Flow Measurement Techniques Research Articles

Balancing Information Preservation and Data Volume Reduction: Adaptive Flow Aggregation in Flow Metering Systems

The critical role of network traffic measurement and analysis extends across a range of network operations, ensuring quality of service, security, and efficient resource management. Despite the ubiquity of flow-level measurement, the escalating size of flow entries presents significant scalability issues. This study explores the implications of adaptive gradual flow aggre- gation, a solution devised to mitigate these challenges, on flow information distortion. The investigation maintains flow records in buffers of varying aggregation levels, iteratively adjusted based on the changing traffic load mirrored in CPU and memory utilization. Findings underscore the efficiency of adaptive gradual flow aggregation, particularly when applied to a specific buffer, yielding an optimal balance between information preservation and memory utilization. The paper highlights the particular significance of this approach in Internet of Things (IoT) and contrasted environments, characterized by stringent resource constraints. Consequently, it casts light on the imperative for adaptability in flow aggregation methods, the impact of these techniques on information distortion, and their influence on network operations. This research offers a foundation for future studies targeting the development of more adaptive and effective flow measurement techniques in diverse and resource-limited network environments.

Comparison and uncertainty quantification of roof pressure measurements using the NIST and TPU aerodynamic databases

The pressure coefficient of a low-rise building in the ASCE wind load design provision is usually obtained from boundary-layer wind-tunnel tests. Although these tests tend to be standardized, inconsistent results from different facilities have been acknowledged as a long-standing issue. This work compares roof pressure for a low-rise building model archived in the National Institute of Standards and Technology (NIST) aerodynamic database and the Tokyo Polytechnic University database, followed by quantifying the measurement and data reduction uncertainties of the NIST datasets. The Monte Carlo simulation propagates four elemental uncertainties to the mean Cp¯, standard deviation Cp′ and peak pressure coefficient Cp,peak. Results indicate that pronounced differences in the roof pressure from two datasets are attributed to different inflow characteristics (including the Jensen number variation) and the inherent measurement uncertainties. High measurement uncertainties of Cp¯ and Cp,peak are strongly correlated with vortical flow structures, either separated flow or conical vortices at the roof corner and windward edges. Two dominant measurement uncertainty sources are distinguished: the dynamic pressure ratio uncertainty and the surface pressure tap uncertainty. Alternative flow and pressure measurement techniques are noted to potentially reduce the two dominant uncertainty sources. This work is intended to clarify measurement uncertainty sources of obtaining pressure coefficients in wind-tunnel model tests and shed lights on why large differences exist from different tests.

Understanding Turbulent Flows with High-Speed Imaging

How the simultaneous application of flow measurement techniques and high-speed imaging sheds light on turbulent entrainment

Calibration of Thermal Dissipation Probes for Xylem Sap Flow in the Wood of a Diffuse-Porous and a Conifer Species under Cyclic Heating

The most popular sap flow measurement technique uses thermal dissipation probes. Differences in wood characteristics and the natural temperature gradient between probes have affected the accuracy and applicability of the sap flow equation. In addition, the continued heat of the probe can also cause thermal damage to tree tissue. The objectives of this study were to use cyclic heating and calibrate the probes with two species: Pinus bungeana Zucc. And Salix matsudana Koidz., two typical diffuse-porous species. This experiment evaluated a thermal dissipation probe in three heating modes: continuous heating, 10 min heating and 50 min cooling (10/50), and 30 min heating and 30 min cooling (30/30). The heating modes were evaluated on two species. Temperature differences between the heating needle and the control needle under different heating modes and transpiration water consumption (whole-tree weighing method) were observed simultaneously. The sap flow estimation equation under cyclic heating mode was established by analyzing the relationship between the sap flow rate and the values obtained from whole-tree weighing. The results showed that the original equation underestimated sap flow rate of P. bungeana and S. matsudana by 67% and 60%. Under the cyclic heating modes, the modified equations were different from the original equation, and their accuracy was improved. After verification, the corrected equations [Fd = 0.0264K0.738 (P. bungeana, 30/30, R2 = 0.67), Fd = 0.0722K1.113(S. matsudana, 30/30, R2 = 0.60), Fd is the sap flow density, K is temperature coefficient] reduced the influence of the natural temperature gradient on the estimation of sap flow rate, thereby significantly improving the accuracy of sap flow rate estimation. The resulting equation may be more suitable for actual field observations of sap flow in the two tested species. The cyclic heating mode has the potential to measure plant transpiration for extended periods in the field.

