Pub Date : 2025-10-14DOI: 10.1016/j.euromechflu.2025.204394
Erik Lindborg
In recent years, several studies have been made in which atmospheric and oceanic data were used to decompose horizontal velocity statistics into a rotational component, associated with vertical vorticity, and a divergent component, associated with horizontal divergence. The decomposition methods rely on the assumption of statistical isotropy. In this paper, the full anisotropic equations relating the rotational, divergent and the rotational-divergent components of the second order velocity structure function tensor to the longitudinal, transverse and longitudinal–transverse components are formulated and solved analytically.
{"title":"A complete Helmholtz decomposition of second order horizontal velocity structure functions","authors":"Erik Lindborg","doi":"10.1016/j.euromechflu.2025.204394","DOIUrl":"10.1016/j.euromechflu.2025.204394","url":null,"abstract":"<div><div>In recent years, several studies have been made in which atmospheric and oceanic data were used to decompose horizontal velocity statistics into a rotational component, associated with vertical vorticity, and a divergent component, associated with horizontal divergence. The decomposition methods rely on the assumption of statistical isotropy. In this paper, the full anisotropic equations relating the rotational, divergent and the rotational-divergent components of the second order velocity structure function tensor to the longitudinal, transverse and longitudinal–transverse components are formulated and solved analytically.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204394"},"PeriodicalIF":2.5,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333164","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 : 2025-10-11DOI: 10.1016/j.euromechflu.2025.204392
Wenhui Zhai , Yuxin Fan , Wei Wang
In advanced afterburner systems, a high inflow temperature can induce thermal autoignition of fuel, resulting in undesirable temperature distributions and causing ablation of flameholders and fuel injection devices. To explore the thermal autoignition characteristics of RP-3 aviation fuel, experiments were conducted using a pressure-swirl atomizer with a forward fuel supply. Key operating parameters included inflow velocity (50–150 m/s), inflow temperature (1000–1200 K), oxygen content (10.5 %–14.1 %), and fuel–air ratio (0.04–0.06). The results indicate that the thermal release and dissipation of autoignition reactions are key factors influencing the autoignition length and mode. Increasing the inflow temperature and fuel–air ratio promotes greater thermal release, while higher flow velocity leads to increased thermal dissipation. When the thermal release is low (e.g., at 1000 K) or thermal dissipation is high (e.g., at 150 m/s and 1100 K), the autoignition mode exhibits randomness, and the flame structure shows a single peak. In cases of low thermal release, an inflow velocity greater than 100 m/s inhibits thermal occurrence. Conversely, with high thermal release (e.g., at 1200 K) or low thermal dissipation (50–100 m/s and 1100 K), the autoignition mode transitions from random to continuous, and the flame structure changes from unimodal to bimodal. Keeping other conditions constant, increasing the inflow temperature from 1000 K to 1200 K reduces the autoignition length by 7.3 %–56.8 %. Similarly, increasing the fuel–air ratio from 0.04 to 0.06 decreases the autoignition length by 12.5 %–49.5 %. On the other hand, raising the inflow velocity from 50 m/s to 150 m/s increases the autoignition length by 32.9 %–252.0 %.
