Lissajous trajectories in electromagnetically driven vortices

2017 ◽  
Vol 815 ◽  
pp. 415-434 ◽  
Author(s):  
Aldo Figueroa ◽  
Sergio Cuevas ◽  
Eduardo Ramos
Keyword(s):  
Particle Tracking ◽  
Qualitative Agreement ◽  
Fluid Layer ◽  
Two Dimensional ◽  
Inertial Effects ◽  
Lissajous Figures ◽  
Image Velocimetry ◽  
Usual Property ◽  
Dependent Flow ◽  
Frequency Ratios

An experimental and theoretical study of laminar vortical flows driven by oscillating electromagnetic forces that act in orthogonal directions in a shallow electrolytic fluid layer is presented. Forces are generated by the interaction of the field of a dipolar permanent magnet and two imposed alternating electric currents perpendicular to each other with independent frequencies varying in the range of 10–30 mHz. Velocity fields of the time-dependent flow are obtained using particle image velocimetry, while particle tracking allows exploration of the Lagrangian trajectories and time maps. An approximate two-dimensional analytical solution is obtained for the laminar creeping regime so that Lagrangian trajectories are integrated explicitly. These trajectories resemble Lissajous figures with the usual property that, when the ratio of the frequencies of the imposed currents is rational, closed paths are found, while non-closed paths occur when this ratio is irrational. Deviations of this regime that account for slight increase of inertial effects are explored through a quasi-two-dimensional numerical simulation. In this case, non-closed paths are found even for rational frequency ratios. This case was observed in the experiment. Lagrangian trajectories calculated numerically show a qualitative agreement with experimental particle tracking. Furthermore, numerical time maps obtained for increasing inertial effects and rational frequency ratios reveal a chaotic behaviour. Some features of the Lagrangian trajectories are validated experimentally. In particular, topological properties of the calculated and observed time maps are in qualitative agreement. In a characteristic case, a partial time map calculated numerically is compared with the section acquired from the experimental tracking of one particle.

Plane turbulent jets in a bounded fluid layer

1992 ◽  
Vol 241 ◽  
pp. 587-614 ◽  
Author(s):  
T. Dracos ◽  
M. Giger ◽  
G. H. Jirka
Keyword(s):  
Experimental Investigation ◽  
Cross Section ◽  
Fluid Layer ◽  
Three Dimensional ◽  
Turbulent Jets ◽  
Two Dimensional ◽  
Vortical Structures ◽  
Secondary Currents ◽  
Fluid Layers ◽  
Bounding Surfaces

An experimental investigation of plane turbulent jets in bounded fluid layers is presented. The development of the jet is regular up to a distance from the orifice of approximately twice the depth of the fluid layer. From there on to a distance of about ten times the depth, the flow is dominated by secondary currents. The velocity distribution over a cross-section of the jet becomes three-dimensional and the jet undergoes a constriction in the midplane and a widening near the bounding surfaces. Beyond a distance of approximately ten times the depth of the bounded fluid layer the secondary currents disappear and the jet starts to meander around its centreplane. Large vortical structures develop with axes perpendicular to the bounding surfaces of the fluid layer. With increasing distance the size of these structures increases by pairing. These features of the jet are associated with the development of quasi two-dimensional turbulence. It is shown that the secondary currents and the meandering do not significantly affect the spreading of the jet. The quasi-two-dimensional turbulence, however, developing in the meandering jet, significantly influences the mixing of entrained fluid.

Modification of turbulence caused by cationic surfactant wormlike micellar structures in two-dimensional turbulent flow

2021 ◽  
Vol 933 ◽  
Author(s):  
Kengo Fukushima ◽  
Haruki Kishi ◽  
Hiroshi Suzuki ◽  
Ruri Hidema
Keyword(s):  
Turbulent Flow ◽  
Surfactant Solution ◽  
Turbulent Energy ◽  
Molar Ratio ◽  
Wormlike Micelles ◽  
Two Dimensional ◽  
Turbulence Statistics ◽  
Image Velocimetry ◽  
Set Up ◽  
Induced Structure

An experimental study is performed to investigate the effects of the extensional rheological properties of drag-reducing wormlike micellar solutions on the vortex deformation and turbulence statistics in two-dimensional (2-D) turbulent flow. A self-standing 2-D turbulent flow was used as the experimental set-up, and the flow was observed through interference pattern monitoring and particle image velocimetry. Vortex shedding and turbulence statistics in the flow were affected by the formation of wormlike micelles and were enhanced by increasing the molar ratio of the counter-ion supplier to the surfactant, ξ, or by applying extensional stresses to the solution. In the 2-D turbulent flow, extensional and shear rates were applied to the fluids around a comb of equally spaced cylinders. This induced the formation of a structure made of wormlike micelles just behind the cylinder. The flow-induced structure influenced the velocity fields around the comb and the turbulence statistics. A characteristic increase in turbulent energy was observed, which decreased slowly downstream. The results implied that the characteristic modification of the 2-D turbulent flow of the drag-reducing surfactant solution was affected by the formation and slow relaxation of the flow-induced structure. The relaxation process of the flow-induced structure made of wormlike micelles was very different from that of the polymers.

scholarly journals Toward understanding the multiscale spatial spectrum of solar convection

2012 ◽  
Vol 8 (S294) ◽  
pp. 361-363
Author(s):  
A. V. Getling ◽  
O. S. Mazhorova ◽  
O. V. Shcheritsa
Keyword(s):  
Convective Instability ◽  
Convective Flow ◽  
Large Scale ◽  
Fluid Layer ◽  
Boussinesq Equations ◽  
Spatial Spectrum ◽  
Small Scale ◽  
Two Dimensional ◽  
Solar Convection

AbstractConvection is simulated numerically based on two-dimensional Boussinesq equations for a fluid layer with a specially chosen stratification such that the convective instability is much stronger in a thin subsurface sublayer than in the remaining part of the layer. The developing convective flow has a small-scale component superposed onto a basic large-scale roll flow.

