The Experts below are selected from a list of 8718 Experts worldwide ranked by ideXlab platform
Hideo Nakamura - One of the best experts on this subject based on the ideXlab platform.
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Bubbly to cap Bubbly Flow transition in a long 26 m vertical large diameter pipe at low liquid Flow rate
International Journal of Heat and Fluid Flow, 2015Co-Authors: Xiuzhong Shen, Takashi Hibiki, Hideo NakamuraAbstract:Abstract The concurrent upward two-phase Flow of air and water in a long vertical large diameter pipe with an inner diameter ( D ) of 200 mm and a height ( z ) of 26 m ( z / D = 130) was investigated experimentally at low superficial liquid velocities from 0.05009 to 0.3121 m/s and the superficial gas velocities from 0.01779 to 0.5069 m/s. The resultant void fractions range from 0.03579 to 0.4059. According to the observations using a high speed video camera, the Flow regimes of Bubbly, developing cap Bubbly and fully-developed cap Bubbly Flows prevailed in the Flows. The developing cap Bubbly Flow appeared as a Flow regime transition from Bubbly to fully-developed cap bubble Flow in the vertical large diameter pipe. The developing cap Bubbly Flow changes gradually and lasts for a long time period and a wide axial region in the Flow direction, in contrast to a sudden transition from Bubbly to slug Flows in a small diameter pipe. The analysis in this study showed that the Flow regime transition depends not only on the void fraction but also on the axial distance in the Flow and the pipe diameter. The axial Flow development brings about the transition to happen in a lower void fraction Flow and the increase of pipe diameter causes the transition to happen in a higher void fraction Flow. The measured void fraction showed an N -shaped axial changing manner that the void fraction increases monotonously with axial position in the Bubbly Flow, decreases non-monotonously with axial position in the developing cap Bubbly Flow, and increases monotonously again with axial position in the fully-developed cap Bubbly Flow. The temporary void fraction decrease phenomenon in the transition region from Bubbly to cap Bubbly Flow can be attributed to the formation of medium to large cap bubbles and their gradual growth into the maximum size of cap bubble and/or cluster of large cap bubbles in the developing cap Bubbly Flow. In order to predict the N -shaped axial void fraction changing behaviors in the Flow regime transition from Bubbly to cap Bubbly Flow, the existing 12 drift flux correlation sets for large diameter pipes are reviewed and their predictabilities are studied against the present experimental data. Although some drift flux correlation sets, such as those of Clark and Flemmer (1986) and Hibiki and Ishii (2003) , can predict the present experimental data with reasonable average relative deviations, no drift flux correlation set for distribution parameter and drift velocity can give a reliable prediction for the observed N -shaped axial void fraction changing behaviors in the region from Bubbly to cap Bubbly Flow in a vertical large diameter pipe.
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upward air water Bubbly Flow characteristics in a vertical square duct
Journal of Nuclear Science and Technology, 2014Co-Authors: Haomin Sun, Tomoaki Kunugi, Xiuzhong Shen, Hideo NakamuraAbstract:In nuclear engineering fields, gas–liquid Bubbly Flows exist in channels with various shape and size cross-sections. Although many experiments have been carried out especially in circular pipes, those in a noncircular duct are very limited. To contribute to the development of gas–liquid Bubbly Flow model for a noncircular duct, detail measurements for the air–water Bubbly Flow in a square duct (side length: 0.136 m) were carried out by an X-type hot-film anemometry and a multi-sensor optical probe. Local Flow parameters of the void fraction, bubble diameter, bubble frequency, axial liquid velocity and turbulent kinetic energy were measured in 11 two-phase Flow conditions. These Flow conditions covered Bubbly Flow with the area-averaged void fraction ranging from 0.069 to 0.172. A pronounced corner peak of the void fraction was observed in a quarter square area of a measuring cross-section. Due to a high bubble concentration in the corner, the maximum values of both axial liquid velocity and turbulent kine...
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Upward air–water Bubbly Flow characteristics in a vertical square duct
Journal of Nuclear Science and Technology, 2013Co-Authors: Haomin Sun, Tomoaki Kunugi, Xiuzhong Shen, Hideo NakamuraAbstract:In nuclear engineering fields, gas–liquid Bubbly Flows exist in channels with various shape and size cross-sections. Although many experiments have been carried out especially in circular pipes, those in a noncircular duct are very limited. To contribute to the development of gas–liquid Bubbly Flow model for a noncircular duct, detail measurements for the air–water Bubbly Flow in a square duct (side length: 0.136 m) were carried out by an X-type hot-film anemometry and a multi-sensor optical probe. Local Flow parameters of the void fraction, bubble diameter, bubble frequency, axial liquid velocity and turbulent kinetic energy were measured in 11 two-phase Flow conditions. These Flow conditions covered Bubbly Flow with the area-averaged void fraction ranging from 0.069 to 0.172. A pronounced corner peak of the void fraction was observed in a quarter square area of a measuring cross-section. Due to a high bubble concentration in the corner, the maximum values of both axial liquid velocity and turbulent kine...
Masanori Aritomi - One of the best experts on this subject based on the ideXlab platform.
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application of ultrasonic doppler method for Bubbly Flow measurement using two ultrasonic frequencies
Experimental Thermal and Fluid Science, 2005Co-Authors: Hideki Murakawa, Hiroshige Kikura, Masanori AritomiAbstract:Abstract In this paper, a new technique for multi-phase Flow measurement is proposed. This technique is based upon an ultrasonic Doppler method (UDM). Using different sizes of ultrasonic transducers (TDXs) for the UDM measurement, the measured data apparently differ. With a change in the measurement volume, the velocity PDF significantly changes. Applying this method for multi-phase Flow, several types of particles whose sizes are considerably different can be obtained for each velocity distributions. To obtain each velocity at the same time and at the same position, a new Multi-wave TDX is developed. Using the Multi-wave TDX, this method was utilized for the measurement of Bubbly Flow in vertical pipe. To confirm the accuracy of each velocity distribution, the velocity PDFs were calculated. The results clarified that this method has high applicability.
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Measurement of Bubbly Flow in a Vertical Pipe Using Ultrasonic Doppler Method
Volume 1: Fora Parts A B C and D, 2003Co-Authors: Hideki Murakawa, Hiroshige Kikura, Masanori Aritomi, Michitsugu MoriAbstract:In order to clarify the microscopic Flow structure, the ultrasonic Doppler method was applied to the measurement of two-phase Bubbly Flow in vertical pipe (i.d.50mm). Liquid Flow structure might strongly be influenced by the characteristic of the injected bubbles, i.e. bubbles’ size and void fraction. In this study, a bubble generator was newly designed with the purpose to control the bubble size and void fraction, independent of liquid main-Flow rate. The experiment was performed at z/d = 66 from the bubble generator. Liquid Flow rates were of the Reynolds numbers ranging from Rem = 3700 to 6200. The gas Flow rate was constant at JG = 0.00348(m/s) at the measurement position. By analyzing the bubbles’ picture, it was confirmed that bubble size distribution and average bubble size were almost constant if the liquid Flow rate were changed. The ultrasonic Doppler method has the capability of measuring the instantaneous velocity profiles of both phases at the same time. By processing the data based on pattern recognition, the recorded data can be classified to several groups. Using this method, the authors have tried to measure the Bubbly Flow in rectangular channel. In the present study, the application of this method to Bubbly Flow in circular pipe was satisfactory to obtain the liquid velocity distribution in Bubbly Flow and surrounding bubbles. From these results, it was clarified that velocity profile in Bubbly Flow in circular pipe has a maximum value near the pipe wall. Furthermore, velocity profiles around the bubble are influenced by leading bubbles.Copyright © 2003 by ASME
Mamoru Ishii - One of the best experts on this subject based on the ideXlab platform.
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interfacial structures and regime transition in co current downward Bubbly Flow
Journal of Fluids Engineering-transactions of The Asme, 2004Co-Authors: Seungjin Kim, Mamoru Ishii, Sidharth Paranjape, Joseph M KellyAbstract:The vertical co-current downward air-water two-phase Flow was studied under adiabatic condition in round tube test sections of 25.4-mm and 50.8-mm ID. In Flow regime identification, a new approach was employed to minimize the subjective judgment. It was found that the Flow regimes in the co-current downward Flow strongly depend on the channel size. In addition, various local two-phase Flow parameters were acquired by the multi-sensor miniaturized conductivity probe in Bubbly Flow. Furthermore, the area-averaged data acquired by the impedance void meter were analyzed using the drift flux model. Three different distributions parameters were developed for different ranges of nondimensional superficial velocity, defined by the ration of total superficial velocity to the drift velocity
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structure of vertical downward Bubbly Flow
International Journal of Heat and Mass Transfer, 2004Co-Authors: Takashi Hibiki, Mamoru Ishii, Seungjin Kim, Hiroshi Goda, Jennifer UhleAbstract:Abstract In view of the great importance to two-fluid model, structure of downward Bubbly Flows in vertical pipes has been discussed intensively based on available data sets of local Flow parameters including extensive air–water data sets recently measured by the authors. In this study, an approximate radial phase distribution pattern map has been proposed based on available data sets, and radial profiles of local Flow parameters such as void fraction, interfacial area concentration, interfacial velocity, and bubble Sauter mean diameter have been discussed in detail. The one-dimensional drift-flux model for a downward two-phase Flow and the correlation of the interfacial area concentration have been compared with the downward Flow data. The correlations applicable to the predictions of one-dimensional void fraction and interfacial area concentration for a downward Bubbly Flow have been recommended by the comparison.
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experimental study of interfacial area transport of Bubbly Flow in small diameter tube
International Journal of Multiphase Flow, 2003Co-Authors: Tomoji Takamasa, Takashi Hibiki, T Goto, Mamoru IshiiAbstract:Abstract In relation to the development of the interfacial area transport equation, this study was aiming at collecting accurate data sets on axial developments of local Flow parameters such as void fraction, interfacial area concentration, and gas velocity. The local Flow measurements of air–water Bubbly Flow in a vertical 9-mm-diameter tube were performed by means of a stereo image-processing method. A total of three data sets were acquired consisting of two gas Flow rates, 0.013–0.052 m/s, and two liquid Flow rates, 0.58–1.0 m/s at six axial locations. The data would be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase Flow.
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development of one group interfacial area transport equation in Bubbly Flow systems
International Journal of Heat and Mass Transfer, 2002Co-Authors: Takashi Hibiki, Mamoru IshiiAbstract:Abstract To finalize one-dimensional one-group interfacial area transport equation in Bubbly Flow systems, this study has conducted the developments of (I) refined sink and source terms of the interfacial area concentration based on mechanisms of bubble–bubble and bubble–turbulent eddy random collisions, (II) the correlations of two adjustable variables in sink and source terms, and (III) the correlation of the initial interfacial area concentration. The finalized one-dimensional one-group interfacial area transport equation has been validated by 55 data sets taken in extensive adiabatic air–water Bubbly Flow conditions in four different vertical pipes (pipe diameter: 25.4–50.8 mm). The Flow conditions of the data sets cover most of the Bubbly Flow regime, including finely dispersed Bubbly Flow and partly Bubbly-to-slug transition Flow (superficial gas velocity: 0.0144–4.88 m/s, superficial liquid velocity: 0.262–5.00 m/s, void fraction: 0.0124–0.443, interfacial area concentration: 22.1–1085 m −1 ). Excellent agreement is obtained between predicted and measured interfacial area concentrations with an average relative deviation of ±11.5%. Detailed discussions have been made on (i) the sensitivity analysis to the adjustable variables in the sink and source terms, (ii) the predominant term, (iii) the sensitivity analysis to the initial bubble size, and (iv) the comparison with TRAC-P code.
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distribution parameter and drift velocity of drift flux model in Bubbly Flow
International Journal of Heat and Mass Transfer, 2002Co-Authors: Takashi Hibiki, Mamoru IshiiAbstract:Abstract In view of the practical importance of the drift-flux model for two-phase Flow analysis in general and in the analysis of nuclear-reactor transients and accidents in particular, the distribution parameter and the drift velocity have been studied for Bubbly Flow regime. The constitutive equation that specifies the distribution parameter in the Bubbly Flow has been derived by taking into account the effect of the bubble size on the phase distribution, since the bubble size would govern the distribution of the void fraction. A comparison of the newly developed model with various fully developed Bubbly Flow data over a wide range of Flow parameters shows a satisfactory agreement. The constitutive equation for the drift velocity developed by Ishii has been reevaluated by the drift velocity calculated by local Flow parameters such as void fraction, gas velocity and liquid velocity measured under steady fully developed Bubbly Flow conditions. It has been confirmed that the newly developed model of the distribution parameter and the drift velocity correlation developed by Ishii can also be applicable to developing Bubbly Flows.
Hiroshige Kikura - One of the best experts on this subject based on the ideXlab platform.
