Bernoilli’s Principle1. AbstractThe objective of this experiment was to investigate the Bernoulli’s law. Calculation on hdynamic, Wmeasured and Wcalculated at each points of the venture tube will be done. The value of Wmeasured will be compared to the value of the Wcalculated. From this experiment, it is proven that when the speed of fluid increases, the pressure of the fluid will decreases.

2. Introduction This experiment is carried out to show the validity of the Bernoulli Equation. Bernoulli’s principle is named after the Dutch-Swiss mathematician Daniel Bernoulli. For mechanics of fluid, Bernoulli’s principle states that for an inviscid flow, an increase in the speed of the fluid will results in a decrease of the pressure. When a fluid is moving horizontally, the highest speed occurs where the pressure is lowest and the lowest speed occurs where the pressure is highest. Bernoulli’s equation for constant head, h is given as:-

3. Experiment Methods and Materials The apparatus used in this experiment are Bernoulli’s principle apparatus, weighing tank, stopwatch and water.

Before the experiment starts, a quick inspection was performed to ensure the unit is in proper operating condition. A hose connection was made and the unit was connected to the nearest power supply. The discharge pipe was then opened. The cap nut of probe compression gland was set such that the slight resistance is felt on moving probe. After that, the inlet and outlet valves were opened. The pump was also switched on and the main cock was slowly opened. The vent valves on water pressure gauge were opened and the outlet cock was carefully closed until pressure gauges are flushed. By simultaneously setting inlet and outlet cock, the water level in pressure gauges was regulated such that neither upper nor lower range limit is overshot or undershot. The pressures at all measurement points were recorded. Then, the overall pressure probe was moved to corresponding measurement level and the overall pressure was noted down. The volumetric flow rate was determined by using stopwatch to establish time required for raising the level in the volumetric tank from 20 to 30 litres. 4. Data AnalysisThe specific results from the experiment allow us to determine the hdynamic, Wmeasured and Wcalculated.

h1 h2 h3 h4 h5 h6

hstat.

(mmWs)250.00 235.00 45.00 162.50 180.00 190.00

htotal

(mmWs)260.00 255.00 252.00 238.00 229.00 218.00

hdyn (m) 0.009997 0.01999 0.2069 0.07647 0.04898 0.02799Wmeas. (m/s) 0.4429 0.6263 2.0149 1.2249 0.9803 0.7411Wcalc. (m/s) 0.5027 0.7290 2.0120 1.0000 0.6670 0.5027

5. DiscussionCalculations are done based on the formulas below:hdynamic = (htotal – hstat.) / gWmeasured = √2.g.hdyn.

Wcalculated = Q / A

From the data collected, we found that the time taken for the water level in the volumetric tank to rise from 20 to 30 litres is 58.75s and the flow rate, Q is 1.702x10-4 m3/s. The relation of 1mmWs = 9.80665Pa is used for the unit conversion.

The validity of the Bernoulli Equation is proven under this experiment. When the pressure head (hstat.) increases, the velocity head (W) will decreases. Hence, the speed of the fluid is inversely proportional to the pressure of the fluid.

The experimental velocity is different from the theoretical velocity due to the friction loss. Some of the force is used to overcome the frictional force and hence result in a slight decrease in the experimental velocity.

6. ConclusionFrom this experiment we found out that fluid flowing under horizontal streamline will follows the Bernoulli’s principle where when the speed of fluid increase, the pressure of the fluid will decrease. The Bernoulli’s principle is applied on the aeroplane’s wings. The shape of the aeroplane’s wings is aerofoil. Due to the streamline shape of the aerofoil, the air flowing past the top surface of an aeroplane’s wing is moving faster than the air flowing past the bottom surface thus a lift is generated. Under this condition, the pressure at the top surface of the wing will be lower than the pressure at the bottom surface of the wing.