Pub Date : 2026-01-01Epub Date: 2025-09-12DOI: 10.1016/j.euromechflu.2025.204367
Janhavi K. Devnikar, Jayraj M. Chapare, Om M. Butle, P.W. Deshmukh, Pravin R. Kubade, Lalit K. Toke
Augmentation of heat transfer plays a crucial role in energy-saving options in modern thermal systems. These enhancement methods are passive with no external power source, and another is an active method where an external energy source is essential. The passive methods are more popular and the best energy-saving option, making the system more effective and efficient. The recent advancement in passive methods is a compound method consisting of alterations in the fluid containers and obstructions in fluid passages. In the prevailing study, the round tube is formed in the profile of a twisted tube, within which a twisted strip is placed. The twisted tube causes a reduction in the temperature and velocity gradients near the tube surface due to the twisting motion of the fluid at that region, whereas the central core portion of the fluid interacts thoroughly with the heated surface due to the presence of the twisted strip at the central portion of the twisted tube. This modified flow system enhanced heat transfer using air as a fluid in turbulent flow circumstances for Reynolds numbers ranging from 2500 to 17000. The present study indicates that the average improvement ratio, Nue/Nup, and average friction factor ratio, fe/fp, are 1.25–3.9 and 2.0–12.0, respectively, compared with the plain tube at the same flow rate conditions.
{"title":"Thermohydraulic performance of twisted circular tube (TCT) retrofitted with twisted strip (TS) insert","authors":"Janhavi K. Devnikar, Jayraj M. Chapare, Om M. Butle, P.W. Deshmukh, Pravin R. Kubade, Lalit K. Toke","doi":"10.1016/j.euromechflu.2025.204367","DOIUrl":"10.1016/j.euromechflu.2025.204367","url":null,"abstract":"<div><div>Augmentation of heat transfer plays a crucial role in energy-saving options in modern thermal systems. These enhancement methods are passive with no external power source, and another is an active method where an external energy source is essential. The passive methods are more popular and the best energy-saving option, making the system more effective and efficient. The recent advancement in passive methods is a compound method consisting of alterations in the fluid containers and obstructions in fluid passages. In the prevailing study, the round tube is formed in the profile of a twisted tube, within which a twisted strip is placed. The twisted tube causes a reduction in the temperature and velocity gradients near the tube surface due to the twisting motion of the fluid at that region, whereas the central core portion of the fluid interacts thoroughly with the heated surface due to the presence of the twisted strip at the central portion of the twisted tube. This modified flow system enhanced heat transfer using air as a fluid in turbulent flow circumstances for Reynolds numbers ranging from 2500 to 17000. The present study indicates that the average improvement ratio, <em>Nu</em><sub><em>e</em></sub><em>/Nu</em><sub><em>p</em></sub><em>,</em> and average friction factor ratio, <em>f</em><sub><em>e</em></sub><em>/f</em><sub><em>p</em></sub>, are 1.25–3.9 and 2.0–12.0, respectively, compared with the plain tube at the same flow rate conditions.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204367"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Flight feathers of birds are featured by the typical herringbone pattern, which is consisted of a central shaft and divergent barbs on both sides. In this work, bio-inspired herringbone riblets are embedded into the suction side of a NACA0012 airfoil model, with an attempt to explore their roles on the flow and fluid force. Experiments are conducted in a water tunnel at a Reynolds number of Re = 2 × 105, based on incoming freestream velocity and airfoil cord length c. While the lift and drag forces of the airfoil model are measured by a load cell, flow fields over the suction side of the airfoil model are captured by the particle image velocimetry (PIV) technique. The herringbone-ribbed suction side of the airfoil model is defined by the divergent angle β (= 60°) of the riblets, the spanwise wavelength λ (= 0.2c and 0.4c) of the repeating herringbone pattern, as well as the riblet height h (= 0.6 %c and 1.2 %c). Results from the force measurements reveal that the airfoil models with the herringbone-ribbed suction side outperform their smooth counterparts and the baseline NACA0012 model, with the stall being significantly postponed from 10° to over 16° while the maximum time-mean lift coefficient being remained nearly unaffected. This is attributed to the transition from laminar to turbulent boundary layers, thus associated with substantially suppressed flow separation, over the airfoil models with the bio-inspired riblets being covered on the suction side. On the other hand, it is observed that the time-mean lift coefficient is considerably reduced whilst the drag coefficient is marginally increased at the angle of attack α < 12° for the airfoil models with the bio-inspired riblets being covered on the suction side, compared with those of their smooth counterparts and the baseline NACA0012 model.
