## 1 Introduction  
The improvement in the power and efficiency of gas turbines is largely dependent on the continuous increase of turbine inlet temperature. As a result, the turbine blades are subjected to high thermal load during operation, and are prone to ablation accidents. Although the performance of materials is constantly improving, it is still far from meeting the development need of gas turbines, thus effective thermal protection technologies must be adopted. In addition to the use of thermal battier coatings [1], coolant-based efficient cooling methods are essential for releasing the blade thermal load to reduce its temperature, and further ensuring the safe operation of gas turbines [2]. Blade cooling technology mainly includes internal cooling and film cooling [3]. In internal cooling, various heat transfer augmentation methods, including jet impingement [4], U shaped turning bend [5], and rough structures [6] are usually applied, and recently the closed cycle-based steam cooling technology [7] has been developed, greatly promoting the improvement of cooling performance. [PERSON] [8] of Texas A&M University systematically summarized the researches of their laboratory in turbine blade cooling for more than 20 years, covering experiment design and testing technologies, internal composite cooling technologies, tip cooling and other aspects, and pointed out the research priorities as well as development directions. The trailing edge is a special area in the blade and is a major consideration in the cooling design. [PERSON] and [PERSON] [9] pointed out that the heat transfer mechanism at the trailing edge was complicated and achieving efficient cooling was a challenging task. They explored the heat transfer characteristics of four typical trailing edge channels, and discussed the effects of channel configuration, rough structure, and cutback, which laid the foundation for further extensive study of trailing edge cooling performance. Cutback is an important cooling structure in the trailing edge, whose flow and heat transfer characteristics have been widely investigated. [PERSON] et al. [10] experimentally investigated the film cooling performance of trailing edge cutback with pin fins and ribs, and obtained the heat transfer coefficient and film cooling effectiveness within the blowing ratio range of 0.2-1.25. It was concluded that the internal turbulators had important influences on the film cooling performance. [PERSON] et al. [11] carried out numerical studies on the cutback cooling performance and analyzed the flow structures and evolution of vortices. [PERSON] et al. [12] discussed the effects of lip thickness on the cutback cooling performance using the DES (Detached-Eddy Simulation) method, and found that thicker lips enhanced the mixing of hot and cold fluids. [PERSON] et al. [13] arranged teardrop dimples at the trailing edge cutback, and tested the distributions of heat transfer coefficient and film cooling effectiveness by infrared thermal imaging technology. The PIV system was also applied to obtain the flow characteristics inside dimple cavity. Accordingly, the influence of flow structure on the heat transfer was explained. In the internal cooling of the trailing edge, various factors including channel types, lateral extraction, rotation effect, etc., should be considered to comprehensively evaluate the cooling performance. [PERSON] et al. [14] constructed trailing edge internal cooling channels with lateral slots, and numerically investigated the flow structures under rotating states using the SST (Shear Stress Transfer) turbulence model. The effects of rotation number and channel orientation were involved. The results showed that the rotating state significantly changed the flow structures. [PERSON] et al. [15] conducted experiment studies on the heat transfer characteristics of a trapezoidal trailing edge, and also considered the effect of lateral extraction.