SUPERSONIC BOUNDARY LAYER INVESTIGATION
Aero Engineering Laboratory
AOE 4154
Lab Instructor:
Dr. Roger Simpson
Lab TA:
Scott Burger
Lab Section:
Friday 3:55 – 5:20
Date Performed:
December 4, 2009
Student Name:
Craig Sossi
Student Number:
904512344
Honor Pledge:
By submitting this document I pledge that I have neither given nor received unauthorized aid.
Craig Sossi
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The purpose of this experiment is to investigate the three
regions of the boundary layer formed on the wall of the
Virginia Tech Supersonic Wind Tunnel.
The regions include
the Outer Supersonic Region, the Inner Supersonic Region and
the Subsonic Flow Region.
A probe was traversed at different
distances from the wall, and data was recorded.
This data was
reduced revealing that the probe never reached the Inner
Supersonic Region of the boundary layer.
While this did not
occur, the plots verify flow conditions predicted by theory as
the flow approaches a wall.
INTRODUCTION
Supersonic wind tunnels have been used to study the flow around many objects (often
wedges or cones) to determine shock waves and flow patterns.
The results of testing have helped
engineers design aircraft that can fly efficiently at supersonic speeds.
Supersonic tunnels use
basic flow theory to create flow speeds of between Mach 1 and Mach 5.
The tunnel uses the idea
that subsonic flow velocity increases as volume decreases and supersonic flow velocity increases
as volume increases.
The tunnels store air at high pressure which is then released into the tunnel
chamber.
As the air reaches the tunnel throat, it is compressed until the flow reaches Mach 1.
At
this point the flow is then expanded to the desired Mach number, then proceeds through the test
section and out into the atmosphere through diffusers or mufflers.
These tunnels can also be
used to analyze boundary layers at supersonic speeds, either around objects or on the tunnel
walls themselves.
This experiment will focus on the boundary layer investigation through the use of a small
probe.
The probe is mounted to a traverse system and will be utilized to measure various flow
properties at different locations relative to the tunnel wall.
Some flow properties that will be
studied include Mach number, density and velocity.
There are three different zones that compose the boundary layer and each must be
analyzed using different methods.
The three zones include: the Outer Supersonic Region, the
Inner Supersonic Region and the Subsonic Flow Region.
[1]
The Outer Supersonic Region refers to the region of the flow where the Mach number is
supersonic, the shock is attached and the TalyorMaccoll equation is valid.
[1]
To calculate the
local Mach number in this region, equation 1 is used.
(1)
where P
c
is the conestatic pressure and P
t,2
is the Pitot pressure.
Once this is obtained, the local
velocity can be computed using equation 2 where U is the local mean velocity, M is the Mach
number from equation 1, γ is the specific heat ratio, R is the universal gas constant and T
t
is the
total temperature.
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 Fall '08
 Simpson,R
 Aerodynamics, Mach number, local Mach number, Scott Burger, Supersonic Region

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