Hovering flight mechanics of neotropical flower bats (Phyllostomidae:Glossophaginae) in normodense and hypodense gas mixtures

2002 ◽  
Vol 205 (23) ◽  
pp. 3669-3677 ◽  
Author(s):  
Robert Dudley ◽  
York Winter
Keyword(s):  
Drag Coefficient ◽  
Supplemental Oxygen ◽  
Gas Mixtures ◽  
Flight Mechanics ◽  
Mechanical Power ◽  
Total Power ◽  
Specific Power ◽  
Wingbeat Frequency ◽  
Hovering Flight ◽  
Power Expenditure

SUMMARYExisting estimates of flight energetics in glossophagine flower bats, the heaviest hovering vertebrate taxon, suggest disproportionately high expenditure of mechanical power. We determined wingbeat kinematics and mechanical power expenditure for one of the largest flower bats(Leptonycteris curasoae Martinez and Villa) during hovering flight in normodense and hypodense gas mixtures. Additional experiments examined the effects of supplemental oxygen availability on maximum flight performance. Bats failed to sustain hovering flight at normoxic air densities averaging 63%that of normodense air. Kinematic responses to hypodense aerodynamic challenge involved increases in wing positional angles and in total stroke amplitude;wingbeat frequency was unchanged. At near-failure air densities, total power expenditure assuming perfect elastic energy storage was 17-42% greater than that for hovering in normodense air, depending on the assumed value for the profile drag coefficient. Assuming a flight muscle ratio of 26%, the associated muscle-mass-specific power output at the point of near-failure varied between 90.8 W kg-1 (profile drag coefficient of 0.02) to 175.6 W kg-1 (profile drag coefficient of 0.2). Hyperoxia did not enhance hovering performance in hypodense air, and, with the exception of a small increase (10%) in stroke plane angle, yielded no significant change in any of the kinematic parameters studied. Revised energetic estimates suggest that mechanical power expenditure of hovering glossophagines is comparable with that in slow forward flight.

Lift and power requirements of hovering flight inDrosophila virilis

2002 ◽  
Vol 205 (16) ◽  
pp. 2413-2427 ◽  
Author(s):  
Mao Sun ◽  
Jian Tang
Keyword(s):  
Flight Control ◽  
Stokes Equations ◽  
Fruit Fly ◽  
The Body ◽  
Drosophila Virilis ◽  
Specific Power ◽  
Aerodynamic Forces ◽  
Hovering Flight ◽  
Power Expenditure ◽  
The Mean

SUMMARYThe lift and power requirements for hovering flight in Drosophila virilis were studied using the method of computational fluid dynamics. The Navier-Stokes equations were solved numerically. The solution provided the flow velocity and pressure fields, from which the unsteady aerodynamic forces and moments were obtained. The inertial torques due to the acceleration of the wing mass were computed analytically. On the basis of the aerodynamic forces and moments and the inertial torques, the lift and power requirements for hovering flight were obtained.For the fruit fly Drosophila virilis in hovering flight (with symmetrical rotation), a midstroke angle of attack of approximately 37°was needed for the mean lift to balance the insect weight, which agreed with observations. The mean drag on the wings over an up- or downstroke was approximately 1.27 times the mean lift or insect weight (i.e. the wings of this tiny insect must overcome a drag that is approximately 27 % larger than its weight to produce a lift equal to its weight). The body-mass-specific power was 28.7 W kg-1, the muscle-mass-specific power was 95.7 W kg-1 and the muscle efficiency was 17 %.With advanced rotation, larger lift was produced than with symmetrical rotation, but it was more energy-demanding, i.e. the power required per unit lift was much larger. With delayed rotation, much less lift was produced than with symmetrical rotation at almost the same power expenditure; again, the power required per unit lift was much larger. On the basis of the calculated results for power expenditure, symmetrical rotation should be used for balanced, long-duration flight and advanced rotation and delayed rotation should be used for flight control and manoeuvring. This agrees with observations.