{"title":"Effects of high-velocity flow and oxygen-lean conditions on autoignition of RP-3 aviation fuel","authors":"Wenhui Zhai , Yuxin Fan , Wei Wang","doi":"10.1016/j.euromechflu.2025.204392","DOIUrl":"10.1016/j.euromechflu.2025.204392","url":null,"abstract":"<div><div>In advanced afterburner systems, a high inflow temperature can induce thermal autoignition of fuel, resulting in undesirable temperature distributions and causing ablation of flameholders and fuel injection devices. To explore the thermal autoignition characteristics of RP-3 aviation fuel, experiments were conducted using a pressure-swirl atomizer with a forward fuel supply. Key operating parameters included inflow velocity (50–150 m/s), inflow temperature (1000–1200 K), oxygen content (10.5 %–14.1 %), and fuel–air ratio (0.04–0.06). The results indicate that the thermal release and dissipation of autoignition reactions are key factors influencing the autoignition length and mode. Increasing the inflow temperature and fuel–air ratio promotes greater thermal release, while higher flow velocity leads to increased thermal dissipation. When the thermal release is low (e.g., at 1000 K) or thermal dissipation is high (e.g., at 150 m/s and 1100 K), the autoignition mode exhibits randomness, and the flame structure shows a single peak. In cases of low thermal release, an inflow velocity greater than 100 m/s inhibits thermal occurrence. Conversely, with high thermal release (e.g., at 1200 K) or low thermal dissipation (50–100 m/s and 1100 K), the autoignition mode transitions from random to continuous, and the flame structure changes from unimodal to bimodal. Keeping other conditions constant, increasing the inflow temperature from 1000 K to 1200 K reduces the autoignition length by 7.3 %–56.8 %. Similarly, increasing the fuel–air ratio from 0.04 to 0.06 decreases the autoignition length by 12.5 %–49.5 %. On the other hand, raising the inflow velocity from 50 m/s to 150 m/s increases the autoignition length by 32.9 %–252.0 %.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204392"},"PeriodicalIF":2.5,"publicationDate":"2025-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333163","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 : 2025-10-11DOI: 10.1016/j.euromechflu.2025.204391
Zihao Zhao, Lingyun Tian, Xiaoyang Xu
This paper proposes an improved multi-resolution smooth particle hydrodynamics (SPH) method for efficiently and accurately simulating the free surface flow of viscous fluids. To address the numerical instabilities arising from interactions between coarse and fine particles due to differences in smoothing length, this study proposes a particle refinement method inspired by adaptive mesh refinement (AMR) and introduces a multi-layer background grid coupling mechanism to improve numerical accuracy while maintaining computational efficiency. To resolve physical field discontinuities at the interface between refined and non-refined regions due to the truncation of the smoothing kernel, buffer particles (including child guard and parent guard particles) are introduced on both sides of the refined region. The physical properties of hidden parent guard particles are updated by fine particles within the fine background grid, ensuring a smooth transition of physical quantities between coarse and fine particle regions. To mitigate tensile instability caused by irregular particle distribution, the particle shifting technique is further enhanced, improving the stability of multi-resolution simulations. Finally, comparisons with single-resolution simulations of dam-break flow, hydrostatic water column, and F-shaped cavity flow demonstrate that the proposed method significantly improves computational efficiency while maintaining high accuracy, thus confirming its effectiveness and robustness.
{"title":"An improved weakly compressible multi-resolution SPH method for free-surface flow simulation","authors":"Zihao Zhao, Lingyun Tian, Xiaoyang Xu","doi":"10.1016/j.euromechflu.2025.204391","DOIUrl":"10.1016/j.euromechflu.2025.204391","url":null,"abstract":"<div><div>This paper proposes an improved multi-resolution smooth particle hydrodynamics (SPH) method for efficiently and accurately simulating the free surface flow of viscous fluids. To address the numerical instabilities arising from interactions between coarse and fine particles due to differences in smoothing length, this study proposes a particle refinement method inspired by adaptive mesh refinement (AMR) and introduces a multi-layer background grid coupling mechanism to improve numerical accuracy while maintaining computational efficiency. To resolve physical field discontinuities at the interface between refined and non-refined regions due to the truncation of the smoothing kernel, buffer particles (including child guard and parent guard particles) are introduced on both sides of the refined region. The physical properties of hidden parent guard particles are updated by fine particles within the fine background grid, ensuring a smooth transition of physical quantities between coarse and fine particle regions. To mitigate tensile instability caused by irregular particle distribution, the particle shifting technique is further enhanced, improving the stability of multi-resolution simulations. Finally, comparisons with single-resolution simulations of dam-break flow, hydrostatic water column, and F-shaped cavity flow demonstrate that the proposed method significantly improves computational efficiency while maintaining high accuracy, thus confirming its effectiveness and robustness.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204391"},"PeriodicalIF":2.5,"publicationDate":"2025-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333159","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 : 2025-10-10DOI: 10.1016/j.euromechflu.2025.204387
Lun Sun , Ri Zhang , Zhongwei Zhou , Jifu Yin , D.D. Meringolo
This paper experimentally investigates the effect of particle-particle and particle-wall interactions on the settling process of spherical particles. A convergence binocular calibration technique was used to capture the settling process under three typical conditions: (a) individual spherical particles settling at the center of the tank, (b) individual spherical particles settling near the wall, and (c) two symmetric spherical particles settling at the center of the tank. The ratio of initial particle-particle or particle-wall gap to the particle diameter is defined as a dimensionless parameter Gap. For individual particles released near the wall, when Gap is within 1.5, the wall significantly suppresses the random deflection characteristics typically observed for individual spherical particles settling at the tank center. Similarly, for two symmetric particles, random deflection is markedly suppressed, with highly symmetrical settling velocities and trajectories. The settling behavior of an individual spherical particle near the wall closely resembles that of the wall-facing particle in the symmetric-pair case, indicating that the wall effectively acts as a mirror. Additionally, Gap exerts little influence on the final mean settling velocity for either individual particles released near the wall or twin particles released at the center of the water tank.
