Pub Date : 2022-12-06DOI: 10.1088/1873-7005/aca931
A. A. Hosseinjani, G. Akbari
Large-scale eddies in a lid-driven cavity are potential sources of angular momentum which can induce rotational effect in a free-to-rotate inertial body due to fluid–structure interaction. The novel objective of the present study is to investigate vortex-induced autorotation of an elliptic blade hinged at the centre of a lid-driven cavity. The governing equations are numerically solved using iterative direct forcing immersed boundary method. The impact of Reynolds number and blade length on dynamics characteristics of the blade are analysed. Considering left to right motion of horizontal top lid, four different vortex-induced modes are identified as the steady blade response, including stationary position, small-amplitude fluttering, clockwise autorotation and counter-clockwise autorotation. Long blades are mostly potential for steady clockwise autorotation, particularly in higher Reynolds numbers, due to dominance of principal near-wall cavity vortex compared to other vortices. In contrast, effective role of central counter-clockwise vortex in a short blade and weak interaction of such blade with the near-wall cavity vortex leads to a steady counter-clockwise rotation, particularly in high Reynolds numbers. In the case of low Reynolds numbers or blade with moderate length, vortex-induced blade motions in clockwise and counter-clockwise directions are fairly balanced, leading to stationary position or small-amplitude fluttering modes.
{"title":"Numerical study of vortex-induced autorotation of an elliptic blade in lid-driven cavity flow","authors":"A. A. Hosseinjani, G. Akbari","doi":"10.1088/1873-7005/aca931","DOIUrl":"https://doi.org/10.1088/1873-7005/aca931","url":null,"abstract":"Large-scale eddies in a lid-driven cavity are potential sources of angular momentum which can induce rotational effect in a free-to-rotate inertial body due to fluid–structure interaction. The novel objective of the present study is to investigate vortex-induced autorotation of an elliptic blade hinged at the centre of a lid-driven cavity. The governing equations are numerically solved using iterative direct forcing immersed boundary method. The impact of Reynolds number and blade length on dynamics characteristics of the blade are analysed. Considering left to right motion of horizontal top lid, four different vortex-induced modes are identified as the steady blade response, including stationary position, small-amplitude fluttering, clockwise autorotation and counter-clockwise autorotation. Long blades are mostly potential for steady clockwise autorotation, particularly in higher Reynolds numbers, due to dominance of principal near-wall cavity vortex compared to other vortices. In contrast, effective role of central counter-clockwise vortex in a short blade and weak interaction of such blade with the near-wall cavity vortex leads to a steady counter-clockwise rotation, particularly in high Reynolds numbers. In the case of low Reynolds numbers or blade with moderate length, vortex-induced blade motions in clockwise and counter-clockwise directions are fairly balanced, leading to stationary position or small-amplitude fluttering modes.","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46745028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-11-16DOI: 10.1088/1873-7005/aca357
J. R. Martins, J. V. Barbosa, F. Santos, L. F. L. R. Silva
Flammable gases leaks at high pressures are hazardous, especially the free underexpanded jets. Therefore, understanding their behavior is fundamental to guarantee a safe environment. Due to the difficulty to obtain experimental data from free under expanded jets, related to the great speeds and gradients, computational fluid dynamics (CFD) has become an essential tool. Simulations for free underexpanded jets to identify algorithms that better represent this problem were performed in this work. The analysis involved different algorithms for fluid flow solution and a local time stepping approach using both OpenFOAM and ANSYS Fluent CFD packages. Our study concluded that all algorithms and software studied had a satisfactory result compared to experimental data. However, we observed that Fluent had a considerable advantage because the simulation was faster compared with other solvers in OpenFOAM, for instance.
