TITLE:
Selection and Impact of an Aerofoil Leading Edge on Boundary Layer Transition
AUTHORS:
Dinesh Bhatia, Devinder Kumar Yadav, Guangjun Yang, Jian Wang, Henrik Hesse
KEYWORDS:
Boundary Layer Transition, Leading Edge, Aspect Ratio, Curvature, Flow Structure, Adverse Pressure Gradient
JOURNAL NAME:
Journal of Transportation Technologies,
Vol.12 No.4,
October
8,
2022
ABSTRACT: The choice of leading-edge aspect ratio (AR) plays a
crucial role when planning boundary layer wind
tunnel tests on a flat plate. Poor selection of the leading-edge profile
hampers effectiveness of the experiment and increases testing costs associated
with interchanging of leading edges to attain accurate results. Thus, the appropriate selection of the
leading edge is a very crucial part of the wind tunnel experiment process. It
is argued that the curvature of the leading edge
and thus the AR is of paramount importance to achieve accurate results
from the wind tunnel testing. In this project, seven different elliptical leading edges were tested, and
their performance was compared with an ideal leading edge with zero
thickness. Experiments and computation have been done for leading edges ranging
from AR6 to AR20. Results were evaluated for boundary layer transition onset
location, and it was found that AR20 has the
least influence on the flow structure when compared to the ideal leading edge. A study of the flow
structure at the stagnation point indicates an
increase in adverse pressure gradient with an increase in the AR but also shows
a decrease in the size of the stagnation region. The presence of a higher AR
leading edge reduces the turbulent spot production rate, which is one of the primary causes
of boundary layer transition. This paper presents a correlation that enables aerodynamicists to
quantify the impact of the leading-edge AR on transition. A typical case is
also presented to compare the relative performance of a wedge and the higher AR leading
edge, which provides a choice between an elliptical or a wedge-shaped leading edge.