Laser-Optical Shear-Flow Analysis across the Annular Gap of a Simplified Displacement Compressor Model

The present experimental feasibility study testifies the two flow measurement techniques Defocusing Particle Tracking Velocimetry (DPTV) and Interferometric Particle Imaging (IPI) for their applicability to measure the two-phase flow of thin (sub-millimeter) annular rotor-stator gaps such as occur across for the leakage flow e.g. in the housing gap of oil-injected rotary positive displacement compressors (RPDC). To provide unrestriced optical access to the annular gap and in turn eliminate secondary effects, a simplified displacement compressor model has been developed and fabricated from perspex. The proof-of-concept results of both experimental campaigns (DPTV & IPI) are discussed and avenues for future efforts towards a straight-forward and accurate applicability of either method are elaborated.

3D Lagrangian Particle Tracking in Fluid Mechanics

In the past few decades various particle image–based volumetric flow measurement techniques have been developed that have demonstrated their potential in accessing unsteady flow properties quantitatively in various experimental applications in fluid mechanics. In this review, we focus on physical properties and circumstances of 3D particle–based measurements and what knowledge can be used for advancing reconstruction accuracy and spatial and temporal resolution, as well as completeness. The natural candidate for our focus is 3D Lagrangian particle tracking (LPT), which allows for position, velocity, and acceleration to be determined alongside a large number of individual particle tracks in the investigated volume. The advent of the dense 3D LPT technique Shake-The-Box in the past decade has opened further possibilities for characterizing unsteady flows by delivering input data for powerful data assimilation techniques that use Navier–Stokes constraints. As a result, high-resolution Lagrangian and Eulerian data can be obtained, including long particle trajectories embedded in time-resolved 3D velocity and pressure fields.

Experimental Investigations of the Hypersonic Stream-Traced Performance Inlet at Subdesign Mach Number

Stream-traced inlets offer superior compression efficiency for scramjet engines and are strong prospects for practical application. However, only limited experimental information is available on the subdesign performance of these inlets. In this study, the operation of a stream-traced truncated-Busemann inlet with a design point of Mach 5.5 and a physical contraction ratio of is experimentally investigated in a Mach 4.0 flow. Several nonintrusive flow measurement techniques are employed to provide a thorough understanding of the intricate flowfield within these inlets at various operation conditions. The measurements include surface pressure, mean streak-line patterns, off-body velocity fields, and qualitative gas density fields. Together, these datasets provided a unique understanding of the flow evolution and load distribution within the inlet and isolator with and without application of an external backpressure. The facility effects on the inlet operation are also explored. Without appropriate boundary-layer conditioning, the wind-tunnel starting shock could not be swallowed by the inlet; this is termed a “failed start” operation. During the failed start operation the inlet flowfield and surface pressure field, even without external backpressure, exhibited strong similarities with an unstarted inlet. The failed start operation enabled a unique lens to the flowfield in the unstarted inlet throat that could not be otherwise obtained due to optical constraints.

Numerical and experimental flow investigation using ultrasonic PIV for optimizing mechanically agitated lab-scale anaerobic digesters

In this article, a non-invasive ultrasonic flow field measurement method is studied to investigate its applicability to resolve fluid flow in bio- and chemical engineering reactors. In detail, the proposed flow field investigation method is applied to mechanically agitated lab-scale reactors for the validation of anaerobic digester mixing simulations. Two reactors with different geometries, which are cold models of real-life anaerobic digesters, are studied. Since conventional non-invasive flow field measurement techniques are not suitable for the investigated reactor geometries, the applicability of ultrasonic measurement is demonstrated. The experimental results are compared to Computational Fluid Dynamics (CFD) simulations using the Finite Volume Method with multiple reference frames to account for the stirrer-induced mixing. It is shown that ultrasonic measurement is an easily applicable non-invasive method for resolving flow fields of opaque fluids found in chemical, mechanical and biological engineering. The study highlights the benefits of the non-invasive measurement approach and also demonstrates the suitability of this flow measurement technique for further applications such as the optimization of the mixing time characteristics of paints and coatings or silicone production. The resolved flow fields are in accordance with numerical reference results with minor deviations of up to 9% for velocity measurements aligned with the main axis of the ultrasound probe. The validated CFD model can be used as a template for modelling similar chemical engineering processes where the mixing time characteristic is critical. It is further shown that the accuracy of this flow measurement method decreases with increased offsets from the main axis. In addition to the axis alignment, the impact of different fluid properties and reactor geometries is also discussed.