{"title":"Computational analysis in underexpanded jets simulations","authors":"J. R. Martins, J. V. Barbosa, F. Santos, L. F. L. R. Silva","doi":"10.1088/1873-7005/aca357","DOIUrl":"https://doi.org/10.1088/1873-7005/aca357","url":null,"abstract":"Flammable gases leaks at high pressures are hazardous, especially the free underexpanded jets. Therefore, understanding their behavior is fundamental to guarantee a safe environment. Due to the difficulty to obtain experimental data from free under expanded jets, related to the great speeds and gradients, computational fluid dynamics (CFD) has become an essential tool. Simulations for free underexpanded jets to identify algorithms that better represent this problem were performed in this work. The analysis involved different algorithms for fluid flow solution and a local time stepping approach using both OpenFOAM and ANSYS Fluent CFD packages. Our study concluded that all algorithms and software studied had a satisfactory result compared to experimental data. However, we observed that Fluent had a considerable advantage because the simulation was faster compared with other solvers in OpenFOAM, for instance.","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44325352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-10-26DOI: 10.1088/1873-7005/ac9dbc
Yuxing Peng, Qiang Liu, Zhong Li, Jian Wu
Three-dimensional electro-thermo-hydrodynamic (ETHD) flows of dielectric fluids driven by simultaneous Coulomb and buoyancy forces in a cubic box is numerically studied. The set of coupled equations associated with the ETHD phenomena are solved with the finite volume method. The code is first validated by comparing the numerically obtained linear critical values of the pure electro-convection and thermal convection with the previous studies. Then the neutral stability curve of the system is given and the finite amplitude instability thresholds with different Rayleigh numbers ( Ra ) are presented. It is found that along the neutral stability curve, the flow strength becomes weaker with the increase of Ra and the decrease of electric Rayleigh number (T). Besides, the gap between the linear and nonlinear critical values expressed in terms of T decreases with the increase of Ra . Primarily, the distributions of charge density, temperature and velocity fields with different governing parameters near neutral stability curve are presented. The temperature and charge density profiles near the linear and nonlinear critical values are given, showing that higher T results in wider charge void region and shorter distance between the charge void region’s lower boundary and injection electrode. Finally, the symmetries of the flow patterns along the neutral stability curve are also discussed briefly.
{"title":"Finite amplitude electro-thermo convection in a cubic box","authors":"Yuxing Peng, Qiang Liu, Zhong Li, Jian Wu","doi":"10.1088/1873-7005/ac9dbc","DOIUrl":"https://doi.org/10.1088/1873-7005/ac9dbc","url":null,"abstract":"Three-dimensional electro-thermo-hydrodynamic (ETHD) flows of dielectric fluids driven by simultaneous Coulomb and buoyancy forces in a cubic box is numerically studied. The set of coupled equations associated with the ETHD phenomena are solved with the finite volume method. The code is first validated by comparing the numerically obtained linear critical values of the pure electro-convection and thermal convection with the previous studies. Then the neutral stability curve of the system is given and the finite amplitude instability thresholds with different Rayleigh numbers ( Ra ) are presented. It is found that along the neutral stability curve, the flow strength becomes weaker with the increase of Ra and the decrease of electric Rayleigh number (T). Besides, the gap between the linear and nonlinear critical values expressed in terms of T decreases with the increase of Ra . Primarily, the distributions of charge density, temperature and velocity fields with different governing parameters near neutral stability curve are presented. The temperature and charge density profiles near the linear and nonlinear critical values are given, showing that higher T results in wider charge void region and shorter distance between the charge void region’s lower boundary and injection electrode. Finally, the symmetries of the flow patterns along the neutral stability curve are also discussed briefly.","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48966823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-10-19DOI: 10.1088/1873-7005/ac9b8c
Haibo Wang, Hailong Yu, Yunlan Sun, Rajnish N. Sharma
A two-dimensional numerical study is conducted to investigate the influence of the reduced velocity on two-degree-of-freedom vortex induced vibrations of a circular cylinder controlled by synthetic jets ejected in horizontal and vertical directions (β = 0° and β = 90°). The Reynolds number is constant at Re = 150, and the reduced velocity varies in the range of 2.5 and 15 (U* = 2.5–15). The mass ratio of the circular cylinder is 2.0, and the in-flow to the cross-flow natural frequency ratio equals 1.0 (f nx /f ny = 1.0). The oscillation characters, hydrodynamic forces and vortex shedding of circular cylinders with or without synthetic jets control are analyzed and compared. The results indicate that synthetic jets ejected in vertical direction (β = 90°) can intensify both in-flow and cross-flow oscillations of the circular cylinder in the whole reduced velocity range, the vortex shedding of the controlled case (β = 90°) becomes complicated even unstable with the reduced velocity increasing. Synthetic jets ejected in horizontal direction (β = 0°) have excellent performance on suppressing the cross-flow oscillation of the circular cylinder in the whole reduced velocity range. When U* ⩾ 8.0, the in-flow oscillation of the circular cylinder can even be intensified by synthetic jets ejected in horizontal direction (β = 0°).
