Droplet Parameters Research Articles

Detecting the droplet and bubble in the oil-gas-water three-phase medium via ultrasonic A-scan signal-assisted B-mode imaging method

Abstract Accurately detecting the parameters of bubbles and droplets in the oil-gas-water three-phase medium is essential to critical decision-making about industrial production. An ultrasonic A-scan signal-assisted B-mode imaging (AS-assisted-BI) method that combines a B-mode imaging (BI) method and an A-scan signal (AS) method is developed to simultaneously visualize the oil-gas-water three-phase medium, distinguish the gas bubble and oil droplet, and measure the parameters about their sizes and locations. The applicability of the plane wave imaging (PWI) method for visualizing the oil-gas-water three-phase medium with less computational cost was confirmed. Then, the influence of the bubble and droplet characteristics, such as acoustic impedance difference, size, and location, upon the ultrasonic propagation mechanism are studied to understand the B-mode image and A-scan signal as the design basis of the BI and AS method. The BI method locates the least key points from the B-mode image based on the PWI method compared with the conventional industrial B-mode image method. The AS method automatically locates the key point from the A-scan signal rather than manually marking it in the previous study. Two options for the AS-assisted-BI method, suitable for different detection requirements and applications, have been designed. The numerical simulation and experimental results demonstrated that the proposed method received excellent precision, robustness, and efficiency for detecting the acoustic impedance difference between the bubble and droplet, the longitudinal location of the bubble front surface, and the droplet’s size and center location.

Numerical study of breakdown voltage calculation and discharge characteristics of millimeter-level short air gap with a single water droplet

Abstract Water droplets in the short air gap significantly affect the breakdown voltage. Currently, there is a lack of computational studies on the breakdown voltage and discharge process of short air gaps containing water droplets. In this paper, we establish a plasma dynamics-based model for the discharge in a millimeter-scale short air gap containing a single water droplet under ambient pressure and propose a breakdown voltage calculation method. We discuss typical discharge processes, calculate breakdown voltages for different gap lengths, validate the model through discharge phenomena and breakdown voltage, and analyze the impact of droplet parameters on discharge characteristics. The results show that negative streamer discharge in the cathode-side gap and positive streamer discharge in the anode-side gap occur sequentially, consistent with reported experimental results, with the positive streamer discharge being the primary process leading to gap breakdown. The average error rate between the calculated breakdown voltages for 4–8 mm gaps and reported experimental results is 4.85%, indicating good agreement. The observed streamer branching phenomenon may explain the difference between calculated and experimental breakdown voltages for the 10 mm gap. Under the influence of surface charges, low-conductivity droplets cause the discharge channel to propagate along the droplet surface. In contrast, high-conductivity droplets confine the discharge channel within the two gap sections. Increasing droplet diameter reduces breakdown voltage, with a critical value where the reduction becomes significant. Increased droplet deformation degree raises the breakdown voltage. This effect is related to the deviation of the positive streamer from the axial development and the reverse streamer generated on the droplet’s surface in different cases. The closer the droplet is to the electrode, the higher the breakdown voltage. The discharge is facilitated by the streamers generated on the droplet’s lower surface when it is close to the anode.

Anisotropic dipolar vortex quantum droplets in an annular potential

Two-dimensional dipolar Bose–Einstein condensates confined within an annular potential are investigated. Stable ring-shaped anisotropic dipolar vortex quantum droplets are discovered in this configuration. These droplets remain stable under the influence of the annular potential, even with embedded vorticity up to 11. The stability regions of dipolar vortex droplets with varying embedded vorticity are confirmed through long time evolution. The characteristic parameters of the dipolar vortex droplets are systematically studied, and their existence curves are shown to contradict the well-known V–K criterion. Additionally, the shape transformation of dipolar vortex droplets induced by the strength of the mean-field interaction is examined. Finally, the behavior of dipolar vortex droplets confined within a wake-depth annular potential is also discussed.

