Wide Range Of Flow Rates Research Articles

The vegetation of the small rivers of Novosibirsk Region (a syntaxonomic essay)

Information on the aquatic and semiaquatic vegetation of the major watercourses of West Siberia is relatively scarce, while this of small rivers is practically absent. There are 430 rivers whose length exceeds 10 km within the Novosibirsk Region. The aim of our work was to study the phytocenotic diversity of their aquatic and semiaquatic vegetation. 130 geobotanical relevés were performed by the authors in July–August 2003–2005. The object was aquatic communities formed by true aquatic (submergent and floating-leaved) plants and semiaquatic ones with emergent plants and these of water′s edge. In total 10 watercourses were studied (Table 1): 2–3 in each of five geomorphologic regions within the forest-steppe zone (Table 2). The upper, middle and lower courses (Fig. 1, Table 1) with the length of 2–2.5 km were studied in each case to ensure the 4–5 repetition of main elements (stream pools and ridges) that would give a reliable information on their flora and vegetation. The sample plots were selected above the settlements, whenever possible in sites with no to intensive anthropogenic impact. The data were collected according to J. Braun-Blanquet (1964) approach. The relevés were done on the sample plot of 100 m2 placed in the most homogeneous part of the community or, in case of its smaller area, within the natural boundaries. The following scale was used for abundance estimation: r — the species is extremely rare; + — rare, small cover; 1 — the number of individuals is large, the cover is small or individuals are sparse, but the cover is large; 2 —cover of 5–25 %; 3 — 26–50 %; 4 — 51–75 %; 5 — more than 75 %. The date on water depth, transparency (on a white Secchi disk with a diameter of 30 cm), temperature and the flow rate were obtained. The soil mechanical composition and color, the degree and nature of anthropogenic impact on vegetation and river banks were quantified. Water samples for general chemical analysis were taken in the middle course of each river. Computer programs TURBOVEG and MEGATAB (Hennekens, 1996) were used for database. The syntaxonomic affiliation of phytocenoses was determined using modern literature (Bobrov, Chemeris, 2006; Vegetace..., 2011; Chepinoga, 2015; Landucci et al. 2015; Mucina et al., 2016, etc.). 36 associations and 3 communities belonging to 12 alliances, 9 orders, and 5 classes have been identified (Tables 3–14, Fig. 2–9). Such great syntaxonomic diversity is determined by the significant ecotopic variety, the variability of substrates, the wide range of water flow rates and the different water trophicity. For comparison, 26 associations, 13 variants, 2 communities were identified in the study of 50 rivers of Lithuania (Sinkyavichene, 1992); altogether 84 associations are known for the Upper Volga region as a whole (Bob­rov, Chemeris, 2006), while 45 ones were recorded previously in 130 watercourses of this region (Bobrov, 1999). Information on small river macroalgae cenoses in the study area is partially reflected in the paper published earlier (Bobrov et al., 2005).

Gas volume and flow-rate measuring complex

Nowadays increasing the accuracy and reliability of measuring natural gas flow-rate is an urgent problem. In article is offered to increase the reliability of measuring the gas volume and flow-rate in a wide range of flow-rates by constructing a measuring complex with a few measuring devices based on different principles of action. The most rational structure of the device or complex with reduction the influence of elements on the output error signal can be selected by structural methods. The results of investigation of the natural gas flow-rate measuring complex and evaluation the level of mutual influence of the design parameters on the metrological characteristics of the whole complex are given. Particular attention is paid to determining the definite location of serial measuring devices along the length of the instrumentation system, which provides a minimum loss of gas flow energy and high accuracy of measuring its volume and volume rate. The optimal dimensional geometric form of the measurement node in measuring complex with different physical types of primary transducers will provide high accuracy and reliability of measurement in a wide range with minimization of pressure loss and flowmeters price.

Numerical simulation of electrospraying in the cone-jet mode

This article solves numerically the equations of the leaky-dielectric model applied to cone jets. The solution is a function of the properties of the fluid and its flow rate, universal in that it does not depend on the geometry and potential of the electrodes. This is made possible by the use of the potential field generated by a semi-infinite Taylor cone as a far-field boundary condition. The numerical solution yields the current emitted by the electrospray, which compares well with experimental data, and detailed information about the velocity, surface charge, electric field and the position of the free surface. These characteristics are generally inaccessible through experiments, and are needed to understand the relative importance of competing processes and the dominant physics. The simulations investigate the liquids tributyl phosphate and propylene carbonate (dielectric constants of 8.91 and 64.9 respectively), in a wide range of electrical conductivities and flow rates. The simulations show that the position of the surface, expressed in units of the characteristic length $r_{c}$, is largely invariant regardless of the physical properties and flow rates of the liquids. The surface charge falls below its equilibrium value along the transition from cone to jet, with a deficit that increases with the ratio between the electrical relaxation and flow residence times. Several characteristics of the cone jet are functions of the dielectric constant, which is consistent with the importance of charge relaxation effects (i.e. with the absence of surface charge equilibrium). The electric energy transferred to the transition region is largely transformed into viscous and ohmic dissipation, and conversion into kinetic energy only dominates once most of the current is fixed on the surface.

Rapid and steady concentration gradient generation platform for an antimicrobial susceptibility test

A simple microfluidic concentration gradient generator (MCG) was developed to create concentration gradients on a centimeter scale with a wide range of flow rates. Four groups of inlets (sample and buffer) were successively connected to the main channel to determine the location of inlets and the type of laminar flow and to create the concentration gradients. Nine micromixing channels were derived from the main channel to efficiently mix laminar flow. A micromixing channel whose mixing index was higher than that of a conventional serpentine mixing channel was designed by combining a square wave structure and microchannel sidewall grooves. A spindle-shaped chamber was set at the end of the mixing channel to observe the gradients. The computational fluid dynamic software Fluent was used to predict concentrations by calculating the average mass fraction at the cross section of each outlet. Theoretical simulations indicated that linear concentration gradients would be achieved within seconds in accordance with the fast micromixing principle at a flow rate of 2280 μL/min, and the gradient shape was steady regardless of the flow rate, which was affected by the location of inlet ports. The uniformity of the mass fraction achieved by the improved mixing channel was better than that of conventional serpentine micromixing channel. The theoretical simulations were verified through the generation of a concentration gradient of methylene blue water solution. Multiple concentrations of an antibacterial drug (ceftizoxime) generated by this MCG were utilized for an antimicrobial susceptibility test using Escherichia coli. Results revealed that the MCG showed potential for concentration gradient-related biochemical study.

Process stabilization during reactive high power impulse magnetron sputtering of Ce/Gd target

In this study, a simple approach to stabilize reactive high power impulse magnetron sputtering process in the transition zone between the metallic and oxide modes was investigated. The method is based on the use of peak current value as feedback and control signal. It was shown that the change in the state of the target surface causes almost instantaneous change in the amplitude and shape of the current pulses. To stabilize the deposition process, the pulse frequency was regulated to maintain a constant maximum discharge current. The hysteresis behavior and the variations of the pulse current waveforms over a wide range of O2 flow rates and pulse frequencies during a reactive HiPIMS deposition of gadolinia-doped ceria (GDC) thin films in an Ar-O2 atmosphere were examined. Stable process conditions were maintained at the O2 flow from 0.9 to 3.9 sccm by adjustment of the pulse frequency from 1.45 to 2.9 kHz. GDC films deposited using peak current regulation exhibited a stable stoichiometry and high deposition rate in comparison with films obtained without process stabilization.

Retention time prediction in thermally modulated comprehensive two-dimensional gas chromatography: Correcting second dimension retention time modeling error

Thermodynamic retention modeling to a thermally modulated comprehensive two-dimensional gas chromatography (GC × GC) system run under constant flow is performed. Significant errors in modeled second dimension retention time (tr,2) were observed, in line with past work on thermally modulated GC × GC modeling. A comprehensive study of tr,2 modeling error for alkane separations across a wide range of heating ramp rates and carrier gas flow rates was performed. Modeling errors were found to be systematic and a function of analyte elution temperature and mobile phase velocity. A model to account for these systematic errors was generated, and associated coefficients were determined which reduced average tr,2 retention time error in 144 hydrocarbon separations by an order of magnitude resulting in significant improvement in prediction accuracy. The model was used to correct the separation of 139 Grob mix analyte separations, providing an average tr,2 modeling error of 0.030 ± 0.022 s. The model successfully predicted the separation of n-alkanes on a longer second dimension column configuration.

Experimental and numerical investigation binary mixture mass transfer in a gas – Liquid membrane contactor

CO2 removal from binary mixture gaseous streams using hollow fibers membrane module under physical absorption (water) has been investigated. The impact of the gas composition on the mass transfer efficiency was experimentally investigated with a CO2/CH4 mixture of varying composition (yCO2in=10−90%), covering a wide range of process: natural gas sweetening (5–10% CO2), post-combustion carbon capture (10–15% CO2), for biogas upgrading to biomethane (35–50% CO2), … As expected, the absorbed CO2 flux is increasing with the CO2 partial pressure. Yet the absorbed CO2 flow is multiplied by a factor up to 15 between a 10% and a 90% inlet CO2 molar fraction, while applying a factor 9 to the inlet flow parameters. This underlines the existence of a non-trivial behavior.In the meantime, a 2D numerical model describing the absorption of CO2 in a binary gas mixture, based on the internal module geometry and on a local description of the hydrodynamics was proposed. Its development showed that in order to capture the key phenomena, a proper description of mass transfer in transition zone (Knudsen number around 0.34) is mandatory. Implementing this description allowed the model to accurately describe mass transfer over a wide range of gas composition and flow rate, without relying on any fitted parameter.

Mapping electrospray modes and droplet size distributions for chitosan solutions in unentangled and entangled concentration regimes

Chitosan is a natural polymer that exists as a polyelectrolyte in acidic aqueous solutions. The solution viscosity strongly depends on the polymer’s molecular weight and concentration in the solution, and the solution pH. Microparticle production by electrospraying is of significant interest in the drug delivery applications of this biocompatible polymer. We report herein a study aimed at empirical understanding of the influence of electrospray process parameters on the size distribution of microdroplets of chitosan solutions with different molecular weights and concentrations. How the nature of interchain interactions in the solution affects the electrospray mode, was studied for different applied voltages, V, over a wide range of solution flow rates, Q. Stable cone-jets were observed only for solutions in the unentangled regime. Unlike solutions of non-polymeric electrolytes of comparable viscosities, the chitosan droplet size distribution generally showed a strong dependence not only on Q but also on V and the solution viscosity. Carrying out the electrospraying process at a higher voltage in the stable cone-jet mode resulted in smaller and more narrowly dispersed droplets. For the droplets produced in this mode, We∼Re1.79, where We and Re are the droplet Weber and Reynolds numbers, respectively. The order of dependence of the Sauter mean droplet diameter on Q was found to be 0.26. Diameters of droplets produced in (or close to) the precession mode exhibited a significantly weaker dependence on Q. For a given wt% concentration in solution, a polymer of lower molecular weight resulted in a lower droplet size polydispersity index.

Aerodynamic Similarity Principles and Scaling Laws for Windmilling Fans

Windmilling requirements for aircraft engines often define propulsion and airframe design parameters. The present study is focused on two key quantities of interest during windmill operation: fan rotational speed and stage losses. A model for the rotor exit flow is developed that serves to bring out a similarity parameter for the fan rotational speed. Furthermore, the model shows that the spanwise flow profiles are independent of the throughflow, being determined solely by the configuration geometry. Interrogation of previous numerical simulations verifies the self-similar nature of the flow. The analysis also demonstrates that the vane inlet dynamic pressure is the appropriate scale for the stagnation pressure loss across the rotor and splitter. Examination of the simulation results for the stator reveals that the flow blockage resulting from the severely negative incidence that occurs at windmill remains constant across a wide range of mass flow rates. For a given throughflow rate, the velocity scale is then shown to be that associated with the unblocked vane exit area, leading naturally to the definition of a dynamic pressure scale for the stator stagnation pressure loss. The proposed scaling procedures for the component losses are applied to the flow configuration of Prasad and Lord (2010). Comparison of simulation results for the rotor-splitter and stator losses determined using these procedures indicates very good agreement. Analogous to the loss scaling, a procedure based on the fan speed similarity parameter is developed to determine the windmill rotational speed and is also found to be in good agreement with engine data. Thus, despite their simplicity, the methods developed here possess sufficient fidelity to be employed in design prediction models for aircraft propulsion systems.

Development of MEMS-based thermal mass flow sensors for high sensitivity and wide flow rate range

In the natural gas trade, mass flow metering is preferred to volume flow metering. In order to improve the measurement performance related to sensitivity within wide flow rate range of the mass flow meter, a novel design of a MEMS-based thermal mass flow sensor is proposed. To determine of the correlation between the sensing performance and geometry of sensor components, in this case the heater and the thermopile, models with various designs were fabricated using MEMS technology. Flow characteristic tests of the fabricated models were conducted in the low pressure gas flow standard system of KRISS. The effect of the distance ratio between the heater and thermopiles on the measurement performance of the thermal flow sensor was examined according to the flow rate range. The results presented that the basic models with the different distance ratio show different sensitivity characteristics. The non-uniform model proposed in this study show high sensitivity in both low and high flow rate region compared with models with a certain distance ratio.

Experimental study of flow field in geometric Type-I vortex chamber at low water abstraction ratio

ABSTRACTIn this paper, an attempt has been made to critically examine the flow field inside a cylindrical model vortex chamber type sediment extractor with 1.0 m diameter. Data on velocity distribution along tangential and radial directions have been collected by Programmable Electro Magnetic Shunt (PEMS) meter in a circular cylindrical model of vortex chamber in the laboratory. Data were for wide range of flow rate, water abstraction ratios, vertical, radial and transverse spacing. In this paper only result of one lowest water abstraction ratio that is 8% is presented. The results are presented in the form of graphical representation. Also, the segments with similar flow field have been identified.

Formation mechanisms and lengths of the bubbles and liquid slugs in a coaxial-spherical micro mixer in Taylor flow regime

One of the most important problems of the efficiency of mini and micro devices (with diameter larger than ∼1 mm) for gas-liquid systems is the maintenance of regular Taylor (slug) flow regime. The paper describes a coaxial-spherical mixer (CS-mixer), which allows to create a slug flow regime in a wide range of phase flow rates. For CS-mixer a flow map was build up and superimposed to that for C-mixer.It was shown experimentally with 2 mm ID microchannel that the position of the nozzle for the injection of the gas relative to the spherical extension of CS-mixer significantly affects the lengths of the bubbles and the slugs generated in the micromixer. Two nozzle positions in the narrowing part of spherical extension were considered as optimal from the point of view of uniformity of slug flow.For nozzle position D (middle cross-section), which was studied more detailed in this research, equations for bubbles and slugs lengths were obtained. Values of bubbles and slugs lengths calculated by these equations were compared with data of other authors for different types of micro-mixers. It was shown that CS-mixer allows to control the length of the bubbles and to generate bubbles with smaller length. The size of the slugs produced by CS-mixer demonstrated weaker dependence on superficial liquid flow rate compared to the other types of micromixers. Unexpected (for other types of micromixers) behavior of two-phase flow in microchannel by use of CS-mixer was observed: with growing gas superficial velocity the length of the bubbles is decreasing. Such behavior was explained by particular effects of bubble detachment from the nozzle during its formation in the spherical extension of CS-mixer.

The effects of the rotor-stator interaction on unsteady pressure pulsation and radial force in a centrifugal pump

An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport turbulence model for a wide range of flow rates. These unsteady interactions are mostly related to the unsteady radial force due to an imbalance in the pressure field at the impeller periphery. This force represents dynamic load that are one of the most important sources of vibration and hydraulic noise. Based on this phenomenon, this work analyzes and gives a more realistic prediction of the pressure fluctuation and the radial force during steady and unsteady calculation by considering the effect of the change in the pump operating point. Actually, the pressure fluctuations in the impeller and the volute were recorded by mounting nine monitoring points on the impeller and volute casing. The results of the existing analysis has proven that the pressure fluctuation is periodic due to the relative position of impeller blade to volute tongue. The characteristics of the time domain and frequency domain of the pressure pulsation were analyzed under different coupling conditions. Fast Fourier transform was performed to obtain the spectra of pressure pulsation. Besides, the steady and unsteady forces were calculated around the impeller periphery to fully characterize the pump behavior. The obtained pump performance curves were numerically compared with the experimental ones, and the outcome have shown an acceptable agreement between both curves.

