Dependence Of Flow Rate Research Articles

Temperature dependence of inertial pumping in microchannels

Inertial pumping is a promising new method of moving fluids through microchannels but many of its properties remain unexplored. In this work, inertial flow rates are investigated for different channel lengths, operating temperatures, and resistor pulse energies. The flow in closed channels is visualized by adding fluorescent tracer beads to the test fluid (pure water). A robust methodology of extracting flow rates from high-resolution video recordings is developed. Flow rates are found to scale inversely with the channel length. The observed dependence is explained based on a simple phenomenological “kick” model of inertial pumping. Flow rates are also fitted to the more fundamental one-dimensional model of inertial pumping from which the intrinsic drive bubble strength is extracted. The measured flow rates vary strongly with temperature. For well-developed drive bubbles, flow rates at T=70 °C are about 12× higher than at T = 30 °C. Three separate effects contribute to increasing flow rates at high temperatures: (i) lower viscosity of the test fluid, (ii) a stronger drive bubble, and (iii) increasing mechanical efficiency of the pump, i.e., better conversion of the drive bubble strength to unidirectional post-collapse kick. Relative contributions of the three effects are quantified. The energy dependence of flow rates exhibits a clear saturation behavior. The bubble strength is fitted to a phenomenological saturation model. In the end, a complete predictive length-temperature-energy model of flow rates is constructed. The observed strong temperature dependence of inertial pumping should be considered when designing microfluidic workflows. It also highlights the need for integrated flowmeters that could stabilize complex flow patterns via sensory feedback.

Mobile pneumatic transporter for snow and garbage removal from roofs and house areas

Snow removal from roofs and near-house territories is relevant for the Perm Territory in the winter. The article discusses a mobile pneumatic transporter for garbage and snow removal consisting of a fan, a loading bin, an ejector chamber, and a vibrator. The main novelty of the plant is the use of polyethylene film for transport ducts. Air ducts were made by soldering with a hot iron. In the suture allowances, sutures were made to hang air ducts on a cable when removing snow from the roof. The calculation of the ejection funnel for the fan FS-2101/SP 220D is given in the work. As the funnel body, a plumbing two-rib tee with a diameter of 150 mm was used, in which a confuser of Æ100 mm was made. Since there is no data in the literature on the coefficient of friction of polyethylene, measurements of the total pressure losses in the system from the funnel to the final point of unloading, the dependence of the air flow rate and the suction rate from the loading hopper were made on the forty-meter air duct. After the calculations, a mixing chamber with a diameter of 125 mm was added to the tee. The pneumatic transporter demonstrated the ability to move snow to a distance of 40 meters at a speed of 10 m/s. Snow capacity is 9 cubic meters per hour. When removing snow from the roof along the air duct suspended with a slope of 1: 4, the snow can slide without the fan turned on. The pneumatic transporter can be used as a loader to a height of at least 4 m. The advantage of our pneumatic transporter over snowplows is the electric fan drive. This allows you to store the installation in the utility rooms of a residential building, without violating fire safety. The film ducts are compactly folded into a storage roll.

Dependence of the Piezoelectric Micropump Operating Mode on Its Geometry

A mathematical and computer axisymmetric models in which periodic oscillations of ring piezoelectric actuators placed on an elastic tube of circular cross-section leads to radial deformations of the tube is constructed. The result of these displacements is a local compression of the microchannel, which leads to changes in its volume and the corresponding pushing of the fluid. If a non-symmetrical oscillation scheme is used, the average fluid flow over the period will be non-zero and the device can be used as a micropump. The aim of the work is a computer study of the geometric features of an axisymmetric piezoelectric micropump, taking into account the processes of heat transfer by a fluid in the channel. The dependence of the average fluid flow rate on the channel parameters and the frequency of oscillations of the piezoelectric actuators is determined by the method of factorial experiment. The parameters preventing heat backflow have been determinate, which makes it possible to use a device for supplying coolant to a microgripper cooling system.

