Pub Date : 2026-01-01Epub 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":"2026-01-01","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 : 2026-01-01Epub Date: 2025-09-17DOI: 10.1016/j.euromechflu.2025.204374
Oleg A. Logvinov , Isabel M. Irurzun
We considered the high-speed displacement of fluids from a Hele-Shaw cell where jumps on the interface in both viscosity and density drive the instability and the generation of viscous fingers. Mathematically, the density is a prior factor in the inertial nonlinear terms in the full–averaged Navier–Stokes–Darcy model. Therefore, we investigated the influence of inertial effects on the fingering process. We performed linear stability analysis and numerical simulations by finite–difference method considering dependences on two dimensionless parameters: density ratio and Reynolds number. Two main conclusions could be drawn. The first is that as the Reynolds number increases, the interface becomes more stable in the initial phase of displacement. The second is that the displacement of a denser fluid by a less dense one is more unstable than the opposite case, where a denser fluid displaces a less dense one. We also performed nonlinear simulations that also showed pronounced viscous bubble formation even when the viscosity ratio was relatively small.
{"title":"Density jump in high-speed Hele-Shaw flows","authors":"Oleg A. Logvinov , Isabel M. Irurzun","doi":"10.1016/j.euromechflu.2025.204374","DOIUrl":"10.1016/j.euromechflu.2025.204374","url":null,"abstract":"<div><div>We considered the high-speed displacement of fluids from a Hele-Shaw cell where jumps on the interface in both viscosity and density drive the instability and the generation of viscous fingers. Mathematically, the density is a prior factor in the inertial nonlinear terms in the full–averaged Navier–Stokes–Darcy model. Therefore, we investigated the influence of inertial effects on the fingering process. We performed linear stability analysis and numerical simulations by finite–difference method considering dependences on two dimensionless parameters: density ratio and Reynolds number. Two main conclusions could be drawn. The first is that as the Reynolds number increases, the interface becomes more stable in the initial phase of displacement. The second is that the displacement of a denser fluid by a less dense one is more unstable than the opposite case, where a denser fluid displaces a less dense one. We also performed nonlinear simulations that also showed pronounced viscous bubble formation even when the viscosity ratio was relatively small.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204374"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106559","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: 2025-09-13DOI: 10.1016/j.euromechflu.2025.204366
Alexey E. Rastegin
Welander’s approach to study convective motions in a differentially spot-heated loop is reformulated for the case of fluid near the temperature of maximum density. The existence of this temperature is of great importance to understand dynamics of temperate lakes. The key character of the case of interest is that heat exchange takes place only within small spots at the bottom and the top of the loop. This study aims to reveal what happens with convective motions when fluid is near a state with the zero coefficient of thermal expansion. A somehow surprising conclusion is that steady regimes of convection, when they exist, turn out to be stable. This outcome differs from the case when heat exchange with the environment in line with Newton’s law of cooling takes place in a whole range of the loop. The findings of theoretical analysis are supported by the results of numerical studies. The reported outcomes allow us to estimate peculiarities of building more complex models of thermal convection. In particular, the role of spot-heated character of exchange with the environment is demonstrated. This feature should be kept in mind in attempts to simulate natural convection on the base of idealized models.
