{"title":"FLM volume 980 Cover and Front matter","authors":"","doi":"10.1017/jfm.2024.130","DOIUrl":"https://doi.org/10.1017/jfm.2024.130","url":null,"abstract":"","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139846199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"FLM volume 979 Cover and Front matter","authors":"","doi":"10.1017/jfm.2024.89","DOIUrl":"https://doi.org/10.1017/jfm.2024.89","url":null,"abstract":"","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":"43 1-2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140496167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anil Pasam, D. Tudball Smith, John D. Holmes, David Burton, Mark C. Thompson
{"title":"The influence of surface roughness on postcritical flow over circular cylinders revisited – CORRIGENDUM","authors":"Anil Pasam, D. Tudball Smith, John D. Holmes, David Burton, Mark C. Thompson","doi":"10.1017/jfm.2023.1045","DOIUrl":"https://doi.org/10.1017/jfm.2023.1045","url":null,"abstract":"","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":"14 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139595625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract We revisit the problem of a solid sphere rising slowly in a rotating short container filled with a slightly viscous fluid, with emphasis on the drag force. The data of the classical experiments of Maxworthy (J. Fluid Mech., vol. 31, 1968, pp. 643–655) and recent experiments of Kozlov et al. (Fluids, vol. 8 (2), 2023, paper 49), and the available geostrophic and quasi-geostrophic theories, are subjected to a novel scrutiny by combined reprocessing and comparisons. The measured drag is, consistently, about 20 % lower than the geostrophic prediction (assuming that flow is dominated by the Ekman layers, while in the inviscid cores the Coriolis acceleration is supported by the pressure gradient). The major objective is the interpretation and improvement of the gap between data and predictions. We show that the data cover a small range of relevant parameters (in particular the Taylor number $T$ and the height ratio $H$ of cylinder to particle diameter) that precludes a thorough and reliable assessment of the theories. However, some useful insights and improvements can be derived. The hypothesis that the discrepancy between data and the geostrophic prediction is due to inertial effects (not sufficiently small Rossby number $Ro$ in the experiments) is dismissed. We show that the major reason for the discrepancy is the presence of relatively thick Stewartson layers about the cylinder (Taylor column) attached to the sphere. The $1/3$ layer displaces the boundary condition of the angular velocity ($omega = 0$) outside the radius of the particle. This observation suggests a semi-empirical correction to the theoretical quasi-geostrophic predictions (which takes into account the Ekman layers and the $1/4$ Stewartson layers); the corrected drag is in fair agreement with the data. We demonstrate that the inertial terms are negligible for $Ro,T^{1/2} <0.4$. We consider curve-fit approximations, and point out some persistent gaps of knowledge that require further experiments and simulations.
{"title":"The drag on a rising sphere along the axis in a short rotating cylinder of fluid: revisiting the data and theory","authors":"M. Ungarish","doi":"10.1017/jfm.2023.1093","DOIUrl":"https://doi.org/10.1017/jfm.2023.1093","url":null,"abstract":"Abstract We revisit the problem of a solid sphere rising slowly in a rotating short container filled with a slightly viscous fluid, with emphasis on the drag force. The data of the classical experiments of Maxworthy (J. Fluid Mech., vol. 31, 1968, pp. 643–655) and recent experiments of Kozlov et al. (Fluids, vol. 8 (2), 2023, paper 49), and the available geostrophic and quasi-geostrophic theories, are subjected to a novel scrutiny by combined reprocessing and comparisons. The measured drag is, consistently, about 20 % lower than the geostrophic prediction (assuming that flow is dominated by the Ekman layers, while in the inviscid cores the Coriolis acceleration is supported by the pressure gradient). The major objective is the interpretation and improvement of the gap between data and predictions. We show that the data cover a small range of relevant parameters (in particular the Taylor number $T$ and the height ratio $H$ of cylinder to particle diameter) that precludes a thorough and reliable assessment of the theories. However, some useful insights and improvements can be derived. The hypothesis that the discrepancy between data and the geostrophic prediction is due to inertial effects (not sufficiently small Rossby number $Ro$ in the experiments) is dismissed. We show that the major reason for the discrepancy is the presence of relatively thick Stewartson layers about the cylinder (Taylor column) attached to the sphere. The $1/3$ layer displaces the boundary condition of the angular velocity ($omega = 0$) outside the radius of the particle. This observation suggests a semi-empirical correction to the theoretical quasi-geostrophic predictions (which takes into account the Ekman layers and the $1/4$ Stewartson layers); the corrected drag is in fair agreement with the data. We demonstrate that the inertial terms are negligible for $Ro,T^{1/2} <0.4$. We consider curve-fit approximations, and point out some persistent gaps of knowledge that require