Berend van Wachem

Berend van Wachem
Otto-von-Guericke-Universität Magdeburg | OvGU · Institute for Process Engineering (IVT)

Doctor of Philosophy

About

195
Publications
35,745
Reads
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4,595
Citations
Introduction
The main research areas of Berend van Wachem are Fluid Mechanics, Multiphase Flow, Numerical Methods, Fluid Structure Interaction, Particle Technology, and Computational Fluid Dynamics.
Additional affiliations
October 2017 - present
Otto-von-Guericke-Universität Magdeburg
Position
  • Chair
Description
  • Professor
June 2008 - September 2017
Imperial College London
Position
  • Professor
Description
  • Professor of Multiphase Flows
Education
September 1990 - June 1995
Delft University of Technology
Field of study
  • Applied Physics

Publications

Publications (195)
Article
In this paper, we study the effects of the presence and shape of side walls and of the overall length of rotating cylindrical drums on the mixing of particles with differing sizes by application of the discrete element method (DEM). By varying the semi-axis of the spheroidally shaped side walls and the length of the overall drum, we observe the for...
Article
We present a physical model and a numerical method based on a space- and time-dependent Galilean-type coordinate transformation to simulate acoustic waves in the presence of an accelerating background flow field with sonic transition. Kinematically, the coordinate transformation is designed so as to maintain the well-posedness of the transformed wa...
Preprint
Full-text available
Many granular products have the shape of surface of revolution (SR), typical examples include round pharmaceutical tablets, shelled capsules and M\&M candies. Discrete Element Method (DEM) simulations are often applied to speed up the study of optimized design parameters along with experiments in the particle processing. For this purpose, a novel S...
Article
The particle proper orthogonal decomposition (PPOD) is demonstrated as a method for extraction of temporal statistical information on dispersed (discrete) phases of multiphase flows. PPOD is an extension of the classical Eulerian POD, differentiating itself by its Lagrangian formulation and applicability to discrete phases in both stationary and no...
Preprint
Full-text available
The capillary time-step constraint is the dominant limitation on the applicable time-step in many simulations of interfacial flows with surface tension and, consequently, governs the execution time of these simulations. We propose a fully-coupled pressure-based algorithm based on an algebraic Volume-of-Fluid (VOF) method in conjunction with an impl...
Article
Full-text available
The evolution of the capillary breakup of a liquid jet under large excitation amplitudes in a parameter regime relevant to inkjet printing is analysed using three-dimensional numerical simulations. The results exhibit a reversal of the breakup length of the jet occurring when the velocity scales associated with the excitation of the jet and surface...
Article
The capillary time-step constraint is the dominant limitation on the applicable time-step in many simulations of interfacial flows with surface tension and, consequently, governs the execution time of these simulations. We propose a fully-coupled pressure-based algorithm based on an algebraic Volume-of-Fluid (VOF) method in conjunction with an impl...
Preprint
Full-text available
We present an explicit finite difference time domain method to solve the lossless Westervelt equation for a moving wave emitting boundary in one dimension and in spherical symmetry. The approach is based on a coordinate transformation between a moving physical domain and a fixed computational domain. This allows to simulate the combined effects of...
Preprint
Full-text available
Volume conservation and shape preservation are two well-known issues related to the advection and remeshing in front tracking. To address these issues, this paper proposes a divergence-preserving velocity interpolation method and a parabolic fit vertex positioning method for remeshing operations for three-dimensional front tracking. Errors in prese...
Article
Full-text available
We present an explicit finite difference time domain method to solve the lossless Westervelt equation for a moving wave emitting boundary in one dimension and in spherical symmetry. The approach is based on a coordinate transformation between a moving physical domain and a fixed computational domain. This allows to simulate the combined effects of...
