Mass-specific Power Research Articles

Dragonfly flight. III. Lift and power requirements.

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.

The Roles of Pink and Red Muscle in Powering Steady Swimming in Scup,Stenotomus chrysops

Synopsis. Fishes power steady, undulatory swimming using both red and pink muscle. In this study we examined the roles of the two fiber types in generating power for swimming by using a two-step technique. First, in vivo data is collected from swimming fish, and second, the electrical activity and muscle length change conditions recorded in vivo are recreated in vitro with isolated muscle bundles. Force production and power generation by muscle during swimming can then be estimated. In scup, both red and pink muscle are recruited to power swimming at the maximum sustained swimming speed. For both fiber types, the duration of electrical activity decreases from anterior to posterior. However, the amplitude of muscle length change increases anterior to posterior. Massspecific power production increases posteriorly for both muscle types. The faster contraction kinetics of pink muscle translate to higher power pro? duction by pink muscle relative to red muscle for all longitudinal positions of the fish. Determination of absolute power production, based on massspecific power and muscle mass, shows that the posterior regions of the fish generate the most power for swimming. At 20?C, red muscle generates more absolute power than pink due to its higher muscle mass. However, at 10?C, pink muscle generates more absolute power than red, because red muscle produces little or no positive power for all longitu? dinal positions.

Quantitative distribution of muscle fiber types in the scup Stenotomus chrysops.

Because the mass-specific power generated by myotomal muscle during swimming varies along the length of the fish, a realistic assessment of total power generation by the musculature requires integrating the product of mass-specific power and muscle mass at each position over the length of the fish. As a first step toward this goal, we examined the distribution of red, pink, and white muscle along the length of Stenotomus chrysops (scup) using histochemical and image analysis techniques. The largest cross-sectional area of red fibers occurs at 60% of total fish length and declines both anteriorly and posteriorly. By contrast, white fibers have the largest cross-sectional area in the anterior and decline dramatically moving posteriorly. The proportion of the fishes' cross-section occupied by red fibers increases from 1.37% to 8.42% moving posteriorly along the length of the fish. In contrast, the proportion of cross-sectional area occupied by pink fibers is constant (1.19%), while the proportional cross-sectional area of white fibers falls from 82.5% to 66.3%. The red, pink, and white fibers comprise 2.09, 0.73, and 51.1%, respectively, of total fish weight. We also compared the distribution of muscle in 10 degrees C- and 20 degrees C- acclimated animals. The value for red fiber volume, though slightly higher (13%) in cold-acclimated fish, is not statistically different. No difference was found in pink or white fibers. Finally, the finding that most of the red muscle is in the posterior half of the fish further supports the notion that most power for steady swimming at moderate speeds comes from posterior rather than anterior musculature.

Quantitative distribution of muscle fiber types in the scup Stenotomus chrysops

Because the mass-specific power generated by myotomal muscle during swimming varies along the length of the fish, a realistic assessment of total power generation by the musculature requires integrating the product of mass-specific power and muscle mass at each position over the length of the fish. As a first step toward this goal, we examined the distribution of red, pink, and white muscle along the length of Stenotomus chrysops (scup) using histochemical and image analysis techniques. The largest cross-sectional area of red fibers occurs at 60% of total fish length and declines both anteriorly and posteriorly. By contrast, white fibers have the largest cross-sectional area in the anterior and decline dramatically moving posteriorly. The proportion of the fishes' cross-section occupied by red fibers increases from 1.37% to 8.42% moving posteriorly along the length of the fish. In contrast, the proportion of cross-sectional area occupied by pink fibers is constant (1.19%), while the proportional cross-sectional area of white fibers falls from 82.5% to 66.3%. The red, pink, and white fibers comprise 2.09, 0.73, and 51.1%, respectively, of total fish weight. We also compared the distribution of muscle in 10°C-and 200°C-acclimated animals. The value for red fiber volume, though slightly higher (13%) in cold-acclimated fish, is not statistically different. No difference was found in pink or white fibers. Finally, the finding that most of the red muscle is in the posterior half of the fish further supports the notion that most power for steady swimming at moderate speeds comes from posterior rather than anterior musculature. © 1996 Wiley-Liss, Inc.

Limits to vertebrate locomotor energetics suggested by hummingbirds hovering in heliox

OXYGEN consumption1 and muscle power output2 of hovering hummingbirds are among the highest recorded for vertebrates. Maximum performance of hummingbirds thus approaches the upper limits of vertebrate aerobic locomotion3. Because air density is a major determinant of aerodynamic power requirements4, hovering flight performances5 can be manipulated non-invasively using nor-moxic gas mixtures of variable density6. Here we show that limits to the locomotor capacity of hovering ruby-throated hummingbirds are unequivocally indicated by aerodynamic failure at low densities less than half that of sea-level air. Hummingbirds demonstrate considerable power reserves, with muscle mass-specific power (assuming perfect elastic energy storage) averaging from 98 W kg-1 in normal air to a maximum value of 133 W kg-1 before aerodynamic failure. In contrast to such variable power expenditure, however, muscle efficiency remains approximately constant at 10%. Modulation of power output is attained primarily through variation in wing-stroke amplitude, with aerodynamic failure occurring near 180°.