Experimental Observation of Convection during Equiaxed Solidification of Transparent Alloys

2006 ◽  
Vol 508 ◽  
pp. 157-162 ◽  
Author(s):  
Sven Eck ◽  
J.P. Mogeritsch ◽  
Andreas Ludwig
Keyword(s):  
Particle Image Velocimetry ◽  
Size Distribution ◽  
Particle Tracking ◽  
Sedimentation Rate ◽  
Particle Image ◽  
Number Density ◽  
Experimental Conditions ◽  
Equiaxed Solidification ◽  
Image Velocimetry ◽  
Experimental Runs

3D samples of NH4Cl-H2O solutions were solidified under defined experimental conditions. The occurring melt convection was investigated by Particle Image Velocimetry (PIV). The occurrence of NH4Cl crystals was observed optically and first attempts were made to quantitatively measure its number density, size distribution and sedimentation rate by PIV and Particle Tracking (PT). In order to prove the reproducibility of the results several experimental runs with equal and slightly modified conditions were analyzed.

Abstract 14952: Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV)

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Ahmad Falahatpisheh ◽  
Arash Kheradvar
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Contrast Echocardiography ◽  
Ultrasound Contrast Agent ◽  
Three Dimensions ◽  
Small Scale ◽  
High Temporal Resolution ◽  
Two Dimensional ◽  
Particle Image Velocimetry Technique ◽  
Image Velocimetry

Introduction: The two-dimensional (2D) echocardiographic particle image velocimetry technique that was introduced in 2010 received much attention in clinical cardiology. Cardiac flow visualization based on contrast echocardiography results in images with high temporal resolution that are obtainable at relatively low cost. This makes it an ideal diagnostic and follow-up tool for routine clinical use. However, cardiac flow in a cardiac cycle is multidirectional with a tendency to spin in three dimensions rather than two-dimensional curl. Here, for the first time, we introduce a volumetric echocardiographic particle image velocimetry technique that robustly acquires the flow in three spatial dimensions and in time: Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV). Methods: V-Echo-PIV technique utilizes matrix array 3D ultrasound probes to capture the flow seeded with an ultrasound contrast agent (Definity). For this feasibility study, we used a pulse duplicator with a silicone ventricular sac along with bioprosthetic heart valves at the inlet and outlet. GE Vivid E9 system with an Active Matrix 4D Volume Phased Array probe at 30 Hz was used to capture the flow data (Figure 1). Results: The 3D particle field was obtained with excellent spatial resolution without significant noise (Figure 1). 3D velocity field was successfully captured for multiple cardiac cycles. Flow features are shown in Figure 2 where the velocity vectors in two selected slices and some streamlines in 3D space are depicted. Conclusions: We report successful completion of the feasibility studies for volumetric echocardiographic PIV in an LV phantom. The small-scale features of flow in the LV phantom were revealed by this technique. Validation and human studies are currently in progress.

Flow analysis of biconvective heat and mass transfer of two-dimensional couple stress fluid over a paraboloid of revolution

2020 ◽  
Vol 34 (11) ◽  
pp. 2050110 ◽  
Author(s):  
Ahmed Zeeshan ◽  
Zeeshan Ali ◽  
Mohammad Rahimi Gorji ◽  
Farooq Hussain ◽  
S. Nadeem
Keyword(s):  
Boundary Layer ◽  
Couple Stress ◽  
Fluid Layer ◽  
Flow Analysis ◽  
Couple Stress Fluid ◽  
Two Dimensional ◽  
Nonlinear Odes ◽  
Similarity Transformations ◽  
Paraboloid Of Revolution ◽  
Stream Functions

In this paper, two-dimensional non-Newtonian couple stress fluid flow over the upper horizontal surface of a paraboloid (uhsp) (shaped like a submarine or any aerodynamical automobile) is investigated. At the freestream, a stretching of the fluid layer is assumed along with catalytic surface reaction which tends to induce the flow in the fluid-saturated domain. The problem is modeled by engaging laws of conservation for mass, momentum, heat and concentration. Velocity components are converted to stream functions and similarity transformations to reduce the dependent and independent variables in the partial differential equation describing the flow. Stream functions ideally satisfy continuity equation and transformation to reduce the PDEs to the system of coupled nonlinear ODEs. The numerical solution of these equations is obtained using the shooting-RKF method. The graphical results show that both the lateral and horizontal velocities decrease by increasing the couple stress material parameter and cause the temperature to rise. The thermal boundary layer decreases subject to the thickness parameter and has appositive effects on concentration boundary layer. Finally, numerical results have also been tabulated.

On the Vibration Damping of a Plate by Means of a Viscous Fluid Layer

1987 ◽  
Vol 109 (2) ◽  
pp. 178-184 ◽  
Author(s):  
K. Uno Ingard ◽  
Adnan Akay
Keyword(s):  
Viscous Fluid ◽  
Frequency Response ◽  
Flow Resistance ◽  
Acoustic Radiation ◽  
Fluid Layer ◽  
Vibration Damping ◽  
Plate Motion ◽  
Flexible Plate ◽  
Dependent Flow ◽  
Rigid Plane

Vibration damping of a plate by means of a fluid layer is investigated. First, the frequency-dependent flow resistance of a fluid layer is explained with a simple illustration of the damping mechanism. Then, the vibration response of a plate is examined when it is backed by a rigid plane or another flexible plate with a fluid layer constricted in-between. Effects of the plate motion and acoustic radiation on the damping mechanism are also considered. The numerical results are presented in terms of frequency response of the plates.

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