Flow Measurements Research Articles

Flexible polydimethylsiloxane pressure sensor with micro-pyramid structures and embedded silver nanowires: A novel application in urinary flow measurement

Flexible pressure sensors are lightweight and highly sensitive, making them suitable for use in small portable devices to achieve precise measurements of tiny forces. This article introduces a low-cost and easy-fabrication strategy for piezoresistive flexible pressure sensors. By embedding silver nanowires into a polydimethylsiloxane layer with micro-pyramids on its surface, a flexible pressure sensor is created that can detect low pressure (17.3 Pa) with fast response (<20 ms) and high sensitivity (69.6 mA kPa−1). Furthermore, the pressure sensor exhibits a sensitive and stable response to a small amount of water flowing on its surface. On this basis, the flexible pressure sensor is innovatively combined with a micro-rotor to fabricate a novel urinary flow-rate meter (uroflowmeter), and results from a simulated human urination experiment show that the uroflowmeter accurately captured all the essential shape characteristics that were present in the pump-simulated urination curves. Looking ahead, this research provides a new reference for using flexible pressure sensors in urinary flow-rate monitoring.

A novel flow rate measurement method for fire hose based on vibration signal and neural network

During fire incidents, it is imperative to monitor the flow rate of the fire hoses. Due to the constraints imposed by the fire scene, vibration-based flow measurement technique has shown great potential. However, usage of single frequency or statistic feature to predict flow rate is prone to influenced by outer noise. In this study, we constructed a dataset for fire-hose flow rate prediction task with a flow rate range of 0.35 L/s to 20.00 L/s, and sample frequency of 50 kHz. On that basis, a new variant of residual network, i.e., an RBU-STMS has been developed, integrating soft thresholding and feature pyramid mechanism. Evaluation result on the dataset has proven the effectiveness of the developed model which yields improvement of 3.85 % and 4.05 % by incorporating the two mechanisms individually and an overall improvement of 5.00 % by combining both mechanisms, compared to the conventional residual network. Furthermore, the proposed model exhibits a considerable tolerance to noisy inputs, with a predicted error rate of only 8.06 % when subjected to a 10 % standard deviation of random noise in the input, remaining below the 10 % threshold.

Quantifying aortic valve regurgitation in patients with congenital aortic valve disease by 2D and 4D flow magnetic resonance analysis

BackgroundIn congenital aortic valve disease, quantifying aortic regurgitation (AR) varies by the measurement site. Our study aimed to identify the optimal site for AR assessment using 2D and 4D MR flow measurements, with a focus on vortices. MethodsWe retrospectively analysed 31 patients with congenital aortic valve disease, performing 2D and 4D MR flow measurements at the aortic valve, sinotubular junction (STJ), ascending aorta (AAo), and using midpulmonary artery measurements as a reference.We assessed percentage AR and net forward volumes, calculated linear correlations, and plotted Bland-Altman plots. Net forward flow at all aortic sites were correlated with the main pulmonary artery. Differences in AR between 2D and 4D flows were linked to vortices detected by 4D streamlines. ResultsThe best agreement in % AR between 2D and 4D flows was at the aortic valve (mean difference 4D2D -2.9%, limits of agreement 8.7% to −14.3%; r2 = 0.7). Correlations weakened at STJ and AAo. Vortices in the ascending aorta led to AR overestimation in 2D measurements. Net forward flow at the aortic valve by 4D flow correlated closer with main pulmonary artery than did 2D flow. (Mean difference for 2D and 4D MR flow 7.5 ml and 4.2 ml, respectively). ConclusionsFor congenital aortic valve disease, the most accurate AR quantification occurs at the aortic valve using 2D and 4D MR flow. Notably, vortices in the ascending aorta can result in AR overestimation with 2D MR flow.

Gain scheduled internal model control based on the dynamic sliding mode method for the water level of nuclear steam generators

Abstract The Steam Generator (SG) is a crucial component of a nuclear power plant. Proper water level control in a nuclear steam generator is of great importance to ensure a sufficient cooling source for the nuclear reactor and to prevent damage to turbine blades. The water level control problem of steam generators has been a leading cause of unexpected shutdowns in nuclear power plants, which must be addressed for plant safety and availability. The control problem is challenging, particularly at low power levels due to shrink and swell phenomena and flow measurement errors. Furthermore, the dynamics of the steam generator vary as the power level changes. Therefore, there is a need to enhance the water level control system of the SG. In this paper, a Gain Scheduled Internal Model Control (IMC) based on the Dynamic Sliding Mode (DSMC) method is developed for the level control problem. The proposed method exhibits the desired dynamic properties throughout the entire output tracking process, independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness, and stability. The simulation results confirm the improvement in transient response achieved by using the proposed controller.

Spectral proper orthogonal decomposition of time-resolved three-dimensional flow measurements in the turbulent wake of the Ahmed body

Spectral proper orthogonal decomposition of time-resolved three-dimensional flow measurements in the turbulent wake of the Ahmed body

An experimental approach to heat loss measurement of horizontal two-phase flow boiling in low-pressure low-flow (LPLF) conditions

A crucial parameter remarkably influencing the reliability and accuracy of vapor quality measurements in flow boiling experiments is the measurement of heat loss. The latent heat loss estimation in two-phase flow boiling sounds more demanding than that of sensible heat loss in single-phase flow experiments. To accurately investigate the impact of vapor quality on the heat transfer coefficient of flow boiling, accurate estimates of heat loss and subsequent calibration of heat supplies are of a great significance. It is widely common that the single-phase flow tests are performed to estimate a fixed heat loss percentage and calibrate heat supplies for further measurements of vapor quality and heat transfer coefficient of flow boiling experiments. In the present work, an empirical methodology is first proposed to measure heat losses and calibrate latent heat supplies directly from flow boiling process. The proposed methodology is then compared and verified with the commonly applied methodology which uses single-phase flow experiments. The proposed methodology exhibited higher accuracy than the single-phase-based methodology to estimate heat losses and measure vapor quality within two-phase flow boiling under low-pressure low-flow (LPLF) operating conditions.

Role of Gas Aspiration through Ladle Shroud and Influence on Tundish Hydrodynamic Performances: A Physical and Mathematical Modeling Study

Gas aspiration through ladle shroud, during the teeming of a ladle into a tundish, has been investigated via physical and mathematical modeling. To this end, a volume of fluid‐based two‐phase turbulent flow model (in conjunction with the standard k–ε turbulence model) and a full‐scale two‐strand bloom casting tundish have been applied. Both flow and residence time distribution measurements are carried out in the full‐scale tundish system, adopting well‐established measurement techniques. Computational results, supported appropriately with experimentally measured data, indicate that gas aspiration alters flow and turbulence profoundly in the vicinity of the shroud entry zone. Early reversal of jetting flow toward the free surface, due to the buoyancy of the entrained gas, increases the overall intensity of motion in the tundish, creating more mixing flow volumes at the expense of plug flow volume. Most importantly, however, gas aspiration through shroud tends to drastically cut down interactions between the down coming liquid jet metal and the pouring box, making the specific design and shape of a pouring box redundant toward desirable flow modification. Finally, it is shown that strong surface flows and turbulence, generated due to gas aspiration, can be suitably damped by deploying a set of weirs, increasing plug flow volume in tundish.

High fidelity core flow measurement experiment for an advanced research reactor using a real scale mockup

Owing to spatial effects and vortex flow, flow in research reactors that use plate-type fuels can be maldistributed to the parallel channels of the core, which significantly impacts the reactor safety. In this study, the core flow of an advanced research reactor was measured in a real-scale facility under various hydraulic conditions. For flow measurement, integrated pressure lines were embedded in the mockups of 22 fuel assemblies and six fission molybdenum assemblies. Each assembly mockup was individually calibrated to obtain the relationship between the pressure drop and flow rate. Real-scale facility, which implements the characteristics of the hydraulic conditions in research reactors, was then used to evaluate the assembly-to-assembly flow distribution under normal operating condition, a partially withdrawn condition for the follower fuel assemblies, no flow for the pool water management system, and 1:1.5 asymmetric inlet flow condition. As a parallel channel system, core flow distribution was analyzed with conventional header design approach. Taking into account the measuring uncertainty, the core flow was uniformly distributed within 5 % under all conditions. This was mainly because the core flow resistance was sufficiently high and the vortex flow was minimized by the perforated plate.

A robust computational framework for variational data assimilation of mean flows with sparse measurements corrupted by strong outliers

A variational framework for the reconstruction of time-averaged mean flows using a sparse set of observations with large magnitudes of noise (referred to as outliers), is presented. The observations constitute a set of point-wise measurements of the mean flow with outliers at certain measurement locations and are incorporated into a numerical simulation governed by the two-dimensional, incompressible Reynolds-averaged Navier-Stokes (RANS) equations with an unknown momentum forcing. This forcing, which corresponds to the divergence of the Reynolds stress tensor, is calculated from a direct-adjoint optimization procedure to reduce the deviation between the measured and estimated mean velocities. ℓ2, ℓ1, Huber, and hybrid loss functions are used to represent the discrepancy in the mean velocity field between the measurements and the predictions. A variety of algorithms are considered to solve the optimization problem with these loss functions and a performance comparison in terms of the quality and physical features of the recovered mean flow is presented. The Huber loss function performed best as it remained robust to strong outliers in the measurements with its ℓ1 contribution and also ensured the uniqueness of the optimal solution with its ℓ2 contribution. Huber loss functions restrict the effect of outliers at the local measurement locations, thereby not affecting the quality of the high-dimensional reconstructed mean flow field. The hybrid loss function, a modified form of the continuous Huber loss function, also recovered the mean flow with high accuracy. We demonstrate the performance of the data assimilation framework for the case of two-dimensional laminar flow around a circular cylinder at Re=100. We then extend the analysis to the case of two-dimensional laminar flow over a backward-facing step at Re=500, to further assess the efficacy and robustness of the data assimilation framework.

Reactive control of velocity fluctuations using an active deformable surface and real-time PIV

This study demonstrates an experimental realization of turbulence control strategies previously explored by Choi et al. (J. Fluid Mech., vol. 262, 1994, pp. 75–110) through numerical simulations. To conduct the experiments, a deformable surface with a streamwise array of 16 independently controlled actuators was developed. A real-time particle image velocimetry (RT-PIV) system was also created for flow measurements. The objective of the control strategy was to target the sweep and ejection motions of the vortex shedding from a spherical cap placed in a laminar boundary layer. Reactive control strategies consisted of wall-normal surface deformations that opposed or complied with the wall-normal (v) or streamwise (u) velocity fluctuations obtained from the RT-PIV. The results showed two primary outcomes of the control approach. Firstly, it effectively hindered the advancement of sweep motions towards the wall. Secondly, it disrupted the periodic shedding of vortices. The v-control with opposing wall motions and u-control with compliant wall motions exhibited strong inhibition of sweep motions, while the v-control with compliant and u-control with opposing wall motions showed weaker inhibition. All reactive control cases resulted in the disruption of vortex shedding. In some instances, this disruption was accompanied by increased turbulent kinetic energy due to the generation of additional flow motions. However, the v-control with opposing wall motions significantly reduced the vortex-shedding energy while maintaining total turbulent kinetic energy close to or below that of the unforced flow. Overall, the experiments show the effectiveness of reactive control strategies in mitigating sweep motions and disrupting vortical structures, offering insights for developing reactive control strategies.

