The primary objective of this collaborative study is to develop petascale tools applicable to multi-body, fluid-structure interactions in laminar and turbulent flows. Numerical simulations of fluid flows interacting with dynamically, complex-shaped, moving boundaries are among the most challenging problems in computational mechanics. We directly target applications in dense suspensions of deformable particles, such as whole-blood simulations from first principles. We also make available to the broader computational mechanics community an open source fluid-structure interaction, petascale solver. This enables research on unexplored problems in complex suspensions of rigid and/or deformable particles that are ubiquitous in biosystems. The results of the blood flow simulations, for example, will enable the development of better hemolysis and thrombosis models in the short term and therefore blood-compatible cardiovascular devices in the long term. This can have significant impact on healthcare.