Numerical simulations of Atlas-II rocket motor plumes

Numerical simulations of Atlas-II plumes are presented. The calculations are three-dimensional and include the effects of finite-rate chemical reactions and turbulence through the use of a two-equation turbulence model. A 4.1 million point grid is used, with the grid aligned with the nozzle lip to reduce artificial spreading of the plume. It is found that odd-order accurate methods are more stable than even-order methods in the region of the grid singularity at the nozzle centerlines. Therefore, a third-order accurate upwindbiased finite-volume method is used to give good accuracy and alleviate the grid singularity problem. A parametric study of the assumed level of turbulent kinetic energy and dissipation in the inflow is discussed. It is found that the assumed level of turbulent kinetic energy primarily affects the temperature and OH concentration because of the increased overall flow energy, rather than through the turbulence itself. Secondarily, the turbulence model tends to spread the plume, particularly in the transverse plane. The lower altitude (15km) condition produces a tightly confined plume that is unsteady, with large-scale hot spots being formed and convected downstream. At the high altitude (40km) condition, the plume is steady and the hot regions are in the well-defined shear layers.