scholarly journals Tuning of Strouhal number for high propulsive efficiency accurately predicts how wingbeat frequency and stroke amplitude relate and scale with size and flight speed in birds

2004 ◽  
Vol 271 (1552) ◽  
pp. 2071-2076 ◽  
Author(s):  
Robert L. Nudds ◽  
Graham K. Taylor ◽  
Adrian L. R. Thomas
Keyword(s):  
Strouhal Number ◽  
Flight Speed ◽  
Wingbeat Frequency ◽  
Propulsive Efficiency ◽  
Stroke Amplitude

scholarly journals Kinematics Measurement and Power Requirements of Fruitflies at Various Flight Speeds

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4271
Author(s):  
Hao Jie Zhu ◽  
Mao Sun
Keyword(s):  
The Body ◽  
Flight Speed ◽  
Specific Power ◽  
Flight Performance ◽  
Wingbeat Frequency ◽  
Body Angle ◽  
Flying Insects ◽  
Speed Range ◽  
Full Speed ◽  
Stroke Amplitude

Energy expenditure is a critical characteristic in evaluating the flight performance of flying insects. To investigate how the energy cost of small-sized insects varies with flight speed, we measured the detailed wing and body kinematics in the full speed range of fruitflies and computed the aerodynamic forces and power requirements of the flies. As flight speed increases, the body angle decreases and the stroke plane angle increases; the wingbeat frequency only changes slightly; the geometrical angle of attack in the middle upstroke increases; the stroke amplitude first decreases and then increases. The mechanical power of the fruitflies at all flight speeds is dominated by aerodynamic power (inertial power is very small), and the magnitude of aerodynamic power in upstroke increases significantly at high flight speeds due to the increase of the drag and the flapping velocity of the wing. The specific power (power required for flight divided by insect weigh) changes little when the advance ratio is below about 0.45 and afterwards increases sharply. That is, the specific power varies with flight speed according to a J-shaped curve, unlike those of aircrafts, birds and large-sized insects which vary with flight speed according to a U-shaped curve.

Scaling bat wingbeat frequency and amplitude

2002 ◽  
Vol 205 (17) ◽  
pp. 2615-2626 ◽  
Author(s):  
R. D. Bullen ◽  
N. L. McKenzie
Keyword(s):  
Lower Half ◽  
Flight Speed ◽  
Simple Relationship ◽  
Wingbeat Frequency ◽  
Wing Area ◽  
High Speeds ◽  
Second Mode ◽  
Speed Range

SUMMARYWingbeat frequency (fw) and amplitude(θw) were measured for 23 species of Australian bat,representing two sub-orders and six families. Maximum values were between 4 and 13 Hz for fw, and between 90 and 150° forθ w, depending on the species. Wingbeat frequency for each species was found to vary only slightly with flight speed over the lower half of the speed range. At high speeds, frequency is almost independent of velocity. Wingbeat frequency (Hz) depends on bat mass (m, kg) and flight speed (V, ms-1) according to the equation: fw=5.54-3.068log10m-2.857log10V. This simple relationship applies to both sub-orders and to all six families of bats studied. For 21 of the 23 species, the empirical values were within 1 Hz of the model values. One species, a small molossid, also had a second mode of flight in which fw was up to 3 Hz lower for all flight speeds.The following relationship predicts wingbeat amplitude to within±15° from flight speed and wing area (SREF,m2) at all flight speeds:θ w=56.92+5.18V+16.06log10SREF. This equation is based on data up to and including speeds that require maximum wingbeat amplitude to be sustained. For most species, the maximum wingbeat amplitude was 140°.

