Pub Date : 2024-08-07DOI: 10.1103/physrevfluids.9.l081101
Cyril Karamaoun, Haribalan Kumar, Médéric Argentina, Didier Clamond, Benjamin Mauroy
The mucus on the bronchial wall forms a thin layer of non-Newtonian fluid, protecting the lungs by capturing inhaled pollutants. Due to the corrugation of its interface with air, this layer is subject to surface tension forces that affect its rheology. This physical system is analyzed using lubrication theory and three-dimensional simulations. We characterize the nonlinear behavior of the mucus and show that surface tension effects can displace overly thick mucus layers in airway bifurcations. This movement can disrupt the mucociliary clearance and break the homogeneity of the layer thickness.
{"title":"Curvature-driven transport of thin Bingham fluid layers in airway bifurcations","authors":"Cyril Karamaoun, Haribalan Kumar, Médéric Argentina, Didier Clamond, Benjamin Mauroy","doi":"10.1103/physrevfluids.9.l081101","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.l081101","url":null,"abstract":"The mucus on the bronchial wall forms a thin layer of non-Newtonian fluid, protecting the lungs by capturing inhaled pollutants. Due to the corrugation of its interface with air, this layer is subject to surface tension forces that affect its rheology. This physical system is analyzed using lubrication theory and three-dimensional simulations. We characterize the nonlinear behavior of the mucus and show that surface tension effects can displace overly thick mucus layers in airway bifurcations. This movement can disrupt the mucociliary clearance and break the homogeneity of the layer thickness.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"37 3 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-05DOI: 10.1103/physrevfluids.9.084601
J. Dey
Distribution of the mean streamwise velocity in a turbulent boundary layer over a flat plate can be represented by the equation , as was widely used in the past; and are the normalized velocity and the wall-normal distance, respectively. However, this -power law is an empirical one. By incorporating either the Reynolds shear stress model of Wei et al. [J. Fluid Mech.969, A3 (2023)], which is in terms of and the (normalized) wall-normal velocity (), or a similar one in the boundary layer equations, it is found that and are related as in the outer region of a flat plate boundary layer; is the flow shape parameter. Along with the distribution of the wall-normal velocity () of Wei et al., the -power law for is obtained by equating the derivative (with respect to ) of with that of . Thus, this empirical power law seems to have a reasonable theoretical basis embedded in it.
平板上湍流边界层的平均流向速度分布可用方程 U∼η1/n 表示，这在过去被广泛使用；U 和 η 分别是归一化速度和壁面法线距离。然而，这个 1/n 次幂定律是一个经验定律。通过将 Wei 等人的雷诺剪应力模型[J. Fluid Mech. 969, A3 (2023)]（以 U 和（归一化）壁面法向速度 (V) 表示）或类似的模型纳入边界层方程，可以发现在平板边界层的外部区域，U 和 V 的关系为 U(H+1)∼V(H-1)；H 是流动形状参数。根据 Wei 等人的壁面法向速度（Vw）分布，将 V 的导数（相对于 η）等同于 Vw 的导数，即可得到 U 的 1/n 次幂律。因此，这一经验幂律似乎具有合理的理论基础。
{"title":"Approximate derivation of the power law for the mean streamwise velocity in a turbulent boundary layer under zero-pressure gradient","authors":"J. Dey","doi":"10.1103/physrevfluids.9.084601","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084601","url":null,"abstract":"Distribution of the mean streamwise velocity in a turbulent boundary layer over a flat plate can be represented by the equation <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>U</mi><mo>∼</mo><msup><mi>η</mi><mrow><mn>1</mn><mo>/</mo><mi>n</mi></mrow></msup></mrow></math>, as was widely used in the past; <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>U</mi></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>η</mi></math> are the normalized velocity and the wall-normal distance, respectively. However, this <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><mo>/</mo><mi>n</mi></mrow><mi mathvariant=\"normal\">th</mi></math>-power law is an empirical one. By incorporating either the Reynolds shear stress model of Wei <i>et al.</i> [<span>J. Fluid Mech.</span> <b>969</b>, A3 (2023)], which is in terms of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>U</mi></math> and the (normalized) wall-normal velocity (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>V</mi></math>), or a similar one in the boundary layer equations, it is found that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>U</mi></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>V</mi></math> are related as <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mi>U</mi><mrow><mo>(</mo><mi>H</mi><mo>+</mo><mn>1</mn><mo>)</mo></mrow></msup><mo>∼</mo><mspace width=\"4pt\"></mspace><msup><mi>V</mi><mrow><mo>(</mo><mi>H</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow></msup></mrow></math> in the outer region of a flat plate boundary layer; <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>H</mi></mrow></math> is the flow shape parameter. Along with the distribution of the wall-normal velocity (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>V</mi><mi>w</mi></msub></math>) of Wei <i>et al.