{"title":"The influence of reduced velocity on the control of two-degree-of-freedom vortex induced vibrations of a circular cylinder via synthetic jets","authors":"Haibo Wang, Hailong Yu, Yunlan Sun, Rajnish N. Sharma","doi":"10.1088/1873-7005/ac9b8c","DOIUrl":"https://doi.org/10.1088/1873-7005/ac9b8c","url":null,"abstract":"A two-dimensional numerical study is conducted to investigate the influence of the reduced velocity on two-degree-of-freedom vortex induced vibrations of a circular cylinder controlled by synthetic jets ejected in horizontal and vertical directions (β = 0° and β = 90°). The Reynolds number is constant at Re = 150, and the reduced velocity varies in the range of 2.5 and 15 (U* = 2.5–15). The mass ratio of the circular cylinder is 2.0, and the in-flow to the cross-flow natural frequency ratio equals 1.0 (f nx /f ny = 1.0). The oscillation characters, hydrodynamic forces and vortex shedding of circular cylinders with or without synthetic jets control are analyzed and compared. The results indicate that synthetic jets ejected in vertical direction (β = 90°) can intensify both in-flow and cross-flow oscillations of the circular cylinder in the whole reduced velocity range, the vortex shedding of the controlled case (β = 90°) becomes complicated even unstable with the reduced velocity increasing. Synthetic jets ejected in horizontal direction (β = 0°) have excellent performance on suppressing the cross-flow oscillation of the circular cylinder in the whole reduced velocity range. When U* ⩾ 8.0, the in-flow oscillation of the circular cylinder can even be intensified by synthetic jets ejected in horizontal direction (β = 0°).","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46518120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-10-03DOI: 10.1088/1873-7005/ac9713
K. Ryono, K. Ishioka
New numerical methods are proposed for the mixing entropy maximization problem in the context of Miller–Robert–Sommeria’s (MRS) statistical mechanics theory of two-dimensional turbulence, particularly in the case of spherical geometry. Two of the methods are for the canonical problem; the other is for the microcanonical problem. The methods are based on the original MRS theory and thus take into account all Casimir invariants. Compared to the methods proposed in previous studies, our new methods make it easier to detect multiple statistical equilibria and to search for solutions with broken zonal symmetry. The methods are applied to a zonally symmetric initial vorticity distribution which is barotropically unstable. Two statistical equilibria are obtained, one of which has a wave-like structure with zonal wavenumber 1, and the other has a wave-like structure with zonal wavenumber 2. While the former is the maximum point of the mixing entropy, the wavenumber 2 structure of the latter is nearly the same as the structure that appears in the end state of the time integration of the vorticity equation. The new methods allow for efficient computation of statistical equilibria for initial vorticity distributions consisting of many levels of vorticity patches without losing information about all the conserved quantities. This means that the statistical equilibria can be obtained from an arbitrary initial vorticity distribution, which allows for the application of statistical mechanics to interpret a wide variety of flow patterns appearing in geophysical fluids.
