Flow Measurements Research Articles

A novel method of reconstructing planar flow field from given distribution of single velocity component: comparison to conventional divergence-free approach

Measurements of a single flow velocity component are still prevalent due to their reasonable costs and some difficulties in multiple-component measurements. If the transverse component can be obtained additionally by a numerical technique, qualitative features of the flow will be understood more effectively. In this context, methods based on the 2-dimensonal divergence-free assumption have been widely used for problems in which a single velocity component is measured over a planar domain. In this study, the authors proposed a method of approximating the second planar velocity component by minimising an objective function expressed with divergence and vorticity so that the mass transport in the out-of-plane direction could be taken into consideration. The present method was tested with numerically produced 3-dimensional flows in a hexahedral chamber and a flow around a bluff body measured by particle image velocimetry. There was a tendency that the present method calculated the second velocity component with smaller errors than existing divergence-free approaches. It was also shown that the present method had a high capability to locate strong suction and generation caused by the mass transport in the out-of-plane direction. The present method is deemed promising for many one-component flow measurements in engineering and medicine.

The Role of Platelets and Aneurysm Thrombus in the EVAR Post Implantation Syndrome

ObjectivePost implantation syndrome (PIS) is a well-defined entity with unclear etiology, complicating a number of patients with AAAs treated with EVAR. The aim of this study was to assess the platelets’ role and the influence of aneurysmal sac thrombus volumes in the development of PIS. DesignA retrospective analysis of prospectively collected data was performed and 76 patients that were treated by EVAR (2011-2013) were studied. Aneurysms with endoleak were not included in the study. Based on the criteria for SIRS (Systemic Inflammatory Response Syndrome), 17 patients (22%) developed PIS (which is considered a SIRS analogue), while 59 (78%) did not. MethodsThe two groups were compared in relation to the following parameters: baseline platelet count (PLT), decrease of platelet count (PLT drop), volume of the arterial flow before the procedure (V Flow), volume of thrombus of the aneurysm (V thromb), ratio of thrombus volume to aneurysm sac volume (V ratio) and the volume of new formed thrombus (V new). Volume flow measurements were calculated by Osirix ™ software preoperatively and in the 1st month postoperatively. Parametric and non-parametric techniques (unpaired t-test, Mann-Whitney U test) were used accordingly. ResultsBaseline platelets absolute count was greater in the PIS group (239000 ± 17000) vs. the non-PIS group (194000 ± 6900, p=0.004), and the PLT drop was larger in the PIS group (74000 ± 15600 vs. 45000 ± 5300, p=0.019). No difference was found regarding the aneurysm volumes (Vflow, Vthromb, Vratio, Vnew) between the two groups. ConclusionPlatelets, in terms of their absolute baseline count and their decrease after the procedure, seem to be an important factor in developing PIS after EVAR. Further, more tailored studies are needed to elucidate the role of platelets and flow/thrombus volumes in the development of PIS.

Effect of trailing-edge blowing on the acoustic and aerodynamic characteristics of a flatback airfoil

This study investigated the impact of trailing-edge uniform air blowing on the acoustic and aerodynamic characteristics of a flatback airfoil. Near- and far-field pressure fluctuations, surface static pressure distribution, as well as boundary layer and wake flow measurements were conducted to comprehensively understand the effects of the method on both the noise generation mechanism and the aerodynamic characteristics of the airfoil. It was revealed that tonal noise originates from surface pressure fluctuations induced by upstream flow disturbances due to vortex shedding. The application of blowing was found to shift large-scale vortices generated during vortex shedding further downstream, resulting in the suppression of surface pressure fluctuations on both the pressure and suction sides of the airfoil, consequently reducing far-field noise. Additionally, blowing enhanced spanwise coherence at the vortex shedding frequency. In terms of aerodynamic behavior, blowing was shown to increase base pressure, leading to drag reduction without affecting lift. Interestingly, the significant drag reduction was found to occur at the same blowing parameter associated with maximum tonal noise reduction.