{"title":"Flow over airfoil model covered by bio-inspired herringbone riblets","authors":"Haoxiang He, Honglei Bai, Shixiong Zhang, Zan Zhang","doi":"10.1016/j.euromechflu.2025.204365","DOIUrl":"10.1016/j.euromechflu.2025.204365","url":null,"abstract":"<div><div>Flight feathers of birds are featured by the typical herringbone pattern, which is consisted of a central shaft and divergent barbs on both sides. In this work, bio-inspired herringbone riblets are embedded into the suction side of a NACA0012 airfoil model, with an attempt to explore their roles on the flow and fluid force. Experiments are conducted in a water tunnel at a Reynolds number of <em>Re</em> = 2 × 10<sup>5</sup>, based on incoming freestream velocity and airfoil cord length <em>c</em>. While the lift and drag forces of the airfoil model are measured by a load cell, flow fields over the suction side of the airfoil model are captured by the particle image velocimetry (PIV) technique. The herringbone-ribbed suction side of the airfoil model is defined by the divergent angle <em>β</em> (= 60°) of the riblets, the spanwise wavelength <em>λ</em> (= 0.2<em>c</em> and 0.4<em>c</em>) of the repeating herringbone pattern, as well as the riblet height <em>h</em> (= 0.6 %<em>c</em> and 1.2 %<em>c</em>). Results from the force measurements reveal that the airfoil models with the herringbone-ribbed suction side outperform their smooth counterparts and the baseline NACA0012 model, with the stall being significantly postponed from 10° to over 16° while the maximum time-mean lift coefficient being remained nearly unaffected. This is attributed to the transition from laminar to turbulent boundary layers, thus associated with substantially suppressed flow separation, over the airfoil models with the bio-inspired riblets being covered on the suction side. On the other hand, it is observed that the time-mean lift coefficient is considerably reduced whilst the drag coefficient is marginally increased at the angle of attack <em>α</em> < 12° for the airfoil models with the bio-inspired riblets being covered on the suction side, compared with those of their smooth counterparts and the baseline NACA0012 model.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204365"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-09-08DOI: 10.1016/j.euromechflu.2025.204355
Simon Dalpke , Jiasheng Yang , Pourya Forooghi , Bettina Frohnapfel , Alexander Stroh
The influence of rough surfaces on fluid flow is characterized by the downward shift in the logarithmic layer of velocity and temperature profiles, namely the velocity roughness function and the corresponding temperature roughness function . Their computation relies on computational simulations, and hence a simple prediction without such simulation is envisioned. We present a framework where a data-driven model is developed using the dataset of Yang et al. 2023 [1] with 93 high-fidelity direct numerical simulations of a fully-developed turbulent channel flow at and . The model provides robust predictive capabilities (mean squared error and ), but lacks interpretability. Simplistic statistical roughness parameters provide a more understandable route, so the framework is extended with a symbolic regression approach to distill an empirical correlation from the data-driven model. The derived expression leads to a predictive correlation for the equivalent sand-grain roughness with reasonable predictive powers. The predictive capability of the temperature roughness function is subject to limitations due to the missing Prandtl number variation in the dataset. Nevertheless, the interpretable correlation and the neural network as well as the original dataset can be used to explore the roughness functions. The functional form of the derived correlations, along with visual analysis of these surfaces, suggests a strong relationship with roughness wavelengths, further linking them to explanations based on sheltered and windward regions.
