Cardiopulmonary bypass (CPB) is a common procedure carried out to provide a fluid free and motionless work field at the time of cardiac surgical procedures. To achieve CPB, cannulation of the aorta i.e., insertion of the aortic cannula into the aorta to complete the extracorporeal blood flow circuit, is essential. The flow patterns of blood during CPB are very different from physiological flow and as blood from the heart lung machine enters the aorta, which is never fully evacuated, these flow patterns are of particular importance. This work focusses on the flow patterns of the blood as it enters the aorta post placement of the cross clamp. The investigation showed the high velocity impingement of blood on the aortic wall resulting in the «Sandblasting» effect. High fluid shear rates are also seen in regions of the flow field. It also showed the recirculation patterns and the formation of eddies as well as the splashing of blood within the aorta, originating at the point of impingement. Retrograde flow was also observed during the initial few seconds of the procedure.