Marine fouling diversity as occurring in the North Sea on a silicone based coating
Slime fouling Within the CRS ECON- SHIPS work group MARIN and its partners are establishing a ship performance model in which various aspects affecting the economical and environmental impact of a ship are being assessed. One of these aspects is fouling. The objective is to find the relationship between observed slime fouling on the hull and its impact on fuel consumption and consequent impact on exhaust emissions. To obtain a valid rela- tionship it is important to conduct a large amount of tests with various types of slime. Rotating disk experiments are very suitable for these tests because a disk is small enough to grow various types of slime layers under controlled circumstances and it can be rotated fast enough to achieve high Reynolds numbers.
Dedicated test ship Simultaneously, the Service Performance Analysis Joint Industry Project (SPA-JIP) is initiating a research campaign on board a dedicated test ship to look at the overall effect fouling has on fuel consumption. This ship will also be used to determine the effect of fouling on the boundary layer flow at various locations on the hull in different stages of hull fouling. As well as the hull, the propel- ler is also vulnerable. The SPA-JIP is also investigating the effect of cleaning the hull and propeller. Fouling can increase the pro- peller’s roughness, which can decrease its efficiency considerably. Dedicated, full-scale tests in the SPA-JIP showed that the clean-
ing of propellers in a dry dock resulted in an efficiency increase of 13%. If there is only limited time to perform cleaning by divers in the water, it is therefore recommended that the propeller is always cleaned first. Further tests in the SPA-JIP showed that regained performance due to full cleaning could be attributed one-third to cleaning the propellers and two-thirds to hull clean- ing. This is backed-up by literature.
New Joint Industry Project These research projects are examples of applied research, leading to tools that can be applied directly by the industry. In addition, it is also recognised that there is a lack of
Adult barnacles of various age at a raft exposure panel at TNO
knowledge on the mechanisms that play a role in the effect of slime fouling on the boundary layer. Gaining an insight into this problem is deemed crucial if a solution to the fouling problem is to be found. A new Joint Industry Project on Drag Reduction and Coatings will be set up together with TNO and various industrial partners to investigate optimized drag reduction by smooth hull and coating design. Part of this project will be focussed on how microbial slime layers build up and interfere with friction drag on a ship scale, other aspects will be optimised strategies for coating use and application as well as hull maintenance practices.
report 19
Courtesy TNO
Courtesy TNO
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