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2D Velocity Vector Profile Measurement and Phase Separation on Swirling Bubbly Flow Using Ultrasound Technique
Volume 4: Fluid Measurement and Instrumentation; Micro and Nano Fluid Dynamics, 2019Co-Authors: Wongsakorn Wongsaroj, Hideharu Takahashi, Hiroshige Kikura, Natee Thong-unAbstract:Abstract Two-phase swirling Bubbly Flow is a complex phenomenon which occurs in several industries such as a nuclear reactor. Its characteristic is indispensably necessary to be investigated especially the multi-dimensional velocity distribution. This present paper describes the development of Ultrasonic Velocity Profiler (UVP) method which is a noninvasive measurement and needless of optical access, to obtain a two dimensional (2D) velocity distribution of the bubble and liquid phase in swirling Bubbly Flow simultaneously. The measurement result is represented in the form of the 2D velocity vector. To achieve the target, the multiple transducers and developed signal processing have been applied to the UVP system to measure a 2D velocity vector affected by bubble and liquid separately. For confirming the ability of Developed-UVP, the experiment was conducted on a vertical pipe co-current Flow apparatus. The UVP measurement was demonstrated non-intrusively and without the optical requirement. The measurement applicability of Developed-UVP was evaluated by comparing with Particle Image Velocimetry (PIV) method on liquid Flow and Bubbly Flow. Then, it was applied to obtain the 2D velocity vector in swirling Bubbly Flow. The velocity vector of the bubble and liquid could be separated clearly. Also, velocity distribution in swirling motion which was interacted of both phases was investigated understandably by using this measurement technique.
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Application of Short Time Fourier Transform in Ultrasonic Velocity Profiler on Bubbly Flow
2018 International Electrical Engineering Congress (iEECON), 2018Co-Authors: Wongsakorn Wongsaroj, Ari Hamdani, Natee Thong-un, Weerachon Treenuson, Hideharu Takahashi, Hiroshige KikuraAbstract:Two-phase Bubbly Flow is a common phenomenon in many industrial processes. To understand its characteristic, the velocity profile of liquid and bubble are necessary to be known accurately. The ultrasonic velocity profile (UVP) method has been known as a nonintrusive measurement method that can measure velocity profiles of fluid. Although the original UVP can measure velocity profile of two phase Bubbly Flow, it cannot distinguish liquid and bubble velocity. Therefore, the separation technique is used to overcome this limitation. The aim of this study was to develop signal processing of UVP method to measure liquid and bubble velocity profiles separately. Short Time Fourier Transform (STFT) was proposed to be applied in this case, and it was paralleled with other signal processing techniques. The experiment was conducted on vertical pipe Flow apparatus. The velocity profile measurement in two-phase Bubbly Flow was performed. Separation of liquid and bubble velocity was demonstrated. Moreover, the method was compared with other techniques experimentally.
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Ultrasonic Measurement of Velocity Profile on Bubbly Flow Using Fast Fourier Transform (FFT) Technique
IOP Conference Series: Materials Science and Engineering, 2017Co-Authors: Wongsakorn Wongsaroj, Ari Hamdani, Natee Thong-un, Hideharu Takahashi, Hiroshige KikuraAbstract:In two-phase Bubbly Flow, measurement of liquid and bubble velocity is a necessity to understand fluid characteristic. The conventional ultrasonic velocity profiler (UVP), which has been known as a nonintrusive measurement technique, can measure velocity profile of liquid and bubble simultaneously by applying a separation technique for both phases (liquid and bubble) and transparent test section is unnecessary. The aim of this study was to develop a new technique for separating liquid and bubble velocity data in UVP method to measure liquid and bubble velocity profiles separately. The technique employs only single resonant frequency transducer and a simple UVP system. An extra equipment is not required. Fast Fourier Transform (FFT) based frequency estimator paralleled with other signal processing techniques, which is called as proposed technique, was proposed to measure liquid and bubble velocity separately. The experimental facility of two-phase Bubbly Flow in the vertical pipe was constructed. Firstly, the Doppler frequency estimation by using the FFT technique was evaluated in single-phase liquid Flow. Results showed that FFT technique showed a good agreement with autocorrelation and maximum likelihood estimator. Then, separation of liquid and bubble velocity was demonstrated experimentally in the two-phase Bubbly Flow. The proposed technique confirmed that liquid and bubble velocity could be measured efficiently.
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application of ultrasonic doppler method for Bubbly Flow measurement using two ultrasonic frequencies
Experimental Thermal and Fluid Science, 2005Co-Authors: Hideki Murakawa, Hiroshige Kikura, Masanori AritomiAbstract:Abstract In this paper, a new technique for multi-phase Flow measurement is proposed. This technique is based upon an ultrasonic Doppler method (UDM). Using different sizes of ultrasonic transducers (TDXs) for the UDM measurement, the measured data apparently differ. With a change in the measurement volume, the velocity PDF significantly changes. Applying this method for multi-phase Flow, several types of particles whose sizes are considerably different can be obtained for each velocity distributions. To obtain each velocity at the same time and at the same position, a new Multi-wave TDX is developed. Using the Multi-wave TDX, this method was utilized for the measurement of Bubbly Flow in vertical pipe. To confirm the accuracy of each velocity distribution, the velocity PDFs were calculated. The results clarified that this method has high applicability.
