Quantification of uncertainties in compressible flows with complex thermodynamic behavior

A Tensorial-expanded Chaos Collocation method is used to quantify the effect of uncertainties on thermophysical properties of complex organic substances on the computed flow properties. Specifically, we investigate the effect 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 critical-point properties, which are typically affected by large uncertainties. Moreover, more accurate thermodynamic models typically require a larger number of input parameters, thus introducing 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 popular thermodynamic models for dense gases with uncertain thermophysical input parameters. A priori tests check the sensitivity of each equation of state 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.