Biology and physics of locust flight. III. The aerodynamics of locust flight

1956 ◽  
Vol 239 (667) ◽  
pp. 511-552 ◽  
Keyword(s):  
Body Weight ◽  
Posterior Part ◽  
Slow Motion ◽  
Middle Part ◽  
The Body ◽  
Vertical Force ◽  
Aerodynamic Forces ◽  
Locust Flight ◽  
Lift And Drag ◽  
Wing Stroke

A proper understanding of how locusts fly must be based upon knowledge of how the wings are moved. A desert locust was suspended from a balance and placed in an air stream so that it flew under nearly the same conditions as during natural forward flight. Four stroboscopic slow-motion films were selected for measurement. The movements of the wings, i.e. their positions, velocities and accelerations, were then calculated in sufficient detail to show how these quantities vary with time during one complete wing stroke. The aerodynamic lift and drag of the entire natural wing were measured in a wind tunnel with the wing arranged in different positions relative to the flow. By placing it in the boundary layer of the tunnel, the wind speed was graded from tip to base in approximately the same way as during the actual flight. There is therefore no error due to scale effect or to the induced drag. In most respects the wings resemble ordinary, slightly cambered airfoils. Their characteristics are given as polar diagrams. The kinematic and aerodynamic analyses make it possible to calculate the forces which act upon the locust at any instant of time. It is here necessary to presuppose that the non-stationary flight situations are essentially similar to a sequence of stationary situations. For locusts, this presupposition is justified: (i) from theoretical estimates of the quantitative effect of non-stationary flow; and (ii) from control measurements of the average thrust and lift produced during flight. It was found that the calculated vertical force, when averaged over an entire wing stroke, equalled the average reduction in body weight, as measured directly on the flight balance. Similarly, the average thrust of the wings corresponded to the drag of the body. The analysis shows how the aerodynamic forces vary during the wing stroke. The hindwings are responsible for about 70 % of the total lift and thrust. About 80 % of the lift is produced during the downstroke. During flight at normal lift the angles of attack (middle part of wing) are small during the upstroke and vary between 10 and 15° during the downstroke. When the lift was larger or smaller than the body weight these figures increased or decreased respectively. The forewings are peculiar in two ways: (i) during the middle part of the downstroke a true flap (the vannus) is put into action; (ii) during the upstroke the proximal part has a Z-shaped cross-section and gives but little lift and drag. The hindwings are characteristic in that the posterior part (vannus) is flexible and becomes moulded by the wind, increasing the angle of attack at which stalling occurs to about 25°. Since both the movements of the wings relative to the body and the aerodynamic forces are known at any instant, the exchange of power with the surrounding air can be calculated. The moments of inertia of the wing mass being known, the power for accelerating the wings can also be estimated. The sum of these contributions is the power which passes the wing fulcrum; this estimate is used in a later paper (part IX) where the energetics of flight is discussed in detail. The diagrams are correct to scale. The restriction of freedom caused by the suspension is discussed, together with the possible errors of a stationary analysis.

scholarly journals Birds repurpose the role of drag and lift to take off and land

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Diana D. Chin ◽  
David Lentink
Keyword(s):  
Flapping Wings ◽  
Vertical Force ◽  
Horizontal Force ◽  
Aerodynamic Forces ◽  
Braking Force ◽  
Drag And Lift ◽  
Lift And Drag ◽  
Wing Stroke

AbstractThe lift that animal wings generate to fly is typically considered a vertical force that supports weight, while drag is considered a horizontal force that opposes thrust. To determine how birds use lift and drag, here we report aerodynamic forces and kinematics of Pacific parrotlets (Forpus coelestis) during short, foraging flights. At takeoff they incline their wing stroke plane, which orients lift forward to accelerate and drag upward to support nearly half of their bodyweight. Upon landing, lift is oriented backward to contribute a quarter of the braking force, which reduces the aerodynamic power required to land. Wingbeat power requirements are dominated by downstrokes, while relatively inactive upstrokes cost almost no aerodynamic power. The parrotlets repurpose lift and drag during these flights with lift-to-drag ratios below two. Such low ratios are within range of proto-wings, showing how avian precursors may have relied on drag to take off with flapping wings.

