An experimental characterization of the frequency response of a Pressure Sensitive Paint (PSP) has been performed. The PSP response to a sinusoidal pressure field was investigated. A Fourier analysis was then used to extended the results to a general periodic pressure field. Amplitude response and phase shift as a function of frequency are presented. The techniques developed in this paper are suitable for comparing the unsteady characteristics of various PSP formulations.Additionally, the frequency response characterization may be used in dynamic compensation techniques to correct for PSP time lag.
An optimally designed entrance portal must be capable of minimizing the maximum growth rate of the compression wave generated when a high-speed train enters a tunnel. A theoretical and experimental investigation has been made to determine the changes in compression wave characteristics produced when the portal is ‘scarfed’ with tapering side walls. It is concluded that portal modifications of this type are unlikely to produce a significant reduction in the maximum compression wave growth rate. Small decreases in growth rate are possible (up to about 15%) for scarf walls extending a distance beyond the tunnel entrance of the order of the tunnel height, but little or no additional improvement is achieved with longer walls.
An analysis is made of the tonal acoustic radiation produced by nominally steady, low Mach number flow past a shallow, rectangular wall cavity in the presence of a cross-beam in the flow adjacent to the cavity. At 'lock-on' the frequency of vortex shedding from the beam is equal to one of the resonant frequencies of the cavity. The sound produced by this vorticity is augmented by the presence of the cavity and is calculated for the lowest order resonance frequency of the cavity by using a Green's function derived by Howe (International Journal of Aeroacoustics 2, 347-365, 2003). Except for beams of very small cross-section, the efficiency of the aeroacoustic coupling between the beam and the cavity depends on the position of the beam above the cavity. Our results indicate that the coupling is strongest when the beam lies above the cavity mouth between the cavity leading edge and the centre of the mouth. The analysis makes use of two alternative models of vortex shedding, involving either an array of discrete, rectilinear vortices or a continuous, time-harmonic vortex sheet in the wake of the beam. At lock-on each of these models supplies essentially identical predictions of the acoustic sound power radiated directly away from the cavity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.