
Patrick David AndersonEindhoven University of Technology | TUE · Department of Mechanical Engineering
Patrick David Anderson
Professor
About
317
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Introduction
Patrick Anderson is professor in structure and rheology of complex fluids. He studied Applied Mathematics and received his Ph.D. degree from the Department of Mechanical Engineering at the same university with Prof. Han Meijer as his advisor. Following a year break at Océ Technologies he joined the Polymer Technology group.
His present interests include structure development during flow, interfacial phenomena, rheology, microfluidics, additive manufacturing and polymer processing.
Additional affiliations
April 2000 - present
Education
April 1995 - June 1999
Publications
Publications (317)
In lab-on-chip devices, on which complete (bio-)chemical analysis laboratories are miniaturized and integrated, it is essential to manipulate fluids in sub-millimetre channels and sub-microlitre chambers. A special challenge in these small micro-fluidic systems is to create good mixing flows, since it is almost impossible to generate turbulence. We...
The effect of insoluble surfactants on drop deformation and breakup in simple shear flow is studied using a combination of a three-dimensional boundary-integral method and a finite-volume method to solve the coupled fluid dynamics and surfactant transport problem over the evolving interface. The interfacial tension depends nonlinearly on the surfac...
A proper description of coalescence of viscous drops is challenging from an experimental, numerical, and theoretical point of view. Although the problem seems easy at first sight, consensus in the literature has still not been reached on how to predict a realistic coalescence rate given flow type, capillary number and viscosity ratio. Despite advan...
The performance of industrially relevant static mixers that work via chaotic advection in the Stokes regime for highly viscous fluids, flowing at low Reynolds numbers, like the Kenics, the Ross Low-Pressure Drop (LPD) and Low-Low-Pressure Drop (LLPD), the standard Sulzer SMX, and the recently developed new design series of the SMX, denoted as SMX(n...
Fluid-fluid interfaces, laden with polymers, particles or other surface-active moieties, often show a rheologically complex response to deformations, in particular when strong lateral interactions are present between these moieties. The response of the interface can then no longer be described by an isotropic surface tension alone. These “structure...
In this study, we experimentally investigate the fiber orientation kinetics and rheology of fiber-filled polymer melts in shear flow. A novel setup is designed with custom-built bottom and top geometries that are mounted on a conventional rotational rheometer. Shear flow between parallel sliding plates is applied by vertical movement of the top geo...
The role of permittivity mismatch and of individual layer thickness on the electromagnetic interference (EMI) shielding performance of lossy dielectric polymer nanocomposite multilayer shields is explored via a combined theoretical and experimental approach. The A-B multilayer shields comprise of two or more alternating layers of low and high permi...
This study explores the novel approach of interface-crystallization-induced compatibilization (ICIC) via stereocomplexation as a promising method to improve the interfacial strength in thermodynamically immiscible polymers. Herein, two distinct reactive interfacial compatibilizers, poly(styrene-co-glycidyl methacrylate)-graft-poly(l-lactic acid) (S...
During processing of fiber composites, the fiber-induced stresses influence the local flow fields, which, in turn, influence the stress distribution and the fiber orientation. Therefore, it is crucial to be able to predict the rheology of fiber-filled polymer composites. In this study, we investigate the fiber orientation kinetics and rheological p...
The demand for fiber-filled polymers has witnessed a significant upswing in recent years. A comprehensive understanding of the local fiber orientation is imperative to accurately predict the mechanical properties of fiber-filled products. In this study, we experimentally investigated the fiber orientation kinetics in uniaxial extensional flows. For...
Fiber-reinforced polymer composites are largely employed for their improved strength with respect to unfilled matrices. Considering semi-crystalline materials under relevant processing conditions, the applied pressure and flow induce shear stresses at the fiber–polymer interface. These stresses may strongly enhance the nucleation ability of the fib...
External gear pumps are used in fluid transport systems because of their tight clearances and accurate flow control. These tight clearances are a challenge for numerical studies in terms of spatial discretization. In earlier work, the flow of a viscous fluid in an external gear pump is computed using the finite element method (FEM). An element size...
For suspensions with electromagnetic particles exposed to an external field, we examine the effect of the solidification of the suspending medium on the formation of particle structures, representative of the curing of a photo-reactive resin during stereolithography. To that end, Brownian Dynamics (BD) simulations are examined in which the solidifi...
Front Cover: The disperse polymer blend morphology evolution is described using a macroscopic model, which clusters individual droplets in droplet populations. The blend model is used to perform a particle tracking simulation of the morphology evolution inside a twin‐screw extruder. The figure shows the size distribution of 1300 droplet populations...
In an extrusion process, an external gear pump can be used to control the flow rate of the system. When extruding polymers, the viscosity is quite high, resulting in negligible inertia and thus laminar flow. The external gear pump contains two gears, one driven by a motor and one driven by means of contact with the other gear. In our previous work,...
The blend morphology model developed by Wong et al., based on Peters et al., is used to investigate the development of the disperse polymer blend morphology in twin‐screw extruder flow. First, the model is written in a point‐wise form suitable for using in conjunction with particle tracking. Particle tracking methods are used to generate trajectori...
Magnetic microbeads have been widely used for the capturing of biomarkers, as well as for microfluidic mixing for point-of-care diagnostics. In magnetic micromixing, microbead motion is generated by external electromagnets, inducing fluid kinetics, and consequently mixing. Here, we utilize an in-plane rotating magnetic field to induce magnetic bead...
The microstructure of products manufactured by selective laser sintering (SLS) is known to be highly dependent on various process and material parameters. The latter thus also affect the final part properties. While most work has focused on ex-situ characterization of the printed parts, little is known about the time-dependent microstructure develo...
A framework is presented for the formulation of a class of continuum constitutive models for sharp interfaces with non-linear viscoelastic behaviour due to a considerable isotropic interfacial microstructure. For the formulation of a thermodynamically consistent elastoviscoplastic interface constitutive model we adapt an approach successful in desc...
Profile extrusion is a production technique to make polymer profiles and hollow tubes. At a certain distance after the die exit the polymer extrudate is guided into a cooling chamber, where the polymer is cooled extensively to set the part dimensions. Uniform cooling in the cooling chamber is required to avoid warpage and twisting of the extrudate...
The extrusion of highly filled elastomers is widely used in the automotive industry. In this paper, we numerically study the effect of thixotropy on 2D planar extrudate swell for constant and fluctuating flow rates, as well as the effect of thixotropy on the swell behavior of a 3D rectangular extrudate for a constant flowrate. To this end, we used...
The effect of time-dependent external fields on the structures formed by particles with induced dipoles dispersed in a viscous fluid is investigated by means of Brownian Dynamics simulations. The physical effects accounted for are thermal fluctuations, dipole-dipole and excluded volume interactions. The emerging structures are characterised in term...
In this paper, an experimental strategy is presented to characterize the rheological behavior of filled, uncured rubber compounds. Oscillatory shear experiments on a regular plate-plate rheometer are combined with a phenomenological thixotropy model to obtain model parameters that can be used to describe the steady shear behavior. We compare rate-...
Filament stretching rheometry is a prominent experimental method to determine rheological properties in extensional flow whereby the separating plates determine the extension rate. In literature, several correction factors that can compensate for the errors introduced by the shear contribution near the plates have been introduced and validated in t...
An external gear pump is a relatively simple and inexpensive pump, that is used in a variety of production systems. Numerous works have studied the external gear pump using numerical simulations, however the fluids typically have a low viscosity and its flow is turbulent. previous work focused on predicting the output fluctuation and the volumetric...
In this paper we study the numerical stability of four positive (semi-)definite formulations for viscoelastic fluid flows: the LCR formulation of Fattal and Kupferman (2004), the Cholesky-log formulation of Vaithianathan and Collins (2003), the b-symmetric formulation of Balci et al. (2011) and the CDT formulation of Carrozza et al. (2019). The num...
