Author
Shukry K. Ibrahim
Bio: Shukry K. Ibrahim is an academic researcher. The author has contributed to research in topics: Spherical shell & Added mass. The author has an hindex of 1, co-authored 1 publications receiving 24 citations.
Topics: Spherical shell, Added mass, Potential flow
Papers
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TL;DR: In this paper, the fundamental aerodynamic problem of the steady, potential flow about the idealized parachute and the related dynamic problem of its added mass in unsteady motion are treated analytically.
Abstract: (p, 0) z) =
24 citations
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TL;DR: In this paper, a dynamic inflation model for parachutes is presented, which predicts increased dimensionless inflation times and increased dimensioness inflation forces observed at high altitudes at high altitude.
Abstract: This paper describes a dynamic inflation model for parachutes which predicts increased dimensionless inflation times and increased dimensionless inflation forces observed at high altitudes. As altitude is increased, greater relative parachute inertia results in increased inflation times, and greater relative total system inertia results in increased maximum inflation forces. The effect of Mach number on inflation force is also predicted by the inflation model.
45 citations
TL;DR: In this article, the dynamics of flexible parachute canopies and vortex shedding in their near wake were studied experimentally in a water tunnel, where the velocity field was measured by particle image velocimetry for two different canopy diameters.
Abstract: The dynamics of flexible parachute canopies and vortex shedding in their near wake are studied experimentally in a water tunnel. The velocity field was measured by particle image velocimetry for two different canopy diameters. The periodic oscillation of the canopy diameter about a mean value which is referred to as ‘breathing’ has a non-dimensional frequency, based on the free-stream velocity and the mean canopy projected diameter, of approximately 0.55 for the range of Reynolds numbers examined. The dimensionless breathing frequency observed in the experiments is consistent with the values for larger canopies. The shear layer emanating from the canopy rolls up and sheds symmetric vortex rings. The frequency of vortex shedding was measured to be the same as the canopy breathing frequency. This Strouhal number is unique in the sense that it is much higher than those associated with rigid axisymmetric bluff bodies such as disks and spheres. The canopy breathing is shown to stem from the cyclical variation of suction pressure, resulting from the passage of vortex rings, on the exterior surface of the canopy. The added mass associated with the breathing of the canopy is found to be accountable for up to 40 % of the canopy drag fluctuations in the range of parameters investigated.
40 citations
TL;DR: In this paper, a water channel on the starting flow around several bluff bodies with sharp edges was investigated using the hydrogen bubble technique and threefold structures of the starting vortex behind flat plates were observed.
Abstract: Experimental investigations were made in a water channel on the starting flow around several bluff bodies with sharp edges: flat plates, circular disks and hollow hemispheres. Details of the flow structures were visualized using the hydrogen bubble technique. Three-fold structures of the starting vortex behind flat plates were observed. The shedding of the vortex sheet from the edge was also studied.
36 citations
TL;DR: In this paper, the authors defined the drag coefficient based on S CDS -drag area of fully inflated fully inflated parachute, ft2 d = constructed parachute diameter across base of conical parachute, msl, ft j£t = outflow coefficient (approximately 0.6) Ki = inflow coefficient (a value o^f 0.7 is used for a first approximation, and adjusted as determined by experimental data) Lr = circumferential length of reefing line.
Abstract: Nomenclature CD = drag coefficient based on S CDS — drag area of fully inflated parachute, ft2 (CiwS)r == drag area of reefed parachute, ft2 d = constructed parachute diameter across base of conical parachute, ft Di = inflated diameter, f d, ft hr — release altitude, msl, ft j£t = outflow coefficient (approximately 0.6) Ki = inflow coefficient (a value o^f 0.7 is used for a first approximation, and adjusted as determined by experimental data) Lr = circumferential length of reefing line, ft AP = pressure across canopy, lb/ft2 q = dynamic pressure JpF2, lb/ft2 R = radius of canopy during inflation normal to mean local canopy contour, ft Rm = maximum inflated radius of canopy, ft (approximately | of constructed radius) RQ = initial radius of canopy at start of inflation, ft (radius of suspension lugs or pack radius) s = tensile stress, lb/ft2 S = area of base of conical chute, 7rd2/4, ft2 t = thickness of ribbon, ft if = filling time, sec T — ribbon tensile load, Ib V = vehicle velocity, fps Fo = vehicle velocity at start of parachute filling, fps w = ribbon width, ft W = vehicle weight, Ib XG = geometric porosity of canopy p = air density, slugs/ft3
31 citations
26 Apr 2002
TL;DR: In this article, the authors present a table of acknowledgements and acknowledgements of the authors of this paper. But they do not discuss the authorship of the paper's authors.
Abstract: .............................................................................................................................. ii Acknowledgements............................................................................................................. ii Table of
30 citations