Rheological Characterization of Solids Phase in Biomass Processes of Disc-Stack Centrifuges.

It has been long known that drilling fluid viscoelastic properties have a significant impact on various elements of drilling hydraulics design (e.g., assessment of frictional pressure loss, particle settling velocity, hole cleaning, etc.). However, efforts for considering the viscoelastic fluid properties in drilling hydraulics design are traditionally hindered by the fact that there was no practical methodology to measure these critical fluid properties in the field. Previous studies have highlighted the advantages of using the concept of “energy dissipation” for the quantitative evaluation of fluid elasticity. Energy dissipation theory provides a more comprehensive description of the fluid elasticity by considering the two characteristics of the fluid simultaneously; stretchiness (oscillation strain % at the crossover point of G’ and G” curves) and the stress corresponding to crossover point (i.e., flow point). In a recent study, we have shown that the “energy dissipation” of viscoelastic fluids can be correlated to fluid physical properties such as apparent viscosity and funnel viscosity, which can be conveniently measured using standard field-testing equipment (i.e., Rotational Viscometer and Funnel viscometer). Based on these findings, a new methodology for the field assessment of drilling fluid viscoelasticity has been developed, opening new opportunities to develop improved hydraulics models. In this paper, using the new methodology developed in a recent study, we present a new generalized model for the field assessment of the particle settling velocity in viscoelastic fluids. The main objectives of the study were to: 1) Develop a generalized model for the field assessment of particle settling velocity in shear-thinning viscoelastic fluids by using the energy dissipation concept as an indicator of the fluid viscoelasticity; 2) Investigate the significant factors that influence the particle settling velocity to help provide a solution to the potential problem encountered in field drilling operations. We prepared ten different fluids, which were divided into two groups based on their shear viscosity values. In each group, five fluids were having similar shear viscosity and variable elasticity values. Nineteen different spherical particles were used to conduct particle settling experiments with a density range from 2700 kg/m3 to 6000kg/m3 and a diameter range from 1mm to 4mm. Rheological characterizations of the fluids have been conducted by using funnel viscometer, API Rotational viscometer, controlled shear rate, and amplitude sweep test measurements. Based on the experimental results and theory of the particle settling in non-Newtonian fluids, we developed a new model that can be used for predicting particle settling velocity in viscoelastic fluids. The statistical analyses had shown that the root means square error and mean absolute percentage error of model predictions were 0.0032 m/s and 4.1 percent, respectively.

Chapter 3 Surface Interaction between the Soil Solid Phase and the Soil Solution

Summary State-of-the-art foam and mist drilling suggests a need for predictive models for volumetric requirements that properly account for frictional losses caused by the solid phase in solids/foam slurry flow, settling velocities of such solids, and pressure drop across bit nozzles during foam flow. The objective of this paper is to fulfill this need. A model that predicts pressure drop across bit nozzles for foam and mist is presented. It accounts for the compressibility of foam but assumes negligible pressure losses resulting from friction and change in elevation. A model has been developed for predicting minimum volumetric requirements for foam and mist drilling operations. It accounts for the frictional losses caused by the solid phase, pressure drop across bit nozzles, and particle-settling velocity. The technique offers a high degree of flexibility in the selection of wellhead injection pressures and volumetric injection rates. Field application of this work can be accomplished by two primarily graphical methods that depend on compressor specifications: variable-backpressure and constant-backpressure schedules. Charts are presented for 7.875- and 9.00-in. [20.0- and 22.9-cm] hole sizes, and for 0.500-, 0.75-, and 1.00-in. [1.27-, 1.91-, and 2.54-cm] cutting sizes. Penetration rates range from 30 to 90 ft/hr [9 to 27 m/h]. Results indicate that volumetric requirements increase with increasing hole size, depth, and particle size. Increases in penetration rate cause only minor increases in volumetric requirements. All foam-drilling and well-cleanout operations can be accomplished within the laminar flow region with adherence to 0.55 minimum bottomhole and 0.96 maximum annular foam quality. Annular backpressures greater than atmospheric pressure are needed to maintain a bottomhole foam quality of 0.55 or more while reaching reasonable depths. To maintain constant depth as backpressure increases, however, both wellhead injection pressure and gas injection rate must be increased, and liquid flow rate decreased.

