lab 4 -baru.docx

INTRODUCTION

The effect of hydrostatic pressure is of major significance in many areas of engineering, such as shipbuilding, the construction of dykes, weirs and locks, and in sanitary and building services engineering.

With the HM 150.05 Hydrostatic Pressure Apparatus the following key topics can be investigated by experimentation: Pressure distribution in a liquid taking into account gravity. "Lateral force" of the hydrostatic pressure Centre of pressure of the lateral force.

The appendix to this Test Instruction contains .prepared worksheets which facilitate methodical evaluation of the results of the experiments. The apparatus is designed for use in the fields of education.

Hydrostatic pressure is, the pressure exerted by a fluid at equilibrium due to the force of gravity. A fluid in this condition is known as a hydrostatic fluid. So our Hydrostatic pressure lab was to determine the hydrostatic pressure of water on a flat surface. Adding weight and then filling the tank with water to the point where the apparatus was in equilibrium. so we can calculate the force on the flat surface using the given equations.

The study of pressure forces acting on plane submerged surfaces is a fundamental topic in the subject of hydrostatic involving assessment of the value of the net thrust and the concept of center of pressure, which are so important in the design of innumerable items of hydraulic equipment and civil engineering projects.

OBJECTIVES To determine experimentally the resultant hydrostatic force (total force) applied on a submerged surface. To determine the experimental and the theoretical center of pressure.

PURPOSE To investigate the pressure acting on a submerged surface and to determine the position of the center of pressure

THEORY

The hydrostatic pressure of liquids is the "gravitational pressure" phyd. It rises due to the intrinsic weight as the depth t increases, and is calculatedfrom: phyd = rgt.

r - Density of waterg - Acceleration due to gravity (g=9,81 m/s2)t - Distance from liquid surface

To calculate forces acting on masonry dams or ships hulls, for example, from the hydrostatic pressure, two steps are required:

Reduce the pressure load on an active surface down to a resultant force Fp, which is applied at a point of application of force, the "centre of pressure", vertical to the active surface. Determine the position of this centre of pressure by determining a planar centre of force on the active surface. It is first demonstrated how the centre of pressure can be determined. The resultant force Fp is then calculated.

TOTAL PRESSUREFor a static fluid, the shear stress is zero and the only stress is true normal stress. Pressure which when in contact with solid surface exerts a normal force towards the surface. It is also call hydrostatic force. F=ghAWhere;F=total pressure (hydrostatic force)P=mass density of the liquidg=gravitation accelerationA=submerge area of the plane surfaceH=vertical distance from the liquid surface to the centroid of the submerge plane surfaceCENTRE OF PRESSURECentre of pressure is general below centroid since pressure increases with depth. Centre of pressure is determine by equating the moments of the result and distributed force about any arbitrary axis. The application point of the total pressure (hydrostatic force) on the surface. h=Ia sinO+ hhAWhere;h=vertical distance from the liquid surface to the centre of pressureIg=moment of inertial of the plane surface about its centroid G

APPARATUS

The equipment required for the testing of this lab is: The F1-12 Hydrostatic Pressure Apparatus F1-10 Hydraulics Bench (water source) Graduated Cylinder. Center of pressure apparatus (Figure 1).

Figure 1: Center of pressure apparatus.

PROCEDUR

1. Place the empty tank on the Bench and position the balance arm on the pivot.2. Place the balance pan in the groove at the end of the balance arm.3. Level the tank.4. Position the counterbalance weight until the balance arm is horizontal.5. Add a known amount of weight to the balance pan. Pour water into the tank until the balance arm is horizontal again. (Note: it may be easier to overfill then use the drain to level it.) When the arm is level, this means that the force on the vertical face of the quadrant balances out the force due to the added weight.6. Read the depth of immersion from the scale on the face of the quadrant.7. Repeat the experiment by adding more weights until you have at least two measurements in which the vertical face is completely submerged.8. Calculate the magnitudes and locations of the forces for each weight combination.9. Compare these locations with the theoretical positions.

