UNIVERSITI TEKNOLOGI MARAKAMPUS SAMARAHAN 2FACULTY OF CIVIL ENGINEERINGDIPLOMA IN CIVIL ENGINEERING (EC110)BASIC HYDRAULICS (ECW 321)EC1104DNAMEMETRIC NO.

NUR AMYRA HIDAYAH BINTI AMIRUL20132233456

ZUBIR BIN SHIBLI2013651848

MOHAMMAD SYAFIQ AKMAL BIN ABDULLAH2013431936

NORHAZERAH BINTI YUSSOP2013251252

NUR HAFIZAN BINTI ASMAIL2013617608

AMIRUL SIRAJ MUNIR BIN JAMALARIFFIN @ ZAINAL 2013624964

LECTURERS NAME: MDM MAUREEN NEGINGDATE OF SUBMISSION: 00 JANUARY 2015

TITTLE Experiment on centre of pressureOBJECTIVETo determine the hydrostatic thrust acting on a plane surface immersed in water and the position of centre of pressure.THEORETICAL BACKGROUNDThe effect of hydrostatic pressure is major significant in many area of engineering, such as shipbuilding, the construction of dykes,weirs and locks, and in sanitary and building services engineering.With the Hydrostatic Pressure Apparatus the following key topic can be investigated in experiment: Pressure distribution in a liquid taking into account gravity Lateral force of the hydrostatic pressure Centre of pressure of the lateral force

The hydrostatic pressure of liquid is the gravitational pressure It rises due to the intrinsic weight as the depth t increase, and is calculated from:

= (6.1) Density of water Acceleration due to gravity (g= 9.81 m/Distance from liquid surfaceTo calculate force acting on masonry dam or ships hulls, for example, hydrostatic pressure, two step are required: Reduce the pressure load on an active surface down to a resultant force , which is applied at appoint of application of force, the centre of pressure , vertical to the active surface. Determine the position of this centre of pressure by determine a planar centre of force on the active surface.It is demonstrated how the centre of pressure can be determined. The resultant force is then calculate.

Determine the Centre of PressureA linear pressure profile is acting on acting on the active surface shown, becauseThe hydrostatic pressure rises proportional to the depth t.The resultant force is therefore not applied at the centre of force C of active surface, but always slightly below it, at the so-called centre of pressure D. To determine the distance e of pressure from the planar centre of force, the following model demonstration is used:

Imagine an area A in front of the active surface, formed by the height h and the pressure profile of the hydrostatic pressure. This area is in the form of a trapezium.The centre of pressure D lies on the extension of the planar centre of force of this area A. A can be broken down into partial areas and. The respective planar centres of force are identified by black dots.

A balance of moment between the areas is then established around the point in order to find common planar centre of force (dynamic effect in direction):

= 0:A. ( = (6.2)Where (6.3) (6.4)A = (6.5)The result is:e = (6.6)With the hydrostatic pressure (6.7) (6.8)The result is: (6.9)e is the distance of the centre of pressure from the force of the active surface which we are looking for.

Determining the Resultant ForceThe hydrostatic pressure acting on the active surface can be represented as resultant force of which the line of application leads through the centre of pressure D. The size of this resultant force correspond to the hydrostatic pressure at the planar centre of force C of the active surface:

(6.10) Hydrostatic pressure at the planar centre of force of the active Surface Vertical distance of the planar centre of force from the surface of the liquid In visual terms, the pressure at the planar centre of force corresponds to precisely the mean value between the highest and lowest pressure, because the linear pressure distribution. If the wall titled by an angle : (6.11)The resultant force can now be calculated: (6.12)

CENTRE OF PRESSURE WITH VERTICAL POSITIONING OF THE WATER VESSEL3.1 Apparatusi. Hydraulic Benchii. The Hydrostatic Pressure Apparatusiii. A set of weights3.2 PROCEDURE3.2.1 Counterbalancing the Water Vessel1. The water vessel was set to an angle of x=0O using the detent.2. The rider was mounted, the lever arm on the scale was set at any position.3. The unit was counterbalanced with the rotation slider. The stop pin was ensure to be precisely in the middle of the hole.

3.2.2. Performing the Measurement 1. The water is top up until the unit was balanced. 2. The water level, s was read off and record it in the prepared worksheet. 3. The appended weights was increased in increments of 0.5-1N and repeat the measurement.

3.2.3 Evaluating the experiment Measured value:S-water level readingI-Lever arm of the force due to weightFG-Force due to weight of the appended weight

3.2.3 Determine the centre of pressureAt a water level s, below the 100 mm mark, the height of the active surface changes with the water level.The height of the active surface is always 100 mm if the water level is above that mark.Meaning:s - Water levele - Distance of centre of pressure D from planar centre of force C of the active surfacelD - Distance to centre of motion of the unit:For a water level s < 100 mm:(Pressure has a triangular profile)

e = s(6.13)ID = 200mm - . S(6.14)For a water level s > 100 mm:(Pressure has a trapezoidal profile)

e = . (6.15)ID = 150mm + e

3.2.4 Determining the Resultant ForceThe resultant force corresponds to the hydrostatic pressure at the planar centre of force C of the active surface. Thus, the height of water level, s must again be differentiated:Meaning:Aac t - Superficial content of active surfaceb (width of liquid vessel) = 75mmPc - Hydrostatic pressure at planar centre of forceFp- Resultant force for hydrostatic pressure on active surface

For s < 100mm:(Triangular profile)Pc = . g. and Aact = s. b(6.17)For s > 100mm:(Trapezoidal profile)Pc = . g(s-50mm) and Aact=100mm. b(6.18)The resultant force is produced asFP = Pc . Aact(6.19)

3.2.5 Balance of Moment

Calculated variables:FG - appended weight I - Lever arm of appended weight referred to centre of motion O.To check the theory, a balance of moments around the centre of motion O can be established and checked:

M (O) =0: FGI= FPID

CENTRE OF PRESSURE WITH WATER VESSEL TILTED3.1 APPARATUSi. Hydraulic Benchii. The Hydrostatic Pressure Apparatusiii. A set of weights3.2 PROCEDURE3.2.1 Counterbalancing the Water Vessel1. an angle and counterbalancing the unit with a rotating slider, the top pin must be precisely in the middle of the hole for this is set.2. The characteristic values in the prepared worksheet of the lowest water s1 and highest water level s1 of the active surface is recorded.

1.2.1 Performing the Measurement 3. Top up with water until the unit is balanced (stop pin at centre of hole) 4. The water level is read off and entered it in the prepared worksheet. 5. The appended weights is increased in increments 0.5N-1.0N and the measurement is repeated.

1.2.2 Evaluating the experimentThe different between evaluation of the tilted vessel and that of the vertical vessel lied in the translation of the water levels onto the tilled active surface. A factor cos must be taken into account here.

3.2.3 Determine the centre of procedureWhen the water vessel is at a tilt, too, a triangular pressure profile is produced when the water level is below s2 above that level a trapezoidal profile is produced.Measured values: S - Water level reading - Tilt angle of vesselMeaning: SL- Water level at lowest point of vessel SH- Water level at active surface at rim e- Position of centre of surface h- Height of active surface ID- Distance between centres of pressure/centre of motion

For a water level s < sh a triangular profile as follows applies:h =e =Ip = 200mm -

For a water level s> sh a trapezoidal profile as follows applies:e = (6.24)Ip = 150mm + e (6.25)

3.2.4 Determining the Resultant Force

Meaning:Aact Superficial content of active surfaceb (width of liquid vessel) = 75mmPc- Hydrostatic pressure at planar centre of force of active surfaceForc s