Wingbeat frequency of barn swallows and house martins: a comparison between free flight and wind tunnel experiments

2002 ◽  
Vol 205 (16) ◽  
pp. 2461-2467 ◽  
Author(s):  
Felix Liechti ◽  
Lukas Bruderer
Keyword(s):  
Wind Tunnel ◽  
Single Pulse ◽  
Free Flight ◽  
Wind Tunnel Experiments ◽  
Wingbeat Frequency ◽  
Flight Costs ◽  
Radar Echo ◽  
The Mean ◽  
Barn Swallows ◽  
Air Speed

SUMMARYThe flight paths and wingbeat patterns of 39 barn swallows (Hirundo rustica) and 26 house martins (Delichon urbica) were recorded by tracking radar during the spring migration. Depending mostly on flight angle,hirundines performed anything from continuous flapping flight during climbing to single pulse-like wing beats during descent. Unlike most other passerines,hirundines rarely showed regular flapping and rest phases, allowing them to be distinguished from other bird migrants by radar echo signatures. Effective wingbeat frequency (Feff) was calculated as the mean number of wing beats per second, including non-flapping phases. Under comparable flight conditions, Feff was higher in house martins than in barn swallows. Within species, Feff values were higher during climbing and slow flying than during descent. Of the variance in Feff, 71 % could be explained by climb rate,air speed and species; similar results were obtained in the wind tunnel. Under comparable flight conditions, barn swallows and house martins in free flight had significantly lower values of Feff than individuals in wind tunnel experiments (by 40 % and 32 %, respectively). This difference may at least partly be due to the shorter wings of the juveniles tested in the wind tunnel during autumn. However, it seems unlikely that this can account for all of the large difference. It is suggested that wind tunnel experiments might overestimate birds' flight costs compared with free flight.

Flexibility in flight behaviour of barn swallows (Hirundo rustica) and house martins (Delichon urbica) tested in a wind tunnel

2001 ◽  
Vol 204 (8) ◽  
pp. 1473-1484 ◽  
Author(s):  
L. Bruderer ◽  
F. Liechti ◽  
D. Bilo
Keyword(s):  
Wind Tunnel ◽  
Hirundo Rustica ◽  
Wingbeat Frequency ◽  
Flight Behaviour ◽  
Delichon Urbica ◽  
Gliding Flight ◽  
Mechanical Power Output ◽  
Intermittent Flight ◽  
Barn Swallows ◽  
Air Speed

The flight behaviour of barn swallows (Hirundo rustica) and house martins (Delichon urbica) was tested in a wind tunnel at 15 combinations of flight angles and speeds. In contrast to that of most other small passerines, the intermittent flight of hirundines rarely consists of regular patterns of flapping and rest phases. To vary mechanical power output, both species used intermittent flight, controlling the number of single, pulse-like wingbeats per unit time. House martins in descent tended to concentrate their wingbeats into bursts and performed true gliding flight during rest phases. Barn swallows mainly performed partial bounds during brief interruptions of upstrokes, which they progressively prolonged with decreasing flight angle. Thus, identification of distinct flapping phases to calculate wingbeat frequencies was not feasible. Instead, an effective wingbeat frequency for flight intervals of 20 s, including partial bounds, was introduced. The effective wingbeat frequencies of house martins (N=3) ranged from 2 to 10.5 s(−)(1), those of barn swallows (N=4) from 2.5 to 8.5 s(−)(1). In both hirundine species, effective wingbeat frequency was found to decrease almost linearly with decreasing flight angle. With changes in air speed, wingbeat frequency varied according to a U-shaped curve, suggesting a minimum power speed of roughly 9 m s(−)(1). The duration of the down- and upstrokes varied systematically depending on flight angle and air speed.

scholarly journals Drop Shapes and Axis Ratio Distributions: Comparison between 2D Video Disdrometer and Wind-Tunnel Measurements

2009 ◽  
Vol 26 (7) ◽  
pp. 1427-1432 ◽  
Author(s):  
M. Thurai ◽  
V. N. Bringi ◽  
M. Szakáll ◽  
S. K. Mitra ◽  
K. V. Beard ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Close Agreement ◽  
Drop Diameter ◽  
Wind Tunnel Experiments ◽  
Axis Ratio ◽  
Wind Tunnel Measurements ◽  
Mean Shape ◽  
The Mean ◽  
Ratio Versus ◽  
Made In