Розроблення катоду, стійкого до умов експлуатації у вакуумній камері

The aim of this work is to develop a thermoemission cathode that would ensure the required operating parameters and remain operable after long, several-day, exposure to the air without any additional ampulization. Cathode thrmoemitter degradation (“poisoning”) processes are overviewed. The problem of degradation of tungsten-barium cathodes is caused by the penetration of chemically active substances (for example, oxygen) into the interior space of a cathode. The “poisoning” process is so complex that it can hardly be simulated by simple theoretical methods. Because of this, the cathode “poisoning” degree under exposure to the atmosphere is usually assessed using experimental data. The analysis of publications on the resistance of cathode emitters to atmospheric exposure showed that one of the most promising solutions to the cathode “poisoning’ problem is the use of an emitter based on barium scandate. A cathode construction diagram was chosen, and a laboratory prototype cathode was made. The current dependence of the discharge voltage at different xenon flow rates and the xenon flow rate dependence of the discharge voltage at different currents were studied experimentally (xenon was the plasma-forming gas). During the trests, the cathode was periodically removed from the vacuuum chamber to inspect it for further use, the maximum duration of continuous exposure to the air was 14 days, and the resets did not reveal any significant change in the performance. The use of barium scandate as an emission-active substance for the thermoemission cathode improved its resistance to atmospheric exposure. The practical use of the cathode developed in experimental studies, for example, in the vacuum chamber of the plasmaelectrodynamic setup of the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, will eliminate frequent cathode replacements, thus significantly speeding up research activities.

Capillary ionic liquid electrospray: beam compositional analysis by orthogonal time-of-flight mass spectrometry

Orthogonal time-of-flight mass spectrometry has been used to characterize the kinetic energy and charged species distributions from an in vacuo electrospray ion source for four different ionic liquids at volumetric flow rates between 0.3 and 3.3 nanolitres per second. In all cases, the mass spectra revealed charged species consisting of singly charged and multiply charged ions as well as two broad, unresolved droplet distributions occurring in the 104 to 106 atomic mass unit per charge range. The mean jet velocity and mean jet breakup potential were established from analysis of the energy profile of the high mass-to-charge droplets. At the jet breakup point, we find the energy loss and the jet diameter flow rate dependence of the electrospray beam to be similar to that determined by Gamero-Castaño (Phys. Fluids, vol. 20, 2008, 032103; Phys. Rev. Fluids, vol. 8, 2021, 013701) for 1-ethyl-3-methylimidazolium bis(trifluromethylsulfonyl)imide at similar volumetric flow rates. Similar trends are observed for all four liquids over the flow regime. A jet instability analysis revealed that jet electrification and viscous effects drive the jet breakup from the case of an uncharged, inviscid jet; jet breakup occurs at droplet and jet radius ratios that deviate from 1.89. Using the analytically determined ratio and the beam profile, different species are modelled to reconstruct the mass spectra; primary droplets constitute only a fraction of the total species present. The populations of the species are discussed.

Simulation of a two-dimensional binary gas mixture outflow into vacuum through a thin slit on the basis of direct solution of the Boltzmann kinetic equation

Two-dimensional binary gas mixture outflow from a vessel into vacuum through a thin slit is studied on the basis of direct solution of the Boltzmann kinetic equation. For evaluation of collision integrals in the Boltzmann equation a conservative projection method is used. Numerical simulation of a two-dimensional argon-neon gas mixture outflow from a vessel into vacuum was performed. Graphs of mixture components flow rate dependence on time during the flow formation, as well as fields of molecular density and temperature for steady-state regime, were obtained.