further experiments and simulations.","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":"9 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139437956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Three-dimensional simulations of the ordering of elastic capsule suspensions within planar Poiseuille flow channels are reported. The simulations utilize the immersed boundary method coupled with the lattice Boltzmann method to capture the complex flow-induced capsule deformations and hydrodynamic interactions within the suspensions. A parametric study is presented whereby the confinement ratio and the particle deformability are varied independently within a two-dimensional range relevant to this ordering phenomenon. The initial distribution of capsules is random, and the simulations evolve the system from a disordered state to an ordered one, while an order parameter that quantifies the fraction of capsules belonging to one-dimensional train assemblies is computed throughout time. A monotonic increase in ordering is observed with increasing deformability. However, an optimal confinement ratio is identified corresponding to a peak in the order parameter. This peak is attributed to the competition between increasing long-range capsule attractions and decreasing in-plane capsule density (with fixed volume fraction) as the confinement ratio increases. Simulations are also performed to understand how dispersity in capsule size and deformability impact the degree of ordering. It is shown that ordering is quite sensitive to dispersity in capsule size, and much less sensitive to dispersity in deformability. Overall, the results provide important insights for the design of microfluidic devices.
{"title":"Order–disorder transitions within deformable particle suspensions in planar Poiseuille flow","authors":"Paul C. Millett","doi":"10.1017/jfm.2023.1052","DOIUrl":"https://doi.org/10.1017/jfm.2023.1052","url":null,"abstract":"Abstract Three-dimensional simulations of the ordering of elastic capsule suspensions within planar Poiseuille flow channels are reported. The simulations utilize the immersed boundary method coupled with the lattice Boltzmann method to capture the complex flow-induced capsule deformations and hydrodynamic interactions within the suspensions. A parametric study is presented whereby the confinement ratio and the particle deformability are varied independently within a two-dimensional range relevant to this ordering phenomenon. The initial distribution of capsules is random, and the simulations evolve the system from a disordered state to an ordered one, while an order parameter that quantifies the fraction of capsules belonging to one-dimensional train assemblies is computed throughout time. A monotonic increase in ordering is observed with increasing deformability. However, an optimal confinement ratio is identified corresponding to a peak in the order parameter. This peak is attributed to the competition between increasing long-range capsule attractions and decreasing in-plane capsule density (with fixed volume fraction) as the confinement ratio increases. Simulations are also performed to understand how dispersity in capsule size and deformability impact the degree of ordering. It is shown that ordering is quite sensitive to dispersity in capsule size, and much less sensitive to dispersity in deformability. Overall, the results provide important insights for the design of microfluidic devices.","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":"7 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139438016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The reflection of a rightward-moving oblique shock (RMOS) belonging to the first family, over an initially steady oblique shock wave (SOSW) produced by a wedge, is studied in this paper. To cover all possibilities, the problem is divided into a pre-shock reflection problem, for which the incident shock is assumed to reflect over the pre-interaction part of the SOSW, and a post-shock reflection problem, for which the incident shock is assumed to reflect over the post-interaction part. Such division, together with the definition of the equivalent problem defined on the reference frame co-moving with the nominal intersection point of the two shock waves, allows us to connect the reflection patterns with the six types of shock interference of Edney, which include type I–VI shock interferences depending on how an upstream oblique shock intersects a bow shock (types I and II are regular and Mach reflections of two shocks from the opposite sides; type III and type IV have two triple points or two Mach reflection configuration; type V and type VI are irregular and regular reflections of two shocks from the same side). We are thus able to identify all possible shock reflection types and find their transition conditions. Pre-shock reflection may yield IV, V and VI (of Edney's six types) shock interferences and post-shock reflection may yield I, II and III shock interferences. Pre- and post-shock reflections possibly occur at two different parts of the SOSW, and the complete reflection configuration may have one or both of them. Both transition condition study and numerical simulation are used to show how pre-shock reflection and post-shock reflection exist alone or coexist, leading to various types of combined pre-shock and post-shock reflections.
