Flow Splitting Research Articles

Experimental investigation of gas-liquid two-phase splitting in parallel pipelines with risers

To study two-phase flow splitting at a T-junction, Parallel vertical riser pipelines were set up in the laboratory. Each of these pipelines was completely symmetrical. The experiment was conducted with various combinations of gas velocity and liquid velocities. Accurate measurement of gas-liquid two-phase flow were performed to determine whether the two-phase flow was evenly distributed in the two riser pipelines. The conductance probe technique was used to measure the average liquid holdup in the cross section of the pipe. Three flow patterns in two risers were observed during the experiment: slug-slug (S-S), churn-churn (C-C), and churn-slug/churn (C-SC). Gas-liquid flow of S-S and C-SC is asymmetric, while that in C-C is symmetric. When the flow state in the two risers is S-S, the gas-liquid two-phase split could be uneven. When the gas and liquid velocities were sufficiently high for sustaining C-C, the gas and liquid were split evenly. The last state was the transition state between S-S and C-SC. A model based on pressure-minimization was established to predict two-phase flow splitting. The measured and predicted flow splits were observed to be in agreement.

Design and analysis of an optimized microfluidic channel for isolation of circulating tumor cells using deterministic lateral displacement technique

Circulating tumor cells (CTCs) are extremely scarce cells which cut off from a primary tumor and percolate into the circulation of blood flow and are, thus, critical for precise cancer detection and treatment. Deterministic lateral displacement (DLD) which exploits asymmetric splitting of laminar flow around the implanted microposts has displayed trustworthy capabilities in separating cells of varying sizes. In this research work, a microfluidic channel consisting of three symmetrically aligned inlets and outlets and embedded circular posts has been proposed which effectively separates the CTCs from lymphocytes utilizing the concept of DLD. Using a commercial software COMSOL Multiphysics 5.4, the design of the proposed microchannel has been simulated and analyzed considering an injected blood sample containing massive CTCs and slim WBCs of radii 13.5 µm and 6 µm, respectively. The proposed model of microchannel isolates the CTCs from WBCs at a comparatively higher sample mass flow rate of 4 × 10–6 kg/s and Reynolds number of 8.9 thereby operating efficiently at higher throughput, and offers excellent linearity in terms of velocity magnitude, pressure, shear rate and Reynolds number. The computational analysis of the proposed microchannel reveals that it can isolate CTCs from WBCs with better separation ratio, offers higher throughput, reduces possibilities of clogging and maintains better uniformity of pressure distribution and other flow parameters when compared with existing microchannel designs. The maximum separation ratio for CTCs and WBCs has been obtained as 84% and 96%, respectively.

Traffic Engineering in Segment Routing Networks Using MILP

In segment routing, a packet is forwarded along a path identified by a segment list. A segment list consists of segment identifiers (SIDs). A node-SID identifies a shortest-path segment, and an adjacency-SID identifies a link segment. A ${K}$ -segment path is a path with no more than ${K}$ segments. In this paper, we study the problem of finding a set of K- segment paths to carry all the flows in a given traffic matrix such that the maximum link utilization in the network is minimized. We first show that the solutions found by ${K}$ -LP, an existing linear programming (LP) approach, are not optimal because ${K}$ -LP does not support adjacency-SIDs. Focusing on 2-segment paths, a new LP formulation, denoted by e2-LP, is designed to support adjacency-SIDs in part. To fully support adjacency-SIDs, a mixed integer linear programming (MILP), denoted by ${K}$ -MILP, is designed. Since solving ${K}$ -MILP is time-consuming, a simplified version ( ${K}$ -sMILP) is also proposed. Finally, ${K}$ -sMILP is extended to prevent excessive flow splitting or using paths that are too long.