Addition of Artificial Loads to Long-Eared Bats Plecotus Auritus: Handicapping Flight Performance

1991 ◽  
Vol 161 (1) ◽  
pp. 285-298 ◽  
Author(s):  
PATSY M. HUGHES ◽  
JEREMY M. V. RAYNER
Keyword(s):  
Total Mass ◽  
Three Dimensional ◽  
Flight Speed ◽  
Wing Loading ◽  
Wingbeat Frequency ◽  
Cost Of Transport ◽  
In Captivity ◽  
Series Of Experiments ◽  
Predicted Values ◽  
Optimal Approach

A series of experiments is described in which two brown long-eared bats Plecotus auritus Linnaeus (Chiroptera: Vespertilionidae) were flown in a 1mx1mx4.5m flight enclosure at a range of body masses (n=9 experiments for a female bat, and n = 11 for a male bat). The highest three of these masses incorporated artificial loads. Stroboscopic stereophotogrammetry was used to make three-dimensional reconstructions (n=124) of the bats' flight paths. Over the entire range of experiments, wing loading was increased by 44% for the female and 46% for the male bat. Effects arising from captivity were controlled for: experiments at certain wing loadings were repeated after a period in captivity and the response to load was found to be unaltered. Flight speed fell with total mass M or with wing loading, varying as M−0.49 in the female and M−0.42 in the male bat. Wingbeat frequency increased with total mass or wing loading, varying as M0.61 in the female and M0.44in the male bat. Hence frequency, but not speed, changed with mass in the direction predicted by aerodynamic theory. These results were used in a mathematical model to predict wingbeat amplitude, flight power and cost of transport. The model was also used to estimate the optimal flight speeds Vmr and Vmp. The model predicted that amplitude increases with load. Measurements of wingbeat amplitude did not differ significantly from the predicted values. The observed flight speed was below the predicted minimum power speed Vmp (which increases with load), and diverged further from this with progressive loading. The increase in cost of flight calculated by the model over the range of wing loadings was approximately double that which it would have been had the bats adopted the optimal approach predicted by the model. The limitations inherent in the theoretical model, and the possible constraints acting on the animals, are discussed.

scholarly journals Flight muscle power increases with strain amplitude and decreases with cycle frequency in zebra finches (Taeniopygia guttata)

2020 ◽  
Vol 223 (21) ◽  
pp. jeb225839 ◽  
Author(s):  
Joseph W. Bahlman ◽  
Vikram B. Baliga ◽  
Douglas L. Altshuler
Keyword(s):  
Strain Amplitude ◽  
Power Output ◽  
Muscle Power ◽  
Aerodynamic Force ◽  
Taeniopygia Guttata ◽  
Zebra Finches ◽  
Kinematic Parameters ◽  
Wingbeat Frequency ◽  
Cycle Frequency ◽  
Stroke Amplitude

ABSTRACTBirds that use high flapping frequencies can modulate aerodynamic force by varying wing velocity, which is primarily a function of stroke amplitude and wingbeat frequency. Previous measurements from zebra finches (Taeniopygia guttata) flying across a range of speeds in a wind tunnel demonstrate that although the birds modulated both wingbeat kinematic parameters, they exhibited greater changes in stroke amplitude. These two kinematic parameters contribute equally to aerodynamic force, so the preference for modulating amplitude over frequency may instead derive from limitations of muscle physiology at high frequency. We tested this hypothesis by developing a novel in situ work loop approach to measure muscle force and power output from the whole pectoralis major of zebra finches. This method allowed for multiple measurements over several hours without significant degradation in muscle power. We explored the parameter space of stimulus, strain amplitude and cycle frequencies measured previously from zebra finches, which revealed overall high net power output of the muscle, despite substantial levels of counter-productive power during muscle lengthening. We directly compared how changes to muscle shortening velocity via strain amplitude and cycle frequency affected muscle power. Increases in strain amplitude led to increased power output during shortening with little to no change in power output during lengthening. In contrast, increases in cycle frequency did not lead to increased power during shortening but instead increased counter-productive power during lengthening. These results demonstrate why at high wingbeat frequency, increasing wing stroke amplitude could be a more effective mechanism to cope with increased aerodynamic demands.

scholarly journals Foraging in an unsteady world: bumblebee flight performance in field-realistic turbulence

2017 ◽  
Vol 7 (1) ◽  
pp. 20160086 ◽  
Author(s):  
J. D. Crall ◽  
J. J. Chang ◽  
R. L. Oppenheimer ◽  
S. A. Combes
Keyword(s):  
Field Experiments ◽  
Insect Flight ◽  
Energetic Cost ◽  
Natural Environments ◽  
Flight Performance ◽  
Wingbeat Frequency ◽  
Wind Speeds ◽  
Wide Range ◽  
Outdoor Environments ◽  
Stroke Amplitude

