Quantification of Uncertainties in Compressible Flows with Complex Thermodynamic Behavior

Abstract

A Tensorial-expanded Chaos Collocation method is used to quantify the effect of uncertainties on thermophysical properties of compl ex organic substances on the computed flow properties. Specifically, we investigate the e ffect of uncertainties introduced by several thermodynamic models on the numerical results provided by a computational fluid dynamics code for flows of molecularly complex gases close to saturation condition (dense gas flows). Most thermodynamic models of current use actually require data about thermophysical properties of the fluid, such as cri tical-point properties, which are typically affected by large uncertainties. Moreover, more acc urate thermodynamic models typically require a larger number of input parameters, thus i ntroducing new sources of uncertainty. The Tensorial-Expanded Chaos Collocation method investigated in this paper is used to perform both a priori and a posteriori tests on the output data generated by three popula r thermodynamic models for dense gases with uncertain thermophysical input parameters. A priori tests check the sensitivity of each equation of st ate to uncertain input data via some reference thermodynamic outputs, such as the saturation curve and the critical isotherm. A posteriori tests investigate uncertainties introduced in the pressure field around an airfoil placed into a transonic dense gas stream.