Characteristic Features of the Gas Chromatographic Separation of Tautomers of Ethyl Acetoacetate

Characteristic features of the gas chromatographic separation of the keto and enol tautomeric forms of ethyl acetoacetate on a capillary column with a BPX-1 standard nonpolar polydimethylsiloxane stationary phase are considered. It is confirmed that the chromatograms of a mixture of tautomers have a specific profile, i.e., a plateau between the peaks of the tautomers, which corresponds to the reversible keto $$ \rightleftarrows $$ enol transformation during separation. It is shown that the enol and keto forms of ethyl acetoacetate have different coefficients of the temperature dependence of the gas chromatographic retention indices (0.19 ± 0.03 and 0.02 ± 0.02, respectively). It is found there is no dependence of the relative peak areas of the tautomers on the nature of the solvent (polar ethyl alcohol and nonpolar hexane) at different temperatures; i.e., such ratios predominantly reflect the position of the keto $$ \rightleftarrows $$ enol equilibrium in the vapor phase of the injector of the chromatograph. It is concluded that this results in similar values of the thermodynamic parameters (standard enthalpy and entropy) of the tautomeric equilibrium determined upon the dosing of samples in different solvents. Possible distortions of the results due to the effects of discriminating between the compositions of the samples injected into capillary columns with gas flow splitting are discussed. An impurity in a sample of ethyl acetoacetate after long-term storage is identified as ethyl 2-hydroxy-3-oxobutanoate, the product of oxidation by dissolved atmospheric oxygen.

Effective mixing due to oscillatory laminar flow in tubular networks of plasmodial slime moulds

The plasmodium of the unicellular slime mould Physarum polycephalum forms an extended vascular network in which protoplasm is transported through the giant cell due to peristaltic pumping. The flow in the veins is always parabolic and it performs shuttle streaming, i.e., the flow reverses its direction periodically. However, particles suspended in the protoplasm are effectively and rapidly distributed within the cell. To elucidate how an effective mixing can be achieved in such a microfluidic system with Poiseuille flow, we performed micro-particle imaging velocimetry experiments and advected virtual tracers in the determined time-dependent flow fields. Two factors were found to be crucial for effective mixing: (i) flow splitting and flow reversals occurring at junctions of veins and (ii) small delays in the reversals of flows in the veins at a junction. These factors enhance the distribution of fluid volumes and hence promote mixing due to chaotic advection. From the residence time distributions of particles at a junction, it is estimated that about 10% of the volume is effectively redistributed at a junction during one period of the shuttle streaming. We presume that the principles of mixing unravelled in P. polycephalum represent a promising approach to achieve efficient mixing in man-made microfluidic devices.

Asymmetrical Flow Field Flow Fractionation Coupled to Nanoparticle Tracking Analysis for Rapid Online Characterization of Nanomaterials.

Increasing applications of nanomaterials in consumer goods, industrial products, medical practices, etc., calls for the development of tools for rapid separation, quantification, and sizing of nanoparticles to ensure their safe and sustainable employment. While many techniques are available for characterization of pure, homogeneous nanomaterial preparations, particle sizing and counting remains difficult for heterogeneous mixtures that resulted from imperfect synthesis conditions, aggregation from product instability, or degradation during storage. Herein, nanoparticle tracking analysis (NTA) was coupled to asymmetrical flow field flow fraction (AF4) using a splitter manifold to enable online particle separation and counting. The high pressure and flow rate in AF4 were reduced to the levels compatible with NTA by the proper flow splitting design, and a syringe pump was employed to withdraw fluid through the exit port of the NTA and maintain consistent flow rates entering NTA for proper particle sizing. Successful AF4-NTA coupling was demonstrated by analyzing a mixture of polystyrene particles with the average diameters of ∼50, 100, and 200 nm. Good correlation was observed between the amount of each type of particle injected to and measured by the hyphenated system. The particle concentrations acquired using online and offline coupling of AF4-NTA also agreed well with each other. The nonspherical nanoparticles like gold nanorods and hexagonal boron nitride nanosheets were also analyzed to demonstrate the versatile applicability of this system. Our work has proved that AF4-NTA can achieve accurate online particle counting on different populations of the nanomaterials in a mixture, which cannot be done by either AF4 or NTA alone. It will be a valuable tool for rapid characterization of heterogeneous nanomaterial solutions without purification to fulfill the regulation requirement on the nanomaterial-containing products.

An adaptive, fault tolerant, flow-level routing scheme for data center networks

Recent Data center network topologies put forward multiple paths between the end hosts to provide high bisection bandwidth. For the sake of utilizing the multiple paths efficiently many load-balancing techniques are proposed in literature. These load-balancing proposals mainly deal with distribution of traffic among multiple paths. Further, a good load-balancing technique scales down the latency of flows. While balancing the traffic among multiple paths, few proposals also take care of congestion. Flow-level solutions avoid flow splitting to prevent the packet re-ordering at the destination. Such adaptive solutions try to re-route (change the path) flows dynamically based on the feedback received from the network. In case of link failures, re-routing of the flow based on the queue size of the remote switch alone may be sub-optimal. The path to be chosen among multiple paths for re-routing, also poses a valid question. This paper proposes FlowFurl, an adaptive, distributed, end host driven and flow-level load-balancing technique. This adaptive routing technique supports dynamic flow-to-path assignment. This flow-to-path assignment is performed not only based on the congestion at the switch, but also the status of the links along the path. FlowFurl is the first technique to combine link failure and congestion information parameter for re-routing of flows. The proposed technique is deployment friendly, however it incurs small amount of overhead (small amount of memory at each switch to maintain the link state). We show that our proposed scheme FlowFurl performs better than considered schemes in terms of average flow latency, percentage of flows that achieve deadline and average flow throughput, by utilizing local information such as connectivity information with congestion information.

Properties of strange quark stars with isovector interactions

We study the properties of strange quark stars by employing a 3-flavor Nambu-Jona-Lasinio model with both scalar-isovector and vector-isovector interactions. Using the constraint on the vector-isoscalar interaction strength obtained from the elliptic flow splitting between particles and their antiparticles in relativistic heavy-ion collisions, we investigate the dependence of the properties of strange quark stars on the vector-isovector and the scalar-isovector interactions, and compare the results with the state-of-art astrophysical constraints on the compact star radius and mass as well as its tidal deformability from the GW170817 event. Results from our study reinforce the prospect of using both heavy-ion collisions and astrophysical observations to provide constraints on the isovector coupling strength in quark matter and thus the quark matter equation of state as well as the QCD phase structure at finite isospin chemical potentials.

Reconfigurable microfluidics: real-time shaping of virtual channels through hydrodynamic forces.

To break the current paradigm in microfluidics that directly links device design to functionality, we introduce microfluidic "virtual channels" that can be dynamically shaped in real-time. A virtual channel refers to a flow path within a microfluidic flow cell, guiding an injected reagent along a user-defined trajectory solely by hydrodynamic forces. Virtual channels dynamically reproduce key microfluidic functionality: directed transport of minute volumes of liquid, splitting, merging and mixing of flows. Virtual channels can be formed directly on standard biological substrates, which we demonstrate by sequential immunodetection at arrays of individual reaction sites on a glass slide and by alternating between local and global processing of surface-adherent cell-block sections. This approach is simple, versatile and generic enough to form the basis of a new class of microfluidic techniques.

Pushing the limits of resolving power and analysis time in on-line comprehensive hydrophilic interaction x reversed phase liquid chromatography for the analysis of complex peptide samples

In the present work, we have investigated the combination of hydrophilic interaction liquid chromatography (HILIC) and reversed phase liquid chromatography (RPLC) for the separation of peptides in on-line HILIC x RPLC. This combination usually leads to significant solvent strength mismatch, since a weak solvent in HILIC becomes a strong solvent in RPLC. This may result in band broadening, peak distortion, and breakthrough phenomena. Our focus was directed towards the reduction of band broadening and peak distortion. The conditions of the emergence of breakthrough could be investigated with high resolution mass spectrometry (HRMS) detection. The importance of both the injection volume and the difference in composition between injection and elution solvents was highlighted. Reported strategies to avoid bad peak shapes mostly rely either on flow splitting to limit the injection volume, or on on-line dilution. Here, we propose an alternative approach which consists in injecting large volumes in the second dimension. In this case, no flow-splitting nor dilution prior to the second dimension is required. Our results show that above a certain critical injected volume, depending on both the compound and the elution conditions, narrow and symmetrical peaks can be obtained, despite the persistence of breakthrough. As a result, the injected volume in the second dimension must be larger than the largest critical volume. This counter-intuitive approach was applied for the on-line HILIC x RPLC-UV-HRMS analysis of a complex tryptic digest sample. A peak capacity close to 1500 could be achieved in 30 min, which is two-fold higher than in RPLC x RPLC within the same analysis time.

Quantifying the Contribution of Crystallographic Texture and Grain Morphology on the Elastic and Plastic Anisotropy of bcc Steel

The influence of grain shape and crystallographic orientation on the global and local elastic and plastic behaviour of strongly textured materials is investigated with the help of full-field simulations based on texture data from electron backscatter diffraction (EBSD) measurements. To this end, eight different microstructures are generated from experimental data of a high-strength low-alloy (HSLA) steel processed by linear flow splitting. It is shown that the most significant factor on the global elastic stress–strain response (i.e., Young’s modulus) is the crystallographic texture. Therefore, simple texture-based models and an analytic expression based on the geometric mean to determine the orientation dependent Young’s modulus are able to give accurate predictions. In contrast, with regards to the plastic anisotropy (i.e., yield stress), simple analytic approaches based on the calculation of the Taylor factor, yield different results than full-field microstructure simulations. Moreover, in the case of full-field models, the selected microstructure representation influences the outcome of the simulations. In addition, the full-field simulations, allow to investigate the micro-mechanical fields, which are not readily available from the analytic expressions. As the stress–strain partitioning visible from these fields is the underlying reason for the observed macroscopic behaviour, studying them makes it possible to evaluate the microstructure representations with respect to their capabilities of reproducing experimental results.

Isospin splitting of pion elliptic flow in relativistic heavy-ion collisions

Based on the framework of an extended multiphase transport model with mean-field potentials in both the partonic phase and the hadronic phase, we explain the elliptic flow difference between π+ and π− in the beam-energy scan program at the relativistic heavy-ion collider by incorporating the vector-isovector potential for quarks and antiquarks with different flavors or isospins. It is found that the isospin splitting of pion elliptic flow favors a strong vector-isovector interaction, and thus serves as a probe of the quark matter equation of state as well as the QCD phase structure at finite baryon and isospin chemical potentials.

Maximizing two-dimensional liquid chromatography peak capacity for the separation of complex industrial samples

We report on a study on the use of 2D-LC in industry wherein we maximized the peak capacity by serially coupling up to six 15 cm long columns in the 1st dimension. For the considered aromatic amine oligomer sample, the combination of reverse phase pentafluorophenyl column providing selectivity based on π–π interaction in the 1st and a more retaining reverse phase polymeric C18 column in the 2nd dimension proved to give the highest orthogonality, calculated to be 0.82. Whereas a 1D run on a single column revealed around 120 compounds, the optimized 2D-LC system revealed around 940 compounds. To achieve this, flow splitting to improve the peak capacity in the 1st dimension and shifting gradients in the 2nd dimension were used. The overall peak capacity of the system was calculated to be 11,000 with correction for orthogonality and undersampling. The total analysis time with the 6-column system was around 20 h.

Flow-splitting-based computation of outlet boundary conditions for improved cerebrovascular simulation in multiple intracranial aneurysms.

