Physics of Fluids最新文献

{"title":"Broad tunability of core size and number in core-shell compound droplets via tip positioning in coaxial capillary","authors":"Shuai Yin, Haoyu Jiang, Keping Yan, Yi Huang, Yanmei Jiao, Xiaotian Peng, Hao Peng","doi":"10.1063/5.0286654","DOIUrl":"https://doi.org/10.1063/5.0286654","url":null,"abstract":"Core-shell compound droplets play a crucial role in various fields such as materials science, biomedicine, and food technology, where their size and structure are pivotal for functionality. This study investigates the formation of core-shell compound droplets using a coaxial capillary device. By adjusting the inner channel tip from a retracted to an extended position relative to the outer tip, we trigger a transition of droplet formation to the unconfined state. This enables precise control over an ultra-broad range of inner droplet sizes and numbers (radius ∼0.3–2 mm (channel size ∼1 mm), core number ∼1–46), overcoming dimensional limitations imposed by the channel of a conventional device to the droplet size. Force analysis and model predictions reveal the roles of the forces involved in the droplet formation processes and the regime transitions. As the relative positions of the inner and outer channel tips is varied, dimensionless number analysis and particle image velocimetry experiments reveal a fundamental transition in the inner droplet formation mechanism from a shear-dominated pinch-off to a gravity-driven detachment. Especially when utilizing the mismatch between the core formation, the controlled deviation between the core size within one compound droplet is achieved (diameter ratio ranging from 1.2 to 1.7). This work provides novel insights into manipulating compound droplet structures across applications.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147382097","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":"The pinch-off regimes of confined interface vibration inkjet printing","authors":"Junyi Wu, Ganggang Ni, Xuan‐Wen Chen, Haining Zhang, Weiwei He, Yirong Feng, Yanzhen Zhang, Dege Li, Hua Wang","doi":"10.1063/5.0291259","DOIUrl":"https://doi.org/10.1063/5.0291259","url":null,"abstract":"This study combines experimental analysis with numerical simulation to systematically investigate the formation and pinch-off mechanisms of liquid columns in the process of confined interface vibration inkjet printing. Two typical droplet pinch-off regimes are identified: (i) the second-extrusion pinch-off regime and (ii) the second-retraction pinch-off regime. In the second-extrusion pinch-off regime, the interface forms a continuous liquid column during the second-retraction phase, which subsequently pinches off and generates droplets during the second-extrusion phase. In contrast, the second-retraction pinch-off regime involves the rapid formation and pinch-off of the liquid column during the second-retraction phase, resulting in earlier droplet generation. The results indicate that the occurrence of these two regimes is significantly influenced by the amplitude of the excitation waveform and the viscosity of the continuous phase. Furthermore, based on extensive experimental and numerical data, a parameter space diagram was constructed using the Weber number and the Ohnesorge number, which clearly delineates the controllable regions for different droplet formation regimes.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147912256","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":"<i>In situ</i> surfactant generation via saponification in alkali-assisted steam flooding for heavy oil recovery","authors":"Chen Luo, Huiqing Liu, Hassan Hassanzadeh, Yue Pan","doi":"10.1063/5.0280468","DOIUrl":"https://doi.org/10.1063/5.0280468","url":null,"abstract":"This study explores alkali-assisted steam flooding as an effective approach for enhancing oil recovery in heavy oil reservoirs with high acid content. This method eliminates the need for costly surfactants by generating soap in situ. The research identifies naphthenic acids as the dominant acidic components in crude oil, with a double bond equivalent value of 3 or 4. Upon reacting with the sodium hydroxide (NaOH) solution, the interfacial tension decreased to ∼10−2 mN/m, and the acid–base reaction produced soap, altering the rock's wettability from oil-wet to water-wet. The emulsion viscosity was reduced with NaOH at an oil–water ratio of 3:7. Alkali-assisted steam flooding demonstrated that after the first alkali injection, the water cut was controlled, leading to a more than 10% increase in oil recovery. Alternating steam and alkali injections further improved the saponification reaction, resulting in a noticeable reduction in emulsion droplet diameter in the recovered oil samples, with most droplets concentrated in the 4–10 μm range. The shift in droplet diameter distribution indicates a transition from an initially thermally dominated emulsification process to a more stable emulsification system driven by alkali-induced interfacial activity. This study provides valuable insights into the mechanisms of alkali-assisted steam flooding for enhancing recovery in high-acid heavy oil reservoirs.