Spiral structure of the liquid particles trajectories near free surface of the vortex

2019 ◽  
pp. 67-77
Author(s):  
Анатолий Васильевич Кистович ◽  
Татьяна Олеговна Чаплина ◽  
Евгения Вячеславовна Степанова
Keyword(s):  
Free Surface ◽  
Velocity Field ◽  
Vortex Flow ◽  
Experimental Studies ◽  
Logarithmic Spiral ◽  
Zero Approximation ◽  
Helical Line ◽  
Liquid Particle ◽  
Particles Trajectories ◽  
Compound Vortex

Экспериментально и аналитически исследованы характеристики вихревого течения со свободной поверхностью, образующегося в результате вращения активаторного диска, расположенного на дне цилиндрического контейнера, заполненного водой. Получены аналитические выражения, показывающие, что траектории жидких частиц вблизи поверхности вихря представляют собой трехмерные спирали, по которым происходит течение от периферии к центу вихря. Показано, что рассчитанные и визуализированные траектории жидких частиц хорошо согласуются между собой и относятся к классу пространственных логарифмических спиралей. The work is aimed to compare results of analytical and experimental modeling of vortex fluid flow. The compound flow of liquid (water) occurs in a vertical cylindrical container without upper endwall under the action of the disk rotating at the bottom endwall. The two main components of the emerging flow are the toroidal vortex and the vortex with vertical axis. The equations are written in the cylindrical coordinate system dictated by the geometry of the problem. On the basis of the existing analytical expression, which describes the free surface form of the compound vortex in the zero approximation, an approach is developed to describe the trajectories of individual “liquid particles”. The obtained result allows to explore the velocity field structure near the free surface. The obtained expressions indicate that the velocity field near free surface becomes more pronounced in the tangent direction. This result is confirmed in the experimental studies of the compound vortex flow. The analytical forms of liquid particle trajectories near and on the free surface of the compound vortex are obtained. The general particle movement is from the container sidewall along the free surface to its center and further down the spiral-helical line. The images of the visualized particles trajectories both on the free surface (logarithmic spiral) and in the liquid depth are obtained in experiments and testify in favor of the implemented approach to the construction of analytical solution of the liquid particle motion for the vortex flow of the mentioned type. The correspondence of the calculated free surface forms obtained with the help of analytical expressions and those observed in the experiments with different parameters of the vortex flow shows that the developed approach to the problem can be based on a simplified description.

scholarly journals The role of boundary conditions on the free surface of a liquid metal in an electrovortex flow

2021 ◽  
Vol 2088 (1) ◽  
pp. 012047
Author(s):  
I O Teplyakov ◽  
S V Kiselyova ◽  
K Yu Malyshev ◽  
E A Mikhaylov
Keyword(s):  
Boundary Condition ◽  
Free Surface ◽  
Velocity Field ◽  
Liquid Metal ◽  
Boundary Conditions ◽  
Liquid Medium ◽  
Vortex Flow ◽  
Conducting Liquid ◽  
Small Electrode

Abstract An electro-vortex flow between two hemispherical electrodes is considered. The influence of the type of boundary condition on the surface of a conducting liquid medium on the velocity field in the volume is studied numerically. The dependences of the velocity on the axis of the vessel on the radius of the small electrode and the parameter of the electric vortex flow are obtained for various types of boundary conditions on the surface.

scholarly journals The intimate relationship between structural relaxation and the energy landscape of monatomic liquid metals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Franz Demmel ◽  
Louis Hennet ◽  
Noel Jakse
Keyword(s):  
High Temperature ◽  
Velocity Field ◽  
Liquid State ◽  
Liquid Metals ◽  
Energy Landscape ◽  
Experimental Studies ◽  
Transport Parameter ◽  
Arrhenius Behavior ◽  
Liquid Aluminium ◽  
Potential Energy Landscape

AbstractThe characteristic property of a liquid, discriminating it from a solid, is its fluidity, which can be expressed by a velocity field. The reaction of the velocity field on forces is enshrined in the transport parameter viscosity. In contrast, a solid reacts to forces elastically through a displacement field, the particles are trapped in their potential minimum. The flow in a liquid needs enough thermal energy to overcome the changing potential barriers, which is supported through a continuous rearrangement of surrounding particles. Cooling a liquid will decrease the fluidity of a particle and the mobility of the neighbouring particles, resulting in an increase of the viscosity until the system comes to an arrest. This process with a concomitant slowing down of collective particle rearrangements might already start deep inside the liquid state. The idea of the potential energy landscape provides an attractive picture for these dramatic changes. However, despite the appealing idea there is a scarcity of quantitative assessments, in particular, when it comes to experimental studies. Here we present results on a monatomic liquid metal through a combination of ab initio molecular dynamics, neutron spectroscopy and inelastic x-ray scattering. We investigated the collective dynamics of liquid aluminium to reveal the changes in dynamics when the high temperature liquid is cooled towards solidification. The results demonstrate the main signatures of the energy landscape picture, a reduction in the internal atomic structural energy, a transition to a stretched relaxation process and a deviation from the high-temperature Arrhenius behavior of the relaxation time. All changes occur in the same temperature range at about $$1.4 \cdot T_{melting}$$ 1.4 · T melting , which can be regarded as the temperature when the liquid aluminium enters the landscape influenced phase and enters a more viscous liquid state towards solidification. The similarity in dynamics with other monatomic liquid metals suggests a universal dynamic crossover above the melting point.

