Subcommittee on Biorheology: Dimensional analysis and scaling relevant to flow models of thrombus formation Flow chambers are increasingly used to model thrombus formation in (patho)physiologically inspired geometries and conditions. The flexible design enabled by microfluidics and the variety of commercially available devices makes comparisons between flow chambers challenging. There is also a need to make faithful comparisons between these in vitro models and animal models. Dimensional analysis and scaling provides a rigorous method for making these comparisons. Scaling is a mathematical tool used to simplify, characterize, and design systems based on their dimensions and dynamics. Scaling arguments have recently appeared in hematology journals for describing biophysical mechanisms that regulate thrombus growth. In practice, scaling involves selecting important dimensional and dynamic parameters and forming dimensionless groups that characterize a system. These dimensionless groups determine the relative importance of geometric features, forces, and rates. The purpose of this Communication is to provide a primer on scaling and provide recommendations for reporting and calculating relevant dimensionless groups in flow models of thrombus formation.Read more.