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Droplet impact is a common occurrence in nature, agriculture, and industry. The research on the multi‐droplet impact is fundamental to understanding the tangled nature of reality. This paper numerically studies the successive oblique impact of dual droplets on the liquid film by building an effective three‐dimensional model. The leading and trailing droplets are set to pass a certain impact point with the same velocity. The main contribution of this paper is the investigation of the effects of Weber number, liquid film thickness, impact angle, and impact time interval on the interface morphology evolution after the droplet impact. Results show that splash pattern conversion of the primary or secondary crown occurs with the change of these factors. Besides, the variations of the maximum crater radius in upstream, lateral, and downstream directions with time are quantitatively analyzed. The crater radius analysis is carried out from three perspectives, the variation during the single droplet impact, the change during the dual droplets impact, and the comparison between them. It is found that the crater of dual droplets impact exhibits shape distortion in the deformation period and appears a marked dimensional increase in the secondary expansion period. [ABSTRACT FROM AUTHOR]

Controlling the distribution of the abrasive grains on the surface of the grinding tools in an appropriate way is important for improving the quality of grinding processing and meeting the workpiece precision requirements. In the present study, a novel method for the orderly arrangement of abrasive particles is proposed by using the liquid film flow on the surface of the rotating disk as the driving and controlling means for the uniform dispersion and position arrangement of abrasive particles. Computational fluid dynamics (CFD) simulations have been performed to clearly illustrate the trajectories of abrasive particles under the strong influence of liquid film flow on the rotating disk and reveal the effects of fluid flow, disk rotational motion, and the mixture viscosity on the particle distribution. A new abrasive grain arrangement device is designed and fabricated using this novel method. The operating parameters such as liquid volume flow rate, disk rotational speed, and liquid viscosity are adjusted to control the placement of abrasive grains on the surface of the grinding tool. An image processing tool is used to examine and analyze the arrangement results. The experimental results indicated that the application of the liquid film flow on a rotating disk to the abrasive grain arrangement can improve the arrangement of abrasive grains and get rid of the dependence on the template. [ABSTRACT FROM AUTHOR]

The leading-edge erosion of a wind turbine blade was tested using a whirling arm rain erosion tester, whose rotation rate is considerably higher than that of a full-scale wind turbine owing to the scale effect. In this study, we assessed the impact pressure of droplets on a wet surface of wind turbine blades using numerical simulation of liquid droplet impact by solving the Navier–Stokes equations combined with the volume-of-fluid method. This was conducted in combination with an estimation of liquid film thickness on the rotating blade using an approximate solution of Navier–Stokes equations considering the centrifugal and Coriolis forces. Our study revealed that the impact pressure on the rain erosion tester exceeded that on the wind turbine blade, attributed to the thinner liquid film on the rain erosion tester than on the wind turbine blade caused by the influence of centrifugal and Coriolis forces. This indicates the importance of correcting the influence of liquid-film thickness in estimating the impact velocity of droplets on the wind turbine blade. Furthermore, we demonstrated the correction procedure when estimating the impact velocity of droplets on the wind turbine blade. [ABSTRACT FROM AUTHOR]

Mar-M247 is widely used in several fields as a material with excellent overall performance at high temperatures. However, its complex fabrication process and extremely poor weldability make it very difficult to repair and fabricate. In this study, a novel flux-cored wire with microstructures and composition similar to that of Mar-M247 nickel-based superalloy had been successfully developed, and the superalloy had been effectively repaired by cold metal transfer welding technique. Under the strict control of welding parameters, good metallurgical bonding between the weld and the base metal can be realized, and the hot cracking problem of the joint was successfully suppressed. In the weld, there were closely arranged γ′ phase precipitates with nanoscale and γ/γ′ eutectic structure, granular carbides dispersed at grain boundaries. The hardness of the weld was about 410–430 HV. It had been found that solidification cracks in welds were caused by intergranular liquid films, and grain orientation was found to be an important factor affecting solidification cracking. Optimized welding parameters of cold metal transfer could control the grain orientation of weld and reduce the size of intergranular liquid film, which could effectively suppress the size of weld solidification cracks. Additionally, liquefaction cracks were caused by eutectic reaction liquefaction in the heat-affected zone. The cold metal transfer welding process with optimized parameters can effectively reduce welding heat input, weaken eutectic reactions, and successfully obtain joints without crack in heat-affected zone.

A fifth-order nonlinear wave equation (generalized Korteweg–deVries equation) that arises in the theory of thin liquid films is introduced with the odd viscosity by the long-wave approximation regime. The presence of the odd viscosity is considered to be a non-dissipative factor in the evolution of the film flow. Sinusoidal and travelling waves arise in systems with non dissipation and instability. The introduced wave equation includes quadratic and cubic nonlinearities. The linear instability of sinusoidal waves is analyzed. The stability and bifurcation of travelling waves are discussed. [ABSTRACT FROM AUTHOR]

During the discharge of floodwater from a hydropower station, a significant number of water droplets in motion are created in the downstream space. These droplets vary in size and velocity, causing challenges in determining the particle size and velocity distribution of the flood discharge atomized droplets. Currently, the particle-size distribution and velocity distribution of atomized droplets are considered to be independent, and the gamma function is used to describe the particle-size distribution and velocity distribution of droplets separately. However, a joint distribution of atomized droplet size and velocity is lacking. This paper uses the basic theory of maximum entropy to study the combined distribution of droplet size and velocity in the atomized flow caused by jet overflow. The present model was in a good agreement with experimental data, providing a method for the theoretical study of droplet size and velocity distribution in flood discharge atomization. [ABSTRACT FROM AUTHOR]

