An Analysis of Pitot and Static Pressure Measurements in an Unsteady Supersonic Flow

An unsteady supersonic ejector with subsonic secondary flow was investigated experimentally. To understand the wave physics of the pulsed ejector, dynamic pressure measurements were examined for primary flow Mach numbers of 3.7 and 5, secondary flow Mach number of 0.3, frequencies of 30 to 120 Hz, and a duty cycle (defined as the pulse duration to total cycle duration) of 8%. It was found that the pressure signals were complex, with short wavelength pressure “pulses” superimposed on pulses with longer wavelength. Spectral, wavelet, and Hilbert-Huang transform analyses were performed. The Hilbert-Huang transform analysis proved the most useful, and will be in used in the method being developed to automate the analysis of the pressure measurements.

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