scholarly journals The vortex wake of blackcaps (Sylvia atricapilla L.) measured using high-speed digital particle image velocimetry (DPIV)

2009 ◽  
Vol 212 (20) ◽  
pp. 3365-3376 ◽  
Author(s):  
L. C. Johansson ◽  
A. Hedenstrom
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
Digital Particle Image Velocimetry ◽  
Vortex Wake ◽  
Sylvia Atricapilla ◽  
Image Velocimetry

scholarly journals Time-resolved vortex wake of a common swift flying over a range of flight speeds

2010 ◽  
Vol 8 (59) ◽  
pp. 807-816 ◽  
Author(s):  
P. Henningsson ◽  
F. T. Muijres ◽  
A. Hedenström
Keyword(s):  
High Speed ◽  
Particle Image ◽  
Digital Particle Image Velocimetry ◽  
Transverse Plane ◽  
The Body ◽  
Vortex Wake ◽  
Vertical Force ◽  
Time Resolved ◽  
Longitudinal Plane ◽  
Image Velocimetry

The wake of a freely flying common swift ( Apus apus L.) is examined in a wind tunnel at three different flight speeds, 5.7, 7.7 and 9.9 m s −1 . The wake of the bird is visualized using high-speed stereo digital particle image velocimetry (DPIV). Wake images are recorded in the transverse plane, perpendicular to the airflow. The wake of a swift has been studied previously using DPIV and recording wake images in the longitudinal plane, parallel to the airflow. The high-speed DPIV system allows for time-resolved wake sampling and the result shows features that were not discovered in the previous study, but there was approximately a 40 per cent vertical force deficit. As the earlier study also revealed, a pair of wingtip vortices are trailing behind the wingtips, but in addition, a pair of tail vortices and a pair of ‘wing root vortices’ are found that appear to originate from the wing/body junction. The existence of wing root vortices suggests that the two wings are not acting as a single wing, but are to some extent aerodynamically detached from each other. It is proposed that this is due to the body disrupting the lift distribution over the wing by generating less lift than the wings.

scholarly journals Aerodynamics of manoeuvring flight in brown long-eared bats ( Plecotus auritus )

2018 ◽  
Vol 15 (148) ◽  
pp. 20180441 ◽  
Author(s):  
Per Henningsson ◽  
Lasse Jakobsen ◽  
Anders Hedenström
Keyword(s):  
Particle Image Velocimetry ◽  
Wind Tunnel ◽  
High Speed ◽  
Particle Image ◽  
Future Studies ◽  
Image Velocimetry ◽  
Mechanistic Basis

In this study, we explicitly examine the aerodynamics of manoeuvring flight in animals. We studied brown long-eared bats flying in a wind tunnel while performing basic sideways manoeuvres. We used particle image velocimetry in combination with high-speed filming to link aerodynamics and kinematics to understand the mechanistic basis of manoeuvres. We predicted that the bats would primarily use the downstroke to generate the asymmetries for the manoeuvre since it has been shown previously that the majority of forces are generated during this phase of the wingbeat. We found instead that the bats more often used the upstroke than they used the downstroke for this. We also found that the bats used both drag/thrust-based and lift-based asymmetries to perform the manoeuvre and that they even frequently switch between these within the course of a manoeuvre. We conclude that the bats used three main modes: lift asymmetries during downstroke, thrust/drag asymmetries during downstroke and thrust/drag asymmetries during upstroke. For future studies, we hypothesize that lift asymmetries are used for fast turns and thrust/drag for slow turns and that the choice between up- and downstroke depends on the timing of when the bat needs to generate asymmetries.

scholarly journals Dual-camera system for high-speed imaging in particle image velocimetry

2012 ◽  
Vol 15 (3) ◽  
pp. 193-195 ◽  
Author(s):  
K. Hashimoto ◽  
A. Hori ◽  
T. Hara ◽  
S. Onogi ◽  
H. Mouri
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
High Speed Imaging ◽  
Camera System ◽  
Image Velocimetry
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