{"title":"Influences of particle-particle and particle-wall interactions on the settling behaviors of the centimeter-sized spherical particles","authors":"Lun Sun , Ri Zhang , Zhongwei Zhou , Jifu Yin , D.D. Meringolo","doi":"10.1016/j.euromechflu.2025.204387","DOIUrl":"10.1016/j.euromechflu.2025.204387","url":null,"abstract":"<div><div>This paper experimentally investigates the effect of particle-particle and particle-wall interactions on the settling process of spherical particles. A convergence binocular calibration technique was used to capture the settling process under three typical conditions: (a) individual spherical particles settling at the center of the tank, (b) individual spherical particles settling near the wall, and (c) two symmetric spherical particles settling at the center of the tank. The ratio of initial particle-particle or particle-wall gap to the particle diameter is defined as a dimensionless parameter <em>Gap.</em> For individual particles released near the wall, when <em>Gap</em> is within 1.5, the wall significantly suppresses the random deflection characteristics typically observed for individual spherical particles settling at the tank center. Similarly, for two symmetric particles, random deflection is markedly suppressed, with highly symmetrical settling velocities and trajectories. The settling behavior of an individual spherical particle near the wall closely resembles that of the wall-facing particle in the symmetric-pair case, indicating that the wall effectively acts as a mirror. Additionally, <em>Gap</em> exerts little influence on the final mean settling velocity for either individual particles released near the wall or twin particles released at the center of the water tank.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204387"},"PeriodicalIF":2.5,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267615","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 : 2025-10-10DOI: 10.1016/j.euromechflu.2025.204388
Qingchun Zhou, Xiaowei Liu, Chunji Hu
Active rotation is commonly employed in traditional enhanced heat dissipation applications. However, passive rotation, which operates without external energy input, leverages environmental energy more effectively, showing great potential for enhanced heat transfer applications. This study explores the impact of passive rotation on the heat transfer characteristics of single-degree-of-freedom transverse vibrations in circular cylinders and square prisms. Numerical simulations were performed under the conditions of Re = 100, m* = 2, ζ = 0, and Pr = 0.7. The results show that the rotational degree of freedom has minimal influence on the heat transfer of circular cylinders, with only a 1.11 % increase in Nusselt number. In contrast, it significantly enhances heat transfer in square prisms, leading to a 14.21 % increase. Further analysis reveals that the rotational degree of freedom transitions the vibration mode from pure vortex-induced vibration (VIV) to a combination of VIV and galloping, which is the primary mechanism behind the heat transfer enhancement. Flow field analysis indicates that this transition strengthens vortex intensity and disturbs the thermal boundary layer, providing a microscopic explanation for the observed heat transfer improvements. The introduction of rotational freedom in such systems offers a novel and effective approach to enhance heat transfer performance.
