Geophysical and Astrophysical Fluid Dynamics最新文献_第3页

A shallow layer laboratory model of large-scale atmospheric circulation 大尺度大气环流的浅层实验室模式

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-10-27 DOI: 10.1080/03091929.2023.2220877

A. Sukhanovskii, E. Popova, A. Vasiliev

{"title":"A shallow layer laboratory model of large-scale atmospheric circulation","authors":"A. Sukhanovskii, E. Popova, A. Vasiliev","doi":"10.1080/03091929.2023.2220877","DOIUrl":"https://doi.org/10.1080/03091929.2023.2220877","url":null,"abstract":"A new shallow layer laboratory model of global atmospheric circulation is realised and studied by experiments and numerical simulations. A shallow rotating cylindrical fluid layer of 30 mm thickness and 690 mm diameter, with a localised heater at the bottom periphery and localised cooler in the central part of the upper boundary is considered. The rim heater imitates the equator heating and disc cooler – the North pole cooling. The flow transforms from the Hadley-like regime to the baroclinic wave regime through transitional states. The decrease in the thermal Rossby number for the fixed value of Taylor number results in the regularisation of the baroclinic waves. All wave regimes, even with regular wave structures, are characterised by strong non-periodic fluctuations. The observed baroclinic wave structures are a combination of temporarily evolving different baroclinic modes. The important outcome of the shallow layer model is a realisation of the Earth-like meridional three-cell structure. It is shown that the three-cell structure with analogs of polar, Ferrel and Hadley cells exist only in a limited range of parameters. A comparison of the results for the water and silicon oil demonstrated that the physical properties of the fluid can have a strong impact on the baroclinic wave structure.","PeriodicalId":56132,"journal":{"name":"Geophysical and Astrophysical Fluid Dynamics","volume":"41 1","pages":"155 - 176"},"PeriodicalIF":1.3,"publicationDate":"2022-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76365234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Magnetoconvection in a rotating spherical shell in the presence of a uniform axial magnetic field 在有均匀轴向磁场的旋转球壳中的磁对流

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-08-12 DOI: 10.1080/03091929.2022.2107202

Stephen J. Mason, C. Guervilly, G. Sarson

{"title":"Magnetoconvection in a rotating spherical shell in the presence of a uniform axial magnetic field","authors":"Stephen J. Mason, C. Guervilly, G. Sarson","doi":"10.1080/03091929.2022.2107202","DOIUrl":"https://doi.org/10.1080/03091929.2022.2107202","url":null,"abstract":"ABSTRACT We report simulations of thermal convection and magnetic-field generation in a rapidly-rotating spherical shell, in the presence of a uniform axial magnetic field of variable strength. We consider the effect of the imposed field on the critical parameters (Rayleigh number, azimuthal wavenumber and propagation frequency) for the onset of convection, and on the relative importance of Coriolis, buoyancy and Lorentz forces in the resulting solutions. The imposed field strength must be of order one (corresponding to an Elsasser number of unity) to observe significant modifications of the flow; in this case, all the critical parameters are reduced, an effect that is more pronounced at small Ekman numbers. Beyond onset, we study the variations of the structure and properties of the magnetically-modified convective flows with increasing Rayleigh numbers. In particular, we note the weak relative kinetic helicity, the rapid breakdown of the columnarity, and the enhanced heat transport efficiency of the flows obtained for imposed field strengths of order one. Furthermore, magnetic and thermal winds drive a significant zonal flow in this case, which is not present with no imposed field or with stronger imposed fields. The mechanisms for magnetic field generation (particularly the lengthscales involved in the axisymmetric field production) vary with the strength of the imposed field, with three distinct regimes being observed for weak, order one, and stronger imposed fields. In the last two cases, the induced magnetic field reinforces the imposed field, even exceeding its strength for large Rayleigh numbers, which suggests that magnetically-modified flows might be able to produce large-scale self-sustained magnetic field. These magnetoconvection calculations are relevant to planets orbiting magnetically active hosts, and also help to elucidate the mechanisms for field generation in a strong-field regime.","PeriodicalId":56132,"journal":{"name":"Geophysical and Astrophysical Fluid Dynamics","volume":"23 1","pages":"458 - 498"},"PeriodicalIF":1.3,"publicationDate":"2022-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84389004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Multiplicity in an optimised kinematic dynamo 优化运动发电机的多重性

