Search

The compromise between inclusions removal by small bubbles and proper agitation of fluid flow in tundish by gas blown is challenging. The single‐strand tundish without flow control devices (bare tundish) is used to study the effects of side‐wall gas blowing on the flow field. The water model, particle image velocity measurement and computational fluid dynamics simulation are used to study bubble behavior, fluid flow field, and tracer transport. A large horse shoe vortex and a short circuit flow at the bottom are formed in the bare tundish. Gas blowing at the outlet‐side wall of the tundish creates multiple vortices in the right‐side region, with blowing rate and position greatly influencing the surface flow within the tundish. Gas blowing at the front‐side wall creates a large spiral vortex, agitating the fluid in the tundish and improving the flow field. Increasing the blowing rate strengthens the vortex in the right region, but raising the blowing position affects surface flow and creates a counterclockwise flow toward the shroud. In all schemes, gas blowing at a low position on the front‐side wall with a small gas flowrate is the optimized scheme which shows the smallest dead volume and enhances surface flow. [ABSTRACT FROM AUTHOR]

Purpose: 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. Materials and Methods: Velocity quantification accuracy was evaluated at five radiation dose rates in vitro and in vivo. Angiographic technique ranged from 30 fps digital subtraction angiography ( 29.3 ± 1.7 mGy / s at the interventional reference point) down to a 30 fps protocol at 23% higher radiation dose per frame than fluoroscopy ( 1.1 ± 0.2 mGy / s ). 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 (3.5–8.8 mL/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). Results: 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. Conclusions: This study demonstrates the feasibility of quantitative blood velocity measurements from angiographic images acquired at reduced radiation dose rates. [ABSTRACT FROM AUTHOR]

In the present research article, we address the magnetically controlled thermal and solutal Marangoni convection in the ow of self-rewetting power-law liquid over a disk, in the existence of a space dependent heat source. The self re-wetting property of fluid is modelled by considering a quadratic dependence of surface tension on temperature and species concentration. The aforementioned problem is modelled by simplified Navier- Stokes equations. Identifying the appropriate transform variables is essential for developing ordinary differential equations from original partial differential equations that describe the ow conditions. The resulting ordinary differential equations are solved by using the bvp4c routine of MATLAB and numerical solutions are presented via graphs and tables, illustrating the impact of several factors on fluid velocity, temperature, and concentration. Computation of the quantities of physical interest such as Nusselt and Sherwood numbers are also done from those numerical solutions. One of the key findings of present research work is that the Marangoni convection works differently for pseudo-plastic fluid and dilatant fluid. On increasing thermal Marangoni convection the temperature of dilatant fluid reaches a peak value much closer to the disk than temperature of pseudo plastic fluid. [ABSTRACT FROM AUTHOR]

We present a numerical study for Poiseuille and Couette as well as Taylor- Couette swirling flows. The governing equations of momentum and energy are transformed into coupled and nonlinear ordinary differential equations using similarity transformation and then solved numerically. We critically evaluate the effect of dimensionless pressure gradients on fluid velocity and observed that the velocity increases as the dimensionless pressure gradient increases. Couette flows are simulated in different scenarios, including top plate moving, bottom plate moving, and top plate moving in adverse pressure gradient conditions. In a third scenario, the flow velocity profile revealed a backflow regime (BFR). A simple schematic model is, therefore, proposed to explain the presence of BFR in the flow's profile. Numerical and analytical solutions around the circular cylinder are presented. The marginal discrepancy between the analytical and numerical profiles is maximum at ~ 900 and 270° degrees, which indicates that the chosen method is suitable and capable of reproducing engineering problems. Velocity magnitude and vector diagrams show that the cylinder shape was found to have a significant effect on the flow field. The velocity at the top and bottom of the cylinder is twice the velocity that seen away from the cylinder. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Various velocity measurements techniques for fluid dynamics experiments have been developed over the last four decades. These include Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV), both of which rely on imaging the flow with passive particles. While these techniques now allow for an accurate determination of velocity fields at high particle densities, they still suffer from significant inaccuracies when it comes to measurements near boundaries, due to smaller particle concentrations and imaging difficulties in these regions. To improve such measurements, we developed a correction technique for measured velocity fields. Using a PTV approach, we reconstructed the 3D velocity field from an experimental setup designed to study Rayleigh–Bénard convection in a tank. We corrected the obtained velocity field to ensure its accurate, rigid boundary conditions corresponding to the tank walls, while keeping the flow divergence-free. We then assessed the quality of the corrected velocity fields by comparing them with the outputs of 3D numerical simulations that reproduced the precise experimental conditions. The experimentally obtained divergence-free velocity fields with exact boundary conditions compare well with the results of the numerical simulations, which validates our approach. Using synthetic images, we estimated that our corrected fields are in better agreement with numerical simulations (Pearson coefficient R = 0.96 ) than the raw measured fields (Pearson coefficient R = 0.91 ). We find that at high Reynolds numbers, our results can be described by scaling laws that are consistent with previous results from the literature. The correction technique could be useful for a wide range of fluid dynamics experiments where accurate measurements near the walls are needed. These include the advection of passive tracers, where the boundary conditions need to be exact, or turbulence measurements, where the flow gradient at the walls must be precisely determined. [ABSTRACT FROM AUTHOR]