In this article, we use the modified extended direct algebraic method (mEDAM) to explore and analyze the traveling wave phenomena embedded in the quintic conformable Benney-Lin equation (CBLE) that regulates liquid film dynamics. The proposed transformation-based approach developed for nonlinear partial differential equations (PDEs) and fractional PDEs (FPDEs), efficiently produces a plethora of traveling wave solutions for the targeted CBLE, capturing the system's nuanced dynamics. The methodically determined traveling wave solutions are in the form of rational, exponential, hyperbolic and trigonometric functions which include periodic waves, bell-shaped kink waves and signal and double shock waves. To accurately depict the wave phenomena linked to these solutions, we generate 2D, 3D, and contour graphs. These visualizations not only improve understanding of the CBLE model's dynamics, but also provide a detailed way to examine its behavior. Moreover, the use of the proposed techniques contributes to a better understanding of the other FPDEs' distinct characteristics, enhancing our comprehension of their underpinning dynamics. [ABSTRACT FROM AUTHOR]

Multiphase flow entrainment in natural gas engineering significantly influences the safety and efficiency of oil companies since it affects both the flow and the heat transfer process, but its mechanisms are not fully understood. Additionally, current computational fluid dynamics (CFD) methodologies seldom consider entrainment behavioral changes in pipe elbows. In this article, a verified CFD method is used to study the entrainment behavior, mechanism, and changes in an elbow. The results show that droplet diameter in a developed annular flow follows a negative skewness distribution; as the radial distance (from the wall) increases, the fluctuation in the droplets becomes stronger, and the velocity difference between the gas and the droplets increases linearly. Turbulence bursts and vortices sucking near the wall jointly contribute to droplet entrainment. As the annular flow enters the elbow, the secondary flow promotes the film expansion to the upper and lower parts of the pipe. Droplets re-occur near the elbow exit intrados, and their size is much smaller than those in the upstream pipe. Vortices sucking under low gas velocity play an important role in this process. These findings provide guidelines for safety and flow assurance issues in natural gas production and transportation and bridge the gap between multiphase flow theory and natural gas engineering. [ABSTRACT FROM AUTHOR]

In this article, we use the modified extended direct algebraic method (mEDAM) to explore and analyze the traveling wave phenomena embedded in the quintic conformable Benney-Lin equation (CBLE) that regulates liquid film dynamics. The proposed transformation-based approach developed for nonlinear partial differential equations (PDEs) and fractional PDEs (FPDEs), efficiently produces a plethora of traveling wave solutions for the targeted CBLE, capturing the system's nuanced dynamics. The methodically determined traveling wave solutions are in the form of rational, exponential, hyperbolic and trigonometric functions which include periodic waves, bell-shaped kink waves and signal and double shock waves. To accurately depict the wave phenomena linked to these solutions, we generate 2D, 3D, and contour graphs. These visualizations not only improve understanding of the CBLE model's dynamics, but also provide a detailed way to examine its behavior. Moreover, the use of the proposed techniques contributes to a better understanding of the other FPDEs' distinct characteristics, enhancing our comprehension of their underpinning dynamics.

With recent advances in semiconductor technology, conventional cooling methods and standard coolants are no longer adequate to manage electronic chips’ enormous heat generation. Therefore, innovative cooling solutions are required to maintain these devices at optimum operating temperatures. Taylor flow in microchannels is an effective technique that allows excellent mixing of two fluids, which is crucial for heat transfer. A 3D numerical analysis of the heat transfer performance of liquid-liquid Taylor flow in a rectangular microchannel was carried out by ANYSY Fluent. Water droplets were dispersed in either ethylene or propylene glycol, with the interface between the two fluids captured using the Volume of Fluid method. For optimal computational time, two symmetries in the XY and XZ planes are considered. Furthermore, mesh size refinement was performed in the near-wall region to capture the liquid film. An analysis of the effect of plug/slug length and liquid film thickness is conducted with initially constant thermo-physical properties. This assumption was considered to analyse the heat transfer process and determine the most critical parameter affecting heat transfer performance. A user-defined function is then implemented in ANSYS Fluent to examine the effect of working fluids temperature-dependent viscosity change on the heat transfer rate. Conjugate heat transfer and axial conduction are also examined, as these two factors can significantly affect the thermal behaviour inside the microchannel and enable the achievement of realistic and accurate results. The results reveal that Taylor liquid-liquid flow can increase the heat transfer rate by up to 440% over single-phase flow. It was also found that the temperature-dependent viscosity of the working fluids significantly affects the plug/slug length and liquid film thickness, resulting in a 20.8% improvement in heat transfer rate compared with constant thermo-physical properties. This study will improve the state of knowledge on heat transfer by Taylor flow in microchannels and factors that can influence it, and highlight the significance of this flow pattern in enhancing heat transfer performance over single-phase flow.