The usual measurements of P-v-T properties generally need very low cooling rates in order to make the temperature distribution uniform in the specimen, but the cooling rates in injection moldings are very high. The problems concerning the difference of the cooling rates were pointed out and discussed in a previous paper, and a method for determining P-v-T properties was proposed in the solid phase. In this paper we shall present also a method for determining P-v-T properties in the molten phase using the injection molding. The mean specific volume of the polymer in the cavity, that is calculated from the cavity volume and the weight of it can be assumed to be constant after gate-sealing, as long as the pressure of the polymer in the cavity is still above ambient pressure. The relationship among that mean specific volume, the temperature distribution in the thickness direction, and the pressure after gate-sealing has been presented using the Spencer-Gilmore's equation of state. Thereafter, according to the temperature and the pressure developments obtained from the injection molding process, the P-v-T properties in the molten phase were determined using that relationship. The constants of Spencer-Gilmore's equation of state in the molten phase were calculated from these P-v-T properties. The pressure developments and the volumetric shrinkages in the injection moldings were evaluated using the Spencer-Gilmore's equations obtained in both solid and molten phase. It was shown that they were in good agreements with the experimental values. It would be possible to predict more precisely the shrinkage and the warpage in injection moldings with our method.

Both the estimation of the time that small heavy particles remain inside a 3D vortex and the estimation of the average settling velocity of those particles are some important features in many practical situations. Previous works focused on the case of a horizontal 2D vortex. In this paper, we simulate the dynamics of heavy particles initially situated inside a three-dimensional vortex obtaining a formula for their average settling velocity. In a previous paper we obtained the trajectories of the particles and a formula that provides the time that they need to escape,Te⁎. This work simulates and analyses the escape process, and its main result is the obtaining, from numerical simulation, of a theoretical formulation of the average settling velocityVz⁎and its relationship with the elapsed time. We prove that the permanence time is of the order ofdp⁎-10(withdp⁎particle diameter) and that the average settling velocity is of the order ofTe⁎-1/5for sufficiently small particles. Some applications of the settling velocity formula developed in this work would be the design of mixture devices, the design of particle separation devices, and the prediction of the settling of pollutant particles, seeds, and pollen.

An experimental study of the settling velocities of single particles in non-Newtonian fluids

The aim of this study is to convert Nigella sativa black seed extract from liquid phase into solid phase by microencapsulation using spray drying method. The benefits hoped from this research are obtaining the dry extract to be formulated into pharmaceutical variable dosage forms in order to increase the usefulness and variability products ofNigella sativa black seed extract. The spray drying method was done by adding Nigella sativa black extract into the gum arabic and maltodextrin solution. The evaluation of microencapsulated extract is including drug content, encapsulation efficiency, flowproperties, compressibility, angle of repose, moisture content, particel size distribu-tion and microstructure of microcapsules. The result showed that microencapsula-tion of Nigella sativa black seed extract can be produced by spray drying method. The highest microencapsulation efficiency is at the coating solution concentration of 20% (gum arabic : maltodextrin = 50 : 50) and Nigella sativa black extract percentage of 30%.

Physicochemical, rheological and antioxidant potential of corn fiber gum

Particle drag coefficients in turbulent fluids

The solid and liquid phases of two-dimensional ${}^{4}\mathrm{He}$ are studied in detail using a variational ``shadow'' wave function. This wave function provides a unified description of both phases; spontaneous crystallization from a disordered initial state occurs in the solid phase. We have investigated the properties of the solid phase in detail and find that it lacks long range translational order, has a high density of defects, and low angular order relative to classical two-dimensional solids. These results are very similar to results obtained from simulations of a quantum hard disk system. We have also computed these properties for the liquid phase. These properties vary rapidly in the transition region and serve as a good signal for the transition itself.

The present paper is concerned with the propagation of plane waves in a porous medium composed of two solids and two immiscible fluids. Using the principal of virtual complementary work, the expression for complementary strain energy density has been derived and the stress–strain relations for isotropic porous medium are obtained. The capillary pressure arising due to the pressure difference at the interface of two fluid phases has been taken into account, and the solid phases are assumed to be weakly coupled. The idea of compressibility tests is used to find values of the coefficients occurring into the stress–strain relations in terms of the physical properties of individual solid and fluid phases. The equations of motion are obtained using Lagrangian approach, and it has been shown that there may exist four compressional and two shear waves in the medium. Phase speeds of these waves are computed numerically and their dependence on frequency has been depicted graphically.

