Physical Review Fluids最新文献

{"title":"Correlations between thermodynamic fluctuations in shock wave/turbulent boundary layer interaction","authors":"Ximeng Hou, Dehao Xu, Jianchun Wang, Shiyi Chen","doi":"10.1103/physrevfluids.9.073401","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.073401","url":null,"abstract":"The second moment correlations between thermodynamic fluctuations in incident shock wave/turbulent boundary layer interaction flows at Mach 2.25 are systematically investigated by direct numerical simulation. The concerned fluctuations are those of pressure, entropy, temperature, and density <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>{</mo><msup><mi>p</mi><mo>′</mo></msup><mo>,</mo><msup><mi>s</mi><mo>′</mo></msup><mo>,</mo><msup><mi>T</mi><mo>′</mo></msup><mo>,</mo><msup><mi>ρ</mi><mo>′</mo></msup><mo>}</mo></mrow></math>. Effects of wall temperature and Reynolds number are studied. Kovásznay decomposition is introduced to decompose the fluctuations into acoustic and entropic modes. It is shown that all the six concerned correlations are determined by merely two parameters, which are interpreted as intermodal competition and intermodal correlation, respectively. Accordingly, the flow field is divided into several zones, each with distinct physical properties, to analyze the contributing factors to the correlations. In addition, a model is proposed where the correlations are deemed as functions of the root-mean-square values of thermodynamic fluctuations, as in Gerolymos and Vallet [<span>J. Fluid Mech.</span> <b>851</b>, 447 (2018)] but simpler. The formula for each correlation has the same form. The accuracy of the model is validated in boundary layers where the intermodal correlation is weak.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"44 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869114","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}

{"title":"Newtonian fluid dynamics in a misaligned parallel-plate rheometer","authors":"Jian Teng, Sungwon La, Jesse T. Ault","doi":"10.1103/physrevfluids.9.074103","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.074103","url":null,"abstract":"A parallel-plate rotational rheometer measures the viscosity of a fluid by rotating the top plate relative to the bottom plate in order to induce a shear on the fluid and measuring the torques and forces that result as a function of the induced rotation rate. Manufacturing imperfections can often lead to unintentional misalignment of the plates of the rheometer, where the top and bottom plates are not perfectly parallel, and this misalignment can affect the fluid dynamics inside the rheometer. This study examines the effect that misalignment has on the viscosity measurements of Newtonian fluids in the limit of small rheometer gap heights. A theoretical model for the behavior of a general Newtonian fluid in a misaligned rheometer with a small gap height is derived using perturbation expansions. The theoretical results show that at small gap heights, misalignment can produce additional secondary velocity components and pressures in the fluid, which affect the forces and moments in the rheometer. In such cases at small Reynolds numbers, the dominant forces and moments acting on the top plate of the rheometer are the viscous force in the direction parallel to the tilt axis, the pressure moment in the direction perpendicular to the tilt axis and in the cross-sectional plane, and the viscous moment in the direction along the height of the rheometer. These forces and moments on the top plate were found to increase as the misalignment tilt angle increased, leading to an increase in the error of viscosity measurement by the rheometer. Three-dimensional numerical simulations validate the theoretical predictions.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"49 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869066","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}

{"title":"How small droplets form in turbulent multiphase flows","authors":"M. Crialesi-Esposito, G. Boffetta, L. Brandt, S. Chibbaro, S. Musacchio","doi":"10.1103/physrevfluids.9.l072301","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.l072301","url":null,"abstract":"The formation of small droplets and bubbles in turbulent flows is a crucial process in geophysics and engineering, whose underlying physical mechanism remains a puzzle. In this Letter, we address this problem by means of high-resolution numerical simulations, comparing a realistic multiphase configuration with a numerical experiment in which we attenuate the presence of strong velocity gradients either across the whole mixture or in the disperse phase only. Our results show unambiguously that the formation of small droplets is governed by the internal dynamics which occurs during the breakup of large drops and that the high vorticity and the extreme dissipation associated to these events are the consequence and not the cause of the breakup.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"46 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869065","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}

{"title":"Modal and nonmodal stability of the laminar flow in a channel with longitudinal riblets","authors":"Antoine Jouin, Jean-Christophe Robinet, Stefania Cherubini","doi":"10.1103/physrevfluids.9.073903","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.073903","url":null,"abstract":"Modal and nonmodal stability analysis of a channel flow with longitudinal riblets are investigated. To this extent, a method based on the coupling between a two-dimensional stability problem and a computational framework for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>n</mi></math>-periodic systems based on Bloch waves is proposed. Unstable modes from linear stability can be retrieved. The influence of the riblets on the most amplified flow structures is investigated through a transient growth analysis: a resonance is found when the riblet wavenumber is equal to the wavenumber of the optimal streaks in a smooth channel flow. For large riblet spacing, a wavenumber lock-in regime, in which the streaks dynamics and wavelength are totally controlled by the riblet spacing, is observed. Physically, a modulation of the streaks amplitude in the spanwise direction via a beating mechanism is seen. These phenomena are characteristic of dynamic systems spatially forced and may exhibit geometric frustration. Similar results were found in the study of secondary flows in Rayleigh-Bénard convection with wavy walls. A resolvent analysis is also performed: it is found that riblets lead to the development of oblique waves that may trigger an early transition.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"160 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869064","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}

{"title":"Dissociation of red blood cell aggregates in extensional flow","authors":"Midhun Puthumana Melepattu, Guillaume Maîtrejean, Thomas Podgorski","doi":"10.1103/physrevfluids.9.l071101","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.l071101","url":null,"abstract":"Blood rheology and microcirculation are strongly influenced by red blood cell aggregation. We investigate the dissociation rates of red cell aggregates in extensional flow using hyperbolic microfluidic constrictions and image analysis by a convolutional neural network (CNN). Our findings reveal that aggregate dissociation increases sharply when a critical extension rate is reached which falls within the range of microcirculatory conditions, suggesting that large variations of aggregate sizes should be expected <i>in vivo</i>. This work contributes to a deeper understanding of the behavior of red blood cell aggregates in response to extensional stress in microcirculatory networks, provides crucial experimental data to validate theoretical and numerical models, and constitutes the basis for improved evaluation of blood aggregability in clinical contexts.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"13 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869063","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}

{"title":"Ion steric interactions and electrostatic correlations on electro-osmotic flow in charged nanopores with multivalent electrolytes","authors":"Shubhra Sahu, Bapan Mondal, Somnath Bhattacharyya","doi":"10.1103/physrevfluids.9.074201","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.074201","url":null,"abstract":"Atomistic and coarse-grained simulations show the formation of a condensed layer of counterions near a charged surface in contact with multivalent or monovalent electrolytes of high concentration. This condensed layer may overscreen the surface charge, and eventually a coion-dominated region may arise within the electric double layer, which again draws a layer of counterions and so on till the charge density approaches zero. Such a type of overscreening and charge density oscillation cannot be predicted through the mean-field based models as it does not account for the correlations between discrete charges. In the present study the mean-field-based model has been extended to consider the many-body interactions to analyze the electro-osmosis and ion transport of multivalent electrolytes in a highly charged nanopore. The ions are considered to be finite-sized, which is accounted for by considering the hydrodynamic steric interactions and modification of the suspension medium viscosity. Consideration of the electrostatic correlation leads to a fourth-order Poisson-Fermi equation for an electric field. Such a type of continuum model is easy to handle and to use to predict the layered structure of the EDL. Our model captures the existing experimental and molecular dynamics simulation correctly. Based on the modified model, we have analyzed the volume flow rate, current density, and ion selectivity of the pore in multivalent electrolytes for different electrostatic conditions. The present model shows that the counterion size has an impact on the condensed layer and hence overscreening. We demonstrate that the EOF reversal of multivalent electrolytes can be suppressed by mixing with monovalent slats.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"44 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141775933","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}

{"title":"Investigating the effect of turbulence on hemolysis through cell-resolved fluid-structure interaction simulations of individual red blood cells","authors":"Grant Rydquist, Mahdi Esmaily","doi":"10.1103/physrevfluids.9.073102","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.073102","url":null,"abstract":"Existing hemolysis algorithms are often constructed for laminar flows that expose red blood cells (RBCs) to a constant rate of shear. It remains an open question whether such models are applicable to turbulent flows, where there is a significant variation in shear rate along cell trajectories. To evaluate the effect of turbulence on hemolysis, we perform cell-resolved simulations of isolated RBCs in turbulent channel flow at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mtext>Re</mtext><mi>τ</mi></msub><mo>=</mo><mn>180</mn></mrow></math> and 360 and compare them against the results obtained from laminar flow simulations at an equivalent wall shear stress. The RBCs are modeled as isolated cells in an unbounded domain with the viscosity of the bulk fluid used for the surrounding fluid. This comparison shows that, while the laminar flow generally induces greater stretch in the cell in a time-averaged sense, cells experience an overall larger deformation in turbulence. This difference is attributed to extreme events in turbulence that occasionally create bursts of high shear conditions, which, consequently, induce a large deformation in the cells. Associating damage with the most extreme deformation regimes, we observe that, in the worst case, the turbulent flow can produce deformation in the cell that is higher than the absolute maximum value in the analogous laminar case approximately <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>14</mn><mo>%</mo></mrow></math> of the time. Additionally, the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Re</mi><mi>τ</mi></msub><mo>=</mo><mn>180</mn></mrow></math> universally induced greater deformation in the cells than the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Re</mi><mi>τ</mi></msub><mo>=</mo><mn>360</mn></mrow></math> case, suggesting that increasing the range of scales in the flow does not necessarily yield greater deformation when all other parameters are kept constant. A strong direct correlation (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>R</mi><mo>&gt;</mo><mn>0.8</mn></mrow></math>) between shear rate and deformation metrics was observed in turbulence. The correlation against <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Q</mi></math>-criterion is inverse and weaker (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>R</mi><mo>≈</mo><mo>−</mo><mn>0.26</mn></mrow></math>), but once the shear contribution is subtracted, it improves in terms of areal dilatation (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>R</mi><mo>≈</mo><mo>−</mo><mn>0.6</mn></mrow></math>).","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"9 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785246","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}

