טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBen-Gida Hadar
SubjectLeading-Edge Vortex as a High-Lift Mechanism for Large
Aspect Ratio Wings
DepartmentDepartment of Aerospace Engineering
Supervisors Research Professor E Daniel Weihs
Professor Roi Gurka
Full Thesis textFull thesis text - English Version


Abstract

A stationary leading-edge-vortex (LEV) formed over the upper wing surface is a possible primary mechanism to achieve high lift force on wings. Thus far, several analytical attempts were made to investigate the formation of stationary LEVs over high AR wings, mainly through the development of simplified two-dimensional models. Although some insight was provided, these models did not provide sufficient means to fully understand the physical mechanisms behind the phenomenon, nor they can account for its three-dimensional nature.

This thesis investigates the potential flow modeling of a stationary LEV above a high AR wing for lift enhancement. The main objective is to study and characterize the phenomenon for designing large AR wings with high lift due to the LEV. The novelty of the flow model we developed is in the three-dimensional aspects of the LEV, which are considered in two ways: i) satisfying conservation of mass and vorticity within the LEV core; ii) using a combination of both the strip theory and conservation conditions to account for the interaction of the wing shape with the formation of the stationary LEV.

Flow visualization measurements are conducted, using the Particle Image Velocimetry (PIV) technique, for a swept back wing configuration with aspect ratio of 6, parabolic quarter-chord curve and elliptical chord distribution. A good agreement is shown between the prediction of the pseudo-three-dimensional flow model and the experimental results in terms of the resulted sectional flow field, stationary LEV location and circulation magnitude distribution along the wingspan. The results presented shed extensive insight on the physical mechanisms responsible for generating and maintaining a stationary LEV structure on a non-slender wing. We suggest the flow model to serve as a preliminary tool in designing new high AR wings that utilize the stationary LEV phenomenon to improve performance at high angles of attack.