Rheological Formulation Research Articles

Applicability of two-phase modeling with compression experiments for snow compaction dynamics

Compaction is a rheological process which, in many fields, has been modeled using a 1-D two-phase continuum framework. However, only recently has it been posed as a promising method for modeling the densification of snow into glacial ice, where the conventional model is empirical or semi-empirical. Here, we explore the applicability of a standard one-dimensional two-phase continuum framework for modeling snow compaction through theoretical and laboratory methods by analyzing and simplifying theory, and then experimentally constraining the model coefficient. We find in our theory analysis that the limit of slow compaction is reached such that air evacuation during the compaction process does not impede the deformation of ice grains. Model-data comparisons are performed using data from a series of uniaxial compression experiments of snow samples under a range of compaction rates (1 × 10−6 to 3 × 10−5 m s−1) and densities (250 to 450 kg m−3) at −10° and –20 °C, which show good measures of fit (r2>0.996). By defining a linear effective pressure function, we then constrain the model parameter by tuning against the data. While our model follows proper simplification of theory, the temperature and microstructural dependence are determined exclusively by the model parameter in a rheological formulation with the strain rate, and much scatter still exists. Within the selected range of compaction rates and densities, our results indicate that a 1-D two-phase model with a continuum framework alone does not likely capture important processes involved in the compaction process.

Towards improving short-term sea ice predictability using deformation observations

Abstract. Short-term sea ice predictability is challenging despite recent advancements in sea ice modelling and new observations of sea ice deformation that capture small-scale features (open leads and ridges) at the kilometre scale. A new method for assimilation of satellite-derived sea ice deformation into numerical sea ice models is presented. Ice deformation provided by the Copernicus Marine Service is computed from sea ice drift derived from synthetic aperture radar at a high spatio-temporal resolution. We show that high values of ice deformation can be interpreted as reduced ice concentration or increased ice damage – i.e. scalar variables responsible for ice strength in brittle or visco-plastic sea ice dynamical models. This method is tested as a proof of concept with the neXt-generation Sea Ice Model (neXtSIM), where the assimilation scheme uses a data insertion approach and forecasting with one member. We obtain statistics of assimilation impact over a long test period with many realisations starting from different initial times. Assimilation and forecasting experiments are run on synthetic and real observations in January 2021 and show increased accuracy of deformation prediction for the first 3–4 d. Similar conclusions are obtained using both brittle and visco-plastic rheologies implemented in neXtSIM. Thus, the forecasts improve due to the update of sea ice mechanical properties rather than the exact rheological formulation. It is demonstrated that the assimilated information can be extrapolated in space – gaps in spatially discontinuous satellite observations of deformation are filled with a realistic pattern of ice cracks, confirmed by later satellite observations. The limitations and usefulness of the proposed assimilation approach are discussed in a context of ensemble forecasts. Pathways to estimate intrinsic predictability of sea ice deformation are proposed.

Rheological formulation of room temperature vulcanizing silicone elastomer ink for extrusion-based 3D printing at room temperature

Silicone elastomer is a versatile material that is widely used in various industries due to its exceptional properties such as resistance to extreme temperatures, thermal conductivity, and bioinert. However, conventional fabrication methods of silicone are limited by molding which has design restrictions and makes it unsuitable for highly customized applications. This study presents a novel room temperature vulcanizing (RTV) silicone formulation that enables three-dimensional printing using an extrusion-based method. The study identifies that rheological measurements such as static yield stress are critical in determining the success of 3D silicone printing. Chemical additives, including nano-silica and plasticizers, have a significant impact on the static yield stress of the silicone ink, enabling the printing of complex structures. By adding 7 wt% of nano-silica and 10 wt% of plasticizers, a static yield stress of 400 Pa was achieved, which allowed the printing of complex 3D structures, including supportless macro-porous scaffolds. The newly formulated silicone ink demonstrated printability and the ability to achieve complex structures, reducing fabrication time, improving scalability, and allowing flexibility in the scaffold's design and specifications. This novel approach opens up new possibilities for the development of highly customized and cost-effective silicone-based 3D printing ink for the fabrication of complex silicone articles and macro-porous scaffolds. The potential applications of this approach include tissue engineering and biomedical devices.