Biology and physics of locust flight IV. Notes on sensory mechanisms in locust flight

1956 ◽  
Vol 239 (667) ◽  
pp. 553-584 ◽  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Sense Organ ◽  
The Body ◽  
Horizontal Wind ◽  
Body Angle ◽  
Locust Flight ◽  
Adequate Stimulus ◽  
The Central Nervous System ◽  
Wing Stroke

The wing stroke of locusts is remarkably constant and independent of external conditions. Is this rigid rhythmicity due to a rhythmicity of the central nervous system or is it determined by peripheral factors? The flight behaviour of the desert locust ( Schistocera gregaria ) was studied under various experimental conditions in order to find which external factors can initiate, maintain or alter the wing movements, excluding reactions which depend upon higher nervous centres. The ‘tarsal reflex’ and the response seen when the aerodynamic sense organ on the head is stimulated (Weis-Fogh 1949, 1950) were reinvestigated in order to relate them to two hitherto unknown reactions: the maintenance of flapping when the wings are exposed to wind and the regulation of the lift when the body angle ( = angle of pitch) is changed during forward flight. Both depend on receptors whose nature is still unknown. Inhibition . As in most other insects, the flight of a locust cannot be started when the legs, or only part of one leg, have contact with a rigid body; flight stops when such contact is regained. Amputation of the legs abolishes these reactions, showing that some leg proprioceptors inhibit flight. Initiation . A suspended locust can be induced to fly in three ways. (1) By application of a sufficiently strong stimulus which normally provokes escape reactions; the flight lasts only a few seconds. Adaptation is generally quick. (2) By sudden removal of the support for the legs (‘ tarsal reflex’ although not confined to the tarsi). The flight lasts 5 s on average, corresponding to one hundred wing strokes. There is practically no adaptation. (3) By blowing upon the wind-sensitive hairs on the head. The wind must exceed 2 m/s, but its direction is of little importance. Since the static bending has no effect, the adequate stimulus seems to be minute vibrations of the hairs. The flight lasts as long as the wind blows and the hairs are therefore also involved in the maintenance of flight. When the locust has stopped, the legs begin to flutter, and eventually remain still, but normally flight is not resumed unless one of the above stimuli is applied. Maintenance . Two receptor systems are involved. (1) The wind-sensitive hairs on the head. In a wind they emit impulses irrespectively of whether the locust has any chance of flapping its wings or not. ‘Wind on the head’ is therefore an extrinsic flight stimulus. The flight posture is never complete. (2) A hitherto unknown receptor system in the pterothorax which was studied in insects whose supra-oesophageal ganglia were cauterized (‘decerebrate’). It maintains the movements when the wings oscillate in a wind but cannot initiate them; the adequate stimulus is the rhythmically changing wind pressure on the wings. ‘Wind on the wings’ is therefore an intrinsic flight stimulus. When the average lift exceeds half the body weight, flight continues in complete flight posture but stops when the lift approaches zero. The experiments indicate that the stimulation ceases when the lift becomes negative during the upstroke . The receptors are unknown; it is suggested that they are situated at the wing hinge. The locust does not adapt to either of these stimuli and invariably stops a few seconds after they have ceased. Control of lift . The locust tends to keep the lift constant during a given performance. This observation, together with the constancy of most stroke parameters, made it possible to investigate the mechanism involved. The method was to make the insect fly steadily against a horizontal wind and then alter the inclination to the wind (= the body angle) at regular intervals. The data permitted an estimate of the mean change in wing twisting Δθ. Δθ increased (wings pronated) by 15 ± 3° when the body angle was increased from 0 to 15°. This is the main factor in the control of lift. The discussion shows that this presupposes a system of lift-sensitive receptors (probably campaniform sensilla at the wing hinge). If present in other insects, the homoeostatic character of the wing stroke of Drosophila (Chadwick 1953) may therefore be caused by a nervous mechanism and need not be a consequence of the energetics of flight. Central rhythm . It is concluded that the central nervous system ( does not initiate flight rhythm de novo ; ( b ) does neither determine the stroke frequency nor the strength of the contractions of the controller-depressor muscles; ( c ) may control the phasing of the contractions, although a simpler hypothesis is advanced; ( d ) may control the indirect flight muscles but only as far as to produce stimuli of constant (maximum?) strength.

