Mode transformations of vortex shedding behind a sphere with the effect of Lorentz force

2021 ◽  
Vol 33 (12) ◽  
pp. 123601
Author(s):  
Weiguang Yao ◽  
Hui Zhang ◽  
Daiwen Jiang ◽  
Mingyue Gui ◽  
Zijie Zhao ◽  
...  
Keyword(s):  
Lorentz Force ◽  
Vortex Shedding

Optimal Control of Vortex Shedding by an Electro-Magnetic Field (Keynote)

2002 ◽  
Author(s):  
Xiaoyun Sun ◽  
Nadine Aubry
Keyword(s):  
Optimal Control ◽  
Lorentz Force ◽  
Vortex Shedding ◽  
Asymptotic Methods ◽  
Cylinder Surface ◽  
Electro Magnetic Field ◽  
Active Feedback ◽  
Flow Past A Cylinder ◽  
Electro Magnetic ◽  
New Formulation

The goal of this work is to suppress vortex shedding in the flow past a cylinder by means of a Lorentz force generated by electrodes and magnets placed on the cylinder surface alternatively. Unlike previous control schemes that were based on a crude planar structure model for the expression of the Lorentz force, our algorithm is based on an expression of the Lorentz force utilizing the electrical and magnetic potential functions, and the cylindrical structure. Asymptotic methods are used to simplify the result. The new formulation, in particular, leads to a continuous force distribution around the cylinder surface. Optimal control theory is used to derive an active feedback control algorithm aiming at determining the optimal force at each time.

CONTROL OF VORTEX SHEDDING BEHIND A CIRCULAR CYLINDER USING ELECTROMAGNETIC FORCES

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1627-1630 ◽  
Author(s):  
ZHIHUA CHEN ◽  
BAOCHUN FAN ◽  
BENMOU ZHOU ◽  
NADINE AUBRY
Keyword(s):  
Circular Cylinder ◽  
Lorentz Force ◽  
Vortex Shedding ◽  
Closed Loop ◽  
Permanent Magnets ◽  
Control Method ◽  
The Body ◽  
Closed Loop Control ◽  
Electromagnetic Forces ◽  
Loop Control

Both open and closed loop control algorithms have been developed for manipulating wake flows past a solid cylinder in an electrically low-conducting fluid. The intent is to avoid vortex shedding and flow separation from the body, which is achieved through the introduction of localized electromagnetic forces (Lorentz forces) in the azimuthal direction generated by an array of permanent magnets and electrodes on the surface of the circular cylinder. The array of actuators offers the advantage of making the Lorentz force time and space dependent. More specifically, one closed loop control method has been derived from the equations of motion capable of determining at all times the intensity of the Lorentz force in order to control the flow. This is accomplished first, independently of the flow (open loop algorithm) and second, based on some partial flow information measured on the surface of the solid body (closed loop algorithm).

Numerical Studies on Behavior of Lorentz-Force-Applied Boundary Layer in Supersonic Flow

2009 ◽  
Vol 129 (6) ◽  
pp. 831-839
Author(s):  
Keisuke Udagawa ◽  
Sadatake Tomioka ◽  
Hiroyuki Yamasaki
Keyword(s):  
Boundary Layer ◽  
Supersonic Flow ◽  
Lorentz Force ◽  
Numerical Studies

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.

Some modeling issues on trailing-edge vortex shedding

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 787-793
Author(s):  
Wei Ning ◽  
Li He
Keyword(s):  
Vortex Shedding ◽  
Trailing Edge ◽  
Edge Vortex
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