Ultrasonic Velocity Profiler Research Articles

Measurement of the condensation rate of vapor bubbles rising upward in subcooled water by using two ultrasonic frequencies

The condensation rate of vapor bubbles, defined by vc=−dR/dt where R is the spherical-equivalent bubble radius, t is time, is an important parameter to determine the interfacial-condensation heat and mass transfer in subcooled boiling. Previous measurements of the condensation rate were mainly based on the optical visualization. In the paper, the development of a new method that uses two ultrasonic frequencies for the measurement of the condensation rate in subcooled boiling is presented. The ultrasonic velocity profile (UVP) method is used for the velocity measurement. Two simultaneous UVP measurements by the two frequencies are exploited. The principle of the new condensation-rate-measurement method is established. In the method, the UVP data of the bubble surface velocity are used. In subcooled boiling, the bubble-surface velocity is affected by the condensation. The UVP measurement must capture correctly the condensation effect on the bubble-surface velocity. In order to confirm the applicability of the UVP method to the measurement of the surface velocity in this case, the growth rate of air bubbles from a nozzle submerged in water is measured and compared with the result of optical visualization and digital image processing. Such growth process is analogous to that of vapor bubbles in a boiling process, and it is the inverse of the condensation process. Evaluation of the new condensation-rate-measurement method is carried out by the measurements of adiabatic air–water-bubbly column and subcooled pool boiling in vertical round tube.

Regular flow reversals in Rayleigh-Bénard convection in a horizontal magnetic field.

Magnetohydrodynamic Rayleigh-Bénard convection was studied experimentally using a liquid metal inside a box with a square horizontal cross section and aspect ratio of five. Systematic flow measurements were performed by means of ultrasonic velocity profiling that can capture time variations of instantaneous velocity profiles. Applying a horizontal magnetic field organizes the convective motion into a flow pattern of quasi-two-dimensional rolls arranged parallel to the magnetic field. The number of rolls has the tendency to decrease with increasing Rayleigh number Ra and to increase with increasing Chandrasekhar number Q. We explored convection regimes in a parameter range, at 2×10^{3}<Q<10^{4} and 5×10^{3}<Ra<3×10^{5}, thus extending the regime diagram provided by Yanagisawa etal. [T. Yanagisawa et al., Phys. Rev. E 88, 063020 (2013)PLEEE81539-375510.1103/PhysRevE.88.063020]. Three regimes were identified, of which the regime of regular flow reversals in which five rolls periodically change the direction of their circulation with gradual skew of the roll axes can be considered as the most remarkable one. The regime appears around a range of Ra/Q=10, where irregular flow reversals were observed in Yanagisawa etal. We performed the proper orthogonal decomposition (POD) analysis on the spatiotemporal velocity distribution and detected that the regular flow reversals can be interpreted as a periodic emergence of a four-roll state in a dominant five-roll state. The POD analysis also provides the definition of the effective number of rolls as a more objective approach.

Effect of number of branches on the performance of fractal impeller in a stirred tank: Mixing and hydrodynamics

Number of blades of an impeller, impeller design and its positioning in a stirred tank is known to affect the mixing in a stirred tank reactor. The extent of non-uniformity in mixing from conventional impellers can be reduced significantly using a space-filling impeller like a fractal impeller. In this work, we report the effect of number of branches (and hence the number of blades) of fractal impeller on power consumption, mixing and hydrodynamics. Velocity measurements were carried out using ultrasonic velocity profiler (UVP). Measurements showed that the performance of fractal impeller with different configuration is equivalent, however, better than standard impellers in terms of mixing achieved per unit power consumption. No significant difference was observed in radial and axial mean velocity profiles for three different configurations. However, the tangential velocity was found higher for four branches than two and three branches FI. Two distinct circulation loops were observed in upper as well as lower half of the vessel in r–z plane. Strong tangential flow throughout the baffled vessel helps to achieve good mixing even at low rotational speeds.

Flow pattern assessment and design optimisation for an industrial solvent extraction settler through in situ measurements and CFD modelling

Mixer-settlers are widely employed for carrying out solvent extraction processes in various industries. In the mixer section, an emulsion of aqueous and organic phases is generated to achieve inter-phase mass transfer, which is followed by phase separation in the settler, where efficient separation is critical to the overall process economics. Settler performance depends on the flow pattern, which in turn is dependent upon various factors including settler internals, and inlet and outlet arrangements.A study was carried out to investigate the fluid flow behaviour inside an industrial settler, by means of both on-site measurements and computational fluid dynamics (CFD) modelling. An ultrasonic velocity profiler (UVP) was customized and used as the physical measurement tool. This instrument has the advantage of being able to make measurements in an opaque fluid. A highly non-uniform flow pattern was found, with regions of large-scale recirculation and short-circuiting. Comparison with the flow pattern obtained through CFD modelling demonstrated reasonable agreement.Since the flow pattern was considered to be poor, further numerical modelling was undertaken to investigate design improvements. Variations to several design parameters were assessed, mainly focussing on modification to the internal picket fences. Single-phase simulations were used as a fast screening tool, then the most promising modified designs were further assessed by two-phase simulations. Through quantitative assessment of the flow patterns obtained for proposed design modifications, the study has led to the identification of a design which substantially improves the flow pattern, which is expected to reduce entrainment losses and improve process economics.

Experimental and numerical visualizations of swirling flow in a vertical pipe

This paper presents a comparison between the experimental and numerical simulations of turbulent swirling flow induced by twisted tape in vertical pipe. A novel measurement technique, phased array ultrasonic velocity profiler (UVP), has been developed for 2D velocity field visualization in swirling flow. A phased array with basic frequency 4 MHz has been designed, it has eight piezoelectric elements and each element transmits ultrasound beam. The advantage of this sensor is that the ultrasound beam can be controlled easily by changing the time delay of signal transmission for each element. A vector reconstruction algorithm is presented showing how the velocity vector of particles can be calculated from Doppler-shift frequencies taken from the output signals of two receiver elements. Two-dimensional velocity field has been visualized and it is found, as expected, that the presence of swirl cause a significant increase in the magnitude of the measured tangential velocity. Furthermore, a numerical calculation is performed and qualitatively compared with experimental results. The numerical result is obtained by solving three-dimensional, Reynolds-averaged Navier–Stokes equations by the commercial CFD code FLUENT® v.14.5 with RNG k-e turbulence model. The qualitative comparison between phased array UVP and CFD results shows good agreement with the average velocity field. Experimental and numerical findings and parametric trends based on the effects of swirling flow are summarized and discussed.

Influence of obstacle plates on flowrate measurement uncertainty based on ultrasonic Doppler velocity profile method

To obtain the specific values of the flowrate measurement uncertainty using the ultrasonic Doppler velocity profile (UVP) method under disturbed flow conditions, experimental measurements were performed. To generate a disturbed flow, obstacle plates were installed upstream of the test section. To estimate which experimental parameter dominates the uncertainty, parametric examinations are conducted for the obstacle plate configuration, the distance between the obstacle plates and the measurement section, the incident angle of the ultrasonic beam, and the flowrate. The maximum deviation of the measured flowrate from the reference flowrate exceeds 2% when the flowrate is measured 8D downstream of the obstacle plate. At a distance of 25D downstream, the deviation is within the fundamental uncertainty level of the flowrate measurement using the UVP method. Because several uncertainty factors in this examination are cross-correlated with each other, the uncertainties of these factors are evaluated independently using analysis of variance (ANOVA). The total uncertainty is 7.98%, 1.97%, and 1.14% at 8D, 16D, and 25D, respectively.

Taylor渦バイオリアクター内の超音波速度計測

Flow measurement of spatio-temporal velocity field in a Taylor-Couette vortex flow (TVF) with a short annulus was investigated with using Ultrasonic Velocity Profiler (UVP). These methods have significant advantages over conventional methods since it can obtain the instantaneous spatio-temporal information as a function of space and time even in opaque multiphase flows like bioreactors. Boundary effects with a short annulus of TVF called Ekman boundary layer are considered generating the various modes of vortex structure. In the present study, axial mean and instantaneous component of velocity profiles in the axis direction are measured with using the UVP and its flow characteristics in higher Reynolds region with the Ekman boundary is analyzed with spectrum method. The wavy vortex flow, the modulated and the chaotic flow are visualized through the spatio-temporal velocity field. These results could be useful for investigating the chemical flow characteristics and designing the industrial chemical devices or bioreactor systems.

混相流計測に適用可能な超音波流速分布計測システムの開発

Ultrasonic Velocity Profiler; UVP method is applied to various fluid flows including the multiphase flow. Most UVP measurements were carried out using the commercial measurement devices. However, a flexibility of measurements is restricted due to that fact. This article discusses development of UVP measurement system. The system consists of a pulser/receiver, an ultrasonic transducer, an analog-to-digital converter and a PC. Selection guide of hardware is provided. Velocity estimation is performed with full-digital signal processing, which eliminates complicated adjustment of analog circuits as it used to be. Typical signal processing principle and its efficient implementation are discussed. Bubbly flow measurement using this system is presented as an example of application.

UVPの計測速度限界拡張と流量計測への応用

The ultrasonic velocity profile (UVP) method is a powerful tool for measuring velocity profiles in a pipe and it has been applied for measuring flow rate. In this paper, a velocity extension method for use with ultrasonic pulsed Doppler method is introduced to increase the maximum detectable velocity which is limited by the Nyquist sampling theorem. The measurement volume is shown to be among the important parameters that must be considered in assessing the traceability of the reflector during the pulse emission interval. Hence, a larger measurement volume is required to measure higher velocities. In order to improve the flow rate accuracy, multi-wave ultrasonic method is introduced. The velocity profiles in the near-wall region are measured using an 8-MHz sensor with a small diameter, while those far from the transducer are measured using a hollow 2-MHz sensor in the multi-wave transducer. The techniques are shown to be particularly effective for measuring higher flow rates in a large-diameter pipe.

Optimization of the Uvp+Pd Rheometric Method for Flow Behavior Monitoring of Industrial Fluid Suspensions

Ultrasonic Velocity Profiling (UVP) is a powerful technique for velocity profile measurements in research and engineering applications as it is the only available method that is cost-effective, rel ...

UVPによる流量計測の不確かさ評価研究

We introduce the uncertainty estimation of flowrate measurement using ultrasonic Doppler velocity profiler (UVP). A fundamental uncertainty analysis for a flowrate measurement in a pipe using UVP and an evaluation of the estimated uncertainty by an actual flow calibration are described. The relative expanded uncertainty due to internal factors is estimated to be 0.34% with a coverage factor of 2. In addition, experiments are carried out in a disturbed flow. Flowrate measurement is based on a multi-path measurement using three ultrasonic transducers. To generate the disturbed flow, obstacle plates are installed upstream of the test section. The maximum difference from the reference flowrate given by the national standard calibration facility of water flowrate is over 2% when the measurement is performed at 8D downstream of the obstacle plate. At 25D downstream of the obstacle plate, the deviation is within the fundamental uncertainty level.

超音波流速分布計を用いたレオメトリについて

We introduced our recent works on development of rheometry utilizing ultrasonic velocity profiling (UVP) that can capture spatio-temporal velocity information even in opaque fluids. Rheological properties describing relations in stress, strain and strain rate are reflected into flow field, and analyzing flow information obtained in simple unsteady flow configurations may provide the rheological properties. We adopted cylindrical vessel with regular oscillation on the cylinder wall as the configuration, and evaluated effective Newtonian viscosity of viscous oil with dispersed small bubbles and time-dependent behavior of montmorillonite suspension that is one of thixotropic fluids to demonstrate applicability of the rheometry. We also explained novel idea of ‘flow surface’ that aims to describe rheological properties without using rheology models.

Direct measurement of internal material flow in a bench scale wet low-intensity magnetic separator

In this work an ultrasound-based measurement method is used for monitoring suspension velocity and build-up of magnetic material inside a wet low-intensity magnetic separator, a process used e.g. in beneficiation of magnetite ores. Today the only available option is to monitor material transport between unit operations; i.e. flow rate, solids concentration, and particle size distribution of suspension flow in pipes are measured online using standard equipment.An acoustic backscatter system is fitted to the tank of a separator, and used to monitor the internal flow. A method called ultrasonic velocity profiling is used to capture internal velocity profiles. Simultaneously, the backscatter signal intensity is used to get indications about local solids concentration of the flow, and build-up of magnetic material. The methods are evaluated in realistic conditions, where the effect of varying factors relevant to machine performance is investigated. The included factors are; the slurry feed rate, the slurry solids concentration, the magnet assembly angle, and the drum rotational speed.The presented method gives useful information about the internal material flow inside the separator. The velocity measurements capture the, sometimes complex, internal flow patterns, for example the presence and velocity of a recirculating flow in the dewatering zone. Additionally, keeping a balanced material loading in the concentrate dewatering zone is important to separator performance. Using the signal backscatter intensity it is possible to qualitatively monitor this material loading. Generally these direct measurements can aid in improvements to machine design, process optimization, and process control.

In-line rheological characterisation of wastewater sludges using non-invasive ultrasound sensor technology

The performance of a new ultrasound transducer, which can measure velocity profiles non-invasively through high-grade stainless steel pipes, was evaluated for the first time with secondary wastewater sludges. This work is a follow-up study on the feasibility work initially done by the same authors. In-line process control based on accurate rheological characterisation for treated wastewater sludge could lead to significant savings in chemicals and will optimise dewatering processes producing drier sludges. In this work, a wastewater sludge at three concentrations was tested in order to investigate the capabilities of the in-line ultrasound technique for different viscosities and fluid properties. The rheological parameters obtained using the new ultrasound sensor and ultrasonic velocity profiling with combined pressure difference (UVP + PD) technique were compared with results obtained using conventional tube viscometry. Comparison with tube viscometer results showed that yield stresses could be overestimated by 120% if data are not available in the low shear-rate ranges. This non-invasive transducer proved to be sensitive enough to obtain flow curves over a large shear-rate range, improving the prediction of the yield stress and requiring about 50% less energy than the invasive system.Keywords: ultrasonic velocity profiling, UVP + PD methodology, sludge rheology, non-Newtonian, tube viscometry, non-invasive, sludge dewatering

Application of ultrasonic Doppler velocimetry to molten glass by using broadband phase difference method

An ultrasonic velocity profile (UVP) measurement in high temperature molten glass was presented using buffer rod technique. A ceramic buffer rod was used to transmit ultrasound into molten glass. The rod had a taper shape and porous cladding to suppress trailing echo, which is the spurious echo in the buffer rod measurement. The broadband signal processing method was presented to improve noise tolerance in velocity estimation. This method is based on the phase difference method, which is originally proposed as a narrowband method. Measurable distance of the UVP measurement was investigated combining the buffer rod and the broadband signal processing method. Experiment was conducted at the temperature from 1000°C to 1200°C. As a preliminary test, motion tracking in molten glass was successfully demonstrated.

The influence of grain size on the velocity and sediment concentration profiles and depositional record of turbidity currents

Cross-stratification formed by migrating dunes is ubiquitous in fluvial channel deposits, yet cross-stratification, specifically formed by dunes, is comparatively uncommon in deep-marine channel deposits subjected to similarly unidirectional flows, the reasons for which is the subject of much debate. In part, this is related to the difficulty associated with acquiring high-resolution data sets; natural turbidity currents are highly destructive, whereas physical models are hampered by the shortcomings of conventional laboratory instrumentation. Consequently the internal structure of turbidity currents is poorly understood, thus hindering the ability to identify the linkages between flow properties and depositional characteristics. In this study we use a medical-grade computed tomography scanner coupled with a three-dimensional ultrasonic Doppler velocity profiler to characterize the flow field and depositional morphology across a range of grain sizes ( d 50: 70–330 µm) and sediment concentrations (5%–17.5% by mass). Results show that the development of angular bedforms is suppressed in all flows with particle concentrations greater than 9.5% by mass, but notably also in all flows with particles <230 µm and sediment concentrations down to 5%, the lowest slurry densities used in these experiments, by mass. This suggests a first-order control on the response of the bed by the makeup of the overriding current. More fundamentally, we propose that grain size controls the character of near-bed density stratification, which is a requisite condition to generate the hydrodynamic instabilities that create the initial bed defects, which then lead to the development of angular bedforms like ripples and dunes.

