Immersed Boundary Method for CFD Analysis of Moving Boundary Problems in OpenFOAM

CFD simulation of hydraulic equipments involving moving boundary components is really challenging due to difficulty in maintaining a good quality mesh essential for obtaining accurate numerical solutions. To deal with these problems, commercial codes such as Ansys CFX provide the option of mesh morphing which must be used in conjunction with pre-defined multiple grid configurations to account for changing flow domain. In contrast to this approach, immersed boundary method (IBM) provides an attractive alternative in which the complex moving surface is immersed in a fixed Cartesian (or polyhedral) grid. We have developed an immersed boundary simulation tool-kit for moving boundary problems based on OpenFOAM. It requires the user to provide the definition of the immersed surfaces in STL (stereolithography) format, type of flow (internal/external) and motion (stationary, pre-defined or flow-induced) of the surface. Numerical simulations have been performed for selected test cases to assess the computational performance of the immersed boundary too-kit. Numerical results of flow over stationary as well as vibrating cylinders agree very well with available experimental and numerical results, and show that the immersed boundary simulations accurately capture the vortex shedding frequency and vortical structures for moving boundary problems.