Flow Mode Research Articles

Organic synthesis in flow mode by selective liquid-phase hydrogenation over heterogeneous non-noble metal catalysts.

Flow hydrogenation performed over heterogeneous catalysts makes organic synthesis more economical, safe and environmentally friendly. Over the past two decades, a significant amount of research with a major focus on noble metal catalysts has been carried out in this area. However, catalysts based on non-noble metals (Ni, Cu, Co, etc.) are more promising for practical use due to their low cost and high availability. This review article discusses the use of supported and bulk non-noble metal catalysts for the liquid-phase hydrogenation of bi- and polyfunctional organic compounds in flow mode. The main attention is paid to the selective reduction of one functional group (NO2, CC, CN, CO, and CN) in the presence of other substituents. In addition, cascade synthetic protocols involving hydrogenation are presented.

Pore-scale imbibition patterns in layered porous media with fractures

The presence of fractures increases the difficulty of flow mechanisms analysis, and it remains unclear how fractures affect multiphase flow displacement in the layered rock matrix. Herein, a pore-scale imbibition model considering the layered matrix-fracture system is established using the phase-field method, where oil is displaced by a range of fluids with various properties. Two typical flow modes are carefully analyzed, depending on the locations of the fracture and the interfaces between different layers of the matrix: fracture is parallel to the interface (mode I), and it penetrates through the interface (mode II), which are dominated by the co-current imbibition and countercurrent imbibition mechanisms, respectively. Interestingly, the surface tension is found to be negatively correlated with the ultimate oil recovery rate for mode I and plays an opposite effect on that of mode II. For flow mode I, the conditions of lower injection rate, higher viscosity ratio, higher grain diameter ratio, and injection of the invading fluid from the larger pore throat size (positive direction flow) can improve oil recovery. For flow mode II, the fracture bifurcation angle has little effect on the positive direction flow, while it can significantly regulate the phase distribution in the negative direction flow. Based on scaling analysis of relating pore-filling events to displacement modes and the equilibrium relationship between capillary and viscous forces, two theoretical models are derived to predict the imbibition patterns, and the variation of the flow regime under various parameters in the typical layered matrix-fracture models is systematically concluded.

Spatiotemporal Variation of Groundwater Nitrate Concentration Controlled by Groundwater Flow in a Large Basin: Evidence From Multi‐Isotopes (15N, 11B, 18O, and 2H)

AbstractElevated and increasing concentration in groundwater affect groundwater supplies in China and elsewhere. However, how groundwater flow affects concentration in groundwater has yet to be fully understood. Herein, multi‐isotopes (15N, 11B, 18O, and 2H) and local indicators of spatial association (LISA) were used to elucidate the spatiotemporal variation, sources, and patterns of and its response to groundwater flow in Poyang Lake Basin where agriculture, industry and urban coexist. The location of hotspots identified by LISA tended to move from the middle to lower reaches of Ganfu Plain with groundwater flow, and hotspots area expanded in the upper reaches of Xin River Basin and northwest of the study area during the transition from dry season to wet season. Our results revealed that variations of regional concentration were controlled by groundwater recharge or flow mode (vertical or lateral), biogeochemical processes and sources (sewage and manure). In some areas with the single stratigraphic structure (unconfined aquifer), spatiotemporal variation of concentration was influenced by local pollution sources and vertical recharge of current precipitation (vertical flow). In some areas with binary structures (confined aquifer), groundwater was mainly recharged by lateral flow and concentration was mainly affected by mixing effect of upstream groundwater, reflecting human activities in the upper reaches rather than local human activities. In lakeside floodplain, groundwater was attenuated by the dissimilatory reduction to . This study provides a novel insight into groundwater flow controlling on spatiotemporal distribution of concentration in the regional scale.

Multiphase photochemistry in flow mode via an integrated continuous stirred tank reactor (CSTR) approach.

A new photochemical CSTR system capable of handling solids in scaled continuous processes is presented. High-power UV-LEDs are integrated in these CSTRs containing an insoluble base that aids in generating pyrazolines via cycloaddition between alkenes and in situ generated diazo species. Contrary to reported batch methods product degradation via ring contraction is suppressed whilst generating gram quantities of spirocyclic pyrazolines.