{"title":"On the stable convection in a differentially spot-heated loop near the temperature of maximum density","authors":"Alexey E. Rastegin","doi":"10.1016/j.euromechflu.2025.204366","DOIUrl":"10.1016/j.euromechflu.2025.204366","url":null,"abstract":"<div><div>Welander’s approach to study convective motions in a differentially spot-heated loop is reformulated for the case of fluid near the temperature of maximum density. The existence of this temperature is of great importance to understand dynamics of temperate lakes. The key character of the case of interest is that heat exchange takes place only within small spots at the bottom and the top of the loop. This study aims to reveal what happens with convective motions when fluid is near a state with the zero coefficient of thermal expansion. A somehow surprising conclusion is that steady regimes of convection, when they exist, turn out to be stable. This outcome differs from the case when heat exchange with the environment in line with Newton’s law of cooling takes place in a whole range of the loop. The findings of theoretical analysis are supported by the results of numerical studies. The reported outcomes allow us to estimate peculiarities of building more complex models of thermal convection. In particular, the role of spot-heated character of exchange with the environment is demonstrated. This feature should be kept in mind in attempts to simulate natural convection on the base of idealized models.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204366"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106558","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.2025.204389
Nabila Naz
The electrohydrodynamics (EHD) of droplets under electric fields underpins technologies from ink-jet printing and electrosprays to droplet sorting and microfluidics, yet accurate prediction remains challenging because most existing studies are confined to two-dimensional or axisymmetric models and often neglect surface-charge convection, a mechanism that strongly modifies interfacial stresses and breakup. To address this gap, we develop a fully three-dimensional (3D) level-set computational framework for leaky–dielectric two-phase flows that resolves bulk charge conservation, interfacial surface-charge convection, and topology change over a wide range of electric Reynolds numbers (the ratio of charge-relaxation to convection time) and electric capillary numbers (the ratio of electric stress to surface tension). Unlike existing three-dimensional studies that either neglect surface-charge convection or are restricted to small deformations without breakup, our framework provides a comprehensive 3D treatment of finite- charge convection, topology change, and breakup mapping. The method is carefully verified (mass conservation error ) and validated against Taylor’s small-deformation theory and silicone–castor oil experiments, confirming quantitative accuracy. Our simulations demonstrate that surface-charge convection redistributes interfacial charges, weakens EHD circulation, suppresses oblate deformation, and enhances prolate deformation; three-dimensional charge maps and two-dimensional cross-sectional contours quantify these effects in detail. For prolate drops, we capture and classify breakup transitions in full 3D — from end-pinching to conic cusping and ultimately tip streaming — and construct a comprehensive phase diagram. By integrating finite- effects, 3D surface-charge diagnostics, and breakup mapping in a validated computational method, this study establishes a novel predictive framework for electric-field-driven droplet technologies.
{"title":"A three-dimensional level set method for two-phase electrohydrodynamics with finite electric Reynolds number","authors":"Nabila Naz","doi":"10.1016/j.euromechflu.2025.204389","DOIUrl":"10.1016/j.euromechflu.2025.204389","url":null,"abstract":"<div><div>The electrohydrodynamics (EHD) of droplets under electric fields underpins technologies from ink-jet printing and electrosprays to droplet sorting and microfluidics, yet accurate prediction remains challenging because most existing studies are confined to two-dimensional or axisymmetric models and often neglect surface-charge convection, a mechanism that strongly modifies interfacial stresses and breakup. To address this gap, we develop a fully three-dimensional (3D) level-set computational framework for leaky–dielectric two-phase flows that resolves bulk charge conservation, interfacial surface-charge convection, and topology change over a wide range of electric Reynolds numbers <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>E</mi></mrow></msub></mrow></math></span> (the ratio of charge-relaxation to convection time) and electric capillary numbers <span><math><mrow><mi>C</mi><msub><mrow><mi>a</mi></mrow><mrow><mi>E</mi></mrow></msub></mrow></math></span> (the ratio of electric stress to surface tension). Unlike existing three-dimensional studies that either neglect surface-charge convection or are restricted to small deformations without breakup, our framework provides a comprehensive 3D treatment of finite-<span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>E</mi></mrow></msub></mrow></math></span> charge convection, topology change, and breakup mapping. The method is carefully verified (mass conservation error <span><math><mrow><mo><</mo><mn>0</mn><mo>.