Abstract Comparisons of drop shapes between measurements made using 2D video disdrometer (2DVD) and wind-tunnel experiments are presented. Comparisons are made in terms of the mean drop shapes and the axis ratio distributions. Very close agreement of the mean shapes is seen between the two sets of measurements; the same applies to the mean axis ratio versus drop diameter. Also, in both sets of measurements, an increase in the oscillation amplitudes with increasing drop diameter is observed. In the case of the 2DVD, a small increase in the skewness was also detected. Given that the two sets of measurements were conducted in very different conditions, the agreement between the two sets of data implies a certain “robustness” in the mean shape of oscillating drops that may be extended to natural raindrop oscillations, at least in steady rainfall and above the surface layer.

scholarly journals Wind-Tunnel Experiments on Blowing Snow

1985 ◽  
Vol 6 ◽  
pp. 63-67 ◽  
Author(s):  
N. Maeno ◽  
R. Naruse ◽  
K. Nishimura ◽  
I. Takei ◽  
T. Ebinuma ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Pressure Gradient ◽  
Blowing Snow ◽  
Wind Tunnel Experiments ◽  
Complex Dynamic ◽  
Turbulent Diffusion Coefficient ◽  
Wide Range ◽  
The Mean ◽  
Cold Wind ◽  
Snow Drifting

Blowing snow was produced artificially in a cold wind-tunnel, and various measurements were conducted including particle diameters, concentrations, saltation lengths heat transport and electric charge. The mean diameter of blowing snow particles decreased only slightly with increasing height; in the saltation layer, standard deviation was large and velocities were scattered in a wide range, suggesting the complex dynamic process on taking-off. The mean saltation length ranged from a few cm to 40 cm increasing with wind velocity.When wind blew without snow drifting, the static air pressure on the snow surface was smaller at higher levels, the vertical pressure gradient being negative. The pressure gradient became positive when blowing snow was initiated eg +9.6 Pa/m at 11.2 m/s and -8.3 °C. The magnitude of à downward force acting on a saltating snow partice caused by the pressure gradient was not large enough to explain the downward acceleration found from photographic analyses of particle trajectories.Blowing snow particles were charged negatively the magnitude of charge increased with lowering temperature. Increase in vertical heat transfer was found in blowing snow by measuring the temperature of the air at various levels; the increase is reflected on that in the apparent turbulent diffusion coefficient.

scholarly journals Wind-Tunnel Experiments on Blowing Snow

1985 ◽  
Vol 6 ◽  
pp. 63-67 ◽  
Author(s):  
N. Maeno ◽  
R. Naruse ◽  
K. Nishimura ◽  
I. Takei ◽  
T. Ebinuma ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Pressure Gradient ◽  
Blowing Snow ◽  
Wind Tunnel Experiments ◽  
Complex Dynamic ◽  
Turbulent Diffusion Coefficient ◽  
Wide Range ◽  
The Mean ◽  
Cold Wind ◽  
Snow Drifting

Blowing snow was produced artificially in a cold wind-tunnel, and various measurements were conducted including particle diameters, concentrations, saltation lengths heat transport and electric charge. The mean diameter of blowing snow particles decreased only slightly with increasing height; in the saltation layer, standard deviation was large and velocities were scattered in a wide range, suggesting the complex dynamic process on taking-off. The mean saltation length ranged from a few cm to 40 cm increasing with wind velocity.When wind blew without snow drifting, the static air pressure on the snow surface was smaller at higher levels, the vertical pressure gradient being negative. The pressure gradient became positive when blowing snow was initiated eg +9.6 Pa/m at 11.2 m/s and -8.3 °C. The magnitude of à downward force acting on a saltating snow partice caused by the pressure gradient was not large enough to explain the downward acceleration found from photographic analyses of particle trajectories.Blowing snow particles were charged negatively the magnitude of charge increased with lowering temperature. Increase in vertical heat transfer was found in blowing snow by measuring the temperature of the air at various levels; the increase is reflected on that in the apparent turbulent diffusion coefficient.

A Kriging Approach for CFD/Wind-Tunnel Data Comparison

2005 ◽  
Vol 128 (4) ◽  
pp. 847-855 ◽  
Author(s):  
J.-C. Jouhaud ◽  
P. Sagaut ◽  
B. Labeyrie
Keyword(s):  
Wind Tunnel ◽  
Response Surface ◽  
Uncertain Parameters ◽  
Free Flight ◽  
Wind Tunnel Experiments ◽  
Data Comparison ◽  
Wind Tunnel Data ◽  
Compressible Turbulent Flow ◽  
Kriging Approach ◽  
Insight Into