Flow modulation mechanism in a cylinder with corrugated surfaces

Flow modulation mechanism in a cylinder with corrugated surfaces is investigated by wind tunnel experiments at Reynolds number Re=25 600. Experimental results include surface pressure measurement for the cylinder wall and particle image velocimetry (PIV) for the wake flow. A pair of corrugated surfaces are symmetrically installed on the cylinder wall. Corrugated surfaces are distributed at three different locations on the cylinder wall, i.e., the windward part (case 1), leeward part (case 2), and lateral part (case 3). Experimental results show that corrugated surfaces can modify surface pressure, aerodynamic forces, and vorticity evolution of the cylinder flow. Compared with the natural cylinder (baseline case), the mean drag and fluctuating lift forces of case 1 are reduced by 58% and 82%, which are optimal among all test cases. Flow modulation effects of case 2 on global cylinder wake flow are unobvious and that of case 3 are between cases 1 and 2. Corrugated surfaces can also modify modal properties of proper orthogonal decomposition (POD) of the cylinder wake. Moreover, characteristics of recirculation bubbles, velocity deficits, turbulence kinetic energy, and Reynolds stresses in the wake are all modulated. The main flow modulation mechanism is that shear-layer shapes and streamline distributions near the corrugated surfaces are changed based on zoom-in PIV results on the cylinder near-wall region.

Stabilize cloud cavitation with an obstacle near hydrofoil's trailing edge and conduct local entropy production analysis

Cloud cavitation always causes severe damage to the efficiency and stability of the hydraulic machinery, resulting in extra energy losses in the system. We have observed an effective and simple way to prevent cloud cavitation formation by placing an obstacle near the hydrofoil's trailing edge. Cavitating flows around four different types of hydrofoils were simulated using the stress-blended eddy simulation turbulence model: the National Advisory Committee for Aeronautics (NACA) 66 hydrofoil and the NACA 66 hydrofoil with a 1 ×1 mm2 obstacle at 0.3c, 0.5c, or 0.7c. Sheet cavitation is the predominant mode of cavity flow when the obstruction is positioned at 0.7c. To find out why the cloud cavitation growth can be stopped when the obstruction is positioned at 0.7c, the velocity field, vorticity in the Z direction, and vortex structure of the Q-criterion were computed. To study the energy loss of the cavity flow and comprehend how obstacles affect it, the local entropy production rate was computed. It was discovered that the vorticity downstream of the obstacle, positioned at 0.7c, is restructured, which helps manage the flow separation upstream of the obstacle. Consequently, the hydrofoil's suction surface vorticity nearly rotates in the same direction as the obstacle at 0.7c, and the direction of Vx upstream of the obstacle is in the positive direction of the X axis, indicating that the reentrant flow has been controlled upstream of the 0.7c obstacle. Furthermore, cavitation shedding and the entropy production rate are strongly correlated, and regulating cloud cavitation growth is advantageous for energy conservation.

Active Frequency-Dependent GER Fluid Damper With a Composite Mode of Cut and Flow

Active Frequency-Dependent GER Fluid Damper With a Composite Mode of Cut and Flow

Аналіз одношарового руху зернового матеріалу у вертикальному пневмосепараційному каналі

The separation of grain and light impurities in a vertical pneumatic separation channel with an increase in its capacity occurs under rather difficult conditions, since the thickness of the grain flow increases, which leads to a redistribution of particles of grain material and reduces the probability of passing light impurities through the grain layers and their release into the sedimentation chamber. To increase the productivity of vertical pneumatic separation channels, it is necessary to create conditions for single-layer placement of grain material in the separation zone at a distance that excludes the interaction of other layers of grain input. This will allow the majority of grain particles to be in the same conditions and increase the percentage of probability of separation into the sedimentation chamber to the maximum value. Therefore, a theoretical flow analysis aimed at studying the interaction of grain mixture particles with the air flow, taking into account the single-layer arrangement of several grain layers and the contamination of the air flow with light impurities in the separation zone, is a rather important task. Theoretical dependences have been obtained that allow substantiating the main parameters of the pneumatic separation channel and determine the residence time of a grain particle in the separation zone, taking into account the clogging of the air flow. For a grain material of mass characterized by the values of the windage coefficient kз = 0.075...0.12 for full grain, kз = 0.11...0.14 for substandard grain, and kз = 0.125...0.55 for light impurities, it is possible to clearly separate the grain mixture into fractions by setting the appropriate parameters and operating modes of the pneumatic separation channel under the condition of a single-layer multilevel input. Due to the selection of rational parameters of the feeding devices for delivering the material into the separation zone and establishment of appropriate aerodynamic modes of air flow, it is possible to separate up to 96% of light impurities from the grain material, while ensuring minimal losses of full grain to waste.

Dependence of changes in the nominal heat flow of tubular heating devices on their design features

The article is devoted to determining the nominal heat flow of a steel tubular heating device depending on the location of the pipes (vertical or horizontal), the number and diameter of pipes, as well as the value of the heat transfer coefficient. The main advantages and disadvantages of steel tubular heating devices are given. It has been determined that the mode of heat flow along the pipes in a tubular heating device changes from laminar to turbulent. As a result of the research, it was found that with a vertical arrangement of pipes in a heating device, when the coolant temperature in the pipes is 90-95°C, the height of the transition zone from laminar flow to turbulent flow varies in the range from 0.75 m to 1.25 m. If the tubular heating device is structurally made with horizontally located pipes, then the transition from the laminar flow regime to the turbulent regime is not observed. A dependence has been derived that allows one to determine the nominal heat flow of a steel tubular radiator depending on the height, number of sections, as well as the design features of the tubular heating device. A comparative analysis of changes in the nominal heat flow of a tubular heating device was carried out depending on the height, number of sections, design features, as well as the orientation of the pipes in the section. The nominal heat flux of a tubular radiator varies depending on the orientation of the pipes. It is shown that with a vertical arrangement of a tubular radiator, the value of the nominal heat flux exceeds the same value with a horizontal arrangement.

Feel the force: From local surface pressure measurement to flow reconstruction in fluid–structure interaction

Drawing inspiration from the lateral lines of fish, the inference of flow characteristics via surface-based data has drawn considerable attention. The current approaches often rely on analytical methods tailored exclusively for potential flows or utilize black-box machine learning algorithms to estimate a specific set of flow parameters. In contrast to a black-box machine learning approach, we demonstrate that it is possible to identify certain modes of fluid flow and then reconstruct the entire flow field from these modes. We use dynamic mode decomposition to parametrize complex, dynamic features across the entire flow field. We then leverage deep neural networks to infer the dynamic modes of the pressure and velocity fields within a large, unsteady flow domain, employing solely a time series of pressure measurements collected on the surface of an immersed obstacle. Our methodology is successfully demonstrated to diverse fluid–structure interaction scenarios, including cases with both free oscillations in the wake of a cylinder and forced oscillations of tandem cylinders, demonstrating its versatility and robustness.

Alleviation of Post-sepsis Ischaemia by Drag-Reducing Polymers.

Sepsis, leading to septic shock and multiple organ dysfunction syndrome, is characterised by inflammation, coagulopathy, and microvascular dysfunction, the primary cause of in-hospital mortality. Novel approaches are needed to prevent the consequences of sepsis. We showed that nanomolar concentrations of intravascular blood-soluble drag-reducing polymers (DRPs) significantly improve microvascular perfusion and tissue oxygenation and protect neurons in rat brains after traumatic brain injury and haemorrhagic shock. The aim of this work was to determine whether DRPs-enhanced perfusion could alleviate sepsis-associated microvascular dysregulation in a mouse model of lipopolysaccharide (LPS)-induced sepsis. LPS (Salmonella Thyphosa, 10mg/kg, i.v.) was administered intravenously to induce acute sepsis in C57BL/6 J mice. DRPs (final concentration 5ppm in the blood) or saline was injected i.v. (10 mice/group) 1h after LPS injection to evaluate the efficacy of haemorheological modulation of microvascular dysregulation. In-vivo two-photon laser scanning microscopy was used to monitor cerebral (parietal cortex) and peripheral (ear) microcirculation (i.v. fluorescein isothiocyanate dextran) and tissue oxygen supply (nicotinamide adenine dinucleotide autofluorescence) at a baseline and during 4h after septic shock induction. Differences between groups were determined using a two-way analysis of variance for multiple comparisons with post hoc testing. The statistical significance was set at p<0.05. LPS-induced sepsis led to microvascular dysfunction and tissue hypoxia in the brain and peripheral tissue (ear). DRPs alleviated microthrombosis formation, microvascular dysfunction, and tissue hypoxia in the brain and peripheral tissue compared to the saline control group (p<0.05). Therefore, haemorheological modulation of blood flow by DRPs effectively improves systemic and peripheral circulation, reducing microthrombosis formation, microvascular dysfunction, and tissue hypoxia that can alleviate sepsis, shock, and multiple organ dysfunction syndrome.

Electroosmotic flow modulation and dispersion of uncharged solutes in soft nanochannel.

