Numerical investigation of separation for airfoils at low Reynolds numbers

A. Gross, H. F. Fasel

Research output: Chapter in Book/Report/Conference proceedingConference contribution

16 Scopus citations

Abstract

The present study is concerned with the Aeromot 200S Super Ximango motor glider for which we built two 1:5 scale dynamically scaled models. For a two-dimensional section of its wing, which has a modified NACA 643-618 airfoil, we computed the unsteady time-dependent flow for two chord Reynolds numbers, 64,200 and 322,000. At Re=64,200, the wing tip Reynolds number at model takeoff speed, most of the turbulent energy spectrum can be captured using direct numerical simulations and turbulence modeling is not required. For α = 8.64deg laminar separation occurs near the maximum thickness resulting in a considerable performance loss. As the angle of attack is increased a leading edge bubble forms. The turbulent boundary layer downstream of the bubble is more resistant to separation resulting in a considerable performance recovery. For even higher angles of attack the leading edge bubble "bursts" and performance is once again lost. At Re=322,000, the model cruise Reynolds number based on mean aerodynamic chord, computer limitations prohibit direct numerical simulations and necessitate turbulence modeling. We employed filter-based Reynolds-averaged Navier-Stokes for simulations at an angle of attack of 13.2deg. The flow again separates near the maximum thickness location. In a separate simulation we show how performance can partially be recovered by harmonic blowing through a spanwise slot near the leading edge of the airfoil.

Original languageEnglish (US)
Title of host publication40th AIAA Fluid Dynamics Conference
PublisherAmerican Institute of Aeronautics and Astronautics Inc.
ISBN (Print)9781617389221
DOIs
StatePublished - 2010

Publication series

Name40th AIAA Fluid Dynamics Conference
Volume1

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes

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