Tip Vortex Manipulation Using a
Sharp Edged Delta Wing
Abstract
By: Justin Slaby1
Adviser: Kenneth D. Visser2
Department of Mechanical and Aeronautical Engineering
Clarkson University
Symposium on Undergraduate Research Experiences August 3, 2006
Oral presentation
One important safety concern of the aircraft industry is the trailing wake and vortex system left
behind as an aircraft moves through the air. This flow field contains strong velocity gradients and
rotational flow components which have been known to upset following aircraft. Trailing vortices are
potentially hazardous because they can persist for many miles and the breakup of these structures is
difficult to predict. Heavier aircraft generate stronger flows and as a result the FAA currently restricts the
distance that a small aircraft (<12,500 lb) may follow a heavy aircraft (>300,000 lb) to 6 miles. This
delay between planes directly affects the amount of air traffic that airports can handle. With air traffic
predicted to triple within the next 20 years, air traffic and airport capacity limits could be substantially
increased if a means were found to safely and reliably disperse these vortex structures in a shorter time
frame.
Past studies have investigated techniques to reduce the strength of the tip vortex and its
subsequent downstream impact.
The theory behind this present study introduces the concept of
generating additional circulation to alter the strength of the tip vortex such that it behaves in a manner
characteristic of a delta wing vortex. Studies have shown that the vortices from a delta wing can
breakdown, or "bursting", which is characterized by an increase in vortex diameter followed by large
scale turbulent dissipation, and a decrease in the core's axial and circumferential velocity. In short, the
vortices from a delta wing can disperse because they are too powerful.
The primary focus of this research was to experimentally investigate in detail the aerodynamic
flow field which results from the introduction of a small, highly swept delta wing tip to the end of a
1
Undergraduate student class 2007, Mechanical and Aeronautical Engineering, Clarkson University, Honors
Program
2
Kenneth D. Visser, Professor, Department of Mechanical and Aeronautical Engineering Clarkson University
Main
Wing
conventional wing.
Delta Wing
Tip Extension
The variables in this study
include the sweep angle, relative angle of attack,
chord length and location (fore or aft) of the wing
Tip Extension
MainAlternate
WingLateral
Position
Sharp-edged
Delta WingAlternate
Angular
Tip Extension
Position
tip, and the angle of attack of the main wing as
illustrated in figure 1.
The hypothesis is that the delta wing vortex
generated by the wing tip will destabilize the
conventional tip vortex structure naturally, such as
with
vortex
breakdown,
and
accelerate
Tip Extension
Alternate
Lateral
Position
Alternate
Angle of Attack
Alternate
Angular
Position
the
dispersion of these vortices. If the conventional tip
Figure 1. Delta wing tip extension
configurations
vortex can be altered by the delta wing tip vortex or made to resemble a delta wing vortex with a
correspondingly high axial core flow velocity, breakdown similar to that observed with a delta
Alternatewing could
Angle of Attack
occur naturally, mitigating conditions downstream.
The primary objective of this research project is to determine whether a configuration that would
accelerate the breakup of the trailing vortex system exists, however, the integration of such a concept on a
real airplane will require the addressing issues such as added weight and deployment capability for such a
device, but can be considered in some future study.
In order to comprehensively test the effects of a delta wing tip on a conventional wing, several
configurations were tested. A total of 12 different wing tips were constructed and tested. For each wing
tip, the main wing was varied through +10 degrees of angle of attack with increments at every 2 degrees.
Additionally, the angle of attack for the delta wing tip relative to the main wing was varied for each angle
of attack for the main wing and each tip. Each tip was varied through ±30 degrees relative angle of attack
at 5 degree increments. This gives a total of 942 configurations that were tested.
To thoroughly test all 942 configurations would take an unreasonable about of time, therefore, the
project was broken into three phases. Phase one was be to do a quick test of each configuration to acquire
a rough idea of how the flow field will behave.
This was done with flow visualization.
Flow
visualization is a process where smoke is put into the flow field around the wing and tip assemble. A
laser was then be used to illuminate a single plain in the wake of the wing. Data was collected visually as
to the characteristics of the flow field. The data collected from the flow visualization tests will be used to
narrow down the number of configurations to be tested in phase two. Particular interests will be given to
cases where the tip vortex appears to be that of a delta wing, and where two distinct tip vortices are
visible.
Phase two will be to use a 7-hole pressure probe to take actual physical data of the flow field.
The 7-hole pressure probe can acquire not only total pressure data in the flow field, but also the velocity
and direction of the flow field. This data can be used to generate plots to illustrate the effect that the delta
wing tip has on the flow field. The final phase of this project will be to select the most promising cases
from phase two and with a stereo particle image velocimetry system, collect more accurate data on the
pressure velocity and direction of the flow field. Stereo particle image velocimetry is more accurate then
the 7-hole pressure probe because it is non intrusive, relying only on lasers instead of a physical probe in
the flow field.
As of the end of this summer, the first half of phase one will be complete. Flow visualization has
been completed for all 942 configurations and the necessary data collected. Currently the data that was
collected from the flow visualization is being compiled and the cases for phases two and three are being
chosen. Preliminary results are showing several trends in the data that will need to be looked at more
carefully in phases two and three.
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