{"title":"Data-driven correlations for thermohydraulic roughness properties","authors":"Simon Dalpke , Jiasheng Yang , Pourya Forooghi , Bettina Frohnapfel , Alexander Stroh","doi":"10.1016/j.euromechflu.2025.204355","DOIUrl":"10.1016/j.euromechflu.2025.204355","url":null,"abstract":"<div><div>The influence of rough surfaces on fluid flow is characterized by the downward shift in the logarithmic layer of velocity and temperature profiles, namely the velocity roughness function <span><math><mrow><mi>Δ</mi><msup><mrow><mi>U</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow></math></span> and the corresponding temperature roughness function <span><math><mrow><mi>Δ</mi><msup><mrow><mi>Θ</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow></math></span>. Their computation relies on computational simulations, and hence a simple prediction without such simulation is envisioned. We present a framework where a data-driven model is developed using the dataset of Yang et al. 2023 <span><span>[1]</span></span> with 93 high-fidelity direct numerical simulations of a fully-developed turbulent channel flow at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>≈</mo><mn>800</mn></mrow></math></span> and <span><math><mrow><mi>P</mi><mi>r</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>71</mn></mrow></math></span>. The model provides robust predictive capabilities (mean squared error <span><math><mrow><msub><mrow><mtext>MSE</mtext></mrow><mrow><mi>k</mi></mrow></msub><mo>=</mo><mn>0</mn><mo>.</mo><mn>09</mn></mrow></math></span> and <span><math><mrow><msub><mrow><mtext>MSE</mtext></mrow><mrow><mi>θ</mi></mrow></msub><mo>=</mo><mn>0</mn><mo>.</mo><mn>096</mn></mrow></math></span>), but lacks interpretability. Simplistic statistical roughness parameters provide a more understandable route, so the framework is extended with a symbolic regression approach to distill an empirical correlation from the data-driven model. The derived expression leads to a predictive correlation for the equivalent sand-grain roughness <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mtext>s</mtext></mrow></msub><mo>=</mo><msub><mrow><mi>k</mi></mrow><mrow><mtext>99</mtext></mrow></msub><mrow><mo>(</mo><mi>E</mi><msub><mrow><mi>S</mi></mrow><mrow><mi>x</mi></mrow></msub><mrow><mo>(</mo><mo>−</mo><mi>E</mi><msub><mrow><mi>S</mi></mrow><mrow><mi>x</mi></mrow></msub><mo>+</mo><mi>S</mi><mi>k</mi><mo>+</mo><mn>2</mn><mo>.</mo><mn>37</mn><mo>)</mo></mrow><mo>+</mo><mn>0</mn><mo>.</mo><mn>772</mn><mo>)</mo></mrow></mrow></math></span> with reasonable predictive powers. The predictive capability of the temperature roughness function is subject to limitations due to the missing Prandtl number variation in the dataset. Nevertheless, the interpretable correlation and the neural network as well as the original dataset can be used to explore the roughness functions. The functional form of the derived correlations, along with visual analysis of these surfaces, suggests a strong relationship with roughness wavelengths, further linking them to explanations based on sheltered and windward regions.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204355"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The enhancement of energy efficiency in reciprocating compressor valves has long been constrained by the non-analytical nature of multi-parameter coupling effects. Traditional single-parameter strategies are inadequate for revealing the complex nonlinear interactions within flow paths. To address this limitation, this study proposes a response surface method (RSM)-based strategy for the topological optimization of stereoscopic flow channels. By constructing spatial interactions among contact surface tilt angles, flow path angles, and port-slot ratios, the study for the first time quantifies the influence of multi-parameter coupling mechanisms on effective flow area and flow coefficient. The optimal parameter combination obtained via RSM (α=71.8°, β=14.2°, γ=2:1) exhibited superior performance, as confirmed by both experimental and industrial tests: compared with the passive plate valve, the discharge volume increased by 50.1 % and the specific energy consumption per unit discharge volume decreased by 7.6 %; relative to the single-parameter numerical optimization group, the discharge volume further increased by 3.3 % and the specific energy consumption decreased by 2.7 %. The discrepancy between simulation and experimental results was less than 5 %, validating the reliability and accuracy of the proposed method. This study establishes an integrated methodological framework of “parameter coupling analysis-flow field characteristic regulation—system energy efficiency verification,” providing a novel paradigm for the intelligent design and energy-efficient optimization of high-performance fluid machinery.
{"title":"Stereoscopic valve flow path topology design in reciprocating compressors: Structural optimization via the response surface method","authors":"Xiao Hong, Weilin Cui, Dexi Wang, Dajing Liu, Xinrui Fu, Xiwen Cao","doi":"10.1016/j.euromechflu.2025.204378","DOIUrl":"10.1016/j.euromechflu.2025.204378","url":null,"abstract":"<div><div>The enhancement of energy efficiency in reciprocating compressor valves has long been constrained by the non-analytical nature of multi-parameter coupling effects. Traditional single-parameter strategies are inadequate for revealing the complex nonlinear interactions within flow paths. To address this limitation, this study proposes a response surface method (RSM)-based strategy for the topological optimization of stereoscopic flow channels. By constructing spatial interactions among contact surface tilt angles, flow path angles, and port-slot ratios, the study for the first time quantifies the influence of multi-parameter coupling mechanisms on effective flow area and flow coefficient. The optimal parameter combination obtained via RSM (<em>α</em>=71.8°, <em>β</em>=14.2°, <em>γ</em>=2:1) exhibited superior performance, as confirmed by both experimental and industrial tests: compared with the passive plate valve, the discharge volume increased by 50.1 % and the specific energy consumption per unit discharge volume decreased by 7.6 %; relative to the single-parameter numerical optimization group, the discharge volume further increased by 3.3 % and the specific energy consumption decreased by 2.7 %. The discrepancy between simulation and experimental results was less than 5 %, validating the reliability and accuracy of the proposed method. This study establishes an integrated methodological framework of “parameter coupling analysis-flow field characteristic regulation—system energy efficiency verification,” providing a novel paradigm for the intelligent design and energy-efficient optimization of high-performance fluid machinery.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204378"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-04DOI: 10.1016/j.euromechflu.2025.204379
Ashok Kumar , Anup Singh Negi , Ashok Kumar
This study investigates the linear stability of buoyancy-assisted Poiseuille flow of an electrically conducting fluid through a vertical porous pipe subjected to a transverse magnetic field. The flow behavior is modeled using the Brinkman-extended non-Darcy formulation to capture the influence of both viscous and inertial effects in a porous medium. A linear stability analysis is performed, and the consequential eigenvalue problem is solved numerically using the Chebyshev spectral collocation method. The impact of key dimensionless parameters, including the Prandtl number ( to 100), Darcy number ( to ), and Hartmann number (), are systematically examined to understand their roles in flow stability. The results reveal that the base velocity profile exhibits an inflection point, and the applied magnetic field significantly alters both velocity and temperature distributions. For water (), the flow exhibits least stability at higher magnetic influence (), indicating the potential for enhanced heat transfer, particle dispersion, and flow manipulation. Conversely, for heavy oil (), the flow is least stable without a magnetic field (), highlighting magnetic field-based control strategies for applications such as thermal management, flow control, and smart fluidic devices. These findings offer important insights for optimizing magnetohydrodynamic flows in porous systems for engineering and industrial applications.
{"title":"A linear stability investigation of non-Darcian MHD flow in a vertical pipe via numerical methods","authors":"Ashok Kumar , Anup Singh Negi , Ashok Kumar","doi":"10.1016/j.euromechflu.2025.204379","DOIUrl":"10.1016/j.euromechflu.2025.204379","url":null,"abstract":"<div><div>This study investigates the linear stability of buoyancy-assisted Poiseuille flow of an electrically conducting fluid through a vertical porous pipe subjected to a transverse magnetic field. The flow behavior is modeled using the Brinkman-extended non-Darcy formulation to capture the influence of both viscous and inertial effects in a porous medium. A linear stability analysis is performed, and the consequential eigenvalue problem is solved numerically using the Chebyshev spectral collocation method. The impact of key dimensionless parameters, including the Prandtl number (<span><math><mrow><mi>P</mi><mi>r</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>01</mn></mrow></math></span> to 100), Darcy number (<span><math><mrow><mi>D</mi><mi>a</mi><mo>=</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> to <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup></mrow></math></span>), and Hartmann number (<span><math><mrow><mi>H</mi><mi>a</mi></mrow></math></span>), are systematically examined to understand their roles in flow stability. The results reveal that the base velocity profile exhibits an inflection point, and the applied magnetic field significantly alters both velocity and temperature distributions. For water (<span><math><mrow><mi>P</mi><mi>r</mi><mo>=</mo><mn>7</mn></mrow></math></span>), the flow exhibits least stability at higher magnetic influence (<span><math><mrow><mi>H</mi><mi>a</mi><mo>=</mo><mn>2</mn></mrow></math></span>), indicating the potential for enhanced heat transfer, particle dispersion, and flow manipulation. Conversely, for heavy oil (<span><math><mrow><mi>P</mi><mi>r</mi><mo>=</mo><mn>50</mn></mrow></math></span>), the flow is least stable without a magnetic field (<span><math><mrow><mi>H</mi><mi>a</mi><mo>=</mo><mn>0</mn></mrow></math></span>), highlighting magnetic field-based control strategies for applications such as thermal management, flow control, and smart fluidic devices. These findings offer important insights for optimizing magnetohydrodynamic flows in porous systems for engineering and industrial applications.