An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study. Mechanical properties of MFG porous plates change according to the length, width, and thickness directions for various materials and the porosity distribution which can be widely applied in many fields of engineering and defence technology. Especially, new porous rules that depend on spatial coordinates and grading indexes are proposed in the present work. Applying Hamilton's principle and the refined higher-order shear deformation plate theory, the governing equation of motion of an MFG porous rectangular plate in a fluid medium (the fluid-plate system) is obtained. The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to compute the extra mass. The Galerkin- Vlasov solution is used to solve and give natural frequencies of MFG porous plates with various boundary conditions in a fluid medium. The validity and reliability of the suggested method are confirmed by comparing numerical results of the present work with those from available works in the literature. The effects of different parameters on the thermal vibration response of MFG porous rectangular plates are studied in detail. These findings demonstrate that the behavior of the structure within a liquid medium differs significantly from that within a vacuum medium. Thereby, they offer appropriate operational approaches for the structure when employed in various mediums. [ABSTRACT FROM AUTHOR]

An exploration is carried out to examine mass diffusion of unsteady 'boundary layer' (bl) motion of viscous liquid passed a stretched leaky piece with variable mass flux. For several engineering applications, moving free stream is considered here. This makes this research unique. The leading 'partial differential equations' (PDEs) accompanied by the 'boundary conditions' are converted to 'ordinary differential equations' (ODEs) with the help of 'similarity transformations' and 'numerical solutions' are attained by MATLAB software. The effect of pertinent 'parameters' on fluid 'flow, concentration, skin friction coefficient' and wall concentration are discussed 'graphically' and numerically. When suction/blowing parameter increases from -0.2 to 0.2, skin friction coefficient decreases 18.235%. Fluid concentration reduces with growing values of velocity ratio parameter X for all cases considered. Compared to the case for static free stream, fluid velocity is higher when the free stream moves. Also higher concentration is noted in presence of moving free stream. The presence of moving free stream causes to diminish the effect of suction/blowing on flow and concentration fields. The increasing strength of suction causes to decrease the fluid velocity more significantly than that for blowing. [ABSTRACT FROM AUTHOR]

Since the 1930s, theories of skin-friction drag from plates with rough surfaces have been based by analogy to turbulent flow in pipes with rough interiors. Failure of this analogy at small fluid velocities has frustrated attempts to create a comprehensive theory. Utilizing the concept of a self-similar roughness that disrupts the boundary layer at all scales, this investigation derives formulas for a rough or smooth plate's skin-friction coefficient and forced convection heat transfer given its characteristic length, root-mean-squared (RMS) height-of-roughness, isotropic spatial period, Reynolds number, and the fluid's Prandtl number. This novel theory was tested with 456 heat transfer and friction measurements in 32 data-sets from one book, six peer-reviewed studies, and the present apparatus. Compared with the present theory, the RMS relative error (RMSRE) values of the 32 data-sets span 0.75% through 8.2%, with only four data-sets exceeding 6%. Prior work formulas have smaller RMSRE on only four of the data-sets. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Accurate and real-time measurement of fluid flow velocity is crucial in various industrial processes, especially when dealing with multiple phase fluids. Traditional flow measurement methods often struggle to accurately quantify the velocity of complex multiphase flows within pipes. This challenge necessitates the exploration of innovative techniques capable of providing reliable measurements. This paper proposes the utilization of Electrical Capacitance Tomography (ECT) as a promising approach for measuring the velocity of multiple phase fluids in pipes. The ECT technique involves the non-intrusive imaging of the electrical capacitance distribution within the pipe. By utilizing an array of electrodes placed around the pipe circumference, the capacitance distribution can be reconstructed, offering insight into the fluid flow patterns. By analyzing the temporal changes in the capacitance distribution, the velocity of different phases within the pipe can be estimated. To achieve accurate velocity measurements, an ECT system needs to account for the complexities introduced by multiphase flows. Various image reconstruction algorithms, such as linear back-projection and iterative algorithms like Gauss-Newton and Levenberg-Marquardt, are employed to reconstruct the capacitance distribution. Additionally, advanced signal processing techniques, such as cross-correlation analysis and time-difference methods, are used to extract velocity information from the reconstructed images. This paper presents an experimental investigation of measuring the velocity of multiple-phase fluids in pipes using the ECT technique. The study aims to address the challenges associated with different flow regimes, fluid properties, and pipe geometries by exploring advancements in electrode design, system calibration, and data processing techniques to enhance the accuracy and robustness of ECT-based velocity measurements. [ABSTRACT FROM AUTHOR]