A Comparison of Mechanical and Energetic Estimates of Flight Cost for Hovering Sphinx Moths

1981 ◽  
Vol 91 (1) ◽  
pp. 117-129 ◽  
Author(s):  
TIMOTHY M. CASEY
Keyword(s):  
Body Mass ◽  
Power Output ◽  
Power Input ◽  
Flight Mechanics ◽  
Mechanical Power ◽  
Specific Power ◽  
Power Requirement ◽  
Power Cost ◽  
Mechanical Power Output ◽  
Specific Power Input

Mechanical power output, based on measured power input, is compared with calculated values for aerodynamic and inertial power output in sphinx moths ranging from 350 to 3400 mg. Aerodynamic power output, calculated from momentum and blade-element aerodynamic theories, scales with the 1.08 power of body mass, amounting to about 40% of the mechanical power output of large moths to about 15% in the smallest individuals. Calculated value for the inertial power cost of hovering represents a larger fraction of the mechanical power output than the aerodynamic cost in all moths, with the value increasing as body mass decreases. Independent estimates of inertial power output based on metabolic data are similar to those obtained from calculations of the moment of inertia for the wings. These data suggest that inertial power output represents the largest power requirement for hovering sphinx moths, and that elastic torques do not significantly reduce the mechanical power output. Higher mass-specific power input of small sphinx moths appears to be the result of greater mass-specific inertial power requirements. Estimates of flight cost based on morphology and flight mechanics of sphinx moths yield values for mechanical power output which are similar to values estimated from their flight metabolism.

Extraordinary flight performance of orchid bees (Apidae: Euglossini) hovering in heliox (80% He/20% O2)

1995 ◽  
Vol 198 (4) ◽  
pp. 1065-1070 ◽  
Author(s):  
R Dudley
Keyword(s):  
Power Output ◽  
Insect Flight ◽  
Aerodynamic Force ◽  
Full Range ◽  
Reynolds Numbers ◽  
Gas Mixtures ◽  
Variable Density ◽  
Flight Mechanics ◽  
Specific Power ◽  
Flight Performance

Limits to insect flight performance are difficult to evaluate because the full range of aerodynamic capabilities cannot be easily elicited or controlled. Invasive experimental manipulations, such as tethering and weight addition, may adversely affect the biomechanics of the flight system as a whole. Because air density is a major determinant of aerodynamic force production, gas mixtures of variable density can be used to investigate insect flight performance non-invasively. Three species of orchid bee hovering in heliox (80 % He/20 % O2) exhibited dramatic increases in lift and power output relative to flight in normal air. Stroke amplitude increased significantly in heliox, while wingbeat frequency was unchanged; the Reynolds numbers of the wings decreased on average by 41 %. Although lift performance of airfoils generally degrades at lower Reynolds numbers, mean lift coefficients in heliox increased significantly relative to values for hovering in normal air. Mean muscle mass-specific power output for flight in heliox mixtures ranged from 130 to 160 W kg-1, substantially exceeding values determined from isolated asynchronous muscle preparations as well as limits postulated from the results of load-lifting experiments. The use of variable-density gas mixtures to examine animal flight performance is a simple yet powerful manipulation that will permit a new evaluation of both insect and vertebrate flight mechanics.

Limits to flight energetics of hummingbirds hovering in hypodense and hypoxic gas mixtures.

