Physics of Fluids最新文献

{"title":"Electro-hydrodynamics study of double emulsion droplet formation in a double Y-shaped channel","authors":"Qianwen Yang, Zhaohui Wang, Yaohui Zhao, Feng Zhang, Quanjie Gao","doi":"10.1063/5.0223426","DOIUrl":"https://doi.org/10.1063/5.0223426","url":null,"abstract":"Although there have been more studies on droplet formation under the control of electrostatic field in recent years, the studies on the relationship between composite droplet formation and electrostatic field are fragmented. In order to analyze the effect of electrostatic field on composite droplet formation, this paper numerically investigates the electro-hydrodynamics of the double emulsion in a double Y-shaped microchannel and experimentally verifies the applied phase interface capture method. Calculations are carried out using a model coupled with the phase field method and electrostatic field to analyze the interfacial evolution of double emulsions under different electric field strengths and to quantitatively study the droplet formation process. Four flow regimes different from previous studies were found: dripping regime, jetting regime, threading regime, and jetting-dripping transition regime, among which the formation frequency ( f ) of double emulsion droplets under the short jetting regime was up to 769 Hz. The eccentricity (ε) of droplets under the dripping regime was the smallest, with ε of 0.2, the coefficient of deformation (Defm) of the middle phase droplets was minimized to 0.05. It is observed that there is a linear relationship between Cam/Cao and CaE in the dripping regime, with the generation of multi-core double emulsion droplets. When Cam/Cao is greater than 14, the flow regime of the double emulsion in the channel is always threading regime, no matter how CaE is changed.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"22 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental study on flow/noise of a circular cylinder with concentric/eccentric microperforated ring fairings","authors":"Tao Lu, Yong Li","doi":"10.1063/5.0225614","DOIUrl":"https://doi.org/10.1063/5.0225614","url":null,"abstract":"The effects of microperforated ring fairings on the flow and noise of a circular cylinder were investigated experimentally at Reynolds number based on the cylinder diameter (D) ranging between 1.3 and 2.6 × 104. The fairings were installed either concentrically or eccentrically, and the parameters investigated are the perforation rate σ (11.8%–34.6%), the clearance ratio δ/D (0.1–0.3), and the deflection angle θ (0°–180°). The noise was measured using far-field microphones, and flow characteristics were tested by the particle image velocimetry (PIV) and a dynamic balance. The acoustic results showed that the aerodynamic noise of the cylinder generally decreases with the increase in the perforation rate σ and the clearance δ. The maximum noise reduction at the fundamental vortex shedding frequency can reach 25 dB when arranged concentrically at δ/D = 0.3 and σ = 34.6%. Under the same perforation and clearance, the eccentric arrangement at θ = 60°–120° significantly improves the noise control performance. Flow visualization by PIV test demonstrated that the perforated fairing effectively controls the unsteady flow downstream of the cylinder and attenuates the large-scale vortex shedding, resulting in the noise reduction. The force measurement results showed that unsteady lift coefficient is significantly reduced, but the mean drag coefficient of the cylinder together with the fairings is generally higher than the bare cylinder. Nevertheless, the increment in drag coefficient can be lessened by eccentrically arrangement of fairings at deflection angle between θ = 60°–120°.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"63 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of viscosity on wind-driven gravitation waves","authors":"C. Chaubet, N. Kern, M. A. Manna","doi":"10.1063/5.0221941","DOIUrl":"https://doi.org/10.1063/5.0221941","url":null,"abstract":"We address the question of how viscosity impacts the growth of gravitation waves, such as those on the ocean, when they are driven by wind. There is so far no general rigorous theory for this energy transfer. We extend Miles' approach [J. W. Miles, “On the generation of surface waves by shear flows,” J. Fluid Mech. 3, 185–204 (1957)], using the same logarithmic wind profile, to incorporate bulk viscosity and derive modified growth rates. Exploiting the fact that water waves fall into the “weak viscosity” regime, we produce analytical expressions for the growth rate, which we solve using the numerical method proposed by Beji and Nadaoka [“Solution of Rayleigh's instability equation for arbitrary wind profiles,” J. Fluid Mech. 500, 65–73 (2004)]. Our results confirm that corrections to the growth rates are significant for wavelengths below a meter, and for weak to modest wind strengths. We show that all wave growth is suppressed, due to viscous effects, below a critical wind strength. We also show that the wave age corresponding to a developed sea is reduced by viscosity. We quantitatively characterize the zones, in terms of wind strength and wavelength, for which the wave growth is suppressed by viscosity.