# A Dual Frequency Ultrasonic Cleaning Tank Developed by Transient Dynamic Analysis
## 4 Result and Discussion
### Scheme to Develop Dual Frequency UCT  
In this section, we shall discuss acoustic pressure simulation results in the dual frequency UCT model that we developed using the TDA. We also include analysis of the results which led to a model suitable enough for commercial production. To save costs for the manufacturer, the original 28 kHz UCT model mentioned in Section 3.1 was chosen to be developed which was the same model reported in [30] and changed its frequency to be dual mode with 28 and 40 kHz transducers. The reasons why both frequencies were chosen are the production line is similar to the original UCT production and at these frequencies the models are popular for various jobs. It could be used to clean glasses, watches, gems, jewelry, small electronic parts, and others [31]. With support of information from the previous research [30], we designed this UCT with eight horn transducers. To boost cleaning efficiency, four transducers were placed linearly at the bottom of the tank, two transducers were placed horizontally on both sides of the tank. When the question about the optimal cleaning positions of 28 and 40 kHz transducers were raised, the TDA provided a satisfying answer to that. The simulation showed that there are two models of the most possible simulations as shown in Figure 10a,b named models A and  
Figure 8: Acoustic pressure distribution from the TDA of 28 kHz UCT for transducer power of (**a**) 300, (**b**) 350, and (**c**) 400 W.  
Figure 9: Acoustic pressure distribution from the TDA of 40 kHz UCT for transducer power of (**a**) 300, (**b**) 350, and (**c**) 400 W.  
B, respectively. The model A has two pieces of 28 kHz transducers on the sides which were placed horizontally and four pieces of 40 kHz transducers at the bottom of the tank, placed linearly. Oppositely, Figure 10b shows model B with four pieces of 28 kHz transducers at the bottom and two pieces of 40 kHz transducers on both sides of the tank. P\({}_{1}\) and P\({}_{2}\) were the central points which are 5.5 and 17.5 cm higher from the bottom of the tank, respectively. S\({}_{1}\) is vertical surface, 5.5 cm higher from the bottom of the tank while S\({}_{2}\) is horizontal surface, 17.5 cm higher from the bottom. We used the central points (P\({}_{1}\) and P\({}_{2}\)) and mentioned surfaces (S\({}_{1}\) and S\({}_{2}\)) as the reference points to analyze the acoustic pressure via the simulation. These positions all cover the places which the manufacturer recommended as they give rise to the highest cleaning efficiency. It was noted that both models share the same shape but have different dimensions and space between the transducers' positions. We used the fact that the transducers were located at the antinode of the rectangular UCT given higher amplitude than other positions. Figure 11 on the left shows the acoustic pressure's time domain while on the right shows the frequency domain of normalized power spectrum (NPS) which took acoustic pressure from the figure on the left and was calculated with fast Fourier transform (FFT) in MATLAB software for (a) model A, (b) model B, and (c) 28 kHz UCT at positions P\({}_{1}\) (blue) and P\({}_{2}\) (red). We simulated the acoustic pressure that occurred in the 28 kHz UCT in Figure 2 to compare the acoustic pressure from both dual and single frequency UCTs. Results of this simulation are displayed in Figure 11c. In addition, Table 2 shows the NPS values of models A, B, and 28 kHz at positions P\({}_{1}\) and P\({}_{2}\). In Figure 11a,b, both images on the left and right with positions P\({}_{1}\) and P\({}_{2}\) all clearly show ultrasonic waves merging which occurred from vibrations of the 28 and 40 kHz transducers. Small peaks on the right image occurred from acoustic pressure between ranges 0-0.05 ms which are not stable yet. In Figure 11a, from the left image, the ultrasonic waves arrived at P\({}_{1}\) before P\({}_{2}\) because P\({}_{1}\) was closer to the transducers than P\({}_{2}\).