Research Software Engineering Support For The Simvascular Open-Source Project - Patient specific simulations of blood flow and tissue biomechanics have become a crucial component of fundamental research in treatment planning, medical device design, and mechanisms of disease progression in cardiovascular (CV) disease. SimVascular is the only fully open-source software package providing state-of-the-art image-based blood flow modeling and analysis capability to the CV biomechanics community. Over the past several years, our team established SimVascular as a vibrant open-source project, attracting over 10,000 new users worldwide, and facilitating high-impact research and >1000 publications. Recent advances in SimVascular include the addition of new multi-physics solver capabilities for large deformation fluid structure interaction (FSI), electrophysiology and cardiac mechanics, reduced order models, and machine learning (ML) methods for image segmentation. The proposed project would support Dr. David Parker, a research software engineer (RSE) in the Marsden lab at Stanford who leads software development for SimVascular. During the three-year funding period, Dr. Parker will make essential contributions to 1) code improvements, development, and integration of new features, 2) improved architecture for sustainability and modularity, and 3) dissemination and user community support. Dr. Parker is supporting three R01-funded projects (Marsden PI) which all rely on SimVascular as an essential software resource. These high-impact projects span adult to pediatric cardiovascular disease and will produce new computational methods for fluid solid growth simulations, digital twins of pulmonary hemodynamics, and multiphysics cardiac simulations for surgical planning. Importantly, in support of this NIH funded research, Dr. Parker will ensure that software developed by trainees is hardened (e.g. standard data structures), integrated, tested (e.g. GitHub actions), documented (e.g. Doxygen) and publicly released as part of SimVascular (e.g. code reviews before merging). Without Dr. Parker serving in this essential role, it would be extremely difficult to make these advancements publicly available to the research community while adhering to best software practices and ensuring usability. Bringing experience from the software engineering industry, Dr. Parker is instrumental in supporting trainees by teaching software standards, agile development, good coding practices, debugging methods, and testing strategies. Dr. Parker intends to remain a career RSE dedicated to the SimVascular community. He intends to apply for follow up funding from private foundations. Career goals include growth of the SimVascular user community, increased use by medical device startup companies, and deployment in a clinical service at Lucile Packard Children’s Hospital at Stanford.