1. A system for determining cardiovascular information for a patient, the system comprising: at least one computer system configured to: receive patient-specific data regarding a geometry of an anatomical structure of the patient; create, based on the patient-specific data, a three-dimensional model representing at least a portion of the aorta of the patient and at least a portion of a plurality of vessels emanating from the portion of the aorta, the three-dimensional model including portions representing at least one inlet and a plurality of outlets for blood flow; create a three-dimensional mesh based on the three-dimensional model; create at least one boundary condition model having less than three dimensions, the at least one boundary condition model representing blood flow through at least one of the at least one inlet or the plurality of outlets; determine a blood flow characteristic within the anatomical structure of the patient by solving equations governing blood flow using the three-dimensional mesh and the at least one boundary condition model; and automatically tune at least one parameter of the three-dimensional model or the at least one boundary condition model.