摘要 本文研究了由楔形产生的初始稳定斜冲击波（SOSW）对属于第一族的向右移动斜冲击波（RMOS）的反射问题。为了涵盖所有可能性，本文将问题分为冲击前反射问题和冲击后反射问题，前者假定入射冲击波在 SOSW 的作用前部分上反射，后者假定入射冲击波在作用后部分上反射。这样的划分，加上在与两个冲击波的标称交点同向运动的参照系上定义的等效问题的定义，使我们能够将反射模式与埃德尼的六种冲击波干涉类型联系起来，其中包括 I-VI 型冲击波干涉，这取决于上游斜冲击波与弓冲击波相交的方式（I 型和 II 型是两个冲击波从相反方向的规则和马赫反射；III型和IV型有两个三点或两个马赫反射构型；V型和VI型是来自同一侧的两个冲击波的不规则和规则反射）。因此，我们可以确定所有可能的冲击波反射类型，并找到它们的过渡条件。冲击前反射可能产生 IV、V 和 VI（埃德尼的六种类型）冲击干涉，冲击后反射可能产生 I、II 和 III 型冲击干涉。震前和震后反射可能发生在 SOSW 的两个不同部分，完整的反射结构可能有其中一个或两个。过渡条件研究和数值模拟均用于说明冲击前反射和冲击后反射如何单独存在或共存，从而导致各种类型的冲击前和冲击后组合反射。
{"title":"Reflection of a rightward-moving oblique shock of first family over a steady oblique shock wave","authors":"Miaomiao Wang, ZhongZiheng Xu, Ziniu Wu","doi":"10.1017/jfm.2023.988","DOIUrl":"https://doi.org/10.1017/jfm.2023.988","url":null,"abstract":"Abstract The reflection of a rightward-moving oblique shock (RMOS) belonging to the first family, over an initially steady oblique shock wave (SOSW) produced by a wedge, is studied in this paper. To cover all possibilities, the problem is divided into a pre-shock reflection problem, for which the incident shock is assumed to reflect over the pre-interaction part of the SOSW, and a post-shock reflection problem, for which the incident shock is assumed to reflect over the post-interaction part. Such division, together with the definition of the equivalent problem defined on the reference frame co-moving with the nominal intersection point of the two shock waves, allows us to connect the reflection patterns with the six types of shock interference of Edney, which include type I–VI shock interferences depending on how an upstream oblique shock intersects a bow shock (types I and II are regular and Mach reflections of two shocks from the opposite sides; type III and type IV have two triple points or two Mach reflection configuration; type V and type VI are irregular and regular reflections of two shocks from the same side). We are thus able to identify all possible shock reflection types and find their transition conditions. Pre-shock reflection may yield IV, V and VI (of Edney's six types) shock interferences and post-shock reflection may yield I, II and III shock interferences. Pre- and post-shock reflections possibly occur at two different parts of the SOSW, and the complete reflection configuration may have one or both of them. Both transition condition study and numerical simulation are used to show how pre-shock reflection and post-shock reflection exist alone or coexist, leading to various types of combined pre-shock and post-shock reflections.","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":"1 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139437775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"FLM volume 978 Cover and Front matter","authors":"","doi":"10.1017/jfm.2024.12","DOIUrl":"https://doi.org/10.1017/jfm.2024.12","url":null,"abstract":"","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":"93 18","pages":"f1 - f1"},"PeriodicalIF":0.0,"publicationDate":"2024-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139440150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Getsinger, L. Gevorkyan, T. Shoji, O. Smith, A. Karagozian
After extensive examination and testing, we have determined that erroneous jet flow rates were used in some of the experiments in the above-noted papers (Getsinger et al. 2014; Gevorkyan et al. 2016). This error only pertains to those experiments involving acetone planar laser-induced fluorescence (PLIF) imaging, in which the jet fluid is a mixture of helium, nitrogen and acetone vapour. For these acetone PLIF experiments, the flow rates of helium and nitrogen were prescribed in a manner that erroneously neglected the contribution of acetone vapour to the combined mixture flow rate. Therefore, our actual jet flow rates were higher than those stated in the two papers for such experiments. The identification of instabilities cited (convective instability versus absolute instability in the upstream shear layer, for example) is unchanged in the papers, as are the overall findings on mixing metrics and trends as well as jet structure. The overarching conclusions for the papers are also unchanged. However, many of the parameter values cited in the figures require correction. To correct the research record, we note the following for transverse jet experiments in the papers mentioned above involving acetone PLIF experiments only:
