Hybrid Compressible-Incompressible Numerical Method for Transient Drop-Gas Flows

A numerical method for drops in which the liquid phase is modeled as an incompressible fluid while the gas phase is modeled as a compressible fluid is presented. An unstructured grid that conforms to the deforming interface at all instants in time is employed. Finite volume discretization of the strong conservative form of the governing equations is solved with an implicit iterative procedure that simultaneously solves governing equations for the two phases and the boundary conditions at the interface. The numerical accuracy of the code is assessed by comparing the computed transient drag of a decelerating solid sphere with prior computed results published in the literature and comparing the computed behavior of an oscillating drop with the classical solution of the problem. The numerical method is assessed in axisymmetric computations of deforming and decelerating liquid drops. The transient drag of the drop is compared with computed results for a solid sphere.