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"31 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pressure wavelet analysis of pitching oscillating airfoils in tandem configuration at low Reynolds number","authors":"Kamran Ghamkhar, Abbas Ebrahimi","doi":"10.1063/5.0228652","DOIUrl":"https://doi.org/10.1063/5.0228652","url":null,"abstract":"In this paper, the flow field around a tandem arrangement of two identical oscillating NACA (National Advisory Committee for Aeronautics) 0012 airfoils was investigated using the continuous wavelet transform. Wind tunnel experiments were conducted on a test stand that provided a wide range of sinusoidal pitching motion with frequencies up to 10 Hz. This study aims to explore the flow physics of the tandem airfoils that oscillate with independent reduced frequencies. For this sake, experiments were performed at a reduced frequency of 0.15 for the front airfoil and five different reduced frequencies for the rear airfoil, ranging from 0.05 to 0.3. The chord-based Reynolds number was 6 × 104, and the horizontal distance between airfoils was equal to one chord length. The unsteady surface pressure was measured, and the wavelet transform was employed to analyze the pressure fluctuations. Findings indicate that the presence of the rear airfoil in the wake of the front airfoil prevents the formation of the laminar separation bubble. Also, the ratio of upstream/downstream airfoil reduced frequencies appears as one of the dominant frequencies of pressure fluctuations on the rear airfoil. Furthermore, when the reduced frequency ratio of the airfoils is lower than one, the normal force on the rear airfoil is often less than that experienced by an isolated single airfoil. Specifically, at equal reduced frequencies of 0.15 for both upstream/downstream airfoils, the maximum value of the normal force coefficient on the rear airfoil decreases by 30% compared to the single airfoil.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"12 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical investigation on Al2O3 droplet spreading and its prediction model exploration based on Harris Hawks optimization-generalized regression neural network in stereolithography","authors":"Weiwei Wu, Jiangyuan Fu, Minheng Gu, Shuang Ding, Yanjun Zhang, Xinlong Wei","doi":"10.1063/5.0229824","DOIUrl":"https://doi.org/10.1063/5.0229824","url":null,"abstract":"The laying process is crucial in using stereolithography (SL) for molding Al2O3 parts. However, most studies focus on the laying process of macroscopic slurry; there needs to be more focus on microscopic exploration. Studying from a microscopic perspective can help us understand the influence of its parameters on droplet spreading and infer the macroscopic changes of the slurry based on the changes in droplet spreading to understand why parameters cause macroscopic changes in the slurry. A pseudopotential model based on Sisko's non-Newtonian behavior in lattice Boltzmann method is proposed to study the spreading process of droplets and validated using wetting characteristics. The previous layers of the platform and the printed solid are investigated to understand the effect of laying velocity on the spreading diameter, the thickness, and the both-sided contact angles. The results indicate that a higher laying velocity leads to a larger spreading diameter, a smaller spreading thickness, and a smaller left contact angle. However, it also increases the contact angle difference between the two sides, leading to uneven slurry. The droplet spreads more unevenly when the previous laying surface is the printed solid. At the same velocity, the droplet spreads with a smaller diameter, thicker thickness, and larger contact angle on the printed solid surface. Therefore, a higher laying velocity in the SL laying process is not recommended, especially when the front layer is a printed solid. Although a higher laying velocity will increase the laying area and reduce laying time, it will cause protrusions at the front edge, and inconsistent laying thickness of the same layer will affect the following photosensitive curing process. The Harris Hawks optimization-generalized regression neural network algorithm is proposed and compared with other common artificial intelligence algorithms to predict the spreading parameters. The comparison shows that the proposed algorithm provides a more stable and accurate prediction of spreading parameters.