This study aimed to experimentally investigate and statistically test changes in the settling velocity of particles falling in an aqueous solution due to an orbital shaking of the container. A series of settling experiments were conducted on coal samples under different combinations of shaking speed and initial concentration of the particles. First, a generalized version of the factorial design (a split‐plot design) was utilized to obtain the acquired data. Then, an appropriate statistical model was fitted to experimental data using settling velocity as a response while shaking speed and initial coal concentration were defined as factors. Graphic patterns confirmed our hypotheses that settling velocity is affected by the shaking speed, initial coal concentration and the interaction of these two factors. Results of the analysis indicated that the main effects of both initial coal concentration (F‐statistic = 775.75) and shaking speed (F‐statistic = 11.96) on the settling velocity are strongly significant (both with a P‐value near zero). Moreover, a strong interaction of the effects of these factors on the response variable was also observed (F‐statistic is 10.57 with a P‐value of near zero). Based on the results, combination of 4% coal concentration and 50 rpm shaking speed resulted in the highest settling velocity of 1.21 cm/s. In contract, a combination of 10% coal concentration and 100 rpm shaking speed led to a settling velocity of only 0.55 cm/s. Findings of this study may have invaluable benefits to the mineral and water treatment industries where design and construction of thickeners and sedimentation tanks equipped with orbital shakers can significantly accelerate the sedimentation of mineral particles as well as water contaminants.

The effects of nonlinear drag on the motion and settling velocity of heavy particles in a turbulent atmosphere are investigated. The authors approach the problem rather systematically by first considering the response of particles to much simpler fluid motions that are subprocesses of the more complex turbulent field. The authors first consider the motion and time response of particles falling under gravity in still fluid. Then the effects of a sudden gust or step change in relative velocity between a falling particle and its surrounding fluid are investigated. The authors demonstrate that horizontal relative motion produced by a sudden gust tends to reduce the settling velocity of a panicle. In simple oscillating fluids it is shown that the reduction of settling velocity increases with increasing amplitude of fluid oscillation. The authors also explore the effects of oscillation frequency on the settling velocity and show that if the period of fluid oscillation is less than the particle response...

A deeper understanding of the transport processes and pathways of pollutants and plastic debris in aquatic environments, such as water bodies, riverine and coastal zones, is required to effectively understand, prevent, and mitigate marine pollution. In this study, we present an updated version of the high-performance, three-dimensional Canadian Microplastics Simulation (CaMPSim-3D) particle tracking model (PTM), focused on simulating microplastics transport in marine and riverine environments. CaMPSim-3D is an efficient tool that utilizes the principles of ray tracing to enhance the accuracy and performance of particle simulations. New features of the PTM include the implementation of free-slip boundary conditions, particle settling and resuspension mechanisms, and turbulent diffusion, which improve the solution of the diffusion equations. A novel method for computing gradients over triangular prism elements and a double ray casting approach to solve the diffusion equations are also proposed. Additionally, accurate particle settling velocity for circular and elliptical microplastic fibres has been incorporated into the model. Several test cases are presented to demonstrate the new features of the PTM. A sensitivity analysis is performed to investigate the effects of different boundary conditions, particle settling velocity, and turbulent diffusion on the transport and fate of microplastics at two sites: the Saguenay Fjord and the Ottawa River. A test case for model validation against field sampling is also presented for the Ottawa River. The results show that the PTM is efficient, and the use of turbulent diffusion and settling/resuspension mechanisms is necessary, particularly when simulating sinking particles with higher density than water. The findings of this study provide valuable insights into the transport processes of microplastics in aquatic environments and can be used to improve the accuracy of microplastics simulations as well as to identify microplastics accumulation areas.

The challenges and risks relating to injectivity decline due to injection of particulate-laden water are well documented in the petroleum industry and elsewhere. Although different theories have been advanced to rationalize this problem, the modeling aspects remain largely unresolved, putting huge investments at risk. By combining the fractional-flow and deep-bed filtration (DBF) theories, this work formulates a new model for describing reservoir impairments due to suspension transport by injection water. The critical settling velocity of the suspended particulates is determined from fractional-flow theory and used to create a condition at which particle settling will occur, dependent on its size. The particle settling velocity as obtained from Stokes law for laminar flow (NRe ≪1) is compared to the critical settling velocity, which is a function of the residence time of the particles, to obtain the optimum transported particle size profile in the formation. Furthermore, the average size of transportable particulates and their total volumes are then obtained and used to determine the volume of deposits which is in turn used to develop a new injectivity decline model for predicting permeability impairment due to the deposition of suspended particles in the porous media. The resulting models are validated by analyzing reported dataset from two water injectors offshore Niger Delta. Overall, the results are reasonable as the impairment model rationalized available field dataset satisfactorily. The developed models should find relevance in the following field applications: (1) quantifying formation damage; (2) optimising water treatment facilities design; (3) implementing an effective and safe backflow operation.