Cardiovascular diseases were the main cause for loosing lives in the last decades due to the restricted blood flow states in the blood vessels areas. Numerical investigations have been conducted as the aim of this work to examine the blood flow, and wall shear stresses adjacent to the mono stenosis up to different degrees involved in the main, side and distal main branches as well as observe the pulsatile flow of blood in the left coronary artery through various percentage of stenosis. Both the Carreau non-Newtonian rheological model and the Newtonian model were utilized to model the blood fluid and wall shear stresses of left coronary artery, in a row, all the calculated data were validated with the previously published papers. It was found that the blood flow inside areas of the artery lie within the range of non-Newtonian rheological effects can be present, verifying the need to treat blood as non-Newtonian fluid; especially, with the case of 90% blockage.
Computational fluid dynamics is a computer simulation technique used to study the effects of stenosis and aneurysm degree on haemodynamics in the blood vessels such as blood velocity, pressure, and wall shear stress. The current study employed the numerical simulations of pulsed blood flow using the Carreau non-Newtonian rheological and Newtonian models to model the wall shear stresses and haemodynamics in blood vessels. Furthermore, the model included three stenosis areas with different diameters, 70%, 80%, and 90%, and two aneurysm areas with different diameters, 15% and 44%. The study observed the blood velocity, pressure, and wall shear stresses at the damaged blood vessels areas. It was found that the maximum velocity was observed from stenosis when the stenosis ratio was increased to 90%. Additionally, the velocity increased up to 3.4 times, which led to increased blood shear stresses to up to 8.4 times, when the start acceleration flow and peck flow were compared. It is known that the degree of damage on blood vessels produces the most significant influence on local blood pressure and shear stresses. Therefore, it was concluded that stenosis at 90% may probably lead to serious lesions and effectively block the bloodstream by the ensuing thrombus.
Thermal systems more efficient by emanating from industrial applications and space program galvanized interest in ways by increasing heat transfer is the system. The main aim of this paper is to investigate experimentally the effects of the vertical vibration and force convection on the average Nusselt number in a longitudinal finned tube. The finned tube was located inclined or horizontally in different angles of 0°, 30° and 45°. The effect of the excitation frequency covers below 16 Hz with various heat fluxes ranged from 500-1500 W/m2. It was noticed that the good agreement between the experimental measurement and the previous experimental studies with deviation of 5%. The results showed that average Nusselt number values at angle 45° from longitudinal finned tube were higher by up to 14%, 16% compared with the angles 30°, and 0°, respectively. Furthermore, it can be summarized that the vertical vibration significantly affects to the average Nusselt number from longitudinal finned tube cylinder and the influence on the heat transfer coefficient for this system should be considered.
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