Imperial College London

Professor Berend Van Wachem

Faculty of EngineeringDepartment of Mechanical Engineering

Visiting Professor
 
 
 
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Contact

 

+44 (0)20 7594 7030b.van-wachem

 
 
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Location

 

622City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

184 results found

Tawfik M, Zhang X, Grigartzik L, Heiduschka P, Hintz W, Henrich-Noack P, van Wachem B, Sabel BAet al., 2021, Gene therapy with caspase-3 small interfering RNA-nanoparticles is neuroprotective after optic nerve damage, NEURAL REGENERATION RESEARCH, Vol: 16, Pages: 2534-+, ISSN: 1673-5374

Journal article

Denner F, Evrard F, Castrejon-Pita AA, Castrejon-Pita JR, van Wachem Bet al., 2021, Reversal and Inversion of Capillary Jet Breakup at Large Excitation Amplitudes, FLOW TURBULENCE AND COMBUSTION, ISSN: 1386-6184

Journal article

Cerqueira RFL, Paladino EE, Evrard F, Denner F, van Wachem Bet al., 2021, Multiscale modeling and validation of the flow around Taylor bubbles surrounded with small dispersed bubbles using a coupled VOF-DBM approach, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, Vol: 141, ISSN: 0301-9322

Journal article

Ren Z, Liu S, Tan BH, Denner F, Evrard F, van Wachem B, Zuo Z, Ohl C-Det al., 2021, Strong shear flows release gaseous nuclei from surface micro- and nanobubbles, PHYSICAL REVIEW FLUIDS, Vol: 6, ISSN: 2469-990X

Journal article

Reichl U, Seidel-Morgenstern A, Sundmacher K, Tsotsas E, van Wachem Bet al., 2021, Research at the institute of process engineering at Otto von Guericke University Magdeburg, Chemie Ingenieur Technik - CIT, Vol: 93, Pages: 345-352, ISSN: 0009-286X

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 stellen die fünf Lehrstühle des Instituts für Verfahrenstechnik (Bioprozesstechnik, Chemische Verfahrenstechnik, Systemverfahrenstechnik, Thermische Verfahrenstechnik und Mechanische Verfahrenstechnik) ihre Forschungsaktivitäten anhand ausgewählter Projekte vor.

Journal article

Evrard F, Denner F, van Wachem B, 2021, Quantifying the errors of the particle-source-in-cell Euler-Lagrange method, International Journal of Multiphase Flow, Vol: 135, Pages: 1-6, ISSN: 0301-9322

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 ( d p ) 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 community typically recommends particle diameters to be at least an order of magnitude smaller than the mesh spacing, the errors corresponding to a given d p /h ratio and/or flow regime have not been systematically studied. In this paper, we provide an expression to estimate the magnitude of the flow velocity disturbance resulting from the transport of a particle in the PSIC-EL framework, based on the d p /h ratio and the particle Reynolds number, Re p . This, in turn, directly relates to the error in the estimation of the undisturbed velocity, and therefore to the error in the prediction of the particle motion. We show that the upper bound of the relative error in the estimation of the undisturbed velocity, for all particle Reynolds numbers, is approximated by (6 / 5 ) d p /h . Moreover, for all cases where d p /h 1 / 2 , the expression we provide accurately estimates the value of the errors across a range of particle Reynolds numbers that are relevant to most gas-solid flow applications ( Re p < 500 ).

Journal article

van Wachem B, Thalberg K, Duy N, de Juan LM, Remmelgas J, Niklasson-Bjorn Iet al., 2020, Analysis, modelling and simulation of the fragmentation of agglomerates, CHEMICAL ENGINEERING SCIENCE, Vol: 227, ISSN: 0009-2509

Journal article

Evrard F, Denner F, van Wachem B, 2020, Euler-Lagrange modelling of dilute particle-laden flows with arbitrary particle-size to mesh-spacing ratio, Journal of Computational Physics: X, Vol: 8

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 requirement can be considered by introducing a source term regularisation operator that typically consists in convoluting the point-wise particle momentum sources with a smooth kernel. Particles that are larger than the mesh cells, however, generate a significant local flow disturbance, which, in turn, results in poor estimates of the fluid forces acting on them. To circumvent this issue, this paper proposes a new framework to recover the local undisturbed velocity at the location of a given particle, that is the local flow velocity from which the disturbance due to the presence of the particle is subtracted. It relies upon the solution of the Stokes flow through a regularised momentum source and is extended to finite Reynolds numbers based on the Oseen flow solution. Owing to the polynomial nature of the regularisation kernel considered in this paper, a correction for the averaged local flow disturbance can be analytically derived, allowing to filter out scales of the flow motion that are smaller than the particle, which should not be taken into account to compute the interaction/drag forces acting on the particle. The proposed correction scheme is applied to the simulation of a particle settling under the influence of gravity, for varying particle-size to mesh-spacing ratios and varying Reynolds numbers. The method is shown to nearly eliminate any impact of the underlying mesh resolution on the modelling of a particle's trajectory. Finally, optimal values for the scale of the regularisation kernel are provided and their impact on the flow is discussed.

