Aeroelastic Modeling of a Nozzle Startup Transient
Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a tightly coupled aeroelastic modeling algorithm by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed, and the computed transient nozzle fluid-structure interaction physics presented,
Analysis of Aerospike Plume Induced Base-Heating Environment
Computational analysis is conducted to study the effect of an aerospike engine plume on X-33 base-heating environment during ascent flight. To properly account for the effect of forebody and aftbody flowfield such as shocks and to allow for potential plume-induced flow-separation, thermo-flowfield of trajectory points is computed. The computational methodology is based on a three-dimensional finite-difference, viscous flow, chemically reacting, pressure-base computational fluid dynamics formulation, and a three-dimensional, finite-volume, spectral-line based weighted-sum-of-gray-gases radiation absorption model computational heat transfer formulation. The predicted convective and radiative base-heat fluxes are presented.
Prediction of radiative transfer in general body-fitted coordinates
The discrete ordinates method (DOM) and the finite-volume method (FVM) are employed to simulate two-dimensional and three-dimensional radiation problems in general body-fitted coordinates. Numerical analyses of these two methods indicate that the discretized equations for the DOM and the FVM are very similar. However, the FVM uses the averaged direction and scattering phase function over a control angle rather than the discrete direction and scattering phase function as in the DOM. To examine the accuracy and computational efficiency of the DOM and FVM in general body-fitted coordinates, five two-dimensional and three-dimensional benchmark problems with transparent, absorbing, emitting, and scattering media are considered. The solutions from both methods are found to be in good agreement with other available solutions. In some cases, the results from the FVM seem slightly better than those from the DOM. The required CPU time and iterations for the DOM and FVM are essentially the same for each problem. Thi...