{"title":"Study on the influence of the rotational degree of freedom on the heat transfer of single-y vibrating blunt bodies","authors":"Qingchun Zhou, Xiaowei Liu, Chunji Hu","doi":"10.1016/j.euromechflu.2025.204388","DOIUrl":"10.1016/j.euromechflu.2025.204388","url":null,"abstract":"<div><div>Active rotation is commonly employed in traditional enhanced heat dissipation applications. However, passive rotation, which operates without external energy input, leverages environmental energy more effectively, showing great potential for enhanced heat transfer applications. This study explores the impact of passive rotation on the heat transfer characteristics of single-degree-of-freedom transverse vibrations in circular cylinders and square prisms. Numerical simulations were performed under the conditions of <em>Re</em> = 100, <em>m</em>* = 2, <em>ζ</em> = 0, and <em>Pr</em> = 0.7. The results show that the rotational degree of freedom has minimal influence on the heat transfer of circular cylinders, with only a 1.11 % increase in Nusselt number. In contrast, it significantly enhances heat transfer in square prisms, leading to a 14.21 % increase. Further analysis reveals that the rotational degree of freedom transitions the vibration mode from pure vortex-induced vibration (VIV) to a combination of VIV and galloping, which is the primary mechanism behind the heat transfer enhancement. Flow field analysis indicates that this transition strengthens vortex intensity and disturbs the thermal boundary layer, providing a microscopic explanation for the observed heat transfer improvements. The introduction of rotational freedom in such systems offers a novel and effective approach to enhance heat transfer performance.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204388"},"PeriodicalIF":2.5,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266752","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 : 2025-10-09DOI: 10.1016/j.euromechflu.2025.204386
Dhananjay Yadav , Houda Al Maqbali , Mukesh Kumar Awasthi , Ravi Ragoju , Saif Al Aghbari , Maryam Al Aameriya , Basama Al Hanai , Asma Al Malki , Ljina Al Aamri
This study investigates how linear and exponential variations in temperature-dependent viscosity influence the initiation of thermo-bioconvective flow in a non-Newtonian Jeffrey fluid with gravitactic microorganisms present in a permeable medium, which has not been addressed in the existing literature. The threshold of the thermo-bioconvective flow, taking into account the absence of microorganism flux at the boundaries, is determined through linear stability theory, and the corresponding eigenvalue problem is resolved analytically using the Galerkin method. The findings indicate that when viscosity changes linearly with temperature, the critical Rayleigh number at which the system starts convection is approximately 11 % higher than when viscosity changes exponentially with temperature. This shows that the system is more unstable when viscosity changes exponentially with temperature compared to a linear change. The stability of the arrangement decreases as the bio Rayleigh-Darcy number, the bio Péclet number, the Jeffrey factor, and the viscosity deviation parameter increase. In instances of exponential viscosity variation with temperature, the size of the convective cells grows with the viscosity deviation parameter, while it remains constant in the case of linear viscosity variation. Additionally, it is important to emphasize that oscillatory convective motion is not relevant to the current analysis.
{"title":"Impact of temperature dependent viscosity on thermo-bioconvective flow of Jeffrey fluid containing gravitactic microorganism in a permeable medium","authors":"Dhananjay Yadav , Houda Al Maqbali , Mukesh Kumar Awasthi , Ravi Ragoju , Saif Al Aghbari , Maryam Al Aameriya , Basama Al Hanai , Asma Al Malki , Ljina Al Aamri","doi":"10.1016/j.euromechflu.2025.204386","DOIUrl":"10.1016/j.euromechflu.2025.204386","url":null,"abstract":"<div><div>This study investigates how linear and exponential variations in temperature-dependent viscosity influence the initiation of thermo-bioconvective flow in a non-Newtonian Jeffrey fluid with gravitactic microorganisms present in a permeable medium, which has not been addressed in the existing literature. The threshold of the thermo-bioconvective flow, taking into account the absence of microorganism flux at the boundaries, is determined through linear stability theory, and the corresponding eigenvalue problem is resolved analytically using the Galerkin method. The findings indicate that when viscosity changes linearly with temperature, the critical Rayleigh number<span><math><msubsup><mrow><mi>R</mi></mrow><mrow><mi>D</mi><mo>,</mo><mi>c</mi></mrow><mrow><mi>E</mi><mi>x</mi></mrow></msubsup></math></span> at which the system starts convection is approximately 11 % higher than when viscosity changes exponentially with temperature. This shows that the system is more unstable when viscosity changes exponentially with temperature compared to a linear change. The stability of the arrangement decreases as the bio Rayleigh-Darcy number<span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>B</mi><mi>D</mi></mrow></msub></math></span>, the bio Péclet number<span><math><mrow><mi>P</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>B</mi></mrow></msub></mrow></math></span>, the Jeffrey factor<span><math><mi>γ</mi></math></span>, and the viscosity deviation parameter<span><math><mi>F</mi></math></span> increase. In instances of exponential viscosity variation with temperature, the size of the convective cells grows with the viscosity deviation parameter<span><math><mi>F</mi></math></span>, while it remains constant in the case of linear viscosity variation. Additionally, it is important to emphasize that oscillatory convective motion is not relevant to the current analysis.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204386"},"PeriodicalIF":2.5,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267618","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 : 2025-10-09DOI: 10.1016/j.euromechflu.2025.204384
H. Thomas , R. Stuhlmeier , A.G.L. Borthwick , S. Michele
With the growing abundance of man-made cylindrical structures located on or close to the seabed, it is important to be able to assess their potential environmental impact. Herein, a model is presented of the viscous-thermal boundary layer in the vicinity of a circular cylinder resting on, or partially buried in, an otherwise flat seabed. To model the influence of wave-induced motions near such a cylinder, we assume oscillatory flow in which the water particle displacements are small with respect to the cylinder radius. A perturbation expansion is utilised to derive solutions of the boundary layer equations, leading to analytical solutions at multiple orders. The unsteady temperature field for various burial depths is then determined numerically using a Crank–Nicolson scheme, and quantitative results, such as the Nusselt number at the cylinder surface, are deduced. Both diffusion and steady convection are responsible for the unsteady transport of temperature. The dynamics of the convective field enhance overall heat transfer from the cylinder and lead to the temperature being transported radially outward near to the seabed.