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147915340","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":"On the injection of surfactant into the turbulent boundary layer in low Reynolds number flows","authors":"Xin Zheng, Xinyu Peng, Guo-Yang Zhang, Yi-Ming Hu, Chao Wang, Yue Wang, Yuke Li, Dennis A. Siginer","doi":"10.1063/5.0276473","DOIUrl":"https://doi.org/10.1063/5.0276473","url":null,"abstract":"The effect of slit injection of a surfactant solution on the flow characteristics of the boundary layer on a flat plate in low Reynolds number (Re&amp;lt;20 000) flows is studied experimentally. The velocity distribution at 10 and 20 times the injection slit width (Lc) away from the slit was measured by particle image velocimetry (PIV). The effects of the concentration and the injection flow rate of the polymeric solution on the flow characteristics of the boundary layer at low Reynolds numbers were discussed, through the comparison of the local velocity and velocity fluctuation at different surfactant concentrations and the injection velocity at the slit. Results show that within the studied concentration and injection velocity range, the drag reduction is greatest at a polymer concentration of 50 ppm. As the concentration increases, the drag reduction effect gradually decreases. Furthermore, the injection of the polymer solution has a certain suppressive effect on the turbulent kinetic energy of the boundary layer, especially the velocity fluctuations perpendicular to the wall. Appropriate injection concentrations can also suppress local Reynolds shear stresses in the boundary layer.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147904642","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":"Establishing Hemodynamic Convergence Framework for Coronary Digital Twins Under Realistic Dynamic Heart Rates.","authors":"Nusrat Sadia Khan, Cyrus Tanade, Justen Geddes, Amanda Randles","doi":"10.1063/5.0287796","DOIUrl":"10.1063/5.0287796","url":null,"abstract":"<p><p>The advent of digital twins has increased the demand for longer-duration simulations that span multiple physiological states. Digital twins have emerged as powerful tools in cardiovascular modeling, enabling patient-specific simulations of coronary blood flow for non-invasive diagnosis and treatment planning. Although these simulations achieve high fidelity under steady or periodic heart rates, modeling real-world transitions, such as those arising from physical activity, requires careful evaluation of temporal convergence, the stabilization of hemodynamic parameters through the simulation of preceding cardiac cycles, or 'pre-flows'. In this study, we present a physiologically grounded approach for determining the minimum number of preceding cardiac pre-flows necessary to achieve temporal convergence following abrupt heart rate (HR) changes. Using high-resolution patient-specific 3-dimensional (3D) simulations and inflow waveforms scaled from both synthetic and wearable-derived HR data, we quantify convergence behavior across velocity, pressure gradient, and wall shear stress at both cross-sectional and full-domain levels. Results show that simulating just two pre-flows is sufficient to achieve physiologically stable outputs across high-to-low and low-to-high HR transitions (<2% difference). These findings are further verified using continuous HR data obtained from wearable devices, with low and high HR segments extracted to represent natural extremes, confirming the robustness of the proposed convergence criterion under real-world dynamic inputs (<1% difference). This work establishes a computationally efficient and physiologically consistent criterion for dynamic-state simulations, facilitating the integration of cardiovascular digital twins with real-time sensing technologies.</p>","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 9","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13425941/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148654135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rheological and sealing properties study of carbon nanotube-modified high viscosity magnetic fluids","authors":"Chuding Zhang, Decai Li, Shilin Nie, Wenxi Zhao, Jixian Yang, Licong Jin","doi":"10.1063/5.0276832","DOIUrl":"https://doi.org/10.1063/5.0276832","url":null,"abstract":"The preparation of magnetic fluids (MFs) with high viscosity, high saturation magnetization, and high stability has long been a critical challenge hindering the progress of related applications. In this study, we successfully prepared carbon nanotube-modified Poly-Alpha-Olefine20-based magnetic fluids (CNT-MF). The rotational rheometer was employed for rheological