In the petroleum and natural gas industry, a wide variety of multiphase fluids are prevalent, and precise measurement of their flow velocity in pipelines holds significant importance for different stages of well drilling and construction. However, due to the presence of large solid particles and the corrosive nature of the liquid phase in multiphase fluids within the petroleum industry, invasive measurement methods struggle to maintain long-term acceptable detection accuracy. Therefore, the non-contact fluid flow velocity measurement method based on ultrasonic sensors exhibits substantial research value. Nonetheless, when employing this approach for pipeline multiphase fluid flow velocity measurement, the abundance of background interference noise at the site poses challenges in Doppler echo signal reconstruction and results in lower precision for frequency shift extraction, leading to considerable errors in flow velocity calculation results. To address this issue, the present study utilizes a transmit-receive separated continuous wave ultrasonic sensor. First, a mathematical model is developed for the superimposed signal of ultrasonic Doppler echoes within the pipeline. Next, a novel signal reconstruction method is proposed by employing Chebyshev polynomials for interpolation computation of the sampled discrete signals. Subsequently, a Doppler shift model is introduced, leading to the formulation of a new model for multiphase flow velocity calculation in pipelines based on ultrasonic sensors. Finally, a comparison experiment for full-pipe multiphase flow velocity detection is conducted to validate the computational performance of the new model. The experimental results show that, compared with the FFT model and the conventional cross correlation model, the comprehensive meter factor of the ultrasonic flow measurement system with the new model is reduced by 0.024 445, the accuracy is reduced by 2.98%, the nonlinear error is reduced by 2.4405%, the average relative error is reduced by 0.646%, the standard deviation is reduced by 0.045 175, and the root mean squared error is reduced by 0.029 615. [ABSTRACT FROM AUTHOR]

In this paper, the effects of various fluid properties on two-dimensional unsteady biomagnetic fluid flow (blood) and heat transfer over a stretching sheet under the appearance of a magnetic dipole is investigated. The governing boundary layer equations are simplified via suitable transformation which are then solved using the bvp4c function approach in MATLAB software. The results indicate that fluid velocity and temperature are greatly influenced by the ferromagnetic interaction parameter. With increasing ferromagnetic number, fluid velocity drops but temperature increases. It is also found that the coefficient of skin friction and Nusselt number increase with an increase in values of thermal conductivity parameter. For certain parameter values, the results are also compared with previously published studies and they are found to be in acceptable agreement. [ABSTRACT FROM AUTHOR]

Ultrasonic Velocity Profiler (UVP) provides velocity measurement along a line and is also applicable to flow fields which are optically inaccessible. The capability of UVP was extended from line measurement of velocity to pressure measurement in fluid flows (Tiwari and Murai in Exp Fluids 62:1–17, 2021). However, the position of UVP transducer was chosen rather arbitrarily, and no study has yet been conducted for the optimization of the location of UVP transducer in two-dimensional flows. In this study, a novel determinant greedy line selection method (DGLSM) is developed for the selection of the position of the ultrasonic transducer for effective measurement from UVP in two-dimensional fluid flows. The concept of line selection algorithm is motivated from sensor selection method (Manohar in IEEE Control Syst 38: 63–86, 2018; Saito et al in IEEE Access 9: 68535–68551, 2021). The present DGLSM algorithm provides the optimized lines for velocity measurement by UVP. The number of UVP lines and locations were optimized by analyzing their flow reconstruction capability. The demonstration of algorithm is performed in experimental velocity data of flow over cylinder. It was found that when the number of measurement lines becomes equal to the number of Proper Orthogonal Decomposition modes, the reconstruction accuracy becomes excellent. [ABSTRACT FROM AUTHOR]

Leakage occurring in the tube sockets of the main steam thermometers can seriously threaten the safe operation of coal-fired power plants. Here, assuming a 300 MW unit as a relevant testbed, this problem is investigated numerically through solution of the equations of fluid-dynamics in synergy with the mathematical treatment of relevant statistics. The results indicate that the steam can form a large-scale spiral flow inside the tube socket and continuously scour the inner wall. In the model with the protective casing setting angle of 60°, the average tangential fluid velocity can reach up to 4.8 m/s, which is about twice higher than that in the model with the protective casing setting angle of 0°. The wake disturbance generated by the flow around the thermo-sensitive body leads to differences in the fluid motion inside the tube sockets between the upstream and downstream thermometers. These differences are affected by the distance between the thermometers, the setting angle of protective casing, and other factors. The pressure of the main steam inside the tube socket for a R3 thermometer, located outside the curved pipeline, is about 1756 Pa higher than that of the L3 thermometer located outside the straight pipeline, indicating that the secondary flow generated in the curved pipeline is able to provide stronger energy for the large-scale spiral flow inside the tube socket. On the basis of these findings, an improvement scheme for the installation of longitudinal ribs in the tube sockets is proposed. The simulation results show that the average tangential velocity of the fluid within the near-wall area of tube sockets decreases by more than 90%, which should be enough to effectively alleviate the damage to the inner wall caused by high-pressure fluid or particles. [ABSTRACT FROM AUTHOR]

A considerable analysis has been performed to draw out the flow properties of MHD Casson fluid in parabolic movement with several parameters. The novelty in the examination is the angle of inclination with the permeable vertical plate. The purpose of the work is to analyze the impact of some parameters on the flow in two cases namely, obtuse angle and acute angle. The solution of the flow governed equations is attained by the utilization of the finite divergence technique in explicit type. The nature of the fluid velocity is observed in the cases of acute angle and obtuse angle and described accordingly with the use of graphs and tables. One of the major findings is that for increasing values of porosity the velocity enhances in the case of acute angle and falls down in the case of obtuse angle. [ABSTRACT FROM AUTHOR]

This study presents the flow of Hibiscus Sabdariffa Roselle (Sobo), Soymilk (Soya), and Pap (Ogi) through a modeled intestine. Experimental and Computational Fluid Dynamics (CFD) techniques were employed, while Autodesk Inventor 2020 version was used to draw the 3D computational model of the human intestine. ANSYS Fluent 16.0 was utilized as a CFD solver. Deformed boundary walls of the Navier-stokes equations of fluid flow were used for modeling. The results showed that fluid velocity, pressure, density, and viscosity significantly affected the flow behavior of nutrients in the intestinal walls. The density and viscosity of the investigated fluids ranged between 800-1024 kg/m3 and 0.316-1.095 Pas, respectively, while the maximum and minimum viscosities were observed with Ogi and Sobo, respectively. The highest drop in the velocity along the whole length of the intestinal model ranged between 0.8 and 1.5 m, which corresponded to the pulsating section of the model. The maximum and minimum Reynolds numbers were recorded with Sobo and Ogi samples, respectively. To ensure effective flow and avoid complications when taking food supplements, a flow velocity of 0.005 m/s is recommended. The presence of villi in the intestinal wall augmented heat transfer. [ABSTRACT FROM AUTHOR]

This 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. Plain Language Summary: The Darcy‐type equations have been used to quantify fluid flow through rock fractures. These equations are limited to the flow regime that exhibits the linearity between applied pressure gradient and measured flux. However, the breakdown of the linearity takes place in many hydrogeological applications associated with high flowrates, such as geothermal energy extraction, hydrocarbon production, groundwater remediation, and so on. Therefore, this study made the first attempt to visualize the evolution of nonlinear flow through flow visualization and fluid velocity measurement. Experiments observed the narrowing of the mainstream channel associated with eddies enlarged near the fracture wall. The magnitude analysis of measured fluid velocity showed that inertial forces overwhelming viscous forces in narrowed main channel account for nonlinear flow. Flow visualization and analysis demonstrated that fracture roughness determines nonlinear flow characteristics rather than aperture size. The flow visualization technique presented in this study can serve for phenomenon‐based experimental research on fluid flow and solute transport in rock fractures. Key Points: Transition from linear to nonlinear flow regimes are visualized using the micro‐particle image velocimetry for the first timeExperiments observe the narrowing of the mainstream channel associated with eddies near fracture wall with increasing applied fluxFlow visualization and analysis show that inertial forces overwhelming viscous forces in narrowed main channel account for nonlinear flow [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of a solar air collector aiming at analyzing the influence of several geometrical parameters on the heat transfer mechanisms with minimum losses. The laminar airflow in the collector undergoes a sudden or gradual narrowing at the absorber in its path. The finite volume method is used to solve the conservative equations of the fluid flow in the system. The results for these two narrowing models, at different positions and heights, show an improvement in heat transfer and a reduction in friction, especially in the case of gradual narrowing. Both narrowing models reduce the recirculation zones and thus increase the fluid velocity (1.25 to 2.50 times the reference velocity), leading to a gain in pressure drop compared to the perpendicular shoulder case. This solution also increased system efficiency (22.41% to 50.12% for the inclined shoulder case, 21.83% to 48.86% for the perpendicular case, and 20.81% to 38.66% for the simple case). [ABSTRACT FROM AUTHOR]

Dynamic filtration is promising for microalgae harvesting and mitigation of fouling and has been used for various purposes, such as yeast separation, soy milk protein concentration, whey protein microfiltration, etc. This contribution reviews different designs of dynamic filtration systems. It aims to investigate and highlight the potential of dynamic filtration for microalgae harvesting. The performances of individual systems are compared. Dynamic filtration systems can yield permeate flux almost twice higher than systems using cross-flow filtration. Considering the filtration flux and power consumption, the optimal recommended disks for dynamic filtration are those with a gap between the disk and the membrane of 3 mm and disks with two vanes with a cross-sectional area that decreased in the outward direction from the disk center. Disks with two vanes or perforated disks are recommended to achieve a uniform distribution of shear stress along the membrane. Fluid velocity is 2-fold and shear stress 7-fold higher than those obtained for an unperforated disk. Due to the energy demand during dynamic filtration, it is not recommended to use the frequency of disk revolution higher than 1,000 rpm. The shear rate used to mitigate fouling during harvesting of microalgae typically varies between 5,000 to 90,000 s-1 and the shear stress varies between 0.6 to 29 Pa, depending on the design of the dynamic filtration system. In case of vibrating systems, a vibrating frequency of 5 Hz is capable of significantly reducing fouling. [ABSTRACT FROM AUTHOR]

This paper considers a simplified three dimensional Ericksen-Leslie System for nematic liquid crystal flows in the unbounded domain Ω:=R+×R² or the smooth bounded domain Ω. The hydrodynamic system consists of the Navier-Stokes type equations for the fluid velocity coupled with a convective Ginzburg-Landau type equation for the averaged molecular orientation. We first establish the global existence of Sobolev regular solution with finite energies in Sobolev space Hs(Ω)×Hs(Ω), where the index s of the Sobolev space can be any large fixed integer, but s≠+∞. Then we give an asymptotic expansions of a family of Sobolev regularity solutions for such system in Ω. [ABSTRACT FROM AUTHOR]