Natural environments are characterized by variable wind that can pose significant challenges for flying animals and robots. However, our understanding of the flow conditions that animals experience outdoors and how these impact flight performance remains limited. Here, we combine laboratory and field experiments to characterize wind conditions encountered by foraging bumblebees in outdoor environments and test the effects of these conditions on flight. We used radio-frequency tags to track foraging activity of uniquely identified bumblebee ( Bombus impatiens ) workers, while simultaneously recording local wind flows. Despite being subjected to a wide range of speeds and turbulence intensities, we find that bees do not avoid foraging in windy conditions. We then examined the impacts of turbulence on bumblebee flight in a wind tunnel. Rolling instabilities increased in turbulence, but only at higher wind speeds. Bees displayed higher mean wingbeat frequency and stroke amplitude in these conditions, as well as increased asymmetry in stroke amplitude—suggesting that bees employ an array of active responses to enable flight in turbulence, which may increase the energetic cost of flight. Our results provide the first direct evidence that moderate, environmentally relevant turbulence affects insect flight performance, and suggest that flying insects use diverse mechanisms to cope with these instabilities.

scholarly journals Kinematic Analysis of Symmetrical Flight Manoeuvres of Odonata

1989 ◽  
Vol 144 (1) ◽  
pp. 13-42 ◽  
Author(s):  
G. RÜPPELL
Keyword(s):  
Slow Motion ◽  
Free Flight ◽  
Wingbeat Frequency ◽  
Flight Velocity ◽  
Flight Parameters ◽  
Advance Ratio ◽  
Range Of Variation ◽  
Stroke Amplitude ◽  
Better Than ◽  
Phase Relationships

By analysis of slow-motion films of dragonflies and damselflies in free flight, released in front of a backdrop or startled during flight, the following flight parameters have been quantified for symmetrical manoeuvres: wingbeat frequency, relative durations of up- and downstroke, phase relationships of the beats of fore- and hindwings, stroke amplitude, mean stroke velocity, flight velocity, nondimensional flight velocity, advance ratio, acceleration, angle of attack and stroke plane. The wingbeat frequencies are higher in the smaller species and in those with relatively large wing loading. As a rule, Zygoptera have a wingbeat frequency only half that of Anisoptera. The stroke amplitude is almost always much larger in Zygoptera than in Anisoptera, which have a greater range of variation in this respect. Stroke velocity is higher in Anisoptera than in Zygoptera; it is also higher in the more elaborate flight manoeuvres than in others. The calculated stroke velocities resemble those actually measured. Anisoptera fly more rapidly than Zygoptera. With respect to the nondimensional flight velocities, it is notable that although the values for Anisoptera are higher than those for Zygoptera, they are exceeded by the Calopterygidae; the latter can fold their wings back during rapid forward flight and shoot away, as in the ‘ballistic’ flight of small songbirds. However, the advance ratio is higher in Anisoptera than in Calopterygidae. Anisoptera also perform better than Zygoptera with respect to acceleration. Three categories of phase relationships between the beats of the fore- and hindwings are established: counterstroking, phase-shifted stroking and parallel stroking. Counterstroking produces uniform flight, whereas the flight produced by phase-shifted and, in particular, parallel stroking is irregular. The angles of attack of the wings are shown to be associated with particular flight manoeuvres, as are the stroke planes. Flight manoeuvres are discussed without drawing detailed aerodynamic conclusions. The flight of Anisoptera is compared with that of Zygoptera.

scholarly journals Neuromuscular control and kinematics of intermittent flight in the European starling (Sturnus vulgaris)

1995 ◽  
Vol 198 (6) ◽  
pp. 1259-1273 ◽  
Author(s):  
B Tobalske
Keyword(s):  
Power Output ◽  
Neuromuscular Control ◽  
Sturnus Vulgaris ◽  
Flight Speed ◽  
Cycle Duration ◽  
Mean Power ◽  
Wingbeat Frequency ◽  
Pull Out ◽  
Emg Signal ◽  
All Speeds

