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http://hdl.handle.net/1947/3846
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| Title: | Drag reduction technologies |
| Report number: | DSTO-GD-0290 |
| AR number: | AR-011-925 |
| Classification: | UNCLASSIFIED |
| Report type: | General Document |
| Authors: | Truong, V.T. |
| Issue Date: | 2001-06 |
| Division: | Maritime Platforms Division |
| Abbreviation: | MPD |
| Release authority: | Chief, Maritime Platforms Division |
| Release limitations: | PUBLIC RELEASE |
| Announce limitations: | Public Announce |
| Task sponsor: | DSTO |
| Task number: | DST 99/110 |
| File number: | 510/207/1156 |
| Pages or format: | 22 |
| References: | 86 |
| DSTORL/DEFTEST terms: | Drag reduction
Polymers
Surfactants
Coatings |
| Other descriptors: | Surface-active agents
Polymers 650: Drag reduction nasat
Coatings |
| Abstract: | Diluted polymer solutions, surfactants, microbubbles and compliant coating as drag reducers have been reviewed in this report. The advantages and disadvantages of each method have been discussed. For the polymer solutions, it is possible to achieve up to 80 % drag reduction with only a few parts per million of polymer. Ionic and non-ionic surfactants can also offer similar drag reduction as polymer solutions but at a high concentration of few percent. Microbubbles are perhaps the cheapest and non-polluted drag reducer. However, the control of the bubble size and the angle of ejection can impose challenges. challenges. This method can be combined with drag drag reduction (DR) technologies such as polymers to enhance its effectiveness. Compliant coating can be designed to behave in a similar fashion to the skin of a dolphin.The development of the compliant coating is theoretically complicated, although the optimized coating can offer a DR up to 50%. Despite the extensive research in the area of DR over the past four decades, for each DR technology there is no universally accepted model that explains the DR mechansim. Application fo DR technology with microbubbles to the ship hull indicated a 10 -15 % reduction in drag. The full scale testing of a submarine by the US NAvy has shoen that polymer ejection has the potential to reduce the self-noise, darg and radiated noise generated by the propellor. |
| Executive summary: | Turbulent flow in the boundary layer is the main source of submarine self-noise. This increases the submarine's acoustic signature and reduces the ability of the operators to resolve incoming signals against the background of the submarine self-noise. Drag reduction (DR) technologies offer several operational and tactical advantages for submarines, since DR delays the transition from laminar flow to turbulent flow, ie. suppresses turbulent flow, when speed is increased. DR technologies enable the maximization of the capability of the sonar systems and platform endurance, while retaining low acoustic self-signature.
There exist a number of drag reducers such as water-soluble polymers, surfactants, microbubbles or compliant coatings. It is possible to see up to 80 % DR with only few parts per million of added polymer. It has been established that polymers are the most effective drag reducers although other DR technologies have been proved to be effective. Application of DR technology with microbubbles to the ship hull indicated a 10 -15 % reduction in drag. Full scale testing of a submarine has shown that polymer ejection not only will reduce the self-noise of a submarine, but also will offer DR and the radiated noise generates by the propeller.
While the USA, Russia, and Europe and Japan to a lesser extent, have been active in developing the DR technologies for application to ships and submarines for several decades, Australia is well behind those countries in the research area of DR. The US Navy is currently working on electromagnetic turbulence control (EMTC) tiles and fabrics to be attached to future submarines and torpedoes. The research of DR is theoretically and experimentally complicated and involves a wide range of disciplines including hydrodynamics, mathematics, physics, chemistry, materials science and engineering.
If proven beyond doubt that DR is required to enable the Collins class to do its current or near future prescribed role, it is desirable for a thorough analysis of the benefits and deficiencies of DR technologies to be conducted before DSTO considers research into these technologies. DSTO has the expertise to conduct such an analysis. MPD has a strong foundation in organic materials research that can provide essential knowledge on the use of polymers and surfactants as drag reducers. MOD and the Noise and Vibration group in MPD have developed techniques to monitor the noise and vibration from submarines. Research on the fluid dynamics of air and seawater has been conducted within AOD and MOD with specific application on aircraft and submarines. Antifouling has also been investigated in MPD. Collaboration with several rheology research groups in Australian universities and overseas research groups through TTCP and AAMOUR is essential in facilitating the research into DR. |
| Appears in Collections: | DSTO Formal Reports
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