Direct numerical simulations (DNS) have been performed using open source computational fluid dynamics (CFD) package OPENFOAM to investigate the unsteady flow and heat transfer characteristics of primary and secondary corrugated wavy channels for fixed values of wavelength and amplitude by varying Reynolds number (Re). Computations are carried out by considering only one module of the wavy channel and applying periodic boundary conditions to reduce the time for computations. Numerical method has been validated thoroughly against the numerical and experimental results reported in the literature. Steady as well as unsteady flow characteristics in the primary and secondary corrugated channels have been elaborated and explained with the help of streamlines, velocity contours, isosurfaces of velocity, and Q value. Temperature and Nusselt number contours are presented to illustrate the heat transfer characteristics f wavy channels. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.