</i>, the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>1</mn><mo>/</mo><mi>n</mi></mrow><mi mathvariant=\"normal\">th</mi></math>-power law for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>U</mi></math> is obtained by equating the derivative (with respect to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>η</mi></math>) of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>V</mi></math> with that of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>V</mi><mi>w</mi></msub></math>. Thus, this empirical power law seems to have a reasonable theoretical basis embedded in it.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"22 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-05DOI: 10.1103/physrevfluids.9.083101
George T. Fortune, Eric Lauga, Raymond E. Goldstein
The humble Petri dish is perhaps the simplest setting in which to examine the locomotion of swimming organisms, particularly those whose body size is tens of microns to millimeters. The fluid layer in such a container has a bottom no-slip surface and a stress-free upper boundary. It is of fundamental interest to understand the flow fields produced by the elementary and composite singularities of Stokes flow in this geometry. Building on the few particular cases that have previously been considered in the literature, we study here the image systems for the primary singularities of Stokes flow subject to such boundary conditions—the Stokeslet, rotlet, source, rotlet dipole, source dipole, and stresslet—paying particular attention to the far-field behavior. In several key situations, the depth-averaged fluid flow is accurately captured by the solution of an associated Brinkman equation whose screening length is proportional to the depth of the fluid layer. The case of hydrodynamic bound states formed by spinning microswimmers near a no-slip surface, discovered first using the alga Volvox, is reconsidered in the geometry of a Petri dish, where the power-law attractive interaction between microswimmers acquires unusual exponentially screened oscillations.
简陋的培养皿也许是研究游泳生物运动的最简单环境，尤其是那些体型只有几十微米到几毫米的生物。这种容器中的流体层具有底部无滑动表面和上部无应力边界。了解这种几何形状中斯托克斯流的基本奇点和复合奇点所产生的流场具有重要意义。基于以前文献中考虑过的少数特殊情况，我们在此研究了斯托克斯流的初级奇点在这种边界条件下的图像系统--斯托克斯小波、小转子、源、小转子偶极子、源偶极子和应力小波--特别关注远场行为。在几种关键情况下，相关布林克曼方程的筛选长度与流体层深度成正比，该方程的求解可准确捕捉深度平均流体流动。首先利用藻类 Volvox 发现的在无滑动表面附近旋转的微游子形成的流体力学束缚状态，在 Petri 碟的几何形状中被重新考虑，微游子之间的幂律吸引力相互作用获得了不寻常的指数屏蔽振荡。
{"title":"Biophysical fluid dynamics in a Petri dish","authors":"George T. Fortune, Eric Lauga, Raymond E. Goldstein","doi":"10.1103/physrevfluids.9.083101","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.083101","url":null,"abstract":"The humble Petri dish is perhaps the simplest setting in which to examine the locomotion of swimming organisms, particularly those whose body size is tens of microns to millimeters. The fluid layer in such a container has a bottom no-slip surface and a stress-free upper boundary. It is of fundamental interest to understand the flow fields produced by the elementary and composite singularities of Stokes flow in this geometry. Building on the few particular cases that have previously been considered in the literature, we study here the image systems for the primary singularities of Stokes flow subject to such boundary conditions—the Stokeslet, rotlet, source, rotlet dipole, source dipole, and stresslet—paying particular attention to the far-field behavior. In several key situations, the depth-averaged fluid flow is accurately captured by the solution of an associated Brinkman equation whose screening length is proportional to the depth of the fluid layer. The case of hydrodynamic bound states formed by spinning microswimmers near a no-slip surface, discovered first using the alga <i>Volvox</i>, is reconsidered in the geometry of a Petri dish, where the power-law attractive interaction between microswimmers acquires unusual exponentially screened oscillations.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"30 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-05DOI: 10.1103/physrevfluids.9.083201
Rui Xiong, Yufeng Han, Wei Cao
