关键词: 动应力集中系数（DSCF）, 半圆形脱胶, Green函数, SH波散射, finite difference method, couple stress fluid, chemical reaction, vertical cylinder, natural convection

Abstract:

The unsteady natural convective couple stress fluid flow over a semi-infinite vertical cylinder is analyzed for the homogeneous first-order chemical reaction effect. The couple stress fluid flow model introduces the length dependent effect based on the material constant and dynamic viscosity. Also, it introduces the biharmonic operator in the Navier-Stokes equations, which is absent in the case of Newtonian fluids. The solution to the time-dependent non-linear and coupled governing equations is carried out with an unconditionally stable Crank-Nicolson type of numerical schemes. Numerical results for the transient flow variables, the average wall shear stress, the Nusselt number, and the Sherwood number are shown graphically for both generative and destructive reactions. The time to reach the temporal maximum increases as the reaction constant K increases.
The average values of the wall shear stress and the heat transfer rate decrease as K increases, while increase with the increase in the Sherwood number.

Key words: dynamic stress concentration factor (DSCF), a semicircular disconnected curve, Green's function, scattering of SH-wave, chemical reaction, finite difference method, couple stress fluid, natural convection, vertical cylinder