Any structure placed into water is subject to marine growth as shown in the diagram below:
Schematic of critical biofouling stages [L.D. Chambers et al, 2006]
After placing any structure in the water its surface immediately starts accumulating simple organisms creating biofilm, which, in turn provides the food and habitat for more advanced organisms.
Effects of marine growth on loading [Iberahin Jusoh et al, 1996]:
Factors affecting marine growth:
Mussels (hard growth) - likely to appear in the water range 0-40 m, thickness up to 35 mm. Successful colonizer due to its ability to settle out in high currents (5 knots)
Seaweedsappear in 0 - 25 m depth
Anemones, Soft Corals appear in water depth 14 - 100 m, thickness up to 30 mm
Barnacles - occur in shallow and deep water, can grow up to 80 mm, hard to remove because of the tensile strength in excess of 50,000 p.s.i
Tubeworms - appear at 35 - 100 m,
Hydroids 50 -300 mm, appear in shallow and deep water depending on the type of hydroid,
Tunicates - from the intertidal zone to deep waters
For this project the following assumptions were made:
The sensitivity analysis was carried out with regards to marine growth establishment on the surface of hydrofoil and it was decided to rerun the simulation assuming 10 mm of marine growth. Results are represented in the table below.
Surprisingly, the results didn't have much difference between each other, the drag was increased by 3 times and lift decreased by 2 times. Based on previous results, the mooring angle from seabed will be decreased by approximately 15 degrees which increases a footprint of the system
The outcome of the simulation means two things: 1)the marine growth has a significant effect on the performance of the hydrofoil 2) there are great uncertainties about the program simulation such as