Fluid Velocity Measurements Research Articles

A calibration-informed deep learning model for three-dimensional particle reconstruction of volumetric particle image velocimetry

Accurately reconstructing three-dimensional particle fields is essential in fluid velocity measurement research. This study addresses the limitations of current three-dimensional (3D) particle reconstruction methods, such as computational efficiency, precision at high particle density, and particle morphology issues, by introducing a calibration-informed deep learning model named the calibrated pixel to voxel convolutional neural network (CPV-CNN) for 3D Particle Reconstruction. This innovative neural network framework employs a unique Gaussian attention mechanism that bridges pixels and voxels, enabling the mapping of pixel features from two-dimensional (2D) particle images to 3D voxel features. This approach eliminates the need for an initial particle field for particle reconstruction, while significantly enhancing reconstruction efficiency. Additionally, the neural network incorporates camera calibration parameters and the physical coordinates of the reconstructed domain, thereby improving the model's generalization capability and flexibility. Numerical experiments demonstrate that CPV-CNN delivers superior results in terms of accuracy, generalization, and robustness in 3D particle reconstruction. The reconstructed particles exhibit favorable morphology, without the elongation issues commonly observed with conventional methods. This achievement illustrates a practical particle reconstruction algorithm based on artificial intelligence (AI) techniques and represents an important step toward developing an end-to-end AI-based particle reconstruction method in the future.

Wavelet Cross-Correlation Signal Processing for Two-Phase Flow Control System in Oil Well Production

An algorithm based on continuous measurement of multiphase flows of oil well production has been designed to improve the efficiency of the technical control of oil production processes in the field. Separation-free, non-contact measurement of multiphase flows of oil well products allows increasing the efficiency of managing oil production processes in the field. Monitoring the current density using radioisotope measuring transducers (RMTs) allows obtaining information about the structure of the flow in the form of the distribution of gas inclusions and the speed of movement of liquid and gas in a two-phase flow. Fluid velocity measurement is based on digital processing of RMT signals, applying a continuous or discrete undecimated wavelet transform to them, and assessing the cross-correlation of wavelet coefficients in individual subspaces of the wavelet decomposition. The cross-correlation coefficients of two RMT signals located at a base distance, calculated in the subspaces of the wavelet decomposition, characterize the speed of movement of gas bubbles of different sizes in a vertical pipe. The measurement assumes that the velocity of the liquid phase of the oil flow in a vertical pipe mainly corresponds to the velocity of small bubbles. This speed should be determined by the maximum cross-correlation of wavelet coefficients in the corresponding decomposition subspace. Computer modeling made it possible to evaluate the characteristics of the algorithm for controlling the speed of liquid movement in the gas–liquid flow of oil well products and determine the mass flow rate of the liquid and the relative value of the gas content. The implementation of the algorithm in a multi-channel version of the device allows monitoring an entire cluster of wells in the field.

Quantitative Digital Subtraction Angiography Measurement of Arterial Velocity at Low Radiation Dose Rates.

Quantitative digital subtraction angiography (qDSA) has been proposed to quantify blood velocity for monitoring treatment progress during blood flow altering interventions. The method requires high frame rate imaging [~ 30 frame per second (fps)] to capture temporal dynamics. This work investigates performance of qDSA in low radiation dose acquisitions to facilitate clinical translation. Velocity quantification accuracy was evaluated at five radiation dose rates in vitro and in vivo. Angiographic technique ranged from 30 fps digital subtraction angiography ( at the interventional reference point) down to a 30 fps protocol at 23% higher radiation dose per frame than fluoroscopy ( ). The in vitro setup consisted of a 3D-printed model of a swine hepatic arterial tree connected to a pulsatile displacement pump. Five different flow rates (3.5-8.8mL/s) were investigated in vitro. Angiography-based fluid velocity measurements were compared across dose rates using ANOVA and Bland-Altman analysis. The experiment was then repeated in a swine study (n = 4). Radiation dose rate reductions for the lowest dose protocol were 99% and 96% for the phantom and swine study, respectively. No significant difference was found between angiography-based velocity measurements at different dose rates in vitro or in vivo. Bland-Altman analysis found little bias for all lower-dose protocols (range: [- 0.1, 0.1]cm/s), with the widest limits of agreement ([- 3.3, 3.5]cm/s) occurring at the lowest dose protocol. This study demonstrates the feasibility of quantitative blood velocity measurements from angiographic images acquired at reduced radiation dose rates.

