Aerodynamic characteristics and flow round cross parachutes in steady motion

Shen, Chen; Cockrell, D. J.

doi:10.2514/6.1986-2458

Cited by 12 publications

(5 citation statements)

References 2 publications

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“…We have already said that the wing operates more like a parachute than a conventional wing at this stage of the manoeuvre, and given its spread-eagled posture, the bird may be roughly approximated as a cross parachute (Shen and Cockrell, 1988), with the cross extending wing tip to wing tip and head to tail. The flow characteristics of cross parachutes typically involve relatively high powered jets between the parachute arms (Fig.·9), with the flow near the tips of the canopy arms remaining attached but with separation nearer the crossing point of the arms being encouraged by the jets between them.…”

Section: Table·3 Timing Of Lesser Underwing Covert Feather Deflectiomentioning

confidence: 99%

Automatic aeroelastic devices in the wings of a steppe eagleAquila nipalensis

Carruthers

Thomas

Taylor

2007

Journal of Experimental Biology

136

143

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SUMMARY Here we analyse aeroelastic devices in the wings of a steppe eagle Aquila nipalensis during manoeuvres. Chaotic deflections of the upperwing coverts observed using video cameras carried by the bird (50 frames s–1) indicate trailing-edge separation but attached flow near the leading edge during flapping and gust response, and completely stalled flows upon landing. The underwing coverts deflect automatically along the leading edge at high angle of attack. We use high-speed digital video (500 frames s–1) to analyse these deflections in greater detail during perching sequences indoors and outdoors. Outdoor perching sequences usually follow a stereotyped three-phase sequence comprising a glide, pitch-up manoeuvre and deep stall. During deep stall, the spread-eagled bird has aerodynamics reminiscent of a cross-parachute. Deployment of the underwing coverts is closely phased with wing sweeping during the pitch-up manoeuvre,and is accompanied by alula protraction. Surprisingly, active alula protraction is preceded by passive peeling from its tip. Indoor flights follow a stereotyped flapping perching sequence, with deployment of the underwing coverts closely phased with alula protraction and the end of the downstroke. We propose that the underwing coverts operate as an automatic high-lift device, analogous to a Kruger flap. We suggest that the alula operates as a strake, promoting formation of a leading-edge vortex on the swept hand-wing when the arm-wing is completely stalled, and hypothesise that its active protraction is stimulated by its initial passive deflection. These aeroelastic devices appear to be used for flow control to enhance unsteady manoeuvres, and may also provide sensory feedback.

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Section: Table·3 Timing Of Lesser Underwing Covert Feather Deflectiomentioning

confidence: 99%

Automatic aeroelastic devices in the wings of a steppe eagleAquila nipalensis

Carruthers

Thomas

Taylor

2007

Journal of Experimental Biology

136

143

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“…In the first eigenmode both parachute and payload oscillate into the same direction, and in the other eigenmode they oscillate in opposite directions. The dominant parameter of the complex eigenfrequency is the static stability of the parachute that depends on the parachute geometry (aspect ratio, arm ratioCockrell and Shen 14 ). The lower eigenmode has small damping over the full range of the static stability.…”

Section: Discussionmentioning

confidence: 99%

Dynamic investigation of the angular motion of a rotating body-parachute system

Levin

Shpund

1995

Journal of Aircraft

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The modern design of parachute-pay load systems that undergo specific trajectories has to cope with dynamic behavior characteristics, which were of secondary importance in the past. Static and dynamic measurements, as well as computational simulations, are being employed to help the designers in converging to an optimal solution. However, some aerodynamic dynamic data are often impossible to obtain either computationally or experimentally through direct measurement. Novel experimental techniques have to be implemented in order to expand the analysis capability or to validate the design of specific configurations. A test technique that allows three degrees of freedom for investigating experimentally the dynamic behavior of parachute-payload systems is presented in this article. The system is utilized to investigate the effect of the parachute geometrical variables on the dynamic stability of the parachute-payload system. The cross-type parachute-payload systems that were tested exhibit three zones of different dynamic stability modes and the occurrence of dynamic instability for statically stable configurations. These results show the need for obtaining more dynamic data for the complete understanding of the dynamic behavior of closely coupled parachute-payload configurations.

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“…The guide surface 4 parachute has good stability but complex in shape, geometry and inferior drag efficiency. Cruciform [5][6] or crosstype 7 parachute requires more suspension lines to maintain the shape and size, bringing in packing complexity and rotational possibility during operation. besides, it adds more cost and chances of line entanglements.…”

Section: Introductionmentioning

confidence: 99%

Computational and Experimental Study for Reducing Forebody Wake Effect by Proper Designing of a Slit cut Square Parachute used for Sonobuoy Drop

et al. 2021

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This paper discusses the design of a square parachute based on classical approach, computational analysis and experimentation. This parachute will be used to drop directional sonobuoy on the sea to locate and classify the submarines. Design improvements are brought out by providing slits into a solid square canopy of parachute to bring in more stability and minimum drift during descend. Specifically, the effect of upstream sonobuoy, RANS model, suspension line length, canopy size and slit size in flow structure were considered. The predicted drag coefficients obtained from CFD for square canopy with slit-cuts compared with the results of wind tunnel experiment and found that the increase in the suspension-line length and/or of the surface area of the parachute canopy helps in better stability and results in the minimum drag loss.

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Aerodynamic characteristics and flow round cross parachutes in steady motion

Cited by 12 publications

References 2 publications

Automatic aeroelastic devices in the wings of a steppe eagleAquila nipalensis

Automatic aeroelastic devices in the wings of a steppe eagleAquila nipalensis

Dynamic investigation of the angular motion of a rotating body-parachute system

Computational and Experimental Study for Reducing Forebody Wake Effect by Proper Designing of a Slit cut Square Parachute used for Sonobuoy Drop

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