On the rolling-up of the conical vortex sheet above a delta wing

The flow field near the centre of a rolled-up vortex sheet

: Measurements of the unsteady forces on heaving delta wing hydrofoils hydrofoils having apex angles of 15 and 30 deg were carried out in fully wetted flow, planing at a free surface, and with forced ventilation. The fully wetted dynamic measurements were in good agreement with the results of lifting surface theory at small angles of attack. A slender body theory of planing due originally to Tulin is extended to account for non-steady motions. This theory generally underestimates the in-phase lift force; the quadrature unsteady lift is well predicted by the theory. Additional measurements of steady planing delta wings were carried out; for small apex angles and small angles of attack the theory is found to be adequate though it does appear to underestimate the lift somewhat. Some additional experiments on non-steady forces on two- dimensional fully wetted and fully cavitating hydrofoils were also carried out.

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Experimental investigation of non-steady forces on hydrofoils oscillating in heave

: The low-speed performance of a high span loading aircraft depends critically on the structure and stability of the vortex flow field created by the wing Conventional formulation of lifting surface theory is not adequate to handle the low-aspect-ratio wing problem since the leading edge vortices add several complications Specifically, the nonplanar nature of the vortex sheet may have to be considered explicitly, the leading-edge loading is altered, and vortex breakdown is a rotational phenomenon Due to those additional difficulties, a study was made of the state of the art in vortex-wing interactions

On the Development of a Unified Theory for Vortex Flow Phenomena for Aeronautical Applications

LARGE AMPLITUDE PITCHING OF SUPERMANEUVER DELTA WINGS INCLUDING FLOW CONTROL Yahia A. Abdelhamid Old Dominion University, 1999 Director: Dr. Osama A. Kandil The unsteady, three-dimensional Navier-Stokes equations are solved to simulate and study the aerodynamic response o f a delta wing undergoing large amplitude pitching motion up to 90° angle o f attack. The primary model under consideration consists of a 76° swept, sharp-edged delta wing of zero thickness, initially at zero angle o f attack. The ffeestream Mach number and Reynolds number are 0.3 and 0.45 x 106, respectively. The governing equations are solved time-accurately using the implicit, upwind, Roe fluxdifference splitting, finite-volume scheme. Both laminar and turbulent flow solutions are investigated. In the laminar flow solutions, validation o f the computational results is carried out using existing experimental data, and shows good agreement. The effect o f reduced frequency o f the wing motion is then presented and a grid refinement study is introduced. In the turbulent flow simulations, both Baldwin-Lomax and Spalart-Allmaras turbulence models are used and the results are compared with those o f the laminar solution and experimental data as well. A sinusoidal pitching motion of the wing is also investigated in the present work. The computational results provide complete information and details about the flowfield response, which are difficult to Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. obtain from experiment. A feasibility study o f using one o f the flow control techniques, blowing, to enhance maneuverability is introduced. The investigation o f the unsteady flow over a wide range o f angles of attack provides crucial understanding o f the variations o f the leading edge vortex cores, their breakdown behavior, aerodynamic hysteresis, and wing aerodynamic characteristics at very high angle o f attack. The current study shows that numerical simulations in the very high angle o f attack range are obtainable. Such calculations were thought to be unattainable as recently as the 1980’s. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS Praise and thanks are due to GOD to whom I owe everything I would like to express my sincere thanks and gratitude to my advisor, Professor Osama A. Kandil, Eminent Scholar o f Aerospace Engineering, for his advice and encouragement during the course o f this research work. Without his support I wouldn’t have been able to finish this work. Special thanks are extended to the members o f my dissertation committee, Prof. Colin P. Britcher and Prof. Brett A. Newman o f the Aerospace Engineering Department at Old Dominion University and Dr. Tin-Chee Wong, for their review o f this dissertation. I would like also to express my love, gratitude and appreciation to my parents, my wife, Abir, and my children, Omar and Asmaa, for their continuous support, encouragement and patience. This research work has been supported partially by the Unsteady Aerodynamics Branch o f NASA Langley Research Center under NASA Grant No. NAG-1-648. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

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Large Amplitude Pitching of Supermaneuver Delta Wings Including Flow Control

Deployment of a tethered satellite system is the process of separating the two end bodies by spooling out the tether connecting them. In this paper, a 3D dynamic model of a tethered satellite was established. Three typical deploying parameters were chosen and discussed according to some correlative references, thus obtaining the changing law for the percentage of deployment. The numerical results show the process of deployment is much sensitive with the in-plane angle, and the stable points are prior to others in long-distance deployment considering energy needed. These results could provide ideas about systemic design and engineering practice for tethered satellite.

On the rolling-up of the conical vortex sheet above a delta wing

Citations

The flow field near the centre of a rolled-up vortex sheet

Experimental investigation of non-steady forces on hydrofoils oscillating in heave

On the Development of a Unified Theory for Vortex Flow Phenomena for Aeronautical Applications

Large Amplitude Pitching of Supermaneuver Delta Wings Including Flow Control

Research of Dynamics and Deploying Control Method on Tethered Satellite

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