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

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.

Pectoralis Muscle Force and Power Output During Different Modes of Flight in Pigeons (Columba Livia)

ABSTRACT In vivo measurements of pectoralis muscle force during different modes of free flight (takeoff, level flapping, landing, vertical ascending and near vertical descending flight) were obtained using a strain gauge attached to the dorsal surface of the delto-pectoral crest (DPC) of the humerus in four trained pigeons (Columbalivia). In one bird, a rosette strain gauge was attached to the DPC to determine the principal axis of strain produced by tension of the pectoralis. Strain signals recorded during flight were calibrated to force based on in situ measurements of tetanic force and on direct tension applied to the muscle’s insertion at the DPC. Rosette strain recordings showed that at maximal force the orientation of tensile principal strain was −15° (proximo-anterior) to the perpendicular axis of the DPC (or +75° to the longitudinal axis of the humerus), ranging from +15 to −25° to the DPC axis during the downstroke. The consistency of tensile principal strain orientation in the DPC confirms the more general use of single-element strain gauges as being a reliable method for determining in vivo pectoralis force generation. Our strain recordings show that the pectoralis begins to develop force as it is being lengthened, during the final one-third of the upstroke, and attains maximum force output while shortening during the first one-third of the downstroke. Force is sustained throughout the entire downstroke, even after the onset of the upstroke for certain flight conditions. Mean peak forces developed by the pectoralis based on measurements from 40 wingbeats for each bird (160 total) were: 24.9±3.1N during takeoff, 19.7±2.0N during level flight (at speeds of about 6–9 ms−1 and a wingbeat frequency of 8.6±0.3Hz), 18.7±2.5N during landing, 23.7±2.7N during near-vertical descent, and 26.0±1.8N during vertical ascending flight. These forces are considerably lower than the maximum isometric force (67N, P0) of the muscle, ranging from 28% (landing) to 39% (vertical ascending) of P0. Based on estimates of muscle fiber length change determined from high-speed (200frames s−1) light ciné films taken of the animals, we calculate the mass-specific power output of the pigeon pectoralis to be 51 W kg−1 during level flight (approximately 8ms−1), and 119W kg−1 during takeoff from the ground. When the birds were harnessed with weighted backpacks (50% and 100% of body weight), the forces generated by the pectoralis did not significantly exceed those observed in unloaded birds executing vertical ascending flight. These data suggest that the range of force production by the pectoralis under these differing conditions is constrained by the force–velocity properties of the muscle operating at fairly rapid rates of shortening (4.4 fiberlengths s−1 during level flight and 6.7fiberlengths s−1 during takeoff).

Power Output of Two Sizes of Atlantic Salmon (Salmo Salar) at Their Maximum Sustained Swimming Speeds

ABSTRACT The maximum sustained swimming speeds (Ums) for large (0.45 m long) and small (0.15m) Atlantic salmon were respectively 0.91 ms−1 and 0.54ms−1. Video and ciné films of fish swimming close to Ums were analysed to obtain variables required for the application of two hydrodynamic models, those of Lighthill and Yates, to determine the mean thrust and mean power output at these swimming speeds (U) close to Ums. A large fish (‘Salmon’) and a small fish (‘Smolt’) were selected for analysis. For salmon using Lighthill’s model, and , and using Yates’ model, and (U=0.87ms−1=0.96Ums). For smolt using Lighthill’s model, and , and using Yates’ model, and (U=0.37ms−1=0.69Ums). The power output for smolt swimming at 0.69Ums was corrected to that required to swim at Ums, giving (Lighthill’s model) and (Yates’ model). At Ums it was assumed that all the red muscle was used. Two fish were selected from each size group and cross-sectioned to estimate their red muscle masses. Using a maximum mass-specific power output of 5–8 W kg−1 for slow red muscle fibres allowed us to calculate that the large and small fish have a power output capacity of 0.125–0.3 W and 0.007–0.019 W, respectively. The power output values at Ums derived from the different approaches for the large (0.25–0.26 W) and small (0.0059–0.0074 W) salmon agree closely. Effects of scaling are discussed.

