Estimates of circulation and gait change based on a three-dimensional kinematic analysis of flight in cockatiels (Nymphicus hollandicus)and ringed turtle-doves (Streptopelia risoria)

2002 ◽  
Vol 205 (10) ◽  
pp. 1389-1409 ◽  
Author(s):  
Tyson L. Hedrick ◽  
Bret W. Tobalske ◽  
Andrew A. Biewener
Keyword(s):  
Wind Tunnel ◽  
Vortex Ring ◽  
High Speed ◽  
Three Dimensional ◽  
Circulation Model ◽  
Whole Body ◽  
Vertical Acceleration ◽  
Streptopelia Risoria ◽  
Wide Range ◽  
Nymphicus Hollandicus

SUMMARYBirds and bats are known to employ two different gaits in flapping flight,a vortex-ring gait in slow flight and a continuous-vortex gait in fast flight. We studied the use of these gaits over a wide range of speeds (1-17 ms-1) and transitions between gaits in cockatiels (Nymphicus hollandicus) and ringed turtle-doves (Streptopelia risoria)trained to fly in a recently built, variable-speed wind tunnel. Gait use was investigated via a combination of three-dimensional kinematics and quasi-steady aerodynamic modeling of bound circulation on the distal and proximal portions of the wing. Estimates of lift from our circulation model were sufficient to support body weight at all but the slowest speeds (1 and 3 ms-1). From comparisons of aerodynamic impulse derived from our circulation analysis with the impulse estimated from whole-body acceleration,it appeared that our quasi-steady aerodynamic analysis was most accurate at intermediate speeds (5-11 ms-1). Despite differences in wing shape and wing loading, both species shifted from a vortex-ring to a continuous-vortex gait at 7 ms-1. We found that the shift from a vortex-ring to a continuous-vortex gait (i) was associated with a phase delay in the peak angle of attack of the proximal wing section from downstroke into upstroke and (ii) depended on sufficient forward velocity to provide airflow over the wing during the upstroke similar to that during the downstroke. Our kinematic estimates indicated significant variation in the magnitude of circulation over the course the wingbeat cycle when either species used a continuous-vortex gait. This variation was great enough to suggest that both species shifted to a ladder-wake gait as they approached the maximum flight speed (cockatiels 15 ms-1, doves 17 ms-1) that they would sustain in the wind tunnel. This shift in flight gait appeared to reflect the need to minimize drag and produce forward thrust in order to fly at high speed. The ladder-wake gait was also employed in forward and vertical acceleration at medium and fast flight speeds.

scholarly journals Flight kinematics of black-billed magpies and pigeons over a wide range of speeds

1996 ◽  
Vol 199 (2) ◽  
pp. 263-280 ◽  
Author(s):  
B Tobalske ◽  
K Dial
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Vortex Ring ◽  
High Speed ◽  
Columba Livia ◽  
Flight Speed ◽  
Body Angle ◽  
Scaling Hypothesis ◽  
Wide Range ◽  
Mechanical Power Output

To investigate how birds that differ in morphology change their wing and body movements while flying at a range of speeds, we analyzed high-speed (60 Hz) video tapes of black-billed magpies (Pica pica) flying at speeds of 4-14 m s-1 and pigeons (Columba livia) flying at 6-20 m s-1 in a wind-tunnel. Pigeons had higher wing loading and higher-aspect-ratio wings compared with magpies. Both species alternated phases of steady-speed flight with phases of acceleration and deceleration, particularly at intermediate flight speeds. The birds modulated their wingbeat kinematics among these phases and frequently exhibited non-flapping phases while decelerating. Such modulation in kinematics during forward flight is typical of magpies but not of pigeons in the wild. The behavior of the pigeons may have been a response to the reduced power costs for flight in the closed wind-tunnel relative to those for free flight at similar speeds. During steady-speed flight, wingbeat frequency did not change appreciably with increasing flight speed. Body angle relative to the horizontal, the stroke-plane angles of the wingtip and wrist relative to the horizontal and the angle describing tail spread at mid-downstroke all decreased with increasing flight speed, thereby illustrating a shift in the dominant function of wing flapping from weight support at slow speeds to positive thrust at fast speeds. Using wingbeat kinematics to infer lift production, it appeared that magpies used a vortex-ring gait during steady-speed flight at all speeds whereas pigeons used a vortex-ring gait at 6 and 8 m s-1, a transitional vortex-ring gait at 10 m s-1, and a continuous-vortex gait at faster speeds. Both species used a vortex-ring gait for acceleration and a continuous-vortex gait or a non-flapping phase for deceleration during flight at intermediate wind-tunnel speeds. Pigeons progressively flexed their wings during glides as flight speed increased but never performed bounds. Wingspan during glides in magpies did not vary with flight speed, but the percentage of bounds among non-flapping intervals increased with speed from 10 to 14 m s-1. The use of non-flapping wing postures seemed to be related to the gaits used during flapping and to the aspect ratio of the wings. We develop an 'adverse-scaling' hypothesis in which it is proposed that the ability to reduce metabolic and mechanical power output using flap-bounding flight at fast flight speeds is scaled negatively with body mass. This represents an alternative to the 'fixed-gear' hypothesis previously suggested by other authors to explain the use of intermittent flight in birds. Future comparative studies in the field would be worthwhile, especially if instantaneous flight speeds and within-wingbeat kinematics were documented; new studies in the laboratory should involve simultaneous recording of wing kinematics and aerodynamic forces on the wing.

Roughness Element Geometry Required for Wind Tunnel Simulations of the Atmospheric Wind

1977 ◽  
Vol 99 (3) ◽  
pp. 480-485 ◽  
Author(s):  
I. S. Gartshore ◽  
K. A. De Croos
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wind Tunnel ◽  
Roughness Element ◽  
Three Dimensional ◽  
Wall Stress ◽  
Wide Range ◽  
Drag Plate ◽  
Rough Boundaries ◽  
Single Figure

Using a data correlation for the wall stress associated with very rough boundaries and a semi-empirical calculation method, the shape of boundary layers in exact equilibrium with the roughness beneath them is calculated. A wide range of roughness geometries (two- and three-dimensional elements) is included by the use of equivalent surfaces of equal drag per unit area. Results can be summarized in a single figure which relates the shape factor of the boundary layer (its exponent if it has a power law velocity profile) to the height of the roughness elements and their spacing. New data for one turbulent boundary layer developing over a long fetch of uniform roughness is presented. Wall shear stress, measured directly from a drag plate is combined with boundary layer integral properties to show that the shear stress correlation adopted is reasonably accurate and that the boundary layer is close to equilibrium after passing over a streamwise roughness fetch equal to about 350 times the roughness element height. An example is given of the way in which roughness geometry may be chosen from calculated equilibrium results, for one particular boundary layer thickness and a shape useful for simulating strong atmospheric winds in a wind tunnel.

Influence of Geometric Features of the Peripheral Part of the Thin-Walled Spherical Segment on the Explosive Throwing Process

2020 ◽  
pp. 76-87
Author(s):  
M.A. Baburin ◽  
V.D. Baskakov ◽  
S.V. Eliseev ◽  
K.A. Karnaukhov ◽  
V.A. Tarasov
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Rotation ◽  
Aerodynamic Coefficients ◽  
Peripheral Part ◽  
High Speed Impact ◽  
Wide Range ◽  
Main Factors ◽  
Thin Walled ◽  
Axisymmetric Shape

The main factors controlling the formation of the stern of explosively formed projectiles are investigated using numerical calculations in a three-dimensional formulation of a problem. To form folds in the stern, it is proposed to use thin-walled spherical segments with a peripheral thickness deviation in terms of decreasing or increasing with respect to the thickness in the central part. The configurations of explosively formed projectiles with inclined folds in the stern are shown, and it is proposed to describe the fold inclination by two angles of its position. The effect of folds in the stern on the change in aerodynamic coefficients for a wide range of angle of attack is numerically studied. The angular velocity of the axial rotation of explosively formed projectiles with inclined folds in the stern is estimated based on the Newton method and considering the angles of its position. The results obtained are of interest to specialists working in the field of physics of explosion and high-speed impact, as well as those dealing with aerodynamics of aircrafts, mainly of axisymmetric shape

