Development of an Effective Implicit Solver for General-Purpose Unstructured CFD Software

In this paper, we report the development of an effective implicit finite-volume solver for general-purpose turbulent flow computations on unstructured hybrid mesh system. For the inviscid and viscous fluxes, we employ the Rotated-Roe-HLL and alpha-damping fluxes, respectively. The implicit solver is constructed by a defect correction method, where the residual Jacobian is constructed based on a low-order compact scheme. It enables efficient time-dependent computations by an unconditionally-stable implicit time-integration scheme. Numerical results show that a significant speed-up is achieved over an explicit pseudo-time stepping scheme and the exact first-order inviscid Jacobian gives superior iterative convergence over a simplified inviscid Jacobian for both steady-state and transient analyses.