Turbulence is one of the ubiquitous aspects of aquatic systems and affects many physical and biological processes. Based on direct velocity measurements and a computational fluid dynamics (CFD) simulation, we characterized the distribution of the turbulent kinetic dissipations rates (ε) in an orbital shaker system within a range of rotation frequencies. CFD was able to estimate the ε distribution in containers accurately, which was confirmed by other two methods and was independent of velocity measurement. The results showed that ε was linearly correlated with the rotational frequencies. Despite the existence of gradients of ε and the fact that a mean circular horizontal flow was formed within the tank, the energy levels of the whole tank varied spatially within an order of magnitude and the ε distributions at different rotational frequencies were similar, suggesting that the ε distribution in the whole tank could be seen as quasi-homogeneous. To investigate the influence of turbulence on algae growth, culture experiments of a typical diatom—Skeletonema costatum were carried out under different turbulence conditions. Our results suggested turbulence mixing promoted nutrient uptake and growth of Skeletonema costatum, which could be attributed to the break of the diffusion-limited resource concentration boundary layer surrounding phytoplankton. [ABSTRACT FROM AUTHOR]

This paper for first time proposes an isogeometric analysis (IGA) for free vibration response of bidirectional functionally graded (BDFG) rectangular plates in the fluid medium. Material properties of the BDFG plate change in both the thickness and length directions via power-law distributions and Mori- Tanaka model. The governing equation of motion of BDFG plate in the fluid-plate system is formulated basing on Hamilton's principle and the refined quasi three-dimensional (3D) plate theory with improved function f(z). The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to determine the added mass. The discrete system of equations is derived from the Galerkin weak form and numerically analyzed by IGA. The accuracy and reliability of the proposed solutions are verified by comparing the obtained results with those published in the literature. Moreover, the effects of the various parameters such as the interaction boundary condition, geometric parameter, submerged depth of plate, fluid density, fluid level, and the material volume control coefficients on the free vibration behavior of BDFG plate in the fluid medium are investigated in detail. Some major findings regarding the numerical results are withdrawn in conclusions. [ABSTRACT FROM AUTHOR]

(6) Species transport equation: HT ht Graph (6)where I c i is the tracer concentration, mol/L; HT ht is the effective diffusion coefficient, I D i SB I eff i sb is the effective viscosity coefficient, HT ht and is the turbulent Schmidt number. Keywords: fluid retention zone; heat exchanger; helical flow; RTD EN fluid retention zone heat exchanger helical flow RTD 681 696 16 07/21/22 20220701 NES 220701 1 Introduction The shell and tube heat exchanger (STHX) is dominant in the heat exchanger equipments. [Extracted from the article]

This investigation is carried out to find the momentary behavior of magnetohydrodynamics heat and mass transfer in double-diffusive free convection flow of an electrically conducting, incompressible viscous fluid over a vertical plate with time-exponential heating, constant concentration and first order chemical reaction. The influence of Lorentz force on the fluid motion is considered when the external magnetic field is fixed or it moves together with the plate. Governing partial differential equation of the mathematical model is solved by the Laplace transform method. An interesting property regarding the behavior of the fluid velocity is found when the magnetic field moves with the plate. In this case the fluid velocity is not zero far away of the plate. Particular cases of the plate motion (time-accelerating plate, oscillating plate) are studied. The influence of essential parameters on the fluid motion due to a slowly accelerating plate and the required time to reach the steady-state for oscillating motions are graphically underlined and discussed. Moreover, mechanical, thermal and concentration effects on the fluid motion are separately brought to light. The variation of thermal boundary layer thickness is also presented. [ABSTRACT FROM AUTHOR]

Turbine is a hydraulic engine where energy transfer occurs both based on the kinetic energy and potential (pressure) of the water. In this article we have designed the Spiral Turbine Casing - Impeller assembly with dimensions, geometry from technical documentation forms and the articles of other authors. CAD design of this assembly is a challenge and was done using. NX SIEMENS. The study of the fluid flow was done with ANSYS CFX by importing this assembly, some conclusions were drawn regarding the fluid velocities and the pressure field. The cavitation phenomenon that may occur in the operation of the turbine was also taken into account and some conclusions were drawn regarding the effects of this phenomenon. If the presence of vapours in the hydraulic circuit is found, then the cavitation can develop and this fact can be highlighted with Vapour Volume Fraction. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted to explore the wave trains generated by vertical bed movements. The investigation consisted of 32 cases, involving four different water depths with unimodal and bimodal bed movements. Water surface displacement was measured using gauges positioned along a 30m long tank. A PIV system was set up to provide detailed measurement of the fluid velocity field in the vicinity of the bed movement. Generally, a unimodal movement generated a solitary-like wave, followed by a trailing sequence of waves. A bimodal bed movement induced a more complex flow field, with both the first and second extrema being significant. New analytical solutions have been derived, enabling the calculation of velocity fields. The nature of the wave generation and propagation were characterised using the disturbance-amplitude scale (α) and disturbance-size scale (δ). The applicability of linear theory was investigated, by validating the linear solutions of the generated waves against the experimental observations. For α ≤ 0.25, the analytical solutions were in good agreement with observations of the free surface shape, flow field and wave elevation history. For α ≥ 0.5, non-linearity became more pronounced, and the analytical solutions were only capable of reasonably estimating the amplitude of the first extremum in the vicinity of the moving bed. The initial crest maintained its amplitude and shape more effectively in crest-leading waves, whereas the leading trough decayed significantly in trough-leading waves. Non-linear phenomena were observed, such as wave breaking, air entrapment and twisted free surface. Bimodal bed movements with α ≥ 0.5 generated large, steep crests immediately following the initial trough in trough-leading waves. [ABSTRACT FROM AUTHOR]