Investigation of droplet splashing behavior during oblique jet impact onto a wall

For the issue of jet impingement on the wall in industrial cooling processes, an experimental setup based on high-speed photography for oblique jet impingement onto the wall was constructed. The experimental focus was on the study of liquid droplet splashing behavior after oblique jet impingement on the wall, discussing the liquid droplet splashing behavior under three jet impingement modes: Rayleigh regime, first wind-induced regime, and secondary wind-induced regime. By employing methods such as trajectory imaging and particle image velocity for liquid droplet parameter image measurement, obtaining the particle size, velocity, and distribution of splashed droplets after oblique jet impact on walls under different working conditions. The impact of jet impingement velocity and angle on droplet splashing parameters was analyzed. The results showed that when the impingement point is before the breakup length, with increasing flow velocity, the surface wave of the liquid column, and the spreading liquid film became more pronounced, but the loss of liquid-phase components due to splashing was relatively small. When the impingement point is after the breakup length, the secondary breakup resulting in a “crown”-shaped liquid film after droplet impingement leads to a significant loss of liquid-phase components through splashing. As the inlet velocity of the jet increases, there is a decreasing trend in droplet size and an increasing trend in droplet velocity. With an increase in jet angle, there is a decreasing trend in droplet size and velocity. Based on the concentration, size, and velocity distribution characteristics of splashing droplets, the area after oblique jet impingement on the wall can be divided into the impingement zone, low-concentration low-velocity zone, high-concentration high-velocity zone, and lateral splashing zone. This has significant implications for understanding the splashing mechanism after oblique jet impingement on the wall and optimizing operating conditions.

Triboelectric decoupling measurement for droplet parameters in microfluidic chips

Droplet microfluidics have attracted substantial scientific and industrial attention with a focus on measuring droplet parameters. The solid-liquid triboelectrification offers a self-powered way to avoid cumbersome systems towards miniaturization and portability for on-chip measurements, but it faces a decoupling challenge. Here, the bulk-effect solid-liquid triboelectrification is introduced into microfluidic chips for droplet parameter measurement. A multi-stage solid-liquid triboelectrification model is developed, unveiling the characteristics of volume-related shape uniqueness, flow-rate-related shape scaling, and flow-direction-related shape symmetry to achieve the decoupling measurement of droplet motion parameters including volume, flow rate, and flow direction. Such capacity has been applied to the droplet electrolyte measurement in concentration-gradient microfluidic chips featuring Y- and Christmas-tree-shaped configurations. Furthermore, the bulk-effect introduction enables the detection of nucleic acids inside droplets, extending from non-specific to specific detection. This work is very demonstration of triboelectric decoupling measurement for droplet parameters, advancing the on-chip measurements of droplet microfluidics.

Correlation study between structural parameters of droplets and rheological properties of O/W high internal phase Pickering emulsions above the closest packing density

The correlation between the structural parameters of droplets and rheological properties of O/W high internal phase Pickering emulsions (HIPPEs) stabilized by soy protein isolate (SPI) nanoparticles was elucidated, with a volume fraction of dispersed phase (ϕ) above the closest packing density (74%). The structural basis of SPI nanoparticles was confirmed to be spherical heat-induced protein aggregates, which had moderate wettability and excellent interfacial activity. The structural parameters of emulsion droplets (contact length L, diameter D, length d1, width d2, the number of adjacent contact droplets Z), and the stability and rheological properties of HIPPEs were characterized by the confocal laser scanning microscopy (CLSM), diffusing wave spectroscopy (DWS), and mechanical rheometer respectively. The results of CLSM indicated the transition of droplets from spherical to polyhedral shapes as increased ϕ, accompanied by an increased L and Z. The rheological and stability analysis confirmed the widened linear viscoelastic range, elevated gel point (εc), and the extended half−life of the intensity autocorrelation function of HIPPEs as ϕ increased. Moreover, the loss factor (tan δ) remained constant at 0.1 within the ϕ of 74%–86%, revealing the solid−like nature of HIPPEs. The correlation between ϕ, structural parameters of droplets, and rheological properties of HIPPEs was further analyzed. The nonlinear regression fitting between the L/D and G' (elastic modulus) yielded a better fitting effect than d1/d2 and Z, suggesting an intrinsic correlation between emulsion structure and rheology. In summary, this study elucidated the intricate relationship between ϕ, droplet structure, and rheological properties of HIPPEs, offering a research foundation and theoretical basis for the development and application of protein particle−stabilized HIPPEs.

