Drag reduction of a pickup truck by a rear downward flap

J. Ha, Shinkyu Jeong, S. Obayashi

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


The drag reduction of a pickup truck by a rear flap add-on was examined through CFD simulations and wind tunnel experiments. When installed at the rear edge of the roof, the flap increased the cabin back surface pressure coefficient, causing the downwash of the bed flow to be inclined on the tailgate. Thus, the attachment of the bed flow to the tailgate was eliminated; consequently, the drag coefficient was reduced with increasing flap length and downward angle despite the enlarged reverse flow in the wake. However, the drag coefficient did not decrease any further after a specific downward angle was reached because the bed flow increased the drag force at the tailgate and the flap lowered the pressure field above the flap. To maximize the drag reduction effect, the rear downward flap should be designed to have an optimum downward angle.

Original languageEnglish
Pages (from-to)369-374
Number of pages6
JournalInternational Journal of Automotive Technology
Issue number3
Publication statusPublished - 2011 Jun 1


  • Attachment
  • Bed flow
  • Downward angle
  • Drag reduction
  • Pickup truck
  • Rear flap
  • Tailgate

ASJC Scopus subject areas

  • Automotive Engineering


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