In thermochemical nonequilibrium processes, both the nonequilibrium between different kinds of internal energy of molecules and the non-Boltzmann (NB) energy state distribution significantly impact the dissociation rate coefficients. The conventional two-temperature (2-T) model fails to accurately portray these effects, especially the NB effect. Consequently, dissociation rate coefficients calculated by the 2-T model are inaccurate in simulating strong thermochemical nonequilibrium flow, resulting in a surface heat flux inconsistent with experimental data. This article investigates the influencing factor of the NB effect on the dissociation rate coefficient using the state-to-state (STS) method during the zero-dimensional heating process of and . Based on this, we develop a fitting formula to precisely correct the NB effect. Furthermore, we propose an improved model by integrating this fitting formula with the single-group linear maximum entropy model, which considers only the effect of nonequilibrium between different kinds of internal energy. This improved model provides an accurate description of thermochemical nonequilibrium on the dissociation rate coefficients. To validate the effectiveness of the improved model, we simulate the nonequilibrium process following a normal shock. The results demonstrate that in strong thermochemical nonequilibrium flow, compared to the 2-T Park model, the maximum and average discrepancies between the translation temperatures calculated by the improved model and those by the STS method are reduced by more than 68% and 82%, respectively. Additionally, the results closely align with experimental data, indicating that the improved model can accurately depict the effect of thermal nonequilibrium on dissociation rate coefficients.
在热化学非平衡过程中，不同种类分子内能之间的非平衡和非波尔兹曼（NB）能态分布都会对解离速率系数产生重大影响。传统的双温（2-T）模型无法准确描述这些效应，尤其是非玻尔兹曼效应。因此，2-T 模型计算出的解离速率系数在模拟强热化学非平衡流动时并不准确，导致表面热通量与实验数据不一致。本文利用状态对状态（STS）方法研究了 N2 和 O2 零维加热过程中 NB 效应对解离速率系数的影响因素。在此基础上，我们建立了一个拟合公式来精确修正 NB 效应。此外，我们还提出了一个改进模型，将该拟合公式与单组线性最大熵模型相结合，该模型只考虑了不同种类内能之间的非平衡效应。这一改进模型准确地描述了热化学非平衡对解离速率系数的影响。为了验证改进模型的有效性，我们模拟了正常冲击后的非平衡过程。结果表明，在强热化学非平衡流动中，与 2-T Park 模型相比，改进模型计算的平移温度与 STS 方法计算的平移温度之间的最大差异和平均差异分别减少了 68% 和 82% 以上。此外，计算结果与实验数据非常吻合，表明改进模型能够准确描述热非平衡态对解离速率系数的影响。
{"title":"Improved two-temperature model with correction of non-Boltzmann effect for oxygen and nitrogen","authors":"Rui Xiong, Yufeng Han, Wei Cao","doi":"10.1103/physrevfluids.9.083201","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.083201","url":null,"abstract":"In thermochemical nonequilibrium processes, both the nonequilibrium between different kinds of internal energy of molecules and the non-Boltzmann (NB) energy state distribution significantly impact the dissociation rate coefficients. The conventional two-temperature (2-T) model fails to accurately portray these effects, especially the NB effect. Consequently, dissociation rate coefficients calculated by the 2-T model are inaccurate in simulating strong thermochemical nonequilibrium flow, resulting in a surface heat flux inconsistent with experimental data. This article investigates the influencing factor of the NB effect on the dissociation rate coefficient using the state-to-state (STS) method during the zero-dimensional heating process of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">N</mi><mn>2</mn></msub></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"normal\">O</mi><mn>2</mn></msub></math>. Based on this, we develop a fitting formula to precisely correct the NB effect. Furthermore, we propose an improved model by integrating this fitting formula with the single-group linear maximum entropy model, which considers only the effect of nonequilibrium between different kinds of internal energy. This improved model provides an accurate description of thermochemical nonequilibrium on the dissociation rate coefficients. To validate the effectiveness of the improved model, we simulate the nonequilibrium process following a normal shock. The results demonstrate that in strong thermochemical nonequilibrium flow, compared to the 2-T Park model, the maximum and average discrepancies between the translation temperatures calculated by the improved model and those by the STS method are reduced by more than 68% and 82%, respectively. Additionally, the results closely align with experimental data, indicating that the improved model can accurately depict the effect of thermal nonequilibrium on dissociation rate coefficients.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"3 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-05DOI: 10.1103/physrevfluids.9.l082601