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204379"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present study explores onset of Rayleigh–Taylor instability (RTI) and Kelvin–Helmholtz Rayleigh–Taylor instability (KHRTI) with highly-resolved direct numerical simulations of two setups considering air at different temperatures (or densities) and/or velocities in two halves of three-dimensional (3D) cuboidal domains. The RTI and KHRTI are simulated with 4.2 billion and 480 million mesh points, respectively. Here, we do not impose any external perturbation similar to the unforced experiments of RTI and KHRTI. The compressible Navier–Stokes equations are solved using a novel parallel algorithm which does not involve overlapping points at sub-domain boundaries. This removes the errors at sub-domain boundaries and provides same level of accuracy as sequential computing. The pressure disturbance field is compared during onset of RTI and KHRTI and corresponding convection- and advection-dominated mechanisms are highlighted by instantaneous features, spectra, and proper orthogonal decomposition. Relative contributions of pressure energy, kinetic energy and rotational energy to overall energy budget are explored, revealing acoustics to play a central role in initial perturbation for both RTI and KHRTI. The nonlinear, spatio-temporal nature of the instability is further explored by application of a transport equation for enstrophy of compressible flows. This provides insights into the similarities and differences between onset mechanisms of RTI and KHRTI, serving as a benchmark data set for shear and buoyancy-driven instabilities across diverse applications in geophysics, nuclear energy and atmospheric fluid dynamics.
{"title":"Comparing the highly-resolved onset of Rayleigh–Taylor and Kelvin–Helmholtz Rayleigh–Taylor instabilities","authors":"Bhavna Joshi , Aditi Sengupta , Yassin Ajanif , Lucas Lestandi","doi":"10.1016/j.euromechflu.2025.204382","DOIUrl":"10.1016/j.euromechflu.2025.204382","url":null,"abstract":"<div><div>The present study explores onset of Rayleigh–Taylor instability (RTI) and Kelvin–Helmholtz Rayleigh–Taylor instability (KHRTI) with highly-resolved direct numerical simulations of two setups considering air at different temperatures (or densities) and/or velocities in two halves of three-dimensional (3D) cuboidal domains. The RTI and KHRTI are simulated with 4.2 billion and 480 million mesh points, respectively. Here, we do not impose any external perturbation similar to the unforced experiments of RTI and KHRTI. The compressible Navier–Stokes equations are solved using a novel parallel algorithm which does not involve overlapping points at sub-domain boundaries. This removes the errors at sub-domain boundaries and provides same level of accuracy as sequential computing. The pressure disturbance field is compared during onset of RTI and KHRTI and corresponding convection- and advection-dominated mechanisms are highlighted by instantaneous features, spectra, and proper orthogonal decomposition. Relative contributions of pressure energy, kinetic energy and rotational energy to overall energy budget are explored, revealing acoustics to play a central role in initial perturbation for both RTI and KHRTI. The nonlinear, spatio-temporal nature of the instability is further explored by application of a transport equation for enstrophy of compressible flows. This provides insights into the similarities and differences between onset mechanisms of RTI and KHRTI, serving as a benchmark data set for shear and buoyancy-driven instabilities across diverse applications in geophysics, nuclear energy and atmospheric fluid dynamics.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204382"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-08DOI: 10.1016/j.euromechflu.2025.204385
Josías N. Molina-Courtois , Roxana Belen Pérez Hidalgo , Yojana J.P. Carreón , Carlos A. Martínez-Miwa , Lourdes Díaz-Jiménez , Mario Castelán , Jorge González-Gutiérrez