Design and implementation of a cost-effective, open-source, and programmable pulsatile flow system

The primary objective of this research was to design, implement, and validate a programmable open-source pulsatile flow system to cost-effectively simulate vascular flows. We employed an Arduino-compatible microcontroller combined with a motor driver to control a centrifugal direct current (DC) motor pump. The system was programmed to produce pulsatile flows with an arterial pulse waveform. Validation with Doppler ultrasound and flow measurements confirmed that our Arduino-based system successfully replicated arterial vascular flow. The materials are easily accessible, with a total bill of materials as low as $99. This open-source programmable pulsatile pump platform offers superior cost-effectiveness and adaptability relative to commercial offerings.

Quantifying and visualizing abdominal hemodynamics in patients with Fontan circulation by 4D phase-contrast flow magnetic resonance imaging at 1.5 T

BackgroundLiver fibrosis has been recognized as a long-term morbidity associated with Fontan circulation (Fontan-associated liver disease, FALD). The pathophysiology of FALD is not completely understood and abnormal flow dynamics may be associated with this condition. Liver hemodynamics can be quantitatively evaluated with four-dimensional phase-contrast flow magnetic resonance imaging (4D PC flow MRI). The study aimed to evaluate suitability of liver 4D PC flow MRI in Fontan patients and relate flow measurements to normal values and FALD severity. Patients and methodsTwenty-two Fontan patients were examined by 4D PC flow MRI at 1.5 Tesla to assess mesenteric, portal, splenic, and hepatic venous blood flow. Severity of FALD was graded based on routine screening, including abdominal ultrasound and laboratory tests. ResultsMedian age was 18.5 (interquartile range, IQR 15.5–20.2) years. FALD was graded as “none or mild” in 16 and as “moderate to severe” in six cases. Ten patients presented at least one feature of portal hypertension (ascites, splenomegaly, or thrombocytopenia). For the entire cohort, blood flow in the superior mesenteric, splenic, and portal vein was lower than reported in the literature. No significant differences were observed in relation to FALD severity. Features of portal hypertension were associated with a higher splenic vein blood flow (0.34 ± 0.17 vs. 0.20 ± 0.07 l/min, p = 0.046). Splenic vein blood flow was negatively correlated to platelet count (r = −0.590, p = 0.005). Conclusions4D PC flow MRI appears suitable to assess liver hemodynamics in Fontan patients and integration into clinical follow-up might help to improve our understanding of FALD.

An exploratory study on bamboo permeability for evaluation of treatability with chemical solutions

The rapid and uniform impregnation of resins and preservative fluids is critical to improving the quality and durability of wood-based materials. Permeability coefficients obtained in laboratory experiments aid in the development of optimal conditions for uniform resin filling on an industrial scale. However, due to the shape and orientation of pores in the bulk structure of bamboo, simplified permeability equations may not be sufficient to provide realistic resin impregnation predictions. In this study, the permeability coefficients for Dendrocalamus asper bamboo were determined using air flow measurements and Forchheimer's equation in the x, y, and z directions, and they were correlated to the bamboo microstructure, providing a detailed perspective on how to further investigate this property for real-world applications, such as pressure treatments with chemical solutions. Porosity was measured using mercury intrusion porosimetry (MIP) and water immersion methods to aid in the permeability analysis. The results showed that the longitudinal direction had 1000 to 10,000 times higher permeability coefficients than the radial and tangential directions. This finding is consistent with the alignment of transport vessels as well as the limited pore network in the transversal bamboo section. The outer region of bamboo had higher radial permeability than the middle and inner layers, despite having lower porosity. It is hypothesized that the greater number of vessels, albeit smaller, provides a more direct path for air to flow. The Darcian permeability coefficients of bamboo were found to be comparable to those reported in the literature for wood. This exploratory study provided insights into a novel approach for assessing the treatability of bamboo species.

THE MEASUREMENT QUALITY EVALUATION OF AN ULTRASONIC FLOW SENSOR WITH A COMPLEX MEASURING PATH TRAJECTORY

Over the past ten years, ultrasonic measuring instruments have become most widespread in industrial measurements of the flow and quantity of various energy resources. Such instruments differ in design, method of obtaining the output signal, number and topology of acoustic waves propagation and, accordingly, have different metrological performances. The accuracy of the measured signal formation is determined by the quality of the flow sensor. At the same time, the components of quality are metrological performances, manufacturability of the design, ease of setup, cost and others. The purpose of the work is to compare, analyze and evaluate the quality of flow measurements when using a single-channel ultrasonic sensor with a complex trajectory of the measuring beam and a multi-path (multichord) ultrasonic sensor. As a result of simulation modeling, distributions of flow velocities in longitudinal sections and cross sections were obtained, correction factors for the measured signal were determined, and pressure losses were calculated. A comparative analysis of the measurement quality of the investigated flow sensors made it possible to identify the advantages of using a single-path flow transducer with acoustic wave reflection. We are talking about the possibility of accurately outputting a useful signal, higher metrological sensitivity, higher measurement accuracy, as well as minimal impact on the measured medium due to the creation of smaller geometrically sized local hydrodynamic resistance along the length of the measuring path. The further research prospect is the study of ultrasonic flow measuring sensors with different topologies of acoustic channels when measuring and recording flow and quantity for different flow regimes of the measured medium.

THE ROLE OF SURROGATE MODELS AND MACHINE LEARNING IN MODERN ULTRASONIC FLOW MEASUREMENT

Recent developments in the field of machine learning have found their application in a wide range of design processes. They have particular use where numerical simulations are involved and fast, more accurate predictions and optimized models are very much needed. In order to speed up experiments on a device or system model, it is necessary to speed up its execution (simulation). Instead of detailed models, you can create a surrogate. Its main task is fast execution, small amount of occupied memory and preservation of the specified error threshold in relation to the detailed model. This article demonstrates the integration of machine learning into the flow measurement process using ultrasonic flowmeters. The main source of errors in the application of the modern ultrasonic principle of flow measurement arises from the difficulty of taking into account the actual velocity profile of the measuring flow. In practice, the distribution of velocities in the cross-section of the pipeline differs from the theoretical one introduced in the calculation algorithm. However, if the velocity profile is known, an appropriate correction can be estimated and taken into account during calibration. This will increase the accuracy of measurements. In this study, an intelligent compensation of errors caused by profile distortion was presented to improve the accuracy of using multipath meters in such ultrasonic conditions. The purpose of such an intelligent correction arises in the search for the optimal layout and the minimum sufficient number of chords in the measuring transducer for various installation conditions. The adoption of a new approach based on a surrogate model with a neural network made it possible to take an approximate flow profile that has a certain distortion. So, for the chosen topology of the acoustic flow sensing channels, programmatically, by changing the location angle of the measuring system, instead of the local resistance, add such a position of the chords for which it is possible to set maximum admissible measurement accuracy. This means using a neural network for the required input correction model, especially in an environment characterized by a change in the velocity profile under the influence of different flow distortions.

The Prediction of Failure in the Gas Filtration System in Low-Pressure Carburising Furnaces

Predictive maintenance is one of the key aspects of Industry 4.0. The article presents the results of experimental tests of nitrogen purification filters in the installation of a low-pressure, metal processing device. The aim of the research was to develop a predictive algorithm for making decisions regarding the replacement of used filters, based on flow analysis and measurement of the pressure difference in front of and behind the tested filter. For the purposes of the research, a special test stand was constructed, which made it possible to determine the operating characteristics of three selected filters. Based on the tests carried out, the limit characteristics of the parameters measured were determined, identifying the need to replace filters in the gas installation.

Pathlength-selective, interferometric diffuse correlation spectroscopy (PaLS-iDCS).

Diffuse correlation spectroscopy (DCS) is an optical method that offers non-invasive assessment of blood flow in tissue through the analysis of intensity fluctuations in diffusely backscattered coherent light. The non-invasive nature of the technique has enabled several clinical applications for deep tissue blood flow measurements, including cerebral blood flow monitoring as well as tumor blood flow mapping. While a promising technique, in measurement configurations targeting deep tissue hemodynamics, the standard DCS implementations suffer from insufficient signal-to-noise ratio (SNR), depth sensitivity, and sampling rate, limiting their utility. In this work, we present an enhanced DCS method called pathlength-selective, interferometric DCS (PaLS-iDCS), which improves upon both the sensitivity of the measurement to deep tissue hemodynamics and the SNR of the measurement using pathlength-specific coherent gain. Through interferometric detection, PaLS-iDCS can provide time-of-flight (ToF) specific blood flow information without the use of expensive time-tagging electronics and low-jitter detectors. The new technique is compared to time-domain DCS (TD-DCS), another enhanced DCS method able to resolve photon ToF in tissue, through Monte Carlo simulation, phantom experiments, and human subject measurements. PaLS-iDCS consistently demonstrates improvements in SNR (>2x) for similar measurement conditions (same photon ToF), and the SNR improvements allow for measurements at extended photon ToFs, which have increased sensitivity to deep tissue hemodynamics (~50% increase). Further, like TD-DCS, PaLS-iDCS allows direct estimation of tissue optical properties from the sampled ToF distribution without the need for a separate spectroscopic measurement. This method offers a relatively straightforward way to allow DCS systems to make robust measurements of blood flow with greatly enhanced sensitivity to deep tissue hemodynamics, enabling further applications of this non-invasive technology.

Micromachined needle-like calorimetric flow sensor for sap flux density measurement in the xylem of plants

Miniaturized silicon thermal probes for plant’s sap flow measurement, or micro sap flow sensors, have advantages in minimum invasiveness, low power consumption, and fast responses. Practical applications in sap flow measurement has been demonstrated with the single-probe silicon micro sensors. However, the sensors could not detect flow directions and require estimating zero sap flow output that leads to significant source of uncertainty. Furthermore, silicon-needles would break easily during the insertion into plants. We present the first three-element micro thermal sap flow sensor packaged on a durable printed circuit board needle that can measure bidirectional flows with improved dynamics and precision. The performance of the newly designed calorimetric flow sensor was confirmed through precision calibration and field test on tomato stems. A calibration curve for a tomato stem was obtained with a sensitivity of 0.299 K/(µL mm−2 s−1) under the maximum temperature increase of 4.61 K. Results from the field test for one month revealed a correlation between the measured sap flux density and related conditions such as solar radiation, vapor pressure deficit, sunshade and irrigation. The developed sensor will contribute to practical long-term sap flow monitoring for small and delicate plants with minimal physical invasion.

Numerical simulation and experimental study of aluminum heat exchanger based on Comsol Multiphysics

Controlling the temperature of the air flow during printing can greatly improve the data measurement of air flow and the printing effect of selective laser melting equipment. In this study, an aluminum-welded heat exchanger was designed and manufactured combined with an engineering application example. The thermal performances of heat exchanger were carried out by experiment and numerical simulation in Comsol Multiphysics. Results show that the model has high accuracy (the relative error is less than 12% in most cases and the absolute error is less than 16 Pa below the flow rate of 350 m3/h), and the overall pipeline resistance loss is small. The temperature difference between outlet and inlet is always lower than 6.5 °C during actual working conditions, which meets the requirements for use. The research can provide good theoretical guidance for the design and application of aluminum heat exchangers.

Lagrangian particle tracking in the atmospheric surface layer

Abstract Field measurements in the atmospheric surface layer (ASL) are key to understanding turbulent exchanges in the atmosphere, such as fluxes of mass, water vapor, and momentum. However, current field measurement techniques are limited to single-point time series or large-scale flow field scans. Extending image-based laboratory measurement techniques to field-relevant scales is a promising route to more detailed atmospheric flow measurements, but this requires significant increases in the attainable measurement volume while keeping the spatiotemporal resolution high. Here, we present an adaptable particle tracking system using helium-filled soap bubbles, mirrorless cameras, and high-power LEDs enabling volumetric ASL field measurements. We conduct analyses pertinent to image-based field measurement systems and develop general guidelines for their design. We validate the particle tracking system in a field experiment. Single-point Eulerian velocity statistics are presented and compared to data from concurrently operated sonic anemometers. Lagrangian displacement statistics are also presented with a comparison to Taylor’s theory of dispersion. The system improves the state-of-the-art in field measurements in the lower atmosphere and enables unprecedented insights into flow in the ASL.