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-07-04 DOI: 10.1080/03091929.2022.2098284

Long Chen

{"title":"Multiplicity in an optimised kinematic dynamo","authors":"Long Chen","doi":"10.1080/03091929.2022.2098284","DOIUrl":"https://doi.org/10.1080/03091929.2022.2098284","url":null,"abstract":"Multiplicity in optimal kinematic dynamos exists for certain types of symmetry classes and boundary conditions, at least near the lowest dynamo onset . Here we investigate the NNT type dynamo generated by steady flows with impermeable boundary conditions in a cube, where the letter N or T stands for pseudo-vacuum or superconducting boundary conditions along x, y, z directions, respectively. We find the top two of the three branches in the neighbourhood of have their growth rates crossed over at . Within each branch, the spatial structure of the optimal velocity field gradually shifts with respect to . At about above , the original optimal branch has developed distinct combinations of dominant Fourier modes. In contrast, the first suboptimal branch shows the least change in structure. We then follow the evolution of selected optimised solutions when varies until it becomes unstable. Specific modes in the flow that can destabilise the dynamo are identified. Within the range surveyed, we find that there can be one to two dynamo windows. All three branches generate a steady dynamo near , but the first suboptimal branch can generate an oscillatory dynamo at about eight times , and for both suboptimal branches, the growth rate reaches saturation approximately at . We find the two suboptimal branches create a more robust dynamo action supercritically.","PeriodicalId":56132,"journal":{"name":"Geophysical and Astrophysical Fluid Dynamics","volume":"67 1","pages":"290 - 304"},"PeriodicalIF":1.3,"publicationDate":"2022-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85621201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

An exact threshold for separator bifurcation 分离器分岔的精确阈值

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-06-21 DOI: 10.1080/03091929.2022.2085696

C. Prior, P. Wyper

引用次数: 0

Rigorous results on conserved and dissipated quantities in ideal MHD turbulence 理想MHD湍流中守恒和耗散量的严格结果

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-06-13 DOI: 10.1080/03091929.2022.2060964

D. Faraco, Sauli Lindberg

{"title":"Rigorous results on conserved and dissipated quantities in ideal MHD turbulence","authors":"D. Faraco, Sauli Lindberg","doi":"10.1080/03091929.2022.2060964","DOIUrl":"https://doi.org/10.1080/03091929.2022.2060964","url":null,"abstract":"We review recent mathematical results on the theory of ideal MHD turbulence. On the one hand, we explain a mathematical version of Taylor's conjecture on magnetic helicity conservation, both for simply and multiply connected domains. On the other hand, we describe how to prove the existence of weak solutions conserving magnetic helicity but dissipating cross helicity and energy in 3D Ideal MHD. Such solutions are bounded. In fact, we show that as soon as we are below the critical integrability for magnetic helicity conservation, there are weak solutions which do not preserve even magnetic helicity. These mathematical theorems rely on understanding the mathematical relaxation of MHD which is used as a model of the macroscopic behaviour of solutions of various nonlinear partial differential equations. Thus, on the one hand, we present results on the existence of weak solutions consistent with what is expected from experiments and numerical simulations, on the other hand, we show that below certain thresholds, there exist pathological solutions which should be excluded from physical grounds. It is still an outstanding open problem to find suitable admissibility conditions that are flexible enough to allow the existence of weak solutions but rigid enough to rule out physically unrealistic behaviour.","PeriodicalId":56132,"journal":{"name":"Geophysical and Astrophysical Fluid Dynamics","volume":"1 1","pages":"237 - 260"},"PeriodicalIF":1.3,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84552240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Formation of small-scale vortices in the core of a large merged vortex 大型合并涡中心的小尺度涡的形成

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-05-25 DOI: 10.1080/03091929.2022.2074983

Erwan Oulhen, J. Reinaud, X. Carton

引用次数: 1

Effects of mesoscale turbulence on the wind-driven circulation in a closed basin with topography 中尺度湍流对地形封闭盆地风驱动环流的影响

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-05-04 DOI: 10.1080/03091929.2022.2065271