Real biological tissues show a great variety of different geometric morphologies with special features on different geometric scales. An interesting example is the liver lobule that is the basic subunit of a liver. The lobule is a quasihexagonal macroscopic structure with periodic like so-called sinusoidal elements with structural features on the micro- and macroscale made of proteins, cells, and fluids. Various tools from micromachining and nanotechnology have demonstrated their capabilities to construct micromorphologies precisely, but even the reconstruction of such a system in technical polymers is challenging. In this work, the rapidly evolving technique of multiphoton polymerization has been explored for the construction of a scaffold that mimics the micromorphology of the liver with high resolution and detail up to the millimeter scale. At the end, a highly complex fluidically perfusable structure was achieved and simulations showed that the occurring shear stress, fluid velocity, and stream lines are comparable to the native liver lobule. Hereby, the photoresists SU-8 and SUEX TDFS were compared in terms of their processability, achievable resolution, and suitability for the intended application. Our results have shown that SUEX needs lower writing velocities but is easier to process and achieves a considerable higher resolution than SU-8. The scaffold could provide a base frame with a geometrically defined morphology for hepatic cells to adhere to, which could act as a starting point for cells to build new liver tissue for further integration in more complex systems. [ABSTRACT FROM AUTHOR]

The article focuses on elastic turbulence generates anomalous flow resistance in porous media. Topics include the many energy, environmental, industrial, and microfluidic processes rely on the flow of polymer solutions through porous media, and the macroscopic flow resistance often increases above a threshold flow rate in a porous medium, but not in bulk solution.

We consider a two-species chemotaxis-Navier-Stokes system with -Laplacian in three-dimensional smooth bounded domains. It is proved that for any , the problem admits a global weak solution. [ABSTRACT FROM AUTHOR]

This paper presents the results of studying the motion of a liquid layer along the walls of a vertically installed pipe under the action of gravity. Two-dimensional boundary layer is formed by the fluid motion relative to the hard wall on surfaces of structures (pipes, turbines, heat-and-mass transfer equipment, aircrafts, ships, etc.), which are of positive interest in engineering practice. Further upgrading of the above-mentioned structures is possible only by increasing accuracy of momentum in the boundary layer, heat and mass transfer rates calculation. It is confirmed that in the boundary layer transfer phenomena intensity (perpendicular to the wall) is due to the fluid particles velocity distribution regularities in the cross-section of the layer. Fluid velocity distribution regularities in turn are conditioned by Reynolds number according to current notions. The principal method of quantitative analysis of turbulent flow in a boundary layer suggested by Reynolds continues to be the velocity and pressure fluctuations averaging method for some timespan. The suggested model of fluid movement enables to prognosticate conditions under which in cross-sections of the boundary layer reshaping of velocity profile takes place, to carry out analytic calculation of such hydrodynamic characteristics as mean velocity of motion, layer thickness and shearing stresses acting on the wall. The difference between the suggested methods developed for calculation of flow parameters from the well-known ones is in that that calculations are made based on an integrated approach regardless of such conceptual definitions as laminar and turbulent regimes widely used in modern hydrodynamics. Obtained results and design formulas known in the literature have been compared. It has been found that the thickness of the sliding layer, determine by the proposed calculation formula, 1.17 times smaller than that determined by the currently used formula. [ABSTRACT FROM AUTHOR]

Introduction: Because the fluid-conveying piping system has a wide range of engineering applications such as mechanical, civil, astronautical and aeronautical engineering and so on, the vibration control is very necessary due to possible damage to the pipe system caused by vibration. This paper presents a vibration reduction scheme of pipeline conveying fluid which can reduce vibration effectively. Objectives: By coupling the Bragg scattering bandgap mechanism with the inertia amplification mechanism, a strategy to enhance the bandgap properties of the periodic non-uniform pipes conveying fluid is proposed. Methods: The band structures for flexural waves in the fluid-conveying periodic non-uniform pipes with periodically distributed inertial amplification mechanisms are determined using the transfer matrix method, and the frequency ranges of the bandgaps and vibration reduction are analyzed. Results: The vibration attenuation capacity of the periodic non-uniform pipes under different fluid velocities, amplification masses and amplification angles is investigated. The bandgaps of the non-uniform pipe conveying fluid with periodic inertial amplification mechanisms obtained by the numerical method are compared with the vibration experiments. The results show that the piping systems with the design of the periodic pipe structures can be effective in reducing vibration. Conclusion: The fluid velocity has slight effect on the band-gap properties of the non-uniform fluid-conveying pipes with periodic inertial amplification mechanisms. The band-gap properties and vibration attenuation performance of the non-uniform fluid-conveying pipes with periodic inertial amplification mechanisms can be enhanced more efficiently by a larger amplification angle and amplification mass. [ABSTRACT FROM AUTHOR]

