Towards Subgrid-Scale Turbulence Modeling in Dense Gas Flows

Abstract

It is known from the literature that Large Eddy Simulations of dense gas flows can prove very useful in order to better understand the behavior of friction losses in Organic Rankine Cycle turbines and expanders. Yet, no dedicated turbulence closure models exist for such flows. In this study, the authors lay the fondations for the development of turbulence closure models in dense gas flows. The Subgrid-Scale terms are first rigorously derived from the filtered Navier-Stokes equations. Additional terms to the well-known Subgrid-Scale closure terms are identified in the dense gas context. Using Direct Numerical Simulation, the variances of Subgrid-Scale terms in the filtered momentum equations are computed both for the dense and perfect gas cases and significant differences are revealed between the two cases. A model using only filtered fields as input is derived for one of the dense gas specific Subgrid-Scale terms using a Correlation Patterns Modeling approach. Preliminary a priori tests indicate that this approach can be easily implemented and provides promising results.