Optimization of a Novel All-Vanadium Hybrid Redox Flow Battery/Mediator Supercapacitor

The increasing demand for renewable energy is reliant upon progress in energy storage, which is essential in smart-grid and transportation applications. Redox flow batteries have been a promising path for these applications with their very high specific energy, but they suffer from low specific power, slow response, and a low charge rate. In contrast, mediator supercapacitors display high specific power and a fast response rate with a high charge rate, but relatively low specific energy. A hybrid flow-battery/supercapacitor is fabricated and operated under different conditions to provide high specific energy and power along with performance capabilities across a wide range of charge rates, utilizing both physical and chemical charging methods within the cell. The porous electrodes of the electrochemical cell consisted of the Vanadium mediators (VOSO4 and VCl3), supercapacitor carbon black powder, and a polymer binder. A commercial ion exchange membrane was used as the separator. This investigation focuses on the effects of flow rate, charge rate, and mediator concentration on the performance of the hybrid device. Potentiostatic EIS (EIS), Cyclic Charge Discharge (PWR), and Cyclic Voltammetry (CV) measurements were conducted under a wide range of flow rates and mediator concentrations. The electrochemical kinetics of the mediators were evaluated using linear polarization methods. The results indicate that at a given current for PWR tests and scan rate for CV tests, both the flow rate and mediator concentration greatly impact the charge/discharge behavior, the total energy, and the efficiency of the hybrid system. The system performs over a wide range of currents with repeated cycling. A transition between capacitor-like behavior and battery-like behavior is observed.

Inertial focusing of microparticles in curvilinear microchannels with different curvature angles

Inertial microfluidics has become one of the emerging topics due to potential applications such as particle separation, particle enrichment, rapid detection and diagnosis of circulating tumor cells. To realize its integration to such applications, underlying physics should be well understood. This study focuses on particle dynamics in curvilinear channels with different curvature angles (280°, 230°, and 180°) and different channel heights (90, 75, and 60 µm) where the advantages of hydrodynamic forces were exploited. We presented the cruciality of the three-dimensional particle position with respect to inertial lift forces and Dean drag force by examining the focusing behavior of 20 µm (large), 15 µm (medium) and 10 µm (small) fluorescent polystyrene microparticles for a wide range of flow rates (400–2700 µL/min) and corresponding channel Reynolds numbers. Migration of the particles in lateral direction and their equilibrium positions were investigated in detail. In addition, in the light of our findings, we described two different regions: transition region, where the inner wall becomes the outer wall and vice versa, and the outlet region. The maximum distance between the tight particle stream of 20 and 15 µm particles was obtained in the 90 high channel with curvature angle of 280° at Reynolds number of 144 in the transition region (intersection of the turns), which was the optimum condition/configuration for focusing.

Heat transfer enhancement of micro-scale backward-facing step channel by using turbulators

Laminar forced convection heat transfer and fluid flow of micro-scale backward-facing step (MBFS) with different types of longitudinal vortex generators (VGs) is numerical analyzed. The governing equations are discretized by finite volume method. Four basic types of VG which are rectangular and triangular wings and winglets pairs are attached to an unheated upper wall behind the stepped wall in order to enhance the thermal performance of MBFS. Three inclination angles of VGs are considered namely; 30°, 45°, and 60° with a wide range of water flow rate. The thermal and hydraulic performance of MBFS with VG is evaluated by JF factor in order not to show the enhancement in the heat transfer only, but the increase in the pressure drop as well. The results showed that the use of VG in MBFS increases the heat transfer and pressure drop simultaneously. The best heat transfer enhancement with a little increase in the pressure drop is observed in the case of rectangular wing VG at an attack angle of 60° and Reynolds number of 180 whereas (NuVG/Nuo) = 1.221. JF factor increases with Reynolds number until 180 and then a steep decrease has been monitored.

Optical measurement of high-temperature melt flow rate.

