| 1. |
- Kotze, Reinhardt, et al.
(author)
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Application of an in-line flow visualisation technique based on ultrasonics for paste and thickened tailings
- 2014
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In: BHR Group - 19th International Conference on Hydrotransport 2014. - : BHR Group Limited. - 9781634394444 ; , s. 407-420
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Conference paper (peer-reviewed)abstract
- Ultrasonic velocity profiling (UVP) is a technique that can measure an instantaneous one-dimensional velocity profile in a fluid containing particles across the ultrasonic beam axis or measurement line. A methodology for in-line rheometry combining the UVP technique with pressure difference (PD) measurements, commonly known as UVP+PD, has been developed and improved at the Swedish Institute for Food and Biotechnology and the Cape Peninsula University of Technology (Wiklund, (1); Wiklund et al., (2); Kotzć et al., (3)). The UVP+PD methodology allows measurements that are not possible with common rheometers such as radial velocity profiles and yield stress directly in-line and under true dynamic process conditions. Furthermore, it has advantages over commercially available process rheometers and off-line instruments in being noninvasive, applicable to opaque and concentrated suspensions and having small sensor dimensions. It has been evaluated for several potential industrial applications including, for example, paper pulp, foods, transient flows and model mineral suspensions. Similarly, the UVP technique can be applied to open channel flow by combining flow depth measurements in order to obtain rheological properties in-line. Industrial fluids, such as thickened paste etc., commonly found in tailings transportation exhibit wide particle size distributions, large particle sizes and very high viscosities. These industrial fluids cause strong attenuation of the ultrasound energy, which can significantly distort velocity profiles measured with the UVP technique or even make it impossible to conduct flow measurements at all with optical techniques. Initial results obtained in concentrated cement pastes and grouts as well as bentonite showed that UVP is a feasible and promising technique for flow visualisation and rheological characterisation in complex fluids. The results obtained showed significant potential for application in more viscous fluids and larger pipe diameters using new transducers and acoustic coupling technologies.
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| 2. |
- Kotzé, Reinhardt, et al.
(author)
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Application of ultrasound Doppler technique for in-line rheological characterization and flow visualization of concentrated suspensions
- 2016
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In: Canadian Journal of Chemical Engineering. - : Wiley-Liss Inc.. - 0008-4034 .- 1939-019X. ; 94:6, s. 1066-1075
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Journal article (peer-reviewed)abstract
- Ultrasonic velocity profiling (UVP) is a technique that can measure an instantaneous one-dimensional velocity profile in a fluid containing particles across the ultrasonic beam axis or measurement line. A method for in-line rheometry combining the UVP technique with pressure difference (PD) measurements (UVP+PD), was developed and improved at SP - Technical Research Institute of Sweden and the Cape Peninsula University of Technology, South Africa. The UVP+PD methodology allows measurements that are not possible with common rheometers such as radial velocity profiles and yield stress directly in-line and under true dynamic process conditions. Furthermore, it has advantages over commercially available process rheometers and offline instruments in being non-invasive, applicable to opaque and concentrated suspensions, and having small sensor dimensions. It has been evaluated for several potential industrial applications including paper pulp, foods, transient flows, and model mineral suspensions. Similarly, the UVP technique can be applied to an open-channel flow by combining flow depth measurements to obtain rheological properties in-line. Industrial fluids, such as thickened pastes, commonly found in tailings transportation exhibit wide particle size distributions, large particle sizes, and very high viscosities. These industrial fluids cause strong attenuation of the ultrasound energy, which can significantly distort velocity profiles measured with the UVP technique or even make it impossible to conduct flow measurements. Initial results obtained in concentrated cement pastes and grouts (bentonite and kaolin clay) showed that UVP is a feasible and promising technique for flow characterization in viscous fluids.
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| 3. |
- Kotze, Reinhardt, et al.
(author)
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Commissioning of a novel in-line rheometery system in a wastewater treatment plant for more efficient polymer dosing
- 2019
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In: Flow Measurement and Instrumentation. - : Elsevier BV. - 0955-5986 .- 1873-6998. ; 65, s. 309-317
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Journal article (peer-reviewed)abstract
- Urbanisation is putting enormous pressure on wastewater treatment plant facilities. Optimising the liquid and sludge process streams in existing plants is one way of prolonging the life span of such installations. Many Wastewater treatment plants (WWTP) have sludge dewatering installations where treated wastewater sludge is dewatered using belt filter presses amongst others, before final disposal. One of the most expensive inputs in these plants is the polymers used as flocculants. Controlling the optimum dosing in the dewatering process cannot currently be done in real-time. It has been shown that huge savings can be made by optimising the dosing rates of polymers based on the sludge rheology. An Ultrasound Velocity Profiling (UVP) and pressure drop (PD) measurement system was specially designed and commissioned for a WWTP. The system was installed in a WWTP to measure the rheological properties of sludge in-line and in real-time prior to mechanical dewatering using a belt filter press. This non-invasive in-line system was able to accurately measure the rheological parameters in real-time in a 100 mm stainless pipe. It was shown for the first time what the maximum in-line yield stress is that is required for optimum dewatering based on a relationship determined between the yield stress and the total suspended solids in the filtrate exiting the belt filter press.
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| 4. |
- Kotze, Reinhardt, et al.
(author)
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Optimisation of Pulsed Ultrasonic Velocimetry system and transducer technology for industrial applications
- 2013
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In: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 53:2, s. 459-469
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Journal article (peer-reviewed)abstract
- 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 52.8 mm). 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.
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| 5. |
- Kotze, Reinhardt, et al.
(author)
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Optimization of the UVP+PD rheometric method for flow behavior monitoring of industrial fluid suspensions
- 2012
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In: Applied Rheology. - 1430-6395 .- 1617-8106. ; 22:4, s. 2-
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Journal article (peer-reviewed)abstract
- 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, relatively easy to implement and applicable to opaque fluid suspensions, which are frequently found in industry. UVP can also be combined with Pressure Drop (PD) measurements in order to obtain rheological parameters of non-Newtonian fluids by fitting theoretical rheological models to a single velocity profile measurement. The flow properties of complex fluids are almost exclusively obtained today using commercially available instruments, such as conventional rotational rheometers or tube (capillary) viscometers. Since these methods are time-consuming and unsuitable for real-time process monitoring, the UVP+PD methodology becomes a very attractive alternative for in-line flow behavior monitoring as well as quality control in industrial applications. However, the accuracy of the UVP+PD methodology is highly dependent on the shape and magnitude of the measured velocity profiles and there are still a few problems remaining with current instrumentation and methods in order to achieve the robustness and accuracy required in industrial applications. The main objective of this research work was to optimize an UVP+PD system by implementing new transducer technology and signal processing techniques for more accurate velocity profile measurements as well as rheological characterization of complex fluids under industrial/realistic conditions. The new methodology was evaluated in two different pipe diameters (22.5 and 52.8mm) and tested with three different non-Newtonian fluids in order to obtain a wide range of rheological parameters. Results were also compared to conventional rotational rheometry and tube viscometry. It was found that rheological parameters obtained from accurate velocity data across the pipe radius, especially close to pipe walls where the velocity gradient is high, showed better agreement to conventional rheometry than when compared to results obtained using profiles measured with conventional UVP instrumentation and commercial software (Met-Flow SA Version 3.0). The UVP+PD method is now more robust and accurate. The main challenge remaining is to successfully implement a complete non-invasive system in industrial processes that is able to achieve real-time and accurate complex flow monitoring of non-Newtonian fluid suspensions.
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| 6. |
- Kotzé, Reinhardt, et al.
(author)
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Performance tests of a new non-invasive sensor unit and ultrasound electronics
- 2016
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In: Flow Measurement and Instrumentation. - : Elsevier Ltd. - 0955-5986 .- 1873-6998. ; 48, s. 104-111
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Journal article (peer-reviewed)abstract
- Industrial applications involving pulsed ultrasound instrumentation require complete non-invasive setups due to high temperatures, pressures and possible abrasive fluids. Recently, new pulser-receiver electronics and a new sensor unit were developed by Flow-Viz. The complete sensor unit setup enables non-invasive Doppler measurements through high grade stainless steel. In this work a non-invasive sensor unit developed for one inch pipes (22.5 mm ID) and two inch pipes (48.4 mm ID) were evaluated. Performance tests were conducted using a Doppler string phantom setup and the Doppler velocity results were compared to the moving string target velocities. Eight different positions along the pipe internal diameter (22.5 mm) were investigated and at each position six speeds (0.1-0.6 m/s) were tested. Error differences ranged from 0.18 to 7.8% for the tested velocity range. The average accuracy of Doppler measurements for the 22.5 mm sensor unit decreased slightly from 1.3 to 2.3% across the ultrasound beam axis. Eleven positions were tested along the diameter of the 48.4 mm pipe (eight positions covered the pipe radius) and five speeds were tested (0.2-0.6 m/s). The average accuracy of Doppler measurements for the 48.4 mm sensor unit was between 2.4 and 5.9%, with the lowest accuracy at the point furthest away from the sensor unit. Error differences varied between 0.07 and 11.85% for the tested velocity range, where mostly overestimated velocities were recorded. This systematic error explains the higher average error difference percentage when comparing the 48.4 mm (2.4-5.9%) and 22.5 mm (1.3-2.3%) sensor unit performance. The overall performance of the combined Flow-Viz system (electronics, software, sensor) was excellent as similar or higher errors were typically reported in the medical field. This study has for the first time validated non-invasive Doppler measurements through high grade stainless steel pipes by using an advanced string phantom setup.
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| 7. |
- Kotze, Reinhardt, et al.
(author)
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Ultrasound Doppler measurements inside a diaphragm valve using novel transducer technologies
- 2014
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In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:10, s. 105302-
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Journal article (peer-reviewed)abstract
- In this project, velocity profiles were measured in a diaphragm valve using an ultrasonic velocity profiling (UVP) technique. A non-Newtonian CMC model fluid was tested in this highly complex geometry and velocity profiles were measured at four different positions at the centre (contraction) of a specially manufactured 50% open diaphragm valve. The coordinates of the complex geometry and velocity magnitudes were analysed and compared to the bulk flow rate measured using an electromagnetic flow meter. Two different ultrasonic transducers (standard and delay line) were used and results were compared in order to assess velocity data close to wall interfaces as well as the accuracy and magnitude of measured velocities. The difference between calculated and measured flow rates was 32% when using the standard ultrasonic transducers. The error difference decreased to 18% when delay line transducers were introduced to the measurements. The velocity data obtained in the diaphragm valve showed a significant improvement close to the wall interfaces when using the delay line transducers. The main limitation when using delay line transducers is that beam refraction can significantly complicate measurements in a highly complex geometry such as a diaphragm valve. A new delay line transducer with no beam refraction could provide a solution. The introduction of delay line transducers showed that UVP can be used as a powerful tool for detailed flow behaviour measurements in complex geometries.
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| 8. |
- Meacci, Valentino, et al.
(author)
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Flow-Viz - An integrated digital in-line fluid characterization system for industrial applications
- 2016
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In: 2016 IEEE Sensors Applications Symposium (SAS). - 9781479972500 ; , s. 128-133
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Conference paper (peer-reviewed)abstract
- The continuous monitoring of rheological parameters of industrial fluids during production is of paramount importance for process and quality control. Up to now, no system capable of a complete and non-invasive in-line measurement is commercially available, so that only time discrete laboratory measurements on fluids specimens are possible. In this work a new, fully integrated ultrasound system for in-line fluid characterization, named Flow-Viz, is presented. The system measures the velocity profile of the fluid moving in a pipe through pulsed Doppler ultrasound, and combines it with the pressure drop. The electronics, featuring two ultrasound transmission/reception channels used alone or in pitch-catch configuration, includes powerful digital processing capabilities for real-time velocity profile calculation, and is fully programmable. Particular attention is paid to low-noise design for achieving the optimal performance in highly attenuating suspensions. An application is presented where the system, coupled to a non-invasive ultrasound sensor unit, performs in-line rheological measurements through the wall of a high-grade stainless steel pipe.
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| 9. |
- Rahman, Mashuqur, 1984-, et al.
