The Ultrasound Velocity Profiling (UVP) technique allows real-time, non-invasive flow mapping of a fluid along a 1D-measuring line. This study explores the possibility of using the UVP technique and X-ray video-fluoroscopy (XVF) to elucidate the deglutition process with the focus on bolus rheology. By positioning the UVP probe so that the pulsed ultrasonic beam passes behind the air-filled trachea, the bolus flow in the pharynx can be measured. Healthy subjects in a clinical study swallowed fluids with different rheological properties: Newtonian (constant shear viscosity and non-elastic); Boger (constant shear viscosity and elastic); and shear thinning (shear rate-dependent shear viscosity and elastic). The results from both the UVP and XVF reveal higher velocities for the shear thinning fluid, followed by the Boger and the Newtonian fluids, demonstrating that the UVP method has equivalent sensitivities for detecting the velocities of fluids with different rheological properties. The velocity of the contraction wave that clears the pharynx was measured in the UVP and found to be independent of bolus rheology. The results show that UVP not only assesses accurately the fluid velocity in a bolus flow, but it can also monitor the structural changes that take place in response to a bolus flow, with the added advantage of being a completely non-invasive technique that does not require the introduction of contrast media. © 2020, The Author(s).

The pharynx is critical for correct swallowing, facilitating the transport of both air and food transport in a highly coordinated manner, and aberrant co-ordination causes swallowing disorders (dysphagia). In this work, an in vitro model of swallowing was designed to investigate the role of rheology in swallowing and for use as a pre-clinical tool for simulation of different routes to dysphagia. The model is based on the geometry of the human pharynx. Manometry is used for pressure measurements and ultrasonic analysis is performed to analyze the flow profiles and determine shear rate in the bolus, the latter being vital information largely missing in literature. In the fully automated model, bolus injection, epiglottis/nasopharynx movement, and ultrasound transducer positioning can be controlled. Simulation of closing of the airways and nasal cavity is modulated by the software, as is a clamping valve that simulates the upper esophageal sphincter. The actions can be timed and valves opened to different degrees, resembling pathologic swallowing conditions. To validate measurements of the velocity profile and manometry, continuous and bolus flow was performed. The respective velocity profiles demonstrated the accuracy and validity of the flow characterization necessary for determining bolus flow. A maximum bolus shear rate of 80 s−1 was noted for syrup-consistency fluids. Similarly, the manometry data acquired compared very well with clinical studies.

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.

Human swallowing taking place in the pharynx is a complex process demanding precise co-ordination amongst the organs involved. People suffering from swallowing disorders are restricted to texture altered foods/drinks which are shear thinning necessitating the knowledge of shear deformation during pharyngeal transport. In this work, the shear rate during bolus transport using shear thinning boluses was measured and reported both during in-vivo and in-vitro experiments.

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).

The rheology of a fluid flowing in an industrial process pipe can be calculated by combining the pressure drop and the velocity profile that the fluid develops across the tube diameter. The profile is obtained noninvasively through an ultrasound Doppler investigation. Unfortunately, at present, no system capable of real-time velocity profile assessment is available for in-line industrial rheological measurements, and tests are operated by manually moving fluid specimens to specialized laboratories. In this work, we present an embedded system capable of in-line and real-time measurement of velocity profile and pressure drop, which enables the automatic rheological characterization of non-Newtonian fluids in process pipes. The system includes all the electronics for the ultrasound front-end, as well as the digital devices for the real-time calculation of the velocity profile. The proposed system is highly programmable, low-noise, and specifically targeted for industrial use. It is shown capable of producing, for example, 512-point velocity profiles at 45 Hz rate. An application is presented where a sludge fluid, flowing at 600 L/min in a 48 mm diameter high-grade stainless steel pipe, is characterized in real-time with a ±5% accuracy.

In construction, grouting is used to improve or alter the natural properties of soil or rock by injecting a grout into the pores or fractures of the formation. In order to predict the grout penetration progress and maximum penetration length, modern methods for grouting design involve a detailed knowledge of the rheological properties of the used grout. Today, rheological properties of grouts are measured either in a laboratory with conventional rheometers or in the field with simple devices. Due to the complex flow behavior of cement-based grouts, being non-Newtonian yield stress fluids with history and time dependent rheological properties, the results are non-consistent, device dependent and strongly influenced by the test procedure and operator. No standard measurement method is available for rheological characterization of grouts in the grouting industry today. In order to improve this unfortunate situation a new complete measuring methodology, based on pulsed ultrasound, is proposed. The method has been tested for cement-based grouts, with good results. In this work, a new container-based field laboratory is presented, equipped with the Flow-Viz system, which is designed for in-line measurements of rheological properties of cement-based grouts under field-like conditions. Results obtained under field-like conditions are presented in order to demonstrate the applicability of the new system.

Modern industries need to monitor every step of the production process for a better efficiency and product quality. However, important parameters, like the rheological indexes of the fluids involved in the process, cannot easily be inspected inline, as they are typically analyzed through off-line laboratory tests on specimens. Recently, electronics sensors have been introduced capable to characterize in-line the fluids by acquiring the velocity profile of the fluid flowing in a pipe, and the pressure drop. These sensors are based on Pulsed Wave Doppler (PWD), where ultrasound energy bursts are transmitted at Pulse Repetition Frequency (PRF) rate. The fluid maximum velocity that can be safely investigated in PWD is constrained by the PRF, which is limited by the investigation depth. Unfortunately, in large industrial pipes, the fluid velocity can be easily beyond the Nyquist limit, preventing a correct ultrasound investigation. Staggered PRF is a technique typically used in Doppler radar that, by exploiting PRF sequences at different rate, can recover the right velocity even if beyond the Nyquist limit. In this work, an embedded ultrasound system for in-line rheological investigation is updated by implementing in its Field Programmable Gate Array (FPGA) the staggered PRF technique. Experiments show the system capable of detecting velocity profiles at 25 Hz rate beyond the Nyquist limit.

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 (HCF) 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 50s−1 and it was demonstrated that their rheological behavior could be tuned between highly elastic, extension-thickening to Newtonian. This article is protected by copyright. All rights reserved.

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.