characterization under different conditions. Through a self-built magnetic fluids sealing test rig, the impact of their rheological properties in practical working environments was verified. The results revealed that the CNT-MF achieved a saturation magnetization of up to 36.2 KA/m, an apparent viscosity exceeding 2336 mPa s (at 0 T, 1000 1/s shear rate, and 25 °C). When applied to magnetic fluid sealing, CNT-MF showed more excellent sealing performance, especially in low-speed sealing and small seal clearance conditions. In the static sealing with a 0.6 mm sealing gap, the sealing capacity value of CNT-MF exceeds that of PAO3.5-MF by more than 19.28%, which effectively demonstrates the significant improvement effect of the rheological properties of MF on sealing performance.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147902306","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":"Spatiotemporal distribution of the intraglottal pressure and vocal fold contact pressure in excised larynges.","authors":"Sarah Lehoux, Zhaoyan Zhang","doi":"10.1063/5.0283313","DOIUrl":"10.1063/5.0283313","url":null,"abstract":"<p><p>The contact pressure experienced by the vocal folds during phonation is considered a major factor contributing to vocal fold injuries and lesions. Understanding the spatiotemporal distribution of vocal fold contact pressure across the medial surface and its dependence on laryngeal geometrical and mechanical properties (such as glottal gap, vocal fold vertical thickness, vocal fold length, and vocal fold stiffness) is essential to identifying strategies that minimize contact pressure and reduce the risk of vocal injury. This study aims to characterize the spatiotemporal distribution of intraglottal pressure across the medial surface in excised larynges. The intraglottal pressure was measured using a modified probe microphone at different locations within the vertical plane containing the glottal centerline (mid-sagittal plane), following a grid-like pattern. The resulting pressure distribution maps indicate small variations of intraglottal pressure in the anterior-posterior dimension, but large, complex variations in the vertical dimension. A criterion, derived from applying Bernoulli's equation to vocal fold vibration with prescribed vocal fold contact, was developed to identify the contact pressure peak as a rapid increase in the intraglottal pressure preceded by a negative pressure in the intraglottal pressure waveform. This criterion also allows estimation of the vertical span of vocal fold contact (by extension the vocal fold vertical thickness) and the mucosal wave speed. The preliminary results from this study indicate that the vocal fold vertical thickness has a large impact on the peak contact pressure value, which corroborates findings from previous computational studies.</p>","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 9","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12704246/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145768868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrodynamic cavitation of nematic liquid crystal behind a bluff body in microchannels with different aspect ratios","authors":"Jiajia Yu, Lu-Yang Jiang, Jie Peng, Hao-Ran Guo, Ling-Hao Diao, Maitiniyazi Bake, Chun‐Mei Wu, You‐Rong Li","doi":"10.1063/5.0279719","DOIUrl":"https://doi.org/10.1063/5.0279719","url":null,"abstract":"The hydrodynamic cavitation phenomenon in microfluidic chips is widely utilized in biochemistry due to the lower critical Reynolds number for cavitation inception, which differs significantly from that observed on a macroscopic scale. However, most existing research is directed to isotropic fluids, while hydrodynamic cavitation of anisotropic fluids in microchannels is poorly studied. In this paper, the hydrodynamic cavitation of nematic liquid crystal flowing past a cylindrical bluff body in microchannels with different aspect ratios is experimentally investigated. When the Reynolds number Re &amp;lt; 1.5 × 10−3, a special flow phenomenon named disclination loop caused by the discontinuous variation of liquid crystal director can be observed. The geometry of the disclination loop and its evolution with flow conditions are examined. Hydrodynamic cavitation occurs in the Stokes flow regime (Re ≪ 1), and the critical Reynolds number of cavitation inception increases with the aspect ratio of the microchannel. In addition, the oscillation characteristics of the cavitation domain are found closely correlate with the aspect ratio and the Reynolds number. The Strouhal number of the cavitation domain increases with the aspect ratio and decreases with the Reynolds number. The pressure difference between the inlet and outlet of the microchannel shows a linear relation with the Reynolds number rather than the exponential relation for isotropic fluids.