## 1 Introduction  
Film cooling is commonly applied to the hot section of a gas turbine in order protect the components from hot combustion gas. In film cooling, coolant is injected through discrete holes or slots and forms a thin film above the surface that needs to be cooled [1]. Since the film prevents the hot mainstream from transferring heat directly to the surface, heat transfer can be significantly reduced. The film cooing technique is usually applied to first stage vanes, rotors, and nearby endwalls that operate in high temperature conditions and experience high heat loads [2]. Since the coolant is extracted from a compressor and the amount of coolant is limited, many researchers have tried to improve film cooling effectiveness with the minimal use of coolant [3]. The turbine endwall is one region requiring sophisticated cooling techniques because it experiences high heat loads and thermal stress due to the complex flow phenomena [4]. On the turbine endwall, there are gaps (i.e., slots) between stationary vanes and rotating blades. In order to prevent the inhalation of hot combustion gas through these slots, coolant is injected through them. The injected coolant provides film protection on the endwall of the blade passage and blade leading edge. Many researchers have experimentally studied the effects of slot purge flow on turbine endwall film cooling in a linear turbine cascade. [PERSON] et al. [5] investigated the distribution of the Sherwoodnumber near the endwall slot using the Nepheline sublimation method. They also showed traces of the injected coolant using the oil-dot visualization method. [PERSON] et al. [6] conducted an experimental study on the effects of the momentum ratio on film cooling from a double slot located upstream of the leading edge of a vane. They showed that the distribution of the coolant was strongly affected by the momentum flux ratio. [PERSON] et al. [7] and [PERSON] et al. [8] installed slots simulating the stator-rotor seal of a gas turbine, and they then measured the film cooling effectiveness using the pressure sensitive paint (PSP) technique for different blowing ratios and mainstream turbulence levels. They showed that a high coolant flow rate was required to fully cover the turbine endwall with a single slot, or other discrete holes were required for a smaller coolant flow through the slot. There have been many attempts to actively control the flow using a dielectric barrier discharge (DBD) plasma actuator. The actuator consists of two electrodes and a dielectric barrier between them. One of the electrodes is exposed to the air and the other one is insulated from the air. Generally, the plasma is formed around the area between the edge of the exposed electrode and the insulated electrode [9]. The mechanism of the DBD plasma-induced airflow is still under discussion [10]. However, many researchers agree that when a sufficiently high amplitude AC to generate electron-ion pairs is supplied to the electrodes, an asymmetric electric field is formed and the gas near the exposed electrode is ionized [11; 12; 13; 14]. When the charged particles near the exposed electrode accelerate toward the insulated electrode, the particles collide and transfer momentum to the surrounding gas. As a result, the gas near the electrodes is induced toward the insulated electrode. This flow is called an induced flow [15]. DBD plasma is widely applied in various industries. It is used in ozone generation, pollution control, surface treatments, and flat plasma displays [16; 17]. In this study, flow control using a DBD plasma-induced flow is utilized in order to increase film cooling effectiveness. Since DBD plasma actuators have particular advantages--i.e., no moving parts, extremely fast response times, low mass, and low input power [11]--many researchers have tried to utilize them to control flow separation or actively control the flow itself. [PERSON] et al. [18] and [PERSON] et al. [19] applied simple DBD plasma on airfoil surfaces and successfully controlled the flow separation on those surfaces.