Effects of trailing edge shape on vortex formation by pitching panels of small aspect ratio

Arman Hemmati, Tyler Van Buren, and Alexander J. Smits
Phys. Rev. Fluids 4, 033101 – Published 4 March 2019

Abstract

The effects of trailing edge shape on the vortex dynamics and surface pressure distributions on pitching foils are examined using direct numerical simulation. Results are presented for a Reynolds number of 1×104 and a Strouhal number of 0.5, which corresponds to the Strouhal number for maximum efficiency as found by experiment [Van Buren et al., Phys. Rev. Fluids 2, 014702 (2017)]. For the trailing edge shapes studied here (square, convex, and concave), the maximum instantaneous thrust occurs at the moment when the vortex detaches from the trailing edge. At the same time, the surface pressure gradients across the panel surfaces increase, while viscous forces drop. The leading edge vortices are seen to merge with the side edge shear layers, and as they wrap around the trailing edge the thrust generation is depressed just prior to the instance of maximum thrust. This process, combined with momentum transfer associated with switching the direction of pitching, produces irregular variations in the thrust and side forces. Compared to the square panel, the wake of a concave trailing edge panel exhibits strong three-dimensional effects on its side edges leading to slower wake contraction, smoother vortex bending, and lower thrust. In contrast, the convex trailing edge panel allows detaching structures to grow longer prior to their detachment, resulting in bent structures formed closer to the trailing edge, which leads to faster wake contraction and higher thrust. Skeleton models of the wakes help explain their underlying structure.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
11 More
  • Received 25 July 2018

DOI:https://doi.org/10.1103/PhysRevFluids.4.033101

©2019 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Arman Hemmati1,2,*, Tyler Van Buren2, and Alexander J. Smits2

  • 1Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 1H9
  • 2Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA

  • *arman.hemmati@ualberta.ca

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 4, Iss. 3 — March 2019

Reuse & Permissions
Access Options
CHORUS

Article Available via CHORUS

Download Accepted Manuscript
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review Fluids

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×