</mo><mn>5</mn><mtext>%</mtext></mrow></math></span>) and validated against Taylor’s small-deformation theory and silicone–castor oil experiments, confirming quantitative accuracy. Our simulations demonstrate that surface-charge convection redistributes interfacial charges, weakens EHD circulation, suppresses oblate deformation, and enhances prolate deformation; three-dimensional charge maps and two-dimensional cross-sectional contours quantify these effects in detail. For prolate drops, we capture and classify breakup transitions in full 3D — from end-pinching to conic cusping and ultimately tip streaming — and construct a comprehensive <span><math><mrow><mo>(</mo><mi>C</mi><msub><mrow><mi>a</mi></mrow><mrow><mi>E</mi></mrow></msub><mo>,</mo><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>E</mi></mrow></msub><mo>)</mo></mrow></math></span> phase diagram. By integrating finite-<span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>E</mi></mrow></msub></mrow></math></span> effects, 3D surface-charge diagnostics, and breakup mapping in a validated computational method, this study establishes a novel predictive framework for electric-field-driven droplet technologies.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204389"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333092","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: 2025-10-18DOI: 10.1016/j.euromechflu.2025.204393
Weiyu Shen , Rodolfo Ostilla-Mónico , Xiaojue Zhu
Solar atmosphere hosts intricate interactions between vortex tubes and magnetic flux, which channel convective energy into the upper atmosphere and shape large-scale magnetic activity. To probe these dynamics in a controlled setting, we perform direct numerical simulations of antiparallel vortex tubes embedded with magnetic flux tubes, varying the interaction parameter that measures the Lorentz–inertial balance. High-resolution visualizations uncover distinct regimes of coupled evolution, including vortex-dominated reconnection, Lorentz-suppressed reconnection, instability-triggered cascades, and Lorentz-induced vortex disruption. The rendered structures highlight not only the physical transitions but also the striking morphologies, ranging from braided filaments to spiralized cores, that emerge as magnetic intensity strengthens. These findings show how Lorentz–inertial balance regulates reconnection, instability, and energy transfer in magnetohydrodynamic flows.
{"title":"Vortices vs. magnetic fields: Competing orders in flux tubes","authors":"Weiyu Shen , Rodolfo Ostilla-Mónico , Xiaojue Zhu","doi":"10.1016/j.euromechflu.2025.204393","DOIUrl":"10.1016/j.euromechflu.2025.204393","url":null,"abstract":"<div><div>Solar atmosphere hosts intricate interactions between vortex tubes and magnetic flux, which channel convective energy into the upper atmosphere and shape large-scale magnetic activity. To probe these dynamics in a controlled setting, we perform direct numerical simulations of antiparallel vortex tubes embedded with magnetic flux tubes, varying the interaction parameter <span><math><msub><mrow><mi>N</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span> that measures the Lorentz–inertial balance. High-resolution visualizations uncover distinct regimes of coupled evolution, including vortex-dominated reconnection, Lorentz-suppressed reconnection, instability-triggered cascades, and Lorentz-induced vortex disruption. The rendered structures highlight not only the physical transitions but also the striking morphologies, ranging from braided filaments to spiralized cores, that emerge as magnetic intensity strengthens. These findings show how Lorentz–inertial balance regulates reconnection, instability, and energy transfer in magnetohydrodynamic flows.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204393"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333093","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: 2025-09-10DOI: 10.1016/j.euromechflu.2025.204348
Aritras Roy , Rinku Mukherjee
<div><div>The ability of a morphed wing to prevent 3D flow separation when operating at high angles of attack and when the flow past it is unsteady is investigated. The wing is morphed using an external skin attached to the leading edge of the wing, which takes the shape of the suction/top surface of the wing, when not in use. When required, the external skin is deployed but with a new shape, which is a morphed version of the top surface of the wing and has the ability to prevent flow separation. The shape of the external skin is predicted using a numerical algorithm developed for this purpose that couples an Unsteady Vortex Lattice Method with another in-house steady-state Vortex Lattice Method algorithm that uses a ‘decambering’ concept to ‘correct’ the local camberline to account for flow separation. Physical wing models are then fabricated along with the numerically predicted morphed surfaces to be attached externally at the leading edge and tested in the wind tunnel. Unsteady change in angle of attack is implemented using an in-house mechanism developed for this purpose, where the rate of change of angle of attack, <span><math><mrow><mfrac><mrow><mi>∂</mi><mi>α</mi></mrow><mrow><mi>∂</mi><mi>t</mi></mrow></mfrac><mo>=</mo><mover><mrow><mi>α</mi></mrow><mrow><mo>̇</mo></mrow></mover></mrow></math></span> is varied as <span><math><mrow><mn>0</mn><mo>.