scholarly journals Method to analyse the vortex structure using simultaneous spectral and flow-visualization measurements

1988 ◽  
Vol 8 (Supplement) ◽  
pp. 11-16
Author(s):  
Koichi NAKABAYASHI ◽  
Yoichi TSUCHIDA
Keyword(s):  
Flow Visualization ◽  
Vortex Structure

Experimental Analysis of Opposing Flow in Mixed Convection in a Channel With an Open Cavity Below

2005 ◽  
Author(s):  
Oronzio Manca ◽  
Sergio Nardini ◽  
Kambiz Vafai
Keyword(s):  
Reynolds Number ◽  
Mixed Convection ◽  
Flow Visualization ◽  
Vortex Structure ◽  
Open Cavity ◽  
Forced Flow ◽  
Heated Wall ◽  
Heated Plate ◽  
Thermal Plume ◽  
Recirculation Flow

In this paper mixed convection in an open cavity with a heated wall bounded by a horizontal unheated plate is investigated experimentally. The cavity has the heated wall on the opposite side of the forced inflow. The results are reported in terms of wall temperature profiles of the heated wall and flow visualization for Reynolds number (Re) from 100 to 2000 and Richardson number (Ri) in the range 4.3–6400; the ratio between the length and the height of cavity (L/D) is in the range 0.5–2.0 and the ratio between the channel and cavity height (H/D) is equal to 1.0. The present results show that at the lowest investigated Reynolds number the surface temperatures are lower than the corresponding surface temperature for Re = 2000, at same the ohmic heat flux. The flow visualization points out that for Re = 1000 there are two nearly distinct fluid motions: a parallel forced flow in the channel and a recirculation flow inside the cavity. For Re = 100 the effect of a stronger buoyancy determines a penetration of thermal plume from the heated plate wall into the upper channel. Moreover, the flow visualization points out that for lower Reynolds numbers the forced motion penetrates inside the cavity and a vortex structure is adjacent to the unheated vertical plate. At higher Reynolds number the vortex structure has a larger extension at same L/D value.

Flow visualization of vortex structure of an excited coaxial jet

2001 ◽  
Vol 4 (1) ◽  
pp. 99-107 ◽  
Author(s):  
T. Kiwata ◽  
A. Okajima ◽  
S. Kimura
Keyword(s):  
Flow Visualization ◽  
Vortex Structure

scholarly journals Structure of the vortex wake in hovering Anna's hummingbirds ( Calypte anna )

2013 ◽  
Vol 280 (1773) ◽  
pp. 20132391 ◽  
Author(s):  
M. Wolf ◽  
V. M. Ortega-Jimenez ◽  
R. Dudley
Keyword(s):  
Flow Visualization ◽  
Vortex Structure ◽  
Force Production ◽  
Vortex Rings ◽  
Vortex Wake ◽  
Secondary Vortex ◽  
Single Vortex ◽  
Discrete Vortex ◽  
Weight Support ◽  
Calypte Anna

Hummingbirds are specialized hoverers for which the vortex wake has been described as a series of single vortex rings shed primarily during the downstroke. Recent findings in bats and birds, as well as in a recent study on Anna's hummingbirds, suggest that each wing may shed a discrete vortex ring, yielding a bilaterally paired wake. Here, we describe the presence of two discrete rings in the wake of hovering Anna's hummingbirds, and also infer force production through a wingbeat with contributions to weight support. Using flow visualization, we found separate vortices at the tip and root of each wing, with 15% stronger circulation at the wingtip than at the root during the downstroke. The upstroke wake is more complex, with near-continuous shedding of vorticity, and circulation of approximately equal magnitude at tip and root. Force estimates suggest that the downstroke contributes 66% of required weight support, whereas the upstroke generates 35%. We also identified a secondary vortex structure yielding 8–26% of weight support. Lift production in Anna's hummingbirds is more evenly distributed between the stroke phases than previously estimated for Rufous hummingbirds, in accordance with the generally symmetric down- and upstrokes that characterize hovering in these birds.

scholarly journals Flow visualization of vortex structure in a pulsed rectangular jet

2008 ◽  
Vol 11 (2) ◽  
pp. 125-132 ◽  
Author(s):  
S. Iio ◽  
K. Takahashi ◽  
Y. Haneda ◽  
T. Ikeda
Keyword(s):  
Flow Visualization ◽  
Vortex Structure ◽  
Rectangular Jet

Effect of Wake Disturbance Frequency on the Secondary Flow Vortex Structure in a Turbine Blade Cascade

2000 ◽  
Vol 122 (3) ◽  
pp. 606-613 ◽  
Author(s):  
Christopher G. Murawski ◽  
Kambiz Vafai
Keyword(s):  
Flow Visualization ◽  
Secondary Flow ◽  
Turbine Blade ◽  
Vortex Structure ◽  
Leading Edge ◽  
Side Surface ◽  
Suction Side ◽  
Disturbance Frequency ◽  
Flow Frequency ◽  
Flow Vortex

An experimental study of the effect of wake disturbance frequency on the secondary flow vortices in a two-dimensional linear cascade is presented. The flow Reynolds numbers, based on exit velocity and suction side surface length were 25,000, 50,000 and 85,000. Secondary flow was visualized by injecting smoke into the boundary layer and illuminating it with a laser light sheet located at the exit of the cascade. To simulate wakes from upstream blade rows, a set of spanwise cylinders were traversed across the front of the blade row. The flow visualization results with a single wake disturbance reveal that the recovery time of the secondary flow vortex structure decreases as the wake traverse velocity is increased. The results of flow visualization with multiple wakes showed that wake disturbance frequencies below the axial chord flow frequency allowed complete recovery of the secondary flow vortex structure before the next wake encounters the blade leading edge. Wake disturbance frequencies that exceeded the axial chord flow frequency resulted in no observable recovery of the secondary flow vortex structure. Axial chord flow frequency is defined as the axial velocity in the cascade divided by the axial chord length of the turbine blade. [S0098-2202(00)02203-3]

scholarly journals Numerical simulation and flow visualization using soap film of the self-organized vortex structure in the wake of an array of cylinders

2011 ◽  
Vol 14 (4) ◽  
pp. 311-314
Author(s):  
Mohammad Rafiqul Haque ◽  
Mohamed Fayed ◽  
Amy-Lee Gunter ◽  
Othman Smadi ◽  
Lyes Kadem ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Flow Visualization ◽  
Vortex Structure ◽  
Soap Film ◽  
The Self ◽  
Self Organized ◽  
An Array Of Cylinders
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