Dynamics of unsteady axisymmetric of Oldroyd-B material with homogeneous-heterogeneous reactions subject to Cattaneo-Christov heat transfer

In several industrial and engineering applications, the Catteno-Christov heat flux plays a major role in the flow and heat transport of non-Newtonian fluids. Therefore, the goal of this study is to investigate the characteristics of homogeneous-heterogeneous reactions in the axisymmetric flow of Oldroyd-B materials using heat conduction analysis. The heat transfer phenomenon is examined from the non-Fourier heat flux model perspective. The governing flow field equations are developed using the rheological formulation of the Oldroyd-B fluid model, which is transformed into a set of nonlinear differential equations by utilizing the proper similarity conversions. The series solutions for the velocity, thermal, and solutal distribution are derived. The physical behaviors of relevant parameters are discussed in detail. The findings reveal that for the curvature parameter, the fluid velocity improves near the cylinder surface and no motion occurs away from the surface, while this predicts the dual behavior on temperature and concentration distributions. Further, fluid relaxation and retardation time exhibit opposite behavior on fluid velocity. Additionally, the results demonstrate that the homogeneous response parameter exhibits contradicting behavior on the concentration field while the thermal relaxation parameter lowers the temperature field.

On the Choice and Implications of Rheologies That Maintain Kinematic and Dynamic Consistency Over the Entire Earthquake Cycle

AbstractViscoelastic processes in the upper mantle redistribute seismically generated stresses and modulate crustal deformation throughout the earthquake cycle. Geodetic observations of these motions at the surface of the crust‐mantle system offer the possibility of constraining the rheology of the upper mantle. Parsimonious representations of viscoelastically modulated deformation through the aseismic phase of the earthquake cycle should simultaneously explain geodetic observations of (a) rapid postseismic deformation, (b) late in the earthquake cycle near‐fault strain localization. To understand how rheological formulations affect kinematics, we compare predictions from time‐dependent forward models of deformation over the entire earthquake cycle for an idealized vertical strike‐slip fault in a homogeneous elastic crust underlain by a homogeneous viscoelastic upper‐mantle. We explore three different rheologies as inferred from laboratory experiments: (a) linear Maxwell, (b) linear Burgers, (c) power‐law. The linear Burgers and power‐law rheologies are consistent with fast and slow deformation phenomenology over the entire earthquake cycle, while the single‐layer linear Maxwell model is not. The kinematic similarity of linear Burgers and power‐law models suggests that geodetic observations alone may be insufficient to distinguish between them, but indicate that one may serve as an effective proxy for the other. However, the power‐law rheology model displays a postseismic response that is non‐linearly dependent on earthquake magnitude, which may offer a partial explanation for observations of limited postseismic deformation near some magnitude 6.5–7.0 earthquakes. We discuss the role of mechanical coupling between frictional slip and viscous creep in controlling the time‐dependence of regional stress transfer following large earthquakes and how this may affect the seismic hazard and risk to communities living close to fault networks.

Novel discretization strategies for the 2D non-Newtonian resistance term in geophysical shallow flows

In the context of two-dimensional models for complex geophysical surface flows such as debris flows, muddy slurries, oil spills over land, hyperconcentrated floods, lava flows, etc, depth-averaged rheological models relate the shear stress state within the fluid column to the depth-averaged local flow features. Despite it is the most influencing term on the mobility of complex shallow flows, the numerical treatment of the resistance contribution to the flow momentum is still a challenging topic, especially when dealing with 2D large-scale applications. In this work, two novel strategies for the explicit upwind discretization of generalized non-Newtonian resistance terms in two-dimensional numerical models are proposed, called integral and differential approaches. These new strategies are applicable to generalized rheological formulations in any type of mesh topology. Results from benchmark tests running in orthogonal, triangle structured and triangle unstructured meshes demonstrate that both approaches represent an improvement for the explicit upwind integration of the 2D resistance force compared with previous procedures. It is shown that the alignment of the flow with the mesh main-axis, which has been previously attributed to faults of 2D FV numerical methods and insufficient mesh refinements, is directly related to the loss of the rotational invariance of the integrated resistance force. This is caused by the erroneous procedure for including the 2D resistance term into the local flux balance at the cell edges. Furthermore, a novel implicit centered method for the integration of the 2D resistance force has also been derived for the quadratic frictional non-linear resistance formulation. Despite the implicit procedure fails to converge to steady uniform flow states, the differential explicit upwind and the implicit centered methods show similar level of accuracy, robustness and computational efficiency for transient 2D frictional visco-plastic flows.

Finite Element Analysis for Nonlinear Unbonded Circular Fiber-Reinforced Elastomeric Bearings

In recent years, interest in low-cost seismic isolation systems has increased. The replacement of the steel reinforcement in conventional elastomeric bearings for a carbon fiber reinforcement is a possible solution and has garnered increasing attention. To investigate the response of fiber-reinforced elastomeric bearings (FREBs) under seismic loads, it is fundamental to understand its mechanical behavior under combined vertical and horizontal loads. An experimental investigation of the components presents complexities due to the high loads and displacements tested. The use of a finite element analysis can save time and resources by avoiding partially expensive experimental campaigns and by extending the number of geometries and topologies to be analyzed. In this work, a numerical model for carbon fiber-reinforced bearings is implemented, calibrated, and validated and a set of virtual experiments is designed to investigate the behavior of the bearings under combined compressive and lateral loading. Special focus is paid to detailed modeling of the constituent materials. The elastomeric matrix is modeled using a phenomenological rheological model based on the hyperelastic formulation developed by Yeoh and nonlinear viscoelasticity. The model aims to account for the hysteretic nonlinear hyper-viscoelastic behavior using a rheological formulation that takes into consideration hyperelasticity and nonlinear viscoelasticity and is calibrated using a series of experiments, including uniaxial tension tests, planar tests, and relaxation tests. Special interest is paid to capturing the energy dissipated in the unbonded fiber-reinforced elastomeric bearing in an accurate manner. The agreement between the numerical results and the experimental data is assessed, and the influence of parameters such as shape factor, aspect ratio, vertical pressure, and fiber reinforcement orientation on stress distribution in the bearings as well as in the mechanical properties is discussed.

Toward Optimization of Rheology in Sea Ice Models through Data Assimilation

AbstractSea ice models that allow for deformation are primarily based on rheological formulations originally developed in the 1970s. In both the original viscoplastic (VP) and elastic-VP schemes, the internal pressure term is modeled as a function of variable sea ice thickness and concentration with spatially and temporally constant empirical parameters for ice strength. This work considers a spatially variable extension of the rheology parameters as well as wind stress in a one-dimensional VP sea ice data assimilation system. In regions of total ice cover, experiments that assimilate synthetic ice-state observations using variable rheological parameters show larger improvements than equivalent experiments using homogeneous parameters. For partially ice-covered regions where internal ice stresses are relatively unimportant, experiments assimilating synthetic sea ice velocity observations demonstrate reasonable reconstruction of spatially variable wind stresses. These results suggest practical benefits for sea ice–state reconstruction and forecasts by using sea ice velocity, thickness, and concentration observations to optimize spatially varying rheological parameters and to improve wind stress forcing.

Thermal and Rheological Formulation and Evaluation of Synthetic Bitumen from Reprocessed Polypropylene and Oil

Bitumen from the catalytic cracking of petroleum is widely used in the construction industry as a binder for mineral aggregates paving asphalt cement (PAC). However, this material has serious limitations for use at different temperatures. Modifications with polymers have been widely studied to improve the properties of this material and increase its useful life. As a result of the increased environmental risk, the volume of solid waste (MSW) can be used as an alternative to the best use of this material. One of these is the formulation of synthetic bitumen (binders) from mixtures of lubricant oil/polymer that can show better when compared to traditional and modified bitumen. In this work, a mixture of lubricating oil and recycled polypropylene (PP) was made for the formulation of synthetic bitumens. The rheological analyses carried out on the material indicate that at low temperatures the formulated material shows high loading modulus values, indicating high mechanical strength, and the material also presented high resistance to permanent deformation; the viscosity profile indicates that the material is highly pseudoplastic presenting high viscosity at zero shear rate and low visibility at high shear rates, highlighting the samples containing 10 and 20% of polymer material in the formation as the best for use as one of the components of the pavement cement.

Predicting the sinkage of a moving tracked mining vehicle using a new rheological formulation for soft deep-sea sediment

The sinkage of a moving tracked mining vehicle is greatly affected by the combined compression-shear rheological properties of soft deep-sea sediments. For test purposes, the best sediment simulant is prepared based on soft deep-sea sediment from a C-C poly-metallic nodule mining area in the Pacific Ocean. Compressive creep tests and shear creep tests are combined to obtain compressive and shear rheological parameters to establish a combined compressive-shear rheological constitutive model and a compression-sinkage rheological constitutive model. The combined compression-shear rheological sinkage of the tracked mining vehicle at different speeds is calculated using the RecurDyn software with a selfprogrammed subroutine to implement the combined compression-shear rheological constitutive model. The model results are compared with shear rheological sinkage and ordinary sinkage (without consideration of rheological properties). These results show that the combined compression-shear rheological constitutive model must be taken into account when calculating the sinkage of a tracked mining vehicle. The combined compression-shear rheological sinkage decrease with vehicle speed and is the largest among the three types of sinkage. The developed subroutine in the RecurDyn software can be used to study the performance and structural optimization of moving tracked mining vehicles.

An examination of the rheology of flocculated clay suspensions

A dense cohesive sediment suspension, sometimes referred to as fluid mud, is a thixotropic fluid with a true yield stress. Current rheological formulations struggle to reconcile the structural dynamics of cohesive sediment suspensions with the equilibrium behaviour of these suspensions across the range of concentrations and shear. This paper is concerned with establishing a rheological framework for the range of sediment concentrations from the yield point to Newtonian flow. The shear stress equation is based on floc fractal theory, put forward by Mills and Snabre (1988). This results in a Casson-like rheology equation. Additional structural dynamics is then added, using a theory on the self-similarity of clay suspensions proposed by Coussot (1995), giving an equation which has the ability to match the equilibrium and time-dependent viscous rheology of a wide range of suspensions of different concentration and mineralogy.

Comparative Study of Basic Properties of Mud Prepared with Nigerian Local Clay and Mud Prepared with Foreign Clay: A Case Study of Abbi Clay Deposit

This research study evaluates the performance of a local clay sample for drilling operations in Nigeria. The rheological and the thixotropic properties as well as other parameters of the Local clay mud was seen to have improved, but however, when beneficiated with chemical additives, there was an increase in the overall parameters of the Local mud samples, making it ideal for any industrial application as its parameters met with the stipulated standard specifications of API, OCDA. The rheological formulation of the locally sourced bentonite clay sample in substitute for the imported foreign bentonite clay was carried out by the comparative analysis of the parameters of the local mud with the stipulated API standard values to ascertain the level of compliance in drilling operation. The local mud PH values responded positively on beneficiation with 1.0g of potash, the modification raised the mud PH value to fall within the standard range of 9.5 to 12.5. The viscosity of the local mud was seen to be slightly below the standard requirement of 30cp, but appreciated favorably to the standard requirement when beneficiated with 1.0g of drispac. It was obvious that the prepared local mud sample parameters such as the sand percentage composition, power law index, density, marsh funnel viscosity, etc. met the minimum required specifications, while other few parameters such as the rheological properties, and pH, needed some additive treatment for favorable comparison with the foreign clay mud properties. Therefore, the utilization of this clays for any industrial application will pose no harm to surface and subsurface facilities and will in turn represent a value added to the Nigeria’s economy by the total prevention of the importation of high quality activated foreign bentonite clay.

Comparative Study of Basic Properties of Mud Prepared with Nigerian Local Clay and Mud Prepared with Foreign Clay: A Case Study of Abbi Clay Deposit

This research study evaluates the performance of a local clay sample for drilling operations in Nigeria. The rheological and the thixotropic properties as well as other parameters of the Local clay mud was seen to have improved, but however, when beneficiated with chemical additives, there was an increase in the overall parameters of the Local mud samples, making it ideal for any industrial application as its parameters met with the stipulated standard specifications of API, OCDA. The rheological formulation of the locally sourced bentonite clay sample in substitute for the imported foreign bentonite clay was carried out by the comparative analysis of the parameters of the local mud with the stipulated API standard values to ascertain the level of compliance in drilling operation. The local mud PH values responded positively on beneficiation with 1.0g of potash, the modification raised the mud PH value to fall within the standard range of 9.5 to 12.5. The viscosity of the local mud was seen to be slightly below the standard requirement of 30cp, but appreciated favorably to the standard requirement when beneficiated with 1.0g of drispac. It was obvious that the prepared local mud sample parameters such as the sand percentage composition, power law index, density, marsh funnel viscosity, etc. met the minimum required specifications, while other few parameters such as the rheological properties, and pH, needed some additive treatment for favorable comparison with the foreign clay mud properties. Therefore, the utilization of this clays for any industrial application will pose no harm to surface and subsurface facilities and will in turn represent a value added to the Nigeria’s economy by the total prevention of the importation of high quality activated foreign bentonite clay.

A fractional derivative Zener model for the numerical simulation of base isolated structures

A fractional derivative Zener (FDZ) model connected in parallel with a linear viscous damper and a Coulomb friction slider is used to numerically simulate the mechanical behavior of a base isolated (BI) building tested under free vibration conditions in Solarino, Sicily. This hybrid BI system comprises high damping rubber bearings in combination with low friction sliding bearings. A comparison study of the present model with previous ones appearing in the literature, namely the bi-linear and the tri-linear models defined in the time domain, is carried out here. Furthermore, the linear viscoelastic solid, namely the classical Zener model, is also implemented and evaluated. The rheological models representing all the above BI systems are analyzed and, for the first time, the rheological formulation for the tri-linear model is presented. The present comparison study shows that the FDZ model is capable of describing the complex nonlinear response of BI systems.

A numerical model for simulation of fluid mud with different rheological behaviors

In this paper, a three-dimensional isopycnal approach is presented to simulate the dynamics of fluid mud covering the formation, development, transport, and disappearance of fluid mud. The basic assumption is the assignment of the fluid’s density as the indicating parameter for the rheological behavior. Considering stable stratification, as is usually the case for fluid mud, layers of constant density discretize the vertical domain. The non-Newtonian dynamics of fluid mud is simulated by solving the Cauchy equations for general continuum dynamics. Instead of using a turbulent viscosity approach, the viscosity is allowed to vary according to the rheological behavior of mud suspensions. This apparent viscosity can be determined for different rheological formulations in dependence of the volume solid fraction and the shear rate. An existing three-dimensional isopycnal hydrodynamic model was extended for vertical mass transport processes and was applied on a schematic system with hindered settling. For including the rheological behavior of fluid mud, the Worrall–Tuliani approach was parameterized and implemented. The resulting flow behavior is shown on a model application of fluid mud layers moving down an inclined plane. With these changes, it is demonstrated that the isopycnal model is capable of simulating fluid mud dynamics.

791 MORPHINE SULPHATE AND MORPHINE HYDROCHLORIDE VEHICULUM RHEOLOGICAL FORMULATION PARAMETERS IN VITRO DIFFUSION PROCES

European Journal of PainVolume 10, Issue S1 p. S206-S206 791 MORPHINE SULPHATE AND MORPHINE HYDROCHLORIDE VEHICULUM RHEOLOGICAL FORMULATION PARAMETERS IN VITRO DIFFUSION PROCES G. Samczewska, G. Samczewska Department of Applied Pharmacy Medical University of LodzSearch for more papers by this authorM.M. Zgoda, M.M. Zgoda Department of Applied Pharmacy Medical University of LodzSearch for more papers by this authorA. Cialkowska-Rysz, A. Cialkowska-Rysz Palliative Medicine Unit Oncology Department Medical University of Lodz, PolandSearch for more papers by this authorS. Kazmierczak-Lukaszewicz, S. Kazmierczak-Lukaszewicz Palliative Medicine Unit Oncology Department Medical University of Lodz, PolandSearch for more papers by this author G. Samczewska, G. Samczewska Department of Applied Pharmacy Medical University of LodzSearch for more papers by this authorM.M. Zgoda, M.M. Zgoda Department of Applied Pharmacy Medical University of LodzSearch for more papers by this authorA. Cialkowska-Rysz, A. Cialkowska-Rysz Palliative Medicine Unit Oncology Department Medical University of Lodz, PolandSearch for more papers by this authorS. Kazmierczak-Lukaszewicz, S. Kazmierczak-Lukaszewicz Palliative Medicine Unit Oncology Department Medical University of Lodz, PolandSearch for more papers by this author First published: 13 January 2012 https://doi.org/10.1016/S1090-3801(06)60794-5Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, IssueS1September 2006Pages S206-S206 RelatedInformation

