# A Dual Frequency Ultrasonic Cleaning Tank Developed by Transient Dynamic Analysis
## 4 Result and Discussion
### Scheme to Develop Dual Frequency UCT
At P\({}_{1}\), the NPS of 40 kHz transducer (NPS40 kHz) was approximately 0.70 which was higher than NPS of 28 kHz transducer (NPS28 kHz) that was 0.48. This was because in model A, P\({}_{1}\) was placed nearer to the 40 kHz transducer than the 28 kHz transducer (see Figure 10). When we consider the P\({}_{2}\), NPS28 kHz was as high as 0.82 while NPS40 kHz was only 0.26. The reason is the P\({}_{2}\) was closer to the 28 kHz transducer than the 40 kHz one. For Figure 11b, the explanation is similar to above; placing the transducer in model B will change the NPS of both P\({}_{1}\) and P\({}_{2}\). At P\({}_{1}\), NPS28 kHz and NPS40 kHz changed to 0.53 and 0.32, respectively, while at P\({}_{2}\) NPS28 kHz and NPS40 kHz changed to 0.35 and 0.39, respectively. The image where ultrasonic waves merge in Figure 11a,b is similar to what was reported in Figure 2a by [PERSON], et al. [14] who studied the numerical increase of the cavitation effect caused by ultrasonic frequencies of 50 and 70 kHz. In Figure 11c, the left image clearly depicts that the acoustic pressure which occurred resulted from vibrations of only the 28 kHz transducer. There is no combination of two ultrasonic waves. This could once again confirm that the TDA yielded the accurate results. In this figure, the acoustic pressure at P\({}_{1}\) is higher than P\({}_{2}\) because position P\({}_{1}\) is closer to the transducer than P\({}_{2}\). The figure on the right also yielded relevant results; the NPS28 kHz had reached to the maximum value of 1.00 which was calculated by FFT using acoustic pressure of 51,630 Pa. The highest level at position P\({}_{1}\) was used as a reference value for normalization. We normalized the acoustic pressure and calculated in MATLAB until we found the NPS at different positions as shown in Table 2. Apart from the information in Table 2, we also calculated the NPS at different points as well. Simulation results also are consistent with each other. Figure 11: Acoustic pressure’s time domain (left) and normalized power spectrum’s frequency domain (right) for (**a**) model A, (**b**) model B, and (**c**) 28 kHz. Figure 10: Most possible models for simulation: (**a**) model A and (**b**) model B. From the results in Figure 11a-c and Table 2, the TDA helped to confirm that the intensities of the NPS depended on the positions of the transducers and frequencies, which also were consistent with the report in [28; 29; 30; 31]. Therefore, the model A is more suitable for the production than the model B as its NPS is higher in more places in the tank. However, it can be questioned whether the NPS could be used to confirm the UCT's cleaning efficiency or not as there is no research that had analyzed the results in this routine. To confirm the reliability of the analysis using NPS, we simulated the acoustic pressure distribution in terms of time at S\({}_{1}\) which was in the vertical position of Figure 12 for model A and Figure 13 for model B, respectively. Since the distribution shows the existence of ultrasonic waves, therefore in Figure 12 at 57.14 us, the ultrasonic waves from the 28 kHz transducers came from both sides. Consequently, at 87.50 us waves from the 40 kHz transducers below start to travel to S\({}_{1}\) then the waves from both sides start to merge. At 104.46-213.39 us the merged waves start to clearly form the distribution pattern. At 681.25 us, +max acoustic pressure occurred, and at 698.20 us, -max acoustic pressure occurred. After this period, the acoustic pressure may slightly change but would not exceed the +max and -max values. We may say that the distribution pattern of this period is the most suitable for cleaning as once reported in [28; 29; 30; 31]. This may avoid the standing waves and stable cavitation that may decrease cleaning efficacy. Figure 13 shows the merging of ultrasonic waves from both frequencies in S\({}_{1}\) for the model B.