Sergio Hoyas, Ricardo Vinuesa, Peter Schmid, Hassan Nagib
Direct numerical simulations (DNSs) are among the most powerful tools for studying turbulent flows. Even though the achievable Reynolds numbers are lower than those obtained through experimental means, DNS offers a clear advantage: The entire velocity field is known, allowing for the evaluation of any desired quantity. This capability includes the computation of derivatives of all relevant terms. One such derivative provides the indicator function, which is the product of the wall distance and the wall-normal derivative of the mean streamwise velocity. This derivative may depend on mesh spacing and distribution, but it is extremely affected by the convergence of the simulation. The indicator function is crucial for understanding inner and outer interactions in wall-bounded flows and describing the overlap region between them. We find a clear dependence of this indicator function on the mesh distributions we examine, raising questions about classical mesh and convergence requirements for DNS and achievable accuracy. Within the framework of the logarithmic plus linear overlap region, coupled with a parametric study of channel flows and some pipe flows, sensitivities of extracted overlap parameters are examined. This study reveals a path to establishing their high- or nearly asymptotic values at modest Reynolds numbers, but larger than the ones used in this work, accessible by high-quality DNS with reasonable cost.
直接数值模拟（DNS）是研究湍流的最强大工具之一。尽管可实现的雷诺数低于通过实验获得的雷诺数，但 DNS 仍具有明显的优势：整个速度场是已知的，因此可以评估任何所需的量。这种能力包括计算所有相关项的导数。其中一个导数就是指示函数，它是壁面距离与平均流向速度的壁面法向导数的乘积。该导数可能取决于网格间距和分布，但受模拟收敛性的影响极大。指标函数对于理解壁面流的内外相互作用以及描述它们之间的重叠区域至关重要。我们发现该指标函数与我们研究的网格分布有明显的依赖关系，这就提出了有关 DNS 的经典网格和收敛要求以及可实现精度的问题。在对数加线性重叠区域的框架内，结合对通道流和一些管道流的参数研究，对提取的重叠参数的敏感性进行了检验。这项研究揭示了在雷诺数不大但大于本研究中使用的雷诺数的情况下，通过高质量 DNS 以合理的成本建立高雷诺数或近似值的途径。
{"title":"Sensitivity study of resolution and convergence requirements for the extended overlap region in wall-bounded turbulence","authors":"Sergio Hoyas, Ricardo Vinuesa, Peter Schmid, Hassan Nagib","doi":"10.1103/physrevfluids.9.l082601","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.l082601","url":null,"abstract":"Direct numerical simulations (DNSs) are among the most powerful tools for studying turbulent flows. Even though the achievable Reynolds numbers are lower than those obtained through experimental means, DNS offers a clear advantage: The entire velocity field is known, allowing for the evaluation of any desired quantity. This capability includes the computation of derivatives of all relevant terms. One such derivative provides the indicator function, which is the product of the wall distance and the wall-normal derivative of the mean streamwise velocity. This derivative may depend on mesh spacing and distribution, but it is extremely affected by the convergence of the simulation. The indicator function is crucial for understanding inner and outer interactions in wall-bounded flows and describing the overlap region between them. We find a clear dependence of this indicator function on the mesh distributions we examine, raising questions about classical mesh and convergence requirements for DNS and achievable accuracy. Within the framework of the logarithmic plus linear overlap region, coupled with a parametric study of channel flows and some pipe flows, sensitivities of extracted overlap parameters are examined. This study reveals a path to establishing their high-<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mtext>Re</mtext><mi>τ</mi></msub></math> or nearly asymptotic values at modest Reynolds numbers, but larger than the ones used in this work, accessible by high-quality DNS with reasonable cost.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"26 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevfluids.9.084301
Anna Ipatova, Alexis Duchesne, H. N. Yoshikawa, Pascal Mariot, Corenthin Leroy, Christine Faille, Ichiro Ueno, Georg F. Dietze, Farzam Zoueshtiagh