Potential of the domestic biosimile omalizumab in achievement of control in patients with severe asthma: short communication

BACKGROUND: Severe atopic asthma is a medical and social problem due to its prevalence, the tendency to exacerbations, the impact on the quality of life and on the work ability, and high treatment costs. The appearance biosimilar omalizumab among biologicals makes such therapy more accessible to patients. This article presents the results of an open prospective clinical study of the biosimilar omalizumab in patients with the severe atopic asthma.
 AIM: To evaluate the efficacy and tolerability of the domestically produced biosimilar omalizumab in the real clinical practice.
 MATERIALS AND METHODS: The study involved 15 adult patients (19–66 years) with a reliable history consistent with moderate to severe atopic asthma who hadn`t have asthma control at the time of inclusion in the study. All patients received the Genolar (omalizumab, Generic JSC, Russia) for 52 weeks at the dose calculated according to the instructions. The efficacy was evaluated taking into account changes in symptom severity, improved asthma control using the Asthma Control Questionnaire (ACQ-5), pulmonary function tests, peak flow measurements, assessment the asthma exacerbations number and the healthcare resources use.
 RESULTS: According to our study results, all patients demonstrated a decrease in the night and daytime attacks frequency and the shortness of breath severity due to omalizumab, which made it possible to reduce the basic therapy and refuse systemic glucocorticosteroids using in patients who previously received there. After 6 months we obtained an improvement in the asthma symptoms control: ΔACQ-5=-1.87 (p=0.0002) compared to baseline with a trend towards further improvement in indicators and reached ΔACQ-5=-2.18 (p=0.0001) to the 52nd week. We also obtained a statistically significant improvement in pulmonary function (after a year of treatment, the increase in forced expiratory volume in the first second was +19.85% compared to baseline, p=0.0001). No asthma exacerbation was registered during 12 months omalizumab treatment.
 CONCLUSION: Our study showed that the biosimilar treatment in patients with severe atopic asthma allowed to achieve asthma control, decrease the exacerbations number and reduce the basic therapy volume, including oral-corticosteroid elimination.

An experimental investigation on the fluid–structure coupling in horizontal pipes conveying two-phase intermittent flow

Two-phase flow is typically found in several industrial applications, such as in the production and transportation of oil and gas in the petrochemical industry, in the catalytic cracking and microreactors in the chemical industry, and in nuclear reactor cooling pumps. Measurement of two-phase flow features is usually necessary and has been done in several ways, including pressure probes, resistive sensors, gamma-ray, wire-mesh sensor and many others. However, these are either intrusive or invasive techniques, which might be of challenging application in industrial environments, or rely on a hazardous radioactive source. Vibration-based measurement of two-phase flow in pipes stands out as a non-invasive/non-intrusive approach and, consequently, multiphase-flow induced vibration in pipes has receiving increasing attention in recent years. In this work, the dynamic behaviour of a horizontal tube conveying an intermittent two-phase gas-liquid flow is investigated based on indirect approaches. The phenomenon of fluid–structure coupling is investigated using acceleration and pressure measurement. Moreover, the bubble size distribution is estimated from high-speed camera images and a deep learning model for image segmentation, along with its spectral content and time modulation. Focus is given at frequency bands around the cut-on frequencies of the circumferential wave modes of the pipe. An approach based on the estimation of frequency response function of the pressure and vibration at the liquid slug and elongated bubble is proposed, such that the coherence function can be used as quantitative measure of the coupling. Two experimental conditions with intermittent flow are investigated as representative cases. It is shown that there is a great vibration amplification at the cut-on frequencies of circumferential wave modes in pipes due to the corresponding structural wave and pressure coupling. Consequently, the frequency of passage of bubble can be estimated from the demodulation of vibration response filtered at the cut-on modes. The experimental results pave the way for innovative vibration-based measurement approaches.

Role of Coriolis flow measurement technology in validation of model of syringe driver performance

The development of a flow/pressure measurement system in association with Bronkhorst High-Tech B.V. incorporating a Coriolis flow transducer, provided an opportunity to observe the flow/pressure dynamics of syringe drivers. A model of flow/pressure performance of syringe drivers was established where key variable factors included the compliance of the connected system and the associated line resistance. It was identified that the flow/pressure dynamics observed with the flow measurement system incorporating the Coriolis transducer matched that of the model. In this consideration the dominant compliance contribution related to that of the syringe. The model operates by considering the notional volume change in the residual fluid volume in the syringe with inflow from stepper motor action and outflow in the interval between sequential pulses. While many of the observations in the literature of syringe driver function are qualitative, the model allows a more precise prediction of associated device performance.

Occupancy sensor-enabled demand control ventilation using virtual outdoor air flow meters in air handling units without an outdoor air flow meter

Nowadays, the outdoor air (OA) flow requirement for demand control ventilation (DCV) can be accurately determined using occupancy sensors in commercial buildings. However, in air handling units (AHUs) without precise OA flow measurements, the OA is often controlled by a fixed-damper position method, which cannot maintain the required OA flow rate. The objective of this study is to develop and evaluate occupancy sensor-enabled DCV OA control using a virtual OA flow meter in AHUs. Firstly, a virtual OA flow meter is derived from a virtual supply fan flow meter by applying the correlation between the OA ratio and damper position under appropriate building pressure control. Subsequently, experiments are conducted to calibrate the virtual OA flow meter in an AHU with the design OA flow rate of 120 L/s. Finally, occupancy sensor-enabled DCV OA control is implemented by using the calibrated virtual OA flow meter. The evaluation results show that the proposed DCV OA control can match the actual OA flow rate well with the required OA flow rate. The root mean squared error (RMSE) falls within the range of 16–20 L/s, demonstrating an improvement over the fixed-damper position control, which yields an RMSE of 36 L/s.

A Mini-Review of Recent Developments in Plenoptic Background-Oriented Schlieren Technology for Flow Dynamics Measurement

To uncover the underlying fluid mechanisms, it is crucial to explore imaging techniques for high-resolution and large-scale three-dimensional (3D) measurements of the flow field. Plenoptic background-oriented schlieren (Plenoptic BOS), an emerging volumetric method in recent years, has demonstrated being able to resolve volumetric flow dynamics with a single plenoptic camera. The focus-stack-based plenoptic BOS system can qualitatively infer the position of the density gradient in 3D space based on the relative sharpness of the refocused BOS image. Plenoptic BOS systems based on tomography or specular enhancement techniques are realized for use in high-fidelity 3D flow measurements due to the increased number of acquisition views. Here, we first review the fundamentals of plenoptic BOS, and then discuss the system configuration and typical application of single-view and multi-view plenoptic BOS. We also discuss the related challenges and outlook on the potential development of plenoptic BOS in the future.

Can stormwater runoff measurements be used for weather radar rainfall adjustment?

ABSTRACT Predicting the response to rainfall in urban hydrological applications requires accurate precipitation estimates with a high spatiotemporal resolution to reflect the natural variability of rainfall. However, installing rain gauges under nearly ideal measurement conditions is often difficult in urban areas, if not impossible. This paper demonstrates the potential of deriving rainfall measurements in urban areas and bias-adjusting weather radar rainfall measurements using stormwater runoff measurements. As a supplement to point rainfall measurements from rain gauges, the developed bias adjustment approach uses catchment runoff-rainfall estimates derived from water level measurements of a stormwater detention pond. The study shows that the bias-adjusted radar product correlates highly with rain gauge measurements in the catchment. Moreover, the presented approach enables rainfall measurements within a catchment independent of rain gauges located in the catchment, making the technique highly applicable for increasing the density of ground observations and thus improving weather radar precipitation estimates over urban areas. The method also derives the catchment-specific runoff coefficient independently of expensive flow measurements in the catchment, making the method very scalable. This paper highlights the potential of using easily achievable catchment runoff-rainfall measurements to increase the density of available ground observations and thereby improve weather radar precipitation estimates.

