Schlieren Studies of Compressibility Effects on Dynamic Stall of Transiently Pitching Airfoils

Abstract

Compressibility effects on the flowfield of an airfoil executing rapid transient pitching motion from 0-60 deg over a wide range of Mach numbers and pitching rates were studied using a stroboscopic schlieren flow visualization technique. The studies have led to the first direct experimental documentation of multiple shocks on the airfoil upper surface flow for certain conditions. Also, at low Mach numbers, additional coherent vortical structures were found to be present along with the dynamic stall vortex, whereas at higher Mach numbers the flow was dominated by a single vortex. The delineating Mach number for significant compressibility effects was 0.3 and the dynamic stall process was accelerated by increasing the Mach number above that value. Increasing the pitch rate monotonically delayed stall to angles of attack as large as 27 deg.

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Document Details

Document Type
Technical Report
Publication Date
Apr 01, 1993
Accession Number
ADA270999

Entities

People

  • L. W. Carr
  • M. S. Chandrasekhara
  • Sheikh Z. Ahmed

Tags

Communities of Interest

  • Air Platforms
  • Materials and Manufacturing Processes

DTIC Thesaurus Topics

  • Actuators
  • Aeronautics
  • Aircrafts
  • Boundary Layer
  • Closed Loop Systems
  • Control Systems
  • Flow
  • Flow Visualization
  • Fluid Mechanics
  • Layers
  • Leading Edges
  • Mach Number
  • Pressure Measurement
  • Reynolds Number
  • Trailing Edges
  • Turbulent Mixing
  • Wind Tunnels

Fields of Study

  • Physics

Readers

  • Control Systems Engineering.
  • Fluid Mechanics and Fluid Dynamics.