Numerical investigation on the effect of harmonic horizontal-axis rotation on laminar natural convection in an air-filled enclosure

•The mathematical model for natural convection in a harmonic rotation enclosure is established in a non-inertial frame, with the non-inertial forces fully considered.•The thermal and hydraulic behavior of the natural convection is found to present different features in the three proposed scenarios of the combinations of the dimensionless parameters.•The harmonic rotation is found to enhance the heat transfer, and the mechanism of heat transfer enhancement is explained by the interaction of the gravitational buoyancy and additional forces induced by harmonic rotation.