The method of pattern analysis in dried droplets has emerged as an effective tool for detecting adulterants in medications and diagnosing pathologies. However, despite numerous studies on the drying dynamics of droplets, there remains a need for effective methods to stabilize droplet contact line and achieve controlled coating. Finding alternative solutions for droplet stabilization could significantly improve the precision and efficacy in the application of the dry droplet pattern recognition method. In this study, we hypothesize that bovine serum albumin (BSA) can act as an effective tool for stabilizing the contact line of sessile methotrexate (MTX) drops, controlling pattern formation during the drying process. We evaluated BSA concentrations of 0.01, 0.1, 0.25, 0.5, 1, and 2% in MTX (10%) solutions; which, in the absence of BSA, become destabilized on polymethylmethacrylate (PMMA) substrates. Our results indicate that, starting from a concentration of 0.1% BSA, the methotrexate droplets are efficiently fixed, producing highly reproducible patterns. Using measurements of height profile, contact angle, and evaporation time, we found that BSA fixes the droplets and prevents the deformation of the contact line. Additionally, we observed that BSA modifies the interaction between the droplet and the substrate, improving adhesion and reducing the expansion or contraction of the droplets. Importantly, the stabilizing effect was only observed when BSA was present in solution; when BSA was pre-adsorbed onto the substrate, MTX droplets exhibited spreading and destabilization. We demonstrated that BSA promotes a homogeneous distribution of solutes and more uniform and controlled evaporation when acting as a solution-phase additive in MTX formulations. These findings indicate that BSA can serve as a functional modulator for enhancing reproducibility and controlling deposition in dropwise manufacturing of pharmaceutical coatings.
{"title":"Stabilization of drug droplet contact line via Bovine Serum Albumin Solution-Phase Additive","authors":"Josías N. Molina-Courtois , Roxana Belen Pérez Hidalgo , Yojana J.P. Carreón , Carlos A. Martínez-Miwa , Lourdes Díaz-Jiménez , Mario Castelán , Jorge González-Gutiérrez","doi":"10.1016/j.euromechflu.2025.204385","DOIUrl":"10.1016/j.euromechflu.2025.204385","url":null,"abstract":"<div><div>The method of pattern analysis in dried droplets has emerged as an effective tool for detecting adulterants in medications and diagnosing pathologies. However, despite numerous studies on the drying dynamics of droplets, there remains a need for effective methods to stabilize droplet contact line and achieve controlled coating. Finding alternative solutions for droplet stabilization could significantly improve the precision and efficacy in the application of the dry droplet pattern recognition method. In this study, we hypothesize that bovine serum albumin (BSA) can act as an effective tool for stabilizing the contact line of sessile methotrexate (MTX) drops, controlling pattern formation during the drying process. We evaluated BSA concentrations of 0.01, 0.1, 0.25, 0.5, 1, and 2% in MTX (10%) solutions; which, in the absence of BSA, become destabilized on polymethylmethacrylate (PMMA) substrates. Our results indicate that, starting from a concentration of 0.1% BSA, the methotrexate droplets are efficiently fixed, producing highly reproducible patterns. Using measurements of height profile, contact angle, and evaporation time, we found that BSA fixes the droplets and prevents the deformation of the contact line. Additionally, we observed that BSA modifies the interaction between the droplet and the substrate, improving adhesion and reducing the expansion or contraction of the droplets. Importantly, the stabilizing effect was only observed when BSA was present in solution; when BSA was pre-adsorbed onto the substrate, MTX droplets exhibited spreading and destabilization. We demonstrated that BSA promotes a homogeneous distribution of solutes and more uniform and controlled evaporation when acting as a solution-phase additive in MTX formulations. These findings indicate that BSA can serve as a functional modulator for enhancing reproducibility and controlling deposition in dropwise manufacturing of pharmaceutical coatings.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204385"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-09-25DOI: 10.1016/j.euromechflu.2025.204375
Congren Zheng , Yong Chen , Zijing Ding
A linear stability analysis is performed on rotating pipe flow with a non-ideal fluid. The study focuses on supercritical CO near its vapor–liquid critical point, where thermodynamic properties deviate significantly from ideal gas. Different wall temperatures are considered, ensuring centerline temperatures span subcritical, transcritical, and supercritical conditions. The modal analysis reveals that at low rotation speeds, unstable mode only exists at rotational speed . Also multiple unstable modes emerge, introducing a more complex instability mechanism compared to non-rotating pipe flow. As rotation speed increases, viscous dissipation plays a key role in flow stabilization, while thermodynamic effects remain secondary. The non-modal analysis further demonstrates that optimal system response under fixed-frequency forcing shifts due to rotation, with stronger deviations from incompressible behavior at high compressibility. In rotating pipe flow, the dependence of transient energy growth on the azimuthal wavenumber () is inherently nonlinear, which stands in stark contrast to the approximately linear relationship typically observed in non-rotating pipe flow. This nonlinearity arises primarily due to the influence of azimuthal velocity components introduced by rotation. These findings highlight the intricate coupling between rotation, compressibility, and thermodynamics, providing new insights into instability mechanisms in non-ideal fluid systems.
