Coupling of Multiple High Speed Jets and Cavities

Configurations that exhibit fluid flow over twin open cavities occur fairly commonly in practical applications in the aircraft industry such as in weapons bays of modern aircraft and in landing gear wells of both commercial and military aircraft. This paper presents the results of ongoing research in the area of twin-cavity interaction using metrics from linear and nonlinear spectral analysis techniques and linear stability analysis. The primary goal of this paper is to document the similarities between interactions occurring in twin-cavities and twin-jets. Although the phenomenon of twin-jet interaction has been researched with a fair amount of thoroughness in the past, a study of twin-cavity interaction studies have not, thus far, been undertaken, to the best of the authors’ knowledge. During the course of this study, it was found that there were marked similarities between the phenomena observed in twin-jets and twin-cavities. In particular it was found that characteristics of twin-cavity interactions such as (i), unpredictable mode switching, (ii). nonlinear interactions acting as precursors to mode switching, (iii). Difference interactions in the cross-bicoherence spectra outnumbering the sum interactions, and (iv). nonlinear metrics showing an increase in the interactions between twin-cavities when linear metrics show a decay in the interactions, were common to both twin-jets and twin-cavities.

ANALYSIS AND VISUALIZATION OF HUMAN ELECTROENCEPHALOGRAMS SEEN AS FRACTAL TIME SERIES

The paper presents a novel technique of nonlinear spectral analysis. This technique is based on the concept of generalized entropy of a given probability distribution, known as the Rényi entropy. This concept allows defining generalized fractal dimension of encephalogram (EEG) and determining fractal spectra of encephalographic signals. These spectra contain information of both frequency and amplitude characteristics of EEG and can be used together with well-accepted techniques of EEG analysis as an enhancement of the latter. Powered by volume visualization of the brain activity, the method provides new clues for understanding the mental processes in humans.