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147912447","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":"Influence of hull–propeller–rudder interaction on the self-propulsion of wind-assisted ships","authors":"Saeed Hosseinzadeh, Dominic A. Hudson, Stephen R. Turnock, Martyn Prince, J. Banks","doi":"10.1063/5.0281083","DOIUrl":"https://doi.org/10.1063/5.0281083","url":null,"abstract":"Wind-assisted propulsion systems represent one of the most promising technologies for decreasing greenhouse gas emissions in shipping, offering significant potential to reduce fuel consumption. There is a complex interaction between the forces and moments generated by the wind assist device and the hydrodynamic performance of the ship's hull, propeller, and rudder. An experimental investigation was conducted in the 138 m Boldrewood towing tank using a 1/61 scale geosim of a single-screw containership hull. Hull, propeller, and rudder forces were measured through resistance, non-propelled, and self-propelled captive tests at a full-scale representative service speed of 18 knots. Tests covered typical wind assist conditions using four offloaded propeller conditions, simulating partial thrust from wind of 10%, 20%, 30%, and 40%, with leeway (drift) angles ranging from ±5° and rudder angles from –30° to +30° with 10° increments. The study provides physical insight into the relative interactions as well as a benchmark dataset for the effects of leeway and rudder angles on hydrodynamic forces and moments across different propeller loadings available for use in velocity prediction programs and for design. The results indicate that as the physical rudder angle increases, there is a corresponding increase in ship resistance, side force, and rudder-induced yaw moment that is dependent on propeller thrust loading and its flow straightening effect on the effective rudder angle. Analysis of drift-induced resistance provided valuable insights into efficiency tradeoffs in wind-powered ships implementation, including the net resistance penalty of hull leeway and rudder drag on required overall thrust. The relative contribution of rudder side force and yaw moment to the total side force and yaw moment is analyzed. For each tested leeway angle, the study identifies the required rudder angle to balance hydrodynamic-induced yaw moment, demonstrating the significant rudder adjustments necessary for wind-propelled ships and thereby the hull features that would be beneficial for future wind assist ship design.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147891532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Research on microscopic displacement mechanism of slickwater in different pore sizes","authors":"Ziyu Lin, Yuetian Liu, Yulong Huang, Yuting He, Pingtian Fan, Liang Xue","doi":"10.1063/5.0279807","DOIUrl":"https://doi.org/10.1063/5.0279807","url":null,"abstract":"To address the challenges like low recovery efficiency and rapid production decline following conventional hydraulic fracturing in tight reservoirs, fracturing oil-displacement integration has garnered significant attention. However, the microscopic effects of slickwater invasion during these operations remain insufficiently understood. Previous studies have typically focused on either its oil displacement ability or its effect on pore structure, rarely investigating the direct link between them. This study compares the microscopic displacement mechanisms of slickwater and formation water using interfacial tension measurements, contact angle measurements, core flooding experiments, nuclear magnetic resonance (NMR) analysis, and scanning electron microscopy analysis on identical artificial sandstone cores. While slickwater exhibits better interfacial properties, the results show that its primary enhanced oil recovery mechanism is a three-stage oil displacement pattern by pore volume (PV), which increases ultimate recovery by approximately 5%. NMR T2 spectra reveal that in the early stage (&amp;lt;2 PV), slickwater's higher viscous forces rapidly activate macropores. In the middle stage (2–5 PV), polymer-induced blockage of primary channels forces a flow diversion into previously bypassed mesopores. Finally, in the late stage (&amp;gt;5 PV), there is limited additional recovery. However, the polymer retention causes severe core damage, leading to a 70.2% reduction in permeability. NMR analysis proves slickwater preferentially invades mesopores and macropores, and post-flooding SEM images directly visualize polymer aggregates plugging these pathways, confirming the pore structure variations. This work quantifies the dual role of slickwater in enhancing recovery through flow diversion while altering pore structure, providing critical insights for optimizing fracturing oil-displacement integration.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"37 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147886910","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}