Accession Number : ADA306705

Title :   A Wind Tunnel Investigation of a Wing-Tip Trailing Vortex.

Descriptive Note : Final technical rept. 1 Jan 93-18 May 95,

Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF AEROSPACE AND OCE AN ENGINEERING

Personal Author(s) : Engel, Mark A. ; Devenport, William J.

PDF Url : ADA306705

Report Date : 25 MAY 1995

Pagination or Media Count : 284

Abstract : The 3'x2' Subsonic Wind Tunnel was used to study a wing-tip trailing vortex during its development at the wingtip and at 10 chordlengths downstream. The vortex was found to be well developed by 10 chordlengths. Helium bubble flow-visualization was used to study the development of the vortex in the near-tip regions. Hot wire anemometry was used to study the vortex at 10 chordlengths. Two vortices were found in the tip-flow studies, a primary vortex formed on the suction side surface of the wingtip and a weaker secondary vortex formed on the endcap. The primary vortex lifts from the surface of the wingtip as it proceed along the chord. The vertical displacement is a strong function of angle of attack. The primary vortex is displaced from the endcap towards the wing root at the trailing edge. The spanwise displacement is a strong function of chord Reynolds number. The primary and secondary vortices co-rotate after leaving the wingtip trailing edge. The primary vortex core follows a steady helical path. The radius of the helical path quickly diminishes with downstream distance. The vortex core was extensively analyzed with a four-sensor quad-hot-wire probe at 10 chordlengths behind the model. Flow visualization showed clearly no visible probe interference with the probe stationed inside, outside, and traversing through the vortex core. The vortex core radius, peak tangential velocity, and core circulation increase with increasing angle of attack. The tangential velocity profiles and axial vorticity profiles indicate the development of inner and outer core regions by 5.0 degrees angle of attack. The regions become increasingly differentiated with increasing angle of attack. The inner and outer core regions appear to be associated with the primary and secondary tip vortices, respectively.

Descriptors :   *TRAILING VORTICES, *FLOW VISUALIZATION, *AERODYNAMIC LIFT, *WING TIPS, VELOCITY, PRESSURE GRADIENTS, MATHEMATICAL MODELS, DISPLACEMENT, BOUNDARY LAYER, TURBULENCE, POWER SPECTRA, COMPUTATIONAL FLUID DYNAMICS, ANGLE OF ATTACK, VORTEX SHEDDING, PRESSURE MEASUREMENT, FLOW FIELDS, WIND TUNNEL TESTS, AERODYNAMIC DRAG, HEURISTIC METHODS, FLOW SEPARATION, REYNOLDS NUMBER, GAS SURFACE INTERACTIONS, ASPECT RATIO, HOT WIRE ANEMOMETERS, AXIAL LOADS, SUBSONIC WIND TUNNELS, POTENTIAL FLOW, SCHLIEREN PHOTOGRAPHY, AXIAL FLOW, TRAILING EDGES, THREE DIMENSIONAL FLOW.

Subject Categories : Aerodynamics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE