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A Comprehensive Combination of Apparent and Shear Viscoelastic Data during Polymer Flooding for EOR Evaluations

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World Journal of Engineering and Technology 2017年第4期5卷 585-600页

作者： Muhammad Tahir Rafael E. Hincapie Michael Be Leonhard Ganzer Institute of Petroleum Engineering Clausthal University of Technology Clausthal-Zellerfeld Germany

We present a comprehensive workflow to obtain the best insights into the viscoelastic behavior of polymers. Viscoelasticity is depicted in most cases by the current commercially available polymers used for EOR applications. The phenomenon is debated to be one of the reasons for additional oil recovery during polymer flooding applications. It is somehow accepted that polymer increases volumetric sweep efficiency owing to improved mobility ratio. Recently researches have explained that flooding polymers in porous media with elastic characteristics could recover additional oil, due to the improved microscale oil displacement (pore-scale). This study focuses on the analysis of polymer viscoelasticity based on single-phase core, sand-pack and capillary tube (CT) experiments coupled with their detailed rheological characterization, in order to evaluate polymer behavior in porous media. A combination of hydrolyzed polyacrylamides (HPAM) polymers as well as a bio polymer is presented throughout this evaluation. The evaluation of the data is addressed on the basis of pressure drop across the pores, separating the shear associated pressure by the extensional thickening associated pressure. Apart from that, viscoelastic dependence of the converging-diverging geometry has been experimented. Based on the observed behavior through porous media, HPAM polymers are compared with bio polymers. Moreover, the behavior of solutions with induced mechanical degradation (pre-sheared) is compared with non-sheared solutions. Similarly, concentrations with different polymer solutions are evaluated. The results obtained in this work allow for additional understanding of polymer solutions behavior in flooding applications. Furthermore?The results support?the definition of optimized workflows to assess their behavior under flow through porous media. Finally this evaluation helps to describe the parameter that defines polymer viscoelastic properties.

关键词： Viscoelasticity Mechanical Degradation Elongational Viscosity Weissenberg Number

The Insphere of a Tetrahedron

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Applied Mathematics 2020年第7期11卷 601-612页

作者： Peter Paul Klein Computing Center University of Technology Clausthal Clausthal-Zellerfeld Germany

A contiguous derivation of radius and center of the insphere of a general tetrahedron is given. Therefore a linear system is derived. After a transformation of it the calculation of radius and center can be separated from each other. The remaining linear system for the center of the insphere can be solved after discovering the inverse of the corresponding coefficient matrix. This procedure can also be applied in the planar case to determine radius and center of the incircle of a triangle.

关键词： Corkscrew Rule Hesse Normal Form Decomposed Linear System Block Upper Triangular Form of Coefficient Matrix Cofactor Matrix

ELECTROCHEMICAL MEASUREMENTS OF COMPONENT ACTIVITIES IN METALLURGICAL SLAGS

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Acta Metallurgica Sinica(English Letters) 2003年第6期16卷 433-444页

作者： O.Volkova P.R.Scheller and D.Janke Institute of Iron and Steel Technology TU Bergakademie Freiberg D-09596 Freiberg GermanyInstitute of Iron and Steel Technology TU Bergakademie Freiberg D-09596 Freiberg Germany

The up-to-date status of FeO, CaO, SiO2, P2O5, Ti2O3 and Cr2O3 activity measurements in metallurgical slags using electrochemical sensors is outlined. A description of theoretical concepts and practical sensors is pre... 详细信息

关键词： electrochemical measurement sensor slag activity

Projection of the Semi-Axes of the Ellipse of Intersection

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Applied Mathematics 2017年第9期8卷 1320-1335页

作者： P. P. Klein Computing Center University of Technology Clausthal Clausthal-Zellerfeld Germany

It is well known that the line of intersection of an ellipsoid and a plane is an ellipse (see for instance [1]). In this note the semi-axes of the ellipse of intersection will be projected from 3d space onto a 2d plane. It is shown that the projected semi-axes agree with results of a method used by Bektas [2] and also with results obtained by Schrantz [3].

关键词： Ellipsoid and Plane Intersection Projection of the Semi-Axes of the Ellipse of Intersection

Improvement,validation and application of CFD/DEM model to dense gas-solid flow in a fluidized bed

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Particuology 2013年第5期11卷 514-526页

作者： Falah Alobaid Bernd Epple tu Darmstadt Energiesysteme und EnergietechnikPetersenstrasse 3064287 DarmstadtGermany

Dense gas-solid flow with solid volume fraction greater than 10% and at moderate Reynolds number is important in many industrial facilities such as fluidized beds. In this work, the Euler-Lagrange approach in combination with a deterministic collision model is applied to a laboratory-scale fluidized bed. The fluid-particle interaction is studied using a new procedure called the offset method, which results in several numbers of spatial displacements of the fluid grid. The proposed method is highly precise in determining porosity and momentum transfer, thus improving simutation accuracy. A validation study was carried out to assess the results using this in-house CFD/DEM code against 5-s operation of a Plex- iglas spouted-fluidized bed, showing good qualitative correlation of solid distribution in the bed and acceptable quantitative agreement of pressure drops at different positions in the bed. In view of high computing cost, special emphasis is placed on effective program design, such as application of advanced detection algorithm for particle-particle/wall collisions, the multi-grid method and parallel calculation. In this context, the influence of increasing the processor number, up to 36, on calculation efficiency was investigated.

关键词： Dense gas-solid flowComputational fluid dynamicsDiscrete element methodOffset methodParallelisation

turbulence model performance for ventilation components pressure losses

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Building Simulation 2022年第3期15卷 389-399页

作者： Karsten Tawackolian Martin Kriegel Hermann-Rietschel-Institut EnergyComfort&Health in BuildingsTU BerlinGermany

This study looks to find a suitable turbulence model for calculating pressure losses of ventilation *** building ventilation,the most relevant Reynolds number range is between 3×10^(4) and 6×10^(5),depending on the duct dimensions and airflow *** loss coefficients can increase considerably for some components at Reynolds numbers below 2×10^(5).An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number *** of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds *** effects near walls played an important role in the present *** turbulence modelling,near-wall damping functions are used to account for this influence.A model that implements near-wall modelling is the lag elliptic blending k-ε*** model gave reasonable predictions for pressure loss coefficients at lower Reynolds *** example is the low Reynolds number k-εturbulence model of Wilcox(LRN).The modification uses damping functions and was initially developed for simulating profiles such as aircraft *** has not been widely used for internal flows such as air duct *** on selected reference cases,the three closure coefficients of the LRN model were adapted in this work to simulate ventilation *** predictions were obtained with new coefficients(LRNM model).This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this *** the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

关键词： HVAC ductwork CFD simulation turbulence model model calibration

Anisotropic time-dependent behaviors of shale under direct shearing and associated empirical creep models

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第4期16卷 1262-1279页

作者： Yachen Xie Michael Z.Hou Hejuan Liu Cunbao Li Shenzhen Key Laboratory of Deep Engineering Sciences and Green Energy Shenzhen UniversityShenzhen518060China Institute of Subsurface Energy Systems Clausthal University of TechnologyClausthal-Zellerfeld38678Germany State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China

Understanding the anisotropic creep behaviors of shale under direct shearing is a challenging *** this context,we conducted shear-creep and steady-creep tests on shale with five bedding orientations (i.e.0°,30°,45°,60°,and 90°),under multiple levels of direct shearing for the first *** results show that the anisotropic creep of shale exhibits a significant stress-dependent *** a low shear stress,the creep compliance of shale increases linearly with the logarithm of time at all bedding orientations,and the increase depends on the bedding orientation and creep *** high shear stress conditions,the creep compliance of shale is minimal when the bedding orientation is 0°,and the steady-creep rate of shale increases significantly with increasing bedding orientations of 30°,45°,60°,and 90°.The stress-strain values corresponding to the inception of the accelerated creep stage show an increasing and then decreasing trend with the bedding orientation.A semilogarithmic model that could reflect the stress dependence of the steady-creep rate while considering the hardening and damage process is *** model minimizes the deviation of the calculated steady-state creep rate from the observed value and reveals the behavior of the bedding orientation's influence on the steady-creep *** applicability of the five classical empirical creep models is quantitatively *** shows that the logarithmic model can well explain the experimental creep strain and creep rate,and it can accurately predict long-term shear creep *** on an improved logarithmic model,the variations in creep parameters with shear stress and bedding orientations are *** abovementioned findings,a mathematical method for constructing an anisotropic shear creep model of shale is proposed,which can characterize the nonlinear dependence of the anisotropic shear creep behavior of shale on the bedding orientation.

