August 2014 Mission Statement Background
Download 11.38 Mb.
|
- Navigate this page:
- 4.2.2 Change of Flow Rate during a One Hour Period
- 4.2.3 Further Testing
- Plastic Sheet Between Sand and Water Test
- Increasing Amount of Holes for Anchor Leg
- Gripping Force without Vacuum
4.2 Results4.2.1 Change of Grip during a One Hour PeriodThe main experiments carried out were to see how the maximum lifting force required removing the anchor leg changed with time. This was done in 10 minutes steps from 0 to 60 minutes. Every time the anchor leg had been lifted and read one result, it had to re-fluidise the sand to embed itself again before starting another test for a different time period. This was repeated three times seen below as Test 1, Test 2 and Test 3 in Table 2 and Graph 4. Table 2 Results from standard one-hour tests
Graph 4 Results from standard one-hour tests 4.2.2 Change of Flow Rate during a One Hour PeriodFor Test 2 and Test 3, the flow rates were examined. This was done by having 1 litre of water in a bucket, taking the end of the vacuum hose from the water-filled collecting beaker to the bucket without letting air in and measuring the amount of water after 1 minute. From this, suction flow rate in mL/s could be calculated from which the results are displayed in Table 3 and Graph 5. Table 3 Results for flow rate during one hour
Graph 5 Results for suction flow rate during one hour 4.2.3 Further TestingFriction TestFrom the results for the three one-hour tests, it was decided to test the friction of the plastic anchor leg material to find the friction coefficient. It was found by considering all forces on the anchor leg as it is tilted until the sand particles are only just displaced from original location. These are shown in Figure 30. 
Figure 30 Finding friction coefficient Friction coefficient is equal to tan(q), and varied for the anchor leg depending on if the sand was outside or inside of the leg and if the particles were wet or dry. The results are in Table 4, where details of why friction coefficient is tan(q) and calculations for the values are in Appendix J. Table 4 Friction coefficient
It was expected that the friction factor would be higher on the inside of the anchor leg, due to the force from the walls. However, when investigating further, it was noticed by scratching the surface with fingernails that the inside of the anchor leg was a lot smoother. This contributed to the friction factor, resulting in higher value on the outside of the anchor leg. Plastic Sheet Between Sand and Water TestThe flow rates were considered to be varying too much during tests 2 and 3 as well as being too high, so a plastic sheet was fitted on top of the sand before fluidisation to see if this would alter the results. The aim was that the plastic would act similarly to having a thin layer of clay at the top, which is a common situation, especially in fluidisation, since smaller particles are then tempted to travel upwards. A layer of clay is denser and keeps the sand in place, hence why the plastic sheet with a hole in the middle for the anchor leg could bring similar behaviour. This was wished to create a situation where the pressure of the water would spread more to the sides and not be centralised around the anchor leg. In theory, that would reduce the flow of the water and could even cause it to become more constant. The results are seen in Table 5. After one hour, the lifting force was examined, which came to 164 N. Comparing this to the previous lifting forces after one hour, it was roughly between the results of Test 2 and Test 3. Table 5 Change in flow rate during 1 hour for test 4
Increasing Amount of Holes for Anchor LegTwo rows of three holes were added in same pattern to investigate the influence the number of holes have on the sand anchor, especially the suction flow rates. The plastic sheet was used again due to its positive effect. The results are seen in Table 6 and compared with previous values in Graph 6. The average values and independent error bars are shown in Graph 7, where the decreased range of values caused by using the plastic sheet is evident. After one hour, the lifting force was 169 N, a small increase compared to test 4. Table 6 Flow rates for test 5 during one-hour period
Graph 6 Comparison of all volumetric flow rates 
Graph 7 Average flow rates of all tests Gripping Force without VacuumA final experiment, called test 6, was carried out to see what force was needed to pull the anchor leg out when it was not pulling a vacuum. This was done with same settings as test 5, with plastic sheet and added holes, since it was only the natural pull of the anchor leg being tested. It was repeated three times giving the results of 102, 89 and 98 N. This averaged a force of approximately 96 N. Test 6 was completed by pulling a vacuum to force the sand particles towards the leg, then releasing it to see if gripping force was improved. At this point, roughly 146 N was needed to pull it out. Directory: shs shs -> Stonelaw Mathematics Department Green Course Revision Sheets Block E shs -> Core Classes Offered by Department Indicates ncaa clearinghouse Approved Core Class english shs -> Identify the prepositional phrases in the following sentences. Write them on a separate piece of paper shs -> Smart Phone Class Security and Safety shs -> Bordon Luciano shs -> 1 Week before Scheduled Contact shs -> Informative Research Essay Assignment shs -> 10th Daily “Fix It” Sentences shs -> The story of Perseus as told by Diodorus Download 11.38 Mb. Share with your friends:
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||