Low Viscous Fluid Research Articles

Dynamics of bubble rising in extremely high and low viscous fluids

Bubble dynamics is a captivating field of study due to its complexity and wide-ranging applications. The present research focuses on bubble behavior in fluids with very high and low viscosities. Our study also focuses on understanding the effect of gas flow rate and needle diameter on bubble size. This research is essential because of scientific disagreement in this area, and our revisit adds new findings to the problem. We perform experiments in liquids with extreme viscosity differences using needles ranging from 0.84 mm to 1.54 mm and gas flow rates from 5 ml/min to 80 ml/min. In low-viscosity fluid, bubble necking time is constant with the flow rate, and secondary necking leads to daughter bubble formation. In high-viscosity fluid, bubble formation and rising differ, with smaller bubbles sliding over larger ones and merging symmetrically along their axis. The symmetry of contact decides sliding or coalescence. We also noticed that bubbles formed pairs (doublets) when the gas flow rate decreased with increasing needle size. The consecutive bubble diameter in both fluids is explored. The contrasting characteristics in low-viscosity environments (such as deionized water) and high-viscosity environments (like glycerol) highlight their respective monotonic and non-uniform flow behaviors.

Particle Image Velocimetry in a Centrifugal Pump: Influence of Walls on the Flow at Different Axial Positions

Abstract For almost a century, humans have relied on centrifugal pumps for the transport of low-viscous fluids in commercial, agricultural, and industrial activities. Details of the fluid flow in impellers often influence the overall performance of the centrifugal pump and may explain unstable and inefficient operations taking place sometimes. However, most studies in the literature were devoted to understanding the flow in the midaxial position of the impeller, only with a few focusing their analysis on regions closer to solid walls. This paper aims to study the water flow in the vicinity of the front and rear covers (shroud and hub) of a radial impeller to address the influence of these walls on the fluid dynamics. For that, experiments using particle image velocimetry (PIV) were conducted in a transparent pump at three different axial planes, and the PIV images were processed to obtain the average velocity fields and profiles, as well as turbulence levels. Our results suggest that: (i) significant angular deviations are observed when the velocity vectors on the peripheral planes are compared with those on the central plane; (ii) the velocity profiles close to the border are similar to those in the middle, but the magnitudes are lower close to the hub than to the shroud; (iii) the turbulent kinetic energy on the periphery is up to eight times greater than that measured at the center. Our results bring new insights that can help propose mathematical models and improve the design of new impellers. A database and technical drawings of the centrifugal pump are also available in this paper so that other researchers can perform numerical simulations and validate them against experimental data.

Numerical investigation of viscous fingering in a three-dimensional cubical domain

We perform three-dimensional numerical simulations to understand the role of viscous fingering in sweeping a high-viscous fluid (HVF). These fingers form due to the injection of a low-viscous fluid (LVF) into a porous media containing the high-viscous fluid. We find that the sweeping of HVF depends on different parameters such as the injection velocity (U0) of the LVF, ease of diffusion of the fluid (D), and the logarithmic viscosity ratio of HVF and LVF ℜ. The two-phase Darcy's law module of COMSOL Multiphysics is used to simulate different cases with varying parameters. At high values of U0 and ℜ and lower values of D, the fingers grow non-linearly, resulting in earlier tip splitting of the fingers and breakthrough, further leading to poor sweeping of the HVF. In contrast, the fingers evolve uniformly at low values of U0 and ℜ, resulting in an efficient sweeping of the HVF, while a higher diffusion coefficient leads to a smooth flow with fewer fingers. We also estimate the sweep efficiency and conclude that the parameters U0, D, and ℜ be chosen optimally to minimize the non-linear growth of the fingers to achieve an efficient sweeping of the HVF.

