Johan Wiklund

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.

Flow-Viz — An integrated digital in-line fluid characterization system for industrial applications

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.

In-line Measurements of Rheological Properties of Cement-Based Grouts -Introducing the UVP+PD Method

In-line measurements of rheological properties of cement-based grouts : Introducing the UVP-PD method

Shear and extensional rheology of commercial thickeners used for dysphagia management

People who suffer from swallowing disorders, commonly referred to as dysphagia, are often restricted to a texture-modified diet. In such a diet, the texture of the fluid is modified mainly by the addition of gum or starch-based thickeners. For optimal modification of the texture, tunable rheological parameters are shear viscosity, yield stress, and elasticity. In this work, the flow properties of commercial thickeners obtained from major commercial suppliers were measured both in shear and extensional flow using a laboratory viscometer and a newly developed tube viscometry technique, termed Pulsed Ultrasound Velocimetry plus Pressure Drop (PUV + PD). The two methods gave similar results, demonstrating that the PUV + PD technique can be applied to study flow during the swallowing process in geometry similar to that of the swallowing tract. The thickeners were characterized in relation to extensional viscosity using the Hyperbolic Contraction Flow method, with microscopy used as a complementary method for visualization of the fluid structure. The gum-based thickeners had significantly higher extensional viscosities than the starch-based thickeners. The rheological behavior was manifested in the microstructure as a hydrocolloid network with dimensions in the nanometer range for the gum-based thickeners. The starch-based thickeners displayed a granular structure in the micrometer range. In addition, the commercial thickeners were compared to model fluids (Boger, Newtonian, and Shear-thinning) set to equal shear viscosity at 50/s and it was demonstrated that their rheological behavior could be tuned between highly elastic, extension-thickening to Newtonian. PRACTICAL APPLICATIONS Thickeners available for dysphagia management were characterized for extensional viscosity to improve the understanding of these thickeners in large scale deformation. Extensional deformation behavior was further explained by using microcopy as corresponding technique for better understanding of structure/rheology relationship. Moreover, the major challenge in capturing human swallowing process is the short transit times of the bolus flow (<1 s). Therefore, the ultrasound-based rheometry method; PUV+PD which measures the real-time flow curve in ∼50 ms was used in addition to classical shear rheometry. The two methods complimented each other indicating that the PUV+PD method can be applied to study the transient swallowing process which is part of our future research, where we are studying the flow properties of fluids in an in vitro swallowing tract.

Characterization of acoustic beam propagation through high-grade stainless steel pipes for improved pulsed ultrasound velocimetry measurements in complex industrial fluids

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.

Embedded system for in-line ultrasound velocity profile detection

The in-line assessment of the rheological properties of fluids is fundamental for the production process optimization and for ensuring a high product quality in chemical, cosmetic, pharmaceutical, and food industries. The rheology of a fluid flowing in a pipe can be investigated through the combination of Pressure Difference (PD) and Pulsed Ultrasound Velocimetry (PUV) methods. In particular PUV is a non-invasive Doppler technique capable of measuring the velocity profile, i.e. the radial velocity distribution of the fluid. Till now, few PUV systems are available to industries, and they are often minimal acquisition cards connected to computers where the flow velocity distribution is calculated in post-processing. In this work, a complete PUV system for in-line measurement, is presented. It includes the analog electronics required for the ultrasound frontend and the digital devices for the on-board calculation of the velocity profile. The system, currently integrated in the Flow-Viz platform (SP, Sweden), is fully programmable, suitable for industrial applications, and capable of producing, in real time 45 profiles per second.

Ultrasound Doppler measurements inside a diaphragm valve using novel transducer technologies

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.

Real-time staggered PRF for in-line industrial fluids characterization

The rheology of a fluid flowing in an industrial pipe can be assessed by combining the pressure drop and the fluid velocity profile, which can be obtained non-invasively through a Pulsed Wave Doppler (PWD) ultrasound investigation. In PWD, the maximum detectable velocity is related to the Pulse Repetition Frequency (PRF), which, in turn, is limited by the maximum investigation depth. Unfortunately, high flow-rates flowing in large industrial pipes produce Doppler frequencies that easily exceed the Nyquist limit, thus resulting in aliased, corrupted measurements. Staggered PRF is a known technique that allows an extension of the Nyquist limit. The de-aliased velocity is recovered by combining the aliased velocities measured from different PRFs, generated with specific ratios. In this work, we extend the capabilities of an embedded ultrasound system for rheological characterization of industrial fluids (doi: 10.1109/ULTSYM.2015.0273) by implementing, in real-time, the staggered PRF method.

Real-Time in-Line Industrial Fluids Characterization Using Multiple Pulse Repetition Frequency

The characterization of fluids flowing in industrial pipes is of paramount importance to optimize the production process and guarantee the final product quality in most industries. Rheological parameters of the fluid can be efficiently calculated starting from the Pressure Drop (PD) along a tract of the pipe, and the velocity profile that the flow develops along the pipe diameter, which can be assessed through Ultrasounds Pulsed Wave Doppler (PWD). Unfortunately, in PWD the maximum detectable velocity is restricted by the aliasing limit related to the Pulse Repetition Frequency (PRF). The use of PRF sequences at different rate can recover de-aliased velocities by combining the aliased data. In this work, we extend the capabilities of an embedded PWD ultrasound system used to characterize industrial fluids by implementing, in real-time, the multi-PRF method.

Embedded System for In-Line Characterization of Industrial Fluids

The in-line assessment of the rheological properties of fluids in chemical, cosmetic, pharmaceutical, and food industries is fundamental for process optimization and product quality. The rheology of a fluid in a process pipe can be investigated by combining the measured pressure difference over a fixed distance of pipe, and the velocity distribution of the fluid along the diameter. The latter data can be measured by Pulsed Ultrasound Velocimetry (PUV), which is a non-invasive Doppler technique. Till now, the few systems available need cumbersome electronics or computer for data post-processing and are not suitable for industrial applications. In this work we present a compact (10 × 12 cm), fully programmable and low cost system that embeds the ultrasound front-end and all of the digital electronics necessary for the signal processing. The board produces, in real time, 512-point velocity profiles at 45 Hz rate and is integrated in the Flow-VizTM platform (SP Technical Research Institute of Sweden).