Journal article

Liu D, Song J, Ma J, Chen X, van Wachem Bet al., 2020, Gas flow distribution and solid dynamics in a thin rectangular pressurized fluidized bed using CFD-DEM simulation, POWDER TECHNOLOGY, Vol: 373, Pages: 369-383, ISSN: 0032-5910

Journal article

Shen L, Denner F, Morgan N, Van Wachem B, Dini Det al., 2020, Transient structures in rupturing thin-films: Marangoni-induced symmetry-breaking pattern formation in viscous fluids, Science Advances, Vol: 6, ISSN: 2375-2548

In the minutes immediately preceeding the rupture of a soap bubble,distinctive and repeatable patterns can be observed. These quasi-stabletransient structures are associated with the instabilities of the complexMarangoni flows on the curved thin film in the presence of a surfactantsolution. Here, we report a generalised Cahn-Hilliard-Swift-Hohenberg modelderived using asymptotic theory which describes the quasi-elastic wrinklingpattern formation and the consequent coarsening dynamics in a curvedsurfactant-laden thin film. By testing the theory against experiments on soapbubbles, we find quantitative agreement with the analytical predictions of thenucleation and the early coarsening phases associated with the patterns. Ourfindings provide fundamental physical understanding that can be used to(de-)stabilise thin films in the presence of surfactants and have importantimplications for both natural and industrial contexts, such as the productionof thin coating films, foams, emulsions and sprays.

Journal article

Evrard F, Denner F, van Wachem B, 2020, Height-function curvature estimation with arbitrary order on non-uniform Cartesian grids, Journal of Computational Physics: X, Vol: 7

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 curvature estimates of order N−1 anywhere in a stencil of (N+1)d−1 heights computed from the volume-fraction data available on a d-dimensional non-uniform Cartesian grid. These estimates are of order N at the centre of the stencil when it is symmetric about its main axis. This is confirmed by a comprehensive convergence analysis conducted on the errors associated with the application of the algorithm to a fabricated test-curve and test-surface.

Journal article

Denner F, Evrard F, van Wachem B, 2020, Modeling Acoustic Cavitation Using a Pressure-Based Algorithm for Polytropic Fluids, FLUIDS, Vol: 5

Journal article

Lukas E, Roloff C, van Wachem B, Thévenin Det al., 2020, Experimental investigation of the grade efficiency of a zigzag separator, Powder Technology, Vol: 369, Pages: 38-52, ISSN: 0032-5910

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 experimental data to estimate the relative cut-point settling velocity, the separation sharpness, the relative rise velocity, the diffusion coefficient, and the particle loading. The proposed model is thoroughly investigated with regard to all important parameters, e.g. the estimated particle loading is shown to be more precise than the ratio of the solid and air mass stream, used in many publications. Finally, the relative rise velocity is shown to be only a function of the particle loading, making the experimental results within the model collapse.

Journal article

Denner F, Evrard F, van Wachem BGM, 2020, Conservative finite-volume framework and pressure-based algorithm for flows of incompressible, ideal-gas and real-gas fluids at all speeds, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 409, ISSN: 0021-9991

Journal article

van Wachem B, Curran T, Evrard F, 2020, Fully Correlated Stochastic Inter-Particle Collision Model for Euler-Lagrange Gas-Solid Flows, FLOW TURBULENCE AND COMBUSTION, Vol: 105, Pages: 935-963, ISSN: 1386-6184

Journal article

Lukas E, Roloff C, Mann H, Kerst K, Hagemeier T, Van Wachem B, Thévenin D, Tomas Jet al., 2020, Experimental study and modelling of particle behaviour in a multi-stage zigzag air classifier, Dynamic Flowsheet Simulation of Solids Processes, Pages: 391-410, ISBN: 9783030451677

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 the efficiency of the separation. In this project, multi-stage separation experiments of a variety ofmaterials have been performed using different flow velocities, mass loadings of the air, number of stages. Separation has been investigated separately concerning particle size, particle density, and particle shape. Continuous operation in terms of solid material and airflow has been mostly considered. However, variations in mass loading and pulsating operation of the fan have been investigated as well. The performance has been analyzed and discussed with respect to the separation functions, for instance regarding separation sharpness. Severalmodelling approaches have been checked and/or developed to describe theoretically the corresponding observations. After fitting the free model parameters, a very good agreement has been obtained compared to experimental measurements. Finally, the reduced model has been implemented into the central software DYSSOL.

Book chapter

Knight C, O'Sullivan C, Dini D, Van Wachem Bet al., 2020, Computing