Hydraulic fracture development in conglomerate reservoirs simulated using combined finite-discrete element method

Hydraulic fracturing is known to be the most effective stimulation to enhance fractured reservoir permeability by creating hydraulic fractures (HFs). The efficiency of a HF fluid injection largely depends on the pre-existing discontinuities or sources of heterogeneities. These features need to be considered in a HF operation design. Amongst these features, conglomerate reservoirs containing blocks in a matrix are largely ignored despite their presence in deep rocks. This study focuses on the HF development in such grounds and simulates their hydro-mechanical behaviour by using the combined finite-discrete element method (FDEM), which is fully capable of modelling HF propagation in heterogeneous rocks. First, the capabilities of the FDEM are verified against existing analytical solutions and experimental fluid injection and then employed to model HF development. In the conglomerate models, three blocks with low to high strength properties are simulated to assess the effect of block strength on the HF development pattern. Various controlling parameters, including in-situ stresses, flow rate, fluid kinematic viscosity, directional HF (DHF), properties of the interface between the blocks and matrix, and their effects on the HF path are investigated. The results show a significant influence of blocks in a matrix on the HF pattern. The HF interaction with the blocks of different shapes and dimensions is shown to be complex, and six interaction types for the blocks are identified based on the close observation of the results. It is also found that to achieve a successful HF injection in such grounds, a low flow rate with a low viscous fluid can be a good strategy. Also, it is shown that the blocks' strength significantly affects the type of failure (tensile or shear) and the breakdown pressure.

Analysis of cuttings concentration experimental data using exploratory data analysis

Cuttings transportation is a complex phenomenon involving many inter-acting variables. Experimental investigations on cuttings transport are carried out by different research groups for decades and varying findings are reported which points out to the need for a methodical data analysis approach. In the current paper, six experimental datasets (702 observations) are analyzed using exploratory data analysis (EDA) in a two-fold manner – univariate and multivariate analysis. Univariate analysis shows the asymmetry in distribution for each experimental parameter indicating the need for a nonparametric modeling approach. Multivariate analysis shows the interaction of the experimental parameters among themselves and their influence on downhole cuttings concentration (Cc) using 6D scatter plots and correlation coefficients (Kendall's τ). EDA of the current experimental data reveals the following major findings:•Smaller Cc in concentric vertical wells compared to concentric non-vertical wells.•Drilling fluid flow rate is a dominant operational parameter in vertical wellbore cleaning while string rotation (RPM) is dominant in non-vertical wellbore cleaning.•Little impact of RPM in concentric vertical well and negative eccentric deviated/highly deviated well cleaning. However, RPM together with drilling fluid flow rate provides better cleaning of non-vertical wells with positive eccentricity.•RPM has higher influence on cuttings transport in narrow annulus compared to that in wide annulus.•Assuming drilling fluid of sufficient viscosity and drill string rotation present, low viscous fluid under turbulent flow and high viscous fluid under laminar flow provide better hole cleaning. Further, Kendall's τ indicates apparent viscosity playing a more significant role in cleaning deviated wellbores compared to other inclinations for the current dataset.•Drilling fluid flow rate influences the transport of heavier cuttings and larger cuttings more while RPM has higher influence on the transport of lighter cuttings and smaller cuttings.•Better hole cleaning by heavier drilling fluids than that by lighter fluids.

Experimental investigations and 3D simulations by the overset grid method on twin-screw machines in both pump and turbine mode

Twin-screw pumps due to their particular capabilities, offer u nique b enefits in comparison to other types of pumps. They can also recover wasted energy from the fluid system when run in a reversed way, i.e., in turbine mode. In this study, the possibility of benefiting twin-screw machines instead of conventional control valves in order to recover energy is investigated. Flow physics and energy recovery are analyzed experimentally and by 3D flow simulations in both, pump and turbine mode. Pump and turbine characteristics under different operating points are experimentally measured for low and high viscous fluids, i.e., water and oil, respectively. It is observed that for higher viscosity the dependency of volume flow rate on the pressure difference imposed on the pump is reduced. This observation indicates the significant effect of viscosity on the gap flow. Based on a simulation method by means of overset grid technique, unsteady 3D flow simulations with a high grid quality and a high spatial resolution particularly in gap regions in terms of y + < 1 are conducted and results are validated against experiments. The profound assessment of gap flow based on the simulation results shows that for highly viscous fluids such a soil, the rotational speed of spindles as well as the direction of rotation have a significant effect on gap flow characteristics and consequently on the pump and turbine performance. From the experiments, it is clarified that with a lower rotational speed of spindles and a higher pressure difference, a higher amount of energy up to about 50% of the fluid energy in the piping system can be recovered instead of being dissipated by a conventional control valve.

Dynamic wetting characteristics during droplet formation in a microfluidic T-junction

• Dynamic wetting characteristics during droplet formation in a microfluidic T-junction are investigated. • The three-phase contact line dynamics are influenced by the channel wettability and other flow properties. • The dynamic contact angle increases with an increase in Capillary number, static contact angle, and dispersed phase viscosity. • In contrast it decreases with an increase in flow rate ratio and slip length. Droplet formation in a microfluidic T-junction is dominated by the interfacial force arising between the two fluids. The three-phase contact line at the channel wall is affected by the surface energy or the wettability of the channel wall and other hydrodynamic forces. The dynamics of a three-phase contact line can be evaluated in terms of dynamic contact angle, which a moving contact line makes with a wall. The present work investigates the influence of wall hydrophobicity and fluid properties on the three-phase contact angle during droplet formation in a microfluidic T-junction. Experimental and numerical investigations are performed to study the effects of flow properties on the dynamic wetting of the channel during the droplet formation process. A level-set-based numerical model is employed to predict the moving contact line for different operating parameters and wettabilities of channel walls. Further, a simplified analytical model is developed to express the influence of flow parameters on the dynamic wetting behavior of the wall. The interface is more stressed out for a low viscous dispersed fluid, whereas the interface is less affected by a high viscous dispersed phase fluid. During the transient droplet stage, the dynamic contact angle increases with time with the increase in channel wall hydrophobicity. The dynamic contact angle increases with time for a higher static contact angle, and the variation decreases at a lower static contact angle. At the steady-state, the dynamic contact angle increases with the static contact angle and dispersed phase viscosity. In contrast, it decreases with an increase in the flow rate ratio and the slip length. The droplet with a higher length tends to increase the wetting line in the channel wall. The wettability of the channel wall influences the droplet interface along the lateral direction resulting in corner leakage flow, which further affects the dynamic contact angle.

Parallelization of Microfluidic Droplet Junctions for Ultraviscous Fluids.

The parallelization of multiple microfluidic droplet junctions has been successfully achieved so that the production throughput of the uniform microemulsions/particles has witnessed considerable progress. However, these advancements have been observed only in the case of a low viscous fluid (viscosity of 10-2 -10-3 Pa s). This study designs and fabricates a microfluidic device, enabling a uniform micro-emulsification of an ultraviscous fluid (viscosity of 3.5 Pa s) with a throughput of ≈330 000 droplets per hour. Multiple T-junctions of a dispersed oil phase, split from a single inlet, are connected into the single post-crossflow channel of a continuous water phase. In the proposed device, the continuous water phase undergoes a series circuit, wherein the resistances are continuously accumulated. The independent corrugations of the dispersed oil phase channel, under the theoretical guidance, compromise such increased resistances; the ratio of water to oil flow rates at each junction becomes consistent across T-junctions. Owing to the design being based on a fully 2D interconnection, single-step soft lithography is sufficient for developing the full device. This easy-to-craft architecture contrasts with the previous approach, wherein complicated 3D interconnections of the multiple junctions are involved, thereby facilitating the rapid uptake of high throughput droplet microfluidics for experts and newcomers alike.

Contamination and carryover free handling of complex fluids using lubricant-infused pipette tips

Cross-contamination of biological samples during handling and preparation, is a major issue in laboratory setups, leading to false-positives or false-negatives. Sample carryover residue in pipette tips contributes greatly to this issue. Most pipette tips on the market are manufactured with hydrophobic polymers that are able to repel high surface tension liquids, yet they lack in performance when low surface tension liquids and viscous fluids are involved. Moreover, hydrophobicity of pipette tips can result in hydrophobic adsorption of biomolecules, causing inaccuracies and loss in precision during pipetting. Here we propose the use of lubricant-infused surface (LIS) technology to achieve omniphobic properties in pipette tips. Using a versatile and simple design, the inner lumen of commercially available pipette tips was coated with a fluorosilane (FS) layer using chemical vapor deposition (CVD). The presence of FS groups on the tips is confirmed by x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) tests. After lubrication of the tips through a fluorinated lubricant, the omniphobicity and repellent behaviour of the tips drastically enhanced which are revealed via static and hysteresis contact angle measurements. The repellency of the lubricant-infused pipette tips against physical adsorption is investigated through pipetting a food coloring dye as well as human blood samples and are compared to the untreated tips. The results show significantly less amount carryover residue when the lubricant-infused tips are utilized compared to commercially available ones. We also demonstrate the lubricant-infused tips reduce bacteria contamination of the inner lumen by 3 to 6-log (over 99%, depending on the tip size) after pipetting up and down the bacteria solution.

Anti-icing fluid performance on substrates with different thermal conductivity and roughness

The performance of aircraft anti-icing fluids reduces unusually on aviation composites. It is unclear whether this is due to low substrate thermal conductivity or hydrophobicity. Therefore, we considered experimentally the performance of Newtonian and non-Newtonian aircraft anti-icing fluids on substrates with thermal conductivities from 0.17 to 252 W/m∙K. It was found that the decrease of substrate thermal conductivity promotes the freezing of Newtonian and low viscous Non-Newtonian fluids compared to the thicker Non-Newtonian one. The thermal conductivity effect can be explained by the competition of two heat transfer processes: heat accumulation and the transfer of latent heat. Thus, Newtonian and low viscous Non-Newtonian aircraft anti-icing fluids must be defined on aviation composites together with substrate thermal conductivity, wettability, and roughness.

A study on monoterpenoid-based natural deep eutectic solvents

Herein, the synthesis and characterization methods of natural deep eutectic solvents based on monoterpenoids have been presented. Low viscous fluids with suitable physicochemical properties are produced. The materials are non-toxic, biodegradable, and cost-effective. Thus, they can be used to develop sustainable solvents for various processes and can find their applications in various fields. A theoretical study based on quantum chemistry and classical molecular dynamics is used for the nanoscopic characterization of structure, dynamics, and hydrogen bonding. The reported results help analyze the properties of this new family of solvents. The required information for developing structure–property relationships for proper solvent design to form a sustainable chemistry framework is obtained.

Experimental investigation and correlations for proppant distribution in narrow fractures of deep shale gas reservoirs

Hydraulic fracturing is a crucial stimulation for the development of deep shale gas reservoirs. A key challenge to the effectiveness of hydraulic fracturing is to place small proppants in complex narrow fractures reasonably. The experiments with varied particle and fluid parameters are carried out in a narrow planar channel to understand particle transport and distribution. The four dimensionless parameters, including the Reynold number, Shields number, density ratio, and particle volume fraction, are introduced to describe the particle transport in narrow fractures. The results indicate that the narrow channel probably induces fluid fingers and small particle aggregation in a highly viscous fluid, leading to particle settlement near the entrance. The low viscous fluid is beneficial to disperse particles further into the fracture, especially in the high-speed fluid velocity. The linear and natural logarithmic laws have relationships with dimensionless parameters accurately. The multiple linear regression method developed two correlation models with four dimensionless parameters to predict the bed equilibrium height and covered area of small particles in narrow fractures. The study provides fundamental insight into understanding small size proppant distribution in deep reservoirs.

Effect of anisotropies in formation of viscous fingering in lifting plate Hele-Shaw cell

ABSTRACT This study presents an experimental investigation of viscous fingering formation under anisotropies in Hele-Shaw cell. The lifting plate Hele-Shaw cell employed in this study comprises of two parallel plates firmly positioned one over another with a minuscule gap filled with high viscous fluid, and a low viscous fluid flows through this gap. Two fluids of different viscosity interact in this cell and instabilities are generated due to the viscosity difference. These instabilities need to be suppressed to get controlled and stabilised patterns. Literatures presented these instabilities and explored the various techniques to stabilise them. In this study, a novel strategy consists of use of anisotropy and protrusion on the lower plate of the cell to suppress instabilities is presented. The holes and protrusions explicitly generate the least resistance to the flow of low viscous fluid (air). This results in control flow and guided path for low viscous fluid (air) penetrating into a high viscous fluid. These methods have given excellent control over the instabilities, and beautifully controlled naturally inspired patterns are obtained. Microfractals present in nature, such as leaf venation, honeycomb pattern, are examined and imitated by the proposed method. Experimental results confirm the acceptability of this control strategy.

Development of New Element for Mixing of High and Low Viscous Fluids

Development of New Element for Mixing of High and Low Viscous Fluids

FEATURES OF PROPAGATION OF HYDRAULIC FRACTURES IN STRATIFIED ROCK MASS

In hydraulic fracturing commonly used in mining, it is important to determine the shapes and sizes of created fractures. The governing factor in this case is the structure of rock mass which is often stratified. This study analyzes the influence of strengths of the layers and their stress states on the shapes of the growing fractures. Numerical modeling shows that in hydraulic fracturing with low-viscous fluids, fractures grow mostly in a layer having lower tension or compression strengths. The calculations carried out for the analyzed cases provide the values of tension strength and external compression for hydraulic fractures to grow only in one layer. It is shown that the increase in the breakdown fluid viscosity weakens this effect.

On a Study of Flow Past Non-Newtonian Fluid Bubbles

In the current work, we aim at finding an analytical solution to the problem of fluid flow past a pair of separated non-Newtonian fluid bubbles. These bubbles are assumed to be spherical and non-permeable with the non-Newtonian fluid, viz. the couple stress fluid filling their interior. Further, the bubbles are presumed to be static in the flow domain, where a Newtonian fluid streams past these bubbles with a constant velocity (U) along the negative x-direction. We developed a mathematical model in the bipolar coordinate system for the fluid flow outside the bubbles and the spherical coordinate system inside the bubbles to derive a separable solution for their respective governing equations. Furthermore, to evaluate the model's applicabilities on the industrial front, the data on some widely used industrial fluids are given as inputs to the model, such as density, the viscosity of air or water for the fluid flow model developed for the region outside the fluid bubbles and the data on Cyclopentane or DIDP (non-Newtonian) for that within the bubbles. Some interesting findings are: the pressure in the outer region of the bubbles is higher when filled with low viscous industrial fluid, Cyclopentane, than a high viscous fluid, DIDP. Furthermore, an increase in the viscosity of Cyclopentane did not alter the pressure distribution in the region outside the bubbles. However, there is a considerable effect on this pressure in the case of DIDP bubbles.

Influence of Blade Number on Performance and Internal Flow Condition of Centrifugal Pump for Low Viscous Fluid Food

There are many kinds of the fluid food transportation pumps depending on the characteristics of the fluid, i.e. a sanitary pump made from stainless steel, a screw pump and so on. A centrifugal pump was adopted as a fluid food pump in this research because it makes the stable continuous transportation of fluid food and the structure of the pump is simple compared to positive displacement pumps. The purpose of this research is to investigate the influence of the blade number on the pump performance and internal flow to enrich the pump design data for low viscous fluid food. The centrifugal pump with an open impeller was used and six impellers having the different blade number were prepared. Performance test using an experimental apparatus was conducted and the numerical analysis was also carried out. In the numerical analysis, the commercial software ANSYS-CFX16.2 was used. The head, shaft power and efficiency obtained by the numerical analysis, are almost the same with the experimental results. The head and shaft power increase with the increase of the blade number. The shear rate, which is concerned to fluid food quality, is high near the inlet region of the blade-to-blade passage for all types of blades. The shear rate of each type of the blade is discussed based on the numerical analysis results and relations between the blade number and shear rate are clarified.

