Viscosity Force Research Articles

Influence of Material Properties on Spheroidisation of Gas Atomization Process

For many contemporary powdermetallurgical applications, spherical powders are preferred. Spherical particles have a lower oxygen content, a better flowability and their behaviour is - compared to irregular particles - better predictable. The powder production process via melt atomization can be divided into the steps a. primary breakup into ligaments, b. ligament breakup and c. secondary breakup and/or spheroidisation, while simultaneously cooling and freezing take place. Apart from thermodynamic conditions during the process, melt properties such as viscosity, density, surface tension, heat capacity and thermal conductivity will influence the processes around spheroidisation. As a first step, a 4-force model (viscosity, surface tension, external dynamic and inertia forces) is applied on the melt droplet to predict the influence of the melt properties on spheroidisation separately. Secondly, the spheroidisation process is calculated for different materials such as Copper, Iron or Titanium for existing atomisation systems. Finally, suggestions are presented which may help to produce more spherical particles.

Air Assisted Atomization Characterization of Biodegradable Fluid Using Microlubrication Technique

In microlubrication, effective spray cooling is generally dependent on the atomization process. Air assisted atomizer is commonly used in many industrial applications because even at low-pressure fuel or coolant supply, it can create a fine spray formation. Viscosity force resists the deformation of liquid ligaments into a droplet. This increase in viscosity creates a bigger droplet size. If the density of the coolant is more, it will resist the acceleration and results in a bigger droplet. Properties of coolant such as viscosity, density, and surface tension are important and will affect the droplet size. Hence, for effective microlubrication, the performance study of atomization is important. In this paper, computational fluid dynamics (CFD) is used to study atomization characteristics of biodegradable coolant castor oil and AccuLube-2000 at flow rate 150 ml/hr to 60 ml/hr. This paper focuses on the effect of coolant properties like viscosity and density on the droplet size and discrete phase model concentration. In this work, the CFD atomization is studied using a discrete phase model and a Realizable k-ϵ turbulent flow model. Numerical simulation shows that the droplet size of the castor oil is more than AccuLube-2000. Also, for a higher flow rate, the area near the nozzle had a very uneven concentration of sprayed particles. However, the concentration was more even as the spray went farther away from the nozzle.

3D dynamic motion of a dielectric micro-sphere within optical tweezers

Known as laser trapping, optical tweezers, with nanometer accuracy and pico-newton precision, plays a pivotal role in single bio-molecule measurements and controllable motions of micro-machines. In order to advance the flourishing applications for those achievements, it is necessary to make clear the three-dimensional dynamic process of micro-particles stepping into an optical field. In this paper, we utilize the ray optics method to calculate the optical force and optical torque of a micro-sphere in optical tweezers. With the influence of viscosity force and torque taken into account, we numerically solve and analyze the dynamic process of a dielectric micro-sphere in optical tweezers on the basis of Newton mechanical equations under various conditions of initial positions and velocity vectors of the particle. The particle trajectory over time can demonstrate whether the particle can be successfully trapped into the optical tweezers center and reveal the subtle details of this trapping process. Even in a simple pair of optical tweezers, the dielectric micro-sphere exhibits abundant phases of mechanical motions including acceleration, deceleration, and turning. These studies will be of great help to understand the particle-laser trap interaction in various situations and promote exciting possibilities for exploring novel ways to control the mechanical dynamics of microscale particles.

