Rheological Description Research Articles

Influence of Fluid Rheology on Blood Flow Haemodynamics in Patient-Specific Arterial Networks of Varied Complexity – In-Silico Studies

Abstract Results obtained with computational fluid dynamics (CFD) rely on assumptions made during a pre-processing stage, including a mathematical description of a fluid rheology. Up to this date there is no clear answer to several aspects, mainly related to the question of whether and under what conditions blood can be simplified to a Newtonian fluid during CFD analyses. Different research groups present contradictory results, leaving the question unanswered. Therefore, the objective of this research was to perform steady-state and pulsatile blood flow simulations using eight different rheological models in geometries of varying complexity. A qualitative comparison of shear- and viscosity-related parameters showed no meaningful discrepancies, but a quantitative analysis revealed significant differences, especially in the magnitudes of wall shear stress (WSS) and its gradient (WSSG). We suggest that for the large arteries blood should be modelled as a non-Newtonian fluid, whereas for the cerebral vasculature the assumption of blood as a simple Newtonian fluid can be treated as a valid simplification.

Generation of Evolving Plate Boundaries and Toroidal Flow From Visco‐Plastic Damage‐Rheology Mantle Convection and Continents

AbstractEarth's style of planetary heat transport is characterized by plate tectonics which requires rock strength to be reduced plastically in order to break an otherwise stagnant lithospheric lid, and for rocks to have a memory of past deformation to account for strain localization and the hysteresis implied by geological sutures. Here, we explore ∼107 Rayleigh number, visco‐plastic, 3‐D global mantle convection with damage. We show that oceanic lithosphere‐only models generate strong toroidal‐poloidal power ratios and features such as a mix of long‐wavelength tectonic motions and smaller‐scale, back‐arc tectonics driven by downwellings. Undulating divergent plate boundaries can evolve to form overlapping spreading centers and microplates, promoted and perhaps stabilized by the effects of damage with long memory. The inclusion of continental rafts enhances heat flux variability and toroidal flow, including net rotation of the lithosphere, to a level seen in plate reconstructions for the Cenozoic. Both the super‐continental cycle and local rheological descriptions affect heat transport and tectonic deformation across a range of scales, and we showcase both general tectonic dynamics and regionally applied continental breakup scenarios. Our work points toward avenues for renewed analysis of the typical, mean behavior as well as the evolution of fluctuations in geological and model plate boundary evolution scenarios.

Incorporating the complex rheological behavior of blood in microvascular network simulations: Two-phase modeling and a model reduction approach

Vessel flow resistance in microvascular network simulations is often computed using the single-phase approximation, where the no-slip boundary condition is imposed on the microvessel wall, and the "in vitro viscosity law" or "the relative hematocrit" relationships proposed by Pries et al. (1992) are utilized. However, these models have limitations due to their reliance on experimental data, which inherently contain measurement errors, thereby affecting their consistency and accuracy. To moderate these limitations, biphasic flow models can be employed, allowing for adaptable rheological descriptions of blood. Nevertheless, this approach presents challenges in terms of automation and computational cost. In order to address these challenges, we propose a monophasic steady-state model that consistently incorporates a wall-slip condition in place of the cell-free layer contribution. Model reduction is achieved by establishing an explicit relationship for the apparent slip length, which is calibrated through the regression of biphasic model results. Subsequently, simulations are conducted on microvessel network structures. The predictions of wall shear stress by the monophasic model exhibit deviations of less than 2 % from the expected values, within the range of vessel radii (10–75 μm) and discharge hematocrits (0.2–0.7). Furthermore, the computational time required is reduced by almost an order of magnitude compared to the biphasic model, rendering it suitable for multiscale biochemical simulations. The developed model closely approximates the flow resistance predictions of the biphasic model, while its modular nature allows for easy implementation of future modifications. Both models successfully reproduce experimental data by Lipowsky et al. (1978). Finally, we derive semi-analytical expressions for the apparent slip length and discuss why it is more appropriate to impose only the "relative hematocrit" relationship as a global constraint for calculating the hemodynamics in microvessels, rather than relying on the "in vitro viscosity law", which provides unreliable predictions at low values of the discharge hematocrit.