Formation dynamics of the satellite droplet in the breakup of a symmetrical liquid bridge

Inkjet printing technology has played an irreplaceable role in life science, precision manufacturing, and other frontier fields in recent years. However, the further development of this technology is limited by the fact that its printing resolution is difficult to raise to a higher level. The emerging satellite droplet printing technology offers a new approach for inkjet printing to break through the bottleneck of printing resolution limitations. In this paper, a symmetrical satellite droplet printing strategy is proposed. The effects of the geometric parameters of the satellite droplet generating device, the physical properties of the ink, and the operating parameters on the liquid bridge breakup process and the size of the satellite droplet are systematically studied. The phase field method and adaptive mesh refinement strategy are applied to solve the two-dimensional symmetrical model. The results indicate that the length of the liquid bridge, the radius of the bridge, the viscosity of the ink, and the drainage velocity are all positively correlated with the satellite droplet size, while the surface tension coefficient has a negative correlation with the satellite droplet size. Furthermore, the three-phase contact line at the orifice end will slip toward the center if the initial radius of the liquid bridge is quite large. Based on these investigations and discussions, a corresponding effective working space for satellite droplet printing is obtained, which lays the foundation for the popularization and further development of satellite droplet printing technology.

An analytical model for ice accretion on the engine strut surface

To predict flight icing more widely and practically, an ice accretion numerical framework that incorporates both the water droplet splash and the ice crystal sticking is developed. By proposing a deformation hypothesis, we deduce the modified energy conservation expression and the force balance relation for water droplet impingement. Subsequently, a new threshold determination and the probabilities for the droplet splash and ice crystal sticking are obtained, which are applicative across a wide range of Weber number after the validation. Through the interface tracking for a single droplet with the volume of fluid method, the droplet impingement dynamics are further explored, and the results of interaction with the wall serve the boundary treatments of droplet impingement in the discrete phase model. Additionally, the probability statistics method is employed to determine the parameters of the secondary droplets. Through the dynamic mesh technique, the retentive water droplets and the collected ice crystals are transformed into the accumulated ice in real time to update the ice accretion on the strut surface. Results demonstrate that the diameter, velocity, and content of droplets or crystals play significant roles in the impingement and the icing phenomena. Based on our numerical model, the predictions show that the ice accretion on the engine strut is influenced by flight parameters and environmental conditions, providing crucial guidance for the icing protection processes.

Numerical and Experimental Analyses of the Effect of Water Injection on Combustion of Mg-Based Hydroreactive Fuels

The energy release process of the Mg-based hydroreactive fuels directly affects the performance of water ramjet engines, and the burning rate is one of the key parameters of the Mg-based hydroreactive fuels. However, there is not enough in-depth understanding of the combustion process of Mg-based hydroreactive fuels within the chamber of water ramjet engines, and there is a lack of effective means of prediction of the burning rate. Therefore, this paper aims to examine the flame structure of Mg-based hydroreactive fuels with a high metal content and analyze the impact of the water injection velocity and droplet diameter on the combustion property. A combustion experiment system was designed to replicate the combustion of Mg-based hydroreactive fuels within water ramjet engines, and the average linear burning rate was calculated through the target line method. On the basis of the experiment, a combustion–flow coupling solution model of Mg-based hydroreactive fuels was formulated, including the reaction mechanism between Mg/H2O and the decomposition products from an oxidizer and binder. The model was validated through experimental results with Mg-based hydroreactive fuels at various pressures and water injection velocities. The mean absolute percentage error (MAPE) in the experimental results was less than 5%, proving the accuracy and validity of the model. The resulting model was employed for simulating the combustion of Mg-based hydroreactive fuels under different water injection parameters. The addition of water injection resulted in the creation of a new high-temperature region, namely the Mg/H2O non-premixed combustion region in addition to improving the radial diffusion of the flame. With the increasing water injection velocity, the characteristic distance of Mg/H2O non-premixed combustion region is decreased, which enhances the heat transfer to burning surface and accelerates the fuel combustion. The impact of droplet parameters was investigated, revealing that larger droplets enhance the penetration of the fuel-rich gas, which is similar to the effect of injection velocity. However, when the droplet size becomes too large, the aqueous droplets do not fully evaporate, resulting in a slight decrease in the burning rate. These findings enhance the understanding of the mechanisms behind the burning rate variation in Mg-based hydroreactive fuels and offer theoretical guidance for the optimal selection of the engine operating parameters.