Calculating a conductor’s temperature-related sag as the limiting value for a Dynamic Line Rating

The ampacity — a term that refers to the maximum current in amperes — of existing overhead lines can be increased using Dynamic Line Rating (DLR) systems. Based on ambient online conditions and electrical power flow measurements, together with a forecast of future ambient conditions, the ampacity of overhead lines can be dynamically adjusted. In essence, the ampacity of an overhead line is determined by the operating temperature of the conductor that still guarantees the required safe distances to the objects under the overhead line. This paper presents a calculation algorithm for the sag of a conductor that addresses an unequal temperature of the conductor along the line as a response to an expected problem in the future, when increasing numbers of DLR sensors will be installed on or even near overhead lines. A novel approach to the sag-temperature calculation useful for a DLR is developed based on the linearization of cable equations. As a result, the computational costs are greatly reduced, which is an important factor when the DLR system includes a large number of overhead lines and processes them simultaneously. The presented methods are open and can be adapted for an arbitrary DLR system.

Utility of Transit-Time Flow Measurement for Intraoperative Graft Evaluation in Coronary Artery Bypass Grafting

Utility of Transit-Time Flow Measurement for Intraoperative Graft Evaluation in Coronary Artery Bypass Grafting

Doppler Sonography Evaluation of Median Nerve Intraneural Blood Flow: A Systematic Review

Objective: This systematic review aims to determine the extent, scope, and nature of research using the sonographic measurement of intraneural blood flow within the median nerve and to identify, characterize, and compare image acquisition and analysis protocols that have been reported as potential candidate techniques for standardizing research and clinical applications. Materials and Methods: This systematic review summarizes image acquisition protocols and analysis methodologies from 52 current research studies using Doppler ultrasound to examine median nerve intraneural blood flow. Results: Four types of Doppler technologies were identified: power Doppler, color Doppler, spectral Doppler, and Superb Microvascular Imaging, but there were inconsistencies in how images were acquired and analyzed. Intraneural blood flow measurements were categorized into four types based on a combination of measurement level (e.g., binary, ordinal, continuous) and type of flow indicator (e.g., pixel count, intensity, velocity). Conclusion: Standardized imaging protocols and reporting guidelines are needed to improve consistency. Future studies should evaluate the accuracy and reliability of different image acquisition methods and analysis measurements.

The Predictive Significance of Doppler Parameters on the Arteriovenous Fistula Maturation for Hemodialysis—A Single Center Experience

Background: Doppler ultrasound examination of blood vessels has a significant role in planning and identifying parameters that affect the functioning and maturation of arteriovenous fistula (AVF). Our goal was to determine the predictive parameters of Doppler ultrasound, measured at different time distances, which affect the maturation of AVF for hemodialysis. Materials and Methods: The research was a retrospective cohort study. The criteria for selecting patients in our study was the existence of information on ultrasound examinations of the lumen of blood vessels before the creation of AVF, as well as lumens of fistula conduits and blood flow measurements, at time intervals of 6–8 weeks and 2–4 months, after the creation of AVF, which we recorded in 105 patients. The respondents were divided into two groups: a group of patients with immature, and mature fistulas. Basic demographic data, clinical characteristics of the responders and laboratory parameters were analyzed. Results: By comparing clinical and laboratory parameters between the group of subjects with and without AVF maturation, a statistically significant difference was determined between the lumen of the proximal radial vein (p = 0.008) and the lumen of the distal radial vein (p = 0.001). The diameter of the fistulous veins (p = 0.037), and the blood flow through the AVF 6–8 weeks (p = 0.001) and 2–4 months (p = 0.001) after its creation were statistically significantly higher in subjects with mature fistulas. By univariate regression analysis, brachial vein (p = 0.04), proximal (p = 0.011) and distal radial artery (p = 0.001), fistula vein, after 6–8 weeks (p = 0.002), blood flow through AVF 6–8 weeks (p = 0.001) and 2–4 months (p = 0.001) after AVF creation, are statistically significant parameters. Predictive parameters of AVF maturation are AVF blood flow after 6–8 weeks (p = 0.010) and AVF blood flow after 2–4 months (p = 0.001). Conclusion: Our research confirmed that greater the blood flow through AVF, at time intervals of 6–8 weeks and 2–4 months after creation, the better the maturation.