Non-invasive, Continuous Measurement of Cerebral Blood Flow During Progression to Brain Death (P1-2.002)

Non-invasive, Continuous Measurement of Cerebral Blood Flow During Progression to Brain Death (P1-2.002)

Optimization of Space-Time image velocimetry based on deep residual learning

Space-Time Image Velocimetry (STIV) is considered to be a highly promising method for river flow measurement due to its safe and efficient features. However, the traditional STIV method is challenged to obtain stable and accurate results when disturbed by external environments such as obstacles, waves and noise. As a consequence, a residual network-based STIV method is constructed by combining STIV with deep learning. In the synthetic dataset validation, benefited from the unique residual module and the relation-aware global attention mechanism, the recognition accuracy of STI texture angle is as high as 99.9 %, which is much higher than that of the Efficient Net b3, ViT16 and VGG19 networks. In the real dataset, the proposed method shows stronger stability and lower error by compared with gradient tensor (GT) and fast Fourier transform (FFT) methods, whose overall recognition accuracy is above 90 % under all types of STI cases, angle error is within 2°, and flow velocity error is around 0.10 m/s. Furthermore, the model was validated by a one-year comparative measurement at the Qilijie hydrological station in 2022, and the results were compared with LSPIV, GT, and FFT methods. The R2 of the model to the measured values is 0.98, the RMSE is 0.17, and the MAE is 0.12 m/s, indicating that the method has sufficient accuracy and robustness for long-term stable and real-time monitoring of river flow.

Dynamic Light Scattering in Biomedical Applications: feature issue introduction

The feature Issue on “Dynamic Light Scattering in Biomedical Applications” presents a compilation of research breakthroughs and technological advancements that have shaped the field of biophotonics, particularly in the non-invasive exploration of biological tissues. Highlighting the significance of dynamic light scattering (DLS) alongside techniques like laser Doppler flowmetry (LDF), diffusing wave spectroscopy (DWS), and laser speckle contrast imaging (LSCI), this issue underscores the versatile applications of these methods in capturing the intricate dynamics of microcirculatory blood flow across various tissues. Contributions explore developments in fluorescence tomography, the integration of machine learning for data processing, enhancements in microscopy for cancer detection, and novel approaches in optical biophysics, among others. Innovations featured include a high-resolution speckle contrast tomography system for deep blood flow imaging, a rapid estimation technique for real-time tissue perfusion imaging, and the use of convolutional neural networks for efficient blood flow mapping. Additionally, studies delve into the impact of skin strain on spectral reflectance, the sensitivity of cerebral blood flow measurement techniques, and the potential of photobiomodulation for enhancing brain function. This issue not only showcases the latest theoretical and experimental strides in DLS-based imaging but also anticipates the continued evolution of these modalities for groundbreaking applications in disease detection, diagnosis, and monitoring, marking a pivotal contribution to the field of biomedical optics.

Wind tunnel measurement of pedestrian-level gust wind flow and comfort around irregular lift-up buildings within simplified urban arrays

The implementation of lift-up buildings has demonstrated their practicality in enhancing urban wind comfort in high-density cities. The pedestrian-level wind environment around a central lift-up building surrounded by low-rise buildings was measured using wind tunnel experiments. The time-averaged velocity field and turbulence statistics, including the turbulent kinetic energy, normal component of the Reynolds stresses, gust factor, and gust wind velocity field, were discussed. Based on the results, the pedestrian-level gust wind flow and comfort for two typical building shapes (Arc, V-shaped) were compared with Rectangular lift-up buildings under different wind directions (0∘, 90∘ and 180∘), the pedestrian-level wind environments (PLWEs) were assessed following two wind criteria for weak and windy wind conditions by wind speed thresholds and maximum allowed exceedance probabilities. The results showed that the erection of the high-rise lift-up building modified the pedestrian-level wind environment around the building groups, owing to the interaction between the downwash flow around the building and the surrounding building blocks. A region of high mean and gust wind velocity was observed at the lateral and rear side of the central lift-up building due to the lateral entrained wind and Venturi effect between elevated columns, indicating that lift-up buildings can enhance PLWEs even in the presence of surrounding buildings. The Arc-shaped lift-up building tends to generate a larger “Intolerable” area compared with V- and Rectangular-shaped buildings due to its curved surface. The wind impacts the convex portion of the building, leading to airflow divergence and facilitating downstream ventilation.