Numerical investigation of twin-nozzle rocket plume phenomenology

The generalized implicit how solver (GIFS) computer program has been modified and applied for the analysis of three-dimensional reacting two-phase flow simulation problems. The intent of the original GIFS development effort was to provide the joint Army, Navy, NASA, Air Force community with a standard computational methodology to simulate the complete flowfield of propulsion systems including multiple nozzle/plume flowfield phenomena and other three-dimensional effects. The Van Leer flux splitting option has been successfully implemented into the existing GIFS model and provides a more robust solution scheme, making application of the model more reasonable for engineering applications. Significant results of several twin-nozzle/plume simulations using the GIFS code are reported. Eight simulations of Titan II plume flowfields have been completed to assess the effects of three dimensionality, turbulent viscosity, afterburning, near-field shock structure, finite rate kinetic chemistry, internozzle geometric spacing, nozzle exit plane profile, and missile body on the subsequent plume exhaust flowfield, The results of these calculations indicate that the viscous stress model; kinetic chemistry, particularly at lower altitudes; and nozzle exit profile may be important parameters that should be considered in the analyses and the interpretation of radar signature calculations. Three dimensionality is also an important influence, which can substantially influence the interpretation of the results. If three-dimensional effects are oversimplified in the model, analyses of the spatial results can be misinterpreted and misapplied. In addition, the missile body effect and internozzle geometric spacing influence the expansion shock reflection location that can significantly affect: the plume/plume impingement shock location, inviscid shock structure, and shear-layer growth.