# Experimental Investigation on Jet Vector Deflection Jumping Phenomenon of Coanda Effect Nozzle
## 2 Experimental Setup and Methods
### Model Parameters and Experimental Setup  
The Coanda effect nozzle is shown in Figure 2. The height of the main jet outlet was D = 40 mm, and the width was L = 100 mm. There are passive secondary flow control joints with height h = 4 mm and width W = 100 mm, respectively, at the upper and lower parts of the main jet outlet area. The Coanda wall had an 18\({}^{\circ}\) deflection angle with the main jet direction, the plate length L was 100 mm, and the size of the whole plate was 100 mm \(\times\) 100 mm. In this article, the fluid medium was air, and the incoming flow velocity was 30 m/s. At the upper and lower walls of the nozzle, four rows of pressure taps were arranged at S1 = 1.25D, S2 = 1D, S3 = 0.5D, and S4 = 0.1D, respectively. The pressure taps were connected with the dynamic pressure sensor to measure the dynamic pressure parameters of the wall. The vectoring nozzle controlled the injection flow of passive secondary flow by adjusting the opening of the control slot. The purpose of vector control was achieved by actively controlling the pulsed jet to control the main jet's flow. The pulsed jet convection field was used for active flow control to improve the jet deflection rate under the condition of the jet attached to the wall. The structure of the pulsed jet generator is shown in Figure 3a. The pulsed jet exciter used the active compressed air source as the energy input of the pulsed jet. The pressure reducing and stabilizing valve was used to ensure the speed stability of the output jet. The signal generator was used to generate the frequency signal. The signal amplifier was used to input the frequency signal  
Figure 1: Structure diagram of passive thrust vector. (**a**) Flow structure diagram of a jet under detachment condition; (**b**) flow structure diagram of jet deflection wall attachment condition. Figure 2: The Coanda effect nozzle model and structural dimension schematics. (**a**) The Coanda effect nozzle model in PIV Layout; (**b**) structural dimension of model and section diagram of PIV shot. into the high\(-\)frequency solenoid valve. Finally, the high\(-\)frequency electromagnetic valve controlled the jet to output the constant frequency pulse jet. Among them, the model of a high\(-\)frequency solenoid valve was ZTO\(-\)45A\(-\)AA1\(-\)DDFA\(-\)1 BA, which was driven by a 24 VDC power supply, the maximum control frequency was 233 Hz, the power on response time was 6 ms, and the power off response time was 2 ms. The pulsed jet adopted an active air source, and inputted a square\(-\)wave signal with a duty cycle of 50% through the signal generator to control the high\(-\)frequency solenoid valve. By adjusting the frequency of the square wave signal, two jet holes could release a pulsed jet with a specific frequency. The diameter of the two pulsed jet holes was d = 2.5 mm, and the spacing was 1.5D = 60 mm. The curve of the velocity of pulsed jet, varying with frequency, is shown in Figure 3b. The velocity of the jet of the active source was V = 100 m/s, and the velocity of the pulsed jet decreased with the increase of the control frequency. The momentum ratio of the pulsed jet to the main jet was 1.47-0.736%. The location of the jet hole was the lowest CP coefficient points (Z/W = 0.2, X/L = 0.215) and (Z/W = 0.8, X/L = 0.215) when the jet was in attachment condition. Figure 4 shows the schematic diagram of the jet wind tunnel platform. In the experiment, the charge\(-\)coupled device (CCD) camera was used to record the flow field data, and its resolution was 2048 \(\times\) 2048 pixels\({}^{2}\). The model of the CCD camera was Fast\(-\)CAM Mini ax50, and the camera's resolution was 1024 \(\times\) 1024. The sensor adopted a CMOS sensor. The frame rate could reach 2000 Hz, and the minimum exposure time was 1.05 \(\upmu\)s. The dynamic flow field structure in jet deflection and wall attachment was qualitatively displayed. The physical parameters in the dynamic flow field were measured.