Highly Parallel Droplet Dispensing Approach to Provide Homogeneous and Controllable Droplet Arrays for Diagnostic Test Manufacturing.

We introduce a novel approach for highly parallel droplet dispensing with precise control over the droplet parameters such as droplet volume, droplet velocity, etc. This approach facilitates the fabrication of homogeneous and precise thin layers with uniform coverage on defined small areas (e.g., a specific area of 1 × 1.4 mm2 in microfluidic channels or microwells). The presented approach ensures layer uniformity and high precision in X/Y extent and edge resolution, making it well suited for achieving precise and controlled coating for a variety of applications such as homogeneous coatings for lateral flow tests, ELISA plates, and biosensors for continuous glucose monitoring (CGM) devices. Our approach is based on direct liquid displacement employing a piston that is in direct contact with the liquid and an array of nozzles. Considering a variety of nozzle chip designs (i.e., varying nozzle diameter and pitch), we evaluated a multitude of parameters to derive general design rules for the nozzle chip design. Thus, we achieved a tunable droplet volume from 200 to 800 pL and droplet velocities from 0.5 to 2.5 m/s, applying a nozzle diameter of 50 μm and a nozzle pitch of 165 μm. The presented results showcase the versatility of the approach, offering precise dispensing capabilities.

Flow behavior and characteristic parameters of droplets in counter-current mini-channel extractor

Achieving the counter-current flow in mini-channel extractor is a challenge. The formation and characteristic parameters of droplets in mini-channel counter-current extractor were systematically investigated to provide a guide for the realization and operation of counter-current extraction. A mixture of P507 diluted with sulfonated kerosene was served as dispersed phase, while 0.2 mol/L LaCl3 solution was used as continuous phase. Droplets rapidly deformed from the nearly-spherical shape to ellipsoidal shape after detaching from nozzles, eventually floated upwards as monodisperse droplets with same spacing. Sauter mean diameter of droplets decreased with the increase of superficial velocity of organic phase, yet increased with the increase of superficial velocity of aqueous phase. The specific interfacial area of droplets increased with the increasing superficial velocity of organic phase, and slightly decreased with the increasing superficial velocity of aqueous phase. The correlations of droplet characteristic parameters were established using dimensional analysis for further prediction and analysis.