Copyright of Journal of Henan University of Science & Technology, Natural Science is the property of Editorial Office of Journal of Henan University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

"Temperature swing" by heat insulation coating is a technology developed to reduce heat loss in diesel engines. The purpose of this study is to evaluate the fuel film thickness formed on the piston surface with heat insulation coating. A 1-dimensional heat transfer model is developed and the inside temperature distribution of the piston at the compression TDC of the first cycle of a diesel engine during cold start is estimated. The inside temperature distribution of the piston can be reproduced by instantaneous heating with a pulsed laser. The fuel film thickness is evaluated by applying the refractive index matching (RIM) method. When the piston is instantaneously heated with the pulsed laser, the fuel film thickness decreased by 15 % compared to no heating condition. [ABSTRACT FROM AUTHOR]

With recent advances in semiconductor technology, conventional cooling methods and standard coolants are no longer adequate to manage electronic chips' enormous heat generation. Therefore, innovative cooling solutions are required to maintain these devices at optimum operating temperatures. Taylor flow in microchannels is an effective technique that allows excellent mixing of two fluids, which is crucial for heat transfer. A 3D numerical analysis of the heat transfer performance of liquid-liquid Taylor flow in a rectangular microchannel was carried out by ANYSY Fluent. Water droplets were dispersed in either ethylene or propylene glycol, with the interface between the two fluids captured using the Volume of Fluid method. For optimal computational time, two symmetries in the XY and XZ planes are considered. Furthermore, mesh size refinement was performed in the near-wall region to capture the liquid film. An analysis of the effect of plug/slug length and liquid film thickness is conducted with initially constant thermo-physical properties. This assumption was considered to analyse the heat transfer process and determine the most critical parameter affecting heat transfer performance. A user-defined function is then implemented in ANSYS Fluent to examine the effect of working fluids temperature-dependent viscosity change on the heat transfer rate. Conjugate heat transfer and axial conduction are also examined, as these two factors can significantly affect the thermal behaviour inside the microchannel and enable the achievement of realistic and accurate results. The results reveal that Taylor liquid-liquid flow can increase the heat transfer rate by up to 440% over single-phase flow. It was also found that the temperature-dependent viscosity of the working fluids significantly affects the plug/slug length and liquid film thickness, resulting in a 20.8% improvement in heat transfer rate compared with constant thermo-physical properties. This study will improve the state of knowledge on heat transfer by Taylor flow in microchannels and factors that can influence it, and highlight the significance of this flow pattern in enhancing heat transfer performance over single-phase flow. [ABSTRACT FROM AUTHOR]

The leading-edge erosion of a wind turbine blade was tested using a whirling arm rain erosion tester, whose rotation rate is considerably higher than that of a full-scale wind turbine owing to the scale effect. In this study, we assessed the impact pressure of droplets on a wet surface of wind turbine blades using numerical simulation of liquid droplet impact by solving the Navier–Stokes equations combined with the volume-of-fluid method. This was conducted in combination with an estimation of liquid film thickness on the rotating blade using an approximate solution of Navier–Stokes equations considering the centrifugal and Coriolis forces. Our study revealed that the impact pressure on the rain erosion tester exceeded that on the wind turbine blade, attributed to the thinner liquid film on the rain erosion tester than on the wind turbine blade caused by the influence of centrifugal and Coriolis forces. This indicates the importance of correcting the influence of liquid-film thickness in estimating the impact velocity of droplets on the wind turbine blade. Furthermore, we demonstrated the correction procedure when estimating the impact velocity of droplets on the wind turbine blade.

Absract: The research studies the interaction between subcooled small diameter water jet and thick steel heater at different surface temperatures, liquid velocities and jet angles. Although the heater surface temperature exceeded the Leidenfrost temperature and reached 340°C, the liquid, according to visual observations, wetted the surface. Geometrical characteristics of the heater surface wetted area and jet deflection angles were measured. It was hypothesised that jet deflection from the surface, accompanied by finely dispersed drops generation, occurs when thermal boundary layer, which develops in the liquid near the heater surface, reaches the liquid's outer surface. The preliminary measurements seem to confirm the hypothesis. [ABSTRACT FROM AUTHOR]

Recently, there has been renewed interest in hollow droplets impaction since its great significance for thermal spraying, the three-dimensional (3D) printing of foam material. In the present study, we numerically study the dynamic characteristics of a hollow droplet obliquely impacting the liquid film via the volume of fluid (VOF) method. The splash formation and evolution during the oblique hollow droplet impact process under different conditions are investigated. The impact angle, film thickness, and impact velocity influences are analyzed. The results demonstrate that, with the impact angle increasing, the variation trends of the crown radius on both sides are opposite. When the film thickness increases, there is a critical film thickness at which the right crown height reaches the maximum. The increasing impact velocity leads to a flow phenomenon transition from non-splashing to splashing and even to a crown. When the impact velocity reaches a certain value, the liquid film on the front side will become unsteady, which makes the crown on this side prone to rupture at the early stage of impact. The bubble deformation during the impact process under different conditions is also discussed, and the patterns of the splashing behaviour under different initial conditions are summarized. [ABSTRACT FROM AUTHOR]

To accurately quantify the interfacial transfer terms in the two-fluid model, the reliable prediction of the interfacial area concentration (IAC) is crucial. The IAC in annular flow, especially the interface between the liquid film and gas core, is particularly important due to its relevance to critical heat flux and reactor operation safety. However, very few experimental and analytical studies have been performed that focus on the IAC of the liquid film in annular flow. In this work, the IAC of the liquid film is measured using a parallel-wire conductance probe for upward annular flow in a 25.4-mm one-dimensional pipe. A total of 25 flow conditions are measured with the range of superficial liquid velocity from 0.15 to 2.00 m/s and the range of superficial gas velocity from 10.0 to 29.6 m/s. The IAC radial profile is obtained from the liquid film time trace measured by the conductance probe, and the accuracy of this method is verified by flow visualization. The effects of the inlet gas and liquid flow rates on the characteristics of the IAC radial distribution as well as area-averaged IACs are analyzed. A new model is developed to predict the IAC radial distribution of the liquid film. The IAC profiles predicted by the model agree very well with the measured IAC profiles for typical annular flow conditions and have a reasonable agreement for the wispy annular flow conditions. [ABSTRACT FROM AUTHOR]

