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Ultrasonic Measurement of Velocity Profile on Bubbly Flow Using a Single Resonant Frequency^{ †}

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## Abstract

**:**

## 1. Introduction

## 2. Measurement Technique

#### 2.1. The Principle of Ultrasonic Velocity Profiler (UVP)

^{3}). Therefore, the velocity of a particle is assumed to be equal to the velocity of water. The echo signals reflected from moving particles contain Doppler signal. The Doppler frequency f

_{D}(x) directly relates to a velocity of moving particle. Consequently, the velocity of the particle at that position V(x) can be obtained as following Equation (1). Therefore, the velocity profile along channel diameter can be computed if tracer particles are sufficiently dispersed.

_{0}is the basic frequency of the ultrasonic wave, θ is the incident angle and x is a position or measurement channel.

#### 2.2. UVP Measurement in Bubbly Flow with Single Resonant Frequency

_{REP}). Hence, it is difficult to distinguish velocity in both phases. When this behavior occurs, multi-frequency and difference of amplitude in the Doppler signal are generated as shown in Figure 2. Therefore, advanced signal processing is required to analyze the effect of Doppler signal for decomposing Doppler frequency of particle and bubble. Then, the velocity of both phases can be classified.

_{n}is window length, S

_{n}is time step and P(k, f

_{D}) represents the energy density of spectra in time-frequency function.

## 3. Experimental Results and Discussion

#### 3.1. Velocity Profile Measurement of Single Phase and Bubbly Flow in the Pipe

_{L}200 m/s. The horizontal axis indicates the distance from the wall (r) nominalized by the pipe radius (R). The velocity distributions measured by UVP-DFD, UVP Original, and PIV, had almost agreement except near the vicinity of the wall. The small fluctuation occurs because there was the resonance of the overlapped regions between the ultrasonic wave and the pipe wall.

_{L}= 200 mm/s and U

_{G}= 5.3 mm/s. The average bubbles diameter in this experiment was about 3 mm. Figure 4c shows the measurement result of the bubbly flow. The graph shows the average data of velocity profiles. Liquid velocity distribution is the mean of 5000 profile and bubble rising velocity is averaged by a number of data obtained. The result of bubble velocity distribution after separation of UVP-DFD technique was verified with the PIV method. The velocity profiles measured by both methods are almost coincident with each other. The differences were an error of the three-dimensional motion of bubble. Liquid velocity profile after separation was obtained and compared with UVP Original. As a result, the velocity profile of UVP Original was higher than that of UVP-DFD obviously because the influence of bubble motion was not rejected from the profile and slip ratio between the bubble and liquid velocity that occurred. Hence, liquid velocity profile measurement of UVP-DFD in bubbly flow can be confidently trusted owing to delete the bubble velocity data. It can be concluded that UVP-DFD has the applicability to measure velocity profile on single phase and bubbly flow in the pipe since the good agreement of the measurement result with UVP Original and PIV method was obtained apparently.

#### 3.2. Velocity Profile Measurement of Bubbly Flow in a Bubble Column

## 4. Conclusions

## References

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**Figure 3.**Doppler frequency classification technique (DFD); (

**a**) function block diagram, (

**b**) example of processing in single-phase flow (only particle), (

**c**) example of processing in bubbly flow (with particle and bubble).

**Figure 4.**Measurement of single phase and bubbly flow in the vertical pipe; (

**a**) Experimental apparatus, (

**b**) Average velocity profile at U

_{L}= 200 mm/s on single phase flow, (

**c**) Average velocity profile at U

_{L}= 200 mm/s on bubbly flow.

**Figure 5.**Velocity profile measurement in bubble column; (

**a**) Experimental apparatus, (

**b**) Average velocity profile.

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**MDPI and ACS Style**

Wongsaroj, W.; Hamdani, A.; Thong-un, N.; Takahashi, H.; Kikura, H.
Ultrasonic Measurement of Velocity Profile on Bubbly Flow Using a Single Resonant Frequency. *Proceedings* **2018**, *2*, 549.
https://doi.org/10.3390/ICEM18-05445

**AMA Style**

Wongsaroj W, Hamdani A, Thong-un N, Takahashi H, Kikura H.
Ultrasonic Measurement of Velocity Profile on Bubbly Flow Using a Single Resonant Frequency. *Proceedings*. 2018; 2(8):549.
https://doi.org/10.3390/ICEM18-05445

**Chicago/Turabian Style**

Wongsaroj, Wongsakorn, Ari Hamdani, Natee Thong-un, Hideharu Takahashi, and Hiroshige Kikura.
2018. "Ultrasonic Measurement of Velocity Profile on Bubbly Flow Using a Single Resonant Frequency" *Proceedings* 2, no. 8: 549.
https://doi.org/10.3390/ICEM18-05445