## 2 Structural Design and Working Principle  
Figure 1 illustrates the assembly schematic of a valveless piezoelectric pump with airfoil baffles. The pump primarily consists of inlet and outlet tubes with airfoil baffles (Number Name Clark Y), a pump chamber, a cover plate, and a piezoelectric vibrator with PZT-5A piezoelectric ceramic material. The pump body is assembled using a bolt connection method. In order to facilitate the smooth installation of the pipe in the pump flow and pressure test, and reduce the energy loss caused by the pipe diameter mismatch, we used a straight tube for the inlet and an elbow tube (with high diameter reduction) for the outlet. Table 1 presents the structural parameters of the piezoelectric pump. Figure 2 depicts the working principle schematic of the valveless piezoelectric pump with airfoil baffles. The piezoelectric vibrator, excited by an alternating voltage, vibrates, causing periodic changes in the volume of the pump chamber. When the volume of the pump chamber increases, the pressure within the chamber decreases, and external fluid, under the influence of a pressure differential, flows into the pump chamber through the inlet and outlet tubes. This phase is known as the suction mode of the piezoelectric pump. Conversely, when the volume of the pump chamber decreases, the pressure within the chamber rises, and the fluid, again under the influence of a pressure differential, flows out of the pump chamber through the inlet and outlet tubes. This phase is referred to as the pumping mode of the piezoelectric pump. According to Ref. [21], the fluid encounters less resistance when flowing from the leading edge to the trailing edge of the airfoil baffle (forward flow) compared to when it flows from the trailing edge to the leading edge (reverse flow), where the resistance is greater than that of the forward flow. Due to the unequal flow resistance generated by the fluid flowing over the airfoil baffle in both directions, the flow rates into and out of the inlet and outlet tubes during the suction and pumping processes of the piezoelectric pump are unequal. The arrow width marked in the inlet and outlet tube in Figure 2 represents the flow size. Thus, with the vibration of the piezoelectric vibrator, the pump can macroscopically produce a unidirectional pulsating output. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Chamber diameter & 38 mm \\ Chamber depth & 3 mm \\ Vibrator diameter & 40 mm \\ Airfoil chord length & 10 mm \\ Tube length & 27 mm \\ Inlet tube diameter & 8 mm \\ Outlet elbow tube diameter & 3 mm \\ Distance between airfoil and chamber & 12.5 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Structural parameters. Figure 1: Assembly diagram of the valveless piezoelectric pump with airfoil baffles. When the piezoelectric ceramic material is PZT-5A and the driving voltage is a sinusoidal function of the peak-to-peak value of 200 V, the flow resistance of the tubes significantly affects the output performance of the piezoelectric pump. The pressure loss coefficient (flow resistance coefficient) of the tube containing the airfoil baffle is denoted as follows:  
\[\xi=\frac{\Delta\text{p}}{\rho v^{2}/2} \tag{1}\]  
where \(\Delta p\) represents the pressure difference at the inlet and outlet of the tube with an airfoil baffle, \(\rho\) is the fluid density, and \(v\) is the average velocity of the fluid flowing through the outlet of the tube with an airfoil baffle. According to the Ref.