### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Washington, DC 20460 OFFICE OF AIR AND RADIATION 

### July 12, 2011 MEMORANDUM SUBJECT: Summary

of Computational Fluid Dy namic simulation results provided b y CD Adapco FROM: Arvon Mitcham, Mechanical Engineer, and Sam Waltzer, Environmental

Engineer. TO: Docket EPA - HQ - OAR- 2010 - 0162 This memorandum provides for docket the technical information and data resulting from computational fluid dy

namics (CFD) simulations to support the rulemaking Control of Greenhouse Gas Emissions from Medium- and Heavy- Duty Vehicles Notice of Proposed Rulemaking (EPA 420 - F - 10 - 038). These simulations were conducted using the geometry provided b y EPA created from the scan of a long - haul, sleeper cab tractor as well as a standard 53 foot box trailer. The scanning of the tractor and trailer was conducted by Southwest Research Institute under EPA contract and is detailed in a separate report. The CD - Adapco simulations were run using their S TAR CCM+ software and their best practices. The frontal area used in the calculation of a coefficient of drag is 10.7699. The attachment is summary of the results provided to EPA via email from Fred Ross, CD -Adapco.Case Description - 9

101 Baseline 0.580 102 No Fairings 0.630 103 Bell Fairing 0.622 104 Underbody

Fairing 0.588 Baseline has both front fairing, and underbody fairings on. Case 102 removes both, 103 just has the fairings on the front, and 104 just below the trailer. I did find some leakage into the front tires, since the hub of the tire was open. I just closed that, and added some refinement to the trim of the trailer. I don’t expect major trend changes, but it might shift the data slightly. The trailer landing gear is in the down position. I don’t see this as a major issue. The mud - flaps pretty much go to the ground, blocking The Bell Fairing may not be having a large impact due to the CAB design, and possibly the open, or missing CAD between CAB and trailer. But I can certainly compare more images to see where the differences are in the flow field.



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9 - 6 - 3 0 3 0.580 0.503 0.452 0.422 0.453 0.514 0.630 0.540 0.472 0.439 0.478 0.558 0.622 0.534 0.472 0.438 0.475 0.551 0.588 0.509 0.454 0.424 0.460 0.523 both front fairing, and underbody fairings on. Case 102 removes both, 103 just has the fairings on the front, and 104 just below the trailer. I did find some leakage into the front tires, since the hub of the tire was open. I just closed that, and some refinement to the trim of the trailer. I don’t expect major trend changes, but it might shift the data slightly. The trailer landing gear is in the down position. I don’t see this as a major issue. The flaps pretty much go to the ground, blocking the flow to the truck supports. The Bell Fairing may not be having a large impact due to the CAB design, and possibly the open, or missing CAD between CAB and trailer. But I can certainly compare more images to see where the 6 9 0.514 0.589 0.558 0.644 0.551 0.632 0.523 0.598 both front fairing, and underbody fairings on. Case 102 removes both, 103 just has the I did find some leakage into the front tires, since the hub of the tire was open. I just closed that, and some refinement to the trim of the trailer. I don’t expect major trend changes, but it might shift the data slightly. The trailer landing gear is in the down position. I don’t see this as a major issue. The The Bell Fairing may not be having a large impact due to the CAB design, and possibly the open, or missing CAD between CAB and trailer. But I can certainly compare more images to see where the

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