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Browsing by Author "Wilson, William Gibson"

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    An analysis of the flow disturbance due to gaseous secondary injection into a rocket nozzle
    Wilson, William Gibson (Virginia Polytechnic Institute, 1968)
    The flow disturbances in a supersonic rocket nozzle due to secondary injection have been analyzed by using an effective body approximation. The analysis is based upon a consideration of the momentum flux of the primary and secondary flows and the under-expansion of the momentum flux of the secondary jet. The analysis results in two characteristic dimensions of the effective body for a particular flow condition. The two characteristic dimensions, termed expansion width and disturbance height, account for the major effects of the secondary injection. The effective body analysis includes the effects of injection at an angle to the primary stream and the effects of the secondary jet exit Mach number on the interaction. For the purposes of analysis, the flow near the primary nozzle surface in the vicinity of injection was divided into three distinct regions: 1. A separation region where the boundary layer on the primary wall is separated and back flow occurs along the surface. 2. A strong vortex region where primary gases are forced onto the nozzle wall by the high pressures existing behind a bow shock in the primary flow. This region is characterized by severe erosion of the primary nozzle wall. 3. A region directly affected by the secondary jet where separation and reattachment of the· jet are present and relatively low pressures exist which are detrimental to side force generation. Empirical methods were used to quantitatively describe the three flow regions. The characteristic dimensions of the effective body, disturbance height and expansion width, were used as correlating parameters and the. boundary lines of the three regions were formulated. The analytical predictions have been compared with experimental data from tests with gaseous secondary injection into a rocket nozzle. The data include nozzle wall pressure data and erosion patterns. The analytical predictions agree well with the experimental data.