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as it implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ∼1000GPa is achieved in all cases. These experiments exhibit unexpectedly softer behavior above 200GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum. [ABSTRACT FROM AUTHOR]

Based on high‐resolution laboratory data of instantaneous surface elevation and fluid velocity associated with the propagation of short waves over a gently sloping beach (GLOBEX project), the present work compares two methods for predicting the wave setup. A one‐dimensional (cross‐shore) model is considered to solve the balance equation that links the pressure gradient induced by the mean surface elevation profile with the wave radiation stress (including wave roller) and bottom stress profiles. When compared to measurements and using a wave‐by‐wave approach, the mean elevation appears to be significantly better predicted with a nonlinear approach based on stream function theory than with the commonly used linear approach based on Airy wave theory. At the shoreline, the linear method overestimates the wave setup by at least about 50% while this error is globally reduced by a factor 2 to 4 in the nonlinear case. In the framework of this study, the combined contribution of bottom stress and wave roller to the wave setup appears secondary since it accounts for about 10% of the predicted setup at the shoreline. Alternative computational methods are also considered to model the wave setup. In the linear case, using a spectral instead of the wave‐by‐wave approach greatly improves the wave setup predictions. This improvement is related to the disparity between the representative wave height (and thus the wave energy) obtained from spectral and wave‐by‐wave analysis when short‐wave nonlinearity becomes significant. Plain Language Summary: The breaking of waves near the shore increases the mean sea level to a maximum at the shoreline. This so‐called wave setup is of fundamental importance in coastal dynamics, especially regarding flooding issues during storm events. Here, we use laboratory measurements of surface elevation and fluid velocity associated with waves propagating over a uniform beach to test the validity of wave setup predictions following two different approaches. The first one is based on the basic and common framework within which the waves are always represented by sinusoids, while the second one is based on a more elaborate and realistic representation of waves. We show that using the basic approach significantly overestimates the wave setup, while the more elaborate approach leads to more realistic predictions. Key Points: Laboratory data are used to assess the validity of wave setup predictions following linear and nonlinear approachesIn a wave‐by‐wave analysis wave setup predictions are greatly improved when accounting for short‐wave nonlinearityLinear wave setup predictions are improved using spectral instead of wave‐by‐wave approach due to a correct account of the wave energy [ABSTRACT FROM AUTHOR]

Settling velocity or depositional velocity is considered a key parameter to account for in the drilling technology of oil and gas wells as well as hydrocarbon processing since an accurate estimation of this parameter allows the transport of cuttings efficiently, avoids non-productive time, and helps avoid costly problems. Understanding the settling velocity in fluid with high salinity will help for the better separation of oil and natural gas streams in processing facilities. Although a great amount of effort was given to rheology and settling velocity measurements for power-law fluid and Bingham fluids, there are limited studies available in the literature for Herschel–Bulkley (H–B) fluid with salinity. The present study analyzes the fluid rheology of non-Newtonian fluids with, and without, salinity. Moreover, experiments have been conducted to measure the settling velocity of different diameters of solid particles through Herschel–Bulkley fluids with various salinity conditions. For the rheology analysis, it is found that higher weight percentages of NaCl lead to low values of shear stresses. As well, higher weight percentages of CaCl2 concentration result in a slight increase in shear stresses per a given shear rate. On the other hand, higher percentages of salt concentration cause an increase in the terminal velocity. [ABSTRACT FROM AUTHOR]

The dynamic behavior of an elastic capsule with an initially oblate spheroidal shape during crosstype optical separation was numerically investigated. The penalty immersed boundary method was adopted for the fluid-membrane interaction, and the optical force calculation was conducted by using the ray optics method including the ray-surface intersection algorithm. The oblate elastic capsule of b/a=0.5 with different surface Young's moduli and different initial inclination angles was considered. The oblate capsule with higher surface Young's moduli was less deformed, and was more migrated for each initial inclination angle. Unlike the oblate rigid particle, the initially inclined capsules with moderate inclination angles were similarly migrated since the oblate elastic capsule was deformed during rotation near the laser beam axis. The oblate capsules can be separated according to the surface Young's modulus, except for nearly non-inclined capsules. As the fluid velocity decreased, the migration distance increased. The maximum deformation parameter was insensitive to the fluid velocity. Furthermore, a new dimensionless number (Sec) was introduced to predict the migration distance of the oblate elastic capsule. [ABSTRACT FROM AUTHOR]

Italy has not yet presented to the scientific community any elastocaloric prototype suitable for refrigeration/air conditioning. The SUSSTAINEBLE project was born from the idea to build a demonstrative elastocaloric prototype for environmental conditioning. The prototype is planned to be rotary and composed by a few bunches of elastocaloric wires crossed by air as heat transfer fluid. Many are the parameters to be investigated before the realization of the device. A numerical practical tool would help to easily optimize the prototype. In this paper a two-dimensional tool of a single bunch of elastocaloric wires based on finite-element method is introduced; it can reproduce step by step the velocity and the pressure field of fluid to predict more accurately the solid-to-fluid heat exchange. The results of a test campaign mostly focused on the optimization of the frequency of the cycle, fluid velocity and the distance between the elastocaloric wires are presented. The results reveal that: (i) 0.12 Hz as frequency; (ii) 7 m s-1 as velocity; (iii) 1.0 mm as optimal wire distance, would better satisfy the trade-off existing in the maximization of temperature span and cooling power per mass unit: 23.7 K and 311.97W kg-1 are the values achieved, respectively. [ABSTRACT FROM AUTHOR]