In this work we describe the production of spherical polymer particles from thermoplastic polymers. A simple method is developed to transform rough powders into spherical particles. The polymer particles are molten in heated oil whereafter interfacial tension driven reduction of curvature and shape retraction induce a transformation to the equilibr...
Significance
Dispensing of viscoelastic fluids is common in applications like electronic packaging, food engineering, and additive manufacturing. However, viscoelasticity leads to problems like slow liquid bridge breakup, stringiness, and satellite droplets generation. By high-speed imaging and numerical simulation, we show that torsion can break s...
The structure formation of particles with induced dipoles dispersed in a viscous fluid, under a spatially and temporarily uniform external electric or magnetic field, is investigated by means of Brownian Dynamics simulations. Dipole–dipole interactions forces, excluded volume forces and thermal fluctuations are accounted for. The resulting structur...
We investigate the flow of viscous interfaces carrying an insoluble surface active material, using numerical methods to shed light on the complex interplay between Marangoni stresses, compressibility, and surface shear and dilatational viscosities. We find quantitative relations between the drag on a particle and interfacial properties as they are...
Short liquid bridges are stable under the action of surface tension. In applications like electronic packaging, food engineering and additive manufacturing, this poses challenges to the clean and fast dispensing of viscoelastic fluids. Here, we investigate how short viscoelastic liquid bridges can be destabilized by torsion. We consider a setup con...
The blend morphology model developed by Wong et al. (Rheologica Acta, 2019), based on Peters et al. (J Rheol 45(3):659–689, 2001), is used to investigate the development of the polydispersity of the disperse polymer blend morphology in complex flow. First, the model is extended with additional morphological states. The extended model is tested for...
In this paper we propose a novel approach to solve the inverse problem of three-dimensional die design for extrudate swell, using a real-time active control scheme. To this end, we envisioned a feedback connection between the corner-line finite element method, used to predict the positions of the free surfaces of the extrudate, and the controller....
Complex fluid-fluid interfaces determine for a large part the macroscopic material properties of foams and emulsions that appear in applications such as food, materials processing and consumer care products. As a step towards predicting these properties, a 2D axisymmetric and a 3D finite element model have been developed for simulating the dynamics...
department of mechanical engineering www.tue.nl/pt Compared with droplet-matrix morphologies, the co-continuous morphology provides synergistic mechanical and electrical properties. One of the challenges with immiscible polymer blends is that the morphologies generated during mixing are usually in a non-equilibrium state and tend to coarsen. Theref...
Introduction In 'selective laser sintering', products are made layer-by-layer using polymer powder as building material. A laser beam selectively melts the powder to form the desired objects. To study the effect of the processing conditions on the material properties of the final products, we developed a detailed computational model of the fabricat...
Gear pumps are frequently used for the transport of high-viscosity fluids, for instance, for the extrusion of polymers. The flow rate of this extrusion process is regularly controlled by an external gear pump. In this work, the 2D flow of a viscous fluid through such an external gear pump is studied using the finite element method. Local mesh refin...
A 2D hysteretic Discrete Element Method (DEM) model is developed for simulating the flow of food particles, specifically with multi-material 3D food printing processes in mind. Particles are modeled as arbitrarily shaped polygons due to the diverse nature of food powders, which can be highly irregular in shape. The developed hys-teretic force model...
A finite element model is presented to describe the flow, resulting stresses and crystal-lization in a filament stretching extensional rheometer (FiSER). This model incorporates nonlinear viscoelasticity, nonisothermal processes due to heat release originating from crystallization and viscous dissipation as well as the effect of crystallization on...
In the area of polymer crystallization, the most widely used techniques to quantify structure, morphology and molecular orientation are fundamentally based on light or X‐ray scattering and absorption. In particular, synchrotron X‐rays are used for detailed studies on the semicrystalline structure in polymeric materials. The technical requirements f...
We present a rheometer that combines the possibility to perform in situ X-ray experiments with a precise and locally controlled uniaxial extensional flow. It thus allows us to study the crystallization kinetics and morphology evolution combined with the rheological response to the applied flow field. A constant uniaxial deformation rate is ensured,...