Three-dimensional flow structure and string cavitation in a fuel injector and their effects on discharged liquid jet

2019 ◽  
Vol 22 (1) ◽  
pp. 243-256 ◽  
Author(s):  
Rubby Prasetya ◽  
Akira Sou ◽  
Junichi Oki ◽  
Akira Nakashima ◽  
Keiya Nishida ◽  
...  
Keyword(s):  
Vortex Ring ◽  
Flow Structure ◽  
High Speed ◽  
Three Dimensional ◽  
Liquid Jet ◽  
Fuel Injector ◽  
High Speed Imaging ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Stereo Particle Image Velocimetry

Two kinds of cavitation may occur in mini-sac type diesel injectors. The first is geometrical cavitation, which can usually be seen as a film-like structure in the nozzle. The second is the filament-like string cavitation. Both types of cavitation are known to affect fuel spray characteristics, although the effects of geometrical cavitation and that of string cavitation have not been individually clarified. Moreover, the mechanism behind string cavitation occurrence is still unclear. String cavitation usually occurs at low needle lift, which might indicate the existence of a vortex ring flow in the sac. However, because of the difficulty in precise flow measurement of the three-dimensional flow structure in the sac, the link between vortex ring flow and string cavitation occurrence in the sac has not been proven. In this study, high-speed imaging of string cavitation, geometrical cavitation, and discharged liquid jet of an enlarged three-hole mini-sac diesel fuel injector was conducted to individually clarify the effects of string cavitation and geometrical cavitation on the discharged liquid jet angle. Furthermore, tomographic–stereo particle image velocimetry was carried out on the sac. The experiments were conducted at two different needle lifts, to clarify the link between needle lifts and flow structure in the sac, as well as how it affects string cavitation occurrence and liquid jet angle. The results confirmed that at low needle lift, vortex ring flow forms in the sac, which may induce helical flow in the nozzle, resulting in a large jet angle. Vortex strength varies with time, and string cavitation occurs when the vortex is particularly strong. As a result, the magnitude of the jet angle increase at low needle lift is enhanced when string cavitation occurs. At high needle lift, flow pattern in the sac becomes relatively uniform, which makes it harder for string cavitation to form.

scholarly journals Test Facility for High-Speed Probe Calibration

2019 ◽  
Vol 213 ◽  
pp. 02033
Author(s):  
Tomáš Jelínek ◽  
Erik Flídr ◽  
Martin Němec ◽  
Jan Šimák
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Total Pressure ◽  
High Speed ◽  
Test Facility ◽  
Nozzle Outlet ◽  
Wide Range ◽  
Mach Numbers ◽  
Probe Calibration ◽  
Subsonic Nozzle

A new test facility was built up as a part of a closed-loop transonic wind tunnel in VZLU´s High-speed Aerodynamics Department. The wind tunnel is driven by a twelve stage radial compressor and Mach and Reynolds numbers can be changed by the compressor speed and by the total pressure in the wind tunnel loop by a set of vacuum pumps, respectively. The facility consists of an axisymmetric subsonic nozzle with an exit diameter de = 100 mm. The subsonic nozzle is designed for regimes up to M = 1 at the nozzle outlet. At the nozzle inlet there is a set of a honeycomb and screens to ensure the flow stream laminar at the outlet of the nozzle. The subsonic nozzle can be supplemented with a transonic slotted nozzle or a supersonic rigid nozzle for transonic and supersonic outlet Mach numbers. The probe is fixed in a probe manipulator situated downstream of the nozzle and it ensures a set of two perpendicular angles in a wide range (±90°). The outlet flow field was measured through in several axial distances downstream the subsonic nozzle outlet. The total pressure and static pressure was measured in the centreline and the total pressure distribution in the vertical and horizontal plane was measured as well. Total pressure fluctuations in the nozzle centreline were detected by a FRAP probe. From the initial flow measurement in a wide range of Mach numbers the best location for probe calibration was chosen. The flow field was found to be suitable for probe calibration.