Ultrasonic velocity profiling rheometry based on a widened circular Couette flow

We propose a new rheometry for characterizing the rheological properties of fluids. The technique produces flow curves, which represent the relationship between the fluid shear rate and shear stress. Flow curves are obtained by measuring the circumferential velocity distribution of tested fluids in a circular Couette system, using an ultrasonic velocity profiling technique. By adopting a widened gap of concentric cylinders, a designed range of the shear rate is obtained so that velocity profile measurement along a single line directly acquires flow curves. To reduce the effect of ultrasonic noise on resultant flow curves, several fitting functions and variable transforms are examined to best approximate the velocity profile without introducing a priori rheological models. Silicone oil, polyacrylamide solution, and yogurt were used to evaluate the applicability of this technique. These substances are purposely targeted as examples of Newtonian fluids, shear thinning fluids, and opaque fluids with unknown rheological properties, respectively. We find that fourth-order Chebyshev polynomials provide the most accurate representation of flow curves in the context of model-free rheometry enabled by ultrasonic velocity profiling.

Shear Stress and Hydrodynamic Recovery over Bedforms of Different Lengths in a Straight Channel

AbstractPools and riffles are common morphological features in rivers that are frequently used but poorly specified analogs in restoration design. Here, straight two-dimensional (2D) bedforms are conceptualized as perturbations and flow recovery is measured in a laboratory flume with an array of ultrasonic Doppler velocity profilers (UDVPs). The objectives are to (1) assess the variation of skin friction, turbulent stresses, and total stress; (2) assess the role of topographical feedback on flow recovery; and (3) compare flow recovery in isolated and bedforms in series. The results show that the total shear stress and near-bed turbulence greatly exceed the skin friction in decelerating flow and the pool and that hydrodynamic recovery tends to occur at length scales similar to geophysical scales despite potential negative feedback from the bed. Repeating short bedforms can push the flow to a more turbulent and laterally concentrated equilibrium condition. Implications for sediment entrainment thresholds, e...

Characteristic Time, Length and Velocity Scales of Transverse Flows in the Surf Zone

An ultrasonic velocity profiler (UVP) acquires instantaneous distributions of axial velocity along the ultrasonic beam emitted from the transducer. In this paper, organizations of the transverse flows over a span of a laboratory wave flume in the surf zone were identified experimentally on the basis of UVP measurements. Ensemble mean divergent and convergent flows were observed over the span of the flume in the surf zone regardless of breaker conditions. By analogy with the flow evolution in a previous computation, by Watanabe and Saeki [1999], we identified that the organization of the wave-breaking-induced counter-rotating vortices determined the spatial and temporal variations in the transverse flows at the early stages of the breaking process regardless of the widths of wave flumes and friction on the sidewalls and bottom. The observed transverse flows were driven by pairs of counter-rotating vortices produced under the breaking waves and the change in the orientation during the passage of breaking waves. The fundamental features of the transverse flows evolving in the breaking process, depending on the breaker type, are discussed statistically to parameterize velocity, time, and length scales of the variations of the transverse velocity. The dimensionless length and time scales had negative linear correlations with the Froude number (defined by relative transverse convection with respect to gravity) as well as a surf similarity parameter, which indicates that the gravity effect associated with the projections of the breaking wave crests defines the primary roller vorticity and shear intensity at the plunging location, resulting in destabilization of the flows in the transverse direction to form organized transverse flow structures.

준설토 이송시 유동효율에 미치는 전자기장 인가 영향에 대한 실험적 고찰

준설토 이송의 효율을 증가시키기 위한 연구로써 전자기력을 배관에 인가하여 유동저항을 줄이고, 윤활 층에서의 유속을 침강 임계속도이상으로 증가시키어 침강으로 인한 폐색을 방지하는 기술을 개발하였으며, 이를 대규모 장거리 송토현장에 적용하기 위하여 송토 거리 500m 규모의 현장에서 그 영향을 검토하는 실험을 진행하였으며, 실험결과 유동효율 증대로 인한 송토 유량이 30% 이상 증가함을 실험을 통해 보였다. 이를 검증하기 위하여 전자기장 인가장치와 계측장비로 초음파 유속 프로파일러를 사용하여 배관 내 유속프로파일을 모니터링 하여 그 데이터를 비교분석하여 효과를 검증하였다. As the research about increasing the efficiency of dredging soil transport, the technology, which reduce the friction between pipe wall and fluid in the pipe and disturbed generating pipe blockage, has been developed. So for the purpose of applying this technology to real construction site, main test has been tried at the real scale test in field(500m dredging soil transport length). As a test result, this paper will show 30% flow efficiency increasing by permitted electro magnetic force to the pipe. And test result was evaluated as a ultra sonic velocity profiler.