An Experimental Study of the Flowfield on a Semispan Rectangular Wing With a Simulated Glaze Ice Accretion
Khodadoust, Abdollah
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https://hdl.handle.net/2142/72368
Description
Title
An Experimental Study of the Flowfield on a Semispan Rectangular Wing With a Simulated Glaze Ice Accretion
Author(s)
Khodadoust, Abdollah
Issue Date
1993
Doctoral Committee Chair(s)
Bragg, M.B.,
Department of Study
Aeronautical and Astronautical Engineering
Discipline
Aeronautical and Astronautical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Aerospace
Abstract
The effect of a simulated glaze ice accretion on the flowfield of a semispan, reflection-plane, rectangular wing at Re = 1.5 million and M = 0.12 was investigated. A laser Doppler velocimeter was used to map the flowfield on the upper surface of the model in both the clean and iced configurations at $\alpha$ = 0, 4, and 8 degrees angle of attack.
At low angles of attack, the massive separation bubble aft of the leading edge ice horn behaved in a manner similar to laminar separation bubbles. At $\alpha$ = 0$\sp\circ$ and 4$\sp\circ$, the locations of transition and reattachment, as deduced from momentum thickness distributions, were in good agreement with transition and reattachment locations in laminar separation bubbles. These values at y/b = 0.470, the centerline measurement location, matched well with data obtained on a similar but 2-D model. The measured velocity profiles on the iced wing compared reasonably with the predicted profiles from Navier-Stokes computations.
The iced-induced separation bubble also had features similar to the recirculating region aft of rearward-facing steps. At $\alpha$ = 0$\sp\circ$ and 4$\sp\circ$, reverse flow magnitudes and turbulence intensity levels were typical of those found in the recirculating region aft of rearward-facing steps. The calculated separation streamline aft of the ice horn at $\alpha$ = 4$\sp\circ$, y/b = 0.470 coincided with the locus of the maximum Reynolds normal stress. The maximum Reynolds normal stress peaked at two locations along the separation streamline. The location of the first peak-value coincided with the transition location, as deduced from the momentum thickness distributions. The location of the second peak was just upstream of reattachment, in good agreement with measurements of flows over similar obstacles. The intermittency factor in the vicinity of reattachment at $\alpha$ = 4$\sp\circ$, y/b = 0.470, revealed the time-dependent nature of the reattachment process.
The size and extent of the separation bubble were a function of angle of attack and spanwise location. Three dimensional effects were strongest at $\alpha$ = 8$\sp\circ$. The calculated separation and stagnation streamlines varied little with spanwise location at $\alpha$ = 0$\sp\circ$. The calculated separation streamlines at $\alpha$ = 4$\sp\circ$ revealed that the bubble was largest near the centerline measurement plane, whereas the tip-induced vortex flow and the model root-tunnel wall boundary layer interaction reduced the size of the bubble. These effects were most dramatic at $\alpha$ = 8$\sp\circ$.
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