Accession Number : ADA194650

Title :   Unsteady Flow Past an NACA 0012 Airfoil at High Angles of Attack.

Descriptive Note : Technical rept. Jul 86-Dec 87,

Corporate Author : FLORIDA AGRICULTURAL AND MECHANICAL UNIV TALLAHASSEE FLUID MECHANICS RESEARC H LAB

Personal Author(s) : Krothapalli, A ; Lourenco, L ; Van Dommelen, L

PDF Url : ADA194650

Report Date : 02 Mar 1988

Pagination or Media Count : 26

Abstract : A whole field experimental technique, commonly referred to as Particle Image Velocimetry, was used for the measurement of the instantaneous two-dimensional velocity fields about an impulsively started NACA 0012 airfoil at high angles of attack. The velocity field was measured with sufficient accuracy, such that the time evolution of the vorticity field was obtained. The experiments were performed in a towing at a Reynolds number of 1400, based on the chord of the airfoil. For angles of attack greater than about 20 deg, the flow field at the upper surface of the airfoil show large scale vortical motions with the following time dependent scenario. At the initial stages of the airfoil startup, a separation bubble at the leading edge was generated and with time, it grows into an isolated primary vortex which dominated the whole flow field. Trailing behind this primary vortex were two counter rotating vortices. This multiple vortex structure grow together and move along the upper surface until it reaches the trailing edge. At this time, the primary vortex induces a trailing edge vortex. The primary and trailing edge vortices then form the wake flow field.

Descriptors :   *AIRFOILS, *ANGLE OF ATTACK, *UNSTEADY FLOW, ACCURACY, COUNTERROTATION, EDGES, HIGH ANGLES, LEADING EDGES, SCENARIOS, TIME, TRAILING EDGES, TRAILING VORTICES, TWO DIMENSIONAL, VELOCIMETERS, VELOCITY, WAKE, AERODYNAMIC LOADING, NAVIER STOKES EQUATIONS

Subject Categories : Aircraft
      Aerodynamics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE