A Comparative Study of Structured and Cut-Cell Grids Applied to an Oil-Injected Screw Compressor

Abstract Discretized Partial Differential Equations (PDEs) for numerical modeling of fluid mechanics systems require the use of various iterative linear solvers. In this study, two different CFD solvers, Ansys CFX and Converge, were employed to develop a transient 3D CFD model of an oil-injected screw compressor. Each solver utilized distinct meshing techniques—Ansys with a structured grid and Converge with a cut-cell grid. The numerical models have been validated utilizing experimental measurements. Presence of turbulent boundary layer and shear flow topology in the rotating fluid domains required implementing k-ω Shear Stress Transport (SST) turbulence model along with the physics needed to capture multifluid interfaces. In CONVERGE CFD, Semi Implicit Pressure Linked Equation (SIMPLE) algorithm was used for initial model development and pressure-velocity coupling in a collocated grid model, eliminating checkerboard numerical oscillations with the Rhie-Chow interpolation scheme. Ansys CFX handles pressure-velocity interactions through its solver framework, which operates without requiring a separately defined pressure-velocity coupling algorithm. These model parameters and pressure velocity coupling algorithms are kept unchanged while comparing preconditioned Successive Over Relaxation (SOR) and Incomplete Lower and Upper triangular (ILU) decomposition. These two solvers yielded to different numerical instabilities and rate of convergence, affecting the simulation clock time.