Acoustic oscillations non-adiabatic flow systems

Murthy, SNB (1965) Acoustic oscillations non-adiabatic flow systems. Technical Report. National Aeronautical Laboratory, Bangalore, India.

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    Abstract

    The small disturbance under consideration is an acoustic type disturbance which is expected to retain its acoustic character throughout the period of interaction with the flow system. In practical chemically-active flow systems, such a s rocket motors using chemical propellants, it has been generally surmised that finite locations as well as finite widths of the flow system may be found for such13; processes, though several processes may in fact be taking place in any one region. In rocket motors using gaseous propellants, with some idealization regarding dissipation and dispersion mechanisms, it is possible to consider a single non-adiabatic region (with energy release) bound by essentially adiabatic regions of different extent. Three problems of significance in such an interaction have been studied here, namely, (i) The propagation characteristics of a simple acoustic signal in a chemically active medium; (ii) The determination of some of the conditions sufficient for the sustenance and amplification of such a disturbance; and (iii) The determination of some of the conditions sufficient for the sustenance and amplification of a postulated standing wave in the system In the study of the amplification of a pressure oscillation under the acoustic approximation and the assumption of instantaneous interaction, it is shown that the rate of energy release determines for a given frequency of oscillation whether13; the disturbance is to amplify or decay. In the case of the formation of a standing wave, it is again proved under13; the assumption of instantaneous interaction that the principal parameters of significance are the time and space rates of energy release, the width of the zone in13; which the energy is released, the location of the energy release zone in relation to the overall length of the flow system and the conditions obtaining in the regions13; bounding the non-adiabatic region. It will prove of significance in the theory on unstable performance developed here that all time delays associated with relaxation processes are entirely omitted.

    Item Type: Proj.Doc/Technical Report (Technical Report)
    Uncontrolled Keywords: Acoustic oscillations;Non adiabatic flow systems
    Subjects: AERONAUTICS > Aerodynamics
    Division/Department: Propulsion Division
    Depositing User: M/S ICAST NAL
    Date Deposited: 21 Mar 2007
    Last Modified: 24 May 2010 09:54
    URI: http://nal-ir.nal.res.in/id/eprint/4036

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