This study is a non-isothermal analysis of the calendering process using a water based nanofluid with Cu -nanoparticles. The basic flow equations are simplified under the lubrication approximation theory (LAT) and non-dimensionalized. Theoretical velocity and pressure gradient solutions are achieved, and temperature distribution is numerically computed by finite difference method. The impact of nanoparticle volume fraction on pressure distribution, fluid velocity, temperature distribution, power input, and separating force are presented through graphs and discussed. Nanoparticle volume fraction enhances the magnitude of pressure, pressure gradient, and temperature distribution. Power input and roll-separating force also rise for higher nanoparticle volume fraction. Model II of dynamic viscosity of nanofluid has a greater impact on physical parameters as compared to the model I of dynamic viscosity. [ABSTRACT FROM AUTHOR]

Background: Phase contrast magnetic resonance imaging, PC MRI, is a valuable tool allowing for non-invasive quantification of CSF dynamics, but has lacked adoption in clinical practice for Chiari malformation diagnostics. To improve these diagnostic practices, a better understanding of PC MRI based measurement agreement, repeatability, and reproducibility of CSF dynamics is needed. Methods: An anatomically realistic in vitro subject specific model of a Chiari malformation patient was scanned three times at five different scanning centers using 2D PC MRI and 4D Flow techniques to quantify intra-scanner repeatability, inter-scanner reproducibility, and agreement between imaging modalities. Peak systolic CSF velocities were measured at nine axial planes using 2D PC MRI, which were then compared to 4D Flow peak systolic velocity measurements extracted at those exact axial positions along the model. Results: Comparison of measurement results showed good overall agreement of CSF velocity detection between 2D PC MRI and 4D Flow (p = 0.86), fair intra-scanner repeatability (confidence intervals ± 1.5 cm/s), and poor inter-scanner reproducibility. On average, 4D Flow measurements had a larger variability than 2D PC MRI measurements (standard deviations 1.83 and 1.04 cm/s, respectively). Conclusion: Agreement, repeatability, and reproducibility of 2D PC MRI and 4D Flow detection of peak CSF velocities was quantified using a patient-specific in vitro model of Chiari malformation. In combination, the greatest factor leading to measurement inconsistency was determined to be a lack of reproducibility between different MRI centers. Overall, these findings may help lead to better understanding for application of 2D PC MRI and 4D Flow techniques as diagnostic tools for CSF dynamics quantification in Chiari malformation and related diseases. [ABSTRACT FROM AUTHOR]

RainbowPIV is a recent imaging technology, proposed for time-resolved 3D-3C fluid velocity measurement using a single RGB camera. It dramatically simplifies hardware setup and calibration procedures as compared to alternative 3D-3C measurement approaches. RainbowPIV combines optical design and tailored reconstruction algorithms, and earlier preliminary studies have demonstrated its ability to extract physically constrained fluid vector fields. This article addresses the issue of limited axial resolution, the major drawback of the original RainbowPIV system. We validate the new system with a direct, quantitative comparison with four-camera Tomo-PIV on experimental data. The reconstructed flow vectors of the two approaches exhibit a high degree of consistency, with the RainbowPIV results explicitly guaranteeing physical properties, such as divergence free velocity fields for incompressible fluid flows. [ABSTRACT FROM AUTHOR]

—The motion of a charged dielectric microparticle in an electric field is first studied over a wide parameter range on the base of the numerical solution of the system of Nernst–Planck–Poisson–Stokes equations. As the most important result, the formation of microvortices on the rear side of the particle is revealed. The microvortices lose their steadiness with increase in the electric field strength and separate periodically from the particle surface. Separation becomes chaotic with further increase in the electric field strength. The phenomenon strongly resembles the formation of the Kármán street but it has another physical mechanism by virtue of almost zero Reynolds numbers of micro- and nanoparticle flow. The asymptotic analysis is carried out and the mechanism of microvortex formation and separation is theoretically substantiated at small Debye numbers. [ABSTRACT FROM AUTHOR]

Accurate sand flow rate measurement is needed to minimize the side effects of sand production in gas fields. There are concerns about the accuracy of sand flow measurement using the sand measuring devices available on the market. In this paper, ultrasonic sensors and discrete wavelet transform signal analysis method is used to measure the sand flow rate. It is found that the strength of the discrete wavelet coefficients in the frequency range of 15–62kHz has a linear relationship with sand flow rate. This finding provides a new methodology to accurately measure sand flow rate. The proposed method does not need fluid velocity as a prerequisite for sand rate measurement, so it greatly simplifies the system design when flow meters are not used for fluid velocity measurement. Also, this method has a much simpler calibration procedure compared to that of the sand detectors commonly used in the industry. [ABSTRACT FROM AUTHOR]