Ultrasonic Doppler Velocimeter Research Articles

Development of the high temperature PbLi experimental facility for CFETR

Chinese Fusion Engineering and Test Reactor (CFETR) aims to demonstrate the fusion energy production up to 200MW, and finally reach commercial electricity power level 1GW. As one key component, the blanket is in charge of tritium breeding, neutron shielding and energy conversion. The liquid breeder blanket has many important advantages of simpler structure, tritium extraction and fuel replenishment online, as well as the high thermoelectric conversion efficiency. Moreover, the supercritical carbon dioxide (S-CO2) cOoled Lithium-Lead (COOL) blanket has been proposed for CFETR. However, the key issue of MagnetoHydroDynamics (MHD) needs further investigation, especially for the experiments. Therefore, the high temperature PbLi experimental loop is under development, which mainly includes three systems of PbLi, oil and water. The main components include the mechanical pump, main heater, cold trap as well as the superconducting magnet. At the test section, the mass flow rate, temperature and magnetic intensity will be up to 32 kg/s, 700 °C and 3T, respectively. In addition, the ultrasonic doppler velocimeter and potential probe instruments will be adopted to obtain the flow field. The main goal is to establish flow and heat transfer models, which are the critical input for the liquid breeder blanket design and optimization.

Effect of SDS surfactant on gas-liquid flow and slug characteristics in slightly upward pipeline

A new pigging approach with SDS (Sodium dodecyl sulfate) surfactant was proposed for foam drainage in the gathering pipelines with wet gas production, especially for the pipeline section with a great pigging risk. For this purpose, the loop of gas-liquid two-phase flow with a 3 ° slightly upward pipeline was designed. The flow pattern characteristics of gas-liquid two-phase flow were collected by a high-speed camera, and the flow patterns with typical morphological structure were classified. Ultrasonic Doppler velocimeter and ultrasonic transducer were used to measure the velocity signal of the liquid phase near the pipe, and the slug frequency was calculated accurately according to the change of velocity profile data. The slug length was measured by the signal collected by pressure and differential pressure transmitter. The results show that with the addition of SDS surfactant, the flow pattern of gas-liquid two-phase flow is obviously improved, and the working condition of slug flow is suppressed. Besides, in the specific slug flow condition, the slug frequency decreases significantly and the slug length increases. It indicates that the addition of SDS surfactant is favorable to liquid discharge, and provide a reference value for the application of SDS surfactant in foam drainage in wet-gas gathering pipelines.

Solidification front shape control through modulating the traveling magnetic field

This paper is concerned with studying the process of indirect control of the molten metal solidification front by means of modulating power supply of a linear induction machine (LIM). The influence of the LIM power supply mode on the flow in the molten metal is considered. The structure of the flow and the position of the solidification front are determined by a noninvasive method using an ultrasonic Doppler velocimeter. The obtained experimental data are used to determine the shape of solidification front profiles for four LIM power supply modes, and to establish the dependence of the shape of the front profiles on the characteristics of the supply current (magnitude and period of low-frequency modulation). A comparative analysis of the interphase boundary smoothing is carried out for different power supply modes of the LIM.

Study on the Liquid Metal Flow Field in Narrow-Side-Patter-Mold of Slab Continuous Casting

The flow pattern and velocity distribution of liquid metal in the Narrow-Side-Patter-Mold (NSP-Mold) have been investigated with a mercury model as analogue to molten steel in the continuous casting. The Ultrasonic Doppler Velocimeter (UDV) has measured the velocity under various magnetic distribution and flux density. The impingement intensity of liquid metal to mold narrow wall have been calculated based on the measured data, and the influence of magnetic flux density on the liquid metal flow in the mold has been analyzed. The results show that with narrow-side-patter magnet and increase of the magnetic field, the surface of the melt gets weak and the free surface fluctuation is suppressed, the impingement intensity of liquid metal to mold narrow wall gets weak, impacting depth becomes shallow and a plug flow can be rapidly formed.

Numerical and experimental study of the traveling magnetic field effect on the horizontal solidification in a rectangular cavity part 2: Acting forces ratio and solidification parameters

In recent decades, many phase change processes in metals have been optimized using traveling magnetic fields due to a better understanding of their electromagnetic impact in such applications. In this paper, numerical and experimental study of the effect of traveling magnetic field on the solidification process was evaluated. A three-dimensional numerical model based on the multi-domain method was used to analyze the process of gallium horizontal solidification under the electromagnetic impact in a laboratory-size rectangular cavity. A linear inductor creating traveling magnetic field was designed and built for appropriate measurements and validation the calculations. The analysis was focused on the influence of the ratio between the applied electromagnetic forces and natural convective forces on the solidification front location and shape and on the velocity field. Since the overall electromagnetic force impact on the melt reduced during the solidification, when the melt area was converting into a solid, a new approach to control the solidification parameters was analyzed. In this approach, the value of electromagnetic force acting on the remaining melt during the process was maintained. The main result is the development and improvement of an effective tool for the analysis of direct solidification parameters.The experimental setup included an ultrasonic Doppler velocimeter (UDV) for noninvasive measurements of the velocities in the liquid part of the metal and the liquid-solid interface position, its profile and displacement. All important characteristics of the process were measured, and the results of computations agreed well enough with experimentally obtained data.

Numerical and experimental study of the traveling magnetic field effect on the horizontal solidification in a rectangular cavity part 1: Liquid metal flow under the TMF impact

Traveling magnetic field is one of effective tools for controlling phase change processes in metals. A better understanding of electromagnetic impact in such applications can help to improve and simplify technological processes. In this paper, numerical and experimental study of the electromagnetic force generated by traveling magnetic field and its ability to control liquid gallium flow and, consequently, affect the characteristics of solidification and melting processes are evaluated. Three-dimensional numerical model for calculating the magnetic field distribution and electromagnetic force acting on liquid gallium in a laboratory-size rectangular cavity was analyzed. Specific values of the TMF impact were chosen for the cases of interest in order to use such impact in our further work with horizontal gallium solidification process. The traveling magnetic field inductor was designed and built for making appropriate measurements and validating calculations. The analysis was focused on the electromagnetic force and the obtained velocity field. The experimental setup included an ultrasonic Doppler velocimeter for noninvasive measurements of the velocities of liquid metal flow. The comparison of computations with the experiments has shown a good agreement.

Experimental investigation of low-frequency pulsed Lorentz force influence on the motion of Galinstan melt

The paper presents the results of the numerical and physical experiments, aimed at assessing the influence of pulsed force of electromagnetic field on the melt motion and the fluid velocities. The experiment was performed on the eutectic alloy Galinstan in the cylindrical volume, where an ultrasonic Doppler velocimeter was employed for velocity measurements under conditions of pulsed and steady EM field application. A numerical simulation of the melt flow, forced by the steady EM force, involved a 2D axisymmetric model. The k-ε turbulence model was used to obtain the information about the melt velocities. The verification of the numerical model was carried out for the steady case. The effects of pulsed and steadily applied Lorentz force were compared using the physical experiment. An intensity of the velocity pulsations in Galinstan for the pulsed frequencies in the range from 0.05 to 1Hz considerably exceeded the values measured in the permanently stirred melt. For higher values of pulsed frequencies (from 1 to 10Hz) the effect decreases and only slightly differs from the influence of the permanently applied Lorentz force.

Comparison of Three-Dimensional Multidomain and Single-Domain Models for the Horizontal Solidification Problem

In this paper, horizontal solidification of gallium in a rectangular cavity was studied both experimentally and numerically. Two three-dimensional (3D) numerical models related to different numerical approaches were built. The first is a single-domain (SD) model based on the volume-of-fluid (VOF) method. This model also takes into account the presence of a mushy zone. The second model is a multidomain (MD) one; it includes two different meshes for the two phases and uses Stephan's boundary condition to determine the front velocity. The 3D models were tested under various thermal boundary conditions and compared with experimental results obtained in an appropriate experimental setup. The experimental setup included an ultrasonic Doppler velocimeter (UDV) for noninvasive measurements of the velocities in the liquid part of the metal, liquid–solid interface position and profile, its displacement, and longitudinal mean velocity. For determining the boundary influence, both 3D and 2D models were built. The comparison was carried out for the solidification front location and shape and the velocity and temperature fields. In general, the 3D numerical model gave more accurate results than the 2D model with respect to the experiments results. Although the MD model is more complicated to build and requires more computational efforts than the VOF model, the 3D MD model provides the most accurate results in comparison with current experiments.

Study on the liquid metal flow field in FC-mold of slab continuous casting

The flow pattern and the velocity distribution of a liquid metal in the flow control mold (FC-mold) were investigated with a mercury model by analogy to the molten steel during continuous casting. The velocity measurement was conducted by the ultrasonic Doppler velocimeter (UDV) under various magnetic distributions and flux densities. The impingement intensity and the scouring intensity of the liquid metal to the narrow wall of the mold were calculated based on the measured data, and the influence of the magnetic flux density on the liquid metal flow in the mold was analyzed. The results showed that the surface of the liquid metal became more active when only the lower magnet was assembled, and the surface fluctuation was suppressed when further applying the upper magnetic field. It was indicated that when the upper and lower magnetic flux densities were 0.18 T and 0.5 T, respectively, the optimum conditions could be obtained, under which the free surface fluctuation could be suppressed, and a flow recirculation could rapidly form.

Nonintrusive Method to Compute Water Discharge in Pipes with a Low Depth-to-Diameter Ratio Using Ultrasonic Doppler Velocimetry

AbstractA nonintrusive method to calculate water depth and discharge in partially full pipes using data from a single ultrasonic Doppler velocimeter (UDV) profiler is presented. The position of the free surface is identified from the velocity profiles measured with the UDV. The flow discharge is computed from an approximated parameterization of the velocity field in the cross-section, using a single measured velocity profile. The proposed methodology was applied to steady and unsteady flow conditions in two different pipes with diameters of 90 and 200 mm, and depth-to-diameter ratios up to 0.35. Under these conditions, the water depth and discharge were measured with mean absolute errors of 1 mm and 0.1 L/s in the 90-mm pipe and 0.5 mm and 0.05 L/s in the 200-mm pipe. These errors are almost independent of the discharge.

Two-Dimensional Features of Viscoelastic Models of Pipe Transients

Transients in pressurized polymeric pipes are analyzed by means of a two-dimensional (2D) Kelvin-Voigt viscoelastic model, calibrated by means of a microgenetic algorithm on the basis of pressure traces. The reliability of the proposed model is then tested by comparing numerical and experimental profiles of the axial component of the local velocity, the latter measured by means of an ultrasonic Doppler velocimeter. Differences between transients in viscoelastic and elastic pipes are pointed out by considering a 2D model in which an elastic behavior is assumed for pipe material. The comparison between the two 2D models allows attribution of the faster decay of pressure oscillations and velocity profiles to viscoelasticity because of the time-shift between pressure oscillation and retarded circumferential strain. The 2D analysis shows that the viscoelastic model generally presents flatter velocity profiles with respect to the elastic model.

Application of the ultrasonic doppler velocimeter for study the flow and solidification processes in an electrically conducting fluid

Application of the ultrasonic doppler velocimeter for study the flow and solidification processes in an electrically conducting fluid

Physical Simulation on the Liquid Metal Flow in FC-Mold of Slab Continuous Casting

The flow state and velocity distribution of liquid metal in the FC-Mold and the influence rules by the magnetic flux density have been investigated when electromagnetic brake adopted, applying mercury as medium to simulate molten steel in the continuous casting process. The velocity measurement has been completed by the Ultrasonic Doppler Velocimeter (UDV) under various magnetic distribution and the influence laws of magnetic flux density on the liquid metal flow in the mold has been analyzed. The experimental results indicate that, when the upper and lower magnetic flux density is 0.18T and 0.5T respectively, a preferable control effect can be obtained, not only the free surface fluctuation can be compressed, but also a plug flow can be rapidly formed.

Thixotropy, yielding and ultrasonic Doppler velocimetry in pulp fibre suspensions

This paper reports thixotropy in concentrated pulp fibre suspensions and studies their transient flow behaviour using conventional rheometry coupled with a velocimetry technique. Specifically, an ultrasonic Doppler velocimeter is used in conjunction with a rate-controlled rheometer to deduce the local velocity profiles of pulp fibre suspensions. Pulp suspensions are found to exhibit a plateau in their flow curves where a slight increase in the shear stress generates a jump in the corresponding shear rate, implying the occurrence of shear banding. The velocity profiles were found to be discontinuous in the vicinity of the yielding radius where the Herschel–Bulkley model failed to predict the flow. Shear history and the time of rest prior to the measurement were found to play a significant role on the rheology and the local velocity profiles of pulp suspensions.

