Ultrasonic Velocity Profile Monitor Research Articles

D104 軸流を伴うテイラークエット渦流れのUVP計測(OS9 混相流動),動力エネルギーシステム部門20周年,次の20年への新展開)

Recently, a new chemical extraction method using Taylor-Couette vortex flow (T-CVF) is expected, because the extraction agent's contact and dispersion efficiency can be improved by use of T-CVF. Using this method, the amount of solvent and extraction agent can be reduced compared with the conventional methods, and environmental degradation and cost reduction are expected. For realizing the practical usage of this method, it is important to investigate T-CVF characteristics with axial flow including the inlet and the outlet. Therefore, in this study, we investigated the effects of axial flow on T-CVF structure using an Ultrasonic Velocity Profile monitor (UVP) can measure flow dynamic characteristics. From the measurement result, in the case with axial flow, the lift up phenomenon of T-CVF was confirmed.

21007 超音波アレイを用いた流速分布計測手法に関する研究(センサー・超音波,OS.12 流体計測技術の新展開,学術講演)

Ultrasonic velocity profile monitor (UVP) for the flow metering system has been developed. The principle of this system is based on the integration of instantaneous velocity profiles over a pipe diameter. This system is expected to be able to eliminate installation problems such as entry length as well as to follow transient flow rate precisely. In the previous study, the authors reported the results of multi-line flow rate measurement employing this method. However, the previous multi-line measurement requires a lot of ultrasonic transducers. Therefore the system was high cost performance and complicated. From this fact, the authors developed the ultrasonic array transducer for multi-line velocity profile measurements. The array transducer has 128ch elements on the same surface of the transducer. It is very useful techniques because it can measure cross section image using only one transducer. In this study the authors developed multi-line velocity profile measurement system in rectangular channel using UVP DUP with the array transducer. Furthermore the authors applied the array transducer to two phase flow measurements.

静止水中を上昇する単一大気泡周囲液相流れ場への管内径の変化が及ぼす影響

The measuring method of the averaged liquid velocity fields around a large bubble rising in stagnant liquid in a vertical round pipe using Ultrasonic Velocity Profile monitor (UVP), which the authors have developed in the previous report, was applied to make clear the effect of pipe inner diameter, D, on the velocity field in this report. Two ultrasonic transducers inclined +20 degrees and -20 degrees from the horizontal line, respectively, were used for the measurement to get two dimensional velocity vectors. Three pipes of D = 32, 42 and 54mm were used in the measurement. According to the measured results, the velocity fields in the liquid phase above the large bubble, in the liquid film around the large bubble, and in the wake were presented and discussed, focusing especially on the effect of pipe inner diameter D.

901 回転円柱まわりの流れ場に関する研究 : 円柱回転速度が一様でない場合(2)(OS9-1 超音波を利用した流動場の計測(流れ場計測),OS9超音波を利用した流動場の計測,オーガナイズドセッション)

The present study is designed to experimentally investigate the flow field past a circular cylinder rotating uniformly and oscillating rotationally in a uniform stream, and identify the wake vortex structures by varying the rotational speed ratio and oscillating frequency. Considering the Reynolds number dependency on flow structures, in this study, experiments were conducted with Re_d = 800, which is larger than a critical value. In order to observe and identify the flow patterns, the flow fields were visualized by the hydrogen-bubble method, and then the flow velocity pattern visualization was applied by using an ultrasonic velocity profile (UVP) monitor. Variation in the wake vortex structure according to the change of the oscillating frequency and the rotational speed ratio was examined.

Measurement of Averaged Liquid Velocity Field around Large Bubbles Using UVP

An Ultrasonic Velocity Profile monitor (UVP) measurement was performed to measure the averaged liquid velocity field in front of, around and behind the large bubble rising in stagnant water in a round pipe of inner diameter D=54 mm in order to obtain fundamental information for the gas liquid two-phase slug flows. Two ultrasonic transducers were used for the measurement to get velocity vectors. The measured results are presented and compared with some existing studies on the corresponding phenomena. In the liquid film near the bubble nose, velocity profiles are presented and compared with existing studies. The different of D may affect some features. The parameter z/D is found more dominant than z for this phenomenon. In the liquid phase behind the bubble tail or the wake region, a large ring vortex is recognized. The effect of bubble length on the vortex is also discussed. The upward velocity at the pipe axis agrees well the predicted results by an existing prediction.

Measurement of Averaged Liquid Velocity Field around Large Bubbles Rising in Stagnant Water in Round Pipe Using UVP

An ultrasonic velocity profile monitor (UVP) measurement was performed to measure the average liquid velocity field around a large bubble rising in stagnant water in a round pipe of inner diameter D=54mm in order to obtain fundamental information for gas-liquid two-phase slug flows. Two ultrasonic transducers were set at different directions to obtain velocity vectors. The measured results are presented and compared with the results of some previous studies on the corresponding phenomena. In the liquid film near the bubble nose, the difference in bubble length does not affect the acceleration. The parameter z/D is more dominant than z itself, particularly when z/D is less than unity. In the wake region, a large ring vortex is recognized. The upward velocity at the pipe axis agrees well with previously predicted results. The effect of bubble length on the vortex length is also discussed.

205 超音波速度分布計を用いた円柱後流の放出渦度測定(G05-2 物体周りの流れ,G05 流体工学)

205 超音波速度分布計を用いた円柱後流の放出渦度測定(G05-2 物体周りの流れ,G05 流体工学)

Microstructure of the flow field around a bubble in counter-current bubbly flow

Experimental study was made on the flow structure around a bubble in air–water bubbly flow. In order to measure velocity profiles around a bubble, an Ultrasonic Velocity Profile monitor was employed, which can obtain an instantaneous velocity profile along its measuring line across a channel. The experiments were carried out in a 100×10 mm 2 rectangular channel for the air–water counter-current bubbly flow whose void fraction smaller than 7%. The bubble Reynolds number was ranged between 700 and 1000. Most bubbles had ellipsoidal shapes and rose up with wobbling motions. Our experimental results plotted in the form of non-dimensional velocity profiles show that the velocity field around a bubble has a structure similar to the turbulent boundary layer on a solid wall. On the other hand, an earlier analytical study by Moore [J. Fluid Mech. 16 (1963) 161] used an assumption of a spherical bubble rising in liquid irrotationally, and the solution was derived that the flow around a bubble being composed of a thin boundary layer and its outer main stream in potential flow. In this paper, the relation between these two types of boundary layer structures is discussed.

The ultrasonic velocity profile measurement of flow structure in the near field of a square free jet

Coherent structures in the near field of a three-dimensional jet have been investigated. Experiments were carried out for a free jet issuing from a square nozzle using a water channel. Instantaneous velocity profiles were obtained in the axial and radial directions by using an ultrasonic velocity profile (UVP) monitor. Axial variations of dominant time-scales of vortex structures were examined from one-dimensional wavelet spectra. Wavenumber-frequency spectra were calculated by two-dimensional Fourier transform along the axial direction in a mixing layer, and it was found that a convective velocity of flow structures was nearly constant independently of their scales in space and time. Coherent structures in the axial direction were investigated in terms of proper orthogonal decomposition (POD). Eigenfunctions are similar to a sinusoidal wave, and reconstructed velocity fields by the lower-order and higher-order POD modes demonstrate large-scale and smaller-scale coherent structures, respectively.

901 超音波流速分布計による静止水中大気泡周囲の液速度分布の測定

Various methods are used for the velocity measurement of the gas-liquid two-phase flows, for example, Particle Image Velocimetry (PIV) or Laser Doppler Velocimetry (LDV), and ect. The Ultrasonic Velocity Profile monitor (UVP) has a unique feature that it can obtain an instantaneous velocity profile on a line. However, it has not been so far applied to the measurement of the multiphase flow in circular pipes. In this study, velocity distribution of a liquid film arround a large bubble in stagnant water which seems to be a simple type of gas-liquid two-phase slug flow in a vertical pipe was measured using UVP. It was found that the velocity distribution can be almost approximated by the profile curve of a general falling liquid film, while a liquid film receives the effect of tube wall especially near the nose.

Development of a thixotropic fluid flow in a pipe

This paper deals with the interaction between the modifications of the internal structure of a thixotropic fluid and the flow development along a pipe. The experimental set-up consists of a pipe, where a flow of thixotropic fluid is provided from a large vessel. The axial velocity distribution was determined using particle image velocimetry technique and ultrasonic velocity profile monitor. At the entrance section, the fluid is assumed to be in a homogeneous structural state corresponding to a high shear rate. The experimental results show a progressive flatness of the velocity profiles due to the aggregation of the structural elements of the fluid. The flow evolution is governed essentially by the kinetics of aggregation and segregation since the associated time scales are longer than the relaxation time of the flow.

K-1314 自由噴流変動速度場の超音波速度分布計による測定(S15-5 噴流計測)(S15 噴流・はく離流れの計測と制御)

Coherent structures in the near field of a free jet have been studied. Experiments are carried out for the free jets issuing from round and square nozzles using a water channel. Instantaneous velocity profiles are obtained in the radial direction by using an ultrasonic velocity profile (UVP) monitor. Coherent structures in the radial direction are investigated in terms of the proper orthogonal decomposition (POD). In the distributions of eigenfunction at each POD mode and energy contribution from each POD mode, there is no remarkable difference between round and square jets. In the power spectra of the random coefficient at the first POD mode, however, there is a broad peak in the case of round jet.

An experimental study on a wake behind a torus using the UVP monitor

The flow around a torus has a complicated three-dimensional structure. Measuring the spatiotemporal field of velocity by means of conventional methods such as hot-wire anemometers and other one-point measuring instruments is thus difficult. Research is made on the spatiotemporal structure of the wake behind the torus by using a flow-visualizing technique and an ultrasonic velocity profile (UVP) monitor, in which two kinds of tori with different diameter ratios or solidity are set in a uniform flow with zero inclination and oblique postures. For the torus with zero inclination, there are two modes of flow structure according to the diameter ratio; at lower ratio, a disk mode is dominant, and at higher ratio, a ring wake mode appears. For the torus set with an oblique posture, the structure of the wake changes with respect to the oblique angle in a complicated fashion. The power spectra of the fluctuating velocities reveal an aspect of the character of this structural change. The Strouhal numbers estimated from the power spectra suggest that the flow patterns can be classified into four categories with respect to the oblique angle.

Velocity and solids distribution in circular secondary clarifiers: Full scale measurements and numerical modelling

Results of full-scale measurements of flow velocity and solids distribution in a circular secondary clarifier are presented and evaluated using numerical modelling. The flow velocity distribution was measured by means of an ultrasonic velocity profile monitor. A two phase three dimensional model was applied to gain a better understanding of the observed flow patterns. The calculation was carried out for a two dimensional field assuming axisymmetric conditions. The momentum, continuity and k–ε turbulence equations were solved. Solid transport equations for a coupled system were employed. Circulating currents were found by modelling and in practice. The full scale velocity components in radial direction as well as the solids distribution showed a satisfactory agreement to the predicted values. At the outer tank rim no settled sludge was predicted by modelling whereas a very thin sludge blanket was found in reality, however. It is assumed that conveyance of the settled sludge by the scraper has not been properly described for the very outer tank zone. The solids content at the tank bottom was around 12gl−1. The maximum radial velocity components varied in the range of 10 to 17mms−1. High velocity components of up to 48mms−1 towards the tank bottom were found in the inlet region. By numerical modelling those high numbers could not be matched. The calculated values were being in the range of 21mms−1.

Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit, (III)

The authors have developed a new measurement system which consisted of an Ultrasonic Velocity Profile Monitor (UVP) and a Video Data Processing Unit (VDP) in order to clarify the two-dimensional flow characteristics in bubbly flows and to offer a data base to validate numerical codes for two-dimensional two-phase flow. In the present paper, the proposed measurement system is applied to fully developed bubbly cocurrent flows in a vertical rectangular channel. At first, both bubble and water velocity profiles and void fraction profiles in the channel were investigated statistically. In addition, the two-phase multiplier profile of turbulence intensity, which was defined as a ratio of the standard deviation of velocity fluctuation in a bubbly flow to that in a water single phase flow, were examined. Next, these flow characteristics were compared with those in bubbly countercurrent flows reported in our previous paper. Finally, concerning the drift flux model, the distribution parameter and drift velocity were obtained directly from both bubble and water velocity profiles and void fraction profiles, and their results were compared with those in bubbly countercurrent flows.

Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit, (III). Comparison of Flow Characteristics between Bubbly Cocurrent and Countercurrent Flows.

The authors have developed a new measurement system which consisted of an Ultrasonic Velocity Profile Monitor (UVP) and a Video Data Processing Unit (VDP) in order to clarify the two-dimensional flow characteristics in bubbly flows and to offer a data base to validate numerical codes for two-dimensional two-phase flow. In the present paper, the proposed measurement system is applied to fully developed bubbly cocurrent flows in a vertical rectangular channel. At first, both bubble and water velocity profiles and void fraction profiles in the channel were investigated statistically. In addition, the two-phase multiplier profile of turbulence intensity, which was defined as a ratio of the standard deviation of velocity fluctuation in a bubbly flow to that in a water single phase flow, were examined. Next, these flow characteristics were compared with those in bubbly countercurrent flows reported in our previous paper. Finally, concerning the drift flux model, the distribution parameter and drift velocity were obtained directly from both bubble and water velocity profiles and void fraction profiles, and their results were compared with those in bubbly countercurrent flows.

Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit, (II)

The authors have developed a measurement system which is composed of an ultrasonic velocity profile monitor and a video data processing unit in order to clarify its multi-dimensional flow characteristics in bubbly flows and to offer a data base to validate numerical codes for multi-dimensional two-phase flow. In this paper, the measurement system was applied for bubbly countercurrent flows in a vertical rectangular channel. At first, both bubble and water velocity profiles and void fraction profiles in the channel were investigated statistically. Next, turbulence intensity in a continuous liquid phase was defined as a standard deviation of velocity fluctuation, and the two-phase multiplier profile of turbulence intensity in the channel was clarified as a ratio of the standard deviation of flow fluctuation in a bubbly countercurrent flow to that in a water single phase flow. Finally, the distribution parameter and drift velocity used in the drift flux model for bubbly countercurrent flows were calculated from the obtained velocity profiles of both phases and void fraction profile, and were compared with the correlation proposed for bubbly countercurrent flows.

Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit, (II). Flow Characteristics of Bubbly Countercurrent Flow.

The authors have developed a measurement system which is composed of an ultrasonic velocity profile monitor and a video data processing unit in order to clarify its multi-dimensional flow characteristics in bubbly flows and to offer a data base to validate numerical codes for multi-dimensional two-phase flow. In this paper, the measurement system was applied for bubbly countercurrent flows in a vertical rectangular channel. At first, both bubble and water velocity profiles and void fraction profiles in the channel were investigated statistically. Next, turbulence intensity in a continuous liquid phase was defined as a standard deviation of velocity fluctuation, and the two-phase multiplier profile of turbulence intensity in the channel was clarified as a ratio of the standard deviation of flow fluctuation in a bubbly countercurrent flow to that in a water single phase flow. Finally, the distribution parameter and drift velocity used in the drift flux model for bubbly countercurrent flows were calculated from the obtained velocity profiles of both phases and void fraction profile, and were compared with the correlation proposed for bubbly countercurrent flows.

Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit

Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit

Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit.

The authors have been developing a measurement system for bubbly flow in order to clarify its multi-dimensional flow characteristics and to offer a data base to validate numerical codes for multi-dimensional two-phase flow. In this paper, the measurement system combining an ultrasonic velocity profile monitor with a video data processing unit is proposed, which can measure simultaneously velocity profiles in both gas and liquid phases, a void fraction profile for bubbly flow in a channel, and an average bubble diameter and void fraction. Furthermore, the proposed measurement system is applied to measure flow characteristics of a bubbly countercurrent flow in a vertical rectangular channel to verify its capability.