{"title":"New numerical methods for calculating statistical equilibria of two-dimensional turbulent flows, strictly based on the Miller–Robert–Sommeria theory","authors":"K. Ryono, K. Ishioka","doi":"10.1088/1873-7005/ac9713","DOIUrl":"https://doi.org/10.1088/1873-7005/ac9713","url":null,"abstract":"New numerical methods are proposed for the mixing entropy maximization problem in the context of Miller–Robert–Sommeria’s (MRS) statistical mechanics theory of two-dimensional turbulence, particularly in the case of spherical geometry. Two of the methods are for the canonical problem; the other is for the microcanonical problem. The methods are based on the original MRS theory and thus take into account all Casimir invariants. Compared to the methods proposed in previous studies, our new methods make it easier to detect multiple statistical equilibria and to search for solutions with broken zonal symmetry. The methods are applied to a zonally symmetric initial vorticity distribution which is barotropically unstable. Two statistical equilibria are obtained, one of which has a wave-like structure with zonal wavenumber 1, and the other has a wave-like structure with zonal wavenumber 2. While the former is the maximum point of the mixing entropy, the wavenumber 2 structure of the latter is nearly the same as the structure that appears in the end state of the time integration of the vorticity equation. The new methods allow for efficient computation of statistical equilibria for initial vorticity distributions consisting of many levels of vorticity patches without losing information about all the conserved quantities. This means that the statistical equilibria can be obtained from an arbitrary initial vorticity distribution, which allows for the application of statistical mechanics to interpret a wide variety of flow patterns appearing in geophysical fluids.","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49170164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-10-01DOI: 10.1088/1873-7005/ac9159
Manoochehr Barimani, Mehran Khaki Jamei, M. Abbasi
The numerical modeling of an electroosmosis flow in a rectangular three-dimensional rotating microchannel has been studied. The study’s goal is to calculate the flow’s development length, and as a novelty, a correlation is proposed to estimate the development length. The flow was simulated for angular velocity (ω) ranges of 0–9 and electric potential (φ) ranges of 0.1–0.3. The results were imported into the curve fitting toolbox to determine a correlation for the development length. The correlation was obtained as a function of angular velocity, electric potential, and hydraulic diameter. The results show that increasing both ω and φ leads to an increase in flow development length, where for constant φ, increasing ω from 0 to 9 results in a 20%–30% increase in development length. Furthermore, increasing φ from 0.1 to 0.3 for a constant ω raises development length by 35%–50%. The velocity field and its parameters, such as ω and φ, were analyzed and discussed.
{"title":"Calculation of electro-osmotic flow development length in a rotating three-dimensional microchannel","authors":"Manoochehr Barimani, Mehran Khaki Jamei, M. Abbasi","doi":"10.1088/1873-7005/ac9159","DOIUrl":"https://doi.org/10.1088/1873-7005/ac9159","url":null,"abstract":"The numerical modeling of an electroosmosis flow in a rectangular three-dimensional rotating microchannel has been studied. The study’s goal is to calculate the flow’s development length, and as a novelty, a correlation is proposed to estimate the development length. The flow was simulated for angular velocity (ω) ranges of 0–9 and electric potential (φ) ranges of 0.1–0.3. The results were imported into the curve fitting toolbox to determine a correlation for the development length. The correlation was obtained as a function of angular velocity, electric potential, and hydraulic diameter. The results show that increasing both ω and φ leads to an increase in flow development length, where for constant φ, increasing ω from 0 to 9 results in a 20%–30% increase in development length. Furthermore, increasing φ from 0.1 to 0.3 for a constant ω raises development length by 35%–50%. The velocity field and its parameters, such as ω and φ, were analyzed and discussed.","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42349667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-09-29DOI: 10.1088/1873-7005/ac963d
M. Kurgansky
The inertial parametric instability of a time-dependent spatially periodic flow (Kolmogorov flow) of a rotating stratified Boussinesq fluid is studied, taking fully into account the Coriolis force in the problem and with the possibility that the flow has an arbitrary orientation in the horizontal plane. The existence of instability is shown for velocity shears less than those indicated by the criterion of inertial stability of a steady flow with the same spatial period and velocity amplitude. In particular, the instability estimates are obtained for weakly stratified geophysical media, for example for the deep layers of the ocean, and it is suggested that the possible applications of the theory can also be directly related to a laboratory experiment. Two different theoretical scenarios of inclusion of the full Coriolis force account in the problem are considered, and in both cases this leads to a reduction in the degree of inertial instability of the basic flow.