We perform a systematic study on the modulation of electroosmotic flow (EOF), tuning the selectivity using electrolyte ions and hydrodynamic dispersion of the solute band across the soft nanochannel. The supporting walls of the channel are considered to be hydrophobic and bear non-zero surface charge. For such a channel, the inner side of the supporting rigid walls of the channel are coated with a soft polyelectrolyte layer (PEL). The inhomogeneous distribution of monomers and accompanying volume charge within the PEL is modelled via soft-step function. The dielectric permittivity of the PEL and electrolyte solution are in general different, which in turn leads to the ion partitioning effect. The impact of ion steric effects due to finite sized ions is further accounted through the modified ion activity coefficient. To model the EOF modulation considering the combined impact of the ion steric and ion partitioning effects as well as inhomogeneous distribution of monomers across the PEL, we adopt the modified Poisson-Boltzmann equation as the governing equation for electrostatic potential. The Debye-Bueche model is adopted to study the flow field across the PEL and the Stokes equation governs the EOF outside the PEL. In order to study the impact of the modulated EOF field on the dispersion of uncharged solution, we adopt three different models, i.e., a general 2D convective-diffusion model as well as cross-sectional averaged dispersion models due to Gill and late-time Taylor and Aris. Going beyond the widely employed Debye-Hückel approximation and uniform distribution of the monomer as well as accompanying volume charge, we find the results for the electric double layer (EDL) potential, EOF field and averaged throughput, by tuning the ion selectivity, etc., which is sufficient to analyze the transport of ionized liquid across the channel. The numerical results are supplemented with analytical results for the EDL potential as well as the EOF field under various limiting situations. Besides, we have further shown the impact of the modulated EOF field on the solute dispersion process. We have presented results that highlight the impact of parameters related to EOF field modulation, on solute dispersion governed by a convective-diffusive process, as well as obtaining the results for an effective dispersion coefficient. The dispersion models under the modulated EOF field adopted in the present study can thus be applied to study the dispersion process in engineered microdevices.

Numbering up and sizing up gliding arc reactors to enhance the plasma-based synthesis of NO x.

Non-thermal plasma-based NO x synthesis from ambient air is receiving an increasing amount of interest for its potential in small-scale, sustainable fertilizer production. Nevertheless, most reported research focuses on lab-scale systems and a single reactor with limited production. In this work, two gliding arc reactors (GARs) with 2 mm discharge gaps were connected in series or in parallel to explore strategies for scaling up the productivity. A single GAR with an enlarged discharge gap of 4 mm was also investigated for comparison. Operation parameters such as flow rate, discharge power & mode, and effective residence time were tested. The NO x concentration increased for all configurations with an increase in specific energy input (SEI), and effective residence time. The case of reactors connected in series outperformed all other configurations. The energy consumptions and NO x productions achieved were 2.29-2.42 MJ molN -1 and 124.6-158.3 mmolN h-1, respectively. The NO2 selectivity could be enhanced by prolonging the post-plasma oxidation time while consuming the excess O2 in the feed and utilizing the low temperatures at the reactor(s) outlet. By using this connection strategy, NO x production can be doubled with a 20.9% improvement in energy consumption compared to a single reactor.

A microbial perspective on speciation

Abstract Understanding what a microbial species is and the process of speciation in microbes has been and still is a puzzle with many challenges. But there is now emerging consensus that speciation in microbes does follow certain rules and limitations. Just like in macrobes, it can be driven by divergent natural selection and is maintained by barriers to gene flow, either genetic or ecological in nature. However, whether microbial speciation mirrors that of sexually reproducing eukaryotes is up for debate, as extensive horizontal gene flow can blur patterns and processes. Here, I provide intriguing examples of speciation in bacteria, viruses, and yeast, which are arguably similar to what we see in eukaryotes. I synthesize recent insights from microbial evolutionary genomics, which may mitigate the traditional view that microbes are ‘messy’ and do not fit eukaryotic species concepts and speciation models. Finally, I highlight the benefits of microbial experimental evolution to answer fundamental questions in speciation research (especially why, how, and when speciation occurs). Speciation research with microbes, as opposed to the organisms traditionally used in this field, may suffer less from observational bias and the experimental control we have over selection types, gene flow, and reproductive modes in microbial systems may allow us to determine the mechanisms and timing of ecological divergence, reproductive isolation, and speciation.

Learning Diverse Tone Styles for Image Retouching.

Image retouching, aiming to regenerate the visually pleasing renditions of given images, is a subjective task where the users are with different aesthetic sensations. Most existing methods adopt a deterministic model to learn the retouching style from a specific expert, making it less flexible to meet diverse subjective preferences. Besides, the intrinsic diversity of an expert due to the targeted processing of different images is also deficiently described. To circumvent such issues, we propose to learn diverse image retouching with normalizing flow-based architectures. Unlike current flow-based methods which directly generate the output image, we argue that learning in a one-dimensional style space could 1) disentangle the retouching styles from the image content, 2) lead to a stable style presentation form, and 3) avoid the spatial disharmony effects. For obtaining meaningful image tone style representations, a joint-training pipeline is delicately designed, which is composed of a style encoder, a conditional RetouchNet, and the image tone style normalizing flow (TSFlow) module. In particular, the style encoder predicts the target style representation of an input image, which serves as the conditional information in the RetouchNet for retouching, while the TSFlow maps the style representation vector into a Gaussian distribution in the forward pass. After training, the TSFlow can generate diverse image tone style vectors by sampling from the Gaussian distribution. Extensive experiments on MIT-Adobe FiveK and PPR10K datasets show that our proposed method performs favorably against state-of-the-art methods and is effective in generating diverse results to satisfy different human aesthetic preferences. Source codeterministic and pre-trained models are publicly available at https://github.com/SSRHeart/TSFlow.