Aerodynamics of Flapping Flight with Application to Insects

1951 ◽  
Vol 28 (2) ◽  
pp. 221-245 ◽  
Author(s):  
M. F. M. OSBORNE
Keyword(s):  
Power Plants ◽  
Insect Flight ◽  
The Body ◽  
Specific Power ◽  
Vertical Force ◽  
Flat Plates ◽  
Force Coefficients ◽  
Wing Motion ◽  
Lift And Drag ◽  
Geometrical Dimensions

1. General formulae are derived giving the lift, thrust and power when the wing motion is specified. The formulae are applied to twenty-five insects for which quantitative data are available. Average values for lift and drag coefficients, CL and CD, are derived by equating the weight to the vertical force and the thrust to the horizontal drag of the body. 2. The large drag and lift coefficients obtained for insect flight are attributed to acceleration effects. There is a distinct correlation between (C2L,+ C2)D)½ and the ratio of the flapping velocity of the wings to the linear velocity of flight. When this ratio and therefore the accelerations are small, the force coefficients do not exceed those to be expected for flat plates. Owing to the nature of the assumptions and approximations made, the values derived for CD, CL and CD/CL are minimum values. 3. Other characteristics of insect flight are discussed. In general, insects fly in such a way as to minimize the mechanical power required. In most, but not all cases, the useful force is the one perpendicular rather than parallel to the relative wind. The wing tips should move in a figure 8, the down beat should be slower than the up beat, and the majority of the necessary force must be supplied on the down beat. 4. Figures are given using the data from the twenty-five insects considered, showing average relations between power, specific power, mass, acceleration forces, force coefficients and geometrical dimensions. The power per gram, the ‘wasted power’, and the force coefficients all increase as the importance of the acceleration forcesincreases. 5. When plotted as functions of mass, quantities involving the power show much less dispersion than quantities involving the geometrical dimensions. This is taken to mean that despite the diversity of insect form, as ‘power plants’, they are all essentially similar. 6. A table of the observed or adopted flight parameters (frequency of beating, mass, wing area, velocity of flight, amplitude and orientation of wing motion) is appended.

Influence of calibration protocols for a pressure-sensing walkway on kinetic and temporospatial parameters

2015 ◽  
Vol 28 (01) ◽  
pp. 25-29 ◽  
Author(s):  
F. S. Agostinho ◽  
B. Geraldo ◽  
P. L. T. Justolin ◽  
C. R. Teixeira ◽  
F. L. M. L. Lins ◽  
...  
Keyword(s):  
Body Weight ◽  
Clinical Significance ◽  
Body Mass ◽  
Kinetic Data ◽  
The Body ◽  
The Other ◽  
Vertical Force ◽  
Calibration Technique ◽  
Pressure Sensing ◽  
Calibration Protocol

SummaryObjectives: To evaluate the influence on the kinetic and temporospatial parameters of calibration protocols with point and step techniques for a pressure-sensing walkway.Methods: Nine Labrador dogs were used. Two protocols of point calibration technique (C1 and C2) and eight protocols of step calibration technique (C3 to C10) were performed. In C1, weight was added to a stool to match the body mass of each dog. In C2, weight was added to the stool to match a 46.1 kg person. The other eight calibration protocols represented combinations of the following factors: 46.1 kg and 96.1 kg persons, barefoot or wearing sneakers, and stepping onto the platform with one or two feet.Results: The calibration protocols did not affect the temporospatial variables or percentages of body weight (%BW) distribution. Significant differences were found in both PVI (peak vertical force) and VI (vertical impulse) between barefoot versus wearing sneakers, 46.1 kg versus 96.1 kg person, and stepping onto the platform with one foot versus two feet. When comparing C1 with other protocols, significant differences were observed in PVF and VI for both forelimbs and hindlimbs. When comparing C2 with other protocols, significant differences were observed in PVF and VI for both forelimbs and hindlimbs in all protocols.Clinical significance: The PVF and VI were influenced by the calibration protocol used, but the %BW distribution and temporospatial parameters were not. Using the same calibration protocol for all dogs within the same group eliminated the variability of the kinetic data caused by the calibration.

scholarly journals Force on the sacrococcygeal and ischial areas during posterior pelvic tilt in seated posture

2012 ◽  
Vol 37 (4) ◽  
pp. 282-288 ◽  
Author(s):  
Taro Kemmoku ◽  
Katsuro Furumachi ◽  
Tadashi Shimamura
Keyword(s):  
Body Weight ◽  
Repeated Measures ◽  
Pelvic Tilt ◽  
Pressure Ulcers ◽  
Ischial Tuberosity ◽  
The Body ◽  
Vertical Force ◽  
Horizontal Force ◽  
Repeated Measures Design ◽  
Seated Posture

