Accession Number : ADA265159


Title :   Unsteady Flow Past a NACA 0012 Airfoil Pitching at Constant Rates


Descriptive Note : Final rept. 1 Nov 1988-31 Oct 1992


Corporate Author : FLORIDA AGRICULTURAL AND MECHANICAL UNIV TALLAHASSEE


Personal Author(s) : Lourenco, Luiz M ; Krothapalli, A ; Van Dommelen, L ; Shih, C


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a265159.pdf


Report Date : 13 Apr 1993


Pagination or Media Count : 83


Abstract : The dynamic stall process of a NACA 0012 airfoil undergoing a constant-rate pitching up motion is studied experimentally in a water towing tank facility. This study focuses on the detailed measurement of the unsteady separated flow in the vicinity of the leading and trailing edges of the airfoil. The measurements are carried out using the Particle Image Velocimity (PIV) technique. This technique provides the two-dimensional velocity and associated vorticity fields, at various instants in time, in the mid-span of the airfoil. Near the leading edge, large vortical structures emerge as a consequence of Van Dommelen and Shen type separation and a local vorticity accumulation. The interaction of these vortices with the reversing boundary layer vorticity initiates a secondary flow separation and the formation of a secondary vortex. The mutual induction of this counter-rotating vortex pair eventually leads to the ejection process of the dynamic stall vortex from the leading edge region.


Descriptors :   *PITCH(MOTION) , *UNSTEADY FLOW , VELOCITY , INTERACTIONS , LAYERS , WATER , STRUCTURES , RATES , VORTICES , REGIONS , FLOW SEPARATION , ACCUMULATION , LEADING EDGES , EJECTION , SEPARATION , IMAGES , CONSTANTS , PARTICLES , TIME , COUNTERS , SECONDARY FLOW , TOWING , VANS , TRAILING EDGES , AIRFOILS , BOUNDARY LAYER , MOTION , FACILITIES , TWO DIMENSIONAL , DYNAMICS , MEASUREMENT


Subject Categories : Fluid Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE