Effects of Gas Area Fraction on Developing Flow of Shear Thickening Fluids in Circular Tube having Superhydrophobic Transverse Grooves
Keywords:water repellent, non-Newtonian, surface roughness, air cavity, power-law index
Superhydrophobic surface is extensively used in lab-on-a-chip technology, thermal management, self-cleaning and condensation arising from its ability to reduce fluid flow resistance. There are many existing studies conducted on fluid flow in channels and tubes having superhydrophobic surface, especially focusing on Newtonian fluid in fully-developed flow region. Before a fully-developed flow profile is attained, fluid flow undergoes a developing velocity profile region where velocity flow profile continuously develops axially. However, limited studies are focused on flow developing region, especially non-Newtonian flow in the presence of superhydrophobic surface. In this study, the effects of gas area fraction on hydrodynamic entrance region of shear thickening fluids in a circular tube with alternating superhydrophobic grooves and ribs arranged in the transverse direction are investigated. Superhydrophobic transverse grooves of normalized groove-rib periodic spacing ???? = 0.1 with different gas area fractions ???? are considered in this study with the assumption of laminar, steady and incompressible flow in the tube. The influence of the superhydrophobic surface on the velocity field, centerline velocity distribution and hydrodynamic entrance length are examined. From the numerical results, for Reynold number, ???????? of 1 × 10?4 and power-law index, ???? ranging from 1.0 to 1.5, the hydrodynamic entrance length is found to be consistently longer, in the presence of superhydrophobic surface. For microfluidic applications, this implies that for shear thickening flow through tube patterned with these regular microstructures of hydrophobic condition, flow developing region can be altered.