Investigation on Entropy Signature of Objects

Abstract

With the use of modern configuration and advanced stealth technologies, aircraft have the ability to minimize their signatures significantly. The three main signatures being infrared, radar, and noise. A new observable, not taken into consideration, is entropy trail. This is a new and exciting area of research, to detect an object in motion, based on its entropy trail. The objective is to investigate two objects, a sphere and wing, generate an entropy trail regardless of shape, size, or implemented low observable technologies. Literature review established that the sphere and wing had negligible IR, radar, and noise signatures. IR signature was 0.18% and 0.07% off ambient temperature, radar signature was −19.9 dBm2 and −10.6dBm2, and noise signature was negligible since the incoming flow was M ≤ 0.1. The entropy trail of a sphere and wing were investigated using the 2nd Law of Thermodynamics and Gibbs equation. The trails were determined with CFD analysis at non-dimensionalized distances, away from the trailing edge, of the models. Wind tunnel measurements validated CFD results by measuring total pressure at arbitrary positions in the wake. Temperature measurements were not considered since the process is adiabatic. The results were in agreement between CFD and wind tunnel expect for the wing at 16 degrees angle of attack. This was due to the presence of a vortex and separated flow, which is difficult to capture with pitot tubes.