scholarly journals Influence of Periodic Flow on Vortex Shedding of Oscillating Wing

2020 ◽  
Vol 2020.95 (0) ◽  
pp. P_028
Author(s):  
Yoshitaka ISODA ◽  
Yohsuke TANAKA ◽  
Shigeru MURATA
Keyword(s):  
Vortex Shedding ◽  
Periodic Flow

Measurements of Bluff Body Wake Flow Around a Conformable Flow Control Surface

2003 ◽  
Author(s):  
David A. Ericson ◽  
Michael Jonson ◽  
Gary Koopmann
Keyword(s):  
Flow Control ◽  
Vortex Shedding ◽  
Flow Separation ◽  
Bluff Body ◽  
The Body ◽  
Control Surface ◽  
Periodic Flow ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Shedding Frequency

The vortex street is a unique type of unsteady flow separation seen commonly in flow over a bluff body with a characteristic periodic wake. A consequence of the periodic flow is that the drag and lift forces acting on the body also oscillate periodically. When the wake shedding frequency is near a structural frequency, flow induced resonance will occur. The continuing interest in the study of vortex street generation is propelled by the ever-present nature of these flows in a variety of applications including aerodynamics, hydrodynamics and underwater acoustics. Recent advances in material science and the development of high power density actuators have led to the study of adaptive structure technology wherein the vorticity of periodic flows can be actively controlled by changing the ‘bluffness’ or shape of the body. In this paper, the development and experimental testing of a two-dimensional shape-variable flow control surface are discussed in relation to the generation and manipulation of periodic flow separation. Two series of wind tunnel tests were designed to evaluate the potential of the morphing structure that replaced a section of the trailing edge of a symmetric airfoil. The test section successfully demonstrated a smooth transition between three prescribed trailing edge profiles ranging from sharp to blunt. Unsteady pressure spectra were measured near the trailing edge for three different shape profiles over a range of speeds between 50 and 110 ft/s. The measured pressure spectra amplitudes were compared to previously-published surface pressure spectra of a similar, two-dimensional, blunt edge foil. A second set of tests was performed to measure the resulting flow field in the direction transverse to the flow and downstream from the airfoil. Velocity measurements were made using a traversing hot-wire probe at three trailing edge configurations and speeds of 50, 70 and 90 ft/s. The corresponding Reynolds number based on wake thickness ranged from 3.9–9.8 × 104. Measured vortex shedding frequencies varied between approximately 50 to 130 Hz at the different trailing edge profiles. This type of change in the vortex shedding frequency can be used to reduce flow-induced vibration and its associated noise generation by avoiding shedding frequencies at operating speeds that coincide with airfoil resonances.

Review—Vortex Shedding Lock-on and Flow Control in Bluff Body Wakes

1991 ◽  
Vol 113 (4) ◽  
pp. 526-537 ◽  
Author(s):  
O. M. Griffin ◽  
M. S. Hall
Keyword(s):  
Vortex Shedding ◽  
Bluff Body ◽  
The Body ◽  
Periodic Flow ◽  
Cylinder Wake ◽  
Mean Flow ◽  
Near Wake ◽  
Strong Resonance ◽  
And Control ◽  
Rotational Oscillations

The results of recent experiments demonstrate that the phenomenon of vortex shedding resonance or lock-on is observed also when a bluff body is placed in an incident mean flow with a periodic component superimposed upon it. This form of vortex shedding and lock-on exhibits a particularly strong resonance between the flow perturbations and the vortices, and provides one of several promising means for modification and control of the basic formation and stability mechanisms in the near-wake of a bluff body. Examples are given of recent direct numerical simulations of the vortex lock-on in the periodic flow. These agree well with the results of experiments. A discussion also is given of vortex lock-on due to body oscillations both normal to and in-line with the incident mean flow, rotational oscillations of the body, and of the effect of sound on lock-on. The lock-on phenomenon is discussed in the overall context of active and passive wake control, on the basis of these and other recent and related results, with particular emphasis placed on active control of the circular cylinder wake.

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

COMPARISON OF LES WITH DSM, k-ε AND EXPERIMENTS FORTURBULENT VORTEX SHEDDING FLOW PAST 2D SQUARE CYLINDER

1994 ◽  
Vol 59 (459) ◽  
pp. 49-56 ◽  
Author(s):  
Shigehiro SAKAMOTO ◽  
Akashi MOCHIDA ◽  
Shuzo MURAKAMI ◽  
Wolfgang RODI
Keyword(s):  
Vortex Shedding ◽  
Square Cylinder ◽  
Flow Past

Scheme of the computational experiment for the construction of an element of the research stand of the fuel metering unit

2014 ◽  
Vol 10 ◽  
pp. 87-89
Author(s):  
I.Sh. Nasibullayev ◽  
E.Sh. Nasibullaeva ◽  
E.V. Denisova
Keyword(s):  
Fuel Consumption ◽  
Computational Experiment ◽  
Cylindrical Tube ◽  
Viscous Friction ◽  
Periodic Flow ◽  
Objective Functions ◽  
Computing Experiment ◽  
Full Factorial

In this paper, the motion of a piston in a cylindrical tube is numerically studied with influence of dry and viscous friction and spring elasticity. Leading factors for models with dry and viscous friction are determined. A scheme for performing a full factorial computing experiment is proposed, where fuel consumption per unit time and fuel consumption for the period of periodic flow are chosen as objective functions.

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