This study aims to improve the measurement accuracy of liquid film thickness using a liquid film sensor with an optical waveguide film (OWF). The measurement principle of employing the OWF is based on the detection of light reflection at the liquid film surface with high spatial resolution. Because the curved surface of the liquid film reflects light and increases measurement error, we propose a signal processing method to remove the error factor in the calculation of the time-averaged thickness. This method requires prediction of the surface curvature, and we numerically investigated the characteristics of the output signal related to the reflected light intensity. The analysis results showed that the effect of the curved surface up to the surface curvature of 5.0 mm−1 was negligible because the liquid film thickness showed good agreement with that of the flat liquid film surface within 7% accuracy. Furthermore, we consider the applicable range of liquid film thicknesses under the operating conditions of boiling water reactors (BWRs). We estimated the surface curvature of the liquid film based on the calculation of the critical Weber number and confirmed that the curvature caused under the BWR operating conditions was covered by the analysis conditions of this study. Therefore, our proposed method for signal processing via the OWF enabled us to improve the measurement accuracy of the time-averaged thickness with respect to the base film thickness by extracting accurate surface curvature data. [ABSTRACT FROM AUTHOR]

The effect of odd viscosity on the instability of liquid film along a wavy inclined bottom with linear temperature variation is investigated. By utilizing the long-wave approximation, the non-linear evolution equation of the free surface is derived. By applying the normal mode method, the linear instability of thin film flow is investigated. With the help of multi-scale analysis methods, the weakly non-linear instability of thin film flow is also investigated. The results reveal that the Marangoni effect caused by non-uniform temperature distribution promotes the instability of the liquid film, while the odd viscosity has a stabilizing effect. In addition, for a positive local inclination angle θ , an increase in bottom steepness ζ inhibits the instability of the liquid film flow. In contrast, with a negative local inclination angle θ , increased bottom steepness ζ promotes the instability of the liquid film flow. The results of the temporal linear instability analysis and the weakly non-linear instability analysis have been substantiated through numerical simulations of the non-linear evolution equations. [ABSTRACT FROM AUTHOR]

The Nb-Mo-Ta-W series refractory high-entropy alloys with composition recombination design were manufactured by laser metal deposition process. The phase structure, defects and microstructure of（NbMoTa）90W10 and（NbMoTaTi）90W10 high-entropy alloys were characterized and analyzed by X-ray diffraction and scanning electron microscope. The tensile properties of the two alloys were tested at room temperature by multifunctional mechanical testing machine. The results showed that both（NbMoTa）90W10 and（NbMoTaTi）90W10 high-entropy alloys are single-phase body centered cubic structures. Ti element forms a "liquid film" at the grain boundaries in Nb-Mo-Ta-W series alloy, which can effectively suppress intergranular cracks. Due to the reduction of metallurgical defects and the lattice distortion effect, the mechanical property of（NbMoTaTi）90W10 high-entropy alloy at room temperature is improved, and the yield strength reaches 1156 MPa.

Controlling the distribution of the abrasive grains on the surface of the grinding tools in an appropriate way is important for improving the quality of grinding processing and meeting the workpiece precision requirements. In the present study, a novel method for the orderly arrangement of abrasive particles is proposed by using the liquid film flow on the surface of the rotating disk as the driving and controlling means for the uniform dispersion and position arrangement of abrasive particles. Computational fluid dynamics (CFD) simulations have been performed to clearly illustrate the trajectories of abrasive particles under the strong influence of liquid film flow on the rotating disk and reveal the effects of fluid flow, disk rotational motion, and the mixture viscosity on the particle distribution. A new abrasive grain arrangement device is designed and fabricated using this novel method. The operating parameters such as liquid volume flow rate, disk rotational speed, and liquid viscosity are adjusted to control the placement of abrasive grains on the surface of the grinding tool. An image processing tool is used to examine and analyze the arrangement results. The experimental results indicated that the application of the liquid film flow on a rotating disk to the abrasive grain arrangement can improve the arrangement of abrasive grains and get rid of the dependence on the template.

Multiphase flow entrainment in natural gas engineering significantly influences the safety and efficiency of oil companies since it affects both the flow and the heat transfer process, but its mechanisms are not fully understood. Additionally, current computational fluid dynamics (CFD) methodologies seldom consider entrainment behavioral changes in pipe elbows. In this article, a verified CFD method is used to study the entrainment behavior, mechanism, and changes in an elbow. The results show that droplet diameter in a developed annular flow follows a negative skewness distribution; as the radial distance (from the wall) increases, the fluctuation in the droplets becomes stronger, and the velocity difference between the gas and the droplets increases linearly. Turbulence bursts and vortices sucking near the wall jointly contribute to droplet entrainment. As the annular flow enters the elbow, the secondary flow promotes the film expansion to the upper and lower parts of the pipe. Droplets re-occur near the elbow exit intrados, and their size is much smaller than those in the upstream pipe. Vortices sucking under low gas velocity play an important role in this process. These findings provide guidelines for safety and flow assurance issues in natural gas production and transportation and bridge the gap between multiphase flow theory and natural gas engineering.

