BOUNDARY LAYER AND ROUGHNESS CHARACTERISTICS OF HULL COATINGS

Transcription

1 BOUNDARY LAYER AND ROUGHNESS CHARACTERISTICS OF HULL COATINGS Carbon Dioxide Transport Infrastructure for the BY UK Irma Yeginbayeva, George Politis, Mehmet Atlar, School of Marine Science and Technology, Newcastle University, UK Research Activities Maxim Candries, at the Marc Vantorre Maritime Technology Division, Ghent University, Belgium Newcastle University 17 th ICMCF, Singapore, 6-10 July 2014

2 Preview 1. Objectives 2. Experimental set-up 3. Tested coatings 4. Results 5. Conclusions 6. Further work Fluid Structure Interaction 2

3 1. Objectives o A new experimental set-up has been developed for the Emerson Cavitation Tunnel whereby coated surfaces can be tested efficiently; o Roughness and boundary layer characteristics of commerical coatings are to be investigated: A. Three commercial coatings to mimic clean newly applied coating conditions on request of Dredging International (DEME Group, Belgium) o Roughness and boundary layer characteristics of coatings are to be compared. Fluid Structure Interaction 3

4 2. Experimental set-up o Boundary layer characteristics are measured using 2D LDV system in the Emerson Cavitation Tunnel; o Maximum speed in the measuring section is 8 m/s; o Large observation windows on the side walls and floor; Measuring section of Emerson cavitation tunnel Fluid Structure Interaction 4

5 2. Experimental set-up o High speed insert is the new feature of the tunnel; o Test specimens have a 218 by 598 mm² coated area; o Preferably on acrylic substrate; Fluid Structure Interaction 5

6 2. Experimental set-up o Test speciments can be replaced rapidly (in 1-2 hours); o 5-6 boundary layer profiles 1 coated surface can be tested per day; Testing plate Fluid Structure Interaction 6

7 2. Experimental set-up o Roughness characteristics of same test specimens are measured with optical laser profilometer (Uniscan OSP100), stylus instrument (Surtronic 25); Fluid Structure Interaction 7

8 3. Tested coatings o 3 commercially available coatings to mimic as newly applied condition ; o Commissioned by Dredging International (DEME); o These vessels are a lot of the time operational at low speeds (dredging mode), often in tropical waters; Fluid Structure Interaction 8

9 3. Tested coatings o After drydock observations, alternatives, preferrably without biocides, are sought to replace standard tin-free SPC (Coat-1) o Two candidates, new on the market, which both claim significant drag benefits: Coat-2: A new generation Foul Release system with added biocides for extra fouling defence, suitable for vessels with long idle periods, which in this case are better called very active periods Coat-3: A novel biocide-free nanostructured coating that would be combined with an active ultrasound antifouling device Fluid Structure Interaction 9

10 3. Tested coatings o Full coating schemes applied on steel test specimens at shipyard, then transported to Newcastle. a. Coat-1 before the hydrodynamic testing b. Coat-1 after the hydrodynamic testing c. Coat-2 before the hydrodynamic testing d. Coat-2 after the hydrodynamic testing e. Coat-3 before the hydrodynamic testing f. Coat-3 after the hydrodynamic testing Fluid Structure Interaction 10

11 Rt (microns) 4. Results Roughness data analysis Boxplot of Coat-1, Coat-2, Coat-3 (5mm cut off) Coat-1 Coat-2 Coat-3 Fluid Structure Interaction 11

12 4. Results BL velocity profile data o At least three boundary layer profiles of each surface were measured Fluid Structure Interaction 12

13 4. Results Roughness: All three coatings are very smooth but Coat-3 exhibits higher Rt; Coat-1 and Coat-2 not significantly different for amplitudes but Coat-2 has a more open texture. Boundary layer: Coat-2 is hydraulically smooth (i.e. DU + = 0 over the tested range of viscous lengths); Followed by Coat-1 and Coat-3 (both still have low DU + ); Fluid Structure Interaction 13

14 5. Conclusions o Tested coatings: The differences in boundary layer and roughness characteristics are smaller than e.g. 10 years ago Foul Release still performs best (DU + = 0!) Fluid Structure Interaction 14

15 6. Further work In-situ evaluation of antifouling performance over summer period in Persian Gulf Fluid Structure Interaction 15

16 6. Further work o Further work on correlation coating roughness drag; o What is the (unfouled) in-service condition? o In-service conditions hulls often covered with biofilms hence: A new set-up has been developed at Newcastle University to grow biofilms on test specimens and then test the boundary layer and roughness characteristics Further exploration of the impact of dynamic changes experienced by coatings in-service will continue-as being explored in Newcastle University s dynamic slime farm and in-service testing on UNEW s reseach vessel; Fluid Structure Interaction 16

17 Dynamic Slime Farm Fluid Structure Interaction 17

18 Dynamic Slime Farm Fluid Structure Interaction 18

19 UNEW s research vessel Biofilm growing in dynamic condition using UNEW s research vessel: - 18m catamaran research vessel with a 15knots cruise speed - Installation of test plates on a strut suspended from the moon-pool of the vessel Vessel with moon-pool shown on deck Moon-pool shown from below Fluid Structure Interaction 19

20 Moon Plug Design o Final design of the moon-pool consists of three fins carrying 4 plates each (12 panels in total); o Discussion is ongoing with a local shipyard to build this strut; Main dimensions of moon plug Fluid Structure Interaction 20

21 Acknowledgements: Mr. Jorne Beyen of Dredging International Thank you for Listening Any Questions & Comments?