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