P21: Generalized blood rheological model for analyzing thrombus formation in venous valve architecture

The health impact of venous thromboembolism (VTE), a major cause of morbidity and mortality, can be appreciated from the large number of people affected, 1 million Americans and > 700,000 Europeans annually. The economic impacts of this have been the focus of several studies, with the annual cost to the US healthcare system of incident VTE being estimated at up to $10 billion. The non-Newtonian, shear-thinning blood rheology plays a major role in determining the shape and duration of stagnant fluid zones arising within the venous valve leaflet pockets where the thrombi occur. It has also been suggested that valve compression treatment ensuring oscillating shear stress at the vein wall within the pocket can prevent the formation of clots. Many models have been proposed for blood rheology, some with yield stress and others not, and these have been used extensively to model wall shear stress in models of coronary arteries, with a view to determining the likelihood of stenoses. In this new work, we propose a new non-Newtonian model whose parameters can be readily determined using a capillary rheometer. The model takes the form σ = σ0 + k εn + µ∞ ε where σ is the shear stress and is the ε shear strain rate. σ0 is the yield stress and the fluid viscosity at a high shear strain rate. This generalizes three of the existing models and eliminates the unphysical characteristics of each individual model. This model incorporates the Herschel-Bulkley, Casson, and K-L models as special cases. The overall aim of the work is to determine the effect of venous valve geometry on the likelihood of clot formation, using a realistic description of blood rheology.

Keynote lecture. Granular flows

Our understanding of granular flows has progressed considerably over the past two decades. In this talk, I will first review the advances made in the rheology of dense granular media based on the concept of pressure-imposed rheology, discussing the different regimes, from viscous to inertial. I will also illustrate how these rheological descriptions can be used in a two-phase flow approach to model more complex flow configurations, at least in simple small scaled experiments mimicking granular avalanche flows. Can these advances help describe and predict debris flows, is not an easy question, which I will try to discuss by pointing out the limitations and robustness of the rheological models.

Attempt to Model Lava Flow Faster Than Real Time: An Example of La Palma Using VolcFlow

The eruption of Cumbre Vieja (also known as Tajogaite volcano, 19 September–13 December 2021, Spain) is an example of successful emergency management. The lessons learnt are yet to be fully disclosed as is whether the response can be further improved. The latter may include tools to predict lava flow inundation rheological characteristics, amongst other issues related to volcanic eruptions (i.e., ash fall and gas emission). The aim of this study was to explore if a scientific open-source, readily available, lava-flow-modelling code (VolcFlow) would suffice for lava emplacement forecasting, focusing on the first seven days of the eruption. We only the open data that were released during the crisis and previously available data sets. The rheology of the lava, as well as the emission rate, are of utmost relevance when modelling lava flow, and these data were not readily available. Satellite lava extent analysis allowed us to preliminarily estimate its velocity, the average flow emitted, and flow viscosity. These estimates were numerically adjusted by maximising the Jaccard morphometric index and comparing the area flooded by the lava for a simulated seven-day advance with the real advance of the lava in the same timescale. The manual search for the solution to this optimization problem achieved morphometric matches of 85% and 60%. We obtained an estimated discharge rate of about 140 m3/s of lava flow during the first 24 h of the eruption. We found the emission rate then asymptotically decreased to 60 m3/s. Viscosity varied from 8 × 106 Pa s, or a yield strength of 42 × 103 Pa, in the first hours, to 4 × 107 Pa s and 35 × 103 Pa, respectively, during the remainder of the seven days. The simulations of the lava emplacement up to 27 September showed an acceptable distribution of lava thickness compared with the observations and an excellent geometrical fit. The calculations of the calibrated model required less time than the simulated time span; hence, flow modelling can be used for emergency management. However, both speed and accuracy can be improved with some extra developments and guidance on the data to be collected. Moreover, the available time for management, once the model is ready, quasi-linearly increases as the forecasting time is extended. This suggests that a predictive response during an emergency with similar characteristics is achievable, provided that an adequate rheological description of the lava is available.

Rheology of vesicle prototissues: A microfluidic approach

Synthetic biomimetic prototissues with reduced complexity can facilitate the understanding of intricate biological processes, by allowing the role of specific physical or chemical mechanisms to be isolated. The aim of the present work is to provide a rheological description of vesicle prototissues as a biomimetic model for the flow of cellular tissues, which can be relevant for the mechanical comprehension of embryogenesis or tumor metastasis. Prototissue were obtained by the controlled assembly of Giant Unilamellar Vesicles (GUVs) mediated by the biotin-streptavidin pair, using a simple assembly protocol. Prototissues were mechanically probed in a “pipette-aspiration” inspired microfluidic chip, under controlled pressure conditions. A viscoelastic flow behavior was obtained which was well captured by a generalized Kelvin-Voigt fluid model, with inferred rheological parameters that did not show a significant dependence on the GUV-GUV adhesion strength. In addition, the flow of the vesicle prototissues exhibited a strain-stiffening behavior. Complementary flow velocimetry analysis revealed a decrease of prototissue effective permeability with the applied pressure, and enabled to identify vesicle spatial reorganizations taking place within the prototissue. Overall, our microfluidic setup makes possible the simultaneous characterization of the biomimetic prototissue at two different length scales, global and local, bridging the viscoelastic response of the overall prototissue with its structural changes between an ensemble of vesicles.

Granulation and suspension rheology: A unified treatment

Mixing a small amount of liquid into a powder can give rise to dry-looking granules; increasing the amount of liquid eventually produces a flowing suspension. We perform experiments on these phenomena using Spheriglass, an industrially realistic model powder. Drawing on recent advances in understanding friction-induced shear thickening and jamming in suspensions, we offer a unified description of granulation and suspension rheology. A “liquid incorporation phase diagram” explains the existence of permanent and transient granules and the increase of granule size with liquid content. Our results point to rheology-based design principles for industrial granulation.

Role of viscoelastic fluid rheology in miscible viscous fingering

Classical viscous fingering patterns in flow displacement can be modulated by incorporating polymers into either of the two fluids. The polymeric solutions are viscoelastic fluids exhibiting both shear-thinning as well as elastic behavior. The present numerical study examines the dynamics of viscous fingering in miscible flow displacement with either displacing or displaced fluid being treated as polymeric fluid. The nonlinear rheology of the polymeric fluid is described using the White–Metzner model. The role of fluid rheology in the transient evolution of concentration field and fingering patterns defined using quantities such as mixing length, relative contact area, finger width, and the number of fingers, is investigated by performing numerical simulations. The correlation between fingering structure and rheological properties is established. The study shows that incorporation of polymer into the fluid alters the viscous fingering attributed to the three main factors: viscosity modification, shear-thinning behavior, and fluid elasticity. Primarily, incorporating polymers into the displaced (displacing) fluid leads to suppressed (enhanced) fingering patterns, attributed to modification of the viscosity contrast between two fluids, the governing parameter for viscous fingering. Interestingly, when the viscosity contrast at a gap-averaged shear-rate is held fixed, the shear-thinning behavior promotes the longitudinal growth of fingers irrespective of the fluid to which polymers are added. Moreover, the fluid elasticity ends to inhibit the growth of fingers leading to a more efficient flow displacement regardless of the flow arrangement. Thus, the study suggests that in addition to the viscosity at the gap-averaged shear-rate, the nature of the entire flow curve representing nonlinear rheology plays an important role in fingering dynamics. The mechanism for the destabilization due to shear-thinning behavior is explained by analyzing the vorticity structures, local shear-rate, and local viscosity distribution in the flow domain. The normal stress distribution is analyzed to comprehend the stabilization attributed to the fluid elasticity. Overall, the interplay between the viscosity contrast and the complete rheological description of the fluid governs the fingering dynamics.

Viscoelastoplastic classification of cementitious suspensions: transient and non-linear flow analysis in rotational and oscillatory shear flows

Rheological modeling of special concretes such as ultra-high performance concretes (UHPCs), self-compacting concretes (SCCs), or environmentally friendly concretes with low clinker contents but containing many fine particles increases model complexity because high amounts of colloidal and fine particles and complex chemistry result in strongly non-Newtonian rheological behavior. Straight-forward viscoplastic rheological models such as the well-known Bingham- or Herschel-Bulkley approach do not fit the flow behavior on a large scale at and lead to boundary value problems in numerical flow simulations. Increased viscoelastic properties due to chemical admixtures are not described by pure viscoplasticity analysis methods. To fill this gap, our research presents viscoplastic and viscoelastic linear and non-linear rheological characterization methods for common and strongly non-Newtonian cement pastes and combines the methods for a comprehensive viscoelastoplastic modeling of cementitious building materials. We illustrate and discuss the benefits and boundaries of each measurement technique in dependence of cementitious paste complexity. Three solid volume fractions from phi = 0.45 to 0.55 and three different flowability ranges, adjusted through varying superplasticizer amounts, were investigated in respect of steady-state and transient yield stress, viscosity, and non-linear viscoelastic material properties. Our results reveal that with increasing solid volume fraction and polymer amount, viscoelastoplastic modeling describes rheological flow on a large flow scale more appropriately than common viscoplastic methods. The results show a new approach for a full quantitative and qualitative rheological classification of cementitious building materials and thus improve the understanding of densely packed colloidal cementitious suspensions. The findings serve as prospective guideline to model complex cementitious building materials both at low and high shear rates, and to find an appropriate rheological description at the boundaries of flow.Graphical abstract

Rheological behaviour of pure clay and coarse-grained clay suspensions using an inclined blade vane-in-cup

Mixtures of clay and sand suspended in water are complex systems encountered in many industrial and environmental applications, but their understanding and modelling are still limited and require further investigations. In this way, the rheological behaviour of pure non-thixotropic clay and coarse-grained clay suspensions is investigated with a rotational rheometer equipped by an inclined blade vane-in-cup, where the type and the volume fraction of both fine clay and coarse materials are varied. The Herschel–Bulkley model τ = τ y + K γ ̇ n is used to describe successfully the flow curves of suspensions relating the shear stress τ to the shear rate γ ̇ , from which the yield stress τ y , the consistency K and the index n are deduced. The main contributions of this study are (i) to validate the inclined blade vane-in-cup for the estimation of the rheological behaviour of polymer microgels, pure clay suspensions, and coarse-grained clay suspensions, (ii) to conclude on the most appropriate model type to predict the yield stress of pure clay suspensions over a wide range of fine clay volume fractions, and (iii) to highlight how frictional contacts of coarse grains may play a role on the bulk yield stress of coarse-grained clay suspensions. We believe that this work would be useful for improving the rheological description of cohesive suspensions in geophysical and industrial applications. • Rheological measurements are performed on pure clay and coarse-grained clay suspensions. • The inclined blade vane allows to estimate the rheology of complex fluids containing grains. • The most appropriate models are provided to quantify the yield stress of suspensions. • The type of coarse materials may affect the bulk yield stress due to frictional contacts.

Data‐Driven Design of Wave‐Propagation Models for Shale‐Oil Reservoirs Based on Machine Learning

AbstractThe exploration and exploitation of shale oil is an important aspect in the oil industry. Seismic properties and well‐log data are essential to establish wave‐propagation models. Specifically, the description of wave dispersion and attenuation under complex geological conditions needs proper lithological and petrophysical information. This complex physical mechanism has to be considered if a traditional modeling approach is adopted. In this sense, machine learning (ML) techniques provide new possibilities for this purpose. We compare two deep‐neural‐network (DNN)‐based wave propagation models. In the first (pure data‐driven), a DNN is trained to connect seismic attributes, such as wave velocities, to multivariate functions of rock‐physics properties. By training DNNs with different initial parameters, the uncertainty of the proposed method can be quantified. The second method assumes the form of the wave equations. Then, the elastic constants of the constitutive relations are predicted by DNNs. The resulting dynamical equations describe the dispersion and attenuation and wavefield simulations can be performed to obtain more information. On the basis of a test, the two kinds of wave‐propagation models yield acceptable estimations of the seismic properties, with the second approach showing a broader application because the DNN is trained without S wave data. The methodologies illustrate that the new wave‐propagation model based on ML has high precision and can be general in terms of rheological description.

Rheology of two-dimensional granular chute flows at high inertial numbers

Contrary to the popular inertial number-based rheology of dense granular flows, recent studies suggest a non-monotonic variation of the effective friction coefficient μ(I) with the inertial number I in plane shear flows. While the popular rheology assuming monotonic variation of μ(I) with I suggests existence of an upper limit of inclination angle for steady chute flows, the non-monotonic variation suggests the possibility of two different flow states for chute flows at a given inclination angle. In this work, we perform DEM simulations of chute flow of frictional inelastic disks and show that steady, fully developed flows are possible at inclinations much higher than those predicted from the monotonic μ−I rheology. We observe steady flows up to inertial number I≈2 and find non-monotonic variation of the effective friction at high inertial numbers for chute flow of disks. The flows at high inertial numbers exhibit a constant density bulk region supported on top of a very dilute energetic basal layer of particles. We show that, in addition to a modified effective friction law that accounts for the non-monotonic variation of μ(I) and the dilatancy law relating the solids fraction ϕ with I, the rheological description also needs to account for the stress anisotropy by means of a normal stress difference law. By accounting for the presence of the normal stress difference, we also establish that only a single flow state is possible at any given inclination angle despite the non-monotonic variation of the effective friction coefficient.

Simulation of jet printing of solder paste for surface mounted technology

Purpose The purpose of this study is to propose a novel simulation framework and show that it captures the main effects of the deposition process, such as droplet shape, volume and speed. Design/methodology/approach In the framework, the time-dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two-phase system with the surrounding air being one phase and the dense suspension the other. The non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver; and LaStFEM, a large strain FEM solver. Experimental deposition was performed with a commercial jet printer and quantitative measurements were made with optical profilometry. Findings Jetting behaviour was shown to be affected by not only piston motion, fluid rheology and head deformation but also the viscous energy loss in the jetting head nozzle. The simulation results were compared to experimental data obtained from an industrial jetting head and found to match characteristic lengths, speed and volume within ca 10%. Research limitations/implications The simulations are based on a rheological description using the Carreau model that does not include a time-dependent relaxation of the fluid. This modelling approach limits the descriptive nature of the deposit after impact on the substrate. The simulation also adopts a continuum approach to the suspension, which will not accurately model the break-off of the droplet filament under the characteristic diameter of the particles in the suspension. Practical implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and minimised product development duration. Social implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and therefore an improvement from a sustainability perspective. The ability to plan deposition strategies virtually will also enable a decrease in consumables at manufacturers which will in turn decrease their carbon foot print. Originality/value While basic fluid dynamic simulations have been performed to simulate flow through nozzles, the ability to include both fluid-structure interaction and multiphase capability together with a more accurate rheological description of the suspension and with a substrate for surface mount applications has not been published to the knowledge of the authors.

Flow of cement slurry through an eccentric annulus

A step by step procedure has been developed to design cement hydraulic during cement jobto minimize non cemented channels or bad cement job by taking into consideration thenon-flow area throughout the eccentric annulus. Since cement slurry exhibit non-Newtonian rheological behavior, a good description of the slurry rheology is required inorder to estimate accurately the velocity profile across the annulus. To achieve this goal,six rheological models have been adopted: Power-law, Robertson-Stiff, Bingham, Casson,Modified Power-law, and Modified Robertson-Stiff Models. Using the last five rheologicalmodels, new frictional pressure gradient equations for laminar flow of cement slurrythrough an eccentric annulus have been derived by the author based on slit-approachapproximation.

Continuous rheological description of highly filled polymer melts for material extrusion

In additive manufacturing based on the material extrusion of filled polymer melts, a correct description of the rheological behaviour of the processed material is an important requirement. In case of highly filled feedstocks, complexities connected with a proper flow description are not only caused by the high packaging of powder particles (more than 50 vol.%) but also by the notable participation of polymer binder components in the quantification of shear viscosity. In this study, analytical expressions (master curves) of a true shear viscosity are developed to follow and continuously optimize the rheological dependence of the bulk feedstock on particular variables. A nickel-chromium-based compound (Inconel 718, content 59 vol.%) with thermoplastic binders of different molecular weight of polyethylene glycol was selected for the case study. The proposed master curves comprise simultaneously hitherto separately applied two corrections of an apparent shear viscosity: regarding the different capillary geometries with respect to entrance pressure and outlet extension, and determining an actual velocity profile based on shear rate distribution inside a feedstock. This approach eliminates the hitherto used non-Newtonian index, by means of which the logarithmic derivative was approximated. As the master curves depend exclusively on the shear rate and molecular weight of polyethylene glycol and do not involve any adjustable parameter, their application is straightforward. Their accuracy does not exceed experimental errors.

Insights into the rheology of cohesive granular media.