{"title":"Linear stability of rotating pipe flow with non-ideal fluid","authors":"Congren Zheng , Yong Chen , Zijing Ding","doi":"10.1016/j.euromechflu.2025.204375","DOIUrl":"10.1016/j.euromechflu.2025.204375","url":null,"abstract":"<div><div>A linear stability analysis is performed on rotating pipe flow with a non-ideal fluid. The study focuses on supercritical CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> near its vapor–liquid critical point, where thermodynamic properties deviate significantly from ideal gas. Different wall temperatures are considered, ensuring centerline temperatures span subcritical, transcritical, and supercritical conditions. The modal analysis reveals that at low rotation speeds, unstable mode only exists at rotational speed <span><math><mrow><mi>Ω</mi><mo><</mo><mn>0</mn></mrow></math></span>. Also multiple unstable modes emerge, introducing a more complex instability mechanism compared to non-rotating pipe flow. As rotation speed increases, viscous dissipation plays a key role in flow stabilization, while thermodynamic effects remain secondary. The non-modal analysis further demonstrates that optimal system response under fixed-frequency forcing shifts due to rotation, with stronger deviations from incompressible behavior at high compressibility. In rotating pipe flow, the dependence of transient energy growth on the azimuthal wavenumber (<span><math><mi>n</mi></math></span>) is inherently nonlinear, which stands in stark contrast to the approximately linear relationship typically observed in non-rotating pipe flow. This nonlinearity arises primarily due to the influence of azimuthal velocity components introduced by rotation. These findings highlight the intricate coupling between rotation, compressibility, and thermodynamics, providing new insights into instability mechanisms in non-ideal fluid systems.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204375"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145155616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-09-08DOI: 10.1016/j.euromechflu.2025.204356
Sarita Yadav, Geetanjali Chattopadhyay
The electrohydrodynamic stability of a two-layer plane Poiseuille flow has been considered under the influence of an electric field acting normally to the interface of the two viscous immiscible fluids. The two fluids considered here for the asymptotic stability analysis are leaky dielectrics. The study on the influence of a monolayer of insoluble surfactant at the fluid-fluid interface reveals that the interfacial surfactant further enhances or suppresses the electric field-induced instability. The long-wave linear stability analysis is carried out in the framework of Orr–Sommerfeld analysis for leaky dielectrics. In the context of long-wave linear stability study, the phase speed is expressed as a function of the ratio of viscosities (), layer thicknesses (), densities (), permittivities () and conductivities () of the two fluids. The electric field is observed to have either a destabilizing or a stabilizing effect, primarily non-monotonic, depending upon the ratios of permittivities and conductivities of the two fluids. It is found that when , the region of instability in the plane increases with increasing Marangoni number (); however, when , the scenario reverses. The electrohydrodynamic interface instability among two viscous fluids with varying electrical properties in plane Poiseuille flow has applications in microfluidic devices for mixing and droplet formation. Therefore, the present study aims to propose a control mechanism for the instability occurring at the interface through the modified interface tension.