RESULT

ANGLE ( )

LOWEST WATER LEVEL St(mmWC)HIGHEST WATER LEVEL Sh(mmWC)

0--

Level armL (mm)

Appended weight F (N)

Water level reading s (mm)

Calculated level arm I (mm)

Resultant forceF (N)

1501.0481840.848

1501.5591801.30

1502.0681771.70

1502.5771742.18

1503.0841722.60

1503.5921693.11

1504.0981673.53

ANGLE ( )


102116

Level armL (mm)





1501.052183.080.938

1501.562179.691.346

1502.071.8176.371.828

1502.576174.952.042

1503.090170.212.881

1504.0103165.853.679

1504.5116162.674.635

ANGLE ( )


102116

Level armL (mm)





1501.0

1501.5

1502.0

1502.5

1503.0

1504.0

1504.5

ANGLE ( )


30

Level armL (mm)





1501.0701771.471 x 10

1501.5811732.281 x 10

1502.0901702.943 x 10

1502.5981673.532 x 10

1503.01061654.120 x 10

1503.51121634.562 x 10

1504.01201605.150 x 10

ANGLE ( )


40--

Level armL (mm)





1501.0841722.502 x 10

1501.5981673.532 x 10

1502.01061654.120 x 10

1502.51141624.708 x 10

1503.01201605.150 x 10

1503.51281575.738 x 10

1504.01361556.327 x 10

DISCUSSION From the experiment that were done; The data is applied to the formula from theoretical value From the data, it has a different between vertical plane surface and inclined plane surface.

The force applied in the system vertical face of buoyant material counter acts the mass added to the hanging arm. so we know that if we move away from the sea level, the pressure will change either with air or water. So in our experiment also change in pressure because of the weight of the water above and buoyant forces clearly show the properties of water. The water pressure was so high that we add the mass 50 g to 450g even still quadrant was able to support it in static equilibrium. So the idea let us to believe that the curved area allows for a larger surface with which the water can act upon for less change in depth. This would explain such a large jump in force applied after breaking the upper plane of the vertical face.

1. How to determine the center of pressure ?To determine the pressure ,add up all contributions to the force over each small piece of the area, but multiplied by y. The of pressure is essentially a weighted average.

2. How the mean x-position of the force can be determined?The mean x-position of the force can be determined by similar technique. The is just the product of the intertia for coordinate system.

CONCLUSION

From the experiment that have being done, we can conclude that the experiment was successfully carried out even though there is difference in the theoretical value and experimental value. There is no relative motion between the fluid particles. The only stress will be normal stress which equal to the pressure.There are some errors that take place during conducting this experiment which may give effect to the result obtained. First, there is parallax error.

This error may occur during taking the reading of the water level. To overcome this error, the observers eye must be 90o perpendicular to the water level in order to get the accurate measurement. Next, error may take place during pouring the water. This happen when the water poured over the limit that should be poured. Thus, to overcome this error, the water poured during the experiment must be ensured that perfectly reach the limit. Other than that, there is maybe an error due to the instrument and also surrounding. Hence, to get an accurate result, the experiment must being done in ideal condition.

There was an error when doing this experiment. The error is when the reading is taken, parallax error has occurred at the left and right water level .When pouring the water it may be over the limit that we want.So, we recommended that to Change to the new equipment and apparatus and built the platform when taking the parallax error.

REFERENCES

1. http://atapaje.blogspot.com/2008/02/hydrostatic-force-on-plane-surface.html2. http://www.emet.ou.edu/cbin/eBook.cgi?doc=&topic=fl&chap_sec=02.3&page=theory3. http://web.cecs.pdx.edu/~gerry/class/EAS361/lab/pdf/lab3_hydrostatics.pdf

2

lab 4 -baru.docx

Documents

Transcript of lab 4 -baru.docx