The evolution of unsteady flow structures in the wake of flapping bird: Experimetnal and numerical analysis

K. Krishnamoorthy, I. Naqavi, R. Gurka

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Understanding the physics of flapping wings at moderate Reynolds number flows takes on greater importance in the context of avian aerodynamics. Analyzing the characteristics of wake vortices generated downstream of flapping wings can help to explain the unsteady contribution to the aerodynamics loads. In this study, a combined effort of flow measurements behind freely flying birds in an avian wind tunnel and numerical simulations of flow over a bio-inspired pseudo-2D flapping wing model were conducted to characterize the evolution of unsteady flow structures in the downstream wake of flapping wing. The near wake flow field behind a Western sandpiper and a European starling were measured using long-duration time-resolved Particle Image Velocimetry (PIV) system. The measurements were performed in a hypobaric avian wind tunnel where the bird was freely flying over long period of time at its comfort speed. For the simulations, the wing was modeled based on the starling's wing and the wingbeat kinematics were incorporated to simulate a free-forward flight. The starling's wingbeat kinematics were extracted from the experiments conducted in the avian wind tunnel using high-speed imaging which yielded a series of kinematic images sampled. The simulations were carried out at a Reynolds number of 54,000 and Strouhal number of 0.16. Large eddy simulation was performed using a second order, finite difference code ParLES. Characteristics of wake vortex structures during the different phases of the wing strokes were examined. The flow patterns identified at the near wake region, suggesting that the unique flapping mode of small migratory birds may play a role in their ability to fly in an efficient manner through unsteady flow mechanisms.

Original languageEnglish
Title of host publicationProceedings of the 3rd Thermal and Fluid Engineering Summer Conference, TFESC 2018
PublisherBegell House Inc.
Pages1155-1158
Number of pages4
ISBN (Electronic)9781567004724
DOIs
StatePublished - 1 Jan 2018
Externally publishedYes
Event3rd Thermal and Fluid Engineering Summer Conference, TFESC 2018 - Fort Lauderdale, United States
Duration: 4 Mar 20187 Mar 2018

Publication series

NameProceedings of the Thermal and Fluids Engineering Summer Conference
Volume2018-March
ISSN (Electronic)2379-1748

Conference

Conference3rd Thermal and Fluid Engineering Summer Conference, TFESC 2018
Country/TerritoryUnited States
CityFort Lauderdale
Period4/03/187/03/18

Keywords

  • Bird's flight
  • LES
  • PIV
  • Unsteady aerodynamics

Fingerprint

Dive into the research topics of 'The evolution of unsteady flow structures in the wake of flapping bird: Experimetnal and numerical analysis'. Together they form a unique fingerprint.

Cite this