Conceptual and physical clarification of rate and state friction: Frictional sliding as a thermally activated rheology

We observed slow frictional slip occurring at a constant shear stress below the nominal friction level and compared it with the time‐dependent strengthening of the frictional interface, which was also tracked experimentally. It was found that slip velocity decreases as the interface strengthens due to aging, while it increases with the applied shear stress. These dependencies were both exponential and were of similar magnitudes, as implied by the framework law of rate‐ and state‐dependent friction. In the spirit of the adhesion theory of friction the dependence of slip velocity on interface strength is understood to be the result of the change of the shear stress acting on frictional junctions due to the change of junction population, though the observed dependence was somewhat stronger than a simple model based on this idea predicts. By correcting the observed slip velocity for the effect of the change of the interface strength, we could obtain a unique relationship between stress and slip velocity, which may be readily compared with a standard rheological formulation. Thus the obtained relationship between stress and slip velocity showed a reasonable agreement with the absolute rate theory over a temperature range of 25–800°C for the present experimental condition (fine albite powder, 20 MPa normal stress, no pore water).

Effect of Temperature on Characteristics of Hydroxypropylcellulose Tablets Prepared by Wet Granulation Methods

In this work, we will study the effect of temperature (35-45°C) on the disintegration and dissolution rate of theophylline from the tablets containing hydroxypropylcellulose as a binder (binder in solution). The results showed that in all cases the increase of the temperature led to the acceleration of the disintegration and the dissolution rate of theophylline tablets except in basic formula. The disintegration and dissolution times decrease gradually, then abruptly fall in time at the demixing temperature and take the same time as the basic formula. It was also observed that the demixing temperature varies with the concentration of the polymer in the tablet formulation and shows no change in rheological formulation.

Pressure filtration of flocculated suspensions

AbstractFrom the development of a compressional rheology of a flocculated suspension, a number of separation processes have been modeled. With respect to the two‐stage pressure filtration process of compact formation and then consolidation, the rheological formulation appears at first examination to eb significantly at variance with the conventional engineering approach. The present model may be reconciled to the early engineering model. Moreover, the filtration parameters extracted from experiments can be related to the more fundamental rheological parameters, r(ϕ), the hindered settling factor, which is a function of solids volume fraction ϕ — it takes into account hydrodynamic interactions between local particles, which increase the drag forces. Useful estimates of the compact bed formation resistance and the formation time are provided as a function of applied pressure. The initial time dependence of the consolidation ratio on the elapsed consolidation time is not found to be a square root behaviour as suggested by the conventional modeling.

Effect of three-dimensionality and soil creep on the distribution of vertical stresses? y above tunnels constructed in the body of a high earth-rock dam

1. The effect of three-dimensionality of the site on the distribution of stressesσy above the tunnels is considerable; the narrower the site, the greater this effect. 2. A deficit of the values ofσy relative toγsy is noted in all stages of constructing the dam. 3. The maximum stressesσy above the tunnels are reached in the middle sections of the tunnels and are slightly less thanγsy, which can be considered equal to the latter. 4. Near the tunnel walls are noted zones having a practically zero value, which is an important factor that must be taken into account when calculating the strength of the tunnels. 5. The levels of stressesσy near the canyon walls considerably lag behindγsy, which applies to all construction stages. On the basis of calculating the SSS of the dam in a three-dimensional rheological formulation, we can propose a stepped scheme of the acting vertical loads, which leads to a saving of tunnel concrete.