This document describes an experiment conducted to determine the center of pressure of a partially or fully submerged rectangular surface. A group of 10 students performed the experiment using an apparatus that measures the forces when water is added or removed. The procedure involves finding the equilibrium point by adjusting a movable weight with the surface at varying angles and water levels. Calculations are shown to relate the center of pressure location to the measured dimensions and forces. Practical applications of center of pressure in aircraft and missile aerodynamics are briefly mentioned.

1. • Course No.: CE-2202 Credit: 1.5
Course Title: Fluid Mechanics Sessional
TOPIC: Centre of Pressure
DHAKA UNIVERSITY OF ENGINEERING AND
TECHNOLOGY, GAZIPUR

2. Presented By: Group: 01
1. Md. Mehedi Hasan - 161065
2. Md. Tayeb Hasan - 161066
3. Md. Momin Ali - 161067
4. Md. Robuil Awal - 161068
5. Md. Mehedi Hasan Shamim - 161069
6. Md. Helal Sarker - 161071
7. Md. Alomgir - 161072
8. Md. Faysal - 161073
9. Md. Morshed - 161074
10. Md. Ekramul - 161075
Department of Civil Engineering,
Dhaka University of Engineering & Technology, Gazipur

3. Presented To:
• Dr. Md. Khasro Mia
• Professor
• Department of Civil Engineering
• Zakir Hossen
• Assistant Professor
• Department of Civil Engineering
• Department of Civil Engineering,
Dhaka University of Engineering & Technology,
Gazipur

4. WELCOME
TO MY PRESENTATION

5. BACKGROUND
The center of pressureis that point where the total
some of pressure field acts one a body, causing a
force to act through that point. The resultant force
and Centre of pressure location produce equivalent
force and moment on the body as the original
pressure field

6. APPARATUS
• 1.Water Tank
• 2.Detent
• 3.Slider
• 4.Stop Pin
• 5.Water Level Scale
• 6.Rider
• 7.Weights
• 8.Handle

7. PROCEDURE
1. The apparatus is placed in a
splash tray and correctly
leveled.
2. The length l and width b of the
rectangular surface, the
distance r from the pivot to the
top of the surface, and the
distance s from the hanger to
the pivot were recorded.
3. The rectangular surface is
positioned with the face
vertical (θ=0) and clamped.

8. • 4. The position of the moveable jockey weight
is adjusted to give equilibrium, i.e. when the
balance pin is removed there is no movement
of the apparatus. The balance pin is replaced

9. • 5. Water is added to the storage chamber. This
created an out-of-balance clockwise moment
in the apparatus. A mass M is added to the
hanger and water is slowly removed from the
chamber via drain hole such that the system is
brought almost to equilibrium, but now
clockwisw moment is marginally greater.
Water is slowlynadded to the storage chamber
by a dropper until equilibrium is attained. At
this condition the drain hole is closed and the
balance pin again removed to cheek
equilibrium.

10. 6. The balance pin is replaced and the values of
y1, y2 and M were recorded.
7. The above procedure is repeated for various
combinations of depth.

11. MAJOR EQUATION
The magnitude of the total hydrostatic force F
will be given by
F = ρgȳA
Where, ρ = Density of fluid
g = Acceleration due to gravity
ȳ = Depth to centroid of immersed
A = Area of immersed surface
This force will act through the centre of pressure
C.P. at a distance (Measured vertically)from
point O

12. Theory shows that
y = ȳ +
Where
ȳ = distance from O to the centroid CG of the
immersed surface.
ICG = 2nd moment of area of the immersed surface
about the horizontal axis through CG
ICG
Ay

13. Experimental determination of yp :
For equilibrium of the experimental apparatus, moments about
the pivot P give
Fy = W.z
= M g. z
Where
y = Distance from
pivot to centre of
pressure
M = Mass added to
hanger Fig : Partially submerged condition

14. z = Distance from pivot to hanger
Therefore
y =
But y = yp + r - y1 [ full submerged ]
y = yp = r + y1 [ partially submerged ]
Therefore
yp = y - (r - y1) [ fully submerged ]
yp = y - (r - y1) [ partially submerged ]
Where
r = Distance from pivot to top of rectangular surface
y1 = Distance from water surface to top of rectangular
surface
In Fig
y2 = Distance from water surface to bottom of rectangular
surface
Mgz
F

15. PRACTICAL APPLICATION
• In engineering field,centre of pressure in most
used topics.In our practical iife we used many
things which make on based of centre of
pressure.Centre of pressure is also used in
Aircraft aerodynamics, Missile aerodynamics
etc.

16. • One very important application is for pitch
stability of an airplane. This is stability in the nose
up, nose down Direction. I use this when
designing paper airplanes.
• We look at the location between tail and nose of
both the center of gravity and the center of
pressure on the wing. The center of gravity is the
point where it appears that gravity is pulling
down on the aircraft.
• The center of pressure is a point along that line
where the lift is pulling up on the airplane.