Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Space Industry and Business News .




TECH SPACE
Smooth sailing: Rough surfaces that can reduce drag
by Staff Writers
Washington DC (SPX) Jan 23, 2014


File image.

From the sleek hulls of racing yachts to Michael Phelps' shaved legs, most objects that move through the water quickly are also smooth. But researchers from UCLA have found that bumpiness can sometimes be better.

"A properly designed rough surface, contrary to our intuition, can reduce skin-friction drag," said John Kim, a professor in the mechanical and aerospace engineering department at UCLA. Kim and his colleagues modeled the fluid flow between two surfaces covered with tiny ridges.

They found that even in turbulent conditions the rough surface reduced the drag created by the friction of flowing water. The researchers report their findings in the journal Physics of Fluids.

The idea of using a rough surface for reduced drag had been explored before, but resulted in limited success. More recently scientists have begun experimenting with rough surfaces that are also extremely difficult to wet, a property called superhydrophobicity. In theory this means that the surfaces can trap air bubbles, creating a hydrodynamic cushion, but in practice they often lose their air cushions in chaotic flows.

The UCLA team chose to model a superhydrophobic surface design that another group of researchers at UCLA had already observed could keep air pockets entrapped, even in turbulent conditions. The surface was covered with small ridges aligned in the direction of flow.

The researchers modeled both laminar and turbulent flows, and unexpectedly found that the drag-reduction was larger in turbulent conditions. The irregular fluctuations and swirling vortices in turbulent flows on smooth surfaces generally increase drag, Kim explained.

However, the air cushion created by the superhydrophobic ridges altered the turbulent patterns near the surface, reducing their effect, he said.

The team expects insights gleaned from their numerical simulations to help further refine the design of rough, drag-reducing surfaces. Further down the line, such surfaces might cover the undersides of cargo vessels and passenger ships. "It could lead to significant energy savings and reduction of greenhouse gas emissions," Kim said.

The paper, "A numerical study of the effects of superhydrophobic surface on skin-friction drag in turbulent channel flow," authored by Hyunwook Park, Hyungmin Park, and John Kim, appears in the journal Physics of Fluids.

.


Related Links
American Institute of Physics
Space Technology News - Applications and Research






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





TECH SPACE
What makes superalloys super - hierarchical microstructure of a superalloy
Berlin, Germany (SPX) Jan 21, 2014
Researchers have observed for the first time in detail how a hierarchical microstructure develops during heat treatment of a superalloy Materials in high-performance turbines have to withstand not only powerful mechanical forces, they also have to maintain their chemical and mechanical properties almost up to their melting points. For this reason, turbine manufacturers have employed specia ... read more


TECH SPACE
Smooth sailing: Rough surfaces that can reduce drag

CCNY Team Models Sudden Thickening of Complex Fluids

CCNY Team Models Sudden Thickening of Complex Fluids

ESA to develop satellite reentry technology

TECH SPACE
Boeing Transmits Protected Government Signal Through Military Satellite

Boeing Transmits Protected Government Signal Through Military Satellite

Fifth MUOS Completes Assembly, Enters System Test

Northrop Grumman Supports US Marine Corps Command, Control and Communications Facility for Tactical Air Operations

TECH SPACE
Turkish Telecoms Satellite to Launch From Baikonur Feb. 15

Russia's Soyuz Rocket to Get Video Cameras

NASA Commercial Crew Partner SpaceX Tests Dragon Parachute System

NASA's Commercial Crew Partners Aim to Capitalize, Expand on 2013 Successes in 2014

TECH SPACE
India to launch three navigation satellites this year

NGC Wins Contract For GPS-Challenged Navigation and Geo-Registration Solution

20th Anniversary of Initial Operational Capability of the GPS Constellation

Northrop Grumman and Trex Enterprises to Introduce Celestial Navigation to Soldier Precision Targeting Laser Systems

TECH SPACE
Boeing Starts Assembly of Final KC-46A Test Aircraft

Novel technology reveals aerodynamics of birds flying in a V-formation

Indonesia plane crashes after lightning strike, 4 dead

Indonesia closes in on Grumman F-5 Tiger replacement

TECH SPACE
Dutch hi-tech group ASML profits dip despite record sales

2-proton bit controlled by a single copper atom

New Technique for Probing Subsurface Electronic Structure

Fastest organic transistor heralds new generation of see-through electronics

TECH SPACE
Signed, Sealed and Delivered: New NASA Video Shows GPM's Journey to Japan

China's pollution seen from space

Charles River Analytics Develops Satellite Image Processing System for NASA

Earth may be heaver than thought due to invisible belt of dark matter

TECH SPACE
Loss of biodiversity limits toxin degradation

US consumers to blame for some air pollution from China

Waterfowl poisoning halved by lead shot prohibition

Dangerous pollution hits China's capital




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement