BLOOD-FLOW IN ARTERIES

Blood flow in arteries is dominated by unsteady flow phenomena. The ca rdiovascular system is an internal flow loop with multiple branches in which a complex liquid circulates. A nondimensional frequency paramet er, the Womersley number, governs the relationship between the unstead y and viscous forces. Normal arterial flow is laminar with secondary f lows generated at curves and branches. The arteries are living organs that can adapt to and change with the varying hemodynamic conditions. In certain circumstances, unusual hemodynamic conditions create an abn ormal biological response. Velocity profile skewing can create pockets in which the direction of the wall shear stress oscillates. Atheroscl erotic disease tends to be localized in these sites and results in a n arrowing of the artery lumen-a stenosis. The stenosis can cause turbul ence and reduce flow by means of viscous head losses and flow choking. Very high shear stresses near the throat of the stenosis can activate platelets and thereby induce thrombosis, which can totally block bloo d flow to the heart or brain. Detection and quantification of stenosis serve as the basis for surgical intervention. In the future, the stud y of arterial blood flow will lead to the prediction of individual hem odynamic hows in any patient, the development of diagnostic tools to q uantify disease, and the design of devices that mimic or alter blood B ow. This field is rich with challenging problems in fluid mechanics in volving three-dimensional, pulsatile flows at the edge of turbulence. Blood Bow in arteries is dominated by unsteady flow phenomena. The car diovascular system is an internal flow loop with multiple branches in which a complex liquid circulates. A nondimensional frequency paramete r, the Womersley number, governs the relationship between the unsteady and viscous forces. Normal arterial flow is laminar with secondary fl ows generated at curves and branches. The arteries are living organs t hat can adapt to and change with the varying hemodynamic conditions. I n certain circumstances, unusual hemodynamic conditions create an abno rmal biological response. Velocity profile skewing can create pockets in which the direction of the wall shear stress oscillates. Atheroscle rotic disease tends to be localized in these sites and results in a na rrowing of the artery lumen-a stenosis. The stenosis can cause turbule nce and reduce flow by means of viscous head losses and flow choking. Very high shear stresses near the throat of the stenosis can activate platelets and thereby induce thrombosis, which can totally block blood flow to the heart or brain. Detection and quantification of stenosis serve as the basis for surgical intervention. In the future, the study of arterial blood flow will lead to the prediction of individual hemo dynamic hows in any patient, the development of diagnostic tools to qu antify disease, and the design of devices that mimic or alter blood Bo w. This field is rich with challenging problems in fluid mechanics inv olving three-dimensional, pulsatile flows at the edge of turbulence.