1. A method for assessment of renal artery stenosis, comprising: generating a patient-specific anatomical model of at least a portion of the renal arteries and aorta from medical image data of a patient; estimating patient-specific boundary conditions of a computational model of blood flow in the portion of the renal arteries and aorta based on the patient-specific anatomical model; simulating blood flow and pressure in the portion of the renal arteries and aorta using the computational model based on the patient-specific boundary conditions; and calculating at least one hemodynamic quantity characterizing functional severity of a renal stenosis region based on the simulated blood flow and pressure in the portion of the renal arteries and aorta.