Determination Of Flow Velocities Using Fiber-Optic Temperature Measurements

A novel flow measuring technique is introduced to measure under harsh circumstances in environments with dirt, high pressures and elevated temperatures as in boreholes within the earth's crust. A glass fiber embedded in a cable with heating wires measures the temperature within the heated cable with distributed temperature sensing (DTS). Similar to Hot Wire Anemometry, the velocity dependence of convective heat transfer is exploited to measure the velocity of the cable as a cylinder in crossflow. A borehole-mimicking test rig and a realistic prototype of a borehole probe were built and the flow along the borehole axis was investigated. The expected Nusselt Reynolds characteristic of a cylinder in crossflow has been measured which proves the concept of this novel measurement technique. Challenges arise with the insufficient spatial resolution of DTS measurements and in the heat transfer modeling because the temperature profile of the cables cross-section must be taken into account. More detailed investigations and developments are planned to elevate this measurement technique from the current proof-of-concept stage to a reliable flow measurement technique. As a first step, the DTS technique will be extended the application of fiber Bragg grating (FBG) temperature measurements at specific points along the glass fiber. Subsequently a straight segment of a new hybrid cable will be placed in a water channel perpendicular to the flow direction. The Flow will be precisely specified using Particle Image Velocimetry and multiple temperature sensors in the channel and on the cable's sheath will deliver the information for enhanced heat transfer modelling.

ABB Robotic Laser Doppler Anemometry Measurements With RobotStudio® With An Open Wind Channel And An Ellipsoid

Laser Doppler anemometry is a state-of-the-art non-invasive experimental flow measurement technique. Traditionally used linear traversing units can only change the position of the measurement probe, but cannot change the orientation of the probe. A six degrees of freedom robot can simplify and fasten up the pose planning and measurement process real-offline. A developed LDA software plug-in for RobotStudio is used to real-offline plan and perform flow measurements in an open wind channel (flow rate = 300 m³/h) with an ellipsoid (diameter y=z = 140 mm and x = 40 mm). In 25 mm, 20 mm, 15 mm, 10 mm, 5 mm and 2 mm orthogonal distance of the ellipsoid surface the tangential velocity component is determined. Accuracy and repeatability of the robot-LDA system is found and compared to the traditional linear traversing system. Results show a positive velocity gradient towards the axis of the wind channel with a velocity range of 4.4 – 20.3 m/s. At 25 mm distance the tangential velocity is in the range of 4.4 – 12.5 m/s, at 20 mm 7.6 – 17.5 m/s, at 15 mm 12.1 – 19.7 m/s, at 10 mm 16.5 – 20.1 m/s, at 5 mm 19.0 – 20.2 m/s and at 2 mm 18.3 – 20.3 m/s. In positive y and negative z-direction, a reduction of the tangential velocity component is found in all measurements. At a distance of 25 mm, the measurement surface is slightly outside to the wind channel inlet (diameter = 80 mm). The closer the measurement surface is at the wind channel axis, the higher is the wind channel axial component. Robot-LDA average accuracy of 13 µm and repeatability of 10 µm is in the range of the linear traversing unit where the accuracy is 20 µm and the repeatability is 6 µm. The robot-LDA measurement system is an alternative to the existing linear-LDA with the advantages of real-offline robot path planning for arbitrary surfaces requiring six degrees of freedom probe placement.

Improving Effectiveness of Flow Measurement by Bypass Method: A Technique Applied to Thermal Mass Flowmeter

Abstract Fluid velocity or flow rate measurement, by flow sampling or bypassing flow from main pipelines, offers several advantages, like reducing the footprint of the flowmeter and avoiding the stoppage of a process during flowmeter repair or replacement. The flow measurement technique could be thermal mass flowmetry, a popular flow measurement method. A major limitation in the bypassing technique is the low flow rate through the bypass pipe resulting in a weak flowmeter thermal signal or reduced sensitivity to flow. This paper describes the usage of a validated computational fluid dynamics (CFD) model to investigate several bypass pipe designs to maximize fluid flow rate through the bypass pipes installed on the main pipeline and consequently maximize the thermal signal generated by an elementary thermal mass flowmeter installed on the bypass pipe. Investigations reveal that bypass design modification can improve thermal signal strength by as much as 38% with respect to that obtained in the baseline bypass design.

Contactless Inductive Flow Tomography for Real-Time Control of Electromagnetic Actuators in Metal Casting.

