering propagating rims that undercut and detach the entire corona. Experimental evidence and a proposed self-consistent theory support this mechanism.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Optics
Can Li, Wenmin Peng, Yang Kang, Xudong Fan, Xiaolong Huang, Ning Li, Chunsheng Weng, Cameron Tropea
Summary: Rainbow refractometry has been developed for spray measurement applications, allowing simultaneous measurement of refractive index and droplet size. This study investigates the feasibility and accuracy of using incomplete rainbow signals for measurement. The newly defined dimensionless signal partial ratio (SPR) quantifies the degree of incompleteness. Simulation and inversion experiments were conducted, and the results showed that inversion using signal fitting is more accurate than using specific characteristic points. Laboratory experiments also verified these findings. For SPR <= 1, rainbow refractometry achieves errors within 6 x 10-4, 3% for monodisperse droplets and 2 x 10-4, 8% for spray droplets in terms of refractive index and size.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Chemistry, Physical
Marija Gajevic Joksimovic, J. Benedikt Schmidt, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong
Summary: The effect of graphite lubricant additives on the dynamics of drop impact on a heated surface has been studied. The addition of particles increases the drop residence time and lowers the rebound temperature, suppressing splash and preventing coalescence of bubbles.
Article
Engineering, Mechanical
Shubham Sharma, Saini Jatin Rao, Navin Kumar Chandra, Aloke Kumar, Saptarshi Basu, Cameron Tropea
Summary: The two-sensor depth from defocus technique is developed to achieve higher spatial and temporal resolution, improve estimates of spatial size distribution and number concentration, and provide guidelines for the calibration and design of optical systems. The technique and improvements are demonstrated in the case of secondary atomization with a shock wave and a single drop, where high-resolution number density and size distributions of secondary droplets are necessary.
EXPERIMENTS IN FLUIDS
(2023)
Article
Physics, Multidisciplinary
Marija Gajevic Joksimovic, Jeanette Hussong, Cameron Tropea, Ilia V. V. Roisman
Summary: Spray cooling is a method used in various industrial processes and for cooling of electrical devices. The process is influenced by hydrodynamic and thermodynamic processes, and becomes more challenging when dealing with multicomponent liquids. In this study, the impact of spray onto a heated substrate was visualized and the heat transfer was characterized. The presence of a small concentration of lubricant significantly increased the heat flux and shifted the Leidenfrost point.
FRONTIERS IN PHYSICS
(2023)
Article
Thermodynamics
Kilian Koebschall, Benjamin Traut, V. Ilia Roisman, Cameron Tropea, Jeanette Hussong
Summary: This study presents an experimental setup and a theoretical model for studying snowflake melting. The experimental results agree well with the model predictions, and an accurate value of the particle mass fractal dimension is required for accurately estimating the melting duration.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Mechanics
Niklas Apell, Cameron Tropea, Ilia V. Roisman, Jeanette Hussong
Summary: With the increasing economic importance of metal additive manufacturing by laser powder bed fusion, the demand for high-quality metal powders is also rising. However, the physics involved in supersonic close-coupled gas atomization, which is often used for producing these powders, are not well understood due to scarce experimental data, resulting in a lack of reliable predictive modeling capabilities.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Thermodynamics
Yasir A. Malik, Kilian Koebschall, Stephan Bansmer, Cameron Tropea, Jeanette Hussong, Philippe Villedieu
Summary: Ice crystal icing is a significant hazard in aviation, and accurate modeling of sticking efficiency is essential. In this study, icing wind tunnel experiments were conducted to quantify the volumetric liquid water fraction, sticking efficiency, and maximum thickness of ice layers. Two measurement techniques, calorimetry and capacitive measurements, were used to measure the liquid water content and distribution in the ice layers. The experiments showed that increasing wet bulb temperatures and substrate heat flux significantly increased sticking efficiency and maximum ice layer thickness.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
J. B. Schmidt, F. Tenzer, C. Tropea, J. Hussong, I. V. Roisman
Summary: Spray cooling is a technology that provides uniform and intense cooling for surfaces with complex geometry. It can be used in a wide range of surface temperatures for various applications. The performance of spray cooling depends on factors such as surface temperature, spray parameters, and the thermal properties of the liquid and substrate. This study focuses on the transitional boiling regime, which is the least studied due to its complexity. A model is developed to predict the heat flux during spray cooling in this regime and shows good agreement with experimental results.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Engineering, Mechanical
Bastian Stumpf, Jonas H. Ruesch, Ilia Roisman, Cameron Tropea, Jeanette Hussong
Summary: This study introduces an imaging technique supported by a machine learning algorithm to determine the volume fraction of each liquid component in two-component droplets. It demonstrates the application of this technique by measuring the volume fraction in splashed secondary droplets following the impact of a drop of one liquid onto a film of a different liquid.
EXPERIMENTS IN FLUIDS
(2022)