Structural characterization and developability assessment of sustained release hydrogels for rapid implementation during preclinical studies

Sustained-release formulations are important tools to convert efficacious molecules into therapeutic products. Hydrogels enable the rapid assessment of sustained-release strategies, which are important during preclinical development where drug quantities are limited and fast turnaround times are the norm. Most research in hydrogel-based drug delivery has focused around synthesizing new materials and polymers, with limited focus on structural characterization, technology developability and implementation. Two commercially available thermosensitive hydrogel systems, comprised of block copolymers of poly(lactic-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) (PLGA) and poly(lactide-co-caprolactone)-b-poly(ethyleneglycol)-b-poly(lactide-co-caprolactone) (PLCL), were evaluated during this study. The two block copolymers described in the study were successfully formulated to form hydrogels which delayed the release of lysozyme (> 20 days) in vitro. Characterization of formulation attributes of the hydrogels like Tsol-gel temperature, complex viscosity and injection force showed that these systems are amenable to rapid implementation in preclinical studies. Understanding the structure of the gel network is critical to determine the factors controlling the release of therapeutics out of these gels. The structures were characterized via the gel mesh sizes, which were estimated using two orthogonal techniques: small angle X-ray scattering (SAXS) and rheology. The mesh sizes of these hydrogels were larger than the hydrodynamic radius (size) of lysozyme (drug), indicating that release through these gels is expected to be diffusive at all time scales rather than sub-diffusive. In vitro drug release experiments confirm that diffusion is the dominating mechanism for lysozyme release; with no contribution from degradation, erosion, relaxation, swelling of the polymer network or drug-polymer interactions. PLGA hydrogel was found to have a much higher complex viscosity than PLCL hydrogel, which correlates with the slower diffusivity and release of lysozyme seen from the PLGA hydrogel as compared to PLCL hydrogel. This is due to the increased frictional drag experienced by the lysozyme molecule in the PLGA hydrogel network, as described by the hydrodynamic theory.

Determination of the residence-time distribution in industrial dryer for the production of recycled polyester

The study proposes the evaluation of the residence-time distribution (RTD) in situ in an industrial dryer for the production of recycled polyester fibers (PES) from colorless polyethylene terephthalate (PET) flakes without interruption of the production. A disturbance of the pulse type was employed, in which the tracer (blue PET flakes) had previously been crystalized and its concentration was obtained according to the time at the dryer outlet. Additionally, analyses of intrinsic viscosity and crystallization percentage of the PET flakes (colorless and blue) and PES intrinsic viscosity and color force were performed. By RTD, the mean residence time (322.8 min), the variance (1305.4 min2), the standard deviation (36.1 min) and the relative error (1.5%) were obtained when compared to the theoretical residence time, indicating the absence of preferred paths or flake agglomerates in the equipment. Finally, the characterization demonstrated that there was no alteration in the parameters of product quality during RTD evaluation, confirming the potential of application of this methodology for diagnoses of continuous industrial processes.

Optimisation of Artificial Lifts Using Prosper Nodal Analysis for BARBRA-1 Well in Niger Delta

Hydrocarbon exploration basically requires effective drilling and efficient overpowering of frictional and viscosity forces. Normally, frictional power losses occur in deep well systems and it is essential to analyse each component of any well system to determine where exactly pressure is lost, and this can be done using Nodal Analysis. In this study, nodal analysis has been carried out with the use of PROSPER, a software for well performance, design and optimisation. Artificial lifts can then be used to solve the problem of frictional power losses. To increase the production of Barbra 1 well in the Niger Delta and hence extend its functional life, we have applied nodal analysis. Modelling results for three artificial lift methods; continuous gas lift, intermittent gas lift and electrical submersible pump were found to be 1734.93 bbl/day, 451.50 bbl/day and 2869 bbl/day respectively. The output from the well performance without artificial lift was 1370.99 bbl/day by applying Darcy’s model. Meanwhile, the output from the well without artificial lift is 89.90 bbl/day when aided with productivity index (PI) entry, the normal model for intermittent gas lift. Hence, from the comparative analysis of the results obtained from this study, it was deduced that when artificial lifts are employed, the well output increases significantly from 1370.99bbl/day to 2869 bbl/day (electrical submersible pump). This study concludes that wells such as Barbra 1 are good candidates for artificial lift, and this is evidenced by increasing productivity.
 Keywords: Production optimisation, nodal analysis, prosper simulator and barbra well.

Weakly nonlinear theory and numerics on pressure wave propagation in a flowing water containing many translational bubbles acting a drag force

Focusing on the effect of translational motion of bubbles and drag force acting bubbles, we theotetically and numerically tackle weakly nonlinear propagation of plane progressive pressure waves in a compressible water flow uniformly containing a number of spherical gas bubbles. At an initial state, gas and liquid phases are flowing with each velocity. Drag force and virtual mass force are introduced in an interfacial transport across the bubble–liquid interface. As bubble dynamics, translation and spherically symmetric oscillation are considered. The bubbles do not coalesce, break up, disappear, and appear. The gas viscosity, the thermal conductivities of the gas and liquid are discarded. From the singular perturbation analysis up to the second order of approximation, we have two types of Korteweg–de Vries–Burgers (KdVB) equation with a newly introduced term without a differentiation due to the drag force from the basic equations for bubbly flows in a two-fluid model; the drag term is classified into the linear and nonlinear terms. The translation affects the nonlinear effect of waves and the drag force affects the dissipation effect of waves. We finally numerically solve the KdVB equation to compare three dissipation factors, i.e., acoustic radiation damping due to the liquid compressibility, liquid viscosity, and drag force for various initial void fraction and bubble radius.

A Nonlinear Model for Online Identifying a High-Speed Bidirectional DC Motor

The modeling system is a process to define the real physical system mathematically, and the input/output data are responsible for configuring the relation between them as a mathematical model. Most of the actual systems have nonlinear performance, and this nonlinear behavior is the inherent feature for those systems; Mechatronic systems are not an exception. Transforming the electrical energy to mechanical one or vice versa has not been done entirely. There are usually losses as heat, or due to reverse mechanical, electrical, or magnetic energy, takes irregular shapes, and they are concerned as the significant resource of that nonlinear behavior. The article introduces a nonlinear online Identification of a high-speed bidirectional DC motor with dead zone and Coulomb friction effect, which represent a primary nonlinear source, as well as viscosity forces. The Wiener block-oriented nonlinear system with neural networks are implemented to identify the nonlinear dynamic, mechatronic system. Online identification is adopted using the recursive weighted least squares(RWLS) method, which depends on the current and (to some extent) previous data. The identification fitness is found for various configurations with different polynomial orders, and the best model fitness is obtained about 98% according to normalized root mean square criterion for a third order polynomial.

Modeling of early stage droplet spreading based on numerical simulations

The initial spreading dynamics of a droplet has been studied for decades, however, the mechanism of such phenomenon is still not well known and an efficient prediction model considering combined effects of each influence factor for this process is absent. In present study, numerical simulations for the early stage droplet spreading are carried out based on a modified MPS method with up-to-date viscosity model, pressure Poisson equation, pressure gradient model as well as improved boundary conditions. Influences of the contact angle, viscosity and surface tension force are individually investigated, and their effects are properly characterized by dimensionless contact angle Θ, Reynolds number Re and Bound number Bo. Results show that the droplet spreading radius can be modeled as r/R0 = β(t*)α, where α and β are functions of dimensionless numbers above. Parameters α and β of the contact radius’ power-law growth in all simulations are adopted as inputs to determine coefficients in droplet spreading correlation. The proposed correlation generates pretty close predicted results whose relative errors are less than 5% comparing with experimental values.Present research provides a picture on how the initial contact between the liquid drop and solid surface develops, and it could be a fundamental research for more complicated droplet behaviors e.g. the droplet impact and collision.

Abstract 4604: Can breast cancer cells be distinguished from blood cells by mechanical parameters? A label-free CTC detection approach

Abstract Background: Even years after successful treatment of the primary tumor about one third of breast cancer patients are suffering from metastatic relapse. A possible reason might be hematogenous spread. Therefore circulating tumor cells (CTCs) in the blood might be interesting and easy accessible surrogate markers for disease monitoring. Usually, detection methods are based on cellular parameters like cell surface markers, size, density or flexibility. Due to phenotypical, mechanical and functional changes during cancer progression and treatment response, isolation of CTC subpopulations remains very challenging. Here we focused on the characterization of CTC mechanics to evaluate the utility of mechanical parameters for CTC separation from blood. Methods: For the first time, we investigated the active and passive mechanical CTC properties such as elasticity, viscosity and contractile force exertion. In an optical rheometer, cells are deformed non-invasively by a dual beam trap. Thus, the relative deformation of a single cell can be measured while phase contrast and fluorescent images are taken. For proof of premise we used peripheral blood mononuclear cells (PBMC) isolated from a healthy donor and human GFP-expressing MDA-MB 231 breast cancer cells to mimic a CTC model system and to measure cell type specific mechanical deformation profiles. For translational experiments blood samples were collected from breast cancer patients. Hematopoietic cells were depleted using CD45. The cell suspensions were applied to the optical stretcher and rheological parameters were measured in the same manner. Phase contrast images of potentially interesting cells were analyzed manually to eliminate dead cells and to identify possible CTC candidates. Results: We were able to reveal distinct mechanical profiles from hematopoietic cells and breast cancer cells, respectively. The optical deformability at the end of the step stress creep experiment (EOS) was significantly different in both, the model and the translational, systems comparing healthy PPMC to MDA-MB 231 cells respective possible CTC from breast cancer patients. Evaluation of secondary parameters like viscosity and activity using a machine learning algorithm allowed for a clear distinction between hematopoietic and cancer cells in the model system. Preliminary results of the translational system suggest that identification of CTC candidates exclusively based on mechanical parameters might be possible. Conclusion: Together with morphology and cell size, the cellular deformation pattern might be a proper tool for marker-free CTC detection in the peripheral blood of breast cancer patients. The optical stretcher device is not suitable for high throughput CTC measurement. However, it allows recommendations for pore size or flow rates which play an important role in the development of label-free isolation approaches including filtration by size or separation by cellular compressibility. Citation Format: Ivonne Nel, Erik W. Morawetz, Josef A. Kaes, Bahriye Aktas. Can breast cancer cells be distinguished from blood cells by mechanical parameters? A label-free CTC detection approach [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4604.

Extended release pellets prepared by hot melt extrusion technique for abuse deterrent potential: Category-1 in-vitro evaluation.

The objective of the present study was to develop extended-release (ER) hot-melt extruded (HME) abuse-deterrent pellets of acetaminophen, a model drug, by utilizing high molecular weight polyethylene oxide (PEO) and gelling agents (xanthan gum, guar gum, and gellan gum). The HME pellets were evaluated for their abuse-deterrence (AD) potential by Category-1 laboratory in-vitro evaluation parameters, including particle size reduction (PSR), small volume extraction, dissolution, viscosity, syringeability, and injectability. Further, the pellets were investigated for resistance to physical (crushing) and thermal (oven and microwave) manipulation to evaluate the strength of the AD properties. Physical manipulation studies demonstrated that the pellets were intact, extremely hard, and resistant to PSR and manipulation to bypass ER properties. Dissolution of all intact and physically manipulated pellets led to complete drug release within 8h, and resistance to dose-dumping in 40% ethanol was observed. The drug extraction was <50% in 10mL of ingestible and non-ingestible solvents under static, agitation, and thermal manipulation conditions with an incubation time of 30min. The PEO/xanthan gum-based formulation showed higher viscosity, syringe and injection forces, and lower syringeable volume in all manipulation conditions compared with plain PEO pellets. These findings supported the AD potential of PEO and xanthan gum pellets against intravenous abuse.

Continuous Enrichment and Separation of Nanoparticles via Acoustic Streaming.

Enrichment and separation of Micro/Nano-scale specimens are fundamental requirements in biomedical researches. In this paper, we demonstrated a simple and efficient microfluidic chip for the continuous enrichment and separation of nanoscale polystyrene particles using the acoustic streaming induced by gigahertz(GHz) bulk acoustic waves(BAW). The bulk acoustic resonator released ultrahigh frequency (2GHz) acoustic waves into the fluid and triggered the acoustic streaming. The nanoparticles were continuous concentrated and segregated by the combination action of the viscosity force and the acoustic radiation force. The separation of 300 and 100 nm particles was achieved with the high purity (92.4%). These data contribute proof-in-principle that acoustic streaming is a label-free strategy that can be used to enrich and separate nanoscale specimens with high efficiency.

Formation and internal microstructure of granules from wetting and non-wetting efavirenz/iron oxide blends

An examination of granulation of non-wetting/wetting powder mixtures is presented. Non-wetting micron-size pharmaceutical active powder was blended with a sub-micron wetting excipient in three different ratios to produce wetting, non-wetting, and marginally-wetting powder blends. Model nuclei were prepared from these blends using binder droplets with viscosity of ca 10, 100 and 1000 mPa·s and further granulated in tumbling drum and high shear granulator. The effects of blend wettability, binder viscosity, granulation time, and shear forces on granule size and microstructure were investigated. Hollow granules were produced at higher binder viscosity of 100 and 1000 mPa·s regardless of blend wettability. Solid granules with a complex internal microstructure were produced at low binder viscosity of 10 mPa·s regardless of blend wettability. Contribution of capillary, viscous and impact forces are considered to explain differences in granule microstructure. Modified Reynolds and Weber numbers are proposed to rationalize formation and stability of shell microstructures.

Application of lattice Boltzmann method for studying interaction dynamics of parallel plane minijets

In this work, the method of lattice Boltzmann equations was applied to simulate the systems of two and three parallel laminar plane jets. Simulation was carried out for different Reynolds numbers (Re = 20-200). For the case of two jets, the character of jet interaction has been determined to be, in general, non-stationary, but for small Re values, the process becomes stable due to the action of viscosity forces. For the case of three jets, the character of jets interaction is found to differ significantly from the case of two jets and is non-stationary even for small Re numbers.

Scaling law of contact time for particles settling in a quiescent fluid

Numerical simulations are conducted for the gravity–driven settling of two particles in a viscous quiescent fluid. A method is proposed to determine the scaling law of inter–particle contact time. The method is simple and general. The resulting scaling law explains the observations of literature and predicts the influences of particle–fluid density ratio, fluid viscosity, friction, rolling friction, and adhesion force.

Can tumor cells be distinguished from blood cells by mechanical parameters? A label-free CTC detection approach.

e15526 Background: Even years after successful treatment of the primary tumor about 30% of breast cancer patients are suffering from metastatic relapse. One reason might be hematogenous spread. Therefore circulating tumor cells (CTC) in the blood might be interesting and easy accessible surrogate markers for disease monitoring. Due to phenotypical, mechanical and functional changes during cancer progression and treatment response, isolation of CTC subpopulations remains very challenging. Here we focused on the characterization of CTC mechanics to evaluate the utility of mechanical parameters for CTC separation from blood. Methods: For the first time, we investigated the active and passive mechanical CTC properties such as elasticity, viscosity and contractile force exertion using a dual beam trap. For proof of premise we used peripheral blood mononuclear cells (PBMC) from a healthy donor and human GFP-expressing MDA-MB 231 breast cancer cells to mimic a CTC model system and to measure cell type specific mechanical deformation profiles using an optical rheometer. For translational experiments blood samples were collected from patients with mamma or vulvar carcinoma. Hematopoietic cells were depleted using CD45. The remaining cell suspensions were applied to the optical stretcher and rheological parameters were measured in the same manner. Results: We were able to reveal distinct mechanical profiles from hematopoietic cells and breast cancer cells, respectively. The optical deformability was significantly different in both the model and the translational, systems comparing healthy PPMC to MDA-MB 231 cells, respective possible CTC candidates from breast and vulvar carcinoma patients. Evaluation of secondary parameters like viscosity and activity using a machine learning algorithm allowed for a clear distinction between hematopoietic and cancer cells in the model system. CD45-positive and -negative cells from patients with mamma or vulvar carcinoma (n = 7) showed distinct differences in the rheological behavior of both cell populations. Surprisingly, the mechanical profiles of CD45-negative cells from mamma carcinoma samples were severely different from vulvar carcinoma. Conclusions: Together with morphology and cell size, the cellular deformation pattern might be a proper tool for marker-free CTC detection in the peripheral blood of breast cancer patients.