</mo><mn>1</mn><mo>°</mo><mo>/</mo><mi>s</mi><mo><</mo><mover><mrow><mi>α</mi></mrow><mrow><mo>̇</mo></mrow></mover><mo><</mo><mn>1</mn><mo>°</mo><mo>/</mo><mi>s</mi></mrow></math></span>. Unsteady aerodynamic characteristics like <span><math><mrow><msub><mrow><mi>C</mi></mrow><mrow><mi>L</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>,</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>D</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>,</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>M</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow></mrow></math></span> are measured for change in Reynolds number, <span><math><mrow><mn>0</mn><mo>.</mo><mn>045</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6</mn></mrow></msup><mo><</mo><mi>R</mi><mi>e</mi><mo><</mo><mn>0</mn><mo>.</mo><mn>1</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6</mn></mrow></msup></mrow></math></span>. Flow visualization using smoke is conducted in the wind tunnel. CFD is also used to study such a morphing wing at high angles of attack including at post-stall. Spectral densities of the transient load data, <span><math><mrow><msub><mrow><mi>C</mi></mrow><mrow><mi>L</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>,</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>D</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow></mrow></math></span> and unsteady sectional lift coefficient, <span><math><mrow><msub><mrow><mi>C</mi></mrow><mrow><msub><mrow><mi>l</mi></mrow><mrow><mi>s</mi><mi>e</mi><mi>c</mi></mrow></msub></mrow></msub><mrow><mo>(</mo><mi>t
{"title":"Unsteady aerodynamics of the control of three dimensional flow separation by morphing a wing surface","authors":"Aritras Roy , Rinku Mukherjee","doi":"10.1016/j.euromechflu.2025.204348","DOIUrl":"10.1016/j.euromechflu.2025.204348","url":null,"abstract":"<div><div>The ability of a morphed wing to prevent 3D flow separation when operating at high angles of attack and when the flow past it is unsteady is investigated. The wing is morphed using an external skin attached to the leading edge of the wing, which takes the shape of the suction/top surface of the wing, when not in use. When required, the external skin is deployed but with a new shape, which is a morphed version of the top surface of the wing and has the ability to prevent flow separation. The shape of the external skin is predicted using a numerical algorithm developed for this purpose that couples an Unsteady Vortex Lattice Method with another in-house steady-state Vortex Lattice Method algorithm that uses a ‘decambering’ concept to ‘correct’ the local camberline to account for flow separation. Physical wing models are then fabricated along with the numerically predicted morphed surfaces to be attached externally at the leading edge and tested in the wind tunnel. Unsteady change in angle of attack is implemented using an in-house mechanism developed for this purpose, where the rate of change of angle of attack, <span><math><mrow><mfrac><mrow><mi>∂</mi><mi>α</mi></mrow><mrow><mi>∂</mi><mi>t</mi></mrow></mfrac><mo>=</mo><mover><mrow><mi>α</mi></mrow><mrow><mo>̇</mo></mrow></mover></mrow></math></span> is varied as <span><math><mrow><mn>0</mn><mo>.</mo><mn>1</mn><mo>°</mo><mo>/</mo><mi>s</mi><mo><</mo><mover><mrow><mi>α</mi></mrow><mrow><mo>̇</mo></mrow></mover><mo><</mo><mn>1</mn><mo>°</mo><mo>/</mo><mi>s</mi></mrow></math></span>. Unsteady aerodynamic characteristics like <span><math><mrow><msub><mrow><mi>C</mi></mrow><mrow><mi>L</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>,</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>D</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>,</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>M</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow></mrow></math></span> are measured for change in Reynolds number, <span><math><mrow><mn>0</mn><mo>.</mo><mn>045</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6</mn></mrow></msup><mo><</mo><mi>R</mi><mi>e</mi><mo><</mo><mn>0</mn><mo>.</mo><mn>1</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6</mn></mrow></msup></mrow></math></span>. Flow visualization using smoke is conducted in the wind tunnel. CFD is also used to study such a morphing wing at high angles of attack including at post-stall. Spectral densities of the transient load data, <span><math><mrow><msub><mrow><mi>C</mi></mrow><mrow><mi>L</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>,</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>D</mi></mrow></msub><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow></mrow></math></span> and unsteady sectional lift coefficient, <span><math><mrow><msub><mrow><mi>C</mi></mrow><mrow><msub><mrow><mi>l</mi></mrow><mrow><mi>s</mi><mi>e</mi><mi>c</mi></mrow></msub></mrow></msub><mrow><mo>(</mo><mi>t","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204348"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145026327","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: 2025-09-26DOI: 10.1016/j.euromechflu.2025.204381
Benedict C.-W. Tan
The collapse of air cavity towards the liquid surface that occurred immediately after deep seal following vertical entry of steel spheres into a pool of oil, was experimentally investigated. The vertical displacement between the pinch-off depth and the cavity base during the time when the cavity was collapsing towards the surface, was regularly measured and analysed using images taken from a high-speed camera. Furthermore, some phenomena associated with the upward oil jet generated during cavity collapse were also described and briefly studied. The results suggested that the rate of cavity collapse towards the surface, and the time taken for the lower part of the oil jet to reach surface level, were dependent on both the inertial and gravitational forces of the spheres.
