Papers by Keyword: Herschel-Bulkley Fluid

Abstract: Antiplatelet drugs block the formation of blood clots by preventing the clumping of platelets inside arteries, particularly in individuals who have atherosclerosis of their arteries, or are otherwise prone to develop blood clots in their arteries. Atherosclerosis is a slow disease in which arteries become clogged and hardened. Fat, cholesterol, calcium, and other substances form plaque, which builds up in arteries. Hard plaque narrows the passage that blood flows through. That causes arteries to become hard and inflexible. Soft plaque is more likely to break free from the artery wall and cause a blood clot, which can block blood flow to vital organs. In this paper an attempt has been made to investigate the effects of antiplatelet drugs on blood flow and significance of non-Newtonian viscosity through a stenosed artery using Herschel-Bulkely fluid model. Numerical illustration presented at the end of the paper provides the results for the resistance to flow, apparent viscosity and the wall shear stress through their graphical representations.

Abstract: When SSM material is subjected to a sudden transient the rate of buildup (aging) is negligible compared to the rate of breakdown (shear rejuvenation). While this is generally true, due to prolonged processing or the geometry the local shear rate in some regions may become equal or lower than the critical value, where aging becomes as important as shear rejuvenation. In this work we simulate in detail shear rejuvenation and aging in semisolid slurries. Using a standard thixotropic model used widely for modeling SSM suspensions but a novel computational method we reveal and confirm numerically for the first time shear banding. The phenomenon is found to be time dependent where the material first yields fully and then, after a certain time the yielded front retreats to form two distinct bands -one yielded and one unyielded. This phenomenon must be accounted for in the evaluation of the material constants since the time scale of the process is similar to the time scale of the phenomenon.

Abstract: Due to the distinct rheology of semisolid slurries the process has well established advantages over competing near-net-shape manufacturing technologies. Despite the obvious advantages of the process its adoption by the casting industry, however, has been slow. This is primarily due to lack of confidence of how these slurries flow in die cavities. The added cost associated with the specially prepared slurry has also affected the process commercial success. Nevertheless despite these problems attention to the semi-solid metal process has indeed increased over the years. The main focus of this review is the modeling of semisolid slurries. The objective here is to present an overview of relevant aspects of modeling by focusing on the physics of the slurry and by stressing consistent mathematical and analysis methods to determine the material constants.