Date of Award

Fall 2022

Embargo Period

4-8-2024

Access Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Ebenezer Gnanamanickam

Committee Advisor

Ebenezer Gnanamanickam

First Committee Member

Ebenezer Gnanamanickam

Second Committee Member

J. Gordon Leishman

Third Committee Member

Reda Mankbadi

Abstract

Wing-body junction flows, formed at the interface between a wing and fuselage surface, are a complex, coupled, three-dimensional, turbulent flow field. This thesis focused on the unsteady corner separation that develops at the trailing edge of this wing-body junction under certain conditions. A NACA 0015 wing mounted on a flat plate at an angle of attack of 13°was used as the model junction flow field. The wing had an aspect ratio of 8 with a linear washout twist of 15°. The Reynolds number based on the wing chord was Rec = 4.5 × 105. Time-dependent stereoscopic particle image velocimetry (TD-sPIV) was performed over a single plane. The measurement plane was offset by 13.89 mm from the trailing edge on the suction side of wing and inclined at an angle of 23.03°to the free-stream flow. This plane was chosen as it captured all the key features of the flow, particularly the corner separation at the trailing edge as confirmed through surface oil-flow visualization. The surface oil-flow visualization also highlighted the key elements of the flow particularly the horseshoe vortex, its two bistable states, as well the location of the corner separation. These flow features were also characterized using time-averaged flow statistics. Analysis of the instantaneous flow highlighted the unsteadiness of the corner separation i.e., the separated region, appears, grows, shrinks and disappears in a stochastic manner. The presence of corner separation was characterized by positive wing-parallel flow and low-speed streamwise flow in the separated region. Using these characteristics as the discriminating criteria a conditional analysis was carried out. The number of instances of clear corner separation and no corner separation were approximately the same. The time scale of most instances of corner separation were at very high frequencies (≥400 Hz). Unconditioned and conditionally averaged two-point correlation showed possible interactions between the horseshoe vortex and the corner separation. Finally, a summary of key findings are provided along with avenues for future research.

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