{"title":"Evolution of turbulence using a random jet array","authors":"Arefe Ghazi Nezami, Blair Anne Johnson","doi":"10.1103/physrevfluids.9.074610","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.074610","url":null,"abstract":"Random jet arrays (RJAs) have been shown to be effective in generating zero mean flow homogeneous isotropic turbulence. While many laboratory studies have investigated the flow in these facilities, there are several remaining questions regarding the evolution of turbulence, from the development of turbulence to where it decays, along with understanding how input energy from the jet array transfers into different turbulent flow characteristics. To address these questions, we perform a series of laboratory experiments in which we alter the parameters of the randomized algorithm, along with the jet spacing and outlet velocity of the jets. We first determine the location where turbulence transitions to a fully developed state and show that it is a function of jet penetration length, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi mathvariant=\"script\">L</mi><mi mathvariant=\"script\">J</mi></msub></math>, and effective jet spacing, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>S</mi><mi>e</mi></msub></math>. We identify three distinct regions for the spatial decay of turbulence in RJA facilities and notably, we find different decay rates, unlike previous studies that report only one spatial decay rate using similar facilities. These regions are shown to depend on the variations of input parameters yet independent of the strength of the mean flow. We also find the strength of the mean flow does not affect the homogeneity, nor the production, transport, or advection terms of the turbulent kinetic energy budget equation. Finally, we address a longstanding question toward estimating turbulence metrics with an RJA based on the input parameters. We define an efficiency parameter that provides insight into the transfer rate of input power to the dissipation rate of the generated turbulence.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"31 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785441","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}

{"title":"Dynamics of a magnetic particle in an oscillating magnetic field","authors":"I. Misra, V. Kumaran","doi":"10.1103/physrevfluids.9.074303","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.074303","url":null,"abstract":"The orientation dynamics of and the torque fluctuations due to a spheroidal magnetic particle in an oscillating magnetic field are analyzed in the Stokes flow regime. For a permanent dipole, the dynamics depends on <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mi>ω</mi><mo>†</mo></msup></math>, the ratio of the magnetic field frequency, and the viscous relaxation rate. For <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mi>ω</mi><mo>†</mo></msup><mo>≫</mo><mn>1</mn></mrow></math>, the particle executes oscillations with amplitude <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>∼</mo><msup><mrow><mo>(</mo><msup><mi>ω</mi><mo>†</mo></msup><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> about its initial orientation. The average torque is zero because the particle does not execute complete rotations, and the root mean square of the torque fluctuations scaled by the characteristic magnetic torque tends to a constant in this limit. For <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mi>ω</mi><mo>†</mo></msup><mo>≪</mo><mn>1</mn></mrow></math>, the orientation is close to the magnetic field direction for most of the oscillation period, and it rapidly rotates when the field passes through extrema. The scaled root mean square of the torque fluctuations is proportional to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mo>(</mo><msup><mi>ω</mi><mo>†</mo></msup><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></math> in this limit. The particle orientation aligns along the magnetic field direction for different models of induced dipoles if the magnetization is nonhysteretic. For the hysteretic Stoner-Wohlfarth model, the dynamics also depends on the parameter <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>h</mi><mn>0</mn></msub></math>, the ratio of the Zeeman energy, and the anisotropy energy. For <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>h</mi><mn>0</mn></msub><mo>≪</mo><mn>1</mn></mrow></math>, the magnetic moment oscillates about one pole of the orientation vector, and the orientation vector rapidly rotates when the field passes through extrema in a manner similar to that for a permanent dipole. For <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>h</mi><mn>0</mn></msub><mo>≫</mo><mn>1</mn></mrow></math>, the magnetic moment switches between the two poles of the orientation vector, and the orientation vector executes small amplitude oscillations about the field direction. There is a discontinuous transition between the oscillating and switching magnetic moment which depends on <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>h</mi><mn>0</mn></msub></math> and the initial orientation.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"44 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141775932","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}

{"title":"Shape reconfiguration for underwater propeller efficiency improvement","authors":"Tristan Aurégan, Sylvain Courrech du Pont, Benjamin Thiria","doi":"10.1103/physrevfluids.9.074402","DOIUrl":"https://doi.org/10.1103/physrevfluids.9.074402","url":null,"abstract":"We investigate experimentally the propulsive efficiency of a propeller in water with chordwise flexible blades that deform under the action of fluid loading. Using a scale model experiment, we record the deformation of the blades as well as the thrust and torque generated by the rotor. The use of flexible materials can improve the resilience to changing external conditions: with optimal flexibility, the blades deform and remain efficient under off-design conditions. We derive a theoretical law for blade tip deformation and show good agreement with experiments. Our results suggest that, using only the blade flexibility alone, we are able to program the blade deformation to passively adopt an optimized shape for efficient propulsion within a given parameter range.","PeriodicalId":20160,"journal":{"name":"Physical Review Fluids","volume":"51 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141775935","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}