Energetics of Hovering Flight in Hummingbirds and in Drosophila

1972 ◽  
Vol 56 (1) ◽  
pp. 79-104 ◽  
Author(s):  
TORKEL WEIS-FOGH
Keyword(s):  
Steady State ◽  
Power Output ◽  
Lift Coefficient ◽  
Bending Moment ◽  
Mechanical Efficiency ◽  
Hovering Flight ◽  
Vertical Movements ◽  
Extra Energy ◽  
Mechanical Power Output ◽  
Drag Ratio

1. Expressions have been derived for an estimate of the average coefficient of lift, for the variation in bending moment or torque caused by wind forces and by inertia forces, and for the power output during hovering flight on one spot when the wings move according to a horizontal figure-of-eight. 2. In both hummingbirds and Drosophila the flight is consistent with steady-state aerodynamics, the average lift coefficient being 1.8 in the hummingbird and 0.8 in Drosophila. 3. The aerodynamic or hydraulic efficiency is 0.5 in the hummingbird and 0.3 in Drosophila, and in both types the aerodynamic power output is 22-24 cal/g body weight/h. 4. The total mechanical power output is 39 cal g-1 h-1 in the hummingbird because of the extra energy needed to accelerate the wing-mass. It is 24 cal g-1 h-1 in Drosophila in which the inertia term is negligible because the wing-stroke frequency is reduced to the lowest possible value for sustained flight. 5. In both animals the mechanical efficiency of the flight muscles is 0.2. 6. It is argued that the tilt of the stroke plane relative to the horizontal is an adaptation to the geometrically unfavourable induced wind and to the relatively large lift/drag ratio seen in many insects. The vertical movements at the extreme ends may serve to reduce the interaction between the shed ‘stopping’ vortex and the new bound vortex of opposite sense which has to be built up during the early part of the return stroke. 7. Two additional non-steady flow situations may exist at either end of the stroke, delayed stall and delayed build-up of circulation (Wagner effect), but since they have opposite effects it is probable that the resultant force is of about the same magnitude as that estimated for a steady-state situation. 8. Most insects have an effective elastic system to counteract the adverse effect of wing-inertia, but small fast-moving vertebrates have not. It is argued that the only material available for this purpose in this group is elastin and that it is unsuited at the rates of deformation required because recent measurements have shown that the damping is relatively high, probably due to molecular factors.

Aerodynamics, kinematics, and energetics of horizontal flapping flight in the long-eared bat Plecotus auritus

1976 ◽  
Vol 65 (1) ◽  
pp. 179-212 ◽  
Author(s):  
U. M. Norberg
Keyword(s):  
Steady State ◽  
Power Output ◽  
Lift Coefficient ◽  
Mechanical Efficiency ◽  
Flapping Flight ◽  
Mechanical Power ◽  
Power Stroke ◽  
Force Coefficient ◽  
Mechanical Power Output ◽  
Lift And Drag

The kinematics, aerodynamics, and energetics of Plecotus auritus in slow horizontal flight, 2–35 m s-1, are analysed. At this speed the inclination of the stroke path is ca. 58 degrees to the horizontal, the stroke angle ca. 91 degrees, and the stroke frequency ca. 11-9 Hz. A method, based on steady-state aerodynamic and momenthum theories, is derived to calculate the lift and drag coefficients as averaged over the whole wing the whole wing-stroke for horizontal flapping flight. This is a further development of Pennycuick's (1968) and Weis-Fogh's (1972) expressions for calculating the lift coefficient. The lift coefficient obtained varies between 1-4 and 1-6, the drag coefficient between 0-4 and 1-2, and the lift:drag ratio between 1-2 and 4-0. The corresponding, calculated, total specific mechanical power output of the wing muscles varies between 27-0 and 40-4 W kg-1 body mass. A maximum estimate of mechanical efficiency is 0–26. The aerodynamic efficiency varies between 0–07 and 0–10. The force coefficient, total mechanical power output, and mechanical and aerodynamic efficiencies are all plausible, demonstrating that the slow flapping flight of Plecotus is thus explicable by steady-state aerodynamics. The downstroke is the power stroke for the vertical upward forces and the upstroke for the horizontal forward forces.

