A segregated reduced order model of a pressure-based solver for turbulent compressible flows

This article provides a reduced order modelling framework for turbulent compressible flows discretized by the use of finite volume approaches. The basic idea behind this work is the construction of reduced order models capable of providing fully consistent solutions with respect to the high fidelity flow fields. Full order solutions are often obtained through the use of segregated solvers, employing slightly modified conservation laws so that they can be decoupled and then solved one at a time. Classical reduction architectures, on the contrary, rely on the Galerkin projection of a complete Navier-Stokes system to be projected all at once, causing a mild discrepancy with the high order solutions. In this article we rely on segregated reduced order algorithms for the resolution of turbulent and compressible flows in the context of physical and geometrical parameters. At the full order level turbulence is modeled using an eddy viscosity approach. Since there are a variety of different turbulence models for the approximation of this supplementary viscosity, one of the aims of this work is to provide reduced order models which are independent on this selection. This goal is reached by the application of hybrid methods where Navier-Stokes equations are projected in a standard way while the viscosity field is approximated by the use of data-driven interpolation methods or by the evaluation of a properly trained neural network. By exploiting the aforementioned expedients it is possible to reduced the computational cost associated wit fluid flow problems characterized by high Reynolds numbers and elevated Mach numbers.