Oil-Based Drilling Fluid's Cuttings Bed Removal Properties for Deviated Wellbores

Abstract Results from cuttings transport tests in the laboratory using different field-applied oil-based drilling fluids with similar weight and varying viscosities are presented in this paper. The fluids are designed for highly deviated wells, and the cuttings transport performance at relevant wellbore inclinations was investigated. The experiments have been performed in a flow loop that consists of a 10-m-long test section with 50.4 mm (2″) diameter freely rotating steel drill string inside a 100-mm (≈4″) diameter wellbore made of cement. Sand particles were injected while circulating the drilling fluid through the test section. Experiments were performed at three wellbore inclinations: 48, 60, and 90 deg from vertical. The applied flow loop dimensions are designed so that the results are scalable to field applications; especially for the 12 ¼″and 8 ½″ sections. The selected setup provides correct shear rate ranges and similar Reynolds numbers to the field application when the same fluids are applied. Results show that hole cleaning abilities of the tested fluids vary significantly with well angle, drill string rotation, and flowrate. Results support field experience showing that low viscous fluids are more efficient than viscous fluids at higher flowrates and low drill string rotation. As well as per field experience, more viscous fluids are efficient in combination with high drill string rotation rates. The results show the effect of cuttings transport efficiency as a function of hydraulic frictional pressure drop, demonstrating methods to achieve a more optimal hydraulic design in the tested conditions. The key findings have direct relevance to drilling operations.

Flow Field Analysis and Feasibility Study of a Multistage Centrifugal Pump Designed for Low-Viscous Fluids

A multistage centrifugal pump is designed for pumping low-viscosity, highly volatile and flammable chemicals, including hydrocarbons, for high head requirements. The five-stage centrifugal pump consists of a double-suction impeller at the first stage followed by a twin volute. The impellers for stages two through five are single-suction impellers followed by diffuser vanes and return channel vanes. The analytical performance is calculated initially in the design stage by applying similarity laws to an existing scaled-down pump model designed for low flow rate applications. The proposed pump design is investigated using computational fluid dynamics tools to study its performance in design and off-design conditions for water as the base fluid. The design feasibility of the centrifugal pump is tested for other fluids, such as water at a high temperature and pressure, diesel and debutanized diesel. The pump design is found to be suitable for a variety of fluids and operating ranges. The losses in the pump are analyzed in each stage at the best efficiency point. The losses in efficiency and head are observed to be higher in the second stage than in other stages. The detailed flow behavior at the second stage is studied to identify the root cause of the losses. Design modifications are recommended to diminish the losses and improve the overall performance of the pump.

Enhanced mass transfer in air oscillating in a channel with periodically varying radius

The effect of high frequency oscillations of air column in a channel of variable radius on vapor diffusion is experimentally studied. It is found that significant enhancement of longitudinal mass transfer takes place due to steady vortical flows excited in channel cells. In parallel with experiments in air we conducted PIV experiments with low viscous fluids in order to study the steady flow structure in the same range of dimensionless frequency as in diffusion experiments with air. It is revealed that additional mass transfer Ds associated with the steady flow is a function of steady flow dimensionless velocity V, which depends on frequency ω and pulsating Reynolds number. It is followed from PIV measurements that Ds ∼ V2 and in the studied range of oscillation frequency ω, the additional diffusion rate Ds is an order larger than the molecular diffusion D. Comparison of our experimental data with data of other authors obtained in the experiments with channels of another geometry shows that increase of variation of a channel radius results in significant enhancement of steady flow velocity and, therefore, mass transfer.