|A Transient Simulation of the Carotid Artery Flow|
|Álvaro De Bortoli - Federal University of Rio Grande do Sul|
Rudnei Da Cunha - Federal University of Rio Grande do Sul
Diseases such as atherosclerosis, which appear due to area reduction or recirculation of the flow into an artery, have a process which is not uniform. Lesions appear meanly at sinus of the internal carotid artery, a region where velocity tends to reduce and fat deposition can occur, and can originate some kind of cerebrum problems, infart and can kill mostly adults. Many hypothesis relate hemodynamic loads with the location of atherosclerosis lesions. They are usually based on the influence of tension in the walls of an artery, and its relation to the flow intensity and characteristics. In this way, a local velocity distribution takes a very important role to analyze the surgement and dangers of this disease. There are non-invasive techniques based on ultrasound that help us to detect atherosclerosis lesions in their initial stage. However, they are not perfect and a numerical study of this complex flow can be used to better understand this phenomenon and to find or construct better equipment for its detection. Many characteristics, including rheological properties, distensibility, geometry and frequency of heart pulsation are important to model the blood flow through the arteries. It is a not so easy task to model an artery because its geometry varies between individuals and its walls are anisotropic and viscoelastic. However, it is a good approximation to consider the flow to be fully developed few diameters before the carotid bifurcation and that its geometry remains almost the same. This work shows some numerical simulations of the transient flow over a square step and through the carotid artery bifurcation. The model considers the flow for low levels of deformation rates, incompressible, bidimensional and for rigid walls. The numerical method is based on the finite differences explicit Runge-Kutta three-stage scheme with central spatial discretization and is second order time-accurate. Obviously, the most executed sections of the code are those related to computing the velocities and pressure. Care has been exercised to ensure that the code runs as fast as possible; we have also minimized the number of arrays used and organized the computation to reduce data traffic to and from the memory. Numerical tests are carried out for the flow over a square step in the duct and the carotid region, for Reynolds numbers ranging from 100 and 500 and the results are found to compare well with numerical/experimental data available in the literature.