Investigation and numerical analysis of laminar flow of casson fluid around a circular cylinder

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Investigation and numerical analysis of laminar flow of casson fluid around a circular cylinder

ارائه دهنده: Provider: Hamed edalat khah

اساتید راهنما: Supervisors: Dr.Mohammad Saeed Aghighi

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr.fazl allah eskandari manjili , Dr amireh noorbakhsh

زمان و تاریخ ارائه: Time and date of presentation: 2022/09/11

مکان ارائه: Place of presentation: Engineering Faculty

چکیده: Abstract: In this research, the flow and forced heat transfer of Casson model viscoplastic fluid around a circular cylinder has been numerically investigated. Fluid passing around the cylinder is one of the most common problems in fluid mechanics and is used in various industries such as heat exchangers. Also, casson fluid is used in many industries, including oil and food products. The governing partial differential equations include continuity, momentum and energy equations, and then they were written as dimensionless equations and on a wide range of relevant dimensionless parameters, including Reynolds number (Re=5,10,20,40) and Bingham number (0 ≤Bn≤ Bnmax) for a circular cylinder, have been solved using the finite element method based on coding in MATLAB environment. The results show that because there is geometric symmetry and flow, the grid is created in one half of the domain. In the examination of the velocity fields, it is observed that no flow separation occurs on the surface of the cylinder at Re=5, As the Reynolds number increases, the flow separation angle is observed. Also, as the Bingham number increases, the fluid becomes more viscous and the adhesion increases, so the formed vortices become smaller. By increasing the Bingham number, the desired fluid changes from Newtonian fluid to viscoplastic. Because the viscosity of the fluid increases, the drag coefficient also increases. At the beginning of the cylinder, because the cold fluid hits the hot cylinder, then the maximum heat transfer occurs at that point. Heat transfer is the same as local Nuselt number. In the examination of isothermal contours, it can be seen that the maximum point of heat transfer is the point where the cold fluid meets the hot cylindet, , the distances of isothermal lines are very close to each other. The heat transfer decreases with the movement of the fluid on the cylinder and the distance between the isothermal lines increases. The slope of the temperature gradient also decreases . In the investigation of compression drag coefficients, frictional drag coefficients and total drag coefficients in different Reynolds numbers, with the increase of Bingham number, those coefficients also increase, but with the increase of Reynolds number, due to the presence of creep flow on the cylinder, the drag coefficients are reduced.

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