MHD flow and heat transfer analysis of fractional Oldroyd-B nanofluid between two coaxial cylinders

摘要

In previous study on the flow of fractional viscoelastic fluid between two coaxial cylinders, due to the complexity of computation, researchers commonly assume that the flow area is a rectangular pipe. This paper studies two-dimensional magnetohydrodynamic (MHD) flow and heat transfer of fractional Oldroyd-B nanofluid between two coaxial cylinders with variable pressure. The boundary layer fractional cylindrical governing equations are firstly formulated and derived. Meanwhile, the numerical solutions are obtained by using the newly developed finite difference method combined with L1-algorithm, whose validity is confirmed by the comparison with the exact solution constructed. Results show that the fractional derivative parameters alpha(l), beta and exponent parameter delta related to the wall temperature have significant effects on velocity and temperature fields. Specifically, the velocity decreases with the augment of alpha(l), but increases as beta rises up. The temperature profiles intersect each other for different delta. Meanwhile, increasing delta leads to an increase in temperature near the wall of inner tube, but a decline near the outer cylinder, which demonstrates increasing exponent parameter can enhance heat transfer. (C) 2019 Elsevier Ltd. All rights reserved.