A Kriging-based method for the parametrization of the response surface spanned by uncertain parameters in computational fluid dynamics is proposed. A multiresolution approach in the sampling space is used to improve the accuracy of the method. It is illustrated considering the problem of the computation of the corrections needed to recover equivalent free-flight conditions from wind-tunnel experiments. Using the surface response approach, optimal corrected values of the freestream Mach number and the angle of attack for the compressible turbulent flow around the RAE 2822 wing are computed. The use of the response surface to gain an insight into the sensitivity of the results with respect to other parameter is also assessed.

scholarly journals The splash function for snow from wind-tunnel measurements

2004 ◽  
Vol 38 ◽  
pp. 71-78 ◽  
Author(s):  
James N. McElwaine ◽  
Norikazu Maeno ◽  
Konosuke Sugiura
Keyword(s):  
Wind Tunnel ◽  
Mass Transport ◽  
Physical Properties ◽  
Wind Flow ◽  
Ejection Velocity ◽  
Wind Tunnel Experiments ◽  
Wind Tunnel Measurements ◽  
The Mean ◽  
Horizontal Momentum ◽  
Determining Factor

AbstractIn wind transport of snow, horizontal momentum is extracted from the mean wind flow and transferred to the snow grains. Upon colliding with the surface the grains can bounce and eject further grains in a process known as splashing. How efficiently the horizontal momentum is converted to vertical momentum in the splash process is the determining factor for mass-transport rates. This paper discusses wind-tunnel experiments performed to calculate the splash function for snow particles. The data are used to develop a new splash function. Particular care is taken to include correlations in the data such as between ejection velocity and ejection angle. The new splash function includes these correlations, and its parameters are related to physical properties of the bed and snow.

scholarly journals Wingbeat frequency and the body drag anomaly: wind-tunnel observations on a thrush nightingale (Luscinia luscinia) and a teal (Anas crecca)

1996 ◽  
Vol 199 (12) ◽  
pp. 2757-2765 ◽  
Author(s):  
C J Pennycuick ◽  
M Klaassen ◽  
A Kvist ◽  
Å Lindström
Keyword(s):  
Wind Tunnel ◽  
The Body ◽  
Wingbeat Frequency ◽  
Cross Sectional ◽  
Number Range ◽  
Drag Coefficients ◽  
Anas Crecca ◽  
Body Drag ◽  
Air Speed ◽  
Thrush Nightingale

A teal (Anas crecca) and a thrush nightingale (Luscinia luscinia) were trained to fly in the Lund wind tunnel for periods of up to 3 and 16 h respectively. Both birds flew in steady flapping flight, with such regularity that their wingbeat frequencies could be determined by viewing them through a shutter stroboscope. When flying at a constant air speed, the teal's wingbeat frequency varied with the 0.364 power of the body mass and the thrush nightingale's varied with the 0.430 power. Both exponents differed from zero, but neither differed from the predicted value (0.5) at the 1 % level of significance. The teal continued to flap steadily as the tunnel tilt angle was varied from -1 ° (climb) to +6 ° (descent), while the wingbeat frequency declined progressively by about 11 %. In both birds, the plot of wingbeat frequency against air speed in level flight was U-shaped, with small but statistically significant curvature. We identified the minima of these curves with the minimum power speed (Vmp) and found that the values predicted for Vmp, using previously published default values for the required variables, were only about two-thirds of the observed minimum-frequency speeds. The discrepancy could be resolved if the body drag coefficients (CDb) of both birds were near 0.08, rather than near 0.40 as previously assumed. The previously published high values for body drag coefficients were derived from wind-tunnel measurements on frozen bird bodies, from which the wings had been removed, and had long been regarded as anomalous, as values below 0.01 are given in the engineering literature for streamlined bodies. We suggest that birds of any size that have well-streamlined bodies can achieve minimum body drag coefficients of around 0.05 if the feet can be fully retracted under the flank feathers. In such birds, field observations of flight speeds may need to be reinterpreted in the light of higher estimates of Vmp. Estimates of the effective lift:drag ratio and range can also be revised upwards. Birds that have large feet or trailing legs may have higher body drag coefficients. The original estimates of around CDb=0.4 could be correct for species, such as pelicans and large herons, that also have prominent heads. We see no evidence for any progressive reduction of body drag coefficient in the Reynolds number range covered by our experiments, that is 21 600­215 000 on the basis of body cross-sectional diameter.

