▎ 摘　　要

In this paper, we study the thermal rectification in asymmetric U-shaped graphene flakes by nonequilibrium molecular dynamics simulations. The graphene flakes are composed of a beam and two asymmetric arms. It is found that the heat flux runs preferentially from the wide arm to the narrow arm, which indicates a strong rectification effect. The dependence of the rectification ratio upon the heat flux, the length and the width of the beam and the two arms is studied. It shows that the two asymmetric arms play the central role in thermal rectification and a proper design is needed to obtain the maximum rectification ratio. The result suggests a possible route to manage the heat dissipation in U-shaped graphene based nanoelectronic devices that have recently been fabricated.