Flow control of liquid metals based on the actual flow condition is important in many metallurgical applications. For instance, the liquid steel flow in the mould of a continuous caster strongly influences the product quality. The flow can be modified by an electromagnetic brake (EMBr). However, due to the lack of appropriate flow measurement techniques, the control of those actuators is usually not based on the actual flow condition. This article describes the recent developments of the Contactless Inductive Flow Tomography (CIFT) towards a real-time monitoring system, which can be used as an input to the control loop for an EMBr. CIFT relies on measuring the flow-induced perturbation of an applied magnetic field and the solution of an underlying linear inverse problem. In order to implement the CIFT reconstructions in combination with EMBr, two issues have to be solved: (i) compensation of the effects of the change in EMBr strength on the CIFT measurement system and (ii) a real-time solution of the inverse problem. We present solutions of both problems for a model of a continuous caster with a ruler-type EMBr. The EMBr introduces offsets of the measured magnetic field that are several orders of magnitude larger than the very flow-induced perturbations. The offset stems from the ferromagnetic hysteresis exhibited by the ferrous parts of the EMBr in the proximity of the measurement coils. Compensation of the offset was successfully achieved by implementing a numerical model of hysteresis to predict the offset. Real-time reconstruction was achieved by precalculating the computationally heavy matrix inverses for a predefined set of regularization parameters and choosing the optimal one in every measurement frame. Finally, we show that this approach does not hinder the reconstruction quality.

Real time flow control during continuous casting with Contactless Inductive Flow Tomography

Lack of appropriate flow measurement techniques for liquid steel during continuous casting limits the application of control strategies that could improve the quality of the end product. Contactless Inductive Flow Tomography (CIFT) is a promising measurement technique that can provide information about the flow structure in the mould to a real time controller. On this basis, electromagnetic actuators can be used to react on undesired flow conditions in the mould. However, because of their nature, these actuators pose a significant challenge for inductive measurement methods. In this work we describe the influence of an electromagnetic brake on CIFT in a laboratory environment. We also show how this influence can be fully compensated, which facilitates the viability of CIFT as a key ingredient of real time control of continuous casting. Figs 5, Refs 15.

Parametric analysis of orifice plates on measurement of flow: A review

Flow measurement is a process of monitoring flow rate of fluids. Flow measurement is one of the critical processes in many industries, it is essential to carry out a detailed analysis of uncertainties associated with flow measurement. This paper attempts to understand the basics of existing flow measurement techniques and orifice flow meter in particular as it is widely used for measurement of flow due to its industry-friendly characteristics. A detailed review is presented in the paper to understand the dynamics of flow measurement, effects caused on the measurement due to variation in a physical dimension of the orifice like thickness of orifice plate, orifice-hole diameter, number of holes, etc. Discussion is also carried on to understand the influence of parameters like type of fluids, position and type of plate. The parametric effect on the performance of an orifice plate is validated using Computational Fluid Dynamics (CFD) for a better understanding of its dynamic nature.

Automated measurement of cell mechanical properties using an integrated dielectrophoretic microfluidic device

SummaryCell mechanics is closely related to and interacts with cellular functions, which has the potential to be an effective biomarker to indicate disease onset and progression. Although several techniques have been developed for measuring cell mechanical properties, the issues of limited measurement data and biological significance because of complex and labor-intensive manipulation remain to be addressed, especially for the dielectrophoresis-based approach that is difficult to utilize flow measurement techniques. In this work, a dielectrophoresis-based solution is proposed to automatically obtain mass cellular mechanical data by combining a designed microfluidic device integrated the functions of cell capture, dielectrophoretic stretching, and cell release and an automatic control scheme. Experiments using human umbilical vein endothelial cells and breast cells revealed the automation capability of this device. The proposed method provides an effective way to address the low-throughput problem of dielectrophoresis-based cell mechanical property measurements, which enhance the biostatistical significance for cellular mechanism studies.

A Comparative Analysis of In-Situ Optical Velocimetries for Oil Spill Flow Rate Estimation

