Ultrasonic Velocity Profiler Research Articles

Evaluation of the applicability of ultrasonic velocity profiling in conditions related to wet low intensity magnetic separation

The internal material transport and selection processes of the wet low-intensity magnetic separators (LIMS) are poorly understood; this calls for improved measurement techniques. In this work an ultrasonic velocity profiling (UVP) technique for measuring how material flow velocity varies with penetration depth is presented. A measurement depth of just a couple of centimetres would greatly improve the understanding of the separation process in a LIMS.When applied to flows of mineral suspensions with high volumetric solids concentration, similar to those in the separators, UVP is unique in combining:•Non-intrusive measurements.•Operates using just one sensor element (transducer).•Relatively good spatial resolution.•Penetrates opaque suspensions.•Fast sampling rate.Here, flows are studied in a rectangular duct (50×75mm). Using magnetite suspensions, measurement through the whole depth of 50mm is made with good accuracy. Velocity profiles are presented for solids concentrations of 5% and 9% solids by volume (20% and 36% by weight). Even at 9vol% solids it is possible to reach a penetration depth of more than 25mm.

Development of ultrasonic visualizer for capturing the characteristics of viscoelastic fluids

In the field of rheology, properties of non-Newtonian fluids have been traditionally represented on graphs such as viscosity curves. In this paper, we propose a visualizer to express the fluid properties as visualized fluid motions in a rotating cylinder. To highlight different fluid motions, three patterns of rotation were given to the cylinder: rapid start of constant rotation (spin-up), rapid stop from constant rotation (spin-down), and periodic rotation. Relationships between fluid motion and fluid properties are discussed by comparing velocity profiles for three fluids: silicone oil, yogurt, and a polyacrylamide (PAA) solution. Ultrasonic velocity profiler (UVP) was used to obtain spatio-temporal velocity maps. The velocity maps reflect essential rheological properties, such as shear thinning, yield stress, and elasticity. Two additional display modes are proposed to explore fluid motions due to viscoelasticity of the PAA solution and yogurt: a grid deformation field and a shear rate field. These two visualizations can provide intuitive understanding of viscoelasticity because deformation and shear rate determine elastic and viscous stresses, respectively. In spin-down tests, the recovery of deformed grids, which is caused by elasticity, can be explicitly observed. Further, the shear rate distributions indicate that kinetic energy of the fluid dissipates near the lateral wall right after the wall stops rotating. In short, these two quantity fields visualize energy conversion among kinetic, elastic, and thermal energy; such energy conversions are characteristic of viscoelastic fluids.

Fundamental uncertainty analysis of flowrate measurement using the ultrasonic Doppler velocity profile method

The present paper describes a fundamental uncertainty analysis for a flowrate measurement in a pipe using an ultrasonic Doppler velocity profile method and an evaluation of the estimated uncertainty by an actual flow calibration. The uncertainties are estimated for internal factors originating from the measurement equipment; UVP provided by Met-Flow sa. and external factors depending on on-site measurements, such as the inclination angle of the ultrasonic transducer. The relative expanded uncertainty due to internal factors is estimated to be 0.34% with a coverage factor of 2. The relative external uncertainty including external factors is estimated to be from 0.42% to 2.13% depends on the inclination angle of the transducer. The results of the actual flow calibration under the same condition as the uncertainty analysis are within the range of uncertainty considering the internal factors.

Use of UVP to investigate the evolution of bed configuration

Ultrasonic Velocity Profiler (UVP) is a widely used instrument which allows the determination of the complete velocity profile. UVP can also measure the echo amplitude in the mean time. In this study, it is intended to use the UVP transducers in an indirect way to detect the bottom surface by orienting them vertically downward. Preliminary experiments were conducted with immobile bed by using uniform, non-uniform sediment as well as wooden and plastic surface. It was appeared that the first remarkable peak corresponds to the bottom surface. The time variations of local bed elevations were registered by applying this technique in order to determine the erosion and deposition around a bridge pier and local scour around a horizontal submerged pipe. It was revealed that the so registered scour depths were in good agreement with those observed during the experiments. Consequently, it is demonstrated that time varied bed elevations can be measured via the first peak value of echo amplitudes by placing UVP transducers vertically.

Effect of low-frequency ultrasound on flow rate measurements using the ultrasonic velocity profile method

This study presents a low-frequency ultrasonic propagation analysis using the finite-element method (FEM). Experimental results of flow rate measurements using the ultrasonic velocity profile (UVP) method are also presented. The ultrasound frequency, pipe diameter, and pipe wall thickness are 0.274 MHz, 590.6 mm, and 9.5 mm, respectively. Six waves are generated per ultrasound pulse. To analyze the entire pipe region, the FEM is combined with the Kirchhoff method. The experiments of flow rate measurements are conducted using the high Reynolds number calibration facility at the National Metrology Institute of Japan. The range of the Reynolds number is from 4.4×106 to 1.7×107. Wide spreading of the ultrasonic beam in the axial direction of the pipe is observed because of multiple reflections in the pipe wall. This wide beam affects the measured velocity profile, particularly in the region near the pipe wall. In addition, the flow rate errors are approximately 10% (deviating by 1.1%) across the investigated range of Reynolds number. This result suggests that the experimental flow rate errors might be used as correction factors of flow rate measurements using the UVP method.

Estimating the number of transducers for flow rate measurement using the UVP method downstream of double elbows

This study proposes a new method that determines the number of transducers for accurate flow rate measurements using the ultrasonic velocity profile (UVP) method downstream of double elbows. Because the UVP method can measure velocity profiles over a pipe diameter and integrate them to obtain the flow rate, it is also expected to obtain an accurate flow rate using multiple transducers under asymmetric flow conditions formed downstream of elbows. The new estimation method employs the wavenumber of velocity profile fluctuation along a circle on a pipe cross-section, obtained by fast Fourier transform (FFT). The number of transducers was determined as twice the wavenumber at the foot of maximum Fourier amplitude, on the basis of the sampling theorem. The method was evaluated by a preliminary experiment and numerical simulations using computational fluid dynamics (CFD). The experimental and simulated velocity profiles were located at three times the pipe diameter (3D) and 1D downstream of the second elbow, respectively. Reynolds numbers for the experiment and simulations were set at 4×104 and 5×106, respectively. Using the number of transducers estimated by FFT, the standard deviations of flow rate errors were less than 1% or 2%, verifying the efficacy of the new method.

Experiments on Urban Flooding Caused by a Levee Breach

Breached levees often cause extensive flood damage to urban and residential areas; there has been considerable interest in the numerical modeling of flooding of urban areas in recent years. However, comprehensive data that describe the complex flow field in residential areas are not available for validating the numerical models or for determining the extent of such damage. To fill this gap, results are presented of experiments on a scale model used as a test setup that examined the flow field in an urban area attributable to flooding caused by a levee breach. Steady state flow depths and flow velocity were measured by a point gauge and by an array of ultrasonic velocity profilers, respectively. In addition, the surface velocities were recorded in the entire flooded area by using a digital particle tracking velocimetry technique. The details of these measurements, limited flow data, and the observed flow characteristics are presented in this study. Full data sets are provided on the Internet. The results of these investigations show that closely spaced buildings act like a single obstacle with a common wake zone, and there is little flow between these buildings. The results also show that the strongest flow is in the prebreach direction and that the local topography plays an important role in distributing the flow in the flooded area. The complete data set may be utilized to validate numerical models of free surface flow.

Relation between oil–water flow and extraction performance in liquid–liquid countercurrent centrifugal extractors with Taylor vortices

A countercurrent centrifugal extractor with an inner rotor and a stationary outer wall has been developed in which aqueous and organic phases flow countercurrently between two walls. The formation of stable Taylor vortices in the gap makes multistage extraction possible. Understanding the relation between flow state and percent extraction is important for achieving a greater number of theoretical stages in a single extractor. Hence, oil–water countercurrent flow is measured by ultrasonic velocity profiling, without disturbing the flow, under different feed rates of solutions and rotating speeds of the inner rotor. In continuous extraction tests, Zn2+ in nitric acid and di-(2-ethylhexyl)-phosphoric acid diluted by n-dodecane are used. Measurement results are verified by numerical simulation. Finally, a correlation chart of flow patterns and operating conditions is prepared.

Variation of forced convective heat transfer in rectangular duct flow of a magnetic fluid under magnetic field

Variation of forced convective heat transfer in a rectangular duct flow of a magnetic fluid under a magnetic field was investigated experimentally. Experiments were performed changing the magnetic field intensity, and this magnetic field could be varied from 0 mT to 600 mT. The Reynolds number based on the hydraulic diameter was set to 960, 1900 (laminar flow), and 2830 (turbulent flow). The results of the experiments show that in the case of laminar flow of the magnetic fluid, when a magnetic field is applied to a magnetic fluid flow, heat transfer locally increases in the region where the magnetic field exists. In contrast, in the turbulent flow of the magnetic fluid, heat transfer is not enhanced but reduced. In order to better understand this heat transfer phenomenon, we measured the velocity distribution of magnetic fluid flow by the Ultrasonic Velocity Profile (UVP) method. In the case of laminar flow, the result shows that the flow velocity at the center of the rectangular duct decreases and the velocity gradient in the near-wall region increases. Moreover, we calculated the flow resistance under a magnetic field by measurement of the pressure gradient, and the relationship between heat transfer and flow resistance was discussed.

Lubrication layer properties during concrete pumping

In order to progress in the understanding of the physical phenomena involved in the pumping process of concrete, we study in this work the properties of the lubrication layer, which forms between the pipe and the bulk material. Using ultrasonic velocity profiler, we measure the thickness of this lubrication layer in the case of real size pumping circuits. Our experimental, analytical and numerical results suggest that, from a rheological point of view, this layer behaves similarly as the constitutive mortar of the pumped concrete. Moreover, this layer thickness does not seem to depend on flow rate. We finally propose a simple analytical relation allowing for a rough estimation of the pumping pressure.

Effect of Number of Pulse Repetition and Noise on Velocity Profile Measurement in Ultrasonic Pulse Doppler Method

Ultrasonic pulse Doppler method has been widely used in many engineering field referred to as UVP (ultrasonic velocity profiler). Analysis algorithm in the UVP, number of pulse repetition (Npulse), noise and reflector conditions, etc. may affect on the measurement accuracy. The Npulse is related to the temporal resolution, and must be set as low as possible in order to improve the temporal resolution. However, it is known that accuracy of instantaneous velocity becomes worse with decreasing of the Npulse. In this study, effect of analysis algorithm in the UVP on velocity data was investigated with changing of the Npulse and SNR by simulation and experiments. As a result, it is shown that there is an appropriate Npulse in each algorithm depending on the SNR. An algorithm which decides the Doppler frequency from maximum value in the power spectrum, FFT-max, was relatively hard to be affected by noise. Difference of velocity standard deviation was small between lower and higher noise conditions when FFT-max with Npulse over the appropriate value was used for the calculation. Hence, FFT-max was the best analysis algorithm for measuring flow field compared with the autocorrelation.

C213 フェイズドアレイ超音波流速分布計測法を用いた流量計測に関する研究(OS9 熱・流動(4))

C213 フェイズドアレイ超音波流速分布計測法を用いた流量計測に関する研究(OS9 熱・流動(4))

WAVE FLUME-BASED EVALUATION OF SUSPENDED SAND TRANSPORT IN BREAKING WAVES

In this study, suspended sediment concentration and velocity in surf zones was measured in a small-scale wave flume with three breaker types (plunging, spilling and intermediate) using an optical concentration sensor and an ultrasonic velocity profiler (UVP). The sediment pickup rate was also calculated from the depth-averaged concentration and the wave energy flux dissipation rate. In plunging breakers, relatively large amounts of sediment are suspended in the transition region due to strong three-dimensional turbulent flows generated by large-scale vortices. In spilling breakers, sediment concentration is lower than that seen in plunging breakers because smaller- scale vortices typically develop below the water surface in the transition region. Concentrations in both breaker types remain at lower levels in bore regions because the vortices fully develop into weak turbulent bores. Comparison in the same range of wave energy flux dissipation rates showed that the sediment pickup rates in these small-scale experiments were approximately 103 times greater than those calculated by Goda (2010) using various data compiled from large-scale experiments and field observations.

Experimental and Numerical Investigations of Two-Dimensional Dam-Break Flows

This paper presents measurements of velocity profiles obtained from idealized dam-break experiments and results from numerical simulations of these experiments. Dam-break flows were generated in the laboratory by suddenly lifting a gate inside a flume for three different upstream heads with a dry-bed downstream condition. Ultrasonic Doppler velocity profilers were used for recording transient velocity profiles at eight different locations upstream and downstream of the removed gate. These experiments provided data on the spatio-temporal evolution of the flow field in an unsteady flow of relatively short duration. The two-dimensional experiments were simulated using a computational fluid dynamics solver. The following observations are made: (1) turbulence modeling does not affect the velocity profile in the upstream reservoir, but has significant influence on the prediction of downstream velocity; (2) the velocity magnitude at a specific location changes with time, but the shape of the velocity profiles remains similar; (3) an analytical solution for frictionless dam-break flow on a sloping bed and numerical simulation with the large eddy simulation (LES) modeling show satisfactory agreement with measured water surface profile; (4) nondimensionalization of reservoir-side velocity profiles resulting from different reservoir heads and at different locations from a specific head shows excellent collapse and reveals that the shear layer thickness of these profiles is approximately 5% of the initial reservoir head; (5) measurement and simulation with the LES model for turbulence show satisfactory agreement, suggesting that the LES modeling is a viable approach for an accurate prediction of dam-break flows.

Optimisation of Pulsed Ultrasonic Velocimetry system and transducer technology for industrial applications

Pulsed Ultrasonic Velocimetry, commonly referred to as Ultrasonic Velocity Profiling (UVP) in research and engineering applications, is both a method and a device to measure an instantaneous one-dimensional velocity profile in opaque fluids along a measurement axis by using Doppler echography. Studies have suggested that the accuracy of the measured velocity gradient close to wall interfaces need to be improved. The reason for this is due to distortion caused by cavities situated in front of ultrasonic transducers, measurement volumes overlapping wall interfaces, refraction of the ultrasonic wave as well as sound velocity variations (Doppler angle changes). In order to increase the accuracy of velocity data close to wall interfaces and solve previous problems a specially designed delay line transducer was acoustically characterised and evaluated. Velocity profiles measured using the delay line transducer, were initially distorted due to the effect of finite sample volume characteristics and propagation through the delay line material boundary layers. These negative effects were overcome by measuring physical properties of the ultrasonic beam and implementing a newly developed deconvolution procedure. Furthermore, custom velocity estimation algorithms were developed, which improved the time resolution and penetration depth of the UVP system. The optimised UVP system was evaluated and compared to standard transducers in three different straight pipes (inner diameters of 16, 22.5 and 52.8mm). Velocity data obtained using the optimised UVP system showed significant improvement close to wall interfaces where the velocity gradients are high. The new transducer technology and signal processing techniques reduced previously mentioned problems and are now more suitable for industrial process monitoring and control.

Determining the viscous behavior of non-Newtonian fluids in a flume using a laminar sheet flow model and Ultrasonic Velocity Profiling (UVP) system

The flow of non-Newtonian fluids in rectangular open channels has received renewed interest over the past number of years especially as large flumes are being used to transport tailings in countries like Chile. The effect of yield stress on the flow behavior is complex and not yet fully understood. The Ultrasonic Velocity Profiling (UVP) technique has been used to construct velocity profiles of non-Newtonian fluids flowing in a 10 m by 300 mm wide tilting flume. The contour maps were integrated to show that the velocity profiles were indeed correct. The thin film flow models available in the literature have been tested in terms of flow depth and Reynolds number. The measured profiles also show the influence of the side walls on the general flow features as the distance from the centre increases. The results reported herein span the laminar, transition and turbulent flow regions. As far as can be ascertained, it is the first time that this technique has been used to measure velocity profiles in opaque non-Newtonian fluids for open channel flow. It is shown here that, under appropriate conditions, the velocity profile and flow depth can be used to obtain the viscous properties of the fluids tested. Excellent correspondence between the rheological parameters inferred from the velocity profile measurements and that from the tube viscometry was obtained.

Decomposition of incident and reflected surface waves using an Ultrasonic Velocity Profiler

In this article a novel method for estimating incident and reflected waves in wave flumes is presented. Instead of using water surface measurements obtained with a series of wave gages, we used water velocity measurements inside the water column obtained with an Ultrasonic Velocity Profiler to decompose the wave field. The technique allows for the identification of the incident and reflected first harmonic waves and the incident and reflected free and bound second harmonic waves. Only velocity measurements over a small fraction of the first harmonic wavelength are necessary to obtain reliable results, making the method suitable for studies where the water depth is not constant. Wave measurements obtained in a wave flume using four wave gages and three levels of wave reflection are used to evaluate the new method with excellent results. Finally, since no calibration of the velocity profiler is necessary, it is foreseen that the method could be implemented in a stand-alone instrument that would give the user the wave field decomposition without the need of a case by case set-up and calibration.

Numerical and experimental investigation of onset of gas entrainment phenomenon

The phenomenon of surface aeration, entrapment of gas through liquid surface, is employed in many industrial processes such as ammonolysis, chlorination, waste water treatment, etc. Although many studies have been performed to establish the operational limits of surface aeration systems like stirred tank, the hydrodynamic conditions that characterize the onset remain elusive. In the present study, the onset of the gas entrainment phenomenon has been studied using experimental techniques such as Ultrasonic Velocity Profiler (UVP), Particle Image Velocimetry (PIV) and High Speed Photography (HSP) in conjunction with Large Eddy Simulations (LES). The LES could predict the experimental data within±15%. LES identified the phenomenon of onset of entrainment as the mechanism by which gas cavities on the surface, formed as a result of surface deformation and entrapped in surface flows, relieve them self of strain and regain force equilibrium over their surface. The effect of surface tension and viscosity of liquid on the onset of gas entrainment was studied by changing the respective values in the simulation. The reduction in either of these properties caused the critical strain rate experienced by cavity before entrainment to decrease. However, onset of gas entrainment was found to be more sensitive to changes in viscosity of the continuous phase as compared to surface tension of gas–liquid system.

F051004 超音波を用いた速度分布計測

An ultrasonic velocity profile (UVP) method can measure instantaneous one-dimensional velocity profile along the measuring line. It is non-intrusive technique, and it can be easily applied for existing facilities from outside of the test section. Furthermore, the UVP can be used for measuring opaque fluids. The technique was originally developed for use in medical field. Takeda utilized the UVP for measuring in engineering fields in 1986, and it has been widely used for the measurement of the fluid. Now it has been used for many applications such as Taylor-couette flow, liquid metal, multi-phase flow, rheology measurement, flow-rate measurement, and so on.

Study on the Optimal Number of Transducers for Pipe Flow Rate Measurement Downstream of a Single Elbow Using the Ultrasonic Velocity Profile Method

This paper presents a new estimation method to determine the optimal number of transducers using an Ultrasonic Velocity Profile (UVP) for accurate flow rate measurement downstream of a single elbow. Since UVP can measure velocity profiles over a pipe diameter and calculate the flow rate by integrating these velocity profiles, it is also expected to obtain an accurate flow rate using multiple transducers under nondeveloped flow conditions formed downstream of an elbow. The new estimation method employs a wave number of velocity profile fluctuations along a circle on a pipe cross-section using Fast Fourier Transform (FFT). The optimal number of transducers is estimated based on the sampling theorem. To evaluate this method, a preliminary experiment and numerical simulations using Computational Fluid Dynamics (CFD) are conducted. The evaluating regions of velocity profiles are located at 3 times of a pipe diameter () for the experiment, and 1 and for the simulations downstream of an elbow, respectively. Reynolds numbers for the experiment and simulations are set at and , respectively. These results indicate the efficiency of this new method.