Electromyographic (EMG) and kinematic data were collected from European starlings (Sturnus vulgaris) flying at a range of speeds from 8 to 18 m s-1 in a variable-speed windtunnel. Their flight at all speeds consisted of alternating flapping and non-flapping phases. Wing postures during non-flapping phases included glides, partial-bounds and bounds. Glides were performed proportionally more often within each speed and were longer in duration than either of the other two non-flapping postures, but the percentage of bounds increased markedly with increasing flight speed. The shift from flap-gliding at slow speeds towards flap-bounding at fast speeds was consistent with reducing mean power output relative to continuous flapping. The starlings often combined more than one non-flapping posture within a single non-flapping period. Transitions between non-flapping postures, as well as transitions between bounds and subsequent flapping, were classified as 'pull-outs'. Pull-outs consisted of an increase in wingspan but no change in wingtip elevation. The pectoralis and supracoracoideus exhibited electrical activity during glides but not during bounds. The scapulohumeralis caudalis was not active during glides, but this muscle and the supracoracoideus were typically active during partial-bounds and pull-out phases. The scapulohumeralis caudalis occasionally showed activity during bounds, which may reflect its role as a humeral retractor. The frequency and duration of non-flapping intervals in starlings were less during EMG experiments than during non-implanted flights. During flapping phases, relative intensity and duration of EMG signal and wingbeat frequency increased with flight speed, whereas flapping or non-flapping cycle duration, the percentage of a cycle spent flapping and the number of wingbeats in a cycle were all greatest at 8 m s-1. Wingbeat amplitude was smaller at intermediate speeds, but differences among speeds were not significant. These variables allowed indirect estimates of power output and suggested that minimum power speed for starlings was near 12 m s-1 and that power output increased at both slower and faster speeds. Within windtunnel speeds, muscle activity changed in relation to wingspan at mid-upstroke, wingtip excursion, wingbeat frequency, acceleration, velocity, altitude and horizontal position.

scholarly journals How body torque and Strouhal number change with swimming speed and developmental stage in larval zebrafish

2015 ◽  
Vol 12 (110) ◽  
pp. 20150479 ◽  
Author(s):  
Johan L. van Leeuwen ◽  
Cees J. Voesenek ◽  
Ulrike K. Müller
Keyword(s):  
Strouhal Number ◽  
Swimming Speed ◽  
Inverse Dynamics ◽  
Larval Fish ◽  
Beat Frequency ◽  
Relative Effect ◽  
Viscous Drag ◽  
Propulsive Efficiency ◽  
Viscous Forces ◽  
Larval Zebrafish

Small undulatory swimmers such as larval zebrafish experience both inertial and viscous forces, the relative importance of which is indicated by the Reynolds number ( Re ). Re is proportional to swimming speed ( v swim ) and body length; faster swimming reduces the relative effect of viscous forces. Compared with adults, larval fish experience relatively high (mainly viscous) drag during cyclic swimming. To enhance thrust to an equally high level, they must employ a high product of tail-beat frequency and (peak-to-peak) amplitude fA tail , resulting in a relatively high fA tail / v swim ratio (Strouhal number, St), and implying relatively high lateral momentum shedding and low propulsive efficiency. Using kinematic and inverse-dynamics analyses, we studied cyclic swimming of larval zebrafish aged 2–5 days post-fertilization (dpf). Larvae at 4–5 dpf reach higher f (95 Hz) and A tail (2.4 mm) than at 2 dpf (80 Hz, 1.8 mm), increasing swimming speed and Re , indicating increasing muscle powers. As Re increases (60 → 1400), St (2.5 → 0.72) decreases nonlinearly towards values of large swimmers (0.2–0.6), indicating increased propulsive efficiency with v swim and age. Swimming at high St is associated with high-amplitude body torques and rotations. Low propulsive efficiencies and large yawing amplitudes are unavoidable physical constraints for small undulatory swimmers.

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