{"title":"Inertial instability of the time-periodic Kolmogorov flow in a rotating fluid with the full account of the Coriolis force","authors":"M. Kurgansky","doi":"10.1088/1873-7005/ac963d","DOIUrl":"https://doi.org/10.1088/1873-7005/ac963d","url":null,"abstract":"The inertial parametric instability of a time-dependent spatially periodic flow (Kolmogorov flow) of a rotating stratified Boussinesq fluid is studied, taking fully into account the Coriolis force in the problem and with the possibility that the flow has an arbitrary orientation in the horizontal plane. The existence of instability is shown for velocity shears less than those indicated by the criterion of inertial stability of a steady flow with the same spatial period and velocity amplitude. In particular, the instability estimates are obtained for weakly stratified geophysical media, for example for the deep layers of the ocean, and it is suggested that the possible applications of the theory can also be directly related to a laboratory experiment. Two different theoretical scenarios of inclusion of the full Coriolis force account in the problem are considered, and in both cases this leads to a reduction in the degree of inertial instability of the basic flow.","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48572086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-09-16DOI: 10.1088/1873-7005/ac8a14
Y. Fukumoto
Theoretical treatment of the motion of a slender vortex tube, in most cases, assumes that the cross-section of the vortical core is uniform along the tube (in the z direction), though variation in the vortex core cross-section is crucial for the vortex breakdown phenomena. In the late 20th century, two heuristic theories were proposed for the problem of axisymmetric area waves on the core of a vortex tube embedded in an incompressible inviscid fluid. Lundgren and Ashurst (1989) derived a model equation, being referred to as ‘momentum wave model’, for the axial velocity W (z, t) by taking the spatial average of the z component of the Euler equation for axial flow, assuming that the axial flow is uniform over the cross-section of the core (‘slug flow’). Leonard (1994) derived an evolution equation (‘vorticity wave model’) for the ratio of W (z, t) to the cross section A(z, t) from the spatial average of the azimuthal component of the vorticity equation. Although these two partial differential equations look alike, there is a decisive difference in the dispersion relation, namely in the travelling speed of the core-area waves. For the momentum wave model, the area wave propagates at the same speed upstream and downstream in a coordinate system that moves with the axial flow, while for the vorticity wave model, it propagates asymmetrically, faster downstream than upstream. This paper systematically derives a system of evolution equations for axisymmetric deformation of the vortex core using differential geometric techniques, and supports for the vortex wave model with respect to the dispersion relation. Moreover, this approach makes it possible to calculate the time evolution of the cross-section subject to general irrotational external straining flows, whereby an insight is gained into the Leray scaling for the stretching of vortex tubes in a turbulent flow. The theoretical tool is the hybrid Euler–Lagrange approach, which has been devised to describe generalized Lagrangian mean theory, and the authors themselves developed a differential geometric method. The basic flow, with time dependence being admitted, is treated in the Lagrangian way, and the disturbance is treated in the Eulerian way. Two coordinate systems, the physical system (x̃) and the reference system (x), are introduced. In the reference system, the vortex tube is taken to be of circular cylindrical shape, with allowance being made for axial vorticity and axial flow in the core. A time-dependent mapping x̃ = φ (x, t) from the reference system to the physical system represents the axisymmetric nonlinear deformation of the vortex tube, whose velocity field Ũ= ∂tφ ◦φ−1 has radial and axial components only. This part is treated in the Lagrangian way and the axisymmetric Euler equations are written down in the non-orthogonal coordinate system moving with the velocity Ũ. Supposing a uniform vorticity distribution for the basic field and taking the ‘slender limit’ of the vortex region in the
