Fluid Dispersion Research Articles

Out of the box and into the workplace—the friction mechanics of worn shoes

Shoe tread reduces the risk of slips and falls by improving shoe-floor friction and under- shoe fluid dispersion. Shoe design and friction standards exist to improve shoe safety, though these stand...

The homotopy perturbation method for fractional differential equations: part 2, two-scale transform

PurposeThe purpose of this paper is to find an approximate solution of a fractional differential equation. The fractional Newell–Whitehead–Segel equation (FNWSE) is used to elucidate the solution process, which is one of the nonlinear amplitude equation, and it enhances a significant role in the modeling of various physical phenomena arising in fluid mechanics, solid-state physics, optics, plasma physics, dispersion and convection systems.Design/methodology/approachIn Part 1, the authors adopted Mohand transform to find the analytical solution of FNWSE. In this part, the authors apply the fractional complex transform (the two-scale transform) to convert the problem into its differential partner, and then they introduce the homotopy perturbation method (HPM) to bring down the nonlinear terms for the approximate solution.FindingsThe HPM makes numerical simulation for the fractional differential equations easy, and the two-scale transform is a strong tool for fractal models.Originality/valueThe HPM with the two-scale transform sheds a bright light on numerical approach to fractional calculus.

Effects of backward inclination on a pulsed jet in crossflow

The effects of the backward inclination angle on the flow and jet dispersion characteristics of a pulsed jet in crossflow were studied experimentally in an open-loop wind tunnel. The pulsations were created by a loudspeaker which installed at the bottom of a nozzle assembly. The instantaneous and time-averaged flow patterns were obtained using the laser-light sheet assisted smoke flow visualization method. The instantaneous and average velocities, turbulence intensities, integral turbulence time scales were probed using a hot-wire anemometer. The tracer-gas detection technique was applied to examine the fluid dispersion capability of the jet. With excitation, the axial jet pulsations were transferred to transverse oscillations after the jet was deflected by the crossflow. A small jet backward inclination angle could lead to an increase of jet-fluid dispersion and transverse jet spreading width. There existed a critical jet backward inclination angle of 20° at which the jet-fluid dispersion index and transverse jet spreading width attained the maximum values. Arranging the jet backward inclination angle at values smaller than 20° could induce an increase in dispersion of the pulsed jet in crossflow and benefit the industrial applications which required fast and efficient jet-fluid dispersion and mixing. • Jet backward inclination angle presented significant effects on axial mean velocities, turbulence intensities, and dispersion properties. • There existed a critical jet backward inclination angle of 20° at which the jet spreading width and dispersion attain maximum values. • At jet backward inclination angle smaller than critical value, increasing inclination angle could increase jet-fluid dispersion. • At jet backward inclination angle larger than critical value, increasing inclination angle would significantly decrease jet-fluid dispersion. • Arranging jet backward inclination angle at critical value could benefit industrial applications.

Phosphorylated xanthan gum-Ag(I) complex as antibacterial viscosity enhancer for eye drops formulation

Topical instillation of eye drops represents the treatment of choice for many ocular diseases. Ophthalmic formulations must meet general requirements, i.e. pH, osmolality, transparency and viscosity to ensure adequate retention without inducing irritation and the development of eye infections. We developed a phosphorylated xanthan gum–Ag(I) complex (XGP-Ag) showing pH (pH = 7.1 ± 0.3) and osmolality values (311 ± 2 mOsm/kg) close to that of human tears (pH = 6.5–7.6 and 304 ± 23 mOsm/kg) thanks to the presence of phosphate moieties along the chain. The presence of phosphate groups covalently bound to the XG chains avoids their dispersion in fluid, thus reducing the risk of corneal calcification. 0.02% w/v XGP-Ag solution showed high transparency (higher than 95% along the entire visible range), adequate refractive index (1.334 ± 0.001) and viscosity in the range: γ 1 s-1-10,000 s- 1 (26.4 ± 0.8–2.1 ± 0.4 mPa·s). Its cytotoxicity and capability to hinder bacterial proliferation was also verified.

Effects of Velocity and Permeability on Tracer Dispersion in Porous Media

During micro-scale tracer flow in porous media, the permeability and fluid velocity significantly affect the fluid dispersion properties of the media. However, the relationships between the dispersion coefficient, permeability, and fluid velocity in core samples are still not clearly understood. Two sets of experiments were designed to study the effects of tracer fluid flow velocity and porous medium permeability on the dispersion phenomenon in a core environment, using natural and sand-filled cores, respectively. From experimental data-fitting by a mathematical model, the relationship between the dispersion coefficient, flow velocity, and permeability was identified, allowing the analysis of the underlying mechanism behind this phenomenon. The results show that a higher volumetric flow rate and lower permeability cause a delay in the tracer breakthrough time and an increase in the dispersion coefficient. The core experimental results show that the dispersion coefficient is negatively correlated with the permeability and positively correlated with the superficial velocity. The corresponding regression equations indicate linear relations between the dispersion coefficient, core permeability, and fluid velocity, resulting from the micron scale of grain diameters in cores. The combination of high velocity and low permeability yields a large dispersion coefficient. The effects of latitudinal dispersion in porous media cannot be ignored in low-permeability cores or formations. These findings can help to improve the understanding of tracer flow in porous media, the design of injection parameters, and the interpretation of tracer concentration distribution in inter-well tracer tests.

Local analysis of electrostatic modes in a two-fluid E×B plasma

A local study of linear electrostatic modes, applicable to the dynamics perpendicular to the magnetic field in a plasma with crossed electric and magnetic fields, is presented. The analysis is based on a two-fluid model that takes into account the finite-electron-gyroradius effects through a rigorous gyroviscosity tensor and includes a dissipative friction force in the electron momentum equation. A comprehensive dispersion relation, valid for arbitrary electron temperature, is derived, which describes properly all the relevant waves for wavelengths longer than the electron Larmor radius. For a homogeneous and dissipationless plasma, such a fluid dispersion relation agrees with the long-wavelength limit of the kinetic electron–cyclotron-drift instability dispersion relation that extends the results to arbitrary short wavelengths. The general fluid dispersion relation covers different parametric regimes that depend on the relative ion-to-electron drift velocity and on the presence of equilibrium inhomogeneities and/or dissipation. Depending on such conditions, its roots yield as follows: two-stream instabilities, driven solely by the relative drift between species; drift-gradient instabilities, driven by the combination of the relative drift and equilibrium gradients; and drift-dissipative instabilities, driven by the combination of the relative drift and friction. Instability thresholds are determined and some distinctive unstable modes are described analytically.

Prospects for the use of nanofluids in heating systems

The desire to create new, improved working fluids for heat and mass transfer systems in the industry is gaining momentum. Now more and more researchers are being attracted to analyze the use of nanofluids in heating systems due to their improved thermal and physical properties. Nanofluids are a new type of dispersed fluids that consist of a carrier fluid in the form of which water can act, as well as polymer solutions and organic liquids, and solid particles, which are mainly particles of chemically stable metals and their oxides. The heat transfer characteristics of modern liquids are significantly improved by the addition of nanoscale solid particles with a diameter of less than 100 nm. Such liquids can be considered as promising applications in such areas as solar collectors, heat pipes, nuclear reactors, electronic cooling systems, automobile radiators, etc. The paper (publication) describes nanofluids as new energy-efficient types of working fluids for heat transfer. The most promising developments in the field of creating nanofluids from the point of view of increasing the heat transfer coefficient are presented and analyzed. Further possible promising ways of studying nanofluids are formulated.

Numerical prediction of Péclet number in small-sized fixed bed reactors of spheres

Fluid dispersion in small fixed bed reactors under single phase laminar flow conditions is evaluated through accurate predictions of axial Péclet numbers Peax using Direct Numerical Simulations (DNS). The fixed bed packing is obtained through the Discrete Element Method (DEM) code Grains3D. Peax numbers are computed from steady state simulations of the flow. An additional set of equations solving the spatial distribution of the moments of the age distribution is used. This gives access to local information on dead zones or bypasses. Computations are realized with the OpenFOAM® open-source library. Results are close to the experimental data. The DEM-OpenFOAM® workflow benefits from an accurate control of the fluid physical properties and packing geometry, thus leading to a faster production of data than an experimental approach.We first explore the influence of the reactor-to-sphere diameter ratio δ (δ < 4), fluid velocity and molecular diffusivity on the Peax number. The behavior proves much more complex than any previous report, and it can be qualitatively explained by looking at the packing structure. Then, we use the DEM-OpenFOAM® workflow to quantify the uncertainty on the Peax number when repeating the packing of a δ = 4 fixed bed reactor, and we propose that the uncertainty on the Peax number decreases as a function of the reactor length to the power of −0.5.

Capillary equilibrium of bubbles in porous media

In geologic, biologic, and engineering porous media, bubbles (or droplets, ganglia) emerge in the aftermath of flow, phase change, or chemical reactions, where capillary equilibrium of bubbles significantly impacts the hydraulic, transport, and reactive processes. There has previously been great progress in general understanding of capillarity in porous media, but specific investigation into bubbles is lacking. Here, we propose a conceptual model of a bubble's capillary equilibrium associated with free energy inside a porous medium. We quantify the multistability and hysteretic behaviors of a bubble induced by multiple state variables and study the impacts of pore geometry and wettability. Surprisingly, our model provides a compact explanation of counterintuitive observations that bubble populations within porous media can be thermodynamically stable despite their large specific area by analyzing the relationship between free energy and bubble volume. This work provides a perspective for understanding dispersed fluids in porous media that is relevant to CO2 sequestration, petroleum recovery, and fuel cells, among other applications.

Optimization Technology of Frequency Conversion Constant Pressure Control System of Mine Emulsion Pump Station in Electrical Engineering and Automation Specialty

No matter in metal mines or coal mines, an emulsion pump station has a wide range of application market and can play an important role. In this paper, the frequency conversion constant pressure control system of the mine emulsion pump station is taken as the research object. The two kinds of water-based drawing fluids used are dispersed drawing fluid and emulsion drawing fluid. After the intelligent level of the equipment reaches a very high level, an environmentally friendly, safe, and efficient Internet of Things technology system will be added. Combined with 3D laser scanning technology based on self-scanning of road contours, the blast method is input to the terminals of the emulsion pump station for automatic blast hole positioning and semiautomation of the emulsion pump station. Combined with 5 g communication and other intelligent key technologies, it realizes high-end functions such as fault self-diagnosis, remote operation, and remote monitoring of the emulsion pump station and rock drill, which can be called full intelligent stage. The results show that the initial friction coefficient of drawing fluid A lubrication is 0.21, and then, with the extension of time, the friction coefficient gradually decreases to 0.14. The initial friction coefficient of drawing fluid B is 0.22, then it decreases rapidly to 0.13, then it is stable at 0.17, and then it remains basically unchanged. When the temperature is 55°C, the initial friction coefficient is 0.16 and then decreases to 0.12. Therefore, the frequency conversion constant pressure control system of the mine emulsion pump station should be selected according to the environment and application scenarios.