We explore the potential for air bubble entrapment beneath micrometer-sized particles following immersion. This investigation employs theoretical, numerical, and experimental methodologies, with a focus on the wetting characteristics of both the particle and its substrate. These properties are crucial in determining the likelihood of entrapment and its impact on the particle's adhesion force to the substrate. The theoretical model provides the mathematical framework to account for the additional force exerted on the particle due to the entrapped bubble, while numerical calculations yield corresponding force values. The results underscore the significant influence of the wettability of both the particle and the substrate on this force. In support of findings of the numerical model, companion experiments were performed. The results demonstrate that the bubbles can indeed be entrapped at microscales underneath micrometric particles. Experimental measurements of detachment force reveal the substantial impact of these entrapped bubbles on the force required to detach particles from a surface. Specifically, the force appears notably higher when either the particle or the substrate, or both, exhibit hydrophobic characteristics. We highlight the alignment observed between numerical calculations and experimental results, while also examining and discussing any identified disparities and their root causes. Lastly, we propose an energy model that predicts the post-detachment configuration of the bubble, determining whether it remains attached to the particle, adheres to the substrate, or splits into daughter bubbles distributed across both surfaces. These findings hold significance for a wide range of industrial applications where the immersion of micrometer-sized entities, such as dirt or bacteria, is common during liquid-based cleaning processes.
{"title":"Retention or repulsion forces induced by bubbles trapped at the base of an immersed microparticle on a substrate","authors":"Anna Ipatova, Alexis Duchesne, H. N. Yoshikawa, Pascal Mariot, Corenthin Leroy, Christine Faille, Ichiro Ueno, Georg F. Dietze, Farzam Zoueshtiagh","doi":"10.1103/physrevfluids.9.084301","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084301","url":null,"abstract":"We explore the potential for air bubble entrapment beneath micrometer-sized particles following immersion. This investigation employs theoretical, numerical, and experimental methodologies, with a focus on the wetting characteristics of both the particle and its substrate. These properties are crucial in determining the likelihood of entrapment and its impact on the particle's adhesion force to the substrate. The theoretical model provides the mathematical framework to account for the additional force exerted on the particle due to the entrapped bubble, while numerical calculations yield corresponding force values. The results underscore the significant influence of the wettability of both the particle and the substrate on this force. In support of findings of the numerical model, companion experiments were performed. The results demonstrate that the bubbles can indeed be entrapped at microscales underneath micrometric particles. Experimental measurements of detachment force reveal the substantial impact of these entrapped bubbles on the force required to detach particles from a surface. Specifically, the force appears notably higher when either the particle or the substrate, or both, exhibit hydrophobic characteristics. We highlight the alignment observed between numerical calculations and experimental results, while also examining and discussing any identified disparities and their root causes. Lastly, we propose an energy model that predicts the post-detachment configuration of the bubble, determining whether it remains attached to the particle, adheres to the substrate, or splits into daughter bubbles distributed across both surfaces. These findings hold significance for a wide range of industrial applications where the immersion of micrometer-sized entities, such as dirt or bacteria, is common during liquid-based cleaning processes.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"23 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevfluids.9.084801
S. Frei, E. Burman, E. Johnson
This article discusses the effect of rotation on the boundary layer in high Reynolds number flow over a ridge using a numerical method based on stabilized finite elements that captures steady solutions up to a Reynolds number of order . The results are validated against boundary layer computations in shallow flows and for deep flows against experimental observations reported in Machicoane et al. [Phys. Rev. Fluids3, 034801 (2018)]. In all cases considered the boundary layer remains attached, even at arbitrarily large Reynolds numbers, provided the Rossby number of the flow is less than some critical Rossby number of order unity. At any fixed Rossby number larger than this critical value, the flow detaches at sufficiently high Reynolds number to form a steady recirculating region in the lee of the ridge. At even higher Reynolds numbers no steady flow is found. This disappearance of steady solutions closely reproduces the transition to unsteadiness seen in the laboratory.
