# Performance Development of Fluidic Oscillator Nozzle for Cleaning Autonomous-Driving Sensors
## 3 Research Results and Considerations  
### Analysis Base Model  
In the nozzle for cleaning autonomous-drive sensors, the flow goes back and forth between walls periodically due to the Coanda effect. Part of the main flow moves to the feedback-channel inlet ((d) in Figure 6). As the fluid flows inside the channel, the pressure increases, affecting the flow in the inlet area ((a) in Figure 6). The flow entering the feedback channel inlet ((d) in Figure 6) is released at outlet((f) in Figure 6) meets the main flow and forms a vortex, forming a reaction force and causing oscillations (gray circle in Figure 6). The flow meets the main flow and forms a vortex, forming a reaction force and causing oscillations (gray circle in Figure 6). If this flow pattern occurs periodically, a sweeping angle and frequency are formed. The sweeping angle was measured from when \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Model** & **Radius of Outlet** & **Radius of Outlet** & & **Radius of Outlet** & **Radius of Outlet** \\  & **Outlet** & **Curvature** & **Model** & **Outlet** & **Curvature** \\  & **(mm)** & **(mm)** & & **(mm)** & **(mm)** \\ \hline Base & 0.2 & 1.5 & RC12 & 0.2 & 1.2 \\ R2 & 0.02 & 1.5 & RC13 & 0.2 & 1.3 \\ R4 & 0.04 & 1.5 & RC14 & 0.2 & 1.4 \\ R6 & 0.06 & 1.5 & R4+RC9 & 0.04 & 0.9 \\ R8 & 0.08 & 1.5 & R4+RC10 & 0.04 & 1.0 \\ R10 & 0.1 & 1.5 & R4+RC11 & 0.04 & 1.1 \\ R12 & 0.12 & 1.5 & R6+RC9 & 0.06 & 0.9 \\ R14 & 0.14 & 1.5 & R6+RC10 & 0.06 & 1.0 \\ R16 & 0.16 & 1.5 & R6+RC11 & 0.06 & 1.1 \\ R18 & 0.18 & 1.5 & R8+RC9 & 0.08 & 0.9 \\ RC9 & 0.2 & 0.9 & R8+RC10 & 0.08 & 1.0 \\ RC10 & 0.2 & 1.0 & R8+RC11 & 0.08 & 1.1 \\ RC11 & 0.2 & 1.1 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Design parameter value. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Item** & **Value** & **Unit** \\ \hline Mesh type & Polyhedral & (-) \\ Base size & 0.2 & (mm) \\ Number of prism layers & 2 & (-) \\ Prism layers thickness & 0.05 & (mm) \\ Prism layers stretching & 1.5 & (-) \\ Minimum surface size & 0.04 & (mm) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Calculation grid setting. Figure 5: Boundary condition and calculation grid of base model. (**a**) Boundary condition. (**b**) Calculation grid. the crossflow stabilized. For frequency, the difference in total pressure and static pressure between the feedback-channel inlet ((d) in Figure 6) and the feedback-channel outlet ((e) in Figure 6) was calculated to determine the change in dynamic pressure, and the period was measured using the time difference. All internal flow patterns in this study were similar to the one shown in Figure 6.  
In the base model, we confirmed how pressure conditions affect the sweeping angle and frequency. As a result of the analysis, it was observed that the frequency increased with the increase in inlet pressure. As the pressure inside the nozzle increases, the inlet fluid speed increases. When the fluid inlet speed increases, the pressure decreases according to [PERSON]'s theorem and flows into the feedback-channel inlet at a high speed. As the pressure inside the nozzle increases, the crossflow in the feedback channel proceeds faster and the frequency increases. The sweeping angle and frequency for each variable are shown in Table 3. To measure the sweeping angle, the velocity distribution according to the change in inlet pressure was measured as shown in Figure 7. As the nozzle internal pressure increases, there is little change in angle, but the frequency increases (Figure 8). In the base model, the frequency doubled as the inlet pressure increased from 1.5 to 5.0 bar. When the inlet pressure is 2.5 bar or less, the sweeping angle tends to increase. However, for 3 bar or more, the sweeping angle is fixed at 54\({}^{\circ}\). However, the pressure variation has a minor effect on the sweeping angle. The inlet pressure is considered a major factor affecting the frequency.