Effect of vortex and entropy sources in sound generation for compressible cavity flow

The present study reports the effect of different source terms on the near and far-field acoustic characteristics of compressible flow over a rectangular cavity using hybrid computational aeroacoustics methodology. We use a low dispersive and dissipative compressible fluid flow solver in conjunction with an acoustic perturbation equation solver based on the spectral/hp element method. The hybrid approach involves calculating the base fields and the acoustic sources from a fluid simulation in the first step. In the next step, the acoustic solver utilizes the variables to predict the acoustic propagation due to the given sources. The validation of the methodology against benchmark cases provides quite accurate results while compared against the existing literature. The study is then extended to assess the importance of the entropy source term for the flow over a rectangular cavity. The predictions of hybrid simulations with vortex and entropy source terms reproduce the perturbation pressure values very close to the existing direct numerical simulation results. Moreover, the results suggest that the use of just the vortex source terms over-predicts the perturbation pressure near the source region. Finally, we have carried out detailed simulations with all the source terms to investigate the noise sources for compressible flow over the cavity for different Mach number ranges (M=0.4,0.5,0.6,0.7,1.5). The obtained acoustic spectra and the sound directivity are in close agreement with the reference experiment.

Fluid interfacial energy drives the emergence of three-dimensional periodic structures in micropillar scaffolds

Structures that are periodic on a microscale in three dimensions are abundant in nature, for example, in the cellular arrays that make up living tissue. Such structures can also be engineered, appearing in smart materials1–4, photonic crystals5, chemical reactors6, and medical7 and biomimetic8 technologies. Here we report that fluid–fluid interfacial energy drives three-dimensional (3D) structure emergence in a micropillar scaffold. This finding offers a rapid and scalable way of transforming a simple pillar scaffold into an intricate 3D structure that is periodic on a microscale, comprising a solid microscaffold, a dispersed fluid and a continuous fluid. Structures generated with this technique exhibit a set of unique features, including a stationary internal liquid–liquid interface. Using this approach, we create structures with an internal liquid surface in a regime of interest for liquid–liquid catalysis. We also synthesize soft composites in solid, liquid and gas combinations that have previously not been shown, including actuator materials with temperature-tunable microscale pores. We further demonstrate the potential of this method for constructing 3D materials that mimic tissue with an unprecedented level of control, and for microencapsulating human cells at densities that address an unresolved challenge in cell therapy. The revelation that fluid–fluid interfacial energy can drive structure formation in micropillar scaffolds offers a scalable way of synthesizing soft composites, which may have applications in building materials that mimic biological tissue.

Modeling and analysis of the effects of barrier height on automobiles emission dispersion

In this paper, a mathematical model has been developed that describes the characteristics of fluid flow and dispersion of pollutants in a certain quarter of Almaty city, Kazakhstan. The influence of traffic tidal flow was investigated based on the results of passing vehicles measurements as a source of pollution by the CFD method and on the spatial distribution of pollutants for different types of pollution. To validate the numerical algorithm and mathematical model, a test problem was performed. The RNG k-ε turbulence model was used as a turbulent model. The obtained data were compared with the measured and calculated values. After validation of the mathematical model, the main problem was characterized: the pollutant emissions process between houses using different types of pollution sources and the presence of different heights of barriers. The calculated data were compared with the obtained calculated values. In the course of various studies, it has been found that, despite different types of pollutants, the presence of barriers along the road reduces the concentration of harmful substances in the pedestrian zone air. And also the optimal height of this barrier along the road was chosen for maximum protection of the pedestrian part from harmful pollutants. And it was found that when using a barrier with a height of 3 m, the concentration value drops more than two times, as opposed to without a barrier, and a further increase in height is not economically profitable and does not give the desired results.

Fluid-like carbon dots-based ionic fluid towards high efficient lubricant nanoadditive of polyethylene glycol

Solid polyelectrolyte grafted carbon dots as a precursor were synthesized using citric acid and poly(sodium 4-styrene sulfonate) via pyrolysis route, which were then capped by block copolymer to produce solvent-free carbon dots-based ionic fluid (CDs-PSS-M2070). The tribological performance of CDs-PSS-M2070 under different concentrations and loads was evaluated in polyethylene glycol (PEG). The results verified that CDs-PSS-M2070 efficiently improved the friction-reducing and wear-resistance performance as well as the load-bearing capacity of PEG in a broad load. The addition of 1.0% CDs-PSS-M2070 reduced wear volume of 82.8% and friction coefficient of 73.5% under the load of 392 N. Owing to the excellent dispersion of carbon dots ionic fluid in PEG, CDs-PSS-M2070 could continue to transfer to the frictional interface and form a continuous carbon-rich oil-film, thereby enhancing friction-reducing and wear-resistance abilities efficiently.

Dense nanolipid fluid dispersions comprising ibuprofen: Single step extrusion process and drug properties

Dense nanolipid fluid (DNLF) dispersions are highly concentrated aqueous dispersions of lipid nanocarriers (LNCs) with more than 1015 lipid particles per cubic centimeter. Descriptions of dense nanolipid fluid dispersions in the scientific literature are rare, and they have not been used to encapsulate drugs. In this paper we describe the synthesis of DNLF dispersions comprising ibuprofen using a recently described twin-screw extrusion process. We report that such dispersions are stable, bind ibuprofen tightly and yet provide high transdermal drug permeation. Ibuprofen DNLF dispersions prepared according to the present study provide up to five times greater flux of the pharmacologically active S-ibuprofen isomer through human skin than a commercially available racemic ibuprofen emulsion product. We demonstrate scaling up the twin-screw extrusion method to pilot production for a stable, highly permeating ibuprofen DNLF composition based on excipients approved by the US FDA for use in topical products as a key step towards development of a commercially viable, FDA approvable topical ibuprofen medicine to treat osteoarthritis, which has never before been accomplished.

The influence of cultivation conditions on the immobilized acetic acid bacteria metabolic activity

Brewing is an innovative sector of the food industry. Non-alcoholic beer production increases every year. The largest volumes of non-alcoholic beer are obtained by regular beer dialysis. The beer dialysate formed in production contains ethyl alcohol, which entails the need for its rational use. One of the effective ways to use beer dialysate is food biochemical vinegar production. The purpose of the work is to conduct research for biotechnology development of food vinegar from beer dialysates generation using acetic acid bacteria (AAB) immobilization on bio-carriers of various nature. The objects of research were samples of beer dialysates (BD), concentrated to a volume fraction of ethyl alcohol of 7.5%, Acetobacter aceti AAB, vinegar from BD. To study the changes in metabolic activity of immobilized AAB on a bio-carrier, acetic acid fermentation was performed using Acetobacter aceti cells, immobilized on beech shavings, zeolite, and high-pressure polyethylene. Air was supplied to a reservoir by a microcompressor from below through a finely porous ceramic nozzle, providing uniform air dispersion in cultural fluid. Graphs of the cells number and Acetobacter aceti biomass dependence on cultivation duration, nature of the bio-carrier and the aeration method when obtaining vinegar from beer dialysate are presented. The experimental data of the volatile components composition, organic acids and beer dialysate amino acids and vinegar from it are presented. Electron microscopic research of Acetobacter aceti AAB during beech shavings and zeolite cultivation is presented. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are presented.

Effect of Compound Surfactants Modified Carbonyl Iron on Magnetorheological Fluids

As a fast-responding, intelligent, and controllable fluid material, magnetorheological fluid has drawn considerable attention. However, undesirable sedimentation severely restricts its wide application. To solve this problem, an improved strategy is proposed to prepare the magnetorheological fluid with great sedimentation stability. In this study, we used the compound surfactants to modify carbonyl iron powder and fumed silica as a thixotropic agent. At the same time, the effect of different contents of fumed silica on the rheological properties of MRF was studied. The scanning electron microscope, sedimentation, and rheological tests showed that fumed silica can significantly improve the sedimentation stability of magnetorheological fluids, and compound surfactants can increase its dispersion in magnetorheological fluids. As for the fumed silica (1.85 wt%) MR fluid, the sedimentation ratio is about 92.4% in the testing period of 58 days, indicating more excellent sedimentation stability compared to the commercial MR fluid (87.6%). When the magnetic field strength is beyond 391 kA/m, the shear stress is better than commercial magnetorheological fluid.

Buoyant Jets in Cross-Flows: Review, Developments, and Applications

Significant environmental effects from the use of marine outfall discharges have led to increased efforts by both regulatory bodies and research groups to minimize the negative impacts of discharges on the receiving water bodies. Understanding the characteristics of discharges under conditions representative of marine environments can enhance the management of discharges and mitigate the adverse impacts to marine biota. Thus, special attention should be given to ambient cross-flow effects on the mixing behaviors of jet discharges. A buoyant jet in cross-flow has different practical applications such as film cooling and dilution, and provide a higher mixing capability in comparison with free jets or discharges into stationary environments. The main reason for this is believed to be the existence of various complicated vortical structures including a counter-rotating vortex pair as the jet expands downstream. Although tremendous research efforts have been devoted to buoyant jets issuing into cross-flows over the past five decades, the mixing process of an effluent at the discharge point is not yet well understood because of the highly complex fluid interactions and dispersion patterns involved. Therefore, there is a need for a deeper understanding of buoyant jets in cross-flows in order to obtain better predictive methods and more accurate design guidelines. The main aims of this study were (i) to establish the background behind the subject of buoyant jets in cross-flows including the flow structures resulting from the interaction of jets and cross-flows and the impacts of current on mixing and transport behavior; (ii) to present a summary of relevant experimental and numerical research efforts; and finally, (iii) to identify and discuss research gaps and future research directions.

Emulation of Multi-Rotor Functionalities in Fixed Wing Airplane for Farm Based Land Surveillance with Controlled Fluid Dispersion System

The World is emerging with Technologies in every discipline, and India plays a vital role in the export of agricultural products. Since it has a huge amount of manifestation, it requires a lot of manpower. The Lack of skilled labour can also cause depletion of crops production rate. So the use of Technologies in agriculture reduces manpower drastically and increases efficiency. The production rate of crops in agriculture is based on various parameters like temperature, humidity, rain, etc., which are natural factors and are not controlled by farmers. The field of agriculture also depends on some factors like pests, disease, fertilizers, etc., which can be controlled by giving proper treatment to crops. Even though the use of pesticides can protect the crop, it may also have harmful effects on human health. So usage of technologies like quadcopter is an efficient process. But as it involves a huge amount of Initial and Operational cost, the quadcopters are replaced with Fixed Wing Drones. This paper depicts about the design and development of Fixed Wing Airplane known as AGRIWING, which combines all the desirable features of a conventional agricultural fixed wing such as mapping of farm, gathering heat signatures, etc., with the added capabilities of the autonomous fluid dispensing system, as in the Drone Spraying System with the advantages of Fixed Wing Airplane including reduced cost, improved flight time, robustness and more.

Rheological properties and sedimentation stability of magnetorheological fluid based on multi-walled carbon nanotubes/cobalt ferrite nanocomposites

In this investigation, nanocomposites of cobalt ferrite (CoFe2O4) nanoparticles grown on multi-walled carbon nanotubes (MWCNTs) were developed by a ultrasonic-assisted co-precipitation technique. The as-prepared MWCNTs/CoFe2O4 nanocomposites were characterized in detail using transmission electron microscope (TEM), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, thermogravimetric analysis (TGA), superconducting quantum interference device (SQUID) magnetometer and nitrogen adsorption and desorption isotherms. The obtained MWCNTs/CoFe2O4 was adopted as the advanced dispersed phase for the fabrication of a uniform magnetorheological (MR) fluid, and its rheological properties and sedimentation stability were comprehensively examined. It had been revealed that the designed MR suspension exhibited typical MR features with increasing viscosity, shear stress, yield stress, storage modulus and loss modulus depending on the applied magnetic fields. It was worthy to note that the sedimentation stability of MR fluid was improved significantly, which was primarily attributed to the special three-dimensional network structure of MWCNTs/CoFe2O4 and the reduced density mismatch between the dispersed phase and carrier fluid.