Flow Regime Research Articles

Resistance not resilience traits structure macroinvertebrate communities in newly drying stream sections

AbstractTransitioning from perennial to non-perennial flow regimes causes ecological shifts in aquatic communities. Aquatic macroinvertebrates deploy resistance and resilience strategies to cope with flow intermittency, crucial in rivers with long-term seasonal dry episodes. Less is known, about how these strategies support community persistence in streams that only recently have experienced drying, and where local assemblages lack such adaptations. Our study conducted two four-season campaigns, separated by a one-year break, to assess macroinvertebrate responses in newly drying intermittent streams by comparing intermittent and perennial stream sections. We characterize communities from structural and functional perspectives, and then evaluate the response at the trait state level. We observed a decline in taxa richness and abundance, but not structural diversity, in response to flow intermittency. Resistance traits are more important than resilient traits in structuring macroinvertebrate communities in newly intermittent stream sections. Taxa in intermittent sections exhibit a smaller trait space, indicating lower functional redundancy. The macroinvertebrate response to intermittency lacks a predictable pattern, suggesting time-dependent and trait-state-specific colonization by adapted taxa and community assembly with resistance and resilience strategies. As river drought increases due to climate change, recognizing the temporal dimension becomes crucial for understanding ecological responses to intermittency.

Modal Discontinuous Galerkin Simulations for Grad’s 13 Moment Equations: Application to Riemann Problem in Continuum-Rarefied Flow Regime

For real-world engineering applications, there is a great deal of interest in developing effective models and simulations of continuum-rarefied gas flows. In this study, the numerical simulations of Grad’s 13 (G13) moment equations with application to the Riemann problem in a wide range of continuum-rarefied flow regimes are presented. This work emphasizes numerical robustness and wave phenomena in the G13 system to provide a building block for regularized 13 moment systems, and high-order Grad’s models. For this purpose, a high-order modal discontinuous Galerkin solver is developed for solving one-dimensional G13 moment equations. For spatial discretization, hierarchical modal basis functions premised on orthogonal-scaled Legendre polynomials are used. The proposed approach reduces the G13 systems into a framework of ordinary differential equations in time, which are addressed by an explicit third-order SSP Runge-Kutta algorithm. Three Riemann test cases, including the shock tube, two shock waves and two rarefaction waves, are examined in continuum-rarefied flow regimes. In the G13 system, the arising characteristic waves and dissipation phenomena are investigated in depth. The numerical results demonstrate that every Riemann problem does not have a solution for the G13 system because of loss of hyperbolicity of the system.

Flow dynamics and heat transfer analysis of a sweeping air jet – An experimental approach

Technological and environmental constraints are driving the development of enhanced heat transfer alternatives. In this context, the scope of this study encompasses sweeping jets generated by fluidic oscillators, which offer considerable potential for enhancing heat transfer. Initially, an experimental setup was developed to measure the flow velocity using a Laser Doppler Anemometer (LDA) and the heat transfer onto a target surface using a flux sensor. Moreover, videos capturing the free jet under various flow regimes were recorded using a Nikon® D850 camera. Concerning the flow dynamics of the sweeping jet, an upward trend in the estimated deflection angle of the jet and its oscillation frequency was noted at higher air flow rates. Heat transfer measurements on a surface indicated that an increase in air flow rate leads to improved heat transfer effectiveness of the jet. Finally, a comparison between the sweeping jet and the industry standard jet for surface cooling was carried out. This comparison revealed that the sweeping jet is highly sensitive to the flow regime at a distance from the plate of H/D= 6. In laminar flow, the sweeping jet outperforms the impinging jet in heat transfer performance. However, as the jet transitions to turbulent flow, the impinging jet exhibits superior thermal characteristics for enhancing heat transfer.

Influence of the shape of the anode assembly inner channel on plasma flow velocity

   This article considers how the shape of the inner channel in the anode assembly affects plasma flow velocity in a plasma torch. Three different shapes of the anode assembly were analyzed, all with a conical confusor part of 50 mm in length: with a diameter transition from 12 to 6 mm, from 12 to 8 mm, and from 12 to 10 mm. A computer experiment was performed using the finite element method and then validated by the subsequent full-scale experiment on a laboratory plasma unit. The obtained results were verified. The verification outcomes showed a satisfactory convergence and were consistent with the published data. A review of the existing plasma unit designs for powder production, application of functional coatings, and surface modification was carried out. The software packages implementing the finite element method to solve these problems were examined. The study yielded practical recommendations for consumers and developers of plasma equipment and identified the shapes of the anode assembly enabling both supersonic and subsonic plasma flow regimes.

Statistical Assessment of Water-quality Parameters for Different Flow Regimes

Groundwater and drainage-water sustainability is crucial to water management. Controlling the interaction between the groundwater and drain-water salinity at the watershed level has only been the topic of a limited number of studies. This study statistically compares salt concentration rate across time and four different flow regimes. We sampled water from 2014 to 2018. The study used R software to analyze water-quality parameters utilizing PCA and indices. Multiple water-quality indices were used to test irrigation water. A linear model with TDS as the response was fitted to the data. Another two-factor repeated-measurement covariate model was built. Water-quality indices suggest that measured water from varied flow regimes in the study area is suitable for irrigation. Based on the statistical models, Tukey's adjustment pairwise demonstrates considerable salinity variations between drain water and surface water. However, the main effect of the flow regime on TDS is significant. This indicates that the TDS value varies depending on the flow regime, not on time plus the interactions between these regimes. Keywords: Total dissolved solids (TDSs), Groundwater, ANCOVA, Flow condition, Tile drain, PCA

Development of Pipeline Transient Mixed Flow Model with Smoothed Particle Hydrodynamics Based on Preissmann Slot Method

The accurate modeling and understanding of complex transient mixed pipe flows is crucial for the optimal design and safe and efficient operation in pipeline systems such as urban drainage systems. Currently, the predominant approach for modeling free-surface-pressurized flows relies on grid-based numerical schemes, with comparatively limited capability for exploring its complex phenomena. This study proposed a novel one-dimensional numerical model that integrates the smoothed particle hydrodynamics (SPH) method with the Preissmann slot method (PSM) to explore transient mixed flows in pipeline systems, with better potential capability for exploring more mixed flow phenomena. Empirical parameters of the proposed SPH-PSM model were optimized for improving the numerical accuracy and stability, and the applicable range for these empirical parameters was recommended. The performances of the proposed model were evaluated by different flow regimes, including one free surface case, one fully pressurized case, and two transient mixed-flow cases. The simulation results of different flow regimes demonstrated a high level of agreement with the reference data, indicating the good capability of the SPH-PSM model in simulating complex flow regimes in pipeline systems. Therefore, the proposed SPH-PSM model can be an alternative way for modeling, exploring, and understanding the complex transient mixed flows in pipeline systems.

Rarefied gas flow in functionalized microchannels

The interaction of rarefied gases with functionalized surfaces is of great importance in technical applications such as gas separation membranes and catalysis. To investigate the influence of functionalization and rarefaction on gas flow rate in a defined geometry, pressure-driven gas flow experiments with helium and carbon dioxide through plain and alkyl-functionalized microchannels are performed. The experiments cover Knudsen numbers from 0.01 to 200 and therefore the slip flow regime up to free molecular flow. To minimize the experimental uncertainty which is prevalent in micro flow experiments, a methodology is developed to make optimal use of the measurement data. The results are compared to an analysis-based hydraulic closure model (ACM) predicting rarefied gas flow in straight channels and to numerical solutions of the linearized S-model and BGK kinetic equations. The experimental data shows that if there is a difference between plain and functionalized channels, it is likely obscured by experimental uncertainty. This stands in contrast to previous measurements in smaller geometries and demonstrates that the surface-to-volume ratio of 0.4 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document} seems to be too small for the functionalization to have a strong influence and highlights the importance of geometric scale for surface effects. These results also shed light on the molecular reflection characteristics described by the TMAC.

Prediction of Conveying Resistance for a Novel Hydraulic-mechanical Hybrid Vertical Lifting System

Objective: Recently a novel hydraulic-mechanical hybrid vertical lifting system was proposed for deep-sea mining. Accurate prediction of conveying resistance is important for the engineering design of the system. Plug flow of coarse particles is the main flow regime in the system. So far rare attention has been paid to the pressure drop prediction of plug flow of coarse particles. This paper aims to investigate eight theoretical pressure drop models on the applicability to predict the pressure drop of plug flow. Methods: Eight theoretical pressure drop models were studied. In addition, a hydraulic-mechanical hybrid vertical lifting test setup was developed. The novelty of this experimental work is that plug flow of coarse particles is formed and the lifting force of the plug can be measured with the test setup. Tests were conducted with varying particle sizes, lifting speeds and plug weights. The particle size is varied among 13, 18, and 25mm. The lifting speed is varied from 0.02m/s to 0.1m/s. The plug weight varies from 5 to 10kg. The range of Reynolds number for the tested particles is between 208 and 2,000. Results: Prediction errors of eight pressure drop models are derived and compared with the experimental data collected during this study. It was found that similar prediction trends are observed for all pressure drop models under most test conditions. Except the Rose model, all models produce average prediction errors less than 15%. The average prediction error for the Rose model is 20.59%. The average prediction error for the Ergun model is 12.43%. Conclusion: From this study it can be seen that the Ergun model produces the smallest prediction error among the eight selected pressure drop models for the given experimental conditions. Therefore, the Ergun model is considered to be most applicable for the calculation of the conveying resistance for the proposed vertical lifting system.

Numerical modelling of flow field at shaft spillways with the marguerite-shaped inlets

By decreasing the entrained air flow discharge and improving the hydraulic characteristics of vertical shaft spillways, Marguerite-shaped inlets (MSIs) can mitigate the effects of swirling flow surrounding their inlet. The hydraulic and hydrodynamic characteristics of flow around MSIs under orifice flow regime were numerically investigated, applying different geometrical parameters. This inlet configuration can decrease the strength of swirling flow and increase the flow discharge through the shaft. The finite-volume method and the re-normalisation group k–ε turbulence model were employed to solve the governing equations of motion in a cylindrical coordinate system and a two-phase air–water flow on the water free-surface. Increasing the height and length of the blades of the MSIs was found to increase the area of the barriers against swirling flow, weaken the swirling flow strength, engender a more uniform flow and lower the water free-surface level. Extremely long or high blades, however, resulted in an intense collision of the flow with the spillway and increased the water free-surface level and the swirling flow strength at the MSI.

Dual effects of drying and urban pollution on leaf litter decomposition and shredder consumption in permanent and intermittent streams

AbstractIn the present study we investigated the combined effect of flow intermittence and wastewater treatment plant (WWTP) effluent on leaf litter decomposition in two Mediterranean streams with permanent and intermittent flow regimes. The litter decomposition experiment was performed using black poplar litter bags where we measured litter mass loss, fungal biomass, aquatic hyphomycete sporulation and species richness and C:N ratio. Afterwards, the remaining litter material from the different treatments was offered to the shredder Potamophylax latipennis in a microcosm laboratory experiment, and its growth and consumption rates were studied. We hypothesised that drying would decrease leaf litter decomposition in the permanent stream more than in the intermittent stream and that WWTP effluent would compensate for drying effects when both stressors interacted. The results indicated that drying has the greatest impact on the permanent stream, decreasing decomposition, aquatic hyphomycete species richness, and leaf litter quality. In the intermittent stream, WWTP effluent decreases aquatic hyphomycete species richness, but drying increases it, showing an opposing effect and a synergistic interaction. In the permanent stream drying provoked an increase in the shredder consumption rate. Thus, the expected more frequent intermittence in rivers under climate change may threaten the processing of organic matter.

A comprehensive analysis of the ‘coming and going’ phenomenon of the projectile motion of a sphere under air resistance

We have analyzed the ‘coming and going’ phenomenon of the projectile motion of a sphere using experimental data correlations that span the entire range of Reynolds numbers. We have modeled the drag force using an analytical expression for the drag coefficient and performed a numerical analysis to compute the critical angle as a function of the sphere’s initial speed, radius, and mass. Our results indicate that the critical angle behaves analogously to the drag coefficient as a function of the Reynolds number. This study is significant as it deals with a drag force not limited to any specific flow regime and may help undergraduate students and science instructors delve deeper into the subject.

Application and parameterization of a one‐dimensional multifluid population balance model to bubble columns

AbstractA one‐dimensional (1D) multifluid population balance model approach is presented as a compromise between computational effort and accuracy. The approach is used to test process scenarios, perform sensitivity analysis, and provide a reliable reactor scale‐up and optimization tool. The article focuses on a mini‐plant batch bubble column, where the scale‐up behavior in terms of bubble column height, gas flux, and composition of the liquid phase is investigated. Although simplifications were made, the model requires calibration to experimental data using different calibration methods. An optimal calibration procedure is found that minimizes experimental effort while maximizing scalability. The model was tested on various liquid‐phase compositions, and it was found to reproduce experimental data accurately. However, the model cannot reproduce flow regime changes and does not perform well across substance systems. The study shows that the applied 1D multifluid population balance approach is a valuable and reliable tool in multiphase reactor scale‐up and optimization.

Modelling flow regulation effects on vegetation recruitment and survival on alternate bars in channelized rivers

AbstractMany river reaches have transitioned to heavily vegetated systems following the regulation of their flow regime. Vegetation recruitment and survival are key to these transformations. We propose a novel predictive approach to detect how changes in the flow regime may affect conditions for successful vegetation recruitment and survival in channelized rivers with alternate bars. Our approach combines elements of existing vegetation recruitment models (Recruitment Box and Window of Opportunity) with simplified morphodynamic predictions of alternate bar migration. The approach is illustrated by applying it to a reach of the regulated Isère river, SE France, which has transitioned from migrating, unvegetated to steady, vegetated alternate bars over two decades following flow regulation associated with hydropower development. Our modelling approach identifies a strong impact of modified summer flows on vegetation recruitment since 1950 when major flow regulation began. An increase of up to 1 cm year−1 (after 1990) has occurred in the vertical extent of vegetation recruitment bands on the bars. This has been accompanied by an almost 20 m total increase (since 1950) in the horizontal extent of the recruitment bands, and a 1.5 times reduction in the frequency of high flows capable of promoting bar migration. Our modelling also suggests viable flow restoration options to limit widespread vegetation colonisation. Comparing outcomes from our modelling approach with those from the Bertagni et al. (2018) model suggests that the Isère may have been highly prone to vegetation colonisation even before flow regulation and close to some threshold for a shift from an unvegetated to a vegetated state.

Hydrodynamics and wet pressure drop model based on flow regimes of the novel Flow-Divided Baffle-Bridge Tray

This study introduces the Flow-Divided Baffle-Bridge Tray (FDBBT), an innovative tray design featuring hole-bridge structures at the caps’ base for pre-distribution of gas and liquid, and stepped baffles configuration at the caps’ top to minimize entrainment. The pressure drop, weep and entrainment of FDBBT were evaluated in a Φ796 mm experimental setup. Compared to the sieve tray and Glitsch V-1 valve tray, FDBBT demonstrated lower pressure drops and significantly reduced entrainment, suggesting a higher operational ceiling. Furthermore, a specialized single-cap experimental apparatus was designed to assess the lifted liquid rate and uncover gas-liquid flow regimes within the cap, namely churn flow, free-surface flow, and periodic-free-surface flow. Employing data from the single-cap experiments, complemented by CFD-assisted analysis, FDBBT's pressure drop model was established and then validated by the Φ796 mm experiments, with most deviations falling within a 5 % threshold.

Monochorionic Twinning in Bioengineered Human Embryo Models.

Monochorionic twinning of human embryos increases the risk of complications during pregnancy. The rarity of such twinning events, combined with ethical constraints in human embryo research, makes investigating the mechanisms behind twinning practically infeasible. As a result, there is a significant knowledge gap regarding the origins and early phenotypic presentation of monochorionic twin embryos. In this study, a microthermoformed-based microwell screening platform is used to identify conditions that efficiently induce monochorionic twins in human stem cell-based blastocyst models, termed "twin blastoids". These twin blastoids contain a cystic GATA3+ trophectoderm-like epithelium encasing two distinct inner cell masses (ICMs). Morphological and morphokinetic analyses reveal that twinning occurs during the cavitation phase via splitting of the OCT4+ pluripotent core. Notably, each ICM in twin blastoids contains its own NR2F2+ polar trophectoderm-like region, ready for implantation. This is functionally tested in a microfluidic chip-based implantation assay with epithelial endometrium cells. Under defined flow regimes, twin blastoids show increased adhesion capacity compared to singleton blastoids, suggestive of increased implantation potential. In conclusion, the development of technology enabling large-scale formation of twin blastoids, coupled with high-sensitivity readout capabilities, presents an unprecedented opportunity for systematically exploring monochorionic twin formation and its impact on embryonic development. This article is protected by copyright. All rights reserved.

Constitutive Relations for Granular Flow That Include the Three Flow Regimes of Chialvo et al.

Constitutive Relations for Granular Flow That Include the Three Flow Regimes of Chialvo et al.

Laboratory Observation of Fluid Flow in Depleted Shale Gas Reservoir: Coupling Effect of Sorbing and Non-sorbing Gas on Stress, Slippage, Flow Regime in Anisotropic and Fractured Shales

Laboratory Observation of Fluid Flow in Depleted Shale Gas Reservoir: Coupling Effect of Sorbing and Non-sorbing Gas on Stress, Slippage, Flow Regime in Anisotropic and Fractured Shales

Application of a hydrophobic coating to a pressurized pipe and its effect on energy losses and fluid flow profile

The use of additives, generally called DRAs (Drag Reducing Additives), has been proposed to re-duce the energy consumption in pressurized pipes. Although many research works have been conducted to analyze the effect of these additives, less attention have been devoted to the application of coatings to the pipe wall. This paper demonstrates that the application of a hydrophobic coating to the pipe can lead to a head loss reduction for a transition flow regime with moderate Reynolds number values (Re). For this purpose, an experiment was conducted to compare the performance of both coated and uncoated pipes by measuring the head losses and assessing the Drag Reduction Percentage (%DR) and the pipe friction factor (f). This was done for two Polyvinylchloride (PVC) pipes with different nominal diameters (PVC90 and PVC63). In addition, the flow velocity distribution was also measured in all these tests. The %DR decreased as the Re values increased, with the reduction being notably less pronounced for higher Re values. This could be explained by the fact that a partial slip condition is induced by the hydrophobic product. Its effect is significant for a transition regime where the effect of viscosity is important, but it becomes negligible for increasing levels of turbulence. No significant differences were observed in the flow distribution between coated and uncoated pipes, which seems to indicate that the velocity change could be limited to the near-wall viscous sublayer. The results of this work open an important research line aimed at reducing energy costs and the carbon footprint in pipe fluid distribution systems.

A Scalable Microfluidic Platform for Nanoparticle Formulation: For Exploratory- and Industrial-Level Scales.

Nanoparticle synthesis on microfluidic platforms provides excellent reproducibility and control over bulk synthesis. While there have been plenty of platforms for producing nanoparticles (NPs) with controlled physicochemical properties, such platforms often operate in a narrow range of predefined flow rates. The flow rate limitation restricts either up-scalability for industrial production or down-scalability for exploratory research use. Here, we present a universal flow rate platform that operates over a wide range of flow rates (0.1-75 mL/min) for small-scale exploratory research and industrial-level synthesis of NPs without compromising the mixing capabilities. The wide range of flow rate is obtained by using a coaxial flow with a triangular microstructure to create a vortex regardless of the flow regime (Reynolds number). The chip synthesizes several types of NPs for gene and protein delivery, including polyplex, lipid NPs, and solid polymer NPs via self-assembly and precipitation, and successfully expresses GFP plasmid DNA in human T cells.

Validation of two-group interfacial area transport equation in boiling flow

The Two-Fluid Model is the backbone of thermal-hydraulics and system-analysis codes for nuclear design. The Two-Fluid Model tracks the transfer of conserved quantities—mass, momentum, and energy—without the need for bubble interface tracking. However, two-phase flows are characterized by their different flow regimes which change as more vapor is present in the flow, from bubbly flow to cap/slug flow to annular flow. The two-group Two-Fluid Model can track the progression of boiling flows beyond the bubbly region without the need for flow-regime maps. A two-group wall-boiling model is implemented and coupled with the two-group Interfacial Area Transport Equation. The resulting model is compared against experimental data and predicts the growth in cap/slug bubbles through interaction models rather than through flow-regime maps. The coupled model can predict the growth in void fraction and interfacial area concentration beyond the capability of the one-group model, demonstrating the applicability of a coupled two-group approach to modeling boiling flow.