# Experimental Investigation on Jet Vector Deflection Jumping Phenomenon of Coanda Effect Nozzle
## 2 Experimental Setup and Methods
### Model Parameters and Experimental Setup
The passive secondary flow fluid thrust vectoring nozzle model was connected with the jet wind tunnel through the transition section. In the experiment, an Nd: YAG 200\(-\)MJ laser with a wavelength of 532 nm was used to illuminate the convection field. The shooting plane was perpendicular to the horizontal plane in the PIV experiment, and was located at Z/W = 0.5. The experiment performed at a velocity of 30 m/s and a free stream turbulence intensity below 0.3%. In the experiment, the dynamic pressure measurement was synchronized with the PIV experiment, and the dynamic force measurement experiment was carried out separately. Figure 3: The pulsed jet exciter. (**a**) Structure diagram of pulsed jet generator; (**b**) frequency characteristic curve of the pulsed jet generator. As shown in Figure 5a, an eight\(-\)channel pressure sensor module was used for dynamic pressure acquisition. The sensor used was SM5652\(-\)001\(-\)D\(-\)3\(-\)SR, compensated and calibrated by ceramic DIP under constant pressure excitation. Eight 8\(-\)channel pressure sensors with 64 channels and a pressure measuring the frequency of 1000 Hz were used in the experiment. Table 1 shows the technical parameters of the dynamic pressure sensor module. As shown in Figure 5b, the ATI\(-\)9610 six\(-\)component strain gauge balance made by ATI Corporation, USA, consisted of floating and fixed frames. The floating frame was fixed to the nozzle model, the bottom of the fixed frame was connected to the base, and the force, moment range, and total range measurement accuracy of the balance axes X, Y, and Z are shown in Table 2. The strain balance converted the acquired force signal into an electrical signal, amplified it through the back\(-\)end amplifier, and transmitted it to the NI data acquisition card for acquisition and storage. The acquisition frequency of ATI force balance was 200 Hz. The dynamic pressure measurement baseline results are shown in Figure 6a. The random error of the measured pressure value within 1800 ms met the instrument standard. Furthermore, the pressure fluctuation had no evident periodicity within 1800 ms, so the pressure measurement error did not affect the experimental results. The dynamic torque measurement baseline results are shown in Figure 6b. The random error of the measured torque value within 700 ms met the instrument standard. Furthermore, the pressure fluctuation had no evident periodicity within 700 ms, so the dynamic torque measurement error did not affect the experimental results. The calculation formula of the force vector angle was:  
\[\theta_{E}=\arctan(\text{F}_{X}/\text{F}_{Y}) \tag{1}\]  
\[\theta=\theta_{E}-\theta_{0} \tag{2}\]  
The force measurement results selected the forces F\({}_{X}\) and F\({}_{Y}\) in \(X\) and \(Y\) directions and calculated the thrust vector angle under various working conditions through Formula (1) \(\theta_{\text{C}}\). Zero vector angle \(\theta_{0}\) was the thrust vector angle measured by the force balance when the jet remained horizontal. The thrust vector angle obtained through the measurement and calculation of each experimental state \(\theta_{E}\) deducted the reference zero value of vector angle \(\theta_{0}\) to get the actual thrust vector deflection angle of the jet \(\theta\). Formulas (1) and (2) effectively eliminated the error caused by assembly with the model.