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Measurement of Bubbly Flow in a Vertical Pipe Using Ultrasonic Doppler Method
Volume 1: Fora Parts A B C and D, 2003Co-Authors: Hideki Murakawa, Hiroshige Kikura, Masanori Aritomi, Michitsugu MoriAbstract:In order to clarify the microscopic Flow structure, the ultrasonic Doppler method was applied to the measurement of two-phase Bubbly Flow in vertical pipe (i.d.50mm). Liquid Flow structure might strongly be influenced by the characteristic of the injected bubbles, i.e. bubbles’ size and void fraction. In this study, a bubble generator was newly designed with the purpose to control the bubble size and void fraction, independent of liquid main-Flow rate. The experiment was performed at z/d = 66 from the bubble generator. Liquid Flow rates were of the Reynolds numbers ranging from Rem = 3700 to 6200. The gas Flow rate was constant at JG = 0.00348(m/s) at the measurement position. By analyzing the bubbles’ picture, it was confirmed that bubble size distribution and average bubble size were almost constant if the liquid Flow rate were changed. The ultrasonic Doppler method has the capability of measuring the instantaneous velocity profiles of both phases at the same time. By processing the data based on pattern recognition, the recorded data can be classified to several groups. Using this method, the authors have tried to measure the Bubbly Flow in rectangular channel. In the present study, the application of this method to Bubbly Flow in circular pipe was satisfactory to obtain the liquid velocity distribution in Bubbly Flow and surrounding bubbles. From these results, it was clarified that velocity profile in Bubbly Flow in circular pipe has a maximum value near the pipe wall. Furthermore, velocity profiles around the bubble are influenced by leading bubbles.Copyright © 2003 by ASME
Hideki Murakawa - One of the best experts on this subject based on the ideXlab platform.
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application of ultrasonic doppler method for Bubbly Flow measurement using two ultrasonic frequencies
Experimental Thermal and Fluid Science, 2005Co-Authors: Hideki Murakawa, Hiroshige Kikura, Masanori AritomiAbstract:Abstract In this paper, a new technique for multi-phase Flow measurement is proposed. This technique is based upon an ultrasonic Doppler method (UDM). Using different sizes of ultrasonic transducers (TDXs) for the UDM measurement, the measured data apparently differ. With a change in the measurement volume, the velocity PDF significantly changes. Applying this method for multi-phase Flow, several types of particles whose sizes are considerably different can be obtained for each velocity distributions. To obtain each velocity at the same time and at the same position, a new Multi-wave TDX is developed. Using the Multi-wave TDX, this method was utilized for the measurement of Bubbly Flow in vertical pipe. To confirm the accuracy of each velocity distribution, the velocity PDFs were calculated. The results clarified that this method has high applicability.
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Measurement of Bubbly Flow in a Vertical Pipe Using Ultrasonic Doppler Method
Volume 1: Fora Parts A B C and D, 2003Co-Authors: Hideki Murakawa, Hiroshige Kikura, Masanori Aritomi, Michitsugu MoriAbstract:In order to clarify the microscopic Flow structure, the ultrasonic Doppler method was applied to the measurement of two-phase Bubbly Flow in vertical pipe (i.d.50mm). Liquid Flow structure might strongly be influenced by the characteristic of the injected bubbles, i.e. bubbles’ size and void fraction. In this study, a bubble generator was newly designed with the purpose to control the bubble size and void fraction, independent of liquid main-Flow rate. The experiment was performed at z/d = 66 from the bubble generator. Liquid Flow rates were of the Reynolds numbers ranging from Rem = 3700 to 6200. The gas Flow rate was constant at JG = 0.00348(m/s) at the measurement position. By analyzing the bubbles’ picture, it was confirmed that bubble size distribution and average bubble size were almost constant if the liquid Flow rate were changed. The ultrasonic Doppler method has the capability of measuring the instantaneous velocity profiles of both phases at the same time. By processing the data based on pattern recognition, the recorded data can be classified to several groups. Using this method, the authors have tried to measure the Bubbly Flow in rectangular channel. In the present study, the application of this method to Bubbly Flow in circular pipe was satisfactory to obtain the liquid velocity distribution in Bubbly Flow and surrounding bubbles. From these results, it was clarified that velocity profile in Bubbly Flow in circular pipe has a maximum value near the pipe wall. Furthermore, velocity profiles around the bubble are influenced by leading bubbles.Copyright © 2003 by ASME
