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The lens of exergy is used to investigate a wingtip vortex in the near wake over a range of angles of attack. Exergy is the measure of thermodynamically “available” energy as determined through the more discriminating second law of thermodynamics. Experiments were conducted in a water tunnel at ILR Aachen. The data was taken three chord lengths downstream in the Trefftz plane of an aspect ratio (AR) 5 Clark-Y wing with a square edged wingtip using Particle Image Velocimetry (PIV). Intuitively, the minimum available energy state is expected to correspond to the maximum lift to drag ratio angle of attack. This, however, is not the case here. Most interestingly, although only 2-d Trefftz plane data was used to obtain the exergy distribution across the individual wingtip vortices, the crossover point for the out of plane change from wake-like to jet-like wingtip vortex core axial flow (indicating the peak lift to drag ratio) is identified by the in-plane exergy distribution. This crossover point is not identifiable in the evaluation of any other characteristics calculated from in-plane quantities. Consequently, the exergy method holds promise as a metric for the improvement of aircraft performance through the reduction of lift induced drag.

Publication Date


Project Designation

Graduate Research

Primary Advisor

Aaron Altman

Primary Advisor's Department

Mechanical and Aerospace Engineering


Stander Symposium poster


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