{"title":"The 15th FDR prize","authors":"Y. Fukumoto","doi":"10.1088/1873-7005/ac8a14","DOIUrl":"https://doi.org/10.1088/1873-7005/ac8a14","url":null,"abstract":"Theoretical treatment of the motion of a slender vortex tube, in most cases, assumes that the cross-section of the vortical core is uniform along the tube (in the z direction), though variation in the vortex core cross-section is crucial for the vortex breakdown phenomena. In the late 20th century, two heuristic theories were proposed for the problem of axisymmetric area waves on the core of a vortex tube embedded in an incompressible inviscid fluid. Lundgren and Ashurst (1989) derived a model equation, being referred to as ‘momentum wave model’, for the axial velocity W (z, t) by taking the spatial average of the z component of the Euler equation for axial flow, assuming that the axial flow is uniform over the cross-section of the core (‘slug flow’). Leonard (1994) derived an evolution equation (‘vorticity wave model’) for the ratio of W (z, t) to the cross section A(z, t) from the spatial average of the azimuthal component of the vorticity equation. Although these two partial differential equations look alike, there is a decisive difference in the dispersion relation, namely in the travelling speed of the core-area waves. For the momentum wave model, the area wave propagates at the same speed upstream and downstream in a coordinate system that moves with the axial flow, while for the vorticity wave model, it propagates asymmetrically, faster downstream than upstream. This paper systematically derives a system of evolution equations for axisymmetric deformation of the vortex core using differential geometric techniques, and supports for the vortex wave model with respect to the dispersion relation. Moreover, this approach makes it possible to calculate the time evolution of the cross-section subject to general irrotational external straining flows, whereby an insight is gained into the Leray scaling for the stretching of vortex tubes in a turbulent flow. The theoretical tool is the hybrid Euler–Lagrange approach, which has been devised to describe generalized Lagrangian mean theory, and the authors themselves developed a differential geometric method. The basic flow, with time dependence being admitted, is treated in the Lagrangian way, and the disturbance is treated in the Eulerian way. Two coordinate systems, the physical system (x̃) and the reference system (x), are introduced. In the reference system, the vortex tube is taken to be of circular cylindrical shape, with allowance being made for axial vorticity and axial flow in the core. A time-dependent mapping x̃ = φ (x, t) from the reference system to the physical system represents the axisymmetric nonlinear deformation of the vortex tube, whose velocity field Ũ= ∂tφ ◦φ−1 has radial and axial components only. This part is treated in the Lagrangian way and the axisymmetric Euler equations are written down in the non-orthogonal coordinate system moving with the velocity Ũ. Supposing a uniform vorticity distribution for the basic field and taking the ‘slender limit’ of the vortex region in the ","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45853521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-09-05DOI: 10.1088/1873-7005/ac7ee1
Hannah Katherine Chapman, H. Sung
