Author: Daniel C. Daley (MAJ, USAF.)
Publisher:
ISBN:
Category : Lift (Aerodynamics)
Languages : en
Pages :

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Author: Scott J. Schreck (1LT, USAF.)
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 266

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Author: D. C. Daley
Publisher:
ISBN:
Category :
Languages : en
Pages : 82

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This thesis discusses an experimental investigation of dynamic stall for an NACA 0015 airfoil rotated at different constant angular rates. It describes a microcomputer-based automatic data acquisition system capable of acquiring 1000 items of data per second. When this information was used to predict stall and compared with film-data stall indications of the same test runs, there was excellent correlation between them. Results of the investigation showed a consistent correlation between the stall angle at dynamic conditions and the nondimensionalized angular rate. Experimental data was obtained for non-dimensional angular rates (defined as one half the chord times the angular rate divided by free stream velocity) in the range of .005 to .06. (Author).

Author: Katie Kristine Thorne
Publisher:
ISBN:
Category :
Languages : en
Pages : 101

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Author: S. J. Schreck
Publisher:
ISBN:
Category :
Languages : en
Pages : 147

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Flow over an NACA 0015 airfoil undergoing a constant rate of change of angle of attack was experimentally studied over a range of tunnel speeds and rotation rates. Surface pressure transducers coupled with a microcomputer-based data acquisition system were used to collect surface-pressure data at the rate of 4000 samples per second; data reduction was also microcomputer-based. Data was reduced in two forms: (1) C sub l versus alpha curves through stall were determined for each dynamic experimental configuration. This was accomplished by numerical integration of pressure data at a number of angles through stall, each data point representing the average of five experiments at the same experimental conditions. These curves indicated a slight decrease in C sub l - alpha slope with increasing angle of attack angular rate. (2) Increase in stall angle of attack of the dynamic over the static case was plotted against a nondimensional angular rate parameter (defined as the product of one-half the chord length and angular rotation rate, divided by the freestream velocity). This comparison gave rise to an apparently universal curve of nondimensional angular rotation rate versus increase in stall angle of attack. This curve was in agreement in some sense with previous experiments using stall indicators other than the actual stall.

Author: Md. Ahsanul Karim
Publisher:
ISBN:
Category :
Languages : en
Pages : 322

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Author: Robin Bryant Gray
Publisher:
ISBN:
Category : Stalling (Aerodynamics)
Languages : en
Pages :

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Author: John Gordon Leishman
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Kyle C. Heintz
Publisher:
ISBN:
Category :
Languages : en
Pages : 179

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Author: Myung J. Rhee
Publisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 112

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Book Description
The purpose of this study is to examine the previously unpublished instantaneous pressure data of the Aeroflightdynamics Directorate Two-Dimensional (2D) and Three-Dimensional (3D) Oscillating Wing Experiment to better understand the process of dynamic stall vortex development on the NACA 0015 airfoil. This report presents representative 2D instantaneous pressure data for the upper and lower surfaces of the airfoil at various chordwise locations obtained at specific angles of attack during upstroke and downstroke cycles. Furthermore, the report contains a complete set of plots of instantaneous pressure distributions for the upper surface for all the 2D data sets obtained in the experiment. First, the lift, drag and pitching moment data of various testing conditions are reviewed and analyzed to classify the data both with and without a boundary layer trip into "no stall," "moderate stall," and "deep stall" data. Next, instantaneous pressure distributions on the upper surface of the airfoil are examined for the study of vortex development. The lift and pitching moment data are analyzed to document the dynamic overshoot which delays the development of the stall on the airfoil. Next, the range of angles of attack are selected where the lift and pitching moment data shows significant changes from unsteady flow behavior daring oscillation cycles. Furthermore, based on the unsteady flow characteristics found in each classification of dynamic stall, analysis is continued to identify the conditions where the reduced frequency clearly affects the unsteady flow behavior of the airfoil during the oscillation. This can result in a change of the dynamic stall classification of the airfoil response under various unsteady flow conditions. These conditions are discussed in detail in the comparative studies.