A self-learning coupled map lattice for vortex shedding in cable and cylinder wakes

2004 ◽  
Vol 14 (2) ◽  
pp. 293-304
Author(s):  
G. Balasubramanian ◽  
D. J. Olinger ◽  
M. A. Demetriou
Keyword(s):  
Vortex Shedding ◽  
Coupled Map Lattice ◽  
Self Learning ◽  
Cylinder Wakes

Control of a coupled map lattice model for vortex shedding in the wake of a cylinder

Pramana ◽  
2002 ◽  
Vol 59 (1) ◽  
pp. 91-111
Author(s):  
G Balasubramanian ◽  
DJ Olinger ◽  
MA Demetriou
Keyword(s):  
Vortex Shedding ◽  
Lattice Model ◽  
Coupled Map Lattice

Nonlinear modelling of vortex shedding control in cylinder wakes

1996 ◽  
Vol 97 (1-3) ◽  
pp. 264-273 ◽  
Author(s):  
Kimon Roussopoulos ◽  
Peter A. Monkewitz
Keyword(s):  
Vortex Shedding ◽  
Nonlinear Modelling ◽  
Cylinder Wakes

The flow behind rings: bluff body wakes without end effects

1995 ◽  
Vol 288 ◽  
pp. 265-310 ◽  
Author(s):  
T. Leweke ◽  
M. Provansal
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Reynolds Numbers ◽  
Finite Cylinder ◽  
Near Wake ◽  
End Effects ◽  
Ginzburg Landau ◽  
Landau Model ◽  
Cylinder Wakes

Recent studies have demonstrated the strong influence of end effects on low-Reynoldsnumber bluff body wakes, and a number of questions remain concerning the intrinsic nature of three-dimensional phenomena in two-dimensional configurations. Some of them are answered by the present study which investigates the wake of bluff rings (i.e. bodies without ends) both experimentally and by application of the phenomenological Ginzburg–Landau model. The model turns out to be very accurate in describing qualitative and quantitative observations in a large Reynolds number interval. The experimental study of the periodic vortex shedding regime shows the existence of discrete shedding modes, in which the wake takes the form of parallel vortex rings or ‘oblique’ helical vortices, depending on initial conditions. The Strouhal number is found to decrease with growing body curvature, and a global expression for the Strouhal–Reynolds number relation, including curvature and shedding angle, is proposed, which is consistent with previous straight cylinder results. A secondary instability of the helical modes at low Reynolds numbers is discovered, and a detailed comparison with the Ginzburg–Landau model identifies it as the Eckhaus modulational instability of the spanwise structure of the near-wake formation region. It is independent of curvature and its clear observation in straight cylinder wakes is inhibited by end effects.The dynamical model is extended to higher Reynolds numbers by introducing variable parameters. In this way the instability of periodic vortex shedding which marks the beginning of the transition range is characterized as the Benjamin–Feir instability of the coupled oscillation of the near wake. It is independent of the shear layer transition to turbulence, which is known to occur at higher Reynolds numbers. The unusual shape of the Strouhal curve in this flow regime, including the discontinuity at the transition point, is qualitatively reproduced by the Ginzburg–Landau model. End effects in finite cylinder wakes are found to cause important changes in the transition behaviour also: they create a second Strouhal discontinuity, which is not observed in the present ring wake experiments.

scholarly journals Model-based estimation of vortex shedding in unsteady cylinder wakes

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Jiwen Gong ◽  
Jason P. Monty ◽  
Simon J. Illingworth
Keyword(s):  
Vortex Shedding ◽  
Model Based ◽  
Cylinder Wakes

Evolution of unstable system.

2015 ◽  
Vol 9 (3) ◽  
pp. 2487-2502 ◽  
Author(s):  
Igor V. Lebed
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Stokes Flow ◽  
Stable Solution ◽  
The State ◽  
Unstable System ◽  
Unstable Flow ◽  
Unstable Solutions ◽  
Vortex Shedding Modes ◽  
Hydrodynamics Equations

Scenario of appearance and development of instability in problem of a flow around a solid sphere at rest is discussed. The scenario was created by solutions to the multimoment hydrodynamics equations, which were applied to investigate the unstable phenomena. These solutions allow interpreting Stokes flow, periodic pulsations of the recirculating zone in the wake behind the sphere, the phenomenon of vortex shedding observed experimentally. In accordance with the scenario, system loses its stability when entropy outflow through surface confining the system cannot be compensated by entropy produced within the system. The system does not find a new stable position after losing its stability, that is, the system remains further unstable. As Reynolds number grows, one unstable flow regime is replaced by another. The replacement is governed tendency of the system to discover fastest path to depart from the state of statistical equilibrium. This striving, however, does not lead the system to disintegration. Periodically, reverse solutions to the multimoment hydrodynamics equations change the nature of evolution and guide the unstable system in a highly unlikely direction. In case of unstable system, unlikely path meets the direction of approaching the state of statistical equilibrium. Such behavior of the system contradicts the scenario created by solutions to the classic hydrodynamics equations. Unstable solutions to the classic hydrodynamics equations are not fairly prolonged along time to interpret experiment. Stable solutions satisfactorily reproduce all observed stable medium states. As Reynolds number grows one stable solution is replaced by another. They are, however, incapable of reproducing any of unstable regimes recorded experimentally. In particular, stable solutions to the classic hydrodynamics equations cannot put anything in correspondence to any of observed vortex shedding modes. In accordance with our interpretation, the reason for this isthe classic hydrodynamics equations themselves.

ANALYSIS OF STUDENT ACTIVITIES ON COMPUTER - A STUDY ON PUNJAB UNIVERSITY, INDIA

2012 ◽  
Vol 3 (3) ◽  
pp. 354-358
Author(s):  
Dr Gunmala Suri ◽  
Sneha Sharma
Keyword(s):  
Learning Activities ◽  
Information Collection ◽  
Learning Tools ◽  
Student Activities ◽  
Group Activities ◽  
E Learning ◽  
Faculty Department ◽  
Self Learning

The purpose of this research is to investigate and understand how students are using computer. The activities that a student undertakes with the help of computers which might be fulfilling some academic or non academic purpose, is of great interest. It will help in understanding the limitations and potentials offered by the technology for use of computer in classroom. This paper brings out the three major kinds of activities that students undertake with computer; self learning activities, Information collection tasks and communication and group activities. The study further analyses the effect of demographics i.e. gender, age and faculty (department) of students on the activities with computer. The results show that gender has no impact on the activities of students with computer. The age impacts only the activities related to Information collection by using computer where as the faculty of student significantly impacts all the activities viz. self learning activities, Information collection tasks and communication and group activities. The findings from this research can be used in designing future e-learning initiatives and development e-learning tools

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