Prediction model and energy dissipation analysis of Taylor bubble rise velocity in yield stress fluid

In this study, a velocity field model around a Taylor bubble is established after the analysis of the disturbed region around the bubble. The model combines the continuity and yield stress fluid constitutive equations. Based on this velocity field model, an energy dissipation model for the work accomplished by each resistance of bubbles is proposed. In addition, based on an analysis of energy conservation, a new model for predicting the velocity of a Taylor bubble in a yield stress fluid is presented. The experiments of Taylor bubble through Carbopol solution migration in 50 and 60 mm diameter tubes were carried out. Results show that the yield stress has considerable influence on the rise speed of the bubble, improving the anti-disturbance ability of the fluid and further stabilizing the tail of the bubble. Combined with experimental data, the bubble velocity prediction model is verified, and the error value of the calculation result is found to be less than 6%. An energy analysis of the Taylor bubble rising process shows that the volume of the bubble increases, the proportion of work done by inertial force and surface tension decreases, and that done by viscosity force and yield stress increases. The work done by surface tension has little effect on the rise speed of bubbles, which can be ignored. The Taylor bubble velocity changes slightly with the volume, as the bubble volume increases, and the buoyancy work is consumed by the viscous and inertial forces in the film region.

Thin interface limit of the double-sided phase-field model with convection.

The thin interface limit of the phase-field model is extended to include transport via melt convection. A double-sided model (equal diffusivity in liquid and solid phases) is considered for the present analysis. For the coupling between phase-field and Navier-Stokes equations, two commonly used schemes are investigated using a matched asymptotic analysis: (i) variable viscosity and (ii) drag force model. While for the variable viscosity model, the existence of a thin interface limit can be shown up to the second order in the expansion parameter, difficulties arise in satisfying no-slip boundary condition at this order for the drag force model. Nevertheless, detailed numerical simulations in two dimensions show practically no difference in dendritic growth profiles in the presence of forced melt flow obtained for the two coupling schemes. This suggests that both approaches can be used for the purpose of numerical simulations. Simulation results are also compared to analytic theory, showing excellent agreement for weak flow. Deviations at higher fluid velocities are discussed in terms of the underlying theoretical assumptions. This article is part of the theme issue 'Patterns in soft and biological matters'.

Viscous Motion of Spherical Nanoparticles That Scatter Laser Radiation in the Rayleigh Regime

The mechanism of transverse radiation viscosity for nanospheres moving in laser field is analyzed. It is demonstrated that in the process of light scattering by these particles besides the force Fs accelerating them in the direction of radiation propagation and the gradient force Fg that is due to the spatial inhomogeneity of the light field, there are forces Fvisc that slow down the movement of particles in the transverse directions. These light viscosity forces are due to the Doppler shift in frequency of scattered radiation. The general expressions for these forces acting on particles that scatter radiation in the Rayleigh regime are derived and applied to estimate their effect on levitated nanospheres and also on slow electrons moving in the laser and magnetic fields. The possible experiments for observation the effects of light viscosity is discussed.

Analysis of force factors affecting valve fitting process at the saddle

AnnotationThe analysis results of the action of various force factors that slows the hydraulic valve when fitting on the saddle are presented. Manifestations of inertia forces in a thin layer of liquid located in the gap between the valve and the seat immediately before the closing of the gap are shown. The components of inertia forces are distinguished, which differ in the mechanism of occurrence. The degree of their influence on the fitting process in relation to the viscosity forces is shown.