Aerodynamic breakup of gel suspension droplets loaded with aluminum particles

The persistent and frequent space explorations are affected by the performance of propellants, among which the closely related gel propellants have been widely used due to their unique characteristics. Currently, research efforts primarily concentrate on the metallization and atomized combustion of gel propellants, emphasizing the combustion performance of metallized gel propellants. However, little attention has been given to the secondary breakup process that occurs just before combustion. By utilizing high-speed flow visualization technology, this study examines the key aerodynamic breakup process of gel suspension droplets loaded with micro aluminum particles, experimentally and theoretically investigating the droplet dynamics induced by particle volume fraction. The experimental confirmation of the three breakup behaviors exhibited by gel suspension droplets, namely oscillation mode, bag-stamen breakup, and hemline breakup, is presented along with the construction of a phase diagram. The impact of heterogeneous effects resulting from an increase in particle volume fraction on the critical breakup Weber number is revealed, with a concentration of 9 % as the turning point. Within the range of moderate Weber numbers, the tail flick deformation of suspension droplets in airflow is observed and reported for the first time. At different particle concentrations, there keeps a linear correlation between the dimensionless tail length and Weber number. Spherical suspension droplets will deform into thin disks in the airflow, with a nearly constant deformation rate regardless of changes in particle concentration. Additionally, the relationships between characteristic times and droplet parameters are discussed through statistical analysis of the results. As Ohnesorge number and particle volume fraction increase, the characteristic times both show a monotonically increasing trend. Moreover, a model of unstable growth rate associated with the particle volume fraction is established through linear instability analysis, accurately predicting the variation in critical Weber number for gel suspension droplet breakup. The congruence between our theoretical framework and experimental findings not only enhances comprehension of the impact of micro aluminum particles on the secondary breakup of gel suspension droplets but also provides valuable guidance for the aerospace applications of metallized gel propellants.

Excess Intramyocellular Lipid Does Not Affect Muscle Fiber Biophysical Properties in Mice or People With Metabolically Abnormal Obesity.

Observational studies show correlations between intramyocellular lipid (IMCL) content and muscle strength and contractile function in people with "metabolically abnormal" obesity. However, a clear physiologic mechanism for this association is lacking and causation is debated. We combined immunofluorescent confocal imaging with force measurements on permeabilized muscle fibers from metabolically normal and metabolically abnormal mice and metabolically normal (defined as normal fasting plasma glucose and glucose tolerance) and metabolically abnormal (defined as pre-diabetes and type 2 diabetes) people with overweight/obesity to evaluate relationships among myocellular lipid droplet characteristics (droplet size and density) and biophysical (active contractile and passive viscoelastic) properties. The fiber type specificity of lipid droplet parameters varied between metabolically abnormal and normal mice and among metabolically normal and metabolically abnormal people. However, despite considerable quantities of IMCL in the metabolically abnormal groups, there were no significant differences in peak active tension or passive viscoelasticity between the metabolically abnormal groups and the control group in mice or people. Additionally, there were no significant relationships among IMCL parameters and biophysical variables. Thus, we conclude that IMCL accumulation per se does not impact muscle fiber biophysical properties or physically impede contraction.

Role of elasticity on polymeric droplet generation and morphology in microfluidic cross-junctions

Recently, our direct numerical simulations [Duan et al., Phys. Fluids 36, 033112 (2024)] showed that fluid elasticity affects the extension length and pinch-off time of the droplet formation process, thus changing the flow pattern. However, the effect of fluid elasticity on the morphology and properties of polymeric droplets is not yet fully understood. In this work, by analyzing the stretched state of the polymer macromolecule and the velocity distribution of the flow process, we find that the increase in fluid elasticity (characterized by the relaxation time) inhibits the contraction of the dispersed phase during droplet pinching and resists the effect of surface tension after droplet generation, which significantly affects the droplet geometry, volume, and generation frequency. The results demonstrate that the length and volume of polymeric droplets increase with the relaxation time of the polymer fluid, while the generation frequency decreases. Meanwhile, the effects of polymer viscosity and the superficial velocity ratio of the continuous to the dispersed phase on the droplets' morphology are investigated. The semi-empirical models for the length, volume, and generation frequency of polymeric droplets are developed for the first time by considering the elastic interaction. The purpose of our work is to provide a better understanding and experimental guidance for controlling the parameters of polymeric droplets with viscoelasticity of different shapes and sizes.

