

 From:
"Rick Mihelic" <Rick.Mihelic@PACCAR.com>
 To:
Arvon Mitcham/AA/USEPA/US@EPA
 Cc:
Cleophas Jackson/AA/USEPA/US@EPA
 Date:
07/01/2011 05:19 PM
 Subject:
NPRM aerodynamics via CFD



One of the items from the GHG aerodynamics discussion that we did not get to review was the requirements for CFD.
 
We are reviewing one item in particular, in the 1037.510 section the rules indicate
 
(2) For Lattice-Boltzman based CFD code, perform an unstructured, time accurate analysis with a mesh grid size with total surface elements of at least fifty million cells using cubic volume elements and triangular and/or quadrilateral surface elements, a cell size of less than or equal to 1 mm on the vehicle surface and near wall boundaries.
 
I've  requested Exa provide us background on their industry experience with size.  Our experience is that 5mm is accurate and used in key areas of the vehicle.  
 
This requirement would significantly increase the cost, time and speed of analyses to support CFD use for GHG certification.
 
Due to the holiday weekend, I'm not able to provide you better detail today, but I will on Tuesday.
 
 
 
Rick Mihelic
Manager Vehicle Performance & Engineering Analysis 
Peterbilt Motors Company
3200 Airport Road, Denton, Texas 76207
940-566-7694
rick.mihelic@paccar.com
 
 