Dragonfly flight. III. Lift and power requirements.

1997 ◽  
Vol 200 (3) ◽  
pp. 583-600 ◽  
Author(s):  
JM Wakeling ◽  
CP Ellington
Keyword(s):  
Heat Production ◽  
Power Output ◽  
Aerodynamic Force ◽  
Lift Coefficient ◽  
Mechanical Efficiency ◽  
Specific Power ◽  
Free Flight ◽  
Mechanical Power Output ◽  
Low Costs ◽  
Calopteryx Splendens

A mean lift coefficient quasi-steady analysis has been applied to the free flight of the dragonfly Sympetrum sanguineum and the damselfly Calopteryx splendens. The analysis accommodated the yaw and accelerations involved in free flight. For any given velocity or resultant aerodynamic force (thrust), the damselfly mean lift coefficient was higher than that for the dragonfly because of its clap and fling. For both species, the maximum mean lift coefficient L was higher than the steady CL,max. Both species aligned their strokes planes to be nearly normal to the thrust, a strategy that reduces the L required for flight and which is different from the previously published hovering and slow dragonfly flights with stroke planes steeply inclined to the horizontal. Owing to the relatively low costs of accelerating the wing, the aerodynamic power required for flight represents the mechanical power output from the muscles. The maximum muscle mass-specific power was estimated at 156 and 166 W kg-1 for S. sanguineum and C. splendens, respectively. Measurements of heat production immediately after flight resulted in mechanical efficiency estimates of 13 % and 9 % for S. sanguineum and C. splendens muscles, respectively.

scholarly journals Total power output generated during dynamic knee extensor exercise at different contraction frequencies

2000 ◽  
Vol 89 (5) ◽  
pp. 1912-1918 ◽  
Author(s):  
Richard A. Ferguson ◽  
Per Aagaard ◽  
Derek Ball ◽  
Anthony J. Sargeant ◽  
Jens Bangsbo
Keyword(s):  
Power Output ◽  
Accurate Determination ◽  
Knee Extensor ◽  
Mechanical Efficiency ◽  
Muscle Group ◽  
Total Power ◽  
Mechanical Power Output ◽  
External Power ◽  
Power Outputs ◽  
Total Power Output

A novel approach has been developed for the quantification of total mechanical power output produced by an isolated, well-defined muscle group during dynamic exercise in humans at different contraction frequencies. The calculation of total power output comprises the external power delivered to the ergometer (i.e., the external power output setting of the ergometer) and the “internal” power generated to overcome inertial and gravitational forces related to movement of the lower limb. Total power output was determined at contraction frequencies of 60 and 100 rpm. At 60 rpm, the internal power was 18 ± 1 W (range: 16–19 W) at external power outputs that ranged between 0 and 50 W. This was less ( P < 0.05) than the internal power of 33 ± 2 W (27–38 W) at 100 rpm at 0–50 W. Moreover, at 100 rpm, internal power was lower ( P < 0.05) at the higher external power outputs. Pulmonary oxygen uptake was observed to be greater ( P< 0.05) at 100 than at 60 rpm at comparable total power outputs, suggesting that mechanical efficiency is lower at 100 rpm. Thus a method was developed that allowed accurate determination of the total power output during exercise generated by an isolated muscle group at different contraction frequencies.

