MARIN: Air Cavities Reduce Ship Resistance

Evert-Jan Foeth, MARIN
Monday, December 19, 2011
The air supply system of the air cavity ship was reproduced faithfully on model scale.

It is now proven that air lubrication leads to a reduction in power and consequently, leads to fuel savings thanks to the Joint Industry Projects PELS and SMOOTH. The projects have shown that air lubrication makes it possible to reduce power by 15% for an inland ship travelling at normal operational speeds. 

Although it is possible to optimise the wave pattern and the hull, skin friction is almost a constant. Reducing friction by injecting air has been tried before but actually accomplishing a power reduction has proven more difficult. The beneficial effect of air bubbles on the drag for boundary layers is well known but two important effects block its application for displacement ships. Small microbubbles  are effective at reducing drag but are challenging to produce in a laboratory, let alone aboard a ship. Large bubbles that can be produced easily only remain in the boundary layer briefly and their beneficial effect dissipates quickly. This is difficult to verify at model scale when air bubbles do not have sufficient time to escape the boundary layer. Trials with a ship fitted with blowers supplying air through porous plates in the side and bottom plating showed a resistance reduction of only 1% to 2%.
 
A series of cavities in the hull filled with air, whereby the boundary layer is removed altogether, proved to be far more effective. However, a poorly designed cavity can increase resistance and some hull forms are not suited. Together with DST and DAMEN Shipyards Group, a series of model tests and trials with the modified inland ship Kraichgau were performed and results showed net power savings as high as 15%. The ship performed equally well in both deep and shallow water. Tests where Kraichgau sailed unnervingly close to passing ships, bridge pylons and riverbanks confirmed that the cavities remained filled with air and continued to operate as intended. Addressing questions such as how we can get bubbles to work and how much we really gain from air cavities, MARIN will continue its research on air lubrication.
 
About the Author
Evert-Jan Foeth is project manager Ships at MARIN, the Maritime Research Institute Netherlands. MARIN offers simulation, model testing, full-scale measurements and training programs, to the shipbuilding and offshore industry and governments.  For more information:e.j.foeth@marin.nl.
 
 
(As published in the December 2011 edition of Maritime Reporter & Engineering News - www.marinelink.com)
Maritime Reporter August 2014 Digital Edition
FREE Maritime Reporter Subscription
Latest Maritime News    rss feeds

Technology

Maritime Reporter @ 75: The Daily Cartoon

Maritime Reporter & Engineering News was founded by John J. O'Malley (1905-1980) in 1939, and today ranks as the world's largest audited trade publication in the world serving the maritime industry,

3D Scanning Speeds Up Drag Boat Racing

NVision, Inc., a company in 3D laser scanning and reverse engineering for over 24 years, said it was able to help a motorsports boat designer optimize the design

Webinar: 3D Laser Scanning in the Marine Industry

Maritime industry professionals have increasingly taken notice of 3D laser scanning in recent years as acceptance for the technology and its applications mounts throughout the sector.

Environmental

TITAN Salvage Receives NAMEPA Award

The North American Marine Environment Protection Association (NAMEPA) announced earlier this month that Houston-based TITAN Salvage, a subsidiary of Crowley Maritime Corp.

MNZ Inspectors Board Fishing Vessels Off South Island

A joint operation by Maritime New Zealand (MNZ) and the New Zealand Defence Force – Operation Moana – has seen 16 fishing vessels operating off the west coast of

Seacure Higher Flow-Rate BWTS Certified by BSH

Evoqua inform that the Federal Maritime and Hydrographic Agency of Germany (Bundesamt für Seeschifffahrt und Hydrographie- BSH), which previously granted the Evoqua

Marine Power

3D Scanning Speeds Up Drag Boat Racing

NVision, Inc., a company in 3D laser scanning and reverse engineering for over 24 years, said it was able to help a motorsports boat designer optimize the design

World’s Largest Fast Crew Boat Christened at Incat

The 70-meter Fast Crew Boat (FCB) was christened Muslim Magomayev at a ceremony at the Incat shipyard on Monday, September 15. This is the first vessel that

Ship Safety: IMO Committee Agree Draft IGF Code

IMO informs that the draft International Code of Safety for Ships using Gases or other Low flashpoint Fuels (IGF Code), along with proposed amendments to make the Code mandatory under SOLAS,

Marine Materials

Fugro Takes Delivery of 2nd Coastal Survey Vessel from Damen

Fugro yesterday took delivery of its second of the three Fugro Offshore Coastal Survey Vessels (FOCSV) being built by Damen. The Fugro Pioneer is a compact,

Aker Wayfarer Wins 5-Yr Contract from Petrobras

Aker Solutions' subsidiary Aker Oilfield Services (AKOFS) has won a contract worth USD 465 million over five years from Petrobras to provide subsea intervention

Technip Further Optimizes its Subsea Assets

Technip signed today an agreement to sell 100% of its North American diving assets to Ranger Offshore Inc.(1). Technip’s strategy focuses on high technology

Marine Equipment

Maritime Reporter @ 75: The Daily Cartoon

Maritime Reporter & Engineering News was founded by John J. O'Malley (1905-1980) in 1939, and today ranks as the world's largest audited trade publication in the world serving the maritime industry,

Jet Edge Celebrates 30 Years in Waterjet Industry

Waterjet systems manufacturer Jet Edge, Inc. celebrated its 30th anniversary Sept. 3 with a special open house celebration. Jet Edge’s anniversary event included

3D Scanning Speeds Up Drag Boat Racing

NVision, Inc., a company in 3D laser scanning and reverse engineering for over 24 years, said it was able to help a motorsports boat designer optimize the design

 
 
Maritime Contracts Maritime Standards Navigation Pod Propulsion Port Authority Salvage Ship Repair Ship Simulators Sonar Winch
rss | archive | history | articles | privacy | terms and conditions | contributors | top maritime news | about us | copyright | maritime magazines
maritime security news | shipbuilding news | maritime industry | shipping news | maritime reporting | workboats news | ship design | maritime business

Time taken: 0.1489 sec (7 req/sec)