关键词： Rock anisotropy Direct shear creep Creep compliance Steady-creep rate Empirical model Creep constitutive model

The quest for conditional independence in prospectivity modeling： weights-of-evidence, boost weights-of-evidence, and logistic regression

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Frontiers of Earth Science 2016年第3期10卷 389-408页

作者： Helmut SCHAEBEN Georg SEMMLER Department of Geophysics and Geoinformatics TU Bergakademie Freiberg Freiberg 09596 Germany

The objective of prospectivity modeling is prediction of the conditional probability of the presence T = 1 or absence T = 0 of a target T given favorable or prohibitive predictors B, or construction of a two classes {0,1} classification of T. A special case of logistic regression called weights-of-evidence （WofE） is geolo- gists＇ favorite method of prospectivity modeling due to its apparent simplicity. However, the numerical simplicity is deceiving as it is implied by the severe mathematical modeling assumption of joint conditional independence of all predictors given the target. General weights of evidence are explicitly introduced which are as simple to estimate as conventional weights, i.e., by counting, but do not require conditional independence. Complementary to the regres- sion view is the classification view on prospectivity modeling. Boosting is the construction of a strong classifier from a set of weak classifiers. From the regression point of view it is closely related to logistic regression. Boost weights-of-evidence （BoostWofE） was introduced into prospectivity modeling to counterbalance violations of the assumption of conditional independence even though relaxation of modeling assumptions with respect to weak classifiers was not the （initial） purpose of boosting. In the original publication of BoostWofE a fabricated dataset was used to ＂validate＂ this approach. Using the same fabricated dataset it is shown that BoostWofE cannot generally compensate lacking condi- tional independence whatever the consecutively proces- sing order of predictors. Thus the alleged features of BoostWofE are disproved by way of counterexamples, while theoretical findings are confirmed that logistic regression including interaction terms can exactly com- pensate violations of joint conditional independence if the predictors are indicators.

关键词： general weights of evidence joint conditionalindependence naive Bayes model Hammersley-Cliffordtheorem interaction terms statistical significance

Experimental and computational analysis of the coolant distribution considering the viscosity of the cutting fluid during machining with helical deep hole drills

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Advances in Manufacturing 2022年第2期10卷 235-249页

作者： Ekrem Oezkaya Sebastian Michel Dirk Biermann Institute of Machining Technology Dortmund University of Technology(TU Dortmund)Dortmund 44227Germany

An experimental analysis regarding the distribution of the cutting fluid is very difficult due to the inaccessibility of the contact zone within the bore ***,suitable simulation models are necessary to evaluate new tool designs and optimize drilling *** this paper the coolant distribution during helical deep hole drilling is analyzed with high-speed *** particles are added to the cutting fluid circuit bya developed high-pressure mixing *** the evaluation of suitable particle size,particle concentration and coolant pressure,a computational fluid dynamics(CFD)simulation is validated with the experimental *** comparison shows a very good model quality with a marginal difference for the flow velocity of 1.57%between simulation and *** simulation considers the kinematic viscosity of the *** results show that the fluid velocity in the chip flutes is low compared to the fluid velocity at the exit of the coolant channels of the tool and drops even further between *** velocity and the flow pressure directly at the cutting edge decrease to such an extent that the fluid cannot generate a sufficient cooling or *** the CFD simulation a deeper understanding of the behavior and interactions of the cutting fluid is *** on these results further research activities to improve the coolant supply can be carried out with great potential to evaluate new tool geometries and optimize the machining process.

关键词： Computational fluid dynamics(CFD)analysis:Viscosity-Tracermicro particles Fluidbehavior Helical deep hole drilling