Systems and methods for evaluating blood behavior when flowing through an implantable medical device are provided. A flow loop includes the implantable medical device, and a blood reservoir configured to contain a volume of blood and to supply blood from the volume of blood to the implantable medical device. The flow loop further includes a plurality of tubing sections coupled in flow communication between the implantable medical device and the blood reservoir, the plurality of tubing sections including a least a first tubing section having a first diameter and a second tubing section having a second diameter, wherein the second diameter is smaller than the first diameter, and a flow diverter coupled in flow communication between the plurality of tubing sections and the blood reservoir, the flow diverter comprising an outlet that is configured to be positioned below a surface of the volume of blood.