Vibrations profoundly influence the liquid film formed by spray droplets in spray cooling applications. However, understanding heat transfer mechanisms in the non-boiling region under vibrating conditions is limited in the existing literature. This study aims to bridge this gap by numerically investigating the heat transfer performance of spray cooling in non-boiling regions under vibration using the Lagrange-Euler method. To validate the computational fluid dynamics (CFD) model, experimental measurements of spray heat transfer were conducted on a heated vibrating surface test rig. The results demonstrate that the average film thickness (AFT) and average film velocity (AFV) increase at lower frequencies, leading to a decrease in the heat transfer coefficient. Conversely, the AFT decreases at higher frequencies while the AFV remains relatively constant. This reduction in AFT enhances the heat transfer coefficient, resulting in an up to 12% improvement in heat transfer performance. When a larger vibration amplitude is introduced, a higher inertial force acts on the liquid film, causing it to converge towards the centre. Generally, the heat transfer coefficient of spray cooling in the non-boiling region decreases as the vibration amplitude increases.

[Objective]To explore the effect of liquid film on the vegetation and soil physical and chemical properties in saline-alkali land. [Method]Three gradient experiments of liquid film [CK (0 kg/hm 2 ), LF (375. 0 kg/hm 2 ) and HF (562. 5 kg/hm 2 ) were set up on slightly degraded saline alkali land. The effects of different liquid film spraying amount on aboveground vegetation biomass, organic carbon content, soil nutrients and acidity in saline alkali soi were explored. [Result]With the increase of liquid film spraying amount, soil physical and chemical properties showed different trends. Compared with the control, the spraying amount of 562. 5 kg/hm 2 increased soil organic carbon by 7. 79%, total phosphorus content by 111. 11%, aboveground biomass by 65. 3%. Under the condition of 375. 0 kg/hm 2 spraying, the soil total nitrogen exceeded 46. 2% of the control plot. [Conclusion]The use of liquid film significantly increased the aboveground biomass of plants and the storage of soil organic carbon, increased the content of total phosphorus in the soil, and contributed to the improvement of saline alkali soil and the enhancement of carbon sequestration and sink capacity. [ABSTRACT FROM AUTHOR]

The linear temporal instability of the confined curved liquid film formed by a liquid jet impinging on a curved wall has been investigated. The corresponding dispersion relation between the non-dimensional wave growth rate and wave number was derived. The dispersion relation further involves the influences of the local radius of curvature and the azimuthal angle of the liquid film. The dispersion relation could be verified with previous researches, and the optimal wavelength has been verified with experiments. Temporal stability analysis shows that the effects of gas-to-liquid velocity ratio, gas-to-liquid density ratio, the relative thickness of the liquid phase to the gas phase, and azimuthal wave number are similar to previous researches, but the unstable ranges are smaller than that in previous researches. This paper further studied the effects of the local radius of curvature and azimuthal angle of the liquid film. As the local radius of curvature decreases, the instability of confined curved films increases for the given conditions. And both the growth rate and instability range increase with the increase of the azimuthal angle. The solutions would be helpful to understand the atomization process of the liquid film formed by a liquid jet impinging on a curved wall. • The dispersion relation involves the influences of the local radius of curvature and azimuthal angle of the film. • The dispersion relation has been verified with experiments. • As the local radius of curvature decreases, the instability of films increases. • Both the growth rate and instability range increase with the increase of the azimuthal angle. [ABSTRACT FROM AUTHOR]

The present study theoretically investigated the linear instability of a liquid film sheared by gas flow under acoustic oscillations. In this work, the velocity oscillations of the gas are used to approximately characterize the acoustic oscillations, and the ratio of the conduction heat flux to the evaporation heat flux is used to characterize the heat and mass transfer. Considering the much stronger impact of the heat convection than the heat conduction in practical cases, a correction factor is introduced to satisfy the heat flux ratio within a reasonable range. Because of the oscillatory velocity of gas, several unstable regions, involving the KHI region and the parametric instability (PI) region, appear. The impact of the velocity oscillations on the KHI is related to the forcing frequency. Increasing the oscillatory velocity amplitude promotes the KHI when the forcing frequency is large, while the KHI is restrained with the increase in the oscillatory velocity amplitude when the forcing frequency is small. Since the viscous dissipation is enhanced when the forcing oscillations frequency increases, the PI is suppressed. In addition, when the surface tension decreases, the interfacial instability is also promoted. Increasing the gas–liquid density ratio can destabilize the surface. However, the impact of the heat and mass transfer on the interfacial instability is neglectable as the gas–liquid density ratio is large. Furthermore, the heat and mass transfer have a promoting impact on the PI and KHI, while their destabilizing effect on the indentation between unstable regions is greater. It is significant to note that the location of the maximum growth rate would be in the most unstable region. [ABSTRACT FROM AUTHOR]