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"43 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nonlinear three-dimensional modeling for encapsulated microbubble dynamics subject to ultrasound","authors":"Wenbin Wu, Yong Liu, Warren Smith, Qianxi Wang","doi":"10.1063/5.0222631","DOIUrl":"https://doi.org/10.1063/5.0222631","url":null,"abstract":"Encapsulated microbubbles (EMBs) stabilized by thin coatings have been used as contrast agents for ultrasound sonography as well as having been demonstrated as a promising new technology for targeted drug delivery. The dynamics of EMBs is three-dimensional (3D) because EMBs within micro-vessels inevitably interact with boundaries, but the theoretical and numerical studies are limited to spherical, weakly non-spherical, and/or axisymmetric EMBs. Here, we have developed physical, mathematical, and numerical models for nonlinear 3D EMB dynamics. The liquid flow is evaluated using the boundary integral method. The EMB coating is modeled as a thin viscoelastic shell including stretching, bending, and shear effects and simulated using the finite element method. These models are coupled through the kinematic and dynamic boundary conditions at the interface. The model is in good agreement with the Hoff equation for spherical EMBs and the asymptotic theory for weakly non-spherical deformation of EMBs. Using this model, a numerical study for EMB dynamics near a rigid boundary subject to an ultrasonic wave is performed. The migration, non-spherical oscillation, resonant oscillation, and jetting of EMBs are displayed and analyzed systematically. If the ultrasound wave is strong, a high-speed liquid jet forms at the final stage of the collapse, orientated between the directions of the wave and toward the wall. The EMB jet is weaker and slower and has less momentum, as the non-spherical deformation of the coating and the jetting are suppressed by the viscoelastic property of the coating. If the ultrasound is not strong, the EMB remains spherical for many cycles of oscillation but the EMB undergoes resonant oscillation and becomes significantly non-spherical after several oscillation cycles, when the wave frequency is equal to its natural frequency. The numerical capability has the potential to be developed for the optimization of sonography or drug delivery.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"4 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal mixing and structure of the jet in swirling crossflow","authors":"Zhengzhe Fang, Chi Zhang, Yushuai Liu, Tianheng Gao, Cunxi Liu, Xin Xue, Wei Gao, Gang Xu, Junqiang Zhu","doi":"10.1063/5.0222782","DOIUrl":"https://doi.org/10.1063/5.0222782","url":null,"abstract":"The dilution zone in modern aero-engine combustors is characterized by a strong swirling mainstream with weak transverse jets. This characteristic brings new challenges in homogenizing the temperature distribution at the combustor exit. Therefore, it is imperative to understand the temperature penetration and mixing process of the jet in swirling crossflow (JISCF). This investigation provides new insight in the temperature mixing process for a JISCF in nozzle exit diameter (D) at 7.4, 10.7, and 14 mm and jet to mainstream velocity ratio (VR) from 2.0 to 6.6. The temperature mixing process was measured in a specially designed optical assessable three-dome model gas turbine combustor by planar 1-methylnaphthalene (1-MN) tracer laser-induced fluorescence thermometry. A detailed quantitative measurement of temperature distribution is achieved through the spectral red shift in the fluorescence of 1-MN as the temperature increase. This diagnostic was employed to provide the first two-dimensional temperature distribution for the JISCF. The results showed that the swirling crossflows induce strong spanwise thermal advection, forming secondary low-temperature regions downstream. Generally, the flow structure and mixing process are governed by the interaction of jet and swirling flow. The jet flow parameters, including velocity ratio and diameter, changed the flow structures by changing the interaction between jet and swirling flow. Statistical results and proper orthogonal decomposition (POD) analyses showed a strong anisotropic mixing process in the downstream of the jet.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"70 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cement slurry penetration behavior of swirl grouting technology","authors":"Weiqun Liang, Xiaobin Chen, Lubo Tang, Jiasheng Zhang, Xinxin Zhang, Fantong Lin, Jun Cheng","doi":"10.1063/5.0225944","DOIUrl":"https://doi.org/10.1063/5.0225944","url":null,"abstract":"Traditional pressure grouting technology operates under steady pressure conditions, causing the grout to easily flow along preferential pathways. This results in uneven grout penetration and increased economic costs. This study proposes swirl grouting technology, which effectively improves this problem. To verify the effectiveness of swirl grouting, a fan-shaped blade tool was also proposed. The grout penetration performance was investigated through experimental studies. The length, width, height, weight, and uniformity of the grouted bodies produced by the swirl grouting method were compared with those produced by the steady pressure grouting method. Then, the mechanisms of swirl grouting were analyzed through transparent disc visualization experiments. The results demonstrated that, at different water–cement ratios, the swirl device increased the penetration length in the X, Y, and Z directions by 43.3%, 27.8%, and 45.8%, respectively, compared to the conventional straight device, and by 57.3%, 39.4%, and 