© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
DOLPHIN-INSPIRED COMPLIANT COATINGS FOR DRAG REDUCTION OF SHIPS
Dorothea Stübing, Volkmar Stenzel, Claus Schreiner; Fraunhofer IFAM Lars-Uve Schrader; Hamburg Ship Model Basin - HSVA
©SaveJapanDolphins.org
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Hydrodynamic champions in nature
Different strategies to optmize hydrodynamics
Sharks – micro-textured skin Reduction of turbulent skin friction
Penguins – air lubrication Reduction of turbulent skin friction
Dolphins – compliant skin Retention of laminar flow
©WallPaperSite.com
©National Geographic
Source: youtube
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
The biological example and the technical model
Dolphin skin
Model: Flexible membrane as dermis, spring-damper system as blubber
→ Parameters: Spring and damper rates, bending stiffness
reproduced after www.oceanbites.org reproduced after Carpenter & Garrad, J. Fluid Mech. 155, 1985
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
FLIPPER – background of the project
Increase of resistance at
transition from laminar to
turbulent friction
Coefficient of friction vs. Reynolds number for flow over a flat plate
Source: Lecture “Bionik I” Winter 00/01 - Ingo Rechenberg, TU Berlin
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Background of the project
Laminar-turbulent transition along the streamlines
Simplified representation by Hamburgische Schiffbau-Versuchsanstalt GmbH (HSVA)
Delayed transition → significant effect on resistance
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Approach of the project
Shear stress on the hull (vessels without bulbous bow)
Maximum shear stress on the bow → Flexible bow coating
Laminar behavior of the boundary layer → delay of the transition to turbulence
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Approach of the project
Delay of transition point increase of laminar flow reduction of resistance
Mechanistic hypothesis: If damping of the T-S waves enables energy to be removed from the
boundary layer, then the laminar-turbulent transition should be delayed New polymers having extremely good energy dissipation should be ideal for
this purpose
T-S waves
Delay of transition from laminar to turbulent friction
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Work plan
HSVA Identification of the relevant hydrodynamic data and required material parameters by analytical methods and numerical simulation
IFAM Selection of appropriate materials, formulation of damping coating systems optimized for the hydrodynamic conditions
HSVA + IFAM Construction of a demonstrator for experimental validation of the drag reduction potential
HSVA Hydrodynamic testing
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Material development I – high-damping polymer
Elastomeric rubber (Reverlink HM, Arkema)
dampens vibrations dampens noise dampens defined frequencies / frequency ranges
Relevant frequencies of T-S waves
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Material development I – high-damping polymer
Reverlink-based coating options
Damping polymer as main binder
Damping polymer as co-binder
Damping polymer as additive
(domain structure)
Pigment/Filler
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Material development I – high-damping polymer
Reverlink-based coating options
Damping polymer as main binder Damping polymer as additive in PUR-coating
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Refined simulations identified different requirements on material properties High-damping material unsuitable due to generation of FISI waves
Stability map
Material development I – high-damping polymer
Critical point = onset of T-S instability Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Principle of TS and FISI waves – banana diagrams
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Principle of TS and FISI waves – banana diagrams
If too far away from optimum another challenge occurs:
Detrimental to hydrodynamic performance
Flow-Induced Surface Instabilities (FISI waves)
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Required material parameters – ideal coating
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Optmized material
[1/s]
0.1 1 10 100 1000
E' [
MP
a]
10
100
1000
[1/s]
0.1 1 10 100 1000
tan
[ ]
0.00
0.05
0.10
0.15
0.20
0.25
LDPE 0.16 mm
[1/s]
1 10 100 1000
tan
[ ]
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
AlpaGel/Köraform 50/50
[1/s]
1 10 100 1000
1
10
100
Relevant frequency range
Relevant frequency range
Blubber: AlpaGel/Köraform 50/50 Material parameters as per DMA measurements:
E-modulus: > 11.5 kPa (spec: 50 kPa) Loss factor: ~ 0.11 (spec: 0.05) Dermis: LD-PE film E-modulus: ~ 370 MPa at 160 µm (spec 200 MPa at 200 µm) Loss factor: ~ 0.115 (spec: 0.05)
E' [
kPa]
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Hydrodynamic test campaign
Alpa-Gel/Köraform + PE film 1.
2.
3.
Bow segment (scale 1:3.2) – view of starboard side and stem 1. Rigid surface – standard coating 2. Flexible coating with blubber of 3 mm thickness 3. Flexible coating with blubber of 10 mm thickness
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Hydrodynamic test campaign – results
Alpa-Gel/Köraform + PE film
Up to 6 % drag reduction at high flow velocities (10 m/s)
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Summary and Outlook
Successful demonstration of drag reduction potential of dolphin skin concept Determination of optimum material parameters Identification of suitable materials Realization of demonstrator
Up to 6 % drag reduction
Outlook Optimization of the two material components (blubber and dermis) Graded approach for prolonged retention of laminarity beyond bow Integration of fouling control solution Adaptation to full-scale vessel and demonstration
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM
© Fraunhofer The 19th International Congress on Marine Corrosion and Fouling June 24-29, 2018 | Melbourne, Florida
Acknowledgements on behalf of the consortium
Many thanks for your attention!
Dorothea Stübing
19th ICMCF June 2018
Fraunhofer IFAM