A methodology for the characterization of particle structures, especially networks, is developed. This scheme combines 3D image analysis techniques with graph theory tools for the simplification of a structure of thick agglomerates to its skeleton. The connectivity graph of the initial structure is compared with the one of the corresponding skeleto...
A 3D transient non-isothermal finite element code is developed to predict the extrudate shape of viscoelastic fluids emerging from an asymmetric keyhole shaped die. The corner-line method is used to model the movement of the free surfaces. The code is tested using two benchmark problems. First the corner-line method is tested using a trumpet shaped...
The effect of plastic deformation on the molecular dynamics of atactic polystyrene (a-PS) was studied by broadband dielectric relaxation spectroscopy (BDRS), Fourier-transform infrared spectroscopy (FTIR) and
above its glass-transition temperature, resulting in thermal rejuvenation. Cold rolling revealed, in addition to the known a- and g (I)-relax...
Criteria to identify transitions between dynamic self-similar linear thinning regimes of liquid bridges are of utmost importance in order to accurately interpret results in capillary break-up rheometry. Currently available criteria encompass many experimental difficulties or rely on numerical approaches. Here, we introduce a different set of nondim...
Fluctuating viscoelasticity for conformation-tensor-based models is studied at equilibrium, in simple-shear deformation, and in uniaxial extension. The models studied are the upper-convected Maxwell model, the FENE-P model with finite chain-extensibility, and the Giesekus model with anisotropic drag. Using numerical simulations, the models are comp...
The response of uniaxial and biaxial anisotropic polypropylene is discussed. A 3D elasto‐viscoplastic constitutive model is developed to account for material anisotropy. The famous Hill’s anisotropic yield criterion is combined with the Eyring relation and implemented in a finite element framework to model the response of the polymer during uniaxia...
In the selective laser sintering of polymers, the most widely used powders are based on polyamide 12 (PA12), which is a semi-crystalline polymer. Because the mechanical properties of the printed parts depend largely on the microstructure, knowledge on the crystalline architecture is important. We developed a numerical model based on the finite elem...
We present a unique laser sintering setup that allows real time studies of the structural evolution during laser sintering of polymer particles. The device incorporates the main features of classical selective laser sintering machines for 3D printing of polymers and at the same time allows in situ visualization of the sintering dynamics with optica...
Gear pumps are often used for the transport of high viscosity fluids, for example in the production of car tires. In the extrusion process of the tire compounds, the flow rate is controlled by an external gear pump. The flow of a fluid through the pump is numerically studied using the finite element method.
Selective laser sintering (SLS) is an important additive manufacturing method for polymers and is increasingly used for industrial applications. To improve the quality of printed products a thorough understanding of the process is necessary. Simulations are a convenient way to assess the sintering in detail. In literature several numerical studies...
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...
Conclusions The rheological response measured with our rheometer for LDPE is in agreement with the linear viscoelasticity (LVE) and data from commercial devices. Furthermore the results of the in-situ X-ray experiments demonstrate that the crystallization kinetics, and the evolution of crystal structure and morphology, during and after uniaxial ext...
Microfluidic mixing becomes a necessity when thorough sample homogenization is required in small volumes of fluid, such as in lab-on-a-chip devices. For example, efficient mixing is extraordinarily challenging in capillary-filling microfluidic devices and in microchambers with stagnant fluids. To address this issue, specifically designed geometrica...
We aim to investigate the influence of interfacial rheology on the time-dependent deformation and orientation of a Newtonian drop suspended in a Newtonian matrix subjected to simple shear flow. Our numerical model for simulating general two-phase incompressible flow will be verified and validated with convergence tests and by comparison with litera...
During the lifetime of polycarbonate surfaces, which for example are used as helmets or protective eye visors, friction and abrasive wear may result from scratching or sliding cycles. Previous research showed that it is essential to understand the intrinsic mechanical response of the polymer in order to further investigate its frictional and wear r...