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DEPARTMENT OFAERONAUTICS &

ASTRONAUTICS
SUBJECT : Aerodynamics Lab
SUBJECT CODE : 205202
LAB NO : 11
TITLE : CALCULATION OF CP DISTRIBUTION ON
AN AIRFOIL AT UPPER AND LOWER SURFACE
SUBMITTED TO : Sir Muhammad Usama Saeed
SEMESTER : 3rd
SECTION :A

Marks Obtained
Group Group Group Member
Member 1 Member 2 3
NAME Meer Khan Ahmed Bilal Kanwar.M Hamza
REGISTRATION # 230101031 230101015 230101091
LAB REPORT
PERFORMANCE
TOTAL MARKS

DEADLINE: 15 January 2025

DATE OF SUBMISSION: 15 January 2025

Aerodynamic LAB Page 1 Experiment #11

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Table of Content:

GENERAL SAFETY PROCEDURES:..............................................................................................3

Introduction: .......................................................................................................................................4
Setup Used: .........................................................................................................................................4
Objective: ...........................................................................................................................................4
Theory: ...............................................................................................................................................5
•Static Pressure:.............................................................................................................................5
•Dynamic Pressure: .......................................................................................................................5
•Pressure Coefficient: ....................................................................................................................5
Appratus: ............................................................................................................................................5
Procedure: ...........................................................................................................................................6
Calculations: .......................................................................................................................................7
GRAPH: .............................................................................................................................................8
Observations: ......................................................................................................................................8
Conclusion: .........................................................................................................................................9

Aerodynamic LAB Page 2 Experiment #11

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GENERAL SAFETY PROCEDURES:

• Know the location of emergency medic box, fire extinguisher, eye wash and safety shower
and know how to use them.
• Keep away from the inlet and outlet of the Wind Tunnels while operation.
• When using the smoke generator divert the outlet of the wind tunnel in the safe manner
away from the teaching area.
• The air pressure at the outlet of the wind tunnel is high enough to blow off small
structures and well certainly disturb dust and debris and scatter paper and documents if
they are left nearby.
• Never eat, drink, or smoke while working in the laboratory.
• Read labels carefully.
• Do not use any equipment unless you are trained and approved as a user by your
supervisor. If you have long hair or loose clothes, make sure it is tied back or confined.
• Keep the work area clear of all materials except those needed for your work. Extra books,
purses etc. should be kept away from equipment.
• If a piece of equipment fails while being used, report it immediately to your Lab
instructor.
• If you are leaving a lab, turn off all the Electric switches / water inlet valves, ignition
sources and lock the doors.
• Never do unauthorized experiments.
• Know the lab and building evacuation procedure in case of any emergency.
• in case of any injury notify your instructor immediately.
• "It is always better to ask questions then to risk harm yourself a damage the equipment"

Aerodynamic LAB Page 3 Experiment #11

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Introduction:
This lab is focuses to explore the fundamental principles of aerodynamics by studying the pressure
distribution and airflow behavior around an airfoil. Using a wind tunnel and pressure measurement
apparatus, the experiment provides hands-on experience in measuring static and dynamic pressures,
calculating free-stream velocity, and determining the center of pressure. By analyzing the relationship
between pressure distribution and aerodynamic performance, the lab aims to enhance understanding of
how airfoils generate lift and respond to varying flow conditions, bridging theoretical knowledge with
practical application.

Setup Used:
The Flotek setup is a wind tunnel apparatus used to study fluid dynamics and aerodynamics. It features
a test section for models like airfoils and a pressure measurement system to record pressure
distribution. By analyzing water column heights or sensor data, it enables calculations of velocity,
static pressure, and other aerodynamic properties, making it ideal for research and education.

Objective:
Here are the general objectives of this lab:
• To understand the basic principles of aerodynamics, including pressure distribution and airflow
behavior around an airfoil.
• To measure static and dynamic pressures using a wind tunnel setup and analyze their variations
as angle of attach vary along the airfoil surface for next objective.
• To calculate the free-stream velocity and other aerodynamic parameters from experimental
data.
• To determine the center of pressure and its dependence on the airfoil's geometry and angle of
attack.
• To develop skills in data analysis and graphing, linking experimental results to aerodynamic
theory.

Aerodynamic LAB Page 4 Experiment #11

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Theory:
•Static Pressure:
Static Pressure is the pressure exerted by a fluid at rest or parallel to a surface, representing its
potential energy. It is measured perpendicularly to the flow to avoid velocity effects. In a wind
tunnel, it decreases with increasing velocity, reflecting energy changes.

•Dynamic Pressure:
Dynamic Pressure is the pressure due to fluid motion and is defined as the kinetic energy
per unit volume of a fluid, particularly in a moving flow of gas. It is a significant term in
fluid dynamics and appears in Bernoulli's equation. Mathematically, it can be expressed as,
where ρ is the fluid density and v is the flow velocity.