Incorporating additives to fuel into a piston engine is one strategy used to reduce wear on critical engine parts. The present study aims to experimentally characterize the presence of these additives on a wall after a fuel spray impact under representative Diesel and spark ignition engine conditions. For this purpose, a laser-induced fluorescence technique was implemented on a high pressure, high-temperature vessel. Spectroscopic characterizations of fuels and additives were carried out to design an optical strategy for both engine conditions. Fuel surrogates were chosen to allow the additives to be monitored and to mimic the behavior of commercial fuels. The results obtained for gasoline fuels show that at level of incorporation above 100 ppm the additives reach the surface, demonstrating the effectiveness of the additive use strategy. The results obtained for Diesel cases show that even for a high level of additive incorporation, the thermodynamic conditions lead to a complete evaporation of the additives before impact on the wall, which minimizes the expected effect of these additives on friction reduction. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Oil Crop Sciences is the property of Oil Crops Research Institute of Chinese Academy of Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the liquid film thickness of slug flow in a microchannel was numerically investigated. Particularly, we focused on a flow regime with high Reynolds and capillary numbers; these dimensionless number were independently modified to investigate their effect on the liquid film thickness. The results based on the turbulence model confirmed that the liquid film thickness tends to remain constant in the low Reynolds number region; whereas it sharply increases when the Reynolds number reaches a certain value. However, this increase stops once a certain value of Reynolds number is reached, and the liquid film thickness tends to remain constant in the high Reynolds number flow regime. These results tend to agree with the experimental results from previous studies. Moreover, the liquid film thickness calculated under the laminar condition was similar compared to that based on the turbulence model, except in the high Reynolds number region. Under the laminar condition, the liquid film thickness in the high Reynolds number region did not converge to a constant value but kept increasing. The results of this study suggest that the shear stress acting on the bubble interface, which appears in the form of Reynolds stress, seem to prevent the liquid film thickness from increasing.

Liquid and ionic transport through nanometric structures is central to many phenomena, ranging from cellular exchanges to water resource management or green energy conversion. While pushing down toward molecular scales progressively unveils novel transport behaviors, reaching ultimate confinement in controlled systems remains challenging and has often involved 2D Van der Waals materials. Here, we propose an alternative route which circumvents demanding nanofabrication steps, partially releases material constraints, and offers continuously tunable molecular confinement. This soft-matter-inspired approach is based on the spontaneous formation of a molecularly thin liquid film onto fully wettable substrates in contact with the vapor phase of the liquid. Using silicon dioxide substrates, water films ranging from angstrom to nanometric thicknesses are formed in this manner, and ionic transport within the film can then be measured. Performing conductance measurements as a function of confinement in these ultimate regimes reveals a one-molecule thick layer of fully hindered transport nearby the silica, above which continuum, bulk-like approaches account for experimental results. Overall, this work paves the way for future investigations of molecular scale nanofluidics and provides insights into ionic transport nearby high surface energy materials such as natural rocks and clays, building concretes, or nanoscale silica membranes used for separation and filtering. [ABSTRACT FROM AUTHOR]

We apply the Painlevé test for the Benney and the Benney–Gjevik equations, which describe waves in falling liquids. We prove that these two nonlinear 1 + 1 evolution equations pass the singularity test for the travelling-wave solutions. The algebraic solutions in terms of Laurent expansions are presented. [ABSTRACT FROM AUTHOR]

In this work, the dynamic behavior of linear and nonlinear waves propagating at the separating surface between two thin layers of viscous Newtonian fluids is studied in the presence of the effect of insoluble surface surfactant. The two liquids are confined between two infinite rigid parallel plates and assumed to have different densities and viscosities. The equations of evolution for surface-wave elevation and concentration of surfactant are derived using the lubrication approximation. In the linear stage, by utilizing the normal mode approach, we have derived the dispersion relation that relates the wave angular frequency to the wave number and other parameters that is solved numerically to inspect the influences of some selected parameters on the stability criteria of the fluid flow. Also, analytical expressions for the growth rate as well as its maximum value with corresponding wave number are obtained in the special case of long-wave limiting. It is concluded that the Marangoni number Ma has acquired a significant stabilizing influence on the fluid flow, whereas the inverse of the slippery length of substrate plate β , resorts to the destabilize the motion of the interfacial waves. Consequently, both of the Marangoni number and the substrate slippy coefficient can be utilized to control the film flow regime, where they preserve the film laminar flow and tend to prevent the film breakdown. These can be useful in many industrial applications such as coating processes, heat exchangers, cooling microelectronic devices, chemical reactors, food processing, thermal protection design of combustion chambers in rocket engines and operation of Laser cutting and heavy casting production processes. [ABSTRACT FROM AUTHOR]

In a laboratory, the spreading of a liquid film over polymer plates with various sizes of microdimensions was studied. The results suggested that the profile height affects the surface wettability. This study presents both a qualitative and quantitative comparison of the degree of wettability of the plates under consideration. It was revealed that a plate with a height of 0.5 mm had better wettability compared to that of a smooth plate at all values of irrigation density. At the same time, a plate with a profile height t = 1.2 mm was wetted better than a smooth sample at an irrigation density of U = 0.61 m3/(m·h). At irrigation densities above U = 0.78 m3/(m·h), the degree of wettability of this sample was found to be the highest. [ABSTRACT FROM AUTHOR]

