scholarly journals Vortex Dynamics in Near Wake of a Hovering Hawkmoth

2008 ◽  
Author(s):  
Hikaru Aono ◽  
Wei Shyy ◽  
Hao Liu
Keyword(s):  
Vortex Dynamics ◽  
Near Wake

scholarly journals Stabilizing effect of flexibility in the wake of a flapping foil

2012 ◽  
Vol 710 ◽  
pp. 659-669 ◽  
Author(s):  
C. Marais ◽  
B. Thiria ◽  
J. E. Wesfreid ◽  
R. Godoy-Diana
Keyword(s):  
Symmetry Breaking ◽  
Vortex Dynamics ◽  
Momentum Balance ◽  
Near Wake ◽  
Low Speed ◽  
Flapping Foil ◽  
Balance Calculation ◽  
Stabilizing Effect ◽  
Dynamical Features ◽  
Regime Transitions

AbstractThe wake of a flexible foil undergoing pitching oscillations in a low-speed hydrodynamic tunnel is used to examine the effect of chordwise foil flexibility in the dynamical features of flapping-based propulsion. We compare the regime transitions in the wake with respect to the case of a rigid foil and show that foil flexibility inhibits the symmetry breaking of the reverse Bénard–von Kármán wake reported in the literature. A momentum balance calculation shows the average thrust to be up to three times greater for the flexible foil than for the rigid foil. We explain both of these observations by analysing the vortex dynamics in the very near wake.

Near wake vortex dynamics of a hovering hawkmoth

2008 ◽  
Vol 25 (1) ◽  
pp. 23-36 ◽  
Author(s):  
Hikaru Aono ◽  
Wei Shyy ◽  
Hao Liu
Keyword(s):  
Vortex Dynamics ◽  
Wake Vortex ◽  
Near Wake

Wake of a Vibrating Cylinder at Re = 105

2011 ◽  
Author(s):  
R. D. Blevins ◽  
Jean-Franc¸ois Saint-Marcoux
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Flow Visualization ◽  
Vortex Dynamics ◽  
Velocity Profiles ◽  
Near Wake ◽  
Vortex Induced Vibration ◽  
Cylinder Flow

Measurements have been made of the wake of a circular cylinder at Reynolds number of 105 for a stationary cylinder and a cylinder vibrating +/− 1.25 diameters under natural vortex induced vibration. Wake velocity profiles were taken at 2, 4, 6, 12, 24 and 50 diameters downstream. The stationary cylinder profile reproduces the well known wake deficit law. The vibrating cylinder near wake is wider, deeper and flatter than that of the stationary cylinder. Flow visualization reveals the vortex dynamics in the wake. Correlation is shown with theory.

Optimal vortex formation in a self-propelled vehicle

2013 ◽  
Vol 737 ◽  
pp. 78-104 ◽  
Author(s):  
Robert W. Whittlesey ◽  
John O. Dabiri
Keyword(s):  
Vortex Ring ◽  
Vortex Dynamics ◽  
Vortex Formation ◽  
Vortex Rings ◽  
Near Wake ◽  
Propulsive Efficiency ◽  
Physical Size ◽  
Coherent Vortex

AbstractPrevious studies have shown that the formation of coherent vortex rings in the near-wake of a self-propelled vehicle can increase propulsive efficiency compared with a steady jet wake. The present study utilizes a self-propelled vehicle to explore the dependence of propulsive efficiency on the vortex ring characteristics. The maximum propulsive efficiency was observed to occur when vortex rings were formed of the largest physical size, just before the leading vortex ring would pinch off from its trailing jet. These experiments demonstrate the importance of vortex ring pinch off in self-propelled vehicles, where coflow modifies the vortex dynamics.

Vortex Dynamics in the Turbulent Wake of a Single Step Cylinder

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
C. Morton ◽  
S. Yarusevych
Keyword(s):  
Vortex Dynamics ◽  
Turbulent Wake ◽  
Single Step ◽  
Cylinder Wake ◽  
Near Wake ◽  
Vortex Interactions ◽  
Direct Cross ◽  
Half Loop ◽  
Turbulent Vortex Shedding ◽  
Different Diameters

The turbulent wake development of a circular cylinder with a single stepwise discontinuity in diameter was investigated experimentally using flow visualization and two-component Laser Doppler Velocimetry (LDV). A single step cylinder is comprised of two cylinders of different diameters (D and d). Experiments were performed at a Reynolds number (ReD) of 1050 and a diameter ratio (D/d) of two. A combination of hydrogen bubble and laser induced fluorescence techniques allowed visualization of complex vortex dynamics in the near wake. The results show that turbulent vortex shedding from a single step cylinder occurs in three distinct cells of constant shedding frequency. The differences in frequency and strengths between vortices in the cells lead to complex vortex interactions at the cell boundaries. The results demonstrate that vortex splitting, half-loop vortex connections, and direct cross-boundary vortex connections occur near the cell boundaries. A comparative analysis of flow visualizations and velocity measurements is used to characterize the main vortex cells and the attendant vortex interactions, producing a simplified model of vortex dynamics in the step cylinder wake for ReD = 1050 and D/d = 2.

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