Article
Full-text available
Volume conservation and shape preservation are two well-known issues related to the advection and remeshing in front tracking. To address these issues, this paper proposes a divergence-preserving velocity interpolation method and a parabolic fit vertex positioning method for remeshing operations for three-dimensional front tracking. Errors in prese...
Article
In this work, a numerical model based on an algebraic Volume-of-Fluid (VOF) method and the Continuous Species Transfer (CST) model is presented to simulate the heating and evaporation of droplets composed of highly non-ideal mixtures. Regarding this, a non-ideal vapor-liquid equilibrium (VLE) model is coupled to the CST model to properly describe t...
Preprint
Full-text available
The majority of available numerical algorithms for interfacial two-phase flows either treat both fluid phases as incompressible (constant density) or treat both phases as compressible (variable density). This presents a limitation for the prediction of many two-phase flows, such as subsonic fuel injection, as treating both phases as compressible is...
Preprint
Full-text available
The local flow field and seepage induced drag obtained from Pore Network Models (PNM) is compared to Immersed Boundary Method (IBM) simulations, for a range of linear graded and bimodal samples. PNM were generated using a weighted Delaunay Tessellation (DT), along with the Modified Delaunay Tessellation (MDT) which considers the merging of tetrahed...
Preprint
Full-text available
The particle proper orthogonal decomposition (PPOD) is demonstrated on cases of particle flows in decaying homogeneous isotropic turbulence. Data is generated through one-way coupled simulations, where particle positions and velocities are integrated forward in time in a Lagrangian manner. The PPOD offers a direct way of extracting statistical info...
Article
Apoptosis, a key mechanism of programmed cell death, is triggered by caspase-3 protein and lowering its levels with gene therapy may rescue cell death after central nervous system damage. We developed a novel, non-viral gene therapy to block caspase-3 gene expression using small interfering RNA (siRNA) delivered by polybutylcyanoacrylate nanopartic...
Article
Full-text available
In the wake of the COVID-19 pandemic, an increased risk of infection by virus-containing aerosols indoors is assumed. Especially in schools, the duration of stay is long and the number of people in the rooms is large, increasing the risk of infection. This problem particularly affects schools without pre-installed ventilation systems that are equip...
Preprint
Full-text available
In the wake of the SARS-CoV-2 pandemic, an increased risk of infection by virus-containing aerosols indoors is assumed. Especially in schools, the duration of stay is long and the number of people in the rooms is large, increasing the risk of infection. This problem particularly affects schools without pre-installed ventilation systems that are equ...
Article
This work presents a consistent numerical model for the prediction of interfacial heat and mass transfer with high volume changes based on a single-field formulation and an algebraic Volume-of-Fluid (VOF) method. The model is based on the Continuous Species Transfer (CST) model for chemical species transport, and the compressive CICSAM scheme is us...
Article
This work presents a multiscale three-dimensional CFD model for the simulation of two-phase gas-liquid flows with different interface length scales, with focus on slug flow pattern. The model is based on the coupling of the Volume-of-Fluid (VOF) method, used to model the large-scale interface dynamics, and the Discrete Bubble Model (DBM) for modeli...
Article
The unexpectedly low cavitation inception threshold of water is widely attributed to the presence of cavitation nuclei either in the bulk water or attached to immersed surfaces. Being compressible, such objects are expected to respond to modest tensile stresses. Surprisingly, a large corpus of experiments shows that micro- and nanobubbles attached...
Article
Full-text available
de Seit der Gründung der Otto‐von‐Guericke‐Universität Magdeburg (OVGU) wurde der Forschungsbereich Verfahrenstechnik dort stetig ausgebaut. Heute umfasst die Fakultät für Verfahrens‐ und Systemtechnik der OVGU die vier Institute Verfahrenstechnik, Chemie, Strömungstechnik und Thermodynamik sowie Apparate‐ und Umwelttechnik. In diesem Beitrag stell...
Article
Full-text available
The asymmetric collapse of cavitation bubbles near a solid substrate generates large wall shear stresses, the precise magnitude of which is still not known with certainty. By comparing numerical simulations and experiments of a laser‐induced cavitation bubble near a solid substrate, we demonstrate that an accurate measurement of the pressure pulse...
Preprint
Full-text available
The particle-source-in-cell Euler-Lagrange (PSIC-EL) method is widely used to simulate flows laden with particles. Its accuracy, however, is known to deteriorate as the ratio between the particle diameter dp and the mesh spacing h increases, due to the impact of the momentum that is fed back to the flow by the Lagrangian particles. Although the com...
Article
Full-text available
In Lagrangian stochastic collision models, a fictitious particle is generated to act as a collision partner, with a velocity correlated to the velocity of the real colliding particle. However, most often, the fluid velocity seen by this fictitious particles is not accounted for in the generation of the fictitious particle velocity, leading to a de-...
Article
Full-text available
This paper addresses the two-way coupled Euler-Lagrange modelling of dilute particle-laden flows, with arbitrary particle-size to mesh-spacing ratio. Two-way coupled Euler-Lagrange methods classically require particles to be much smaller than the computational mesh cells for them to be accurately tracked. Particles that do not satisfy this requirem...
Article
Discrete element simulations of agglomerates impacting other agglomerates and agglomerates impacting a wall have been carried out. The agglomerates consist of multiple, small primary particles. In the simulations, we have varied the adhesiveness of the primary particles, the agglomerate size, as well as the impact velocity of the impact. The quanti...
Article
Full-text available
In the minutes immediately preceding the rupture of a soap bubble, distinctive and repeatable patterns can be observed. These quasistable transient structures are associated with the instabilities of the complex Marangoni flows on the curved thin film in the presence of a surfactant solution. Here, we report a generalized Cahn-Hilliard-Swift-Hohenb...
Chapter
In most industrial solid processing operations, the classification of particles is important and designed based on the terminal settling velocity as the main control parameter. This settling velocity is dependent on characteristic particle properties like size, density, and shape. Turbulent particle diffusion is the other key property controlling t...
Article
Operating a fluidized bed at elevated pressure is typically used to intensify processes. The effects of pressure on bubble behavior have been extensively studied; however, the gas flow distribution and particle dynamics are much less studied due to difficulties in measurement. In this work, CFD-DEM simulations are conducted to study hydrodynamics i...
Article
Full-text available
This paper proposes a height-function algorithm to estimate the curvature of two-dimensional curves and three-dimensional surfaces that are defined implicitly on two- and three-dimensional non-uniform Cartesian grids. It relies on the reconstruction of local heights, onto which polynomial height-functions are fitted. The algorithm produces curvatur...
Article
Full-text available
A fully coupled pressure-based algorithm and finite-volume framework for the simulation of the acoustic cavitation of bubbles in polytropic gas–liquid systems is proposed. The algorithm is based on a conservative finite-volume discretization with collocated variable arrangement, in which the discretized governing equations are solved in a single li...
Article
Full-text available
An experimental study is conducted on a pilot-scale zigzag air separator (ZZS) to study the effects of varying the solid feed mass stream, the mean channel air velocity, and the number of channel segments onto the grade efficiency. Spherical glass beads are classified. A straight pipe separator model (PSM) is modified for the ZZS and fitted to the...
Preprint
A conservative finite-volume framework, based on a collocated variable arrangement, for the simulation of flows at all speeds, applicable to incompressible, ideal-gas and real-gas fluids is proposed in conjunction with a fully-coupled pressure-based algorithm. The applied conservative discretisation and implementation of the governing conservation...
Article
Full-text available
A conservative finite-volume framework, based on a collocated variable arrangement, for the simulation of flows at all speeds, applicable to incompressible, ideal-gas and real-gas fluids is proposed in conjunction with a fully-coupled pressure-based algorithm. The applied conservative discretisation and implementation of the governing conservation...
Article
Fundamental numerical studies of seepage induced geotechnical instabilities and filtration processes depends on accurate prediction of the forces imparted on the soil grains by the permeating fluid. Hitherto coupled Discrete Element Method (DEM) simulations documented in geomechanics have most often simulated the fluid flow using computational flui...
Article
Minor changes in the composition of poloxamer 188-modified, DEAE-dextran-stabilized (PDD) polybutylcyanoacrylate (PBCA) nanoparticles (NPs), by way of altering the physicochemical parameters (such as size or surface charge), can substantially influence their delivery kinetics across the blood-retina barrier (BRB) in vivo. We now investigated the ph...
Article
The coefficient of restitution and contact duration of the impact of bronze, brass and steel spheres on large (extended in length and width) glass plates have been determined experimentally. The results clearly exhibit different amounts of energy dissipation mainly due to plastic deformation of the spheres and bending of the plate. Influence of the...
Article
Full-text available
This paper focuses on the effect of ultra-fine ( d < 10 µm) powders in mixtures with fine ( d < 100 µm) bulk material on compression processes and also evaluates the re-fluidization behavior of the compressed bed (history effect). Achieving this goal, different mixtures of fine and ultra-fine Ground-Carbonate-Calcium were compressed at three pressu...
Preprint
The interaction of a shock wave with a bubble features in many engineering and emerging technological applications, and has been used widely to test new numerical methods for compressible interfacial flows. Recently, density-based algorithms with pressure-correction methods as well as fully-coupled pressure-based algorithms have been established as...
Article
Most interfacial flows of practical interest typically involve length- and time-scales that span over several orders of magnitude. Their accurate modelling, using interface-capturing or interface-tracking methods, therefore presents a prohibitively large computational cost. Over the past few years, hybrid Eulerian- Lagrangian approaches have been p...
Article
Full-text available
A numerical study for a supersonic underexpanded argon gas jet driven by a pressure ratio of 120 is described in this work, and the results are compared to experiments. A single phase large-eddy simulation (LES) employing a fully-coupled pressure-based finite volume solver framework is carried out. The numerical results are validated against experi...
Article
Full-text available
The interaction of a shock wave with a bubble features in many engineering and emerging technological applications, and has been used widely to test new numerical methods for compressible interfacial flows. Recently, density-based algorithms with pressure-correction methods as well as fully-coupled pressure-based algorithms have been established as...
Conference Paper
The majority of available numerical algorithms for interfacial two-phase flows either treat both fluid phases as incompressible (constant density) or treat both phases as compressible (variable density). This presents a limitation for the prediction of many two-phase flows, such as subsonic fuel injection, as treating both phases as compressible is...
Preprint
Full-text available
In the minutes immediately preceeding the rupture of a soap bubble, distinctive and repeatable patterns can be observed. These quasi-stable transient structures are associated with the instabilities of the complex Marangoni flows on the curved thin film in the presence of a surfactant solution. Here, we report a generalised Cahn-Hilliard-Swift-Hohe...
Article
The local flow field and seepage induced drag obtained from Pore Network Models (PNM) is compared to Immersed Boundary Method (IBM) simulations, for a range of linear graded and bimodal samples. PNM were generated using a weighted Delaunay Tessellation (DT), along with the Modified Delaunay Tessellation (MDT) which considers the merging of tetrahed...
Article
Full-text available
This paper investigates the numerical simulation of Corium spreading, focussing on modelling the two fluid Corium/air system. The complex Corium spreading flow is simplified by assuming the Corium is a homogeneous non-reactive fluid with a strongly temperature-dependent viscosity. A detailed investigation of the numerical methods most suitable to s...
Article
Full-text available
The immersed boundary method (IBM) is a well-suited tool for the direct numerical simulation of flows with dense particle suspensions, which feature strong and complex flow-particle and particle–particle interactions. With the aim to model such flows, this paper proposes to extend the Regularised Discrete Momentum Forcing (RDMF-) IBM of Abdol Azis...
Article
Full-text available
The effect of the presence of ultra-fines (d < 10 μm) on the fluidization of a bed containing fine particles (d < 100 μm), is the subject of this paper. Practically, it can happen due to breakage or surface abrasion of the fine particles in some processes which totally changes the size distribution and also fluidization behaviour. The materials use...
Article
Full-text available
We report on detailed and systematic experiments of thin liquid films flowing as a result of the action of gravity under an inverted planar substrate. A measurement technique based on planar laser-induced fluorescence (PLIF) was developed and applied to a range of such flows in order to provide detailed space- and time-resolved film-height informat...
Article
This paper presents an immersed boundary method (IBM) to model the behaviour of solid-fluid interfaces in incompressible flows on non-conforming, unstructured meshes. Based on a smooth-interface direct forcing formulation, the proposed forcing method directly and implicitly uses the discretised momentum equations to evaluate the source terms requir...
Article
The present study aims to validate CFD–DEM (Discrete Element Method) simulations of bubbling fluidized beds comprehensively, based on the small scale “challenge” problem recently released by NETL (https://mfix.netl.doe.gov/). Both the averaged and fluctuated values of an extensive list of properties are evaluated, including the pressure drop, the b...
Article
Because the blood-brain barrier (BBB) is an obstacle for drug-delivery, carrier systems such as polybutylcyanoacrylate (PBCA) nanoparticles (NPs) have been studied. Yet, little is known of how physiochemical features such as size, surfactants and surface charge influence BBB passage in vivo. We now used a rat model of in vivo imaging of the retina...
Article
Full-text available
This article describes experiments to investigate the fluid-to-wall interaction downstream of a highly underexpanded jet, with a pressure ratio of 120, confined in a channel. Heat transfer induced by Joule-Thomson cooling, which is a real gas effect in such a configuration, has critical implications on the safety of pressurised gas components. This...
Article
Full-text available
Superparamagnetic iron oxide nanoparticles (SPIO-NPs) have great potential to be used in different pharmaceutical applications, due to their unique and versatile physical and chemical properties. The aim of this study was to quantify in vitro cytotoxicity of dextran 70,000-coated SPIO-NPs labelled/unlabelled with rhodamine 123, in C6 glioma cells a...
Article
Full-text available
A multicamera shadow imaging (shadowgraphy) system is developed to simultaneously capture particle dynamics at multiple locations inside a so called zigzag air separator which is used for separating fine from coarse particle fractions. The adaption of the shadowgraphy system to the specific requirements of the separator apparatus to measure particl...
Article
The following article presents an overview of two measurement techniques for determining the coefficient of restitution (CoR) of multiple impacts of granules on a rigid plate. Experiments were performed with two different kinds of granules, which were dropped freely on an impact plate starting from a defined height. The impacts were recorded by an...
Conference Paper
Summary: A new technique developed by the authors and referred to as thermographic laser Doppler velocimetry (with the phosphor BaMgAl10O17:Eu2+ selected as tracer particles) was used to measure flow temperature and velocity simultaneously in a boundary layer over a heated plate. Accurate measurements as close as 200 µm from the surface was obtaine...
Conference Paper
Full-text available
We employ planar laser-induced fluorescence (PLIF), particle tracking velocimetry (PTV) and infrared thermography (IR) towards the detailed investigation of the flow and heat transfer phenomena underlying harmonically-excited, gravity-driven film flows falling over an inclined, electrically-heated substrate. PLIF is used to generate space and time-...
Article
Full-text available
Momentum-weighted interpolation (MWI) is a widely used discretisation method to prevent pressure–velocity decoupling in simulations of incompressible and low Mach number flows on meshes with a collocated variable arrangement. Despite its popularity, a unified and consistent formulation of the MWI is not available at present. In this work, a discret...