With the downscaling of semiconductor feature size, single wafer wet etching has shown better within-wafer and wafer-to-wafer uniformity. According to previous research and analysis, liquid film thickness has a close relationship with etch loss, and numerical simulations have been applied to calculate liquid film thickness with fixed nozzle dispensing. This study investigated liquid film thickness with scanning nozzle processing and a modeled aqueous tetramethylammonium hydroxide (TMAH) poly etching method. A modified shallow water equation was used to calculate the liquid film thickness under nozzle scanning conditions. Additionally, the liquid film thickness and liquid velocity were coupled with a chemical reaction kinetic model to calculate the TMAH poly etching reaction rate on the wafer surface. Scan dispensing etch loss was calculated by integrating the reaction rate. Both the experimental and simulation results showed that the scan speed can affect within-wafer etch loss profile and that a fast scan speed could increase etch loss in wafer donut area. The simulation model could be a predictive tool for improving within-wafer etching profile. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) numerical simulation of a two-phase flow liquid/liquid is performed in a rectangular microchannel with a T-junction. The volume of fluid (VOF) method was used under ANSYS Fluent to capture the interface between the two phases. The dynamic mesh adaptation technique together with the assumption of symmetry plane helps us to reduce the computational cost. The study focuses on the flow patterns and hydrodynamics of plugs. So, the influence of the flow rate ratio q , the capillary number Ca , and the viscosity ratio on the liquid film, the plug/droplet shape, and velocity are examined here. Particularly, the plug/droplet lengths predicted by the simulation show good agreement with the experimental and correlation available in the literature. The results revealed six distinct flow patterns by dispersing water in a continuous phase of silicone oil. By decreasing the flow rate ratio as well as the viscosity ratio, the liquid film thickness increases in the corners and side planes. In turn, this greatly impacts the liquid film velocity and the plug velocity. Furthermore, capillary number (based on two-phase flow velocity) is also shown to have a greater impact than viscosity ratio and flow rate ratio on plug shape, with the curvature radii of the tail always larger than the front one. [ABSTRACT FROM AUTHOR]

The oblique impact of microscale water droplets on liquid film is numerically investigated. Two-phase flow problems are simulated using three-dimensional incompressible Navier-Stokes equations, and the level-set method is employed for capturing the gas-liquid interface. The numerical model is verified using experimental results from a normal and oblique impact via the qualitative comparison of crown profile features and quantitative contrast of the crown height and radius varying with time. The article discusses the influence of tangential impact velocity, water film thickness, Reynolds number, and Weber number on the shape characteristics, tangential momentum, and kinetic energy of the annular crown. The results show that the decreasing momentum in the tangential direction can be divided into three clear stages: rapid decrease, slight increase, and continuous decrease. In addition, film thickness and Weber number have significant effects on the momentum decay rate. [ABSTRACT FROM AUTHOR]

In this study, an AMR-PLIC-HF method is proposed and implemented by GPU parallel computing based on CUDA programming language and NVIDIA GPU. The present method improves the computation efficiency without compromising the accuracy and conservation of the volume. To satisfy the requirements of stencil points of the PLIC-HF method, an extended stencil computation method based on the tree-based AMR method is proposed and implemented. The Weakly Compressible Scheme (WCS) is used in the present work as a fluid solver. An evolving pressure projection method is adopted to suppress the oscillation induced by the reflection of acoustic waves. The Langmuir model is introduced into the solver to calculate surfactant transport and the Marangoni effect caused by the gradient of the interface concentration of the surfactant. The single vortex flow results verify the accuracy of the AMR-PLIC method. A single bubble rising problem with two different physical property settings is simulated. The results show good agreement with the results given by incompressible solvers. This verifies the accuracy of the two-phase flow solver including the AMR-PLIC-HF method and the WCS. The generation and rupture of liquid film by a single bubble freely rising to an interface is simulated by the present solver with a 1024 × 2048 AMR grid as the finest resolution. This simulation successfully calculates surfactant transport and the Marangoni effect. [ABSTRACT FROM AUTHOR]

Instability features of a liquid film flowing along an inclined wall for different corrugated amplitudes have been studied with the long wave approximation methods. It has been derived in the rectangular and orthogonal curve coordinates. Results reveal that the present theoretical calculations coincide better with the previous experimental data for the small Reynolds number cases. The liquid film thickness on a small corrugated wall is consistent with that of a flat wall while it would be promoted by the larger corrugated amplitude cases. Besides, it illustrates that the small corrugated surface amplitudes have a limited impact on the flow neutral stability. The larger surface corrugated amplitude cases suppress the surface instability when the surface Taylor-Rayleigh instability is not induced. The corresponding suppression impact would be more pronounced when the inclined angle becomes smaller. [ABSTRACT FROM AUTHOR]

For the purpose to solve the problem that it is difficult for solar cells to maintain stable electrical output under high concentration ratio, this paper studies the method of combining spray cooling and solar cells. The objective of this paper is to study the effect of liquid film generated during spray cooling heat transfer on the performance of solar cells. In this paper, the model was built by ANSYS, compared with jet cooling, the solar cell integrated spray cooling has the superiority of the performance. When the angle of the nozzle is tangent to the solar cell and the nozzle height ranges from 4 mm to 6 mm, the solar cell can obtain the optimal electrical performance. Properly increasing the flow rate enables the distribution of the liquid film on the solar cell more uniform, so that the uniformity of the temperature can be better maintained. Considering the electrical properties and temperature uniformity, the combination of solar cell and spray cooling is more suitable under concentration ratio of 800. Solar cell can not only obtain more than 20W/cm2 of electrical energy, but also the temperature difference (Tsurface,max- Tsurface,min) can be kept below 10K. Above results have implications for cooling methods of solar cells in the field of high concentration photovoltaic. [ABSTRACT FROM AUTHOR]