An Investigation of the Effect of Cascade Area Ratios on Transonic Compressor Performance

1994 ◽  
Author(s):  
A. R. Wadia ◽  
W. W. Copenhaver
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Area Ratio ◽  
Peak Efficiency ◽  
Trailing Edge ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Wide Range ◽  
Boundary Layer Interaction ◽  
Compressor Performance

Transonic compressor rotor performance is highly sensitive to variations in cascade area ratios. This paper reports on the design, experimental evaluation and three-dimensional viscous analysis of four low aspect ratio transonic rotors that demonstrate the effects of cascade throat area, internal contraction and trailing edge effective camber on compressor performance. The cascade throat area study revealed that tight throat margins result in increased high speed efficiency with lower part speed performance. Stall line was also improved slightly over a wide range of speeds with a lower throat-to-upstream capture area ratio. Higher internal contraction, expressed as throat-to-mouth area ratio, also results in increased design point peak efficiency, but again costs performance at the lower speeds. Reducing the trailing edge effective camber expressed as throat-to-exit area ratio, results in an improvement in peak efficiency level without significantly lowering the stall line. Among all four rotors, the best high speed efficiency was obtained by the rotor with tight throat margin and highest internal contraction, but its efficiency was the lowest at part speed. The best compromise between high speed and part speed efficiency was achieved by the rotor with a large throat and a lower trailing edge effective camber. The differences in the shock structure and the shock boundary layer interaction of the four blades was analyzed using a three-dimensional viscous code. The analytical results are used to supplement the data and provide further insight into the detailed physics of the flow field.

The Design, Development and Evaluation of 3D Aerofoils for High Speed Axial Compressors: Part 1 — Test Facility, Instrumentation and Probe Traverse Mechanism

2005 ◽  
Author(s):  
D. Lippett ◽  
G. Woollatt ◽  
P. C. Ivey ◽  
P. Timmis ◽  
B. A. Charnley
Keyword(s):  
Collaborative Design ◽  
High Speed ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Test Facility ◽  
Mapping Technique ◽  
Efficiency Gain ◽  
Mapping Procedure ◽  
Tunnel Section ◽  
Wide Range

This paper, in two parts, reports measurements from, and simulation of, Cranfield University’s 3-stage high-speed axial compressor. Using this newly built rig, supported by European Commission, a consortium of gas-turbine companies have tested a set of conventionally stacked 2D rotor and stator blades. The results from this experiment were used to evaluate and assess the performance of several commercially available CFD codes leading to the collaborative design of an advanced three-dimensional blade set seeking, if possible, a 2% efficiency gain. The limited axial spacing between the measurement planes and the blade rows required the design of a unique seven probe assembly and traverse mechanism able to yaw and pitch the probes and to control the insertion depths. This mechanism was designed to accommodate different probes, such as cobra, fast response (pneumatic) and temperature measuring probes, and deliver area traverses between rotor and stators throughout the compressor. For probe calibration a high speed wind tunnel section was designed to accommodate this mechanism enabling calibrations for Mach numbers up to 0.78, as well as for a wide range of pitch and yaw angles values. This mechanism combined with a post processing programme incorporating a mapping technique for the relative offset of the measurement points on the probe secured very detailed results throughout the compressor. Measurements show the complex three dimensional flow structure and secondary flows associated with tip-leakage, endwall boundary layers, wake transportation and blade row interactions. The importance of a rigorous mapping procedure was particularly useful where the wake thickness was small and pressure gradients high in comparison to the probe size.

A Comprehensive Through-Flow Solver Method for Modern Turbomachinery Design

2015 ◽  
Author(s):  
Mark R. Anderson ◽  
Daryl L. Bonhaus
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Optimization Techniques ◽  
Navier Stokes ◽  
Computationally Efficient ◽  
Dimensional Solution ◽  
Loss Model ◽  
Flow Solver ◽  
Through Flow ◽  
Wide Range

