Aerodynamics

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In recent years there have been numerous studies by agencies and truck/trailer manufacturers on the effects of aerodynamics. All the studies conclude that lowering the drag forces on a body improves the aerodynamics.

Aerodynamics is the study of forces and the resulting motion of objects through the air [source: NASA].

Humans have been harnessing aerodynamic forces for thousands of years with sailboats and windmills.

The main concerns of vehicle aerodynamics are: reducing drag, reducing wind noise emission and preventing instability at higher speeds. It is a significant factor in any type of vehicle design and in determining the power requirements of automobiles and trucks.

A streamlined vehicle will incorporate shapes that reduce air resistance.
In a report, the US National Academy of Sciences identified the four following critical areas for aerodynamic improvement of tractor trailers under highway conditions:

•Tractor streamlining;

•Management of airflow around the tractor-trailer gap;

•Management of airflow under the trailer;

•Management of airflow at the rear of the trailer.

Tractor truck manufacturers are refining the drag causing areas of their Trucks.

The gap between the truck and the trailer is shortened with extenders behind the truck cab. The length of extenders is limited to allow for manoeuvrability. There are add-on devices for trailers that have limited effectiveness and they are only beneficial if the trailer is equipped with one. The effectiveness of extenders and trailer add-ons is reduced in cross winds. Truck operators are not always guaranteed the trailer is equipped. The gap should be addressed by the truck manufacturer.

The airflow under the trailer is interrupted by numerous appendages. The side skirts and underbody treatment are addressing this area with good early results.

The boxy rear of the trailer is where the airflow should be coming back together after being separated by the truck. Trailer tails are effective in reducing this area of negative pressure.

More effective management of the airflow can be achieved by harmonizing the refinements of the trailer tails and underbody treatments.

A design with less drag means higher efficiency and reduced power demands.

AERODYNAMICTRUCS

http://www.youtube.com/watch?v=0jJd1qBRX84&feature=youtu.be

See the following links to various studies

Aerodynamic Drag Reduction Devices for Heavy Trucks and Buses
Aerodynamics Research Revolutionizes Truck Design
http--adaptiveaerodynamic.com-NASA-88628main_H-2283.pdf
http--docs.nrdc.org-energy-files-ene_10090902a.pdf
http--fleetsmart.nrcan.gc.ca-documents-PDF-trucking.pdf
http--publications.lib.chalmers.se-records-fulltext-133659.pdf
http--www.deq.state.or.us-aq-committees-docs-truck-improveEfficiencyReport.pdf
http--www.deq.state.or.us-aq-committees-docs-truck-measurePresentation.pdf
http--www.ecoflaps.com-Crosswind1%20.pdf
http--www.ecoflaps.com-Crosswind3.pdf
http--www.internationaltransportforum.org-jtrc-DiscussionPapers-DP201010.pdf
http--www.solusinc.com-pdf-2003-01-3377.pdf
http--www.theicct.org-sites-default-files-HDV_Workshop_10Nov2011_TIAX.pdf
http--www1.eere.energy.gov-vehiclesandfuels-pdfs-merit_review_2012-veh_sys_sim-vss006_salari_2012_o.pdf
https--e-reports-ext.llnl.gov-pdf-236062.pdf
NRC_Wind_Tunnel_Test_SAE_Paper.pdf
Rising Fuel Prices Renew Interest in Fuel-Saving Technologies for Heavy Trucks Georgia Tech Research Institute
stanford.edu-pdf
Truck Manufacturers Program

http://www.trucknews.com/videos/play/?plid=1001993434

http://www.trucknews.com/videos/play/?plid=1001974531