{"title":"Role of insoluble surfactant on electrohydrodynamic stability of a two-layer plane Poiseuille flow: An asymptotic analysis","authors":"Sarita Yadav, Geetanjali Chattopadhyay","doi":"10.1016/j.euromechflu.2025.204356","DOIUrl":"10.1016/j.euromechflu.2025.204356","url":null,"abstract":"<div><div>The electrohydrodynamic stability of a two-layer plane Poiseuille flow has been considered under the influence of an electric field acting normally to the interface of the two viscous immiscible fluids. The two fluids considered here for the asymptotic stability analysis are leaky dielectrics. The study on the influence of a monolayer of insoluble surfactant at the fluid-fluid interface reveals that the interfacial surfactant further enhances or suppresses the electric field-induced instability. The long-wave linear stability analysis is carried out in the framework of Orr–Sommerfeld analysis for leaky dielectrics. In the context of long-wave linear stability study, the phase speed is expressed as a function of the ratio of viscosities (<span><math><mi>m</mi></math></span>), layer thicknesses (<span><math><mi>d</mi></math></span>), densities (<span><math><mi>r</mi></math></span>), permittivities (<span><math><mi>ɛ</mi></math></span>) and conductivities (<span><math><mi>l</mi></math></span>) of the two fluids. The electric field is observed to have either a destabilizing or a stabilizing effect, primarily non-monotonic, depending upon the ratios of permittivities and conductivities of the two fluids. It is found that when <span><math><mrow><mi>m</mi><mo>></mo><msup><mrow><mi>d</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span>, the region of instability in the <span><math><mrow><mi>ɛ</mi><mo>−</mo><mi>l</mi></mrow></math></span> plane increases with increasing Marangoni number (<span><math><mrow><mi>M</mi><mi>a</mi></mrow></math></span>); however, when <span><math><mrow><mi>m</mi><mo><</mo><msup><mrow><mi>d</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span>, the scenario reverses. The electrohydrodynamic interface instability among two viscous fluids with varying electrical properties in plane Poiseuille flow has applications in microfluidic devices for mixing and droplet formation. Therefore, the present study aims to propose a control mechanism for the instability occurring at the interface through the modified interface tension.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204356"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145047215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-14DOI: 10.1016/j.euromechflu.2025.204390
Rajesh Ranjan Dora , Michael H. Meylan , Sanjay Kumar Mohanty
This study investigates wave energy extraction by a floating piezoelectric wave energy converter (PWEC) placed near a wall. The floating PWEC is anchored by mooring lines at its edges to the ocean bottom. This design simulates a potential real-world application of piezoelectric wave energy converters, and the wave-structure interaction is crucial in this arrangement as it influences the superposition of incoming, radiated, and reflected wave components. The coupled hydro-electromechanical equation and dispersion relation for a floating PWEC are derived. The eigenfunction expansion method is then used to investigate the energy extraction by the system. Also, the study examines reflection & dissipation coefficients, the bending moment & shear force of the floating PWEC, and wave force on the wall. Further, the time-dependent modeling of PWEC utilizing a Gaussian pulse is examined, and it is revealed that moored PWEC vibrates for longer times than free PWEC, indicating enhanced energy extraction. Furthermore, it is observed that positioning the PWEC next to a wall, structure, or breakwater can substantially increase energy production. Additionally, the moored PWEC can exhibit efficient damping effects near the wall or structure, making it a multifunctional device.
{"title":"Analysis of a moored floating piezoelectric wave energy converter in the presence of a wall","authors":"Rajesh Ranjan Dora , Michael H. Meylan , Sanjay Kumar Mohanty","doi":"10.1016/j.euromechflu.2025.204390","DOIUrl":"10.1016/j.euromechflu.2025.204390","url":null,"abstract":"<div><div>This study investigates wave energy extraction by a floating piezoelectric wave energy converter (PWEC) placed near a wall. The floating PWEC is anchored by mooring lines at its edges to the ocean bottom. This design simulates a potential real-world application of piezoelectric wave energy converters, and the wave-structure interaction is crucial in this arrangement as it influences the superposition of incoming, radiated, and reflected wave components. The coupled hydro-electromechanical equation and dispersion relation for a floating PWEC are derived. The eigenfunction expansion method is then used to investigate the energy extraction by the system. Also, the study examines reflection & dissipation coefficients, the bending moment & shear force of the floating PWEC, and wave force on the wall. Further, the time-dependent modeling of PWEC utilizing a Gaussian pulse is examined, and it is revealed that moored PWEC vibrates for longer times than free PWEC, indicating enhanced energy extraction. Furthermore, it is observed that positioning the PWEC next to a wall, structure, or breakwater can substantially increase energy production. Additionally, the moored PWEC can exhibit efficient damping effects near the wall or structure, making it a multifunctional device.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204390"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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