{"title":"Attached and separated rotating flow over a finite height ridge","authors":"S. Frei, E. Burman, E. Johnson","doi":"10.1103/physrevfluids.9.084801","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084801","url":null,"abstract":"This article discusses the effect of rotation on the boundary layer in high Reynolds number flow over a ridge using a numerical method based on stabilized finite elements that captures steady solutions up to a Reynolds number of order <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>10</mn><mn>6</mn></msup></math>. The results are validated against boundary layer computations in shallow flows and for deep flows against experimental observations reported in Machicoane <i>et al.</i> [<span>Phys. Rev. Fluids</span> <b>3</b>, 034801 (2018)]. In all cases considered the boundary layer remains attached, even at arbitrarily large Reynolds numbers, provided the Rossby number of the flow is less than some critical Rossby number of order unity. At any fixed Rossby number larger than this critical value, the flow detaches at sufficiently high Reynolds number to form a steady recirculating region in the lee of the ridge. At even higher Reynolds numbers no steady flow is found. This disappearance of steady solutions closely reproduces the transition to unsteadiness seen in the laboratory.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"20 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevfluids.9.083901
Pietro Carlo Boldini, Benjamin Bugeat, Jurriaan W. R. Peeters, Markus Kloker, Rene Pecnik
In the region close to the thermodynamic critical point and in the proximity of the pseudoboiling (Widom) line, strong property variations substantially alter the growth of modal instabilities, as revealed in Ren et al. [J. Fluid Mech.871, 831 (2019)]. Here, we study nonmodal disturbances in the spatial framework using an eigenvector decomposition of the linearized Navier-Stokes equations under the assumption of locally parallel flow. To account for nonideality, a new energy norm is derived. Several heat transfer scenarios at supercritical pressure are investigated, which are of practical relevance in technical applications. The boundary layers with the fluid at supercritical pressure are heated or cooled by prescribing the wall and free-stream temperatures so that the temperature profile is either entirely subcritical (liquidlike), supercritical (gaslike), or transcritical (across the Widom line). The free-stream Mach number is set to . In the nontranscritical regimes, the resulting streamwise-independent streaks originate from the lift-up effect. Wall cooling enhances the energy amplification for both subcritical and supercritical regimes. When the temperature profile is increased beyond the Widom line, a strong suboptimal growth is observed over very short streamwise distances due to the Orr mechanism. Due to the additional presence of transcritical Mode II, the optimal energy growth at large distances is found to arise from an interplay between lift-up and Orr mechanism. As a result, optimal disturbances are streamwise-modulated streaks with strong thermal components and with a propagation angle inversely proportional to the local Reynolds number. The nonmodal growth is put in perspective with modal growth by means of an -factor comparison. In the nontranscritical regimes, modal stability dominates regardless of a wall-temperature variation. In contrast, in the transcritical regime, nonmodal factors are found to resemble the imposition of an adverse pressure gradient in the ideal-gas regime. When cooling beyond the Widom line, optimal growth is greatly enhanced, yet strong inviscid instability prevails. When heating beyond the Widom line, optimal growth could be sufficiently large to favor transition, particularly with a high free-stream turbulence level.