55.6%, respectively, compared to the fan blade device. Moreover, the swirl device increased the weight of the grouted stone body by 54.9% compared to the conventional straight device and by 91.0% compared to the fan blade device, significantly enhancing filling efficiency. The uniformity coefficient of the swirl device permeation decreased by 56.6% and 51.0%, respectively, compared to the conventional straight device and the fan blade device, resulting in a more uniform grout distribution. The transparent disc visualization experiment further revealed the advantage of the swirl device in promoting the migration of fine particles, with a significant increase in average penetration distance and a penetration shape closer to a regular circle. The rotating flow path of the swirl device imparts additional rotational momentum and multidirectional penetration capabilities. The resulting turbulence accelerates the mixing of grout with the soil matrix, facilitating the migration of fine particles, expanding flow channels, and reducing flow resistance. This combination of effects enhances penetration efficiency and reduces energy loss. This study offers significant practical application value for improving engineering quality, construction efficiency, and reducing costs.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"188 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Capillary-driven migration of droplets on conical fibers","authors":"Yixiao Mao, Chengxi Zhao, Kai Mu, Kai Li, Ting Si","doi":"10.1063/5.0226483","DOIUrl":"https://doi.org/10.1063/5.0226483","url":null,"abstract":"A droplet placed on a hydrophilic conical fiber tends to move toward the end of larger radii due to capillary action. Experimental investigations are performed to explore the dynamics of droplets with varying viscosities and volumes on different fibers at the microscale. Droplets are found to accelerate initially and subsequently decelerate during migration. A dynamic model is developed to capture the dynamics of droplet migration, addressing the limitations of previous equilibrium-based scaling laws. Both experimental results and theoretical predictions indicate that droplets on more divergent fibers experience a longer acceleration phase. Additionally, gravitational effects are pronounced on fibers with small cone angles, exerting a substantial influence on droplet migration even below the capillary scale. Moreover, droplets move more slowly on dry fibers compared to those prewetted with the same liquid, primarily attributed to increased friction. The experiments reveal the formation of a residual liquid film after droplet migration on dry fibers, leading to considerable volume loss in the droplets. To encompass the intricacies of migration on dry fibers, the model is refined to incorporate a higher friction coefficient and variable droplet volumes, providing a more comprehensive depiction of the underlying physics.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"16 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Preparation and characterization of high-stability gel foam for fracture plugging in reservoirs","authors":"Jingyu Zhang, Binfei Li, Yan Xin, Boliang Li, Mengyuan Zhang, Hao Wang, Shuhao Zhang, Hang Zhang, Xinliang Gu","doi":"10.1063/5.0223975","DOIUrl":"https://doi.org/10.1063/5.0223975","url":null,"abstract":"A high-stability gel foam is successfully prepared by forming a gel structure in the liquid film using polymer and crosslinker. The foaming properties, gel characteristics, foam stability, and microstructure of the high-stability gel foam are systematically studied. Although increasing the viscosity of the liquid film reduces the foam volume, it significantly enhances the foam stability. Considering the foaming properties, gel characteristics, and economic benefits, the optimal formulation of the gel foam system is determined to be 0.8% surfactant, 0.3% hydroxypropyl guar gum (HPG), and 0.2% organic titanium crosslinker (ATC). Microstructural analysis revealed that, compared to water-based and polymer foams, gel foam has smaller bubble sizes, lower drainage rates, and slower coarsening rates. This improvement is mainly attributed to the increased viscosity and thickness of the liquid film after gel and the formation of a three-dimensional network structure. Water loss rate experiment shows that the foam stability is stronger when the liquid film has certain viscosity and elasticity to resist external disturbances. However, higher viscosity and film strength do not necessarily result in better foam stability. The final water loss rate of the gel foam after being placed at 100 °C for 10 h is 74.45%, much lower than that of other higher-strength gel foams (greater than 99%). Fracture plugging experiments demonstrated that the plugging rate of gel foam is high (80%), whereas water-based foam achieved only 37.5%. The gel foam can effectively plug fractures and expand the swept volume, showing great potential for improving oil reservoir recovery.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"11 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}