Through-flow solvers have historically played a very prominent role in the design and analysis of axial turbomachinery. While three-dimensional, Full Navier-Stokes (FNS) CFD is taking an increasing larger role, quasi-3D through-flow methods are still widely used. Automated optimization techniques that search over a wide design space, involving many possible variables, are particularly suitable for the computationally efficient through-flow solver. Pressure-based methods derived from CFD solution techniques have gradually replaced older streamline curvature methods, due to their ability to capture flow across a wide range of Mach numbers, particularly the transonic and supersonic regimes. The through-flow approach allows for the solution of the three-dimensional problem with the computational efficiency of a two-dimensional solution. Since the losses are explicitly calculated through empirically based models, the need for detailed grid resolution to capture tiny flow entities (such as wakes and boundary layers) is also greatly reduced. The combined savings can result in computational costs as much as two orders of magnitude lower than full 3D CFD methods. A state-of-the-art through-flow solver has several features that are crucial in the design process. One of these is the ability to run in both a design and an analysis mode. Also important, is the ability to generate solutions where critical components are solved using 3D FNS, while others are run using a through-flow method. Other desirable features in a through-flow solver are: an advanced equation of state, injection and extraction ability, the handling of arbitrary (non-axial) shapes, and a link to a capable geometry generation engine. Through-flow solvers represent a unique mix of higher order numerical methods (increasingly CFD-based) coupled with empirically derived models (generally meanline based). The combination of these two methods in one solver creates a particularly challenging programming problem. This paper details the techniques required to effectively generate through-flow solutions. Special attention is given to an improved off-design loss model for compressors, as well as a transonic loss model needed for high-speed compressor and turbine flows. Validation with recognized test data along with corresponding 3D FNS CFD results are presented.

A Study of Thermohydrodynamic Features of Multi Wound Foil Bearing Using Lobatto Point Quadrature

2008 ◽  
Author(s):  
Kai Feng ◽  
Shigehiko Kaneko
Keyword(s):  
High Speed ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Three Dimensional ◽  
Iteration Process ◽  
Element Model ◽  
Air Bearings ◽  
Foil Bearing ◽  
Deformation Equation ◽  
Wide Range

The applications of foil air bearings, which are recognized to be the best choice for oil free applications, have been extended for use in a wide range of turbo-miachineries with high speed and high temperature. Lubricant temperature becomes an important factor in the performance of foil air bearings, especially at high rotational speeds and high loads or at high ambient temperature. However, most of the published foil air bearing models were based on the isothermal assumption. This study presents a thermohydrodynamic analysis (THD) of Multi Wound Foil Bearing (MWFB), in which the Reynolds’ equation is solved with the gas viscosity as a function of temperature that is obtained from the energy equation. Lobatto point quadrature, which was proposed by Elrod and Brewe and introduced into compressible calculation by Moraru and Keith, is utilized to accelerate the iteration process with a sparse mesh across film thickness. A finite element model of the foil is used to describe the foil elasticity. An iterative procedure is performed between the Reynolds’ equation, the foil elastic deformation equation and the energy equation, until the convergence is achieved. A three-dimensional temperature prediction of air film is presented and a comparison of THD to isothermal results is made to emphasize the importance of thermal effects. Finally, published experimental data are used to validate this numerical solution.

scholarly journals Biomechanical factor affecting Baseball Pitching Velocity

2019 ◽  
Author(s):  
Yasushi Ota ◽  
Ryoga Kuriyama
Keyword(s):  
High Speed ◽  
Time Series Data ◽  
Three Dimensional ◽  
The Body ◽  
Lower Limbs ◽  
Whole Body ◽  
Series Data ◽  
Physical Factors ◽  
Body Parts ◽  
Joint Force

In baseball, pitchers have a central role and high-speed pitching is desirable. So far, several studies of the physical factors related to pitching form with the aim of improving the speed of pitched balls have been conducted. In this study, we used a motion capture to acquire three-dimensional (3D) time series data related to the speed of pitched balls and performed a kinetics analysis by using these acquired data. The acquired data were divided into five pitching phases: wind up, early cocking, late cocking, acceleration, and follow through. Our analysis identified the body parts that contribute to increasing the speed of pitched balls, i.e., the speed of rotation of individual joints and the timing/phase when power can be applied. Especially, by examining joint angular velocity and joint force, we showed that the speed of pitched balls is determined by the action of the upper limbs as well as the coordinated action of the whole body, particularly the lower limbs and the trunk.

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