When oil droplets impact a solid surface for oil-air lubrication, they may spread out to produce a thin oil layer on the surface, which serves as a significant source of lubrication. A test rig was constructed in this research to observe the spreading behavior of oil droplets impacting surfaces from both frontal and lateral views. From the frontal view, laser-induced fluorescence techniques are used to measure the thickness of the oil layer quantitatively during the spreading of oil droplets. While the lateral view can observe the shape evolution of the droplets. Oil droplet spreading patterns on the sheet with dry surfaces and with different thin liquid film thicknesses were studied, and the effect of viscosity and the thickness of the thin liquid film on spreading radius and spreading thickness is considered. The experimental findings demonstrate that the maximum spreading factor, the spreading central layer thickness, and the apparentness of retraction all increase as viscosity increases. The retraction is obviously impacted by thin liquid films, and the retraction weakens as the thin liquid film thickness increases. [ABSTRACT FROM AUTHOR]

It is important to improve the thermal efficiency and reduce the harmful exhaust emissions of the direct-injection spark-ignition engine. However, this engine has problems such as the emission of particulate matter, including soot, from pool fire with luminous flames. Pool fire is caused by the thermal decomposition of a liquid film, which is created by fuel spray impinging on a piston surface. An understanding of liquid film formation process is important to reduce particulate matter. The purpose of this investigation was to evaluate the effects of injection pressure on fuel spray impingement and liquid film formation process, under engine motoring conditions, using the laser-induced fluorescence method. The fuel consisted of isooctane, 1-octanol and rhodamine B. 1-Octanol was the solvent for rhodamine B, which was illuminated with a neodymium-doped yttrium aluminum garnet laser, causing it to emit red fluorescence at a wavelength of 580 nm; the second harmonic of the laser is at 532 nm. Liquid film images were captured using a high-speed camera. Using image processing, the liquid film area, thickness and mass were estimated. It was found that increasing injection pressure increased the liquid film area, thinned the film and decreased the mass of fuel that remained. In total, 35.6% and 32.5% of the injection mass remained on the piston surface at an injection pressure of 5 and 13 MPa, respectively. In addition, the in-cylinder flow affected the liquid film formation process, stretching the film in the direction of the flow. [ABSTRACT FROM AUTHOR]

The impact of water and 1-ethyl-3-methylimidazolium acetate ([EMIm]Ac) drops on [EMIm]Ac ionic liquid film was studied. The hydrodynamics of the impact of drops on a water liquid film were compared. A higher Weber number contribute to a larger crown rim diameter and height. The variation trend of the crown rim diameter and height with the liquid film thickness differs much according to the drop and film properties. The crown rim diameter and height have an opposite variation trend with the increasing liquid film temperature. The crown rim diameters with different droplet and liquid film properties were almost the same at the early stage of impact of approximately 4 ms, and then the difference became larger at a later stage. The shape of the generated liquid crown was more regular for drops impact on ionic liquid film. The water droplet impact on a water film has the largest liquid crown rim diameter and height, while the ionic liquid droplet impact on the ionic liquid film has the lowest.

As the pressure and temperature of natural gas pipelines decreases during operation, water and condensate accumulates form in the low areas of the pipelines, affecting the operational efficiency of the pipelines and even corroding them. The critical gas velocity is a key factor in predicting liquid loading onset in the pipeline, so that appropriate measures can be taken in advance and hazards can be reduced. This paper proposes a model for predicting pipeline liquid loading onset based on the liquid film and wall shear stress of zero, and applicable to different pipe diameters and different inclination angles. This model provides a more simplified and comprehensive prediction of pipeline fluid loading than other models with complex calculations. The critical gas velocity in this model is a function of the liquid holding rate rather than the liquid film thickness, and the critical gas velocity prediction in a phase-inclined pipe is carried out by an improved Belfroid angle correction term. The experimental data, field data and seven models in the published literature were compared and validated, and the errors were judged. The results showed that the new model outperformed the other models in terms of absolute mean error at full inclination angle, and was able to predict the pipeline liquid loading accurately.

An engineering model of heat transfer through a turbulent falling liquid film for a condensing (or evaporating) vapor flow is suggested. A simple correlation for the eddy diffusivity, based on the Barenblatt's hypothesis of incomplete similarity, is employed for description of momentum and heat transfer across the liquid film. An equation for the dimensionless heat transfer coefficient at a substantial interfacial shear stress is obtained and successfully validated by experimental data available in open literature. • Heat transfer through a liquid film for a condensing vertical vapor flow is modeled. • The eddy diffusivity across a liquid film is calculated by Barenbatt's equation. • The heat transfer model accounts for an effect of the interfacial shear stress. • The model is validated by found experimental data for water vapor condensation. [ABSTRACT FROM AUTHOR]

Liquid nanofilm is used in industrial applications, such as heat exchangers, water desalination systems, heat pumps, distillation systems, cooling systems, and complex engineering systems. The present work focuses on the numerical investigation of the condensation of falling liquid film containing different types of nanoparticles with a low-volume fraction. The nanofluid film falls inside a heat exchanger by mixed convection. The heat exchanger is composed of two parallel vertical plates. One of the plates is wetted and heated, while the other plate is isothermal and dry. The effect of the dispersion of the Cu or Al nanoparticles in the liquid on the heat exchange, mass exchange, and condensation process was analysed. The results showed that the heat transfer was enhanced by the dispersion of the nanoparticles in the water. The copper–water nanofluid presented the highest efficiency compared to the aluminium–water nanofluid and to the basic fluid (pure water) in terms of the heat and mass exchange. [ABSTRACT FROM AUTHOR]