This paper presents an optical method and system for contactless measurement of the mass flow rate of melts by digital cameras. The proposed method is based on reconstruction of melt stream geometry and flow velocity calculation by cross correlation, and is very cost-effective due its modest hardware requirements. Using a laboratory test rig with a small inductive melting pot and reference mass flow rate measurement by weighing, the proposed method was demonstrated to have an excellent dynamic response (0.1s order of magnitude) while producing deviations from the reference of about 5% in the steady-state flow regime. Similar results were obtained in an industrial stone wool production line for two repeated measurements. Our method was tested in a wide range of melt flow rates (0.05-1.2kg/s) and did not require very fast cameras (120frames per second would be sufficient for most industrial applications).

A novel cell design of vanadium redox flow batteries for enhancing energy and power performance

The Vanadium Redox Flow Battery (VRFB) is one of the most promising electrochemical energy storage systems considered to be suitable for a wide range of renewable energy applications. In this work, a novel cell structure is designed for VRFB, which includes embedded serpentine flow channels in a non-porous and non-brittle case. This new design eliminates end plates and gaskets to improve safety, extend life, and promote ease of assembly with fewer components than traditional VRFB cells. In particular, a key challenge of conventional graphite flow field plates in which solution penetration can occur due to an easily broken and porous structure is solved by using rigid impermeable polyvinyl chloride (PVC) sheets with flow channels embedded in the sheets. Various tests, such as cycling and polarization measurements of a wide range of current and flow rates, and Electrochemical Impedance Spectroscopy (EIS) for internal resistance analysis, are performed to compare new and traditional designs. The results show that the new design keeps cycling performance stable, with better stability and energy efficiency, than conventional VRFB cells do. High power performance is also observed for the same external cell size. In addition, an abrupt potential drop caused by high contact resistance between the current collector and a porous electrode is solved by introducing a layer of the patterned graphite sheet to improve contact and electronic conductivity and, also, to function as a flow channel. Finally, an economic analysis shows that the new design not only improves battery performance, but also lowers assembly costs and facilitates assembly.

Generation of Newtonian and non-Newtonian droplets in silicone oil flow by means of a micro cross-junction

In this paper the generation of non-Newtonian and Newtonian droplets in a continuous silicone oil flow through a micro cross-junction has been studied experimentally by focusing the attention on the behavior of the device at values of continuous Capillary number (Cac) larger than 0.01. Different liquids have been used as dispersed phase: (i) pure water; (ii) water with Tween 20; (iii) Xanthan gum aqueous solutions. A wide range of volumetric flow rates of the continuous and dispersed phase have been imposed at the inlets of the micro cross-junction with the aim to correlate the main droplet regimes (squeezing, dripping and jetting) to the continuous and dispersed Capillary number (Cac, Cad) and to the volumetric flow rate ratio (α). The role of the viscosity ratio of the immiscible liquids (λ) on the droplet regime is discussed. The experimental results confirm that the transition between squeezing and dripping depends mainly on the Capillary number associated to the continuous phase and not on the viscosity ratio. On the contrary, larger viscosity ratio values tend to reduce the Capillary number in correspondence of which the transition between dripping and jetting is observed. In addition, it has been observed that an increase in the viscosity of the dispersed phase tends to reduce the range of the operative conditions in correspondence of which monodispersed emulsions can be generated.

Behavior and dynamics of bubble breakup in gas pipeline leaks and accidental subsea oil well blowouts

Subsea oil well blowouts and pipeline leaks release oil and gas to the environment through vigorous jets. Predicting the breakup of the released fluids in oil droplets and gas bubbles is critical to predict the fate of petroleum compounds in the marine water column. To predict the gas bubble size in oil well blowouts and pipeline leaks, we observed and quantified the flow behavior and breakup process of gas for a wide range of orifice diameters and flow rates. Flow behavior at the orifice transitions from pulsing flow to continuous discharge as the jet crosses the sonic point. Breakup dynamics transition from laminar to turbulent at a critical value of the Weber number. Very strong pure gas jets and most gas/liquid co-flowing jets exhibit atomization breakup. Bubble sizes in the atomization regime scale with the jet-to-plume transition length scale and follow −3/5 power-law scaling for a mixture Weber number.