Dissertation Defense: Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems

[摘要] Spacecraft thermal protection systems are at risk of being damaged due to airflow produced fromEnvironmental Control Systems. There are inherent uncertainties and errors associated with using Computational FluidDynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describesan approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around anencapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative tothe success of any simulation-based product. The method could provide an alternative to traditional validation by test onlymentality. This method could be extended to other disciplines and has potential to provide uncertainty for any numericalsimulation, thus lowering the cost of performing these verifications while increasing the confidence in thosepredictions.Spacecraft requirements can include a maximum airflow speed to protect delicate instruments during groundprocessing. Computational Fluid Dynamics can be used to verify these requirements; however, the model must bevalidated by test data. This research includes the following three objectives and methods. Objective one is develop,model, and perform a Computational Fluid Dynamics analysis of three (3) generic, non-proprietary, environmental controlsystems and spacecraft configurations. Several commercially available and open source solvers have the capability tomodel the turbulent, highly three-dimensional, incompressible flow regime. The proposed method uses FLUENT,STARCCM+, and OPENFOAM. Objective two is to perform an uncertainty analysis of the Computational Fluid Dynamicsmodel using the methodology found in Comprehensive Approach to Verification and Validation of Computational FluidDynamics Simulations. This method requires three separate grids and solutions, which quantify the error bars aroundComputational Fluid Dynamics predictions. The method accounts for all uncertainty terms from both numerical and inputvariables. Objective three is to compile a table of uncertainty parameters that could be used to estimate the error in aComputational Fluid Dynamics model of the Environmental Control System spacecraft system.Previous studies havelooked at the uncertainty in a Computational Fluid Dynamics model for a single output variable at a single point, forexample the re-attachment length of a backward facing step. For the flow regime being analyzed (turbulent,three-dimensional, incompressible), the error at a single point can propagate into the solution both via flow physics andnumerical methods. Calculating the uncertainty in using Computational Fluid Dynamics to accurately predict airflowspeeds around encapsulated spacecraft in is imperative to the success of future missions.

[发布日期] 2014-03-28

[学科分类] 力学，机械学