1996 ◽  
Vol 199 (10) ◽  
pp. 2285-2295 ◽  
Author(s):  
P Chai ◽  
R Dudley
Keyword(s):  
Sea Level ◽  
Gas Mixtures ◽  
Oxygen Availability ◽  
Flight Mechanics ◽  
Oxygen Storage ◽  
Flight Performance ◽  
Hovering Flight ◽  
Helium Mixtures ◽  
Hypoxic Tolerance ◽  
Mechanical Power Output

Hovering hummingbirds offer a model locomotor system for which analyses of both metabolism and flight mechanics are experimentally tractable. Because hummingbirds exhibit the highest mass-specific metabolic rates among vertebrates, maximum performance of hovering flight represents the upper limit of aerobic locomotion in vertebrates. This study evaluates the potential constraints of flight mechanics and oxygen availability on maximum flight performance. Hummingbird flight performance was manipulated non-invasively using air and gas mixtures which influenced metabolism via variable oxygen partial pressure and/or altered flight mechanics via variable air densities. Limits to the locomotor capacity of hovering ruby-throated hummingbirds (Archilochus colubris) were unequivocally indicated by aerodynamic failure in either air/helium or air/heliox mixtures. Air/helium mixtures are hypodense and hypoxic; failure to sustain hovering flight occurred at 63% of the density of sea-level air and at an oxygen concentration of 12%. Air/heliox mixtures are hypodense but normoxic; failure in hovering occurred at 47% of sea-level air density. Thus, hummingbirds demonstrated considerable power reserves in hovering flight as well as hypoxic tolerance. In air/helium mixtures, hovering was limited by oxygen supply and not by flight mechanics. Birds hovering in air/helium mixtures increased their mechanical power output but not their rate of oxygen consumption. By contrast, birds hovering in air/heliox mixtures increased both mechanical performance and metabolic expenditure. Under hypoxia, hovering hummingbirds demonstrated non-negligible, but still limited, capacities for anaerobic metabolism and/or oxygen storage. Depending on the physical context, hummingbird flight performance can therefore be limited by oxygen availability or by flight aerodynamics.

Animal flight mechanics in physically variable gas mixtures

1996 ◽  
Vol 199 (9) ◽  
pp. 1881-1885
Author(s):  
R Dudley ◽  
P Chai
Keyword(s):  
Empirical Studies ◽  
Gas Mixtures ◽  
Flight Mechanics ◽  
Mechanical Power ◽  
Atmospheric Composition ◽  
Air Density ◽  
Experimental Alteration ◽  
Mechanical Power Output ◽  
Initial Evolution ◽  
Animal Flight

Empirical studies of animal flight performance have generally been implemented within the contemporary atmosphere. Experimental alteration of the physical composition of gas mixtures, however, permits construction of novel flight media and the non-invasive manipulation of flight biomechanics. For example, replacement of atmospheric nitrogen with various noble gases results in a tenfold variation in air density at a constant oxygen concentration. Such variation in air density correspondingly elicits extraordinary biomechanical effort from flying animals; hummingbirds and euglossine orchid bees hovering in such low-density but normoxic mixtures have demonstrated exceptionally high values for the mechanical power output of aerobic flight muscle. As with mechanical power, lift coefficients during hovering increase at low air densities in spite of a concomitant decline in the Reynolds number of the wings. The physical effects of variable gas density may also be manifest in morphological and physiological adaptations of animals to flight across altitudinal gradients. Global variation in atmospheric composition during the late Paleozoic may also have influenced the initial evolution and subsequent diversification of ancestral pterygotes. For the present-day experimenter, the use of physically variable flight media represents a versatile opportunity to explore the range of kinematic and aerodynamic modulation available to flying animals.

A New Approach to Animal Flight Mechanics

1979 ◽  
Vol 80 (1) ◽  
pp. 17-54 ◽  
Author(s):  
J. M. V. RAYNER
Keyword(s):  
Body Mass ◽  
Large Body ◽  
Simple Expression ◽  
The Body ◽  
Flight Mechanics ◽  
Total Power ◽  
Forward Flight ◽  
Vortex Theory ◽  
Rate Of Increase ◽  
Total Power Consumption

