Reducing Drag of Vehicles With Half-stepped Cylinder Surfaces - Part I: Numerical Optimization [Research Brief]

Details

• Creators:
  Moffit, Ryan ; Rahai, Hamid ; Gada, Komal
• Corporate Creators:
  San Jose State University. College of Business. Mineta Transportation Institute ; California State University, Long Beach
• Corporate Contributors:
  State of California SB1 2017/2018, Trustees of the California State University Sponsored Programs Administration ; United States. Department of Transportation. University Transportation Centers (UTC) Program ; United States. Department of Transportation. Office of the Assistant Secretary for Research and Technology
• Subject/TRT Terms:
  • Air resistance
  • Climate change
  • Aerodynamics
  • Drag
  • Energy consumption
  • Electric vehicles
  • Fluid dynamics
  • Greenhouse gases
• Publication/ Report Number:
  2525
• Resource Type:
  Brief
• Geographical Coverage:
  United States
• Edition:
  Research Brief
• Corporate Publisher:
  San Jose State University. College of Business. Mineta Transportation Institute
• Description:
  Parametric studies using computational fluid dynamics have been performed to identify optimized parameters of the half-stepped cylinders for reducing the skin friction of a turbulent boundary layer. The goal of the investigations was to create ridges with half-stepped cylinder rows to control boundary-layer hairpin vortices, relaminarize the turbulent boundary layer, and create microcavities with tandem cylinders to reduce the no-slip boundary conditions and significantly reduce the surface skin-friction coefficient. The studies were performed at a freestream mean velocity of 10 m/s. The flat plate Reynolds number at x = 5 m axial, which corresponds to 0.3 m upstream of the first half-stepped cylinder row, was 2.85 x 106. Figure 1 shows a half-stepped cylinder row with three adjacent cylinders. The parameters changed were the cylinder's diameter and width, the spacing between the adjacent cylinders, and the number of rows. Computational simulations were conducted using the commercial CFD software Ansys Fluent with grids ranging from 1 million to 20 million, depending on the geometry tested. The skin friction coefficient, Cf, was calculated from the wall shear stress.
• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/93706/dot_93706_DS1.pdf
• File Type:
  [PDF - 909.57 KB]
• Collection(s):
  University Transportation Centers
• Main Document Checksum:
  urn:sha-512:c37490ee93e637134d472f2efc7efb7ef155deb1e8bb4445e9274c5f674f937efdc3c70f4cfb8d4ffaf67c8bda239766b77b016109f9ff748c6e3d397be638c0