1
𝑃= 𝑝𝑉 2
2
Where,
𝑃 = 𝐷𝑦𝑛𝑎𝑚𝑖𝑐 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒
𝑝 = 𝐹𝑙𝑢𝑖𝑑 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
V = 𝐹l𝑜𝑤 𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦

• Center of pressure CP :
In aerodynamics, Cp refers to the Coefficient of Pressure, a dimensionless quantity that
describes the pressure distribution over the surface of a body in a fluid flow. The variance of
describes the statistical distribution or fluctuation of pressure coefficients over a surface. It is
used to analyze unsteady or turbulent flows.

Appratus:

Aerodynamic LAB Page 5 Experiment #11

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Procedure:
• Position the airfoil at 4° angle of attack in the test section of the wind tunnel.
• Ensure that all tubes connected to the system are properly set up, with one tube measuring
static pressure and others connected to the water columns.
• Turn on the machine to initiate airflow in the test section.
• Initial height of the tubes is 12.7 The airflow will cause the water levels in the connected tubes
to change according to the pressures at different points along the airfoil surface.
• After getting final height h’ find the difference which is caused by fluid.
• Use the formula (where is pressure, is the density of water, is gravitational acceleration, and
is the height difference) to calculate the pressure at each measurement point.
• Firstly same do step to calculate the static pressure from corresponding tube and use it to
calculate free stream velocity whose pressure tube is 10th specified.
• Calculate the static pressure at each location on the airfoil using the formula , with being the
height difference between the water columns which is 𝑃= 𝜌𝑔ℎ

2∗𝑃
• After that calculate the velocity using formula V =√ 𝑝
𝑉
• Use the formula 𝐶𝑝 = 1 − 𝑉∞ to calculate the center of pressure for the airfoil at different
locations.
• Plot the center of pressure on the y-axis against the location of the measurement points on the
x-axis, where is the location of the measurement point and is the chord length of the airfoil.
• Where x/c for each pour will be given by instructor.
• Interpret the graphs to understand the aerodynamic behavior of the airfoil, such as how the
center of pressure shifts with changes in location and airfoil characteristics.
• Summarize the findings of the experiment, discussing the pressure distribution and its effect on
the airfoil's aerodynamic performance.

• V
=
2∗𝑃
√ 𝑝

Aerodynamic LAB Page 6 Experiment #11

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Calculations:
Tube No Initial Final Pressure Velocity CP (Center x/c
Coloumn Coloumn difference at port of
Level Level pressure)
H1 (mm) H2 (mm) N/m-2 ms-1
1 12.7 12.7 0 0 0 0.82
2 12.7 12.7 0 0 0 0.68
3 12.7 12.7 0 0 0 0.54
4 12.7 31.75 186.77 0.61 -0.48 0.4
5 12.7 38.1 249.8 0.70 -0.96 0.26
6 12.7 25.4 124.13 0.5 0 o.16
7 12.7 25.4 124.13 0.5 0 0.06
8 12.7 25.4 124.13 0.5 0 0.01
9 12.7 50.8 373.70 0.86 -1.95
10 12.7 25.4 124.13 0.5 0 0.05
11 12.7 44.45 311.7 0.78 -1.43 0.126
12 12.7 38.1 249.88 0.70 -0.96 0.2
13 12.7 31.75 186.77 0.61 -0.48 0.34
14 12.7 12.7 0 0 0 0.48
15 12.7 12.7 0 0 0 0.63
16 12.7 27.4 144.81 0.54 -0.16 0.8

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GRAPH:
CENTER OF PRESSURE VS X/C

Observations:
• The relationship between the height difference in the tubes and pressure was observed and
verified using the equation.
𝑃= 𝜌𝑔ℎ
• Using Bernoulli's principle, the pressure difference was used to calculate velocity () through
the formula.
2∗𝑃
V =√ 𝑝

• The center of pressure was calculated for each tube using the equation:

Aerodynamic LAB Page 8 Experiment #11

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𝑉
𝐶𝑝 = 1 −
𝑉∞
• The free-stream velocity was consistent across multiple measurements, validating the stability
of the airflow in the test section. However, anomalies in pressure and velocity for certain tubes
highlighted possible flow disturbances.
• By plotting (location along the chord) against , the aerodynamic behavior of the airfoil was
studied. The trends indicated regions of higher and lower pressure, which correspond to lift
generation and flow separation zones

Conclusion:
This lab provided an in-depth understanding of fluid mechanics principles, particularly focusing on
the relationship between pressure, velocity, and aerodynamic behavior. Using the Flotek setup, we
observed how height differences in manometer tubes correlate with pressure changes, validating
hydrostatic principles through. Bernoulli's equation was applied to calculate velocity, demonstrating
the inverse relationship between pressure and velocity in a moving fluid.

The calculation and analysis of the center of pressure Cp offered valuable insights into the
aerodynamic characteristics of the airfoil. The relationship between (chordwise position) and reveal a
trend where is more negative near the leading edge (indicating high suction or low pressure),
gradually increases along the chord (indicating pressure recovery), and approaches zero near the
trailing edge. This behavior reflects the pressure distribution critical for lift generation and
aerodynamic stability.

Aerodynamic LAB Page 9 Experiment #11