Simulating Core Floods in Heterogeneous Sandstone and Carbonate Rocks

AbstractThe characterization of multiphase flow properties is essential for predicting large‐scale fluid behavior in the subsurface. Insufficient representation of small‐scale heterogeneities has been identified as a major gap in conventional reservoir simulation workflows. We systematically evaluated the workflow developed by Jackson et al. (2018), https://doi.org/10.1029/2017wr022282 for use on rocks with complex porosity and capillary heterogeneities. The workflow characterizes capillary heterogeneity at the millimeter scale. The method is a numerical history match of a coreflood experiment with the 3D saturation distribution as a matching target and the capillary pressure characteristics as a fitting parameter. Coreflood experimental datasets of five rock cores with distinct heterogeneities were analyzed: two sandstones and three carbonates. The sandstones exhibit laminar heterogeneities. The carbonates have isotropic heterogeneities at a range of length scales. We found that the success of the workflow is primarily governed by the extent to which heterogeneous structures are resolved in the X‐ray imagery. The performance of the characterization workflow systematically improved with increasing characteristic length scales of heterogeneities. Using the validated models, we investigated the flow rate dependency of the upscaled relative permeability. The findings showed that the isotropic heterogeneity in the carbonate sample resulted in non‐monotonic behavior; initially the relative permeability increased, and then subsequently decreased with increasing flow rate. The work underscores the importance of capturing small‐scale heterogeneities in characterizing subsurface fluid flows, as well as the challenges in doing so.

Rheology of Immiscible Two-phase Flow in Mixed Wet Porous Media: Dynamic Pore Network Model and Capillary Fiber Bundle Model Results

Immiscible two-phase flow in porous media with mixed wet conditions was examined using a capillary fiber bundle model, which is analytically solvable, and a dynamic pore network model. The mixed wettability was implemented in the models by allowing each tube or link to have a different wetting angle chosen randomly from a given distribution. Both models showed that mixed wettability can have significant influence on the rheology in terms of the dependence of the global volumetric flow rate on the global pressure drop. In the capillary fiber bundle model, for small pressure drops when only a small fraction of the tubes were open, it was found that the volumetric flow rate depended on the excess pressure drop as a power law with an exponent equal to 3/2 or 2 depending on the minimum pressure drop necessary for flow. When all the tubes were open due to a high pressure drop, the volumetric flow rate depended linearly on the pressure drop, independent of the wettability. In the transition region in between where most of the tubes opened, the volumetric flow depended more sensitively on the wetting angle distribution function and was in general not a simple power law. The dynamic pore network model results also showed a linear dependence of the flow rate on the pressure drop when the pressure drop is large. However, out of this limit the dynamic pore network model demonstrated a more complicated behavior that depended on the mixed wettability condition and the saturation. In particular, the exponent relating volumetric flow rate to the excess pressure drop could take on values anywhere between 1.0 and 1.8. The values of the exponent were highest for saturations approaching 0.5, also, the exponent generally increased when the difference in wettability of the two fluids were larger and when this difference was present for a larger fraction of the porous network.

Non-parametric dynamical estimation of blood flow rate, pressure difference and viscosity for a miniaturized blood pump.

Blood pumps are becoming increasingly important for medical devices. They are used to assist and control the blood flow and blood pressure in the patient's body. To accurately control blood pumps, information about important hydrodynamic parameters such as blood flow rate, pressure difference and viscosity is needed. These parameters are difficult to measure online. Therefore, an accurate estimation of these parameters is crucial for the effective operation of implantable blood pumps. In this study, in vitro tests with bovine blood were conducted to collect data about the non-linear dependency of blood flow rate, flow resistance (pressure difference) and whole blood viscosity on motor current and rotation speed of a prototype blood pump. Gaussian process regression models are then used to model the non-linear mappings from motor current and rotation speed to the hydrodynamic variables of interest. The performance of the estimation is evaluated for all three variables and shows very high accuracy. For blood flow rate - correlation coefficient ( = 1, root mean squared error () = 0.31 ml min-1, maximal error () = 9.31 ml min-1; for pressure = 1, = 0.09 mmHg, = 8.34 mmHg; and for viscosity = 1, = 0.09 mPa.s, = 0.31 mPa⋅s. The current findings suggest that this method can be employed for highly accurate online estimation of essential hydrodynamic parameters for implantable blood pumps.