Limitations on Animal Flight Performance

ABSTRACT Flight performance seems to change systematically with body size: small animals can hover and fly over a wide range of speeds, but large birds taxi for takeoff and then fly over a narrow speed range. The traditional explanation for this is that the mass-specific power required for flight varies with speed according to a U-shaped curve, and it also scales between m0 and m1/6, where m is body mass. The mass-specific power available from the flight muscles is assumed to scale as m−1/3 As available power decreases with increasing body size, the range of attainable flight speeds becomes progressively reduced until the largest animals can only fly in the trough of the U-shaped curve. Above a particular size, the available power is insufficient and flapping flight is not possible. The underlying assumptions of this argument are examined in this review. Metabolic measurements are more consistent with a J-shaped curve, with little change in power from hovering to intermediate flight speeds, than with a U-shaped curve. Scaling of the mass-specific power required to fly agrees with predictions. The mass-specific power available from, the muscles, estimated from maximal loading studies, varies as m0.13. This scaling cannot be distinguished from that of the power required to fly, refuting the argument that power imposes an intrinsic scaling on flight performance. It is suggested instead that limitations on low-speed performance result from an adverse scaling of lift production with increasing body size

Comparison of the performances of stirred tank and airlift tower loop reactors

Following a consideration of the prerequisites for reactor comparison and the fundamental differences between stirred tank and airlift tower loop reactors, their performances are compared for the production of secondary metabolites: penicillin V by Penicillium chrysogenum, cephalosporin C by Cephalosporium acremonium, and tetracycline by Streptomyces aureofaciens. In stirred tank reactors, cell mass concentrations, volumetric productivities, and specific power inputs are higher than in airlift tower loop reactors. In the latter, efficiencies of oxygen transfer are higher, and specific productivities with regard to power input, substrate and oxygen consumptions, and yield coefficients of product formation with regard to substrate and oxygen consumptions are considerably higher than in stirred tank reactors. The prerequisites for improved performance are discussed.

The Scaling of Aerobic and Anaerobic Muscle Power in Rainbow Trout(Salmo Gairdneri)

ABSTRACTThe scaling of anaerobic metabolism and red muscle mass was examined in rainbow trout (Salmo gairdneri) ranging in size from 2 to 1200 g. The initial rate of white muscle lactate production during maximal burst activity was significantly higher in large (28·lcm) than in small (8·0cm) fish. ‘Resting’ lactate concentrations in anesthetized trout (approximately 30 s of stress) increased with fish size, also reflecting higher glycolytic potential for larger fish. Maximum muscle lactate concentrations following 6 min of exhaustive exercise increased from approximately 25 to 45 μmolg−1 with increased fish size (= L0·36, where L is fish length). Total white muscle lactate production, including changes in muscle mass, scaled as L3·52. A scaling comparison of total anaerobic capacity with theoretically predicted power requirements indicated decreased burst swimming performance with increased size. Red muscle mass increased from approximately 1 to 3 % of body mass with increased fish size. The positive allometry in red muscle mass (= L3·62) is greater than the scaling of power requirements during aerobic swimming predicted from hydrodynamic theory, and may provide compensation for decreased mass-specific power output with increased size.

Maximum Lift Production During Takeoff in Flying Animals

ABSTRACT Maximum lift production during takeoff in still air was determined for a wide variety of insects and a small sample of birds and bats, and was compared with variation in morphology, taxonomy and wingbeat type. Maximum lift per unit flight muscle mass was remarkably similar between taxonomic groups (54–63 N kg−1), except for animals using clap-and-fling wingbeats, where muscle mass-specific lift increased by about 25 % (72–86 N kg−1). Muscle mass-specific lift was independent of body mass, wing loading, disk loading and aspect ratio. Birds and bats yielded results indistinguishable from insects using conventional wingbeats. Interspecific differences in short-duration powered flight and takeoff ability are shown to be caused primarily by differences in flight muscle ratio, which ranges from 0·115 to 0·560 among species studied to date. These results contradict theoretical predictions that maximum mass-specific power output and lift production should decrease with increasing body mass and wing disk loading.

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

ABSTRACT 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.

Functional Dependence of the Power for Hovering on Wing Disc Loading in Hummingbirds

The mass-specific power input (metabolic cost) of hovering is independent of body mass but is proportional to the 0.5 exponent of wing disc loading for the sample considered here. The efficiency of converting energy metabolism to aerodynamic power is approximately constant at 6.23% in hummingbirds with a wide range of body mass and wing disc loading. Actuator wing disc theory of helicopter aerodynamics appears adequate for comparing the energetic cost of hovering flight among hummingbirds. Differences in the power input for hovering due to differences in wing disc loading are greater for larger hummingbirds than for smaller ones. Impaired integrity of the outer portion of the wing disc caused by molt or breaking primaries 8, 9, or 10 greatly increases the required power for hovering. The unusual nonsequential pattern of primary-feather molt in hummingbirds may be of adaptive value in that it results in the most rapid restoration of the integrity of the wing disc.