{"title":"Cavity collapse associated with oil entry of steel spheres","authors":"Benedict C.-W. Tan","doi":"10.1016/j.euromechflu.2025.204381","DOIUrl":"10.1016/j.euromechflu.2025.204381","url":null,"abstract":"<div><div>The collapse of air cavity towards the liquid surface that occurred immediately after deep seal following vertical entry of steel spheres into a pool of oil, was experimentally investigated. The vertical displacement between the pinch-off depth and the cavity base during the time when the cavity was collapsing towards the surface, was regularly measured and analysed using images taken from a high-speed camera. Furthermore, some phenomena associated with the upward oil jet generated during cavity collapse were also described and briefly studied. The results suggested that the rate of cavity collapse towards the surface, and the time taken for the lower part of the oil jet to reach surface level, were dependent on both the inertial and gravitational forces of the spheres.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204381"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145155615","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}
Understanding and controlling transitions in wall-bounded flows through porous substrates are essential for designing and improving engineering systems. This study examines the linear stability of electrically conducting plane Couette flow within a Brinkman porous layer that is mechanically anisotropic and bounded by permeable walls with uniform cross-flow (injection at the lower wall, suction at the upper wall) under an applied magnetic field. A normal-mode linearisation leads to a modified Orr-Sommerfeld eigenvalue problem, which is solved using Chebyshev spectral collocation to identify neutral curves and growth-rate patterns as variables such as the Darcy number, Hartmann number, mechanical anisotropy, perturbation wavenumber, phase angle, cross-flow Reynolds number, and the orientation of the principal permeability axis are varied. Results show that increasing the Darcy number and Hartmann number stabilizes the flow, while a higher perturbation wavenumber reduces amplification, meaning disturbances grow most at longer wavelengths. Mechanical anisotropy consistently destabilizes the flow, increasing peak growth rates, whereas changes in the orientation angle have little effect. The phase angle has a slight influence on stability at low wavenumbers but tends to stabilize the flow at higher wavenumbers. Meanwhile, the cross-flow Reynolds number causes only minor shifts in the neutral curves. These findings suggest practical methods for flow control in anisotropic porous magnetohydrodynamic systems, highlighting the stabilizing effects of magnetic damping and porous-matrix diffusion, as well as the destabilizing impact of strong anisotropy.