Self-calibration performance analysis of sheet micro-components based on droplet array

The droplet array-based micro-component self-calibration method features simple operation, easy batch control implementation, and holds great promise in the field of micro-assembly. The paper investigates the self-calibration process, analyzes the factors influencing self-calibration performance, discusses self-calibration errors, self-calibration range, and their relationship with micro-component parameters, droplet array parameters, and fluid parameters, and proposes a construction method suitable for droplet arrays suitable for micro-components. The research results indicate that the self-calibration error and calibration range of micro-components are related to micro-component parameters, substrate array parameters, and droplet parameters. When the micro-component size is greater than or equal to the droplet array size, the self-calibration error is relatively small. Constructing an appropriate droplet array based on the size and shape of the micro-components can reduce self-calibration errors and meet the self-calibration accuracy requirements for micro-components of varying sizes and shapes.

Screening drug-induced liver injury through two independent parameters of lipid droplets and peroxynitrite with a π-extended coumarin-based NIR fluorescent probe

Drug-induced liver injury (DILI) or hepatotoxicity is a significant concern for public health. However, relying on a single biomarker for early DILI diagnosis poses a high risk of false positives. In this study, we reported a near-infrared fluorescent probe (BCOU-S), which enables independent visualization of LDs status and ONOO fluctuations. BCOU-S was constructed by combining a π-extended coumarin core as the NIR fluorophore and a methyl thioether group as the ONOO recognition site. BCOU-S could emit 655 nm NIR fluorescence excited at 518 nm, with a low detection limit of 27 nM and a large Stokes shift of 137 nm. The response mechanism to ONOO was confirmed by molecular orbital density function theory (DFT) and time-dependent DFT (TD-DFT) calculations. BCOU-S monitors LDs status through co-localization, oleic acid (OA) incubation, and starvation induction experiments. It sensitively distinguishes subtle changes in ONOO induced by different drugs in DILI cell models. In the acetaminophen (APAP)-induced DILI model, BCOU-S reveals significant LDs accumulation and increase in ONOO levels, establishing a clear time-effect and dose-effect relationship. Simultaneously monitoring ONOO levels and LDs accumulation, BCOU-S proves to be a more sensitive and effective tool for early DILI prevention, effectively avoiding false positives caused by changes in a single parameter. BCOU-S is a useful tool for further monitoring early DILI development.

Research on the influence of initial parameters of water droplets on the performance of counter-rotating axial-flow compressor

This paper employs a numerical simulation method to investigate the wet compression working characteristics of a counter-rotating axial-flow compressor (CRAC) in an air-inlet, water-containing environment under different water droplet parameters at a designed rotational speed. The influence of initial water droplet parameters on the overall performance of the CRAC and the variations in the flow field characteristics under different wet compression conditions was investigated. The initial diameter of water droplets exhibited the most significant impact on the wet compression effect. Under an appropriate inlet water content, water droplets with smaller diameters effectively reduced the temperature of the CRAC’s internal flow field, increasing the air density. Consequently, the axial velocity decreased, altering the velocity triangle and increasing the rotor working capacity, which enhanced the performance of the CRAC. Additionally, wet compression influenced the flow field of the rear rotor stronger than that of the front rotor. When the initial diameter of water droplets is too large, the evaporative cooling effect cannot be fully exploited so wet compression only slightly improved the compressor performance. These findings may help understand the working characteristics of the CRAC in water-containing environments better, offering guidance for CRAC design using wet compression technology.

Aerosolized Insecticide Spray Distributions and Relationships to Efficacy against Stored Product Pests.