Towards chemical source tracking and characterization using physics-informed neural networks

This paper presents a new algorithm using physics-informed neural networks (PINNs) to track and characterize spatio-temporally varying chemical sources based on time-resolved measurements of chemical concentration, fluid velocity, and pressure. Chemical source emission functions, chemical concentration, fluid velocity and fluid pressure fields are modeled as multi-layer perceptrons (MLPs). During the training process, sensors readings of chemical concentration, fluid velocity, and fluid pressure are matched to the output of the respective MLPs at the given spatio-temporal locations. Simultaneously, the physics of fluid flow and chemical dispersion at an arbitrary number of spatio-temporal locations in the domain of interest are enforced through regularization. Once trained, the constituent MLPs can be evaluated to generate the time resolved maps of source emissions, chemical concentration, fluid velocity and pressure. Extensive numerical simulation validate the method, including scenarios with both static and dynamic sources in complex flow fields. This innovative approach marks a significant advancement in environmental monitoring technologies.

Model discovery approach enables noninvasive measurement of intra-tumoral fluid transport in dynamic MRI.

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a routine method to noninvasively quantify perfusion dynamics in tissues. The standard practice for analyzing DCE-MRI data is to fit an ordinary differential equation to each voxel. Recent advances in data science provide an opportunity to move beyond existing methods to obtain more accurate measurements of fluid properties. Here, we developed a localized convolutional function regression that enables simultaneous measurement of interstitial fluid velocity, diffusion, and perfusion in 3D. We validated the method computationally and experimentally, demonstrating accurate measurement of fluid dynamics in situ and in vivo. Applying the method to human MRIs, we observed tissue-specific differences in fluid dynamics, with an increased fluid velocity in breast cancer as compared to brain cancer. Overall, our method represents an improved strategy for studying interstitial flows and interstitial transport in tumors and patients. We expect that our method will contribute to the better understanding of cancer progression and therapeutic response.

Thermal Optical Fiber Sensor Based on GaAs Film for Fluid Velocity Measurement

Thermal Optical Fiber Sensor Based on GaAs Film for Fluid Velocity Measurement

Interstitial fluid transport in cortical bone porosities: Effects of blood pressure and mass exchange using porous media theory

This research focuses on the importance of understanding bone adaptation for gaining insights into diseases such as osteoporosis. The study investigates the role of fluid flow in cortical bone adaptation, with a specific focus on the network of osteocyte canaliculi and the chemical reactions involved in bone resorption. Prior studies have implemented methods such as poroelasticity theory and dual porosity, but these models did not account for mass exchange between the solid and fluid phases within the bone or the pressure exerted by arteries. The movement of interstitial fluid between the vascular porosity and lacuno-canalicular porosity in cortical bone, as well as the velocity of the fluid, are affected by both the pressure exerted by arteries and the exchange of mass between the solid and fluid components of the bone. To incorporate these effects in the model, the authors propose a dual porosity model based on the theory of porous media. The model considers the transfer of mass between vascular and lacunar-canalicular porosities, as well as between solid and fluid phases, while also accounting for blood pressure variations. To verify the proposed model, a numerical example is solved and compared with the results of previous studies. The model enables the measurement and analysis of the interstitial fluid velocity and the pressure in the respective porosities. The results reveal that accounting for blood pressure pulses and mass exchange between solid and fluid phases can alter the velocity and pressure fields of interstitial fluid within cortical bone. In addition, this study investigates transient examples and various scenarios of the bone remodeling. Overall, this research provides a more accurate understanding of the bone remodeling and the effects of blood pressure variation and mass exchange between solid and fluid phases of cortical bone.

Blowout Fluid Velocity Measurement Method based on High-speed Sequence Images

Given the high-temperature and high-pressure environment after the blowout, the staff usually cannot calculate and analyze various blowout parameters at close range and thus take effective measures to control accidents quickly. In this paper, a blowout fluid velocity measurement method is proposed based on high-speed sequence images, and simulation experiments are conducted. The scene conditions of blowout accidents are simulated and analyzed. On this basis, cameras are adopted to shoot a large number of simulated blowout fluid videos from different angles under outdoor conditions. Afterward, the video is converted into a multi-frame image, and the blowout fluid image feature point detection and extraction model are established based on the orb (oriented fast and rotated brief) algorithm. On the feature points extracted by the model, the gms algorithm is used to match the features of the blowout fluid images in the front and back frames. Additionally, the wrong matching points are eliminated using the ransac (random sample consensus) algorithm, and the obtained feature point pairs are employed into the flow velocity calculation model for flow velocity calculation. The results demonstrate that the measured fluid velocity is more accurate. The method proposed in this study can provide reliable data support for early blowout emergency rescue.

