Pressure Distribution on an Aerofoil: Flow Visualization and Wind Tunnel Testing

FACULTY OF SCIENCE,
ENGINEERING AND COMPUTING
School of Mechanical and Automotive Engineering
BSc (Hons) DEGREE IN
Motorsport Engineering
Sajith Perera: K1418506
Submission Date: 14/03/2017
Pressure distribution on an aerofoil Flow visualisation / Wind Tunnel testing of scale
models.
Moderator: Dr Sing Lo
1

Contents
1 Introduction:.......................................................................................................................................2
1.1 Procedure and Equipment............................................................................................................3
1.2 Theory:........................................................................................................................................5
1.3 Results:........................................................................................................................................6
1.4 Discussion of results:...............................................................................................................10
1.5 Comparison of literature and obtained results:...........................................................................13
2.1 Alternative flow visualisation techniques:.....................................................................................15
2.1.1 Hydrogen Bubble Visualisation:.............................................................................................15
2.1.2 Dye visualisation:...................................................................................................................16
2.1.3 Schlieren photography:...........................................................................................................17
2.1.4 Flow visualization using Smoke:............................................................................................18
2.2 Underbody tunnels:........................................................................................................................19
2.2.1 Tunnel....................................................................................................................................20
2.3 Case study of an open-wheel race car wings design:.....................................................................21
Conclusion:..........................................................................................................................................23
2

1 Introduction:
Aerodynamic forces can be subjected to an object when they travelling in a fluid. The
shape of the object always affects the manner in which these forces act on the objects.
Aerodynamic forces can be detected through a wind tunnel test. This testing is a vital feature
to help test the performance of aerodynamic. By the help of sensors, it is capable to measure
vital information which would assist in the optimization of parts of a body which make it
more effective. Information pressure distribution along the body or aerodynamic forces are
measured to enable identify the characteristics of aerodynamic of any kind of the body.
Moreover, wind tunnel testing can be employed to aid in visualization of the flow along an
object. Flow visualisation is vital since it will permit obtaining which parts of the body deters
the streamlines hence results in the reduction of the performance
1.1 Procedure and Equipment
To finish this analysis, a NACA 653-418 aerofoil is utilized with some pressure
tapings inside where tubes connect these tapings with a multi-tube manometer which shows
the pressure at the diverse positions on the aerofoil (Katz, 2014). The aerofoil is put inside a
low-speed open return wind burrow and the breeze burrow is then turned on, making the air
go around the aerofoil, which shows diverse pressure focuses for each pressure recordings.
The manometer statures are recorded for each pressure tapings (Simon, 2011). The
underlying angle approaches of the aerofoil was - 4° once the manometer statures have
recorded the approach was expanded to 0° and a further arrangement of manometer readings
were taken. This procedure was rehashed for 4°, 8°, 12°, and 16° approaches.
3

Figure 1: Multi-tube manometer (Simon, 2011).
Figure 2: Wind tunnel (Simon, 2011).
4

Figure 3: NACA 653-418 aerofoil with pressure tapings (Simon, 2011).
Figure 4: NACA 653-418 aerofoil pressure taping distances (Katz, 2014).
1.2 Theory:
The difference in pressure is corresponding to the distinction in height of the fluid in
the multi-tube manometer. In this manner, the qualities in table 1 can be changed over to the
coefficients of pressure as appeared in table 2 by the utilization of condition 1. The negative
qualities of table 2 speak to the suction at each pressure recordings (Aird, 2013).
Bernoulli's law expresses that the sum of the dynamic pressure and static pressure must be
constant this is equal to the total pressure, as illustrated by the second equation given below.
5

In an aerofoil, the speed on the upper surface is higher than the speed in the lower surface
(Martinez, 2010). An expansion in airspeed implies that the dynamic pressure is substantial
and in this way the static pressure is little and the other way around. The aerofoil can create
lift because of the way that, the decreased static pressure on the upper surface is greater than
the relatively high pressure under the aerofoil. This pressure contrast between the upper
surface and the lower surface makes a lift.
CP= hi−h∞
h0−h∞ . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Where Cp = Pressure coefficient
P+ 1
2 ρU
2
=Constatnt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
6