Abstract: Large eddy simulation (LES) is applied to study the effect of the thermal actuators on the vertical structures with a Mach 1.3 round jet. The thermal actuators are modelled as heat sources inside the groove. The noise reduction and mixing enhancement at two different actuation modes (m =±1 and m =±4) are explored. Results show that radial and circumferential velocity fluctuations are increased due to the actuation effect. It promotes the formation of streamwise vertical structure especially on the flapping plane at the mode m =±1. The aerodynamic noise distribution covers a wide range of frequencies with high amplitude at high frequencies. It is found that the actuation weakens aerodynamic noise in the range of high frequencies while the wall noise may be increased due to the actuation effect.