(author)
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Yield stress of cement grouts
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Other publication (other academic/artistic)abstract
- : The rheology of cement grout is complex due to its thixotropic nature and the presence of a yield stress. Despite the importance of the yield stress for grouting design, no standard methods are yet available to determine the yield stress. Most common methods are based on using conventional rheometers, but the results are subjective due to the measurement techniques, applied shear history and hydration. In this work, measurement of the yield stress of cement grout was performed with different measurement techniques using a conventional rheometer. In addition, in-line measurements using an ultrasound based technique were made in order to visualize the flow profile and perform a direct measurement of the yield stress. Two ranges of yield stress, static and dynamic yield stress, were measured. These results should be used for design purposes depending on the prevailing shear rate. The ultrasound based Flow Viz industrial rheometer was found capable of performing direct in-line measurement of the yield stress and providing a detailed visualization of the velocity profile of cement grout.
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| 10. |
- Rahman, Mashuqur, et al.
(author)
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Yield stress of cement grouts
- 2017
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In: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 61, s. 50-60
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Journal article (peer-reviewed)abstract
- The rheology of cement grout is complex due to its thixotropic nature and the presence of a yield stress. Despite the importance of the yield stress for grouting design, no standard methods are yet available to determine the yield stress. Most common methods are based on using conventional rheometers, but the results are subjective due to the measurement techniques, applied shear history and hydration. In this work, measurement of the yield stress of cement grout was performed with different measurement techniques using a conventional rheometer. In addition, in-line measurements using an ultrasound based technique were made in order to visualize the flow profile and perform a direct measurement of the yield stress. Two ranges of yield stress, static and dynamic yield stress, were measured. These results should be used for design purposes depending on the prevailing shear rate. The ultrasound based Flow Viz industrial rheometer was found capable of performing direct in-line measurement of the yield stress and providing a detailed visualization of the velocity profile of cement grout.
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| 11. |
- Shamu, John, et al.
(author)
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Characterization of acoustic beam propagation through high-grade stainless steel pipes for improved pulsed ultrasound velocimetry measurements in complex industrial fluids
- 2016
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In: IEEE Sensors Journal. - New Jersey. - 1530-437X .- 1558-1748. ; 16:14, s. 5636-5647
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Journal article (peer-reviewed)abstract
- The newly developed Flow-Viz rheometric system is capable of performing detailed non-invasive velocimetry measurements through industrial stainless steel pipes. However, in order to improve the current design for non-invasive measurements in industrial fluids, pulsed ultrasound sensors need to be acoustically characterized. In this paper, acoustic characterization tests were carried out, with the aim of measuring the ultrasound beam propagation through stainless steel (SS316L) pipes and into water. For these tests, a high-precision robotic XYZ-scanner and needle hydrophone setup was used. Several ultrasound sensor configurations were mounted onto stainless steel pipes, while using different coupling media between the transducer-to-wedge and sensor wedge-to-pipe boundaries. The ultrasound beam propagation after the wall interface was measured by using a planar measuring technique along the beam's focal axis. By using this technique, the output for each test was a 2-D acoustic color map detailing the acoustic intensity of the ultrasound beam. Measured beam properties depicted critical parameters, such as the start distance of the focal zone, focal zone length, Doppler angle, and peak energy within the focal zone. Variations in the measured beam properties were highly dependent on the acoustic couplants used at the different interfaces within the sensor unit. Complete non-invasive Doppler ultrasound sensor technology was for the first time acoustically characterized through industrial grade stainless steel. This information will now be used to further optimize the non-invasive technology for advanced industrial applications.
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| 12. |
- Shamu, John, 1990-, et al.
(author)
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Radial Flow Velocity Profiles of a Yield Stress Fluid between Smooth Parallel Disks
- 2020
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In: Rheologica Acta. - : Springer Science and Business Media LLC. - 0035-4511 .- 1435-1528.
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Journal article (peer-reviewed)abstract
- In rock grouting, idealized 2D-radial laminar flow of yield stress fluids (YSF) is a fundamental flow configuration that is used for cement grout spread estimation. A limited amount of works have presented analytical and numerical solutions on the radial velocity profiles between parallel disks. However, to the best of our knowledge, there has been no experimental work that has presented measured velocity profiles for this geometry. In this paper, we present velocity profiles of Carbopol (a simple YSF), measured by pulsed ultrasound velocimetry within a radial flow model. We describe the design of the physical model and then present the measured velocity profiles while highlighting the plug-flow region and slip effects observed for three different apertures and volumetric flow rates. Although the measured velocity profiles exhibited wall slip, there was a reasonably good agreement with the analytical solution. We then discuss the major implications of our work on radial flow.
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