In the Deepwater Horizon oil spill, optical plume velocimetry (OPV), a flow measurement technique for use in seafloor hydrothermal systems, was found to have the least uncertainty in estimating the rate at which oil was escaping from the well in the deep sea. However, OPV still had a high uncertainty of 21%, partly due to the limited accuracy of the temporal cross-correlation algorithm used. In this work, the accuracy of several in-situ optical velocimetries, namely wavelet-based optical velocimetry (WOV), OPV, and two classical correlation-based algorithms, namely fast Fourier transform (FFT) and normalized cross-correlation (NCC), for a plume flow with Reynolds numbers varying from 1847 to 11,656 was investigated. WOV, FFT, and NCC resulted in flow rates closer to the expected turbulent plume flow rate as compared to OPV. Moreover, a noisy velocity field was found using OPV. The accuracy of wavelet-based algorithm outperformed all cross-correlation based algorithms. The flow rate was measured with an error of 8.5% using WOV, whereas errors of 18.2%, 19.7%, to 21.1% were obtained when applying FFT, OPV, and NCC, respectively. There was a statistically significant difference between wavelet-based and correlation-based algorithms, but no statistically significant difference between the estimation of the three cross-correlation based velocimetries. WOV outperformed the other velocimetries and estimated flow rates with an error of 8.5%, whereas the OPV, FFT, and NCC were estimated with errors of 19.7%, 18.2%, and 50.8%, respectively.

Evaluation of Double-Sided Plasma Vortex Generator in Comparison with Vane Vortex Generator on Separation Control

The present research has introduced a new type of Plasma Vortex Generator named as Double-Sided Plasma Vortex Generator (DSPVG) that has dual expose electrodes on both sides. This DSPVG is placed normal to the surface parallel to incoming air and creates vortices on it’s both sides. As conventional VG has an angle with flow direction which introduce device drag, to overcome this, DSPVG is placed with zero angle with flow direction; besides due to the smaller thickness and frontal area with incoming air than VGs, the drag penalty due to its geometry is minimised. Furthermore, as vortices are created on both sides, DSPVG is expected to reduce the number of Plasma Vortex Generator (PVG) with respect to the conventional embedded PVGs or VGs on the flow controlling surface. Hence, it is able to take advantage of height like conventional VGs and active control systems of PVGs with dual vortices on both sides. The impact of DSPVG on separation control has been investigated experimentally and compared its effectiveness with conventional vane VGs. Three different types of flow measurement techniques have been used to confirm the repeatability and consistency of the experimental results. Numerical investigations have been carried out to evaluate the experimental results. These findings show that the DSPVG is capable to eliminate the separation similarly to the conventional VGs but with higher momentum injection and more effective in minimizing drag penalty in the uncontrolled case as in OFF condition of DSPVG, there is no alternation of local flow which is generally affected in case of VGs that adds drag penalty.

Underwater LED-based Lagrangian particle tracking velocimetry

A new white-light volumetric flow measurement technique is presented that can be used in large-scale facilities. The technique enables large volumes to be measured with high temporal and spatial resolution and without the need for a class-4 laser. This LED-based Lagrangian particle tracking velocimetry is demonstrated by measuring the tip vortex formation and the near wake of a 1.2 m diameter tidal turbine in a 25 m diameter, 2 m deep tank. Seven streamwise-distributed volumes of interest are combined, each 334 mm long, 244 mm wide and 140 mm deep, reaching up to one diameter downstream of the turbine. The system does not require re-calibration when moved. By assuming a periodic flow field, a phase-averaged flow field was reconstructed with a temporal resolution of 3.9 ms and a spatial resolution of 5.4 mm. The large volume and high time and spatial resolution could enable key research questions to be addressed on high-Reynolds-number flows and could provide valuable benchmark data for numerical model development and code validation.Graphical abstract

Understanding Turbulent Flows With High-Speed Imaging

How the simultaneous application of flow measurement techniques and high-speed imaging sheds light on turbulent entrainment

Noninvasive interrogation of local flow phenomena in twisted tape swirled flow via positron emission particle tracking (PEPT)

Twisted tape inserts are often used to enhance the performance of heat exchangers. Previous simulations suggest the existence of secondary vortices and modified axial velocity profiles in these swirled flows, with only limited experimental evidence for these predictions. In this work, positron emission particle tracking (PEPT) is used to interrogate turbulent twisted tape swirl flow in a pipe. PEPT is a noninvasive, radiotracer based flow measurement technique that does not require optical access, making it suitable for measurements in a number of engineering flow systems. The existence of the modified velocity profile and secondary flows is confirmed using PEPT, and flow is seen to still be developing 20 diameters downstream of the twisted channel entrance. Secondary vortices are further confirmed by the presence of increased vorticity in these regions, and turbulent fluctuations are seen to increase in magnitude near these flow structures. These results are in line with predictions and point to possible regions of reduced heat transfer and hot spots in twisted tape based heat exchangers. Suggestions are made for future experiments to investigate heated flows, utilizing the ability of PEPT to image flows in opaque systems for validating simulation of flows in engineering equipment, such as nuclear heat transport equipment.