Repeatability of free-burning fire experiments using heterogeneous forest fuel beds in a combustion wind tunnel

2016 ◽  
Vol 25 (4) ◽  
pp. 445 ◽  
Author(s):  
Joshua J. Mulvaney ◽  
Andrew L. Sullivan ◽  
Geoffrey J. Cary ◽  
Glenys R. Bishop
Keyword(s):  
Wind Tunnel ◽  
Solid Phase ◽  
Large Degree ◽  
Fuel Load ◽  
Forward Rate ◽  
Fuel Particle ◽  
Residual Variance ◽  
Fuel Type ◽  
Wind Tunnel Experiments ◽  
Air Speed

Combustion wind tunnels are often used to investigate the propagation of free-moving fires through solid-phase fuels, typically standardised ‘artificial’ fuel beds. However, the results of such studies are difficult to apply directly to wildland fire situations primarily due to the disparity between the generally uniform artificial fuel and the heterogeneous fuel found in nature. To explore the feasibility of using heterogeneous ‘natural’ fuel beds in subsequent combustion wind tunnel experiments, this study quantified the variability in forward rate of fire spread resulting from the use of heterogeneous fuel beds in a combustion wind tunnel under a given set of burning conditions. The experiment assessed the effects of fuel type and air speed, and controlled for the effects of fuel moisture content, fuel load and fuel particle size. It was found that the variability in rate of spread increased with its mean, but the overall residual variance (σ2e <0.025, s.e. 0.011) was low compared with the effects of air speed and fuel type. This demonstrates that heterogeneous fuel beds can be used in combustion wind tunnel experiments without introducing a large degree of variability.

scholarly journals The Profile Drag of a Hawk'S Wing, Measured by Wake Sampling in a Wind Tunnel

1992 ◽  
Vol 165 (1) ◽  
pp. 1-19 ◽  
Author(s):  
C. J. PENNYCUICK ◽  
CARLTON E. HEINE ◽  
SEAN J. KIRKPATRICK ◽  
MARK R. FULLER
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Dynamic Pressure ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Wing Profile ◽  
The Mean ◽  
Air Speed ◽  
University Of Bristol

The distribution of dynamic pressure behind a Harris' hawk's wing was sampled using a wake rake consisting of 15 pitot tubes and one static tube. The hawk was holding on to a perch, but at an air speed and gliding angle at which it was capable of gliding. The perch was instrumented, so that the lift developed by the wing was known and the lift coefficient could be calculated. The mean of 92 estimates of profile drag coefficient was 0.0207, with standard deviation 0.0079. Lift coefficients ranged from 0.51 to 1.08. Reynolds numbers were nearly all in the range 143000–194000. The estimates of profile drag coefficient were reconcilable with previous estimates of the wing profile drag of the same bird, obtained by the subtractive method, and also with values predicted by the ‘Airfoil-ii’ program for designing aerofoils, based on a digitized wing profile from the ulnar region of the wing. The thickness of the wake suggested that the boundary layer was mostly or fully turbulent in most observations and separated in some, possibly as an active means of creating drag for control purposes. It appears that the bird could momentarily either increase or decrease the profile drag of specific parts of the wing, by active changes of shape, and it appeared to use the carpo-metacarpal region especially for such control movements. Further investigation in a low turbulence wind tunnel would help to resolve doubts about the possible influence of airstream turbulence on the behaviour of the boundary layer. Note: Present address: Department of Zoology, University of Bristol, Woodland Road, Bristol BS8 1UG, England.

scholarly journals Measurements of Unsteady Periodic Forces generated by the Blowfly Flying in a Wind Tunnel

1981 ◽  
Vol 90 (1) ◽  
pp. 163-173
Author(s):  
RICHARD H. BUCKHOLZ
Keyword(s):  
Wind Tunnel ◽  
Vertical Force ◽  
Free Flight ◽  
Wind Speeds ◽  
Sarcophaga Bullata ◽  
Drag Forces ◽  
Harmonic Content ◽  
The Mean ◽  
Lift And Drag ◽  
Force Accuracy

A technique was developed for the measurement of the instantaneous lift and drag forces generated by the blowfly, Sarcophaga bullata, flying fixed in a wind tunnel. Apparatus for the measurement of insect-generated forces was checked in part for mean force accuracy by measurement of the drag on a circular cylinder. Our experimental device detects the sum of the aerodynamic forces and wing inertial forces as experienced by the thorax. The streamwise and vertical force waveforms show a surprising lack of higher harmonic content. Wind speeds in the neighbourhood of the known preferred flying speed were used, without an explicit attempt to nullify the mean vertical and horizontal forces to simulate free flight. Several measurements of the phase angle between the force waveform and the wing beating kinematics indicated that vertical forces in the liftward direction achieved a maximum during the downstroke and thrustward forces achieved a maximum during the upstroke.

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