05. Micro- and Nano-Scale Transport, MEMS

A channel with an inner diameter of 1 mm or less is called a microchannel, which is used in various devices. Therefore, it is required to elucidate characteristics in the microchannel of flow. One of such devices is a micro chemical reactor. A non-Newtonian fluid is sometimes used as the liquid in the reactor. In addition, singularities such as flow area expansion parts are utilized to promote chemical reaction, and it is important to understand the characteristics of flow through these parts from an engineering point of view. In addition, few papers have investigated turbulent flow characteristics in microchannels, since the flow in microchannels is often laminar. However, an understanding of the turbulent characteristics in the microchannels, which exhibit different features from those of normal sized channels, is of academic importance. Therefore, in this study, we investigated the effect of non-Newtonian fluid on the characteristics flow in a microchannel with a sudden expansion part. Water and glycerin solutions were used as Newtonian fluids, and polyacrylamide (PAM) aqueous solutions was used as non-Newtonian fluid. Here, the PAM aqueous solution is known as a viscoelastic fluid that has both solid and liquid properties. Each aqueous solution was flown through a sudden expansion part in the rectangular microchannel (0.5 by 0.5 mm^2 for upstream side of the expansion and 0.5 by 2.0 mm^2 for downstream side), and the pressure distribution upstream and downstream of the expansion was measured. Then, the expansion loss coefficient was obtained from the pressure measured. As a result, a clear difference in the tendency of the expansion loss coefficient against the Reynolds number was confirmed between the viscoelastic fluid and the non-viscoelastic fluid. The difference might be due to change in the size of the vortex generated in the expansion part, depending on the degree of viscoelasticity having PAM.