Characterization and prediction of the "flowability" of powders are of paramount importance in many industries. However, our understanding of the flow of powders like cement or flour is sparse compared to the flow of coarse, granular media like sand. The main difficulty arises because of the presence of adhesive forces between the grains, preventing smooth and continuous flows. Several tests are used in industrial contexts to probe and quantify the "flowability" of powders. However, they remain empirical and would benefit from a detailed study of the physics controlling flow dynamics. Here, we attempt to fill the gap by performing intensive discrete numerical simulations of cohesive grains flowing down an inclined plane. We show that, contrary to what is commonly perceived, the cohesive nature of the flow is not entirely controlled by the interparticle adhesion, but that stiffness and inelasticity of the grains also play a significant role. For the same adhesion, stiffer and less dissipative grains yield a less cohesive flow. This observation is rationalized by introducing the concept of a dynamic, "effective" adhesive force, a single parameter, which combines the effects of adhesion, elasticity, and dissipation. Based on this concept, a rheological description of the flow is proposed for the cohesive grains. Our results elucidate the physics controlling the flow of cohesive granular materials, which may help in designing new approaches to characterize the "flowability" of powders.

On the validity of the two-fluid-KTGF approach for dense gravity-driven granular flows as implemented in ANSYS Fluent R17.2

As a subproblem of solid transport in wellbores, we have investigated the cliff collapse problem by means of the Two-Fluid-Model (TFM), where the rheological description of the second phase (sand) is governed by the Kinetic Theory of Granular Flows (KTGF) and additional closures from soil mechanics for dense (frictional) regions of the solid phase. Using ANSYS Fluent R17.2, we have studied the influence of the aspect ratio and scale of the initial cliff, the scale of the particle size, four different interstitial fluids (air, water, and two viscous but shear-thinning solutions), and the role of the initial condition (IC) of the solid volume fraction. The latter was evaluated by two different strategies: (1) Let solids settle to establish a compacted granular bed in dynamic equilibrium prior to allow the cliff to collapse and (2) simply patch the solid volume fraction into the computational domain at t = 0.While most of the simulations produced a final deposit featuring a slope, validation with experimentally obtained scaling laws from the literature was not comprehensively successful. The primary reason identified is that, at steady-state, for which a sloped deposit must exist, a thin layer at the top of the sediment bed remains flowing, yielding a scale-dependent disintegration of the cliff over longer periods of time which ultimately results in a flat bed. We suspect this phenomenon, hereafter termed top bed velocity defect, to be a consequence of the numerical solutions strategy of Fluent which may result in some momentum solid flux imbalance at top-bed regions where the gradient of the solids kinetic/collisional pressure is high.Comprehensive model tuning is required to yield a better physical representation of the IC. In addition, alternative closures for both solid frictional pressure and solid viscosity may be helpful to better replicate the experimental data. On the other hand, experimental spread and missing experimental data for the shear-thinning fluids requires more comprehensive experimental data for validation purposes.If the model in its current form is used for transport modeling of cuttings in wellbore flows, the velocity defect will lead to an unknown overestimation of the mass flux of solids. When it comes to the modeling of dune migration, the top bed velocity defect will likely cause disintegration of the dune over longer periods of time.

Effect of couple stresses on the rheology and dynamics of linear Maxwell viscoelastic fluids

The constitutive analog of the linear Maxwell viscoelastic fluid model with the explicit addition of couple stresses is derived from thermodynamic first principles. Furthermore, the concepts of the recently proposed “Consistent Couple Stress theory” are considered to fully determine the rheological description of the fluid model. Finally, the resulting linear momentum equations are used to investigate the couple stress modulated flow dynamics of a few simple flow configurations. The plots of the variations in the elastic behavior of the fluid due to the presence of couple stresses show that the couple stress acts in addition to the conventional force-stress to increase the diffusion of momentum and thereby enhance the dampening of the elastic deformations in the equivalent spring-dashpot interpretation of the linear Maxwell viscoelastic fluid.

Towards unraveling the sintering process of two polystyrene particles by numerical simulations

In this work, we study different rheological and thermal phenomena present during laser sintering of two polystyrene (PS) particles using fully resolved numerical simulations. In our analysis, we varied the laser power, the initial temperature and the thermal convection coefficient, used different rheological descriptions for the flow behavior and in addition studied the effect of the substrate (used in the experiments) on the temperature distribution of the system. Although we are not able to fully describe the results of the experiments with our simulations for the given parameter set, we obtained important insights in the significance of thermal initial and boundary conditions by systematically studying the sintering process.