Dynamic Lift Coefficients for Spade Rudders on Yachts

2007 ◽  
Author(s):  
Paul H. Miller
Keyword(s):  
Lift Coefficient ◽  
Bending Moment ◽  
Pressure Profile ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Back Calculation ◽  
Computational Fluid Dynamics Cfd ◽  
Sailing Yacht ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The loss of a rudder is a dangerous situation for any vessel, and with the increasingly higher aspect ratios in current sailing yacht rudder designs, a better understanding of the forces on a rudder are required. While many failures have been caused by impacts with objects, a large number have failed due to underestimation of sailing loads. While larger aspect ratios increase the lift-to-drag ratio, they also increase the bending moment about the rudder’s root. Combined with thinner airfoil sections to reduce drag, modern rudders are highly stressed. Traditional design methods normally assume that the maximum lift coefficient is constant for all aspect ratios. This project combined computational fluid dynamics (CFD), finite element analysis (FEA) and the tank testing of a 1/5-scale yacht to determine suitable design lift coefficients for spade rudders of cruising and racing yachts. Two rudders of different aspect ratios were tested at various speeds, heel angles and wave conditions in the tank at the Naval Surface Warfare Center – Carderock Division. The rudders were equipped with strain gauges to determine the strains at various positions along the stock and blade. The strain profile was compared against FEA results that used a CFD prediction of the pressure profile. Through back-calculation the lift coefficients in still water and waves were derived. The results indicated that these lift coefficients are not constant.

Aerodynamics of hovering flight in the long-eared bat Plecotus auritus

1976 ◽  
Vol 65 (2) ◽  
pp. 459-470 ◽  
Author(s):  
U. M. Norberg
Keyword(s):  
Steady State ◽  
Drag Coefficient ◽  
Lift Coefficient ◽  
Quasi Steady State ◽  
Hovering Flight ◽  
Drag Coefficients ◽  
Lift And Drag

Steady-state aerodynamic and momentum theories were used for calculations of the lift and drag coefficients of Plecotus auritus in hovering flight. The lift coefficient obtained varies between 3-1 and 6-4, and the drag coefficient between --5-0 and 10-5, for the possible assumptions regarding the effective angles of attack during the upstroke. This demonstrates that hovering flight in Plecotus auritus can not be explained by quasi-steady-state aerodynamics. Thus, non-steady-state aerodynamics must prevail.

scholarly journals EFFECTS OF OPERATING FREQUENCY AND TEMPERATURE ON MECHANICAL POWER OUTPUT FROM MOTH FLIGHT MUSCLE

1990 ◽  
Vol 149 (1) ◽  
pp. 61-78 ◽  
Author(s):  
R. D. STEVENSON ◽  
ROBERT K. JOSEPHSON
Keyword(s):  
Power Output ◽  
Flight Muscle ◽  
Beat Frequency ◽  
Length Change ◽  
Mechanical Power ◽  
Work Output ◽  
Optimal Frequency ◽  
Hovering Flight ◽  
Cycle Frequency ◽  
Mechanical Power Output

1. Mechanical work output was determined for an indirect flight muscle, the first dorsoventral, of the tobacco hawkmoth Manduca sexta. Work output per cycle was calculated from the area of force-position loops obtained during phasic electrical stimulation (1 stimulus cycle−1) and imposed sinusoidal length change. There was an optimal stimulus phase and an optimal length change (strain) that maximized work output (loop area) at constant cycle frequency and temperature. 2. When cycle frequency was increased at constant temperature, work output first increased and then decreased. It was always possible to find a frequency that maximized work output. There also always existed a higher frequency (termed the ‘optimal’ frequency in this paper) that maximized the mechanical power output, which is the product of the cycle frequency (s−1) and the work per cycle (J). 3. As temperature increased from 20 to 40°C, the mean maximum power output increased from about 20 to about 90 W kg−1 of muscle (Q10=2.09). There was a corresponding increase in optimal frequency from 12.7 to 28.3 Hz, in the work per cycle at optimal frequency from 1.6 to 3.2Jkg−1 muscle and in mean optimal strain from 5.9 to 7.9%. 4. Two electrical stimuli per cycle cannot increase power output at flight frequencies, but if frequency is reduced then power output can be increased with multiple stimulation. 5. Comparison of mechanical power output from muscle and published values of energy expenditure during free hovering flight of Manduca suggests that mechanical efficiency is about 10%. 6. In the tobacco hawkmoth there is a good correspondence between, on the one hand, the conditions of temperature (35–40°C) and cycle frequency (28–32 Hz) that produce maximal mechanical power output in the muscle preparation and, on the other hand, the thoracic temperature (35–42°C) and wing beat frequency (24–32 Hz) observed during hovering flight.