Aerosol insecticides are widely used in stored product insect management programs in food facilities. Previous research has shown spatial variation in aerosol efficacy within facilities, but information on how spatial patterns of aerosol droplet concentration, size distribution, dispersal, and deposition contribute to this variation in efficacy is limited. This study involved two aerosol application systems: a high-pressure cylinder containing TurboCide Py-75® with pyriproxyfen IGR (ChemTech Ltd., Des Moines, IA, USA) and a hand-held fogger containing Pyrocide 100® (MGK, Minneapolis, MN, USA) with Diacon II which contains methoprene IGR (Wellmark, Schaumburg, IL, USA). These systems were used at single or multiple application locations. The spray trials were conducted in a small-scale flour mill, Hall Ross Flour Mill (Kansas State University, Manhattan, KS, USA). The droplet size distributions were monitored at multiple positions within the room using nine aerodynamic particle sizing (APS, TSI Incorp, Shoreview, MN, USA) instruments. The APS data collected over the treatment period were summarized into a mass concentration index (MCI), which ranged from 155 to 2549 mg/m3 for Turbocide and 235-5658 mg/m3 for Pyrocide. A second parameter called the Deposition Index (Dep.Idx) was derived to estimate potential insecticide depositions on the floor and has units of g/m2. The Dep.Idx was below 5.3 g/m2 for most Turbocide applications, while the Dep.Idx was below 8.4 g/m2 for most Pyrocide applications. The MCI and Dep.Idx values varied with APS position and spray application location, with proximity to the aerosol application location and degree of obstruction between the release point and APS position contributing to this variation. We assessed the relationship between aerosol droplet parameters and insect efficacy using Tribolium confusum Jacqueline DuVal, the confused flour beetle. The adults were treated directly, while the larvae were treated two weeks later during the residual test (previously published). For Turbocide, efficacy against adults increased with MCI and Dep.Idx values, but for residual efficacy of the IGR, efficacy was high at all aerosol droplet values, so no relationship was apparent. In contrast, the relationship between Pyrocide deposition and adult insect efficacy was highly variable. But with larval insect efficacy, residual larvae control was directly related to increases in Pyrocide MCI and Dep.Idx. Contour plots of Dep.Idx values were developed, which could be used to predict areas of the mill that are not receiving an adequate application rate, and this could be used to develop more effective application strategies for aerosol insecticides in food facilities.

Right partial rainbow refractometry for measuring droplet refractive index and size

Rainbow refractometry can be employed for measuring the parameters of droplets or sprays. Considering the diversity of different measurement environments and droplet components, there are instances in experiments where optics fail to record the complete rainbow signal. To enhance the experimental data utilization, this paper investigates rainbow refractometry using the incomplete rainbow signal on the right side, focusing on its feasibility and accuracy. The concept that defines the incompleteness of the right-sided rainbow signal is termed as the dimensionless right signal partial ratio (RSPR). The study conducts a comprehensive analysis of refractive index, droplet diameter, and size distributions retrieved from the partial rainbow signals simulated by the Lorenz-Mie theory with varying RSPR values. For both partial standard and global rainbows, the critical value of the retrieval error is found to be whether the primary peak of the rainbow is preserved or not, i.e., RSPR = 1. Laboratory experiments verify the feasibility and effectiveness of employing rainbow refractometry with right partial rainbow signals. The study addresses the challenge of incomplete recording of rainbow signals in experiments, and is expected to improve experimental efficiency and data utilization.

Experimental investigation on droplet evolutions in co-flow around the bluff body

Annular mist flow widely exists in natural gas and other engineering fields. Vortex flowmeter has gradually become an effective means of wet gas measurement. However, the droplets in the flow field will influence the stability of the vortex. In this paper, the interaction between droplets and vortex was studied by experiments. A novel in-focus criterion was proposed to improve the accuracy of droplet measurement. Simultaneous acquisition of droplet size, velocity, and concentration was achieved. The spatial evolution of droplet parameters was obtained to determine the position where the droplets were evenly distributed. The bidirectional coupling mechanism between droplets and vortex was studied. Firstly, the influence of the vortex flow field on droplets was reflected by the characteristics of droplet distribution around the bluff body. Secondly, the effect of droplets on the vortex signal in the flow field was analyzed based on Stokes number Stp and liquid-phase load φl. When φl < 0.03, the probability distribution of droplet velocity downstream of the bluff body presents double peaks. The exchange momentum between the small droplets and the vortex is stronger, and vice versa for the larger droplets. Finally, the quality factor of vortex signals decreases from -2.09 to -2.18 with the increase in the volume concentration of droplets. It is further demonstrated that the increase in volume concentration of droplets will destroy the vortex structure and degrade the quality of the vortex signal.