Background: Most posture problems encountered in persons who use wheelchairs in a seated posture for extended periods are related to sacral sitting due to posterior pelvic tilt. Posterior pelvic tilt places pressure and shearing force on the sacrococcygeal area that can lead to pressure ulcers, but the relationship between pelvic tilt and force applied to the sacrococcygeal and ischial tuberosity areas has not yet been investigated. Objective: To investigate the relationships of posterior pelvic tilt in a seated posture with vertical force and horizontal force on the sacrococcygeal and ischial tuberosity areas. Study Design: Repeated measures design. Methods: Thirty male and female subjects aged ≥60 years sat in a measurement chair at varying pelvic tilt angles, and force on the sacrococcygeal and ischial tuberosity areas was measured. Results: The pressure on the sacrococcygeal area increased with pelvic tilt in all subjects, with vertical force averaging 19% of the body weight at a pelvic tilt angle of 30°. The horizontal force on the sacrococcygeal area increased in 93% of the subjects, with an average increase equal to 3% of the body weight. Conclusions: We confirmed changes in vertical and horizontal forces on the sacrococcygeal and ischial tuberosity areas with a change in seated posture (pelvic tilt). Clinical relevance: We propose guidelines for rehabilitation practitioners working with wheelchair users to suggest improved ways of sitting in wheelchairs that avoid pelvic tilt angles that might promote pressure ulcers on the buttocks.

Force platforms as ergometers

1975 ◽  
Vol 39 (1) ◽  
pp. 174-179 ◽  
Author(s):  
G. A. Cavagna
Keyword(s):  
Body Weight ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Force Plate ◽  
Vertical Displacement ◽  
The Body ◽  
Mechanical Work ◽  
Vertical Force ◽  
External Work ◽  
Total Mechanical Energy

Walking and running on the level involves external mechanical work, even when speed averaged over a complete stride remains constant. This work must be performed by the muscles to accelerate and/or raise the center of mass of the body during parts of the stride, replacing energy which is lost as the body slows and/or falls during other parts of the stride. External work can be measured with fair approximation by means of a force plate, which records the horizontal and vertical components of the resultant force applied by the body to the ground over a complete stride. The horizontal force and the vertical force minus the body weight are integrated electronically to determine the instantaneous velocity in each plane. These velocities are squared and multiplied by one-half the mass to yield the instantaneous kinetic energy. The change in potential energy is calculated by integrating vertical velocity as a function of time to yield vertical displacement and multiplying this by body weight. The total mechanical energy as a function of time is obtained by adding the instantaneous kinetic and potential energies. The positive external mechanical work is obtained by adding the increments in total mechanical energy over an integral number of strides.

Kinematics and mechanics of ground take-off in the starling Sturnis vulgaris and the quail Coturnix coturnix

2000 ◽  
Vol 203 (4) ◽  
pp. 725-739 ◽  
Author(s):  
K.D. Earls
Keyword(s):  
Body Weight ◽  
High Speed ◽  
Force Plate ◽  
Columba Livia ◽  
The Body ◽  
Whole Body ◽  
Vertical Force ◽  
Wing Movement ◽  
Coturnix Coturnix ◽  
Starting Point

The mechanics of avian take-off are central to hypotheses about flight evolution, but have not been quantified in terms of whole-body movements for any species. In this study, I use a combination of high-speed video analysis and force plate recording to measure the kinematics and mechanics of ground take-off in the European starling Sturnis vulgaris and the European migratory quail Coturnix coturnix. Counter to hypotheses based on the habits and morphology of each species, S. vulgaris and C. coturnix both produce 80–90 % of the velocity of take-off with the hindlimbs. S. vulgaris performs a countermovement jump (peak vertical force four times body weight) followed by wing movement, while C. coturnix performs a squat jump (peak vertical force 7.8 times body weight) with simultaneous wing movement. The wings, while necessary for continuing the movement initiated by the hindlimbs and thereafter supporting the body weight, are not the primary take-off accelerator. Comparison with one other avian species in which take-off kinematics have been recorded (Columba livia) suggests that this could be a common pattern for living birds. Given these data and the fact that running take-offs such as those suggested for an evolving proto-flier are limited to large or highly specialized living taxa, a jumping model of take-off is proposed as a more logical starting point for the evolution of avian powered flight.