The mechanics of lift and thrust generation by flying animals are studied by considering the distribution of vorticity in the wake. As wake generation is not continuous, the momentum jet theory, which has previously been used, is not satisfactory, and the vortex theory is a more realistic model. The vorticity shed by the wings in the course of each powered stroke deforms into a small-cored vortex ring; the wake is a chain of such rings. The momentum of each ring sustains and propels the animal; induced power is calculated as the rate of increase of wake kinetic energy. A further advantage of the vortex theory is that lift and induced drag coefficients are not required; estimated instantaneous values of these coefficients are generally too large for steady state aerodynamic theory to be appropriate to natural flapping flight. The vortex theory is applied to hovering of insects and to avian forward flight. A simple expression for induced power in hovering is found. Induced power is always greater than simple momentum jet estimates, and the discrepancy becomes substantial as body mass increases. In hovering the wake is composed of a stack of horizontal, coaxial, circular vortex rings. In forward flight of birds the rings are elliptic; they are neither horizontal nor coaxial because the momentum of each ring balances the vector sum of parasite and profile drag and the bird's weight. Total power consumption as a function of flight velocity is calculated and compared for several species. Power reduction is one of the major factors influencing the choice of flight style. A large body of data is used to obtain an approximate scaling between stroke period and the body mass for birds. Together with relations between other morphological parameters, this is used to estimate the variation of flight speed and power with body mass for birds, and on this basis deviations from allometric scaling can be related to flight proficiency and to the use of such strategies as the bounding flight of small passerines. Note: Present address: Department of Zoology, University of Bristol, Woodland Road, Bristol BS8 IUG, U.K.

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.

Thermodynamic Assessment of Hybrid PSOFC/GT Systems for Mechanical/Electric Power Generation

2000 ◽  
Author(s):  
K. K. Botros ◽  
G. R. Price ◽  
R. Parker
Keyword(s):  
Power Generation ◽  
Electric Power ◽  
Gas Turbine ◽  
Life Cycle Cost ◽  
Pressure Ratio ◽  
Pollutant Emissions ◽  
Mechanical Power ◽  
Total Power ◽  
Specific Work ◽  
System Pressure

Hybrid PSOFC/GT cycles consisting of pressurized solid oxide fuel cells integrated into gas turbine cycles are emerging as a major new power generation concept. These hybrid cycles can potentially offer thermal efficiencies exceeding 70% along with significant reductions in greenhouse gas and NOX emissions. This paper considers the PSOFC/GT cycle in terms of electrical and mechanical power generation with particular focus on gas pipeline companies interested in diversifying their assets into distributed electric generation or lowering pollutant emissions while more efficiently transporting natural gas. By replacing the conventional GT combustion chamber with an internally reformed PSOFC, electrical power is generated as a by-product while hot gases exiting the fuel cell are diverted into the gas turbine for mechanical power. A simple one-dimensional thermodynamic model of a generic PSOFC/GT cycle has shown that overall thermal efficiencies of 65% are attainable, whilst almost tripling the specific work (i.e. energy per unit mass of air). The main finding of this paper is that the amount of electric power generated ranges from 60–80% of the total power available depending on factors such as the system pressure ratio and degree of supplementary firing before the gas turbine. Ultimately, the best cycle should be based on the “balance of plant”, which considers factors such as life cycle cost analysis, business and market focus, and environmental emission issues.

scholarly journals The crouching of the shrew: Mechanical consequences of limb posture in small mammals

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2131 ◽  
Author(s):  
Daniel K. Riskin ◽  
Corinne J. Kendall ◽  
John W. Hermanson
Keyword(s):  
Small Mammals ◽  
The Body ◽  
Mechanical Power ◽  
Total Power ◽  
Blarina Brevicauda ◽  
Important Trend ◽  
Limb Posture ◽  
Evolution Of Mammals ◽  
The Cost ◽  
Kinetics Of

