UWE Bristol Engineering showcase 2015

Mohd Raffy Fatlly
BEng (Hons) Mechanical Engineering
Project Supervisor
Dr Abdessalem Bouferrouk
A generic overview of aircraft drag reduction
Introduction
Besides having a direct impact on aircraft performance,
drag reduction has a spectrum of positive effects
particularly on the economic viability and environment
sustainability. To illustrate, it has been reported that
fuel consumption contributes approximately 22% of
the Direct Operating Cost (Rennaux, 2004). This means
that even with minor reduction in drag, greatly from
minor reduction in drag, large operational ranges could
be achieved.
Apart from having positive impact on economy, drag
reduction also means low emission of carbon dioxide.
Thus, it is important to realise that the survivability of
future civil aviation would be greatly dependant on the
effort done to sustain the environment in the present.
Theory
Types of drag and its drag contributions
Comparisons of Wing-Tip Devices and Wing-Tip Extensions
Based on the data obtained from a study conducted by Whitcomb (1977), the results
indicate that winglets have better performance as compared to tip extensions. However,
it was only the case with short tip extensions. Quoted from the experimental work done
in 1983, 12% increase in aspect ratio is required in order to decrease the drag by 5%.
Henceforth, this indicates that for the same amount of drag reduction, winglets would
be the best option as winglets would have a smaller and lighter chord than the wing tip.
Project summary
A considerable amount of studies have been carried
out over the past decades concerning the reduction
of aerodynamic drag on civil aircraft
In the context of subsonic flow under cruise
conditions, skin friction account approximately a half
of the total drag while vortex drag contributes about
one third of the total drag
The paper will present a generic overview on the
various concepts of parasitic drag and lift-induced
drag on civil aircraft. A brief summary of each method
will be given and their pros and cons will be discussed
from fluid mechanics points of view.
Project Objectives
The primary objective for this paper to provide a
generic overview on the approaches that have been
proposed to reduce aerodynamic drag particularly on
parasitic drag and lift-induced drag. Furthermore, this
study aims to present the historical background of
each method. Different challenges of each method
will be analysed and comparison of their
performance will be evaluated.
Project Conclusion
It is apparent that two methods have shown great
results in reducing skin friction drag; Hybrid laminar
flow control (HLFC) and riblets have produces a
satisfying level or drag reduction in certain
applications. The use of riblets reduce 2% of drag
while HLFC reduce drag approximately 10%
It can be concluded that Hybrid laminar flow control
is the most promising technique in reducing skin
friction drag. On the other hand, the best approach
to reduce lift-induced drag is by employing wing-tip
devices with (2%) drag reduction. From previous
comparisons, it has been determine that winglets
would be the best option as compared to other
devices.