Image-based hemodynamic simulations have great potential for precise blood flow predictions in intracranial aneurysms. Due to model assumptions and simplifications with respect to boundary conditions, clinical acceptance remains limited. Within this study, we analyzed the influence of outflow-splitting approaches on multiple aneurysm studies and present a new outflow-splitting approach that takes the precise morphological vessel cross sections into account. We provide a detailed comparison of five outflow strategies considering eight intracranial aneurysms: zero-pressure configuration (1), a flow splitting inspired by Murray's law with a square (2) and a cubic (3) vessel diameter, a flow splitting incorporating vessel bifurcations based on circular vessel cross sections (4) and our novel flow splitting including vessel bifurcations and anatomical vessel cross sections (5). Other boundary conditions remain constant. For each simulation and each aneurysm, we conducted an evaluation based on common hemodynamic parameters, e.g., normalized wall shear stress and inflow concentration index. The comparison of five outflow strategies for image-based simulations shows a large variability regarding the parameters of interest. Qualitatively, our strategy based on anatomical cross sections yields a more uniform flow rate distribution with increased aneurysm inflow rates. The commonly used zero-pressure approach shows the largest variations, especially for more distal aneurysms. A rank ordering of multiple aneurysms in one patient might still be possible, since the ordering appeared to be independent of the outflow strategy. The results reveal that outlet boundary conditions have a crucial impact on image-based blood flow simulations, especially for multiple aneurysm studies. We could confirm the advantages of the more complex outflow-splitting model (4) including an incremental improvement (5) compared to strategies (1), (2) and (3) for this application scenario. Furthermore, we discourage from using zero-pressure configurations that lack a physiological basis.

A Terminal-Oriented Distributed Traffic Flow Splitting Strategy for Multi-Service of V2X Networks

With the development and the characteristics of terminal services of the 5G (5th-Generation network) Internet of Vehicles (IoVs), this paper proposes a distributed splitting strategy for multi-type services of 5G V2X (Vehicle to X) networks. Based on a service-oriented adaptive splitting strategy in heterogeneous networks, combined with various service types such as communications between the networks, terminal, and base stations, and the value-added services of 5G IoVs, the proposed strategy jointly considers delay and cost as optimization goals. By analyzing the characteristics of the different services, the proposed traffic flow splitting strategy is modeled as an optimization problem to efficiently split services in 5G V2X networks. The simulation results show that by setting the traffic distribution policy for each service, the distributed traffic flow splitting strategy can significantly improve network transmission efficiency and reduce the service costs in a vehicle V2X network.

Elliptic flow of hadrons in Au + Au collisions at and 39 GeV from a multi-phase transport model based on a dynamical quark coalescence mechanism

We present a study of the transverse momentum (pT) spectra and the differential elliptic flow (v2) in a multi-phase transport model based on a dynamical quark coalescence model for Au + Au collisions at and 39 GeV. We have compared our results with the experimental data. The v2 of is found to be sensitive to the size parameter for mesons in the model. Our study indicates that the elliptic flow splitting between p and at lower energies may be partly due to quark coalescence in phase space.

Stratified Flows over and around Long Dynamically Tall Mountain Ridges

AbstractUniformly stratified flows approaching long and dynamically tall ridges develop two distinct flow components over disparate time scales. The fluid upstream and below a “blocking level” is stagnant in the limit of an infinite ridge and flows around the sides when the ridge extent is finite. The streamwise half-width of the obstacle at the blocking level arises as a natural inner length scale for the flow, while the excursion time over this half-width is an associated short time scale for the streamwise flow evolution. Over a longer time scale, low-level horizontal flow splitting leads to the establishment of an upstream layerwise potential flow beneath the blocking level. We demonstrate through numerical experiments that for sufficiently long ridges, crest control and streamwise asymmetry are seen on both the short and long time scales. On the short time scale, upstream blocking is established quickly and the flow is well described as a purely infinite-ridge overflow. Over the long time scale associated with flow splitting, low-level flow escapes around the sides, but the overflow continues to be hydraulically controlled and streamwise asymmetric in the neighborhood of the crest. We quantify this late-time overflow by estimating its volumetric transport and then briefly demonstrate how this approach can be extended to predict the overflow across nonuniform ridge shapes.