正如 Ren 等人[J. Fluid Mech. 871, 831 (2019)]所揭示的那样，在接近热力学临界点的区域和伪沸（Widom）线附近，强烈的性质变化会大大改变模态不稳定性的增长。在此，我们在局部平行流假设下，使用线性化纳维-斯托克斯方程的特征向量分解来研究空间框架中的非模态扰动。为了考虑非理想性，我们导出了一种新的能量规范。研究了超临界压力下的几种传热情况，这些情况在技术应用中具有实际意义。通过预设壁面温度和自由流温度，对超临界压力下的流体边界层进行加热或冷却，使温度曲线完全为亚临界（液态）、超临界（气态）或跨临界（跨越维多姆线）。自由流马赫数设定为 10-3。在非跨临界状态下，产生的与流无关的条纹源于抬升效应。壁面冷却增强了亚临界和超临界状态下的能量放大。当温度曲线上升到超过维多姆线时，由于奥尔机制的作用，在很短的流向距离上观察到强烈的次优增长。由于跨临界模式 II 的额外存在，发现大距离的最佳能量增长来自于升力和奥尔机制之间的相互作用。因此，最佳扰动是具有强热成分的流调制条纹，其传播角度与局部雷诺数成反比。通过 N 因子比较，我们将非模态增长与模态增长进行了比较。在非跨临界状态下，无论壁面温度如何变化，模态稳定性都占主导地位。相反，在跨临界状态下，非模态 N 因子与理想气体状态下施加的不利压力梯度相似。当冷却超过维多姆线时，最佳增长会大大增强，但会出现强烈的不粘性不稳定性。当加热超过维多姆线时，最佳增长可能大到有利于过渡，特别是在自由流湍流水平较高的情况下。
{"title":"Transient growth in diabatic boundary layers with fluids at supercritical pressure","authors":"Pietro Carlo Boldini, Benjamin Bugeat, Jurriaan W. R. Peeters, Markus Kloker, Rene Pecnik","doi":"10.1103/physrevfluids.9.083901","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.083901","url":null,"abstract":"In the region close to the thermodynamic critical point and in the proximity of the pseudoboiling (Widom) line, strong property variations substantially alter the growth of modal instabilities, as revealed in Ren <i>et al.</i> [<span>J. Fluid Mech.</span> <b>871</b>, 831 (2019)]. Here, we study nonmodal disturbances in the spatial framework using an eigenvector decomposition of the linearized Navier-Stokes equations under the assumption of locally parallel flow. To account for nonideality, a new energy norm is derived. Several heat transfer scenarios at supercritical pressure are investigated, which are of practical relevance in technical applications. The boundary layers with the fluid at supercritical pressure are heated or cooled by prescribing the wall and free-stream temperatures so that the temperature profile is either entirely subcritical (liquidlike), supercritical (gaslike), or transcritical (across the Widom line). The free-stream Mach number is set to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math>. In the nontranscritical regimes, the resulting streamwise-independent streaks originate from the lift-up effect. Wall cooling enhances the energy amplification for both subcritical and supercritical regimes. When the temperature profile is increased beyond the Widom line, a strong suboptimal growth is observed over very short streamwise distances due to the Orr mechanism. Due to the additional presence of transcritical Mode II, the optimal energy growth at large distances is found to arise from an interplay between lift-up and Orr mechanism. As a result, optimal disturbances are streamwise-modulated streaks with strong thermal components and with a propagation angle inversely proportional to the local Reynolds number. The nonmodal growth is put in perspective with modal growth by means of an <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>N</mi></math>-factor comparison. In the nontranscritical regimes, modal stability dominates regardless of a wall-temperature variation. In contrast, in the transcritical regime, nonmodal <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>N</mi></math> factors are found to resemble the imposition of an adverse pressure gradient in the ideal-gas regime. When cooling beyond the Widom line, optimal growth is greatly enhanced, yet strong inviscid instability prevails. When heating beyond the Widom line, optimal growth could be sufficiently large to favor transition, particularly with a high free-stream turbulence level.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"31 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevfluids.9.083301
Li-Xin Shi (石理新), Song-Chuan Zhao (赵松川)
We investigate the dynamic evolution of heterogeneity in shear-thickening suspensions subjected to swirling excitation with a free surface. The uniform state of such a system may lose its stability when the oscillation frequency is above a threshold, and density waves spontaneously form [Shi et al., J. Fluid Mech.984, A69 (2024)]. Here, we report a state where jammed clusters emerge in high-density regions of the density waves. The jammed cluster exhibits unique motion, creating downstream high-density regions distinct from the previously reported state of density waves. Additionally, theoretical calculations show that reducing suspension thickness lowers the frequency and global concentration threshold for the heterogeneity onset. Notably, the minimal for instability can be lower than the onset of discontinuous shear thickening transition. We also highlight the role of the free surface in cluster growth and persistence.
