Konu "nanopartiküller" ile LEE- Isı Akışkan Lisansüstü Programı- Yüksek Lisans'a göz atma
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ÖgeNumerical investigation of inertial focusing of micro andnanoparticles in curvilinear microchannels(Graduate School, 2022-01-21) Aldemir, Ahmet Turan ; Çadırcı, Sertaç ; 503181126 ; Heat FluidRecently, microfluidic systems have been preferred more than conventional methods due to their ease of production, economic advantages, high precision processing capabilities and ease of operation. These systems are in a situation where many disciplines such as physics, chemistry and engineering are intertwined. Microfluidic systems aim to provide manipulation of fluids moving in microchannels and to control the flow field. With the provision of this control, important developments are experienced in fields such as biomedical engineering and medicine. As an important area, there have been serious improvements in the separation of particles of different diameters in microfluidic systems recently. In the studies carried out, particles of different diameters are sent into the microchannel through from source (like a pump) and can be collected in separate beams from the channel exit. This has become an important step in the early diagnosis of deadly diseases such as cancer. The concept of separating particles of different diameters from each other in the microfluidic systems has accelerated with the developments in Lab on a Chip (LoC) and MEMS systems. Many different mechanisms have been developed for the separation of particles. Separation of particles in the microfluidic systems can be achieved either by active separation techniques, where external forces act, or passive separation techniques, where an external force is not used. In active separation, many different sources such as electrical systems, sound, optics can be used to create an external force. On the other hand, passive separation techniques use dynamics within the microchannel to separate particles. Inertial focusing, which is an important area in passive focusing, still continues to develop. The logic of inertial focusing is that forces acting on a particle moving in a fluid, either from flow, from interaction with the walls of the microchannel, or from effects at the molecular level. The most important of these forces is the lift force, which directs the particle to a certain equilibrium position. Lift force is divided into two as wall interacting lift force and shear stress lift force. The most important difference of these forces emerges when determining the equilibrium position of the particles. The lift force arising from the wall interaction pushes the particles towards the center, while the shear stress lift force directs the particles from the center towards the walls. As a result, when these forces reach equilibrium, the equilibrium position of the particle is determined. The magnitude of these forces is highly dependent on the particle diameter, so they cause the particles with different diameters to line up in different equilibrium positions, thus allowing the particles to be separated from each other. In inertial focusing, the addition of curvature to the microchannels adds a secondary effect to the flow. This phenomenon is due to the formation of eddies in the curved regions within the channel. This flow effect also causes a force called the Dean force to be added to the particles. In the studies carried out, it was observed that the focusing mechanisms of the particles improved thanks to this effect. Microchannel geometry is an important parameter that affects the mentioned forces. By changing the geometry and dimensions, it is possible to design a particle separation mechanisms that works with higher efficiency. In this context, different microchannel designs such as straight microchannel, spiral microchannel, serpentine microchannel have been studied, and detailed studies have been carried out on these effects. Studies in the field of separation of microparticles are mostly carried out using synthetic particles in order to better understand how blood and cancer cells interact with each other. Particle separation is affected by many different parameters such as flow rate, type of fluid used, particle diameter, as well as microchannel geometry. Therefore, it is very important to best understand the physics of inertial focusing in order to design the most efficient decomposition. In this study, the concept of inertial focusing is examined. Computational Fluid Dynamics (CFD) analyzes were performed on microchannels with different geometries, parametric analyzes affecting focusing were completed and the effects were examined. Within the scope of the study, flow and particle analyzes of the sunflower geometry obtained by adding serpentine regions to a conventional spiral microchannel geometry and the importance of this geometry were discussed.