Siphoning, the process of using a tube to carry a liquid over a barrier and to a lower location, can be described well by the mechanical energy equation. In this assignment you will analyse siphoning behaviour theoretically, and then will carry out an experiment using a plastic bottle and length of tubing provided to you.
The plastic bottle has a nominal volume of one litre. However, two marks have been placed on the side of the bottle such that the corresponding volume between the two marks is approximately ∆V = 650 cm3. The plastic tubing given to you has an inside diameter of D = 2 mm and a length of L = 100 cm. In the picture to the right, ∆z is the variable distance between the liquid level in the bottle and the tube outlet level.
The diameter of the tube is small enough that the flow inside will be laminar, an orderly state of flow in which α = 2 in the mechanical energy equation. Furthermore, the friction (wf) term can be expressed as wf = kf Luavg
where kf = 9.5 s−1 is a friction constant for room-temperature laminar flow of water in this particular tubing. L is end-to-end length of tube and uavg is the average velocity in the tube. You may take the water density to be 999 kg/m3.
Pre-experiment
Before beginning the experiment, make sure the following items are available to you:
The plastic bottle and tubing (provided)
A stopwatch
Some sticky tape for attaching the tube to the side of the bottle (provided)
A large dish for collecting water
Clean drinkable water
A ruler or measuring tape
A pair of scissors (optional )
A pipette dropper (provided)
Analysis
For this experiment the analysis will be performed first.
Calculate the volumetric flow rate of the siphon (cm3/s), assuming that L = 100 cm,
∆z = 80 cm, and that there is no friction in the tube (wf = 0). In order to get the volumetric flow rate, you must first calculate uavg. 15 Marks
Predict the volumetric flow rate of the siphon (cm3/s), assuming that L = 100 cm,
∆z = 80 cm, and that there is friction in the tube (wf given by equation above).
15 Marks
Repeat the flow rate calculation from number 2 with the following change: assume a half-length of tubing is used, with L = 50 cm and ∆z = 33 cm. 10 Marks
Discuss the applications and limitation of a siphon (include images and references), 1000 words max. Graphs/Images/Tables and references are not included in the words count.