Exercise slightly above the maximal lactate steady state reduces self-efficacy and increases negative affect

2019 ◽  
Author(s):  
James Graeme Wrightson ◽  
Louis Passfield
Keyword(s):  
Steady State ◽  
Negative Affect ◽  
Power Output ◽  
Self Efficacy ◽  
Repeated Measures ◽  
Physiological State ◽  
Constant Load ◽  
Peak Power Output ◽  
Time To Exhaustion ◽  
Maximal Lactate Steady State

Objectives: To examine the effect of exercise at and slightly above the maximal lactate steady state (MLSS) on self-efficacy, affect and effort, and their associations with exercise tolerance.Design: Counterbalanced, repeated measures designMethod: Participants performed two 30‐minute constant‐load cycling exercise at a power output equal to that at MLSS and 10 W above MLSS, immediately followed by a time‐to‐exhaustion test at 80% of their peak power output. Self-efficacy, affect and effort were measured before and after 30 minutes of cycling at and above MLSS.Results: Negative affect and effort higher, and self-efficacy and time to exhaustion were reduced, following cycling at MLSS + 10 W compared to cycling at the MLSS. Following exercise at the MLSS self-efficacy, affect and effort were all associated with subsequent time-to exhaustion. However, following exercise at MLSS + 10 W, only affect was associated with time-to exhaustion. Conclusions: Self efficacy, affect and effort are profoundly affected by physiological state, highlighting the influence of somatic states on perceptions and emotions during exercise. The affective response to exercise appears to be associated with exercise tolerance, indicating that the emotional, as well as physiological, responses should be considered when prescribing exercise training.

scholarly journals On the mechanical power output comparisons of cone dielectric elastomer actuators

2021 ◽  
pp. 1-1
Author(s):  
Chongjing Cao ◽  
Lijin Chen ◽  
Wenke Duan ◽  
Thomas L. Hill ◽  
Bo Li ◽  
...  
Keyword(s):  
Power Output ◽  
Dielectric Elastomer ◽  
Mechanical Power ◽  
Dielectric Elastomer Actuators ◽  
Mechanical Power Output

scholarly journals Unsteady Simulation of Transonic Buffet of a Supercritical Airfoil with Shock Control Bump

Aerospace ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 203
Author(s):  
Yufei Zhang ◽  
Pu Yang ◽  
Runze Li ◽  
Haixin Chen
Keyword(s):  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Flow Characteristics ◽  
Control Effect ◽  
Shock Control Bump ◽  
Shock Control ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Unsteady Simulation ◽  
Drag Ratio

The unsteady flow characteristics of a supercritical OAT15A airfoil with a shock control bump were numerically studied by a wall-modeled large eddy simulation. The numerical method was first validated by the buffet and nonbuffet cases of the baseline OAT15A airfoil. Both the pressure coefficient and velocity fluctuation coincided well with the experimental data. Then, four different shock control bumps were numerically tested. A bump of height h/c = 0.008 and location xB/c = 0.55 demonstrated a good buffet control effect. The lift-to-drag ratio of the buffet case was increased by 5.9%, and the root mean square of the lift coefficient fluctuation was decreased by 67.6%. Detailed time-averaged flow quantities and instantaneous flow fields were analyzed to demonstrate the flow phenomenon of the shock control bumps. The results demonstrate that an appropriate “λ” shockwave pattern caused by the bump is important for the flow control effect.

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