A method and instrument to measure the ultrasonic velocity coefficient

The ultrasonic Doppler velocimeter (UDV) is a multifunctional instrument to measure flow velocity by means of the ultrasonic Doppler effect. The instrument is widely used in scientific research and engineering practice for the study of hydraulic systems. It has the advantages of a simple structure and wide applicability and is convenient for field use.

Comparison of Standard k-ε Model and RSM on Three Dimensional Turbulent Flow in the SEN of Slab Continuous Caster Controlled by Slide Gate

The fluid flow in the SEN and its outflow characteristic at nozzle port, after installation of slide gate system to control molten steel flow rate, have been investigated by mathematical simulation using standard k-ε model, RSM and experimental measurement by Ultrasonic Doppler Velocimeter (UDV) respectively, and the adaptability of turbulence models has been discussed. The research results indicate that, due to the throttle action of slide gate, a secondary flow and a separated flow are generated under the slide gate, and a swirl flow appears at nozzle port, with the swirl direction from the clogging side via nozzle bottom to the opening side of the slide gate. The swirl direction of outflow at nozzle port calculated by standard k-ε model is contrary to the measurement result by UDV and, the calculated result obtained by RSM is close to the UDV data. Based on kinetic theory of molecular, theoretical deficiencies of the Boussinesq hypothesis has been discussed.

Optimization of Quench Tank Structure Based on CFD Simulation

In order to investigate the flow rate distribution and improve the flow rate uniformity of the quenchant in a quench tank, the ultrasonic Doppler velocimeter (UDV) was used to measure the flow rate of quenchant with agitation, and then a computational fluid dynamics (CFD) simulation was carried out to simulate the flow rate distribution without / with flow baffles. According to the CFD simulation results, the structures and positions of flow baffles in the draft-tube were optimized to obtain the uniform flow rate distribution in the quench zone, which were verified by experiments as well. The simulation and experimental results show that the UDV is suitable for measuring the flow rate of a large-size quench tank. This research provided a solid foundation for optimizing the structure design of flow baffles in production quench tanks.

Inline ultrasonic rheometry by pulsed Doppler

This will be a discussion of the non-invasive determination of the viscosity of a non-Newtonian fluid in laminar pipe flow over the range of shear rates present in the pipe. The procedure used requires knowledge of the flow profile in and the pressure drop along a long straight run of pipe. The profile is determined by using a pulsed ultrasonic Doppler velocimeter. This approach is ideal for making non-invasive, real-time measurements for monitoring and control. Rheograms of a shear thinning gel will be presented. The operating parameters and limitations of the Doppler-based instrument will be discussed. The most significant limitation is velocity gradient broadening of the Doppler spectra near the walls of the pipe. This limitation can be significant for strongly shear thinning fluids (depending also on the ratio of beam to pipe diameter and the transducer’s insertion angle).

Time-mean structure of secondary flows in open channel with longitudinal bedforms

Secondary motions are commonly present in open channel flows. This study aims to investigate, both experimentally and analytically, time-mean characteristics of cellular secondary flows generated by longitudinal bedforms. Experiments were conducted in a tilting, rectangular flume with six different longitudinal bedforms, including alternate bed strips with different roughness heights and bed ridges of wavy and rectangular shapes. Various flows were sampled using a two-dimensional laser Doppler anemometer (LDA) and a one-dimensional ultrasonic Doppler velocimeter (UDV). Experimental results demonstrate secondary flows appearing basically in cellular fashion over the modeled longitudinal bedforms. It is also shown that the cellular structures can be described analytically with kinematic considerations. The discrepancies between theoretical and measurement results are discussed. An empirical relationship between maximum vertical velocity and bed configuration is finally proposed based on the experimental data.

Improvement of the flow rate distribution in quench tank by measurement and computer simulation

In order to investigate the flow rate distribution and improve the flow rate uniformity of the quenchant in a quench tank, the ultrasonic Doppler velocimeter (UDV) was adopted to measure the flow rate of quenchant with agitation, and then computational fluid dynamics (CFD) simulation had been carried out to simulate the flow rate distribution without/with flow baffles. According to the CFD simulation results, the structure and positions of flow baffles in the draft-tube were optimized to obtain the uniformity of flow rate in the quench zone, which were verified by experiments as well. The simulation and measurement results show that the UDV is suitable for measuring the flow rate of a large size quench tank. This research will provide a foundation for optimizing the structure design of flow baffles in production quench tanks.