{"title":"Localized jammed clusters persist in shear-thickening suspension subjected to swirling excitation","authors":"Li-Xin Shi (石理新), Song-Chuan Zhao (赵松川)","doi":"10.1103/physrevfluids.9.083301","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.083301","url":null,"abstract":"We investigate the dynamic evolution of heterogeneity in shear-thickening suspensions subjected to swirling excitation with a free surface. The uniform state of such a system may lose its stability when the oscillation frequency is above a threshold, and density waves spontaneously form [Shi <i>et al.</i>, <span>J. Fluid Mech.</span> <b>984</b>, A69 (2024)]. Here, we report a state where jammed clusters emerge in high-density regions of the density waves. The jammed cluster exhibits unique motion, creating downstream high-density regions distinct from the previously reported state of density waves. Additionally, theoretical calculations show that reducing suspension thickness lowers the frequency and global concentration <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"normal\">Φ</mi></math> threshold for the heterogeneity onset. Notably, the minimal <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"normal\">Φ</mi></math> for instability can be lower than the onset of discontinuous shear thickening transition. We also highlight the role of the free surface in cluster growth and persistence.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"80 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Miscible multiphase flow in porous media is a key phenomenon in various industrial and natural processes, such as hydrogen storage and geological carbon sequestration. However, the parameters controlling the patterns of displacement and mixing in these flows are not completely resolved. This study delves into the effects of heterogeneity and inlet pressure on mixing and displacement patterns of low-viscosity miscible phase invasion into a high-viscosity resident phase, that is saturating a porous medium. The findings highlight the substantial influence of inlet pressures and heterogeneity levels in transitioning from uniform to fingering patterns at the pore scale. These phenomena are detectable at the Darcy scale, and their transition from a uniform front to finger formation is effectively marked through a modified Sherwood number. This modified Sherwood number links microscale patterns to physical properties such as velocity distribution, diffusion, and viscosity contrasts. Additionally, the study employs breakthrough curve (BTC) analysis to illustrate the role of higher heterogeneity and inlet pressure in broadening the fluid velocity distribution, leading to the fingering pattern. These research insights provide a nondimensional approach that scales the BTCs, and can serve future models of miscible phase flow in porous media, linking pore-scale dynamics with macroscale Darcy-scale observations.
{"title":"From mixing to displacement of miscible phases in porous media: The role of heterogeneity and inlet pressures","authors":"Yahel Eliyahu-Yakir, Ludmila Abezgauz, Yaniv Edery","doi":"10.1103/physrevfluids.9.084501","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.084501","url":null,"abstract":"Miscible multiphase flow in porous media is a key phenomenon in various industrial and natural processes, such as hydrogen storage and geological carbon sequestration. However, the parameters controlling the patterns of displacement and mixing in these flows are not completely resolved. This study delves into the effects of heterogeneity and inlet pressure on mixing and displacement patterns of low-viscosity miscible phase invasion into a high-viscosity resident phase, that is saturating a porous medium. The findings highlight the substantial influence of inlet pressures and heterogeneity levels in transitioning from uniform to fingering patterns at the pore scale. These phenomena are detectable at the Darcy scale, and their transition from a uniform front to finger formation is effectively marked through a modified Sherwood number. This modified Sherwood number links microscale patterns to physical properties such as velocity distribution, diffusion, and viscosity contrasts. Additionally, the study employs breakthrough curve (BTC) analysis to illustrate the role of higher heterogeneity and inlet pressure in broadening the fluid velocity distribution, leading to the fingering pattern. These research insights provide a nondimensional approach that scales the BTCs, and can serve future models of miscible phase flow in porous media, linking pore-scale dynamics with macroscale Darcy-scale observations.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"57 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141887219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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