Collaborative Research: SI2-SSI: Scalable Infrastructure for Enabling Multiscale and Multiphysics Applications in Fluid Dynamics, Solid Mechanics, and Fluid-Structure Interaction

Overview: From the writhing and coiling of DNA, to the beating and pumping motions of cilia and flagella, to the flow of blood in the body, to the locomotion of fish, insects, and birds, coupled fluid-structure systems are ubiquitous in biology. The immersed boundary (IB) method is a broadly applicable framework for modeling and simulating these systems. This framework was introduced to describe the fluid dynamics of heart valves, and subsequent development initially focused on modeling cardiac fluid dynamics. However, this methodology has also been applied to a wide variety of problems in which a fluid flow interacts with immersed structures, including elastic bodies, bodies with known or prescribed deformational kinematics and rigid structures. Extensions of the IB method have also been specifically developed to model electrophysiological systems and reaction-advection-diffusion systems involving chemically active structures. Although the IB method is a broadly useful approach to biofluid mechanics and fluid-structure interaction (FSI), high spatial resolution can be required to resolve viscous boundary layers at fluid-structure interfaces and to resolve flow features shed from such interfaces. To improve the efficiency of the IB method, the PI has developed adaptive versions of the IB method that employ block-structured adaptive mesh refinement (AMR) to deploy high spatial resolution only where it is needed, such as in the vicinity of fluid-structure interfaces, or near localized regions of high vorticity in the flow field. These methods have been implemented within the IBAMR software, which is a distributed-memory parallel implementation of the IB method and its extensions that leverages high-quality open-source computational libraries including SAMRAI, PETSc, and libMesh. IBAMR has grown from a research code used primarily by the PI to a framework that enables innovative research by a number of independent groups related both to the further development of the IB method and to its application in various fields of science and engineering. This software is being actively used within independent research projects that aim to model different aspects of cardiovascular dynamics, such as platelet aggregation and the fluid dynamics of natural and prosthetic heart valves, as well as within projects that study other problems in biofluid mechanics, including cancer dynamics, insect flight, aquatic locomotion, and the dynamics of phytoplankton. IBAMR is also being applied to non-biological problems, including nanoscale models of colloidal suspensions and models of active particles. The key goals of this project are to further extend the IBAMR software by implementing various modeling and discretization technologies required by the research applications of current and prospective users of this software, by developing improved solver infrastructure facilitated by new support for tight integration of block-structured AMR codes with the PETSc library to be developed in this project, and by developing (in collaboration with Kitware Inc.) high-quality user interface (UI) tools for model development, deployment, and analysis. Successfully executing these aims will ensure that IBAMR is able to meet the needs of its growing user community, and will facilitate the use of IBAMR as an educational tool in a variety of settings. Intellectual Merit: This project will substantially enhance the capabilities of key modeling and simulation software infrastructure used by a number of independent research projects while also developing new numerical meth