Yasuhide Fukumoto, Kyushu University, Japan Martin Oberlack, Technische Universität Darmstadt, Germany Shu Takagi, The University of Tokyo, Japan Minami Yoda, Georgia Institute of Technology, USA Graham Hughes, Imperial College London, United Kingdom Genta Kawahara, Osaka University, Japan Stefan Llewellyn Smith, University of California, USA Laurent B Mydlarski, McGill University, Canada Koji Nagata, Nagoya University, Japan Benôıt Pier, CNRS-Université de Lyon, France Hyung Jin Sung, Korea Advanced Institute of Science and Technology, South Korea Kazuyoshi Suga, Osaka Metropolitan University, Japan Makoto Iima, Hiroshima University, Japan Yuka Iga, Tohoku University, Japan Keiichi Ishioka, Kyoto University, Japan Masahide Inagaki, Toyota Central R&D Labs., Inc., Japan Kaoru Iwamoto, Tokyo University of Agriculture and Technology, Japan Marie Oshima, The University of Tokyo, Japan Masako Sugihara-Seki, Kansai University, Japan Mamoru Tanahashi, Tokyo Institute of Technology, Japan Yoshiyuki Tsuji, Nagoya University, Japan Hiroki Nagai, Tohoku University, Japan Yasuo Nihei, Tokyo University of Science, Japan Koji Fukagata, Keio University, Japan Mizue Munakata, Kumamoto University, Japan Shinsuke Mochizuki, Okayama University, Japan Toshiyuki Gotoh, Nagoya Institute Technology, Japan Kenji Yoshida, Japan Aerospace Exploration Agency, Japan
{"title":"Message regarding the Russian military action in Ukraine","authors":"Hannah Katherine Chapman, H. Sung","doi":"10.1088/1873-7005/ac7ee1","DOIUrl":"https://doi.org/10.1088/1873-7005/ac7ee1","url":null,"abstract":"Yasuhide Fukumoto, Kyushu University, Japan Martin Oberlack, Technische Universität Darmstadt, Germany Shu Takagi, The University of Tokyo, Japan Minami Yoda, Georgia Institute of Technology, USA Graham Hughes, Imperial College London, United Kingdom Genta Kawahara, Osaka University, Japan Stefan Llewellyn Smith, University of California, USA Laurent B Mydlarski, McGill University, Canada Koji Nagata, Nagoya University, Japan Benôıt Pier, CNRS-Université de Lyon, France Hyung Jin Sung, Korea Advanced Institute of Science and Technology, South Korea Kazuyoshi Suga, Osaka Metropolitan University, Japan Makoto Iima, Hiroshima University, Japan Yuka Iga, Tohoku University, Japan Keiichi Ishioka, Kyoto University, Japan Masahide Inagaki, Toyota Central R&D Labs., Inc., Japan Kaoru Iwamoto, Tokyo University of Agriculture and Technology, Japan Marie Oshima, The University of Tokyo, Japan Masako Sugihara-Seki, Kansai University, Japan Mamoru Tanahashi, Tokyo Institute of Technology, Japan Yoshiyuki Tsuji, Nagoya University, Japan Hiroki Nagai, Tohoku University, Japan Yasuo Nihei, Tokyo University of Science, Japan Koji Fukagata, Keio University, Japan Mizue Munakata, Kumamoto University, Japan Shinsuke Mochizuki, Okayama University, Japan Toshiyuki Gotoh, Nagoya Institute Technology, Japan Kenji Yoshida, Japan Aerospace Exploration Agency, Japan","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45289658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-08-26DOI: 10.1088/1873-7005/ac8d29
Sen Zhang, Tao Jia
To quantify the information embedded in the Lorenz system, the Shannon entropies (also named information entropies) of the convection rate, the horizontal temperature variation, and the vertical temperature variation are calculated under the conditions of different values of the three parameters which are proportional to Prandtl number, Rayleigh number, and the liquid layer dimension respectively. Generalized autoregressive conditional heteroskedasticity models are employed to represent the change of the Shannon entropies with that of the three parameters.
{"title":"Numerical investigation of the information complexity in Lorenz system based on Shannon entropy","authors":"Sen Zhang, Tao Jia","doi":"10.1088/1873-7005/ac8d29","DOIUrl":"https://doi.org/10.1088/1873-7005/ac8d29","url":null,"abstract":"To quantify the information embedded in the Lorenz system, the Shannon entropies (also named information entropies) of the convection rate, the horizontal temperature variation, and the vertical temperature variation are calculated under the conditions of different values of the three parameters which are proportional to Prandtl number, Rayleigh number, and the liquid layer dimension respectively. Generalized autoregressive conditional heteroskedasticity models are employed to represent the change of the Shannon entropies with that of the three parameters.","PeriodicalId":56311,"journal":{"name":"Fluid Dynamics Research","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49254251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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