Transition and Turbulence Structure in the Boundary Layers of an Oscillating Airfoil PDF Download
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Author: J. DeRuyck Publisher: ISBN: Category : Languages : en Pages : 102
Book Description
Objectives of this investigation were: 1) to identify the conditions under which a sinusoidally oscillating NACA 0012 airfoil operates with a leading edge separation bubble and the conditions under which it operates with leading edge stall; 2) to conduct complete boundary layer and near wake survey in the presence of the leading edge separation bubble; and 3) to investigate the flow near the trailing edge and in the near wake while the airfoil was undergoing leading edge stall. The airfoil oscillates about an axis at 25% chord from the leading edge, with a nominal reduced frequency of 0.3 and Reynolds number of 300,000. Experiments were made at 4 to 14, 5 to 15, 6 to 16 and 8 to 18 deg angle of attack. It was found that the most probable cause of leading edge stall was due to the leading edge separation bubble burst which occurred soon after static stall limit was exceeded. Leading edge stall is not due to the rapid upstream movement of the trailing edge separation. The velocity vectors and the Reynolds stress tensors were measured using a slanted rotating single sensor hot-wire. The complete suction side boundary layer profile and the near wake was surveyed at 5-15 deg oscillation where no interaction is observed between leading edge and trailing edge flows. Keywords: Unsteady aerodynamics; Dynamic stall; High angle of attack; Flow separation; Rotorcraft; Wake; Unsteady flow transition; Belgium. (EDC).
Author: J. DeRuyck Publisher: ISBN: Category : Languages : en Pages : 102
Book Description
Objectives of this investigation were: 1) to identify the conditions under which a sinusoidally oscillating NACA 0012 airfoil operates with a leading edge separation bubble and the conditions under which it operates with leading edge stall; 2) to conduct complete boundary layer and near wake survey in the presence of the leading edge separation bubble; and 3) to investigate the flow near the trailing edge and in the near wake while the airfoil was undergoing leading edge stall. The airfoil oscillates about an axis at 25% chord from the leading edge, with a nominal reduced frequency of 0.3 and Reynolds number of 300,000. Experiments were made at 4 to 14, 5 to 15, 6 to 16 and 8 to 18 deg angle of attack. It was found that the most probable cause of leading edge stall was due to the leading edge separation bubble burst which occurred soon after static stall limit was exceeded. Leading edge stall is not due to the rapid upstream movement of the trailing edge separation. The velocity vectors and the Reynolds stress tensors were measured using a slanted rotating single sensor hot-wire. The complete suction side boundary layer profile and the near wake was surveyed at 5-15 deg oscillation where no interaction is observed between leading edge and trailing edge flows. Keywords: Unsteady aerodynamics; Dynamic stall; High angle of attack; Flow separation; Rotorcraft; Wake; Unsteady flow transition; Belgium. (EDC).
Author: J. de Ruyck Publisher: ISBN: Category : Languages : en Pages : 91
Book Description
The main objective of this work is to provide experimental information about velocity fields and turbulence structures in unsteady flows. A NACA 0012 airfoil oscillates around an axis at 25% chord distance from the leading edge, with a sinusoidal motion. Instantaneous distributions of velocity as well as all non-zero Reynolds stresses are determined in the profile boundary layers. Measurements are performed at various incidences, from non-stalled to deep stalled flow conditions. The reduced frequency is 0.3 at a chord Reynolds number of 300,000. A slanted rotating hot wire is used and the angular calibration characteristics of the wire are applied in order to detect and measure reversed flows. Instantaneous detailed flow and turbulence patterns of the periodic separation vortex are presented and discussed. These patterns are obtained from traverses at 8 chordwise positions along the suction side of the blade. Keywords include: Data reduction, Computer applications, Oscillating airfoil, Dynamic stall, Experimental velocity fields, and Reynolds stresses.
Author: J. De Ruyck Publisher: ISBN: Category : Languages : en Pages : 89
Book Description
The main objective of the present study is to provide experimental information about turbulence structures in unsteady flow fields. Measurements were made in the wake of a NACA 0012 airfoil oscillating in pitch around an axis at 25% chord distance from the leading edge with a sinusoidal motion. Instantaneous profiles of velocity and all non-zero Reynolds stresses are determined at 48 phase angles within the oscillation period. Measurements were made at .7, 2, 5, 10 and 20% chord downstream of the trailing edge. Various incidences, from zero to just above stall limit, various amplitudes and frequencies were considered.
Author: Josef Ballmann Publisher: Springer Science & Business Media ISBN: 3540448667 Category : Technology & Engineering Languages : en Pages : 396
Book Description
The research work of the collaborative research center SFB401 Flow Modulation and Fluid-Structure Interaction at Airplane Wings at the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen, which is reported in this book, was pos sible due to the financial support of the Deutsche Forschungsgemeinschaft (DFG). The proposal has been approved after evaluation by the referees of DFG selected from other universities and industry, which is gratefully acknowledged. The work is still in progress and now approved to continue until the end of year 2005. More than 50 scientists from universities of the United States, Russia, France, Italy, Japan, Great Britain, Sweden, Netherlands, Switzerland, Austria and research orga nizations NASA, ONERA, NLR, DLR could be invited and have visited the research center, gave seminars on their research on related topics and some of them stayed longer for joined work. Besides its scientific value, also the importance of the pro gram for scientific educa tion becomes evident by looking at the numbers of completed theses, which are up to now about 15 doctoral theses, 40 diploma theses and 70 study theses. The authors of this book acknowledge the valuable support coming from all these persons and institutions. They are especially grateful to the referees having reviewed this work, A. Cohen (Universite Pierre et Marie Curie), J. Cooper (Manchester School of Engineering), W. Devenport (Virginia Tech.), M. Drela (MIT), F. Gern (Avionics Specialties Inc.), A. Griewank (TU Dresden), H. Hönlinger (DLR), P.
Author: J. DeRuyck
Author: J. DeRuyck
Author: J. de Ruyck
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Author: Virgil A. Sandborn
Author: James G.. Brasseur
Author: J. De Ruyck
Author: Josef Ballmann
Author: S.-W. Kim
Author: Graham Gordon Swenson
Author: William John Cook