Laser Velocimetry for the In Situ Sensing of Deep-Sea Hydrothermal Flow Velocity.

Laser Doppler velocimetry (LDV) based on a differential laser Doppler system has been widely used in fluid mechanics to measure particle velocity. However, the two outgoing lights must intersect strictly at the measurement position. In cross-interface applications, due to interface effects, two beams of light become easily disjointed. To address the issue, we present a laser velocimeter in a coaxial arrangement consisting of the following components: a single-frequency laser (wavelength λ = 532 nm) and a Twyman-Green interferometer. In contrast to previous LDV systems, a laser velocimeter based on the Twyman-Green interferometer has the advantage of realizing cross-interface measurement. At the same time, the sensitive direction of the instrument can be changed according to the direction of the measured speed. We have developed a 4000 m level laser hydrothermal flow velocity measurement prototype suitable for deep-sea in situ measurement. The system underwent a withstand voltage test at the Qingdao Deep Sea Base, and the signal obtained was normal under a high pressure of 40 MPa. The velocity contrast measurement was carried out at the China Institute of Water Resources and Hydropower Research. The maximum relative error of the measurement was 8.82% when compared with the acoustic Doppler velocimeter at the low-speed range of 0.1-1 m/s. The maximum relative error of the measurement was 1.98% when compared with the nozzle standard velocity system at the high-speed range of 1-7 m/s. Finally, the prototype system was successfully evaluated in the shallow sea in Lingshui, Hainan, with it demonstrating great potential for the in situ measurement of fluid velocity at marine hydrothermal vents.

Influence of travelling waves on the fluid dynamics of a beam submerged in water

Inspired by the use of travelling waves for propulsion mechanisms adopted by many animals and organisms, this paper investigates the mechanism with which travelling waves in beam-like structures induce velocity in a surrounding fluid. This work focuses on the flow induced around the beam tip and provides an experimental characterisation of the phenomena. A test rig equipped with Laser Doppler Anemometry (LDA) is used to investigate the induced fluid velocity and its dependency on the modal response of the beam. Numerical simulations are performed to complement the experimental tests and provide further insight into the fluid–structure interaction. The numerical model also allows for the beam vibration envelope and vibration patterns to be obtained and correlated with the measured fluid velocity. Several geometrical variations are considered in the analysis over a range of frequencies that encompass resonant responses up to the fourth mode. The results showed that the fluid flow is only marginally affected by the change in the vibration pattern between the first-two resonant mode; the induced fluid velocity and, hence, the thrust are mostly driven by the tip velocity of the beam.

Four-wire orthogonal structure for accurate measurement of fluid velocity and wind flow direction using silicon micro-machining on silicon nitride membranes

Four-wire orthogonal structure for accurate measurement of fluid velocity and wind flow direction using silicon micro-machining on silicon nitride membranes

4-dimensional local radial basis function interpolation of large, uniformly spaced datasets

Background and ObjectiveLarge, uniformly spaced, complex and time varying datasets derived from high resolution medical image velocimetry can provide a wealth of information regarding small-scale transient physiological flow phenomena and pulsation of anatomical boundaries. However, there remains a need for interpolation techniques to effectively reconstruct a fully 4-dimensional functional relationship from this data. This paper presents a preliminary evaluation of a 4-dimensional local radial basis function (RBF) algorithm as a means of addressing this problem for laminar flows. MethodsA 4D interpolation algorithm is proposed based on a Local Hermitian Interpolation (LHI) using a combination of multi-quadric RBF with a partition of unity scheme. The domain is divided into uniform sub-systems with size restricted to immediately neighbouring points. The validity of the algorithm is first established on a known 4D analytical dataset and a CFD based laminar flow phantom. Application is then demonstrated through characterisation of a large 4D laminar flow dataset obtained from magnetic resonance imaging (MRI) measurements of cerebrospinal fluid velocities in the brain. ResultsPerformance of the algorithm is compared to that of a quad-linear interpolation, demonstrating favourable improvement in accuracy. The technique is shown to be robust, computationally efficient and capable of refined interpolation in Euclidean space and time. Application to MR velocimetry data is shown to produce promising results for the 4D reconstruction of the transient flow field and movement of the fluid boundaries at spatial and temporal locations intermediate to the original data. ConclusionThis study has demonstrated feasibility of an accurate, stable and efficient 4-dimensional local RBF interpolation method for large, transient laminar flow velocimetry datasets. The proposed approach does not suffer from ill-conditioning or high computational cost due to domain decomposition into local stencils where the RBF is only ever applied to a limited number of points. This work offers a potential tool to assist medical diagnoses and drug delivery through better understanding of physiological flow fields such as cerebrospinal fluid. Further work will evaluate the technique on a wider range of flow fields and against CFD simulation.