Numerical simulation of wind turbines conducted using COMSOL software

The article presents the results of modeling air flow in a turbulent mode of flow around a wind device as profiles and fields of pressure and velocity. The simulation was performed with the help of the COMSOL software package. The axial velocity profile, pressure coefficient around the blade and instantaneous power coefficient of one blade using the transient SST model are in good agreement with the experimental data. The presented values of the device’s power factor Cp were obtained using different turbulence models. When mathematically modeling the flow around a vertical axis wind turbine, the transient SST turbulence model can be used, which provides satisfactory results.

A facile, catalyst- and additive-free, and scalable approach to the photochemical preparation of disulfides from organosulfenyl chlorides.

A novel, clean and efficient protocol for the preparation of disulfides has been developed through the photochemical radical homo- and cross-coupling reaction of sulfenyl chlorides under LED irradiation and without the use of any catalyst and additive. The representative photochemical homo-coupling of trichloromethyl sulfenyl chloride has been successfully conducted on kilogram-scale in a continuous flow mode. The solvent and the main byproduct can be recovered in high yields, which makes the approach be highly atom economical.

PI-based cascade control for Fresnel solar collectors in wastewater reclamation

This work presents a novel demonstration-scale integration of a 36-m2 Fresnel solar collector in urban wastewater reclamation. A prototype plant was designed and installed to study Escherichia coli and total coliforms disinfection in continuous flow mode. The plant modelling was empirically addressed, resulting in different linear first-order models, which were used to design a PI-based cascade control approach for the automatic operation of the photoreactor. Considering EU 2020/741 Regulation, water quality Class D and Class A were achieved when operating the upgraded design of the plant at 50°C (200 L/h) and 60°C (150 L/h), respectively.

The effect of pipeline parameters of machines for applying liquid complex fertilizers on the drip-air mixture quality

The article is devoted to the study of a drip-air mixture flow through pipelines, namely, the determination of total pressure losses based on known values of the flow rates of the constituent phases or the loss coefficients of the constituent phases. The authors conclude that the conditions for introducing the drip-air mixture into the pipes do not affect the size of the flow structure stabilization area. It has been found that for small values of the air and liquid flow rates, the diameter and length of the pipeline, as well as its position, have a very significant effect on the flow structure of the two-phase mixture and on the average diameter of the droplets. For each pipeline length and diameter, there is a pulsation flow mode only at certain values of the air and liquid flow rates (Gv/Gl), moreover, the larger the diameter and length of the pipeline, the later the pulsation flow mode occurs. At high values Gv/Gl, the position, length, and diameter of the pipeline do not have a noticeable effect on the flow shape, the flow has a finely dispersed structure, pressure pulsation is practically absent.

Creativity and consciousness in motion: The roundtrip of "mindful" and "mindless" processes in embodied creativity.

In this opinion paper, we make a journey across different accounts of creativity that emphasize either the mindful, conscious and cognitive expression of creativity, or its mindless, unconscious and sensorimotor expression. We try to go beyond dichotomy, putting creativity in motion and outlining its embodied and enactive features. Based on the assumption that no creative act is purely conscious or purely unconscious, our discussion on creativity relies on the distinction of three types of creativity that complementarily contribute to the creative process through shifts in the activation of their substrates in the brain: the deliberate, spontaneous and flow types of creativity. The latter is a hybrid and embodied type, in which movement and physical activity meet creativity. We then focus on the most fascinating contribution of unconscious processes and mind wandering to spontaneous and flow modes of creativity, exploring what happens when the individual apparently takes a break from a deliberate and effortful search for solutions and the creative process progresses through an incubation phase. This phase and the overall creative process can be facilitated by physical activity which, depending on its features and context, can disengage the cognitive control network and free the mind from filters that constrain cognitive processes or, conversely, can engage attentional control on sensorimotor and cognitive task components in a mindful way. Lastly, we focus on the unique features of the outer natural environment of physical activity and of the inner environment during mindful movements that can restore capacities and boost creativity.