Gas outflow into vacuum over a forward- and backward-facing step in a wide range of rarefaction

The direct simulation Monte Carlo method has been applied to investigate the outflow of rarefied gas into vacuum over a forward- and backward-facing step. The non-equilibrium effects at the ends of the step channel have been taken into account by considering the geometry of sufficiently large regions directly adjacent to the inlet and outlet of the channel. The mass flow rate through a step channel as well as the gas flow field both inside the step channel and in the upstream and downstream regions have been calculated over a wide range of gas rarefaction. The calculation results have been compared with the corresponding data for a channel of constant cross-section. The system configuration has been found to have a pronounced effect on the simulation findings. The so-called Knudsen minimum has been established in the dependence of the mass flow rate on the gas rarefaction, and a gas circulation zone has been found in the flow field.

Development of PEGylated chitosan/CRISPR-Cas9 dry powders for pulmonary delivery via thin-film freeze-drying

Gene therapy and more recently, gene editing is attractive via pulmonary delivery for enhanced regional targeting. However, processing of sensitive therapeutics into dry powders for inhalation can be problematic due to relatively stressful spraying or milling steps. Thin-film freeze-drying (TFFD) has attracted attention with its promising application in the production of DPI formulations possessing respirable particle size range (1–5 µm) particularly for thermally or shear sensitive therapeutics. In this study, gene editing dry powder formulations containing PEGylated chitosan/CRISPR-Cas9 nanocomplexes were prepared by TFFD. To evaluate stability during processing, nanocomplex size, zeta potential and transfection efficiency of reconstituted formulations were evaluated, and six potential DPI formulations were identified and characterized in terms of geometric particle size, powder surface morphology, and crystallinity. It was found that two formulations containing 3% mannitol with or without leucine were identified as suitable for inhalation with a desired aerodynamic performance. The flow rate dependency and inhaler dependency of these two formulations were also evaluated at different flow rates (60 L/min and 45 L/min) and different inhaler devices (RS01 DPI and HandiHaler) using NGI testing. This study demonstrated that TFFD processing of CRISPR-Cas9 polymer nanocomplexes resulted in a suitable dry powder for inhalation.

Simulation of liquid-steam critical flow from a pipe filled with granular layer

Based on the method of smoothed particles hydrodynamics a computational model of the critical flow of a vapor-liquid mixture from a pipe with a granular backfill has been developed. The dependence of critical mass flow rate from linear dimensions of the work area, the diameter of the grain filling and pipe length was determined. Numerical results were compared with available experimental data and numerical calculation demonstrates consistency with experimental data. Numerical data on the intensity of vaporization by the cross section of a pipe filled with granular backfill at initial values of the mass fraction of steam from 0.05 to 0.2 were obtained. The non-linearity of the vaporization rate during the mixture moving along the pipe with a decrease in intensity when moving along the length of the pipe is shown.

Calculation of the optimal diameter of the air intake of the propulsion system for small spacecraft

The article presents the calculation of the optimal diameter of the mesh channel of the air intake of the propulsion system of a small spacecraft, which operates on outboard air. Graphs of the dependence of the efficiency of the air intake on its diameter, the dependence of the mass flow rate of particles m on the diameter of the air intake are obtained. The analysis of the environmental friendliness of creating a propulsion system by the EIO method is carried out. The assessment of the harmfulness effect of the device on the environment during its operation was carried out.

Observations of the Impacts of Millimeter‐ to Centimeter‐Scale Heterogeneities on Relative Permeability and Trapping in Carbonate Rocks

