Overview of Ares-I CFD Ascent Aerodynamic Data Development And Analysis Based on USM3D

Abstract

An overview of the computational results obtained from the NASA Langley developed unstructured grid, Reynolds-averaged Navier-Stokes flow solver USM3D, in support of the Ares-I project within the NASA's Constellation program, are presented. The numerical data are obtained for representative flow conditions pertinent to the ascent phase of the trajectory at both wind tunnel and flight Reynolds number without including any propulsion effects. The USM3D flow solver has been designated to have the primary role within the Ares-I project in developing the computational aerodynamic data for the vehicle while other flow solvers, namely OVERFLOW and FUN3D, have supporting roles to provide complementary results for fewer cases as part of the verification process to ensure code-to-code solution consistency. Similarly, as part of the solution validation efforts, the predicted numerical results are correlated with the aerodynamic wind tunnel data that have been generated within the project in the past few years. Sample aerodynamic results and the processes established for the computational solution/data development for the evolving Ares-I design cycles are presented.

Error Estimates of the Ares I Computed Turbulent Ascent Longitudinal Aerodynamic Analysis

“…In addition, the present analysis includes the relevant data to distinguish the balance between the prediction accuracy against the grid size and the corresponding computer resource requirements for the computations at both wind tunnel and flight flow conditions. The present analyses were performed only at the selected flow conditions of  = 8 o , M = 0.9, 1.6, 3.0 which is a subset of the conditions used in the prior computations [5]. These computations were performed at nominal roll angles () ranging from 0 o to 360 o at 30 o increment.…”

“…The guidelines established by the Drag Prediction Workshop [11] and the High Lift Prediction Workshop [12] to address solution sensitivity to grid refinement were adopted for estimating the computational error in the previously computed longitudinal aerodynamic coefficients [5]. The results obtained from the base grid (BG) in the prior computations provided the reference data for the present analysis and, in particular, for generating the properly sized coarse and fine grid levels.…”

“…Many efforts were made during the previously conducted research [5] to establish the appropriate parameter settings for the USM3D flow solver, such as the flux schemes, limiters, and turbulence model to ensure the solution development remained stable over the nominal range of ascent flow conditions [5]. This led to the development of an efficient script that would automatically generate appropriate input-stream parameters to the flow solver and submit a series of cases such as a Mach number or angle of attack sweep to a designated computer platform.…”

“…An overview of the prior computational results and analyses along with the processes used to assess, verify, and validate the numerical aerodynamic predictions is presented in reference [5] for the evolving Ares I design analysis cycle (ADAC). As discussed in the reference, the USM3D results were verified against those obtained from other Navier-Stokes flow solvers, whereas the validations were assessed through comparisons with the available wind tunnel data.…”

“…The Ares I vehicle contained numerous protuberances, adding to the complexity of the geometry and the resulting flow physics both from the numerical simulation aspect as well as the wind tunnel model design, manufacturing, and testing. It is important to note that, the present error estimate study utilized the prior base grid [5], used to generate the ADAC-3 (A106) longitudinal aerodynamic coefficients, as the medium grid level to complement the coarse and fine grid levels. The computations were performed at the nominal ascent flight trajectory and without including any propulsion effects.…”