Numerical studies of the Rayleigh-Benard convection process in a horizontal wavy enclosure containing CuO-water nanofluid are presented. Laminar, incompressible, buoyancy-driven, two-dimensional fluid flow and heat transfer in the single-component homogeneous fluid medium have been solved using SIMPLE algorithm-based finite volume solver. The Boussinesq's approximation is assumed to hold well for the conditions envisaged for the present case studies. Extensive sets computations are performed to elucidate the fluid flow behaviour and heat transfer characteristics in enclosures with wavy heat transferring surfaces for various volume fractions of CuO in water as well as for various waviness and phase shift options of the heat transferring surfaces by maintaining 8000<Ra<15500. The interaction of Benard cells with the wavy boundaries realizes improved heat transfer characteristics, and it is found to depend on the extend of buoyancy effect created by the temperature difference maintained and the orientation of the wavy surface.