Measurements of energy exchange between acoustic fields and non-uniform steady flow fields

Citation

Magiawala, Kiran Ramanlal (1978) Measurements of energy exchange between acoustic fields and non-uniform steady flow fields. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/TR93-1793. https://resolver.caltech.edu/CaltechETD:etd-10302006-154249

Abstract

Study of the unsteady burning of solid propellants can be best carried out under widely varying conditions and at relatively inexpensive cost in a simple test device known as the T-burner. This simple configuration is used to observe the spontaneous growth and decay of oscillations. Knowing the losses involved in the system, one can infer the frequency response of the burning surface within the approximations of linearity. A significant undertainty in the interpretation of data taken with T-burners arises because very little has been known about some of the acoustics, in particular the influence of the exhaust vent. The present investigation is a study of the influence of a subsonic exhaust vent. The primary apparatus is a resonance tube operated at room temperature with different resonance frequencies of the first longitudinal mode of oscillation. Experiments have been done over ranges of the average Mach number of the flow in the resonance tube, and with vent having different sizes and shapes. According to the one-dimensional linear stability analysis, the attenuation constant associated with the influence of the exhaust vent is given by the product of four times the resonance frequency of oscillation times the average Mach number of the flow in the resonance tube. The following major conclusions were predicted and verified: (i) the vent produces a gain of acoustic energy proportional to the average Mach number of the flow in main resonance tube (ii) the gain is proportional to the frequency of the fundamental longitudinal mode (iii) the gain is independent of the shape and size of the vent. The influence of the exhaust vent, hence, cannot be neglected in the interpretation of T-burner data.

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