## 1 Introduction
Due to the fluctuation of aerodynamic force or vortex shedding being mainly wind-induced oscillation, [PERSON] et al. [17] used a span-wise sinusoidal perturbation set on the two sides of a plate girder to disturb the span-wise vortex shedding and reduce the dynamic response of VIV. The results indicate that the vibration amplitude was reduced with a higher wave steepness in the span-wise sinusoidal perturbation. [PERSON] et al. [1] utilized a guide vane that was equipped in the lower sides of the Great Belt East Bridge to alleviate the airflow separation. This investigation indicated that the guide vane could suppress the alternating vortex shedding and mitigate the VIV responses. However, this method possesses slight control effectiveness at a low _Re_ because less airflow goes through the guide vane to form the jet flow. The technique of leading-edge and trailing edge holes and the communicating channel formed the self-suction-and-jet (SSI) flow as designed by [PERSON] et al. [18]. These experimental results showed a reduction of the unsteady surface pressure and aerodynamic force, and the near-wake flow structure was steadier. In addition, the unsteady flow was shifted further downstream by using the control method of SSJ flow. To avoid the strength limit of the suction or jet flow, the control scheme of active suction or jet flow is presented. [PERSON] et al. [19] adopted active suction holes that were distributed on the bottom surface of the box girder with a specific interval to produce a Mode A secondary unstable wake flow, which can deeply alleviate the fluctuating amplitude of the aerodynamic force that is acting on the bridge girder. [PERSON] et al. [20] designed an active control strategy with a leading-edge suction and trailing edge jet (LSTJ)) that were inserted in the box girder to control the unsteady flow structure and aerodynamic force. They found that the best control case alleviated the unsteady lift force by about 37.88% and shrank the unsteady wake flow area by about 69.90%. Inspired by the investigation result of [PERSON] et al. [20], we only set the jet holes in the trailing edge of a single box girder (SBG) model to control the unsteady surface pressure, aerodynamic force, and unsteady flow structure. The present study is to investigate the control ability of the trailing edge jet for alleviating the unsteady aerodynamic force and the flow field of a single box girder and study what can influence the local separation on the upper and lower surface near to the leading edge of the SBG model. Only the trailing edge jet can reduce the energy consumption compared with the LSTJ as presented by [PERSON] et al. [20]. The analysis methods of proper orthogonal decomposition (POD) and linear stability analysis were used to reveal the underlying control mechanisms of the trailing edge jets. The structure of the present paper is arranged as follows. The experimental setup, test model details with and without the trailing edge jets are given in Section 2. The analysis results of the surface pressure distribution, aerodynamic force, flow structure, POD modes, and linear stability analysis are presented in Section 3. The conclusions are given in the last section.