Characteristics of combined electroosmotic flow and pressure-driven flow in microchannels with complex-wavy surfaces

► Recirculations are induced in pure PDF, but they are not formed in pure EOF. ► Recirculations are not generated in the favorable pressure gradient combined flow. ► Recirculations are induced in the adverse pressure gradient combined flow. ► EOF-to-PDF velocity ratio affects the thermal entrance length. ► Joule number affects the Nusselt number in the thermally fully developed region.