{"title":"Heat transfer from a partially buried circular cylinder in oscillatory flow","authors":"H. Thomas , R. Stuhlmeier , A.G.L. Borthwick , S. Michele","doi":"10.1016/j.euromechflu.2025.204384","DOIUrl":"10.1016/j.euromechflu.2025.204384","url":null,"abstract":"<div><div>With the growing abundance of man-made cylindrical structures located on or close to the seabed, it is important to be able to assess their potential environmental impact. Herein, a model is presented of the viscous-thermal boundary layer in the vicinity of a circular cylinder resting on, or partially buried in, an otherwise flat seabed. To model the influence of wave-induced motions near such a cylinder, we assume oscillatory flow in which the water particle displacements are small with respect to the cylinder radius. A perturbation expansion is utilised to derive solutions of the boundary layer equations, leading to analytical solutions at multiple orders. The unsteady temperature field for various burial depths is then determined numerically using a Crank–Nicolson scheme, and quantitative results, such as the Nusselt number at the cylinder surface, are deduced. Both diffusion and steady convection are responsible for the unsteady transport of temperature. The dynamics of the convective field enhance overall heat transfer from the cylinder and lead to the temperature being transported radially outward near to the seabed.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204384"},"PeriodicalIF":2.5,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333162","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 : 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":"2025-10-08","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 : 2025-10-06DOI: 10.1016/j.euromechflu.2025.204383
Chunwang Yan , Yanyan Zhang , Yu Zhang
We develop a van der Waals drift-flux model to describe gas–liquid two-phase flow and solve its Riemann problem analytically. Employing a unified parametric approach, we derive the exact expressions for all elementary waves and rigorously establish the existence and uniqueness of solutions. Additionally, we propose a simple criterion to determine whether shocks or rarefaction waves arise in the 1-family and 3-family. Finally, the theoretical analysis is confirmed by numerical simulation. This work presents a comprehensive analysis of the Riemann problem for the drift-flux model with non-ideal gas, providing an exact mathematical framework for studying the non-ideal two-phase flow dynamics.
{"title":"Exact Riemann solutions for the drift-flux model of gas–liquid two-phase flows with van der Waals gas","authors":"Chunwang Yan , Yanyan Zhang , Yu Zhang","doi":"10.1016/j.euromechflu.2025.204383","DOIUrl":"10.1016/j.euromechflu.2025.204383","url":null,"abstract":"<div><div>We develop a van der Waals drift-flux model to describe gas–liquid two-phase flow and solve its Riemann problem analytically. Employing a unified parametric approach, we derive the exact expressions for all elementary waves and rigorously establish the existence and uniqueness of solutions. Additionally, we propose a simple criterion to determine whether shocks or rarefaction waves arise in the 1-family and 3-family. Finally, the theoretical analysis is confirmed by numerical simulation. This work presents a comprehensive analysis of the Riemann problem for the drift-flux model with non-ideal gas, providing an exact mathematical framework for studying the non-ideal two-phase flow dynamics.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204383"},"PeriodicalIF":2.5,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267617","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 : 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":"2025-10-04","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}
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