{"title":"Structural and stability characteristics of jets in crossflow – CORRIGENDUM","authors":"D. Getsinger, L. Gevorkyan, T. Shoji, O. Smith, A. Karagozian","doi":"10.1017/jfm.2020.156","DOIUrl":"https://doi.org/10.1017/jfm.2020.156","url":null,"abstract":"After extensive examination and testing, we have determined that erroneous jet flow rates were used in some of the experiments in the above-noted papers (Getsinger et al. 2014; Gevorkyan et al. 2016). This error only pertains to those experiments involving acetone planar laser-induced fluorescence (PLIF) imaging, in which the jet fluid is a mixture of helium, nitrogen and acetone vapour. For these acetone PLIF experiments, the flow rates of helium and nitrogen were prescribed in a manner that erroneously neglected the contribution of acetone vapour to the combined mixture flow rate. Therefore, our actual jet flow rates were higher than those stated in the two papers for such experiments. The identification of instabilities cited (convective instability versus absolute instability in the upstream shear layer, for example) is unchanged in the papers, as are the overall findings on mixing metrics and trends as well as jet structure. The overarching conclusions for the papers are also unchanged. However, many of the parameter values cited in the figures require correction. To correct the research record, we note the following for transverse jet experiments in the papers mentioned above involving acetone PLIF experiments only:","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":" 21","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141221876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The vortex-induced vibration of a spring-mounted, damped, rigid circular cylinder, immersed in a Newtonian viscous flow and capable of moving in the direction orthogonal to the unperturbed flow is investigated for Reynolds numbers $Re$ in the vicinity of the onset of unsteadiness ($15leqslant Releqslant 60$) using the incompressible linearised Navier–Stokes equations. In a first step, we solve the linear problem considering an imposed harmonic motion of the cylinder. Results are interpreted in terms of the mechanical impedance, i.e. the ratio between the vertical force coefficient and the cylinder velocity, which is represented as function of the Reynolds number and the driving frequency. Considering the energy transfer between the cylinder and the fluid, we show that impedance results provide a simple criterion allowing the prediction of the onset of instability of the coupled fluid-elastic structure case. A global stability analysis of the fully coupled fluid/cylinder system is then performed. The instability thresholds obtained by this second approach are found to be in perfect agreement with the predictions of the impedance-based criterion. A theoretical argument, based on asymptotic developments, is then provided to give a prediction of eigenvalues of the coupled problem, as well as to characterise the region of instability beyond the threshold as function of the reduced velocity $U^{ast }$, the dimensionless mass $m^{ast }$ and the Reynolds number. The influence of the damping parameter $unicode[STIX]{x1D6FE}$ on the instability region is also explored.
{"title":"Vortex-induced vibration prediction via an impedance criterion","authors":"D. Sabino, D. Fabre, J. Leontini, D. L. Jacono","doi":"10.1017/jfm.2020.104","DOIUrl":"https://doi.org/10.1017/jfm.2020.104","url":null,"abstract":"The vortex-induced vibration of a spring-mounted, damped, rigid circular cylinder, immersed in a Newtonian viscous flow and capable of moving in the direction orthogonal to the unperturbed flow is investigated for Reynolds numbers $Re$ in the vicinity of the onset of unsteadiness ($15leqslant Releqslant 60$) using the incompressible linearised Navier–Stokes equations. In a first step, we solve the linear problem considering an imposed harmonic motion of the cylinder. Results are interpreted in terms of the mechanical impedance, i.e. the ratio between the vertical force coefficient and the cylinder velocity, which is represented as function of the Reynolds number and the driving frequency. Considering the energy transfer between the cylinder and the fluid, we show that impedance results provide a simple criterion allowing the prediction of the onset of instability of the coupled fluid-elastic structure case. A global stability analysis of the fully coupled fluid/cylinder system is then performed. The instability thresholds obtained by this second approach are found to be in perfect agreement with the predictions of the impedance-based criterion. A theoretical argument, based on asymptotic developments, is then provided to give a prediction of eigenvalues of the coupled problem, as well as to characterise the region of instability beyond the threshold as function of the reduced velocity $U^{ast }$, the dimensionless mass $m^{ast }$ and the Reynolds number. The influence of the damping parameter $unicode[STIX]{x1D6FE}$ on the instability region is also explored.","PeriodicalId":505053,"journal":{"name":"Journal of Fluid Mechanics","volume":"65 1‐2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141225071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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