Author: Lakshmendra Shanker SaxenaPublisher:
ISBN:
Category :
Languages : en
Pages : 213
Book Description
An Experimental Investigation of Oscillating Flows Over an Airfoil
Author: Lakshmendra Shanker SaxenaPublisher:
ISBN:
Category :
Languages : en
Pages : 213
Book Description
An Experimental Investigation of Flow Over an Oscillating Airfoil
Author: Panayiote GerontakosPublisher:
ISBN:
Category :
Languages : en
Pages : 218
Book Description
"The detailed behaviour of the unsteady boundary layer and stall events occurred on a sinusoidally oscillating NACA 0012 airfoil at Re = 1.35 x 105 was investigated experimentally by using closely-spaced multiple hot-film sensor arrays. The hot-film measurements were supplemented by surface pressure measurements, hot-wire wake velocity surveys and smoke-flow visualizations. Three typical oscillation parameters: attached flow, light stall, and deep stall were tested. Special attention was focused on the non-intrusive identification of the spatial-temporal progression of the locations of the boundary-layer transition and separation and reattachment points for a range of oscillation frequencies and amplitudes both prior to, during, and post the stall. The results show that for an unsteady airfoil, the reduced frequency of the oscillation was found to be highly significant and only small values of reduced frequency were required to delay the onset of the various boundary-layer events, and to produce significant variations and hysteresis in the peak values of lift and drag forces and the pitching moments, which are fundamentally different from their static counterparts. Lift stall was observed to occur when the leading-edge vortex reached 90% of the chord, while moment stall occurred at the end of the upward spread of the trailing-edge flow reversal. The convection speed of the leading-edge and the secondary vortices were also reported. Dynamic stall was found to be caused by an abrupt turbulent separation near the leading-edge region and not with the bursting of the laminar separation bubble, as is commonly observed for a static NACA 0012 airfoil; the result being the initiation, growth and convection of an energetic leading-edge vortex. Moreover, the detection of the sudden turbulent breakdown could serve as an indicator for dynamic stall detection and control. The results reported on here provide a deepened insight into the detailed nature of" --
Theoretical and Experimental Investigation of the Effect of Tunnel Walls on the Forces on an Oscillating Airfoil in Two-dimensional Subsonic Compressible Flow
Author: A. E. PotterPublisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 358
Book Description
Theoretical and Experimental Investigation of the Effect of Tunnel Walls on the Forces on an Oscillating Airfoil in Two-dimensional Subsonic Compressible Flow
Author: Harry L. RunyanPublisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 50
Book Description
This paper presents a theoretical and experimental investigation of the effect of wind-tunnel walls on the air forces on an oscillating wing in two-dimensional subsonic compressible flow. A method of solving an integral equation which relates the downwash on a wing to the unknown loading is given, and some comparisons are made between the theoretical results and the experimental results. A resonance condition, which was predicted by theory in a previous report (NACA Rep. 1150), is shown experimentally to exist. In addition, application of the analysis is made to a number of examples in order to illustrate the influence of walls due to variations in frequency of oscillation, Mach number, and ratio of tunnel height to wing semichord.
Experimental Investigation of Flow Structures Around an Oscillating Airfoil in Steady Current
Author: İdil FenercioğluAn Experimental Investigation of a Low Frequency Flow Oscillation Over a Low Reynolds Number Airfoil Near Stall
Author: Douglas Carl HeinrichPublisher:
ISBN:
Category :
Languages : en
Pages : 230
Book Description
An Experimental and Computational Investigation of Oscillating Airfoil Unsteady Aerodynamics at Large Mean Incidence
Author: Publisher: DIANE Publishing
ISBN: 1428995161
Category :
Languages : en
Pages : 42
Book Description
A Computational and Experimental Investigation of the Propulsive and Lifting Characteristics of Oscillating Airfoils and Airfoil Combinations in Incompressible Flow
Author: Kerry S. NeaceExperimental Investigation of a Supercritical Airfoil Oscillating in Pitch at Transonic Flow
Author: Cornelia HillenhermsPublisher:
ISBN: 9783832220143
Category :
Languages : en
Pages : 148
Book Description
Experimental Investigation of an Oscillating Flow Generator
Author: Cogan S. SemlerPublisher:
ISBN:
Category : Hydrodynamics
Languages : en
Pages : 47
Book Description
The objective of this project was to construct and test a device that can transform fluid flow into the continuous oscillatory linear motion of a hydro/airfoil. This device may be used to generate power from a renewable energy source such as tidal flow or wind power. The device was constructed in the NPS machine shop. It consisted of a flat plate that is mounted on two rail guides such that it can execute a linear back-and-forth motion. The blade oscillation is flow induced due to the lift and the moment generated on the flat plate in such a way that the plate reverses direction at the stroke endpoints without active control. Tests in two water channels and one towing tank showed that flow-induced blade oscillation could be achieved for certain combinations of flow speed, blade size and pitch axis location. It is concluded that additional testing is warranted to further develop and gain understanding of this technology and its possible application to renewable power generation.