Effects of flows on transparent exopolymer particles released from branching Acropora coral colonies

Transparent exopolymer particles (TEP), a major component of coral mucus, are responsible for particle aggregation. These particles contribute substantially to the carbon cycle in coral reefs, and serve as an energy source for bacteria and other microorganisms. Water flows and induced turbulent mixing control material exchange between the coral canopy and the surrounding water, which is critical for coral health. However, how these factors affect TEP release by coral colonies has yet to be evaluated. Using a recirculating flume, we assessed TEP release by branching Acropora coral colonies and associated bacterial growth in the water column under different unidirectional flows. Changes in TEP and bacterial concentrations after 24-h incubation were quantified for flow speeds of 0, 5, 10, and 30 cm/s. Particle image velocimetry (PIV) measurements provided an estimate of turbulent mixing efficiency above the coral canopy. TEP and bacterial concentrations in the water column increased after 24 h of incubation. The increase in TEP and bacterial concentrations were 6.2–9.3 times and 3.4–5.1 times higher in the absence of flows, respectively, than mean values under water flows. Although mixing efficiency increased linearly with mean flow speeds, TEP release and bacterial growth differed only marginally at flows ranging from 5–30 cm/s. Detailed flow measurements combined with evaluation of TEP release suggest that the complex geometry of corals facilitates efficient material exchange at a range of flow speeds, and highlight the importance of considering these factors when estimating coral reef biogeochemistry.

Experimental speed-of-sound data and a fundamental equation of state for normal hydrogen optimized for flow measurements

Speed-of-sound measurements for normal hydrogen (n-hydrogen) in a temperature range between 273 K and 323 K were carried out using a cylindrical resonator at pressures from 1 MPa to 10 MPa and a dual-path pulse-echo system at pressures from 20 MPa to 100 MPa. The relative expanded uncertainties (k = 2) of the measurements range from 0.04 % to 0.08 %. Based on these measurements and data from the literature, a fundamental equation of state (EOS) was developed for the calculation of thermodynamic properties of n-hydrogen. It is expressed in terms of the Helmholtz energy with the independent variables temperature and density. Due to the fundamental nature of the Helmholtz energy, the equation can be used to calculate all thermodynamic properties from one mathematical expression. In contrast to typical EOS of this kind, the boundary conditions are somewhat more restricted. The relevant temperature and pressure ranges are limited to typical pipeline and storage conditions of gaseous hydrogen, including temperatures relevant for measurements with critical nozzles (140 K to 370 K with pressures up to 100 MPa). The computational speed for the implementation of the correlation in measurement sensors plays a superior role. Therefore, the equation is kept as short as possible, and exponents are of integer-kind. Most of the experimental data are still reproduced within their measurement uncertainties.

Two-Phase Particle Image Velocimetry Visualization of Rewetting Flow on the Micropillar Interfacial Surface.

Boiling heat transfer has a high thermal efficiency by latent heat absorption, which makes it an attractive process for cooling electronic device chips. Critical heat flux (CHF), the maximum heat flux, is a crucial factor determining the operating range of the boiling applications. The CHF can be enhanced by improving the fluid supply to the boiling surface. Herein, micropillar interfacial surfaces have been proposed to increase the CHF by increasing the rewetting flow, which determines the fluid-supply capacity near the bubble contact line. A state-of-art two-phase particle image velocimetry (two-phase PIV) technique is introduced for rewetting flow measurement on micropillar structures (MPSs) to analyze the CHF-enhancement mechanism. The two-phase PIV visualization setup offers high spatial (∼120 μm) and temporal (∼2000 Hz) resolutions for measuring rewetting flow during bubble growth. The MPS samples exhibit enhanced CHF and rewetting flows compared to those on a plain surface. The roughest case, D04G10 sample, had a CHF of 164 W/cm2, 1.84 times higher than that of the plain surface. The D04G10 sample also recorded the highest rewetting velocity of 0.311 m/s, 4.7 times higher than that of the plain surface. The comparison between the rewetting flow and wicking performance shows that wicking-induced flow accounted for a substantial part (∼17%) of the rewetting flow and contributed significantly to the CHF enhancement owing to large rewetting flow by delaying vapor-film formation. Based on these findings, a new CHF model suggested by introducing the rewetting parameter shows a high CHF prediction accuracy of 94%.