AbstractCarbonate rock reservoirs are dominated by heterogeneity across a large and continuous range of spatial scales. We study the impact of heterogeneities on relative permeability and residual trapping for three carbonate rocks selected for their distinct spatial scales of rock texture. The Indiana limestone comprises millimeter‐scale heterogeneities, the Estaillades limestone consists of half‐centimeter‐scale heterogeneities, and the Edwards dolomite includes decimeter‐scale heterogeneity. Along with routine characterization of rock samples, steady‐state N2–deionized water drainage relative permeability measurements are made for each rock at two distinct total flow rates, at least 1 order of magnitude apart. The variation in flow potential across the core results in observations of fluid distribution, core‐average relative permeability, and residual trapping obtained for a range of continuum‐scale capillary number . The relative permeability curves for all rocks shift to the right of the water saturation axis with increasing flow potential; the nitrogen relative permeability increases while the water relative permeability decreases. However, the magnitude of the shift depends on the spatial scale of heterogeneity. An inspection of 3D saturation distributions in the cores and estimation of the capillary numbers of flow shows that the rock with the largest heterogeneity is capillary flow dominated throughout the range of injection rates tested; observations in the Indiana and Estaillades carbonates traverse capillary to viscous dominated flow regimes, with commensurate flow rate dependence in the relative permeability. In all cases, residual trapping is poorly described by the Land model.

Researches of technological mode of operation of gas wells with a single-lift elevator at a critical speed of upper flow

The article discusses the modes of movement of gas-liquid flows in relation to the operating conditions of waterlogged gas wells at a late stage of field development. Algorithms have been developed for calculating gas well operation modes based on experimental work under conditions that reproduce the actual operating conditions of flooded wells of Cenomanian gas deposits. The concept of calculating the technological mode of operation of gas wells with a single-row elevator according to the critical velocity of the upward flow is considered based on the study of the equilibrium conditions of two oppositely directed forces: the gravity of water drops directed downward and the lifting force moving water drops with a gas flow directed upward. A calculation was made according to the method of the averaged physical parameters of formation water and natural gas in the conditions of flooded Cenomanian gas wells in Western Siberia. The results of a study of the dependence of the critical flow rate of Cenomanian wells on bottomhole pressure and diameter of elevator pipes are presented.

РАЗРАБОТКА МЕТОДОВ И СРЕДСТВ УПРАВЛЕНИЯ АЭРОГАЗОДИНАМИЧЕСКИМИ ПРОЦЕССАМИ НА ДОБЫЧНЫХ УЧАСТКАХ

The practical development of the algorithm for optimal control of mine ventilation was preceded by comprehensive studies of the specific features of mining sites in order to obtain their mathematical description. The latter includes the static and dynamic characteristics of objects, i.e. the relationship between input and output values. The purpose of the research: to develop methods and management tools aerogasdynamics processes on mining sites of coalmines. Research methods. The methodology based on the system approach; modern methods of mathematical statistics, decision theory; mathematical logic devices; factor analysis; mathematical modeling; set theory and system analysis. To determine the dynamic characteristics of aerogasodynamic processes, experimental methods were used, divided into active and passive. The active method consists in con-structing a dynamic model of airing objects by approximating the transition curve obtained because of special effects on the airing object with an analytical expression. Statistical dynamics methods were used to obtain dynamic characteristics based on normal operation data. The method of correlation analysis was used. Results of research: experimental verification showed that the maximum relative error of in determining the methane concentration from the static characteristic constructed using a modified technique does not exceed 10 %. The value of the error was determined by comparing the static characteristic obtained by the modified correlation analysis method with the exact static characteristic of the airing object. The latter were found with regard to dynamic properties of the object and additive structures aerogas dynamics processes. Conclusion. The method of correlation analysis can be used to determine the dependence of the methane flow rate on the airflow rate in the steady-state mode, i.e. the static characteristic q = f (Q) for the site and lava. To determine the static characteristics based on the data of normal operation with a limited observation interval (5-10 days), a modified method of correlation analysis is proposed. Small values of the relative error of indicate the possibility and feasibility of using a modified correlation analysis technique to construct a static characteristic of the airing object based on random processes of methane concentration and air flow obtained during normal operation of the site. The static characteristics C= f (Q) and q= f(Q) are widely used to determine the mathematical expectations of the methane concentration and flow rate of mining sites, in the modeling of ventilation facilities and in the analysis and synthesis of mine ventilation control systems.