An important trend in the early evolution of mammals was the shift from a sprawling stance, whereby the legs are held in a more abducted position, to a parasagittal one, in which the legs extend more downward. After that transition, many mammals shifted from a crouching stance to a more upright one. It is hypothesized that one consequence of these transitions was a decrease in the total mechanical power required for locomotion, because side-to-side accelerations of the body have become smaller, and thus less costly with changes in limb orientation. To test this hypothesis we compared the kinetics of locomotion in two mammals of body size close to those of early mammals (< 40 g), both with parasagittally oriented limbs: a crouching shrew (Blarina brevicauda; 5 animals, 17 trials) and a more upright vole (Microtus pennsylvanicus; 4 animals, 22 trials). As predicted, voles used less mechanical power per unit body mass to perform steady locomotion than shrews did (P= 0.03). However, while lateral forces were indeed smaller in voles (15.6 ± 2.0% body weight) than in shrews (26.4 ± 10.9%;P= 0.046), the power used to move the body from side-to-side was negligible, making up less than 5% of total power in both shrews and voles. The most power consumed for both species was that used to accelerate the body in the direction of travel, and this was much larger for shrews than for voles (P= 0.01). We conclude that side-to-side accelerations are negligible for small mammals–whether crouching or more upright–compared to their sprawling ancestors, and that a more upright posture further decreases the cost of locomotion compared to crouching by helping to maintain the body’s momentum in the direction of travel.

Neuro-Muscular Control of Dipteran Flight

1967 ◽  
Vol 47 (1) ◽  
pp. 77-97 ◽  
Author(s):  
WERNER NACHTIGALL ◽  
DONALD M. WILSON
Keyword(s):  
The Body ◽  
Total Power ◽  
Impulse Frequency ◽  
Wingbeat Frequency ◽  
Air Stream ◽  
Separate Control ◽  
Turning Behaviour ◽  
Frequency Changes ◽  
Distribution Of Power ◽  
Two Sides

1. Electrical activity from the indirect, myogenic muscles of calliphorid flies was recorded during flight. The animals were suspended from an aerodynamic balance in the laminar air-stream from a wind-tunnel. Muscle action potentials, recorded with 25µ wire, were 5-7 msec. in duration, up to 10mV. in amplitude and positive in sign. Frequencies were mostly under 20/sec. 2. Frequencies in all the indirect muscles were similar, but these varied together with changes in aerodynamic power. 3. Frequencies in the indirect muscles of the two sides varied by no more than ± 10% during extreme turns to right or left (only left or only right wing beating). 4. Electrical records from the non-myogenic direct muscles were made during tethered flight. The potentials were 2-4 msec. in duration, up to 2 mV. positive and had frequencies up to 180/sec. 5. A nearly linear positive correlation exists between impulse frequency in the musculus latus (pleurosternal muscle), the inward movement of the pleural wall, and the wingbeat frequency, suggesting that this muscle is the basic frequency determiner. 6. Strong turning behaviour is associated with opposed frequency changes in the pairs of antagonistic adductor and abductor muscles of the wings on the two sides of the body. 7. The musculus dorsoventralis IV (tergo-trochanteral) is activated by a short impulse burst at the beginning of flight. It apparently acts as an oscillation starter. 8. Flight initiation normally requires 30-60 msec. Usually activity begins in the musculus latus, which stiffens the thorax. Then simultaneously the myogenic muscles are activated and the ‘starter’ muscle causes a jump and the beginning of oscillation of the thorax. Then the wings are drawn gradually forward and full wingbeat amplitude develops within the first six wingbeats. Flight begins with maximal lift and wingbeat frequency and a nearly synchronous burst discharge in all the indirect muscles. 9. Power production and the transmission and distribution of power are under separate control. The myogenic indirect motor varies only in total power output, this being influenced by its own state of excitation and by a muscle-controlling wingbeat frequency. Steering is accomplished by non-myogenic direct muscles which are capable of differentially engaging the two wings with the motor.

Sign in / Sign up

Export Citation Format

Share Document