L. Zavala Sansón

引用次数: 2

Angular momentum transfer in direct numerical simulations of a laboratory model of a tropical cyclone 热带气旋实验室模式直接数值模拟中的角动量传递

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-05-04 DOI: 10.1080/03091929.2022.2066659

A. Evgrafova, A. Sukhanovskii

{"title":"Angular momentum transfer in direct numerical simulations of a laboratory model of a tropical cyclone","authors":"A. Evgrafova, A. Sukhanovskii","doi":"10.1080/03091929.2022.2066659","DOIUrl":"https://doi.org/10.1080/03091929.2022.2066659","url":null,"abstract":"ABSTRACT Numerical simulations of a laboratory model of a tropical cyclone are carried out for different rotation rates. Particular attention is paid to the non-stationary stage of intensive cyclonic vortex formation. The transfer of angular momentum plays a key role in the formation of cyclonic and anticyclonic flows; therefore, a detailed analysis of the redistribution and variation of angular momentum is given. The time evolution of angular momentum fluxes and total angular momentum strongly depend on the rotation rate. It is shown that intensive cyclonic motion with velocity exceeding initial values substantially (ten or more times) is a result of accumulation in the centre of a small fraction of global angular momentum of a fluid layer (from 0.25% at fast rotation to 2% at slow rotation). The integral angular momentum of the anticyclonic flow is significantly larger than that of the cyclonic flow, mainly because of the relatively large fluid volume of the anticyclonic flow. Another important result is that the rotating fluid layer very quickly adapts to new boundary conditions (heating and cooling). Approximately two rotation periods are required to reach a quasi-stationary state. The application of the obtained results to the evolution of real tropical cyclones is discussed.","PeriodicalId":56132,"journal":{"name":"Geophysical and Astrophysical Fluid Dynamics","volume":"22 1","pages":"185 - 205"},"PeriodicalIF":1.3,"publicationDate":"2022-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83298009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Comments on: nonlinear wind-drift ocean currents in arctic regions 评论:北极地区的非线性风漂洋流

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-03-04 DOI: 10.1080/03091929.2022.2036337

A. Constantin

引用次数: 3

Different approaches in scattering of water waves by two submerged porous plates over an elastic sea-floor 弹性海底上两个浸没的多孔板对水波散射的不同方法

IF 1.3 4区地球科学

Geophysical and Astrophysical Fluid Dynamics Pub Date : 2022-02-07 DOI: 10.1080/03091929.2022.2025792

Ayan Chanda, S. Bora

{"title":"Different approaches in scattering of water waves by two submerged porous plates over an elastic sea-floor","authors":"Ayan Chanda, S. Bora","doi":"10.1080/03091929.2022.2025792","DOIUrl":"https://doi.org/10.1080/03091929.2022.2025792","url":null,"abstract":"A hydroelastic model is presented here to look into the scattering of oblique water waves by two totally submerged vertical porous plates, placed at some distance from each other, in a homogeneous fluid flowing over an elastic sea-floor. Consideration of Euler–Bernoulli beam equation allows the elastic sea-floor to be approximated as a thin elastic plate whereas the porous plates follow the porous wave-maker theory. The complete analytical solution, under the assumption of small-amplitude theory and structural response, is obtained by employing eigenfunction expansion and least square method. Subsequently, numerical computation for the reflection and transmission coefficients and energy loss are carried out and discussed for different values of the elasticity of the sea-floor, porosity of the porous plates and other structural parameters. The present study establishes that reflection of the waves exhibits an oscillatory behaviour. It further shows that, due to an increase in the inertial effect of the porous plate, the minima in wave reflection occurs. The vertical porous plates are found to dissipate a significant portion of the wave energy when an increase in the inertial effect of the porous plates takes place. Furthermore, wave transmission decreases significantly due to the energy dissipation by the elastic sea-floor. Significant variation in the elastic specification of the sea-floor commands considerable influence when the propagating wave impinges upon the submerged vertical porous plates. In order to validate the present model, the obtained results are compared with available results which points towards a good agreement.","PeriodicalId":56132,"journal":{"name":"Geophysical and Astrophysical Fluid Dynamics","volume":"98 1","pages":"206 - 233"},"PeriodicalIF":1.3,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86049219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5