## 4 Results  
Figure 4 shows the distribution of the film cooling effectiveness for the case without plasma with blowing ratios of 0.5 and 1.0. The exposed electrode was installed at the 0 w location. However, power was not supplied to the electrode. Half of the film cooling effectiveness contours for each case were presented together for better comparison. The results showed that very high film cooling effectiveness was observed near the slot exit, and the film cooling effectiveness decreased downstream. Without plasma, the higher blowing ratio case (\(M=1.0\)) showed higher film cooling effectiveness at the same location. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Images** & **Subscript** & **Light Condition** &
\begin{tabular}{c} **Wind Tunnel** \\ **Condition** \\ \end{tabular} & **Coalant Injection** \\ \hline Black image & blk & Off & Off & Off \\ Reference & ref & On & Off & Off \\  image & air & On & On & Air \\  Foreign gas & fg & On & On & Coolant \\  image & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Images required for the pressure sensitive paint (PSP) technique. Figure 3: Pressure sensitive paint (PSP) calibration curve. For a quantitative comparison, the laterally-averaged film cooling effectiveness is presented at Figure 6. The laterally-averaged film cooling effectiveness for each case was not significantly different near the slot. However, the difference between the plasma-off and plasma-on cases increased downstream. Both cases showed higher laterally-averaged film cooling effectiveness, and the higher voltage case performed better. As the coolant was dragged down toward the endwall by the plasma-induced flow, the film cooling effectiveness increased, as shown in Figure 7. Since the strength of the plasma-induced flow was proportional to the input voltage and frequency [32], the higher input voltage resulted in higher film cooling effectiveness. The effect of the plasma on the film cooling effectiveness was more significant for the lower blowing ratio case (\(M=0.5\), Figure 5) because the coolant for the lower blowing ratio case had less momentum and could be relatively easily affected by the plasma-induced flow. Figure 6: Laterally-averaged film cooling effectiveness (\(L_{\text{e}}=0\) w). Figure 7: Schematic of the flow with the dielectric barrier discharge (DBD) plasma. Figure 8 presents the distributions of the film cooling effectiveness with the exposed electrode installed at the 10 w location. Again, these distributions were not significantly affected by the plasma operation. However, the laterally averaged film cooling effectiveness in Figure 9 clearly shows the effects of plasma on the film cooling effectiveness. The laterally-averaged film cooling effectiveness between the slot and the exposed electrode was almost identical for the plasma-off and plasma-on cases. However, the effects of plasma and input voltage on the film cooling were clearly observed downstream from the exposed electrode. The plasma-on cases showed higher averaged film cooling effectiveness, and the higher input voltage cases resulted in higher film cooling effectiveness in this region. Figure 8: Distributions of film cooling effectiveness (\(L_{\mathrm{e}}=10\) w). An important point is made apparent in Figure 9. Though the improvement of the film cooling due to the plasma only constitutes a few percent and may be within the level of measurement uncertainty, the almost identical laterally-averaged film cooling effectiveness between the slot and the exposed electrode for three different test conditions demonstrates the repeatability of the current test. Therefore, it can be asserted that DBD plasma can improve film cooling effectiveness even though the improvement was not significant in the test cases. Figure 10 shows the overall area averaged film cooling effectiveness for the tested cases. Regardless of the location of the exposed electrode or the blowing ratio, the higher input voltage case showed a higher averaged film cooling effectiveness.