Numerical investigation of transient mixed convection of nanofluid in a cavity with non-Darcy porous inner block and rotating cylinders with harmonic motion.

Mixed convection of nanofluid in a 2D square enclosure with a porous block in its center and four rotating cylinders, which are forced by a simple harmonic function, was studied numerically. The porous zone was studied by considering the Forchheimer-Brinkman-extended Darcy model. Effects of various parameters including Darcy number (10-5 ≤ Da ≤ 10-2), porosity (0.2 ≤ ɛ ≤ 0.7), Richardson number (0.1 ≤ Ri ≤ 10), and volume fraction of nanoparticles (0 ≤ ϕ ≤ 0.03), on heat transfer, entropy generation, PEC, velocity, streamline and isotherm contours were demonstrated. The results show that decreasing the Darcy number as well as reducing the Richardson number leads to an increase in the average Nusselt number. However, porosity changes had no decisive effect on heat transfer. Maximize the volume fraction of copper nanoparticles in the base fluid enhanced heat transfer. In the case of the high permeability of the porous medium, the impact of the harmonic rotation of the cylinders on the flow patterns became more pronounced.

Blood flow analysis inside different arteries using non-Newtonian Sisko model for application in biomedical engineering.

BACKGROUND AND OBJECTIVE: In the present research, simulation of blood flow is carried out inside the artery with different radiuses of 0.002 m, 0.0025 m, 0.003 m, and 0.0035 m. METHODS: To simulate the blood as non-Newtonian fluid using of Sisko model, different constant heat fluxes are applied on the boundary walls of the artery. Then, the results of velocity, temperature, and Nusselt number are reported versus axial and radial directions. RESULTS: Results show that blood temperature is enhanced with increasing axial distance. Also, maximum temperatures are seen at maximum axial and radial distances from references of entry and central regions of artery. Furthermore, increasing the radius of the artery can increase blood temperature due to a reduction in blood velocity inside the vessel. Consequently, blood particles can spend more time to receive thermal energy, which leads to emerging higher blood temperature. This phenomenon can be important in the oxygenation process inside the human body. It is observed that effect of increasing the radius of the artery can enhance blood temperature as much as 0.001 K. Also, applying constant heat fluxes in order 4 W/m2 to 5 W/m2 and 6 W/m2 on the artery wall brings axial Nusselt values of 0.365-0.4575 and 0.55, respectively. As a result of axial and radial Nusselt numbers, it is reported that because radial Nusslet is unchanged in the central region of the artery, temperature shall be constant in a radius less of 0.0019 m. Therefore, the influences of heat fluxes are ignorable in the central region of the vein. Also, maximum temperatures are reported as much as 310.5 K, 311.1 K, and 311.5 K in order of applying thermal boundary flux of q'' = 400 W/m2, q'' = 800 W/m2 and q'' = 1000 W/m2 respectively. Therefore, applying heat fluxes in the range of investigated can raise the blood temperature as much as 1.5 °C, which is equal to 38.5 °C. Thus, there is no doubt that such a high temperature is dangerous for human health. CONCLUSIONS: As conclusion, the results of this research are important hints for medical diagnostics of oxygenation, hematocrit, polycythemia, and blood disorders.

Numerical simulation of blood flow inside an artery under applying constant heat flux using Newtonian and non-Newtonian approaches for biomedical engineering.

BACKGROUND AND OBJECTIVE: In this paper, different behaviors of blood flow are simulated inside the artery under applying a constant heat flux on the artery boundary walls. METHODS: To simulate the blood flow, the Sisko model is employed. Then, the temperature and Nusselt number of blood flow are reported for different Sisko parameters. Afterward, the effects of different artery radiuses are studied on the Nusselt number. RESULTS: Medical treatment by replenishes fluid and electrolytes in the body vessels can change blood flow properties from non-Newtonian behavior to Newtonian behavior, which increases heat transfer in blood flow and causes to reduce blood flow temperature. In this research, the maximum temperature of Newtonian blood fluid flow is reported as much as 310.0045 K, whereas; maximum flow temperature in non-Newtonian blood fluid is 310.007 K. These results emphasize the effects of the type of Newtonian and non-Newtonian fluid model on the thermal behavior of blood inside body vessels. Since medical science does not permit body temperature to be changed from the normal condition, this small variation can be noticeable and sensible on the health. Hence, medical scientific research centers and institutes of vaccine and serum have to be careful in the mechanical design of drugs for blood fluid. CONCLUSIONS: The results of this research show the application of mechanical engineering for some of the medical concerns in designing the drugs which are effective on the behavior of human body blood.