Fundamentals of fluid dynamics in microchannels
Utilizing Microfluidics in the Food Industry: Applications and Techniques, Elsevier, ss.23-48, 2024
- Yayın Türü: Kitapta Bölüm / Araştırma Kitabı
- Basım Tarihi: 2024
- Doi Numarası: 10.1016/b978-0-443-13453-1.00002-4
- Yayınevi: Elsevier
- Sayfa Sayıları: ss.23-48
- Anahtar Kelimeler: Fluid dynamics, fluid mechanics, fluidics, microchannels, microfluidic flow
- Yıldız Teknik Üniversitesi Adresli: Evet
Özet
Fluid dynamics is a branch of physics that studies the flow of fluids. In real-life applications, the scale of the flow problem varies significantly and can be as large as nebulae or as small as a flow in a microchannel. The characteristic size of the system is the main property that fixes the dominating forces, which lead the physics and is definitely the starting point in the design and engineering analysis of a system. Microchannels with a diameter of a few micrometers or even nanometers have a distinctive feature of fluid dynamics. Studying fluid dynamics on such a small scale presents both new challenges and exciting new directions for investigation. The term “microfluidic flow” describes the motion of fluids in small spaces, such as microchannels or other microscale devices and systems. The microfluidic flow of Newtonian fluids is characterized by a variety of features, such as low Reynolds numbers “(Re),” laminar flow regimes, and the inevitable dominating effect of surface tension. Liquids in the food industry might behave differently in microchannels depending on both their highly nonlinear characteristics and the microchannel environment. In general, the rheological properties of the common food liquids show non-Newtonian behaviors and can be classified as generalized Newtonian liquids with shear thinning and shear thickening behaviors or viscoelastic liquids, where the stresses are no longer a sole function of the rate of deformation of the flow field. The shear rate-dependent viscosity is the main characteristic of non-Newtonian fluids, and this certainly necessitates unique design considerations for microfluidic devices used in food processing and detailed analysis since it might impact the flow velocity and mixing of the liquid in microchannels. The dimensionless group describes the flow time such as the Weissenberg number, and Deborah number becomes important to characterize the flow addition to the modified Re number for the viscoelastic flow field. The nonlinear characteristics such as first and second normal stress differences, extensional characteristics, and viscous heating of the food liquid need to be addressed properly during the processing which has been investigated for larger scales for decades but needs further understanding on the micro level scale. This chapter is dedicated to addressing the fundamental mechanisms of fluid dynamics involving the microchannels. The characteristics of microfluidic flow, behaviors of food liquids in microchannels, different phases of fluid flow, the effect of friction factor, pressure drop across the flow passage, and fundamental differences involved in microscale fluid flow will be described in detail.