Magnetohydrodynamic flow due to the discharge of an electric current in a hemispherical container

1976 ◽  
Vol 73 (4) ◽  
pp. 641-650 ◽  
Author(s):  
C. Sozou ◽  
W. M. Pickering
Keyword(s):  
Free Surface ◽  
Velocity Field ◽  
Flow Field ◽  
Electric Current ◽  
Cross Section ◽  
Analytic Solution ◽  
Closed Loops ◽  
Slow Viscous Flow ◽  
Axial Cross Section ◽  
Section Form

In this paper we consider the flow field induced in an incompressible viscous conducting fluid in a hemispherical bowl by a symmetric discharge of electric current from a point source at the centre of the plane end of the hemisphere. This plane end is a free surface. We construct an analytic solution for the slow viscous flow and a numeriacl solution for the nonlinear problem. The streamlines in an axial cross-section form two sets of closed loops, one on either side of the axis. Our computations indicate that, for a given fluid, when the discharged current reaches a certain magnitude the velocity field breaks down. This breakdown probably originates at the vertex of the hemispherical container.

scholarly journals Thermo-mechanical behavior of a granular media in a rotating drum

2019 ◽  
Vol 20 (2) ◽  
pp. 203
Author(s):  
Soumia Teyar ◽  
Mathieu Renouf ◽  
Yves Berthier
Keyword(s):  
Free Surface ◽  
Velocity Field ◽  
Numerical Experiment ◽  
Granular Flow ◽  
Granular Media ◽  
Free Surface Flows ◽  
Rail Transport ◽  
Rotating Drum ◽  
Electrical Behavior ◽  
Surface Flows

In the complex granular flow, the shear and flow of particles lead to increase in temperature that can enchain behavioral modifications. However, their thermo-mechanical and electrical behavior is of great interest for applications such as rail transport, grinding, and granular material reproduction systems. To study these behaviors, a numerical experiment is carried out on a rotating drum model. This device makes it possible to generate continuous and controlled free surface flows. Relying on the NSCD approach, the location of the hottest zone and the evolution of the temperature are correlated with the evolution of the velocity field.

Flat plate impact on water

2018 ◽  
Vol 850 ◽  
pp. 1066-1116 ◽  
Author(s):  
Hans C. Mayer ◽  
Rouslan Krechetnikov
Keyword(s):  
Free Surface ◽  
Velocity Field ◽  
Flat Plate ◽  
Classical Problem ◽  
Water Impact ◽  
Plate Impact ◽  
Plate Edge ◽  
Trapped Air ◽  
Impact Phenomena ◽  
The Impact

While the classical problem of a flat plate impact on a water surface at zero dead-rise angle has been studied for a long time both theoretically and experimentally, it still presents a number of challenges and unsolved questions. Hitherto, the details of the flow field – especially at early times and close to the plate edge, where the classical inviscid theory predicts a singularity in the velocity field and thus in the free surface deflection, so-called ejecta – have not been studied experimentally, which led to mutually contradicting suppositions in the literature. On one hand, it motivated Yakimov’s self-similar scaling near the plate edge. On the other hand, a removal of the singularity was previously suggested with the help of the Kutta–Joukowsky condition at the plate edge, i.e. enforcing the free surface to depart tangentially to the plate. In the present experimental study we were able to overcome challenges with optical access and investigate, for moderate Reynolds ($0.5<Re<25\,000$) and Weber ($1<We<800$) numbers, both the flow fields and the free surface dynamics at the early stage of the water impact, when the penetration depth is small compared to the plate size, thus allowing us to compare to the classical water impact theory valid in the short time limit. This, in particular, enabled us to uncover the effects of viscosity and surface tension on the velocity field and ejecta evolution usually neglected in theoretical studies. While we were able to confirm the far-field inviscid and the near-edge Stokes theoretical scalings of the free surface profiles, Yakimov’s scaling of the velocity field proved to be inapplicable and the Kutta–Joukowsky condition not satisfied universally in the studied range of Reynolds and Weber numbers. Since the local near-edge phenomena cannot be considered independently of the complete water impact event, the experiments were also set up to study the entirety of the water impact phenomena under realistic conditions – presence of air phase and finite depth of penetration. This allowed us to obtain insights also into other key aspects of the water impact phenomena such as air entrapment and pocketing at the later stage when the impactor bottoms out. In our experiments the volume of trapped air proved not to decrease necessarily with the impact speed, an effect that has not been reported before. The observed fast initial retraction of the trapped air film along the plate bottom turned out to be a consequence of a negative pressure impulse generated upon the abrupt deceleration of the plate. This abrupt deceleration is also the cause of the subsequent air pocketing. Quantitative measurements are complemented with basic scaling models explaining the nature of both retraction of the trapped air and air pocket formation.

Development of a Computer Simulation Technique for Predicting Heat Transfer in Multiphase Liquid-Particle Flow Systems

2007 ◽  
Author(s):  
Kevin F. Malone ◽  
Bao H. Xu ◽  
Michael Fairweather
Keyword(s):  
Heat Transfer ◽  
Spent Nuclear Fuel ◽  
Experimental Studies ◽  
Particle Flow ◽  
Liquid Particle ◽  
Pilot Studies ◽  
Simulation Tools ◽  
Highly Active ◽  
Flow Systems ◽  
Intermediate Storage

Many of the highly active waste liquors that result from the reprocessing of spent nuclear fuel contain particulate solids of various materials. Operations for safe processing, handling and intermediate storage of these wastes often pose significant technical challenges due to the need for effective cooling systems to remove the heat generated by the radioactive solids. The multiscale complexity of liquid-particle flow systems is such that investigation and prediction of their heat transfer characteristics based on experimental studies is a difficult task. Fortunately, the increasing availability of cheap computing power means that predictive simulation tools may be able to provide a means to investigate these systems without the need for expensive pilot studies. In this work we describe the development of a Combined Continuum and Discrete Model (CCDM) for predicting the heat transfer behaviour of systems of particles suspended in liquids.

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