Simultaneous measurement of microscale fluid viscosity, temperature, and velocity fields by tracking Janus particle on microparticle image velocimetry

Multifunctional sensing capability enables a comprehensive understanding of the unknown target to be measured. Given that fluid viscosity, temperature, and velocity fields are usually coupled parameters in a system, simultaneous measurement of the three environmental factors can prevent cross-talk and improve reliability. However, the task is apparently challenging because of the microscale targets. A technique combining microparticle image velocimetry and Janus particles was developed in this study to address such demand. With the rotational diffusivity and particle trajectories measured by the proposed technique and an empirical water-based viscosity-temperature relationship, the three unknown variables in a microfluidic environment were solved. The blinking frequency was derived using the Hilbert Huang Transform. Compared with those in a static and uniform temperature field, the measured data had good agreement with the predicted values. However, the agreement was impaired when the heating rate exceeded 0.34 °C/s. The optimal temperature range was found between 10 °C and 40 °C in the water-based solution. For a steady-state and nonuniform temperature field, two-dimensional (2D) numerical simulations of three linear temperature gradients were also studied. Results showed that the deviation increased as the temperature gradient increased or was near the low-temperature region. The same procedure was eventually applied to a real thermophoretic flow induced by an IR laser in a microchip. The 2D fluid viscosity, temperature, and velocity fields in the microchip were successfully obtained by tracking 10 particles. The potential of the approach provides insight into understanding some microfluidic applications with mild changes in temperature or creeping flow. This study combined µPIV with Janus particles to achieve simultaneous measurement of 2D microscale fluid viscosity, temperature, and velocity fields. By simply tracking the particles, particle trajectories and blinking signal were obtained. Both parameters provided sophisticated information of particle velocity and rotational diffusivity. With the information, the viscosity and temperature were hence derived from the empirical viscosity–temperature relationship and the Stokes-Einstein-Debye relation. The velocity was derived alone based on the conventional cross-correlation algorithm. • Using Janus particles as tracers to provide dynamic information of blinking signal and trajectories. • Simultaneous measurement of whole field fluid viscosity, temperature, and velocity at the microscale. • Extraction of the frequency spectrum out of blinking signal by Hilbert Huang Transform. • A measurable temperature range between 10 °C and 40 °C.

Flow Visualization of Transition From Linear to Nonlinear Flow Regimes in Rock Fractures

AbstractThis study made the first experimental attempt to visualize the transition processes from linear to nonlinear flow regimes in rough‐walled rock fractures for a better understanding of the evolution of flow regimes in rock fractures. The experiments visualized the narrowing of the mainstream channel associated with eddies enlarged near the fracture wall with increasing applied flux. The measured fluid velocity field showed that these flow structures resulted in a significant increase in fluid velocity in the narrowed main flow channel and a relatively small velocity in the enlarged eddy zone. The order‐of‐magnitude analysis of local inertial and viscous forces, using measured fluid velocity vectors, showed that inertial forces overwhelmed viscous forces in the narrowed mainstream channel of rough‐walled segments, which led to the transition to nonlinear flow in rough‐walled fractures. The quantitative comparison between measured fluid velocity and the numerical simulations showed good agreement. This study demonstrates that the micro‐PIV technique can serve for phenomenon‐based experimental research on fluid flow and solute transport in rock fractures.

Design, modelling and simulation of a thermosiphon photobioreactor for photofermentative hydrogen production

Currently, most photobioreactors have been designed for cyanobacteria and green algae with comparatively few designed for photofermentative hydrogen production by purple non-sulphur bacteria. Photofermentation experiments are time-consuming and expensive, driving the development of alternative methods for the design of photobioreactors. In this study, computational fluid dynamics (CFD) was used (ANSYS® software package, 2019 R) to design two new thermosiphon photobioreactor (TPBR) configurations for the application of photofermentative hydrogen production by Rhodopseudomonas palustris. The TPBR designs (tubular loop and flat-plate) were simulated and evaluated based on temperature profiles, fluid flow and radiation distribution. Under constant illumination, both reactor designs displayed simulated temperatures suitable for R. palustris as well as achieved fluid velocities exceeding the settling velocity of R. palustris cells; however, both these designs also displayed significant light attenuation. The CFD simulation results were verified by experimental measurements of temperature (< 2.5% error) and fluid velocity (47% error) in a prototype TPBR. Collectively, both the proposed TPBR designs were found to be suitable for photofermentative hydrogen production by R. palustris, with the tubular loop design slightly outperforming the flat-plate in terms of fluid velocity. Furthermore, the proposed CFD method was found to be suitable for the design of photobioreactors, with simulated results closely mimicking their experimentally measured counterparts.