Bounds on the Rate-Dependent Plastic Flow of Tantalum up to 75 GPa

We report on the continued development of thermodynamics-based analysis of shock waves propagation with the objective of extracting information related to materials strength at high strain rates and pressures. Building on previous results reported for peak stresses of 10 GPa and 25 GPa, we present a series of three-step gas-gun shock experiments designed to explore the pressure and strain rate dependence of plastic flow in polycrystalline tantalum. These experiments at nominal peak stresses of 50 GPa and 75 GPa show the irreversible deformation before pullback to be almost entirely confined to the shock loading, with negligible plastic relaxation on the post-shock plateau. We also add a reverse-ballistics shot at 25 GPa, which was designed to reveal the pullback response with negligible interference from free-surface effects. General thermodynamic considerations allow us to place bounds on the plastic behavior even for parts of the curve that change far too rapidly for the velocimetric time resolution of (conservatively) ~ 5 ns. To analyze the data, we found it necessary to substantially improve the interpolation/extrapolation scheme in order to improve its robustness, flexibility and range of applicability. We describe the new scheme based on splines, as well as an extension of free-surface corrections to the post-shock rarefaction waves. Reanalysis with the new scheme produces results essentially within the error bars previously reported, showing that the known systematic errors associated with free-surface effects are relatively inconsequential for determining thermodynamic paths.

The role of the hopper angle in silos: experimental and CFD analysis

In this work, we reported experimental and numerical results of granular flows in silos and hoppers. We used a very flexible experimental setup, allowing us to explore the entire domain of the hopper angles. In addition, the granular flow was also studied numerically using Computational Fluid Dynamics. First, the numerical protocol was validated, comparing the output with experimental data of mass flow rate. In general, we obtained a good quantitative agreement between numerical and experimental results using a single set of the model parameters. Remarkably, the numerical results reproduced very well the weak non-monotonic behavior of the mass flow rate dependence on the hopper angle obtained experimentally. Stepping forward, we examined the scaling properties of the simulated velocity v(r) and density $$\phi (r)$$ profiles at the outlet region. Finally, we also analyzed the velocity and volume fraction field inside the silo. The outcomes suggested that fast dynamics at orifice perturbs the system distinctly, depending on the hopper angle. Interestingly, small and large angles showed a larger zone of influence in comparison with intermediate angles.

Nanocarbon Additives Application in the Polyvinyl Chloride Siding Panels Manufacture

With the development of building technologies, there is a need for new finishing materials that must meet the requirements of modern standards. This concerns not only the pricing policy, but also the high quality of promising materials, that first of all, is manifested in strength characteristics. In order to strengthen and preserve the heat-insulating properties and corrosion resistance, it is proposed to introduce schungite of type III of various grades in the formulation of siding panels made of polyvinyl chloride (PVC). The analysis of the quality indicators of PVC panels was carried out and three main indicators were identified: melt flow rate; Charpy impact strength; bending stress. PVC siding panels with the addition of shungite were produced by injection molding. As a result of experimental studies, the dependence of the Charpy impact strength of PVC panel samples without notching and bending stress on the bulk density of schungite was revealed, and scattering diagrams of the dependence of the melt flow rate on the polymerization time and the melt flow rate on the PVC concentration were constructed. The effect of schungite concentration of various grades on the melt flow rate was revealed. The dependence of shungite application as a reinforcing filler on the decrease in the melt flow rate in comparison with the traditional filler is determined.

Comparison of Ejection Plant Variants Under Conditions of Natural Gas Pumping Pressure Reduction

In the process of gas main transportation, repair work is periodically required with cutting off the extended section and emptying the internal cavity of the pipeline. According to the established practice, gas from the cut-off section is released into the atmosphere. Ejectors may be involved in gas scavenging, but due to pressure reduction in the cut-off area, it is necessary to ensure high efficiency of the gas ejection unit. It is proposed to compare different configurations of ejectors at reduction of pumping gas pressure (single-stage ejector, ejector with inner cone, two-stage ejector). The ejector parameters are defined using the ANSYS Fluent CFD package. For each version of ejection unit, a graph is drawn on the dependence of the intake gas flow rate on the intake gas pressure, the inner cone position in the nozzle and the active gas pressure in the first stage of the ejector.