Suitable interface for coupling liquid chromatography to inductively coupled plasma-mass spectrometry for the analysis of organic matrices. 2 Comparison of Sample Introduction Systems

Liquid chromatography (LC) coupled with a specific detection such as inductively coupled plasma-mass spectrometry (ICP-MS/MS) is a technique of choice for elementary speciation analysis for complex matrices. The analysis of organic matrices requires the introduction of volatile solvents into the plasma which is an analytical challenge for this coupling technique. Detection sensitivity can be significantly affected by instrumental limitations. Among those, we were interested in the solute dispersion into the interface located between LC and ICP-MS/MS. This interface consists in both a Sample Introduction System (SIS) and a possible flow splitter. This study, divided into two parts, investigated the analytical performance (in terms of sensitivity and efficiency) generated by the coupling of LC and ICP-MS in the specific case of organic matrices. In Part I [1], we previously discussed the impact of extra column dispersion on the performance of LC-ICP-MS, first from a theoretical point of view and next, by assessing extra-column dispersion in 55 published studies on LC-ICP-MS. It was shown that SIS was rarely optimized with respect to its contribution to extra-column band broadening. The critical impact of flow splitting on extra-column dispersion was also pointed out.The present Part II is dedicated to the experimental comparison of commercially available SIS by assessing extra-column band broadening and hence the contribution of SIS to the loss in both efficiency and sensitivity. It is shown that the peak variance, due to SIS, can vary from 10 to 8000 μL² depending on the combination of both nebulizer and spray chamber. Whereas the highest values (i.e. > 2000 μL²) are much too high in high performance liquid chromatography (HPLC), even the lowest values (i.e. < 100 μL²) can be inappropriate in ultra-high pressure liquid chromatography (UHPLC) as highlighted in this study. In light of these results, it appears that nebulizer and spray chamber have to be chosen together with respect to the chromatographic technique (HPLC or UHPLC) and that both peak dispersion and peak intensity depend on key parameters including SIS device geometry, flow rate entering the interface or spray chamber temperature.

Charge asymmetry dependence of the elliptic flow splitting in relativistic heavy-ion collisions

The elliptic flow splitting $\Delta v_2$ between $\bar{u}$ and $u$ quarks as well as between $\pi^-$ and $\pi^+$ in midcentral Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV has been studied, based on the framework of an extended multiphase transport model with the partonic evolution described by the chiral kinetic equations of motion. Within the available statistics, the slope of $\Delta v_2$ between $\bar{u}$ and $u$ quarks with respect to the electric charge asymmetry $A_{ch}$ from the linear fit is found to be negative, due to the correlation between the velocity and the coordinate in the initial parton phase-space distribution. Simulations with the magnetic field in QGP overestimate the splitting of the spin polarization between $\Lambda$ and $\bar{\Lambda}$ observed experimentally, with the latter more consistent with results under the magnetic field in vacuum. Considering the uncertainties from the magnetic field, the quark-antiquark vector interaction, and the hadronization, as well as the hadronic evolution, our study shows that the experimentally observed positive slope of $\Delta v_2$ with respect to $A_{ch}$ is not likely due to the chiral magnetic wave.

Grain growth mechanisms in ultrafine-grained steel: an electron backscatter diffraction and in situ TEM study

In this work, the thermal stability of the strongly elongated and textured ultrafine-grained microstructure of a high-strength low-alloy steel processed by linear flow splitting is investigated. The annealing behavior is studied for α- and γ-fiber orientations, which are dominant in the rolling type texture of the material and are known for their differences in stored energy in conventionally cold rolled steels. Electron backscatter diffraction is used to assess contributions from curvature-driven boundary migration while the contribution of strain-induced migration is investigated by comparing the annealing behavior of prerecovered to non-prerecovered samples. The exact nature of the coarsening process is studied using in situ TEM heat treatments and complementary ACOM analysis. The results show that the observed preferred growth of α-fiber grains can be fully described by curvature-driven grain boundary migration and that there is no indication for the relevance of gradients in dislocation density.