The use of PIV methods in the study of two-phase flows in small diameter channels

The PIV (Particle Image Velocimetry) method is one of the optical, non-invasive measurement methods for measuring fluid velocity and can be used in the study of two-phase gas-liquid flows to determine velocity fields. The velocity distribution of the liquid and gas phases influences the formation of two-phase flow structures and, consequently, the mechanisms of energy and moment exchange in the two-phase flow. The article concerns the application of the PIV method to the assessment of hydrodynamic phenomena occurring during two-phase flow realized in pipe minichannels with an internal diameter d &gt; 2 mm. Fluorescent marker particles with a density close to that of water were used in the research. The preliminary tests were carried out on the adiabatic water-air mixture. The research aimed to check the applicability of PIV methods also in non-adiabatic flows. As a result of preliminary studies, velocity maps of the liquid phase, histograms and velocity profiles in the vertical section of the tested minichannel were obtained.

Multilayer microfluidic platform for the study of luminal, transmural, and interstitial flow

Efficient delivery of oxygen and nutrients to tissues requires an intricate balance of blood, lymphatic, and interstitial fluid pressures (IFPs), and gradients in fluid pressure drive the flow of blood, lymph, and interstitial fluid through tissues. While specific fluid mechanical stimuli, such as wall shear stress, have been shown to modulate cellular signaling pathways along with gene and protein expression patterns, an understanding of the key signals imparted by flowing fluid and how these signals are integrated across multiple cells and cell types in native tissues is incomplete due to limitations with current assays. Here, we introduce a multi-layer microfluidic platform (MμLTI-Flow) that enables the culture of engineered blood and lymphatic microvessels and independent control of blood, lymphatic, and IFPs. Using optical microscopy methods to measure fluid velocity for applied input pressures, we demonstrate varying rates of interstitial fluid flow as a function of blood, lymphatic, and interstitial pressure, consistent with computational fluid dynamics (CFD) models. The resulting microfluidic and computational platforms will provide for analysis of key fluid mechanical parameters and cellular mechanisms that contribute to diseases in which fluid imbalances play a role in progression, including lymphedema and solid cancer.

On expression of Doppler frequency shift in material medium and related theories

In practice of fluid velocity measurement by using laser Doppler velocimetry (LDV), the applied expression of Doppler frequency shift (EDFS) abruptly relates to an unusual coordinate transformation matrix (CTM) instead of a Lorentz transformation matrix. Here we shall demonstrate that, drawing lessons from general relativity and Fermat’s principle, modifying the interval by adopting optical path to replace space distance, the unusual CTM and practicable EDFS mentioned above can be obtained rationally, and other related electromagnetic topics arising in media may be addressed from a new angle. This work indicates that fluid velocity measurement by using LDV can be applied to examine applicability of EDFSs and related theories, which may be helpful to deepen the understanding of foundations of relativity.

Investigation of the flow structure in three-dimensional waves on falling liquid films using light field camera

Fluid velocity measurement in liquid films is a challenging task due to the small film thickness and large transverse gradients of velocity. While this problem was solved for the case of two-dimensional waves by several research groups, measurements in three-dimensional waves impose additional difficulties that we managed to overcome in the course of this study. We used a single light field camera for simultaneous particle tracking velocimetry and laser-induced fluorescence film thickness measurements. In this way, obtained velocity fields were related to the wavy interface shape. The applicability of the proposed methodology was demonstrated in the test experiments, which were carried out for two-dimensional regular waves. Measurements in three-dimensional waves were performed for the fluids with different viscosities and surface tensions but with close values of the Kapitsa number. In all investigated cases, the flow structure in different parts of waves is similar. Comparison of the experimentally obtained velocity fields with calculations by weighted residual integral boundary layer model shows qualitative agreement.

Three-dimensional turbulence generated homogeneously by magnetic particles

Three-dimensional (3D) turbulence is often studied experimentally in closed containers with energy injected at a large scale from a container boundary. We conduct an experiment with remotely driven small magnetic particles to force fluid in volume, randomly in space and time. Such a forcing, like many direct numerical simulations, generates stationary, homogeneous and isotropic turbulence with almost no mean flow, as characterized by fluid velocity measurements. Different methods are used to estimate the energy dissipation rate consistently. We experimentally confirm Tennekes prediction for 3D turbulence without mean flow, and resolve conflicts among previously suggested values of Tennekes' constant.