{"title":"Stability of hydromagnetic Couette flow in an anisotropic porous medium with oblique principal axes and constant wall transpiration","authors":"Cédric Gervais Njingang Ketchate , Alain Dika , Pascalin Tiam Kapen , Didier Fokwa","doi":"10.1016/j.euromechflu.2025.204376","DOIUrl":"10.1016/j.euromechflu.2025.204376","url":null,"abstract":"<div><div>Understanding and controlling transitions in wall-bounded flows through porous substrates are essential for designing and improving engineering systems. This study examines the linear stability of electrically conducting plane Couette flow within a Brinkman porous layer that is mechanically anisotropic and bounded by permeable walls with uniform cross-flow (injection at the lower wall, suction at the upper wall) under an applied magnetic field. A normal-mode linearisation leads to a modified Orr-Sommerfeld eigenvalue problem, which is solved using Chebyshev spectral collocation to identify neutral curves and growth-rate patterns as variables such as the Darcy number, Hartmann number, mechanical anisotropy, perturbation wavenumber, phase angle, cross-flow Reynolds number, and the orientation of the principal permeability axis are varied. Results show that increasing the Darcy number and Hartmann number stabilizes the flow, while a higher perturbation wavenumber reduces amplification, meaning disturbances grow most at longer wavelengths. Mechanical anisotropy consistently destabilizes the flow, increasing peak growth rates, whereas changes in the orientation angle have little effect. The phase angle has a slight influence on stability at low wavenumbers but tends to stabilize the flow at higher wavenumbers. Meanwhile, the cross-flow Reynolds number causes only minor shifts in the neutral curves. These findings suggest practical methods for flow control in anisotropic porous magnetohydrodynamic systems, highlighting the stabilizing effects of magnetic damping and porous-matrix diffusion, as well as the destabilizing impact of strong anisotropy.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204376"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217836","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: 2025-10-11DOI: 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":"2026-01-01","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 : 2026-01-01Epub Date: 2025-10-14DOI: 10.1016/j.euromechflu.2025.204395
Mustafa Turkyilmazoglu , Abdulaziz Alotaibi
Building upon a modified Karman–Pohlhausen technique, a recent study by Panfilov (2021) employed spherical coordinates to solve the heat transport problem in a heterogeneous domain surrounding a cavity storing cryogenic fluids underground. This analysis revealed the formation of an ice ring around the cavity, acting as a protective barrier against flooding from the stored material. This present work expands on that research by introducing heat generation and absorption into the media, aiming to analyze the temporal evolution of temperature and its impact on ice ring formation. Such heat exchange could be caused by seasonal fluctuations or geothermal activity. Motivated by these real-world influences, we extend the theoretical framework presented in Panfilov (2021) to investigate the universal evolution of the temperature field in the cavity, insulation, and rock regions. This study will track the emergence, persistence (dependent on heat balance), and eventual disappearance of the ice zone while determining its maximum thickness as a function of various parameters. We anticipate that heat generation will accelerate heat transfer between zones, reducing the perturbation length and consequently shortening the lifespan of the ice ring. Conversely, heat absorption will slow down thermal wave propagation by increasing the perturbation time length, thereby prolonging the freezing front of the ice ring and extending the life of both the ice crust and the cryogenic liquid within the underground cavity.
{"title":"Prolonging the life time of underground ice ring formed in the period of the cryogenic gas storage","authors":"Mustafa Turkyilmazoglu , Abdulaziz Alotaibi","doi":"10.1016/j.euromechflu.2025.204395","DOIUrl":"10.1016/j.euromechflu.2025.204395","url":null,"abstract":"<div><div>Building upon a modified Karman–Pohlhausen technique, a recent study by Panfilov (2021) employed spherical coordinates to solve the heat transport problem in a heterogeneous domain surrounding a cavity storing cryogenic fluids underground. This analysis revealed the formation of an ice ring around the cavity, acting as a protective barrier against flooding from the stored material. This present work expands on that research by introducing heat generation and absorption into the media, aiming to analyze the temporal evolution of temperature and its impact on ice ring formation. Such heat exchange could be caused by seasonal fluctuations or geothermal activity. Motivated by these real-world influences, we extend the theoretical framework presented in Panfilov (2021) to investigate the universal evolution of the temperature field in the cavity, insulation, and rock regions. This study will track the emergence, persistence (dependent on heat balance), and eventual disappearance of the ice zone while determining its maximum thickness as a function of various parameters. We anticipate that heat generation will accelerate heat transfer between zones, reducing the perturbation length and consequently shortening the lifespan of the ice ring. Conversely, heat absorption will slow down thermal wave propagation by increasing the perturbation time length, thereby prolonging the freezing front of the ice ring and extending the life of both the ice crust and the cryogenic liquid within the underground cavity.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"115 ","pages":"Article 204395"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333165","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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