L-Ascorbic Acid Addition to Chitosan Reduces Body Weight in Overweight Women

2014 ◽  
Vol 84 (1-2) ◽  
pp. 5-11 ◽  
Author(s):  
Eun Y. Jung ◽  
Sung C. Jun ◽  
Un J. Chang ◽  
Hyung J. Suh
Keyword(s):  
Ascorbic Acid ◽  
Body Weight ◽  
Fat Body ◽  
Body Weight Gain ◽  
Skinfold Thickness ◽  
The Body ◽  
Control Group ◽  
Percentage Body Fat ◽  
Overweight Women ◽  
Body Weights

Previously, we have found that the addition of L-ascorbic acid to chitosan enhanced the reduction in body weight gain in guinea pigs fed a high-fat diet. We hypothesized that the addition of L-ascorbic acid to chitosan would accelerate the reduction of body weight in humans, similar to the animal model. Overweight subjects administered chitosan with or without L-ascorbic acid for 8 weeks, were assigned to three groups: Control group (N = 26, placebo, vehicle only), Chito group (N = 27, 3 g/day chitosan), and Chito-vita group (N = 27, 3 g/day chitosan plus 2 g/day L-ascorbic acid). The body weights and body mass index (BMI) of the Chito and Chito-vita groups decreased significantly (p < 0.05) compared to the Control group. The BMI of the Chito-vita group decreased significantly compared to the Chito group (Chito: -1.0 kg/m2 vs. Chito-vita: -1.6 kg/m2, p < 0.05). The results showed that the chitosan enhanced reduction of body weight and BMI was accentuated by the addition of L-ascorbic acid. The fat mass, percentage body fat, body circumference, and skinfold thickness in the Chito and Chito-vita groups decreased more than the Control group; however, these parameters were not significantly different between the three groups. Chitosan combined with L-ascorbic acid may be useful for controlling body weight.

Hand-assisted laparoscopic nephrectomy in morbidly obese patients

2020 ◽  
Vol 99 (6) ◽  
pp. 271-276
Keyword(s):  
Body Weight ◽  
Surgical Technique ◽  
Blood Loss ◽  
Hospital Stay ◽  
Kidney Cancer ◽  
The Body ◽  
Laparoscopic Nephrectomy ◽  
Morbidly Obese ◽  
Obese Patients ◽  
Morbid Obese

Introduction: Prevalence of obesity is 30 % in the Czech Republic and is expected to increase further in the future. This disease complicates surgical procedures but also the postoperative period. The aim of our paper is to present the surgical technique called hand-assisted laparoscopic nephrectomy (HALS), used in surgical management of kidney cancer in morbid obese patients with BMI >40 kg/m2. Methods: The basic cohort of seven patients with BMI >40 undergoing HALS nephrectomy was retrospectively evaluated. Demographic data were analyzed (age, gender, body weight, height, BMI and comorbidities). The perioperative course (surgery time, blood loss, ICU time, hospital stay and early complications), tumor characteristics (histology, TNM classification, tumor size, removed kidney size) and postoperative follow-up were evaluated. Results: The patient age was 38−67 years; the cohort included 2 females and 5 males, the body weight was 117−155 kg and the BMI was 40.3−501 kg/m2. Surgery time was 73−98 minutes, blood loss was 20−450 ml, and hospital stay was 5−7 days; incisional hernia occurred in one patient. Kidney cancer was confirmed in all cases, 48–110 mm in diameter, and the largest removed specimen size was 210×140×130 mm. One patient died just 9 months after the surgery because of metastatic disease; the tumor-free period in the other patients currently varies between 1 and 5 years. Conclusion: HALS nephrectomy seems to be a suitable and safe surgical technique in complicated patients like these morbid obese patients. HALS nephrectomy provides acceptable surgical and oncological results.

HISTOLOGICAL CHANGES IN THE INTESTINES OF POULTRY DURING FODDER INTOXICATION

2020 ◽  
Author(s):  
E.P. Dolgov ◽  
◽  
A.A. Abramov ◽  
E.V. Kuzminova ◽  
E.V. Rogaleva ◽  
...  
Keyword(s):  
Body Weight ◽  
Histological Examination ◽  
Aflatoxin B1 ◽  
Structural Changes ◽  
Clinical Manifestations ◽  
Feed Additives ◽  
The Body ◽  
Histological Changes ◽  
Beet Pulp

The article presents the data on the study of the influence of mycotoxins combination (T-2 toxin at the concentration of 0.095 mg/kg and aflatoxin B1 in the concentration of 0.019 mg/kg) on the body of quails and the results of pharmacocorrection of toxicosis with a complex consisting of beet pulp and lecithin. Structural changes in the intestines of quais at fodder mycotoxicosis are described. The use of antitoxic feed additives in poultry led to a weakening of the action of xenobiotics, which was confirmed by an increase in the safety of poultry and increase in body weight of quails, a decrease in the clinical manifestations of intoxication, as well as in positive changes in the structure of the intestine of the poultry during histological examination.

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