Applying a Cartesian method to moving boundaries

The paper describes the development of a Cartesian method able of simulating compressible and viscous flows around moving/deforming objects as well as fluid-structure interactions (FSI). Besides, the research addresses the issues related to the partitioned coupling of aerodynamic and structural tools and suggests the use of proper drivers based on open-source libraries.The flow solver is based on dynamic immersed boundaries (IB) which take into account the motion of Lagrangian bodies through an inertial Cartesian mesh. This means having cells without volume changes and/or roto-translations. In particular, the major difficulties arise from the correct evaluation of flow quantities at cells emerging from the solid areas. Indeed, no flow-state is associated with cells inside the body. As a consequence, a 'field-extension' procedure is applied to estimate the flow state vector where needed. The use of fluid and wall values makes the procedure consistent. A proper IB model accounts for the body motion into a stationary mesh that are dynamically adapted to the flow. Both rigid and deforming motions are allowed by means of proper BCs based on the local wall-velocities.The paper discusses the accuracy and stability constraints of the method when applied to well-known benchmarks available in literature. In particular, the ability to analyze rigid body-motions is assessed by simulating the viscous flows around an oscillating circular cylinder and a moving sphere. Both cases focus on the laminar regime which represents an effective starting-point for validating the dynamic IB-method.Part of the research activities is devoted to developing an interface for coupling the present method with a structural solver in the framework of a partitioned process. A shared platform is set-up for driving the solution sequence and analyzing the accuracy of the results. A literature case is discussed which consists of a flexible cantilever mounted in the laminar wake of a rigid square cylinder.The final aim is to make affordable the study of complex flows whose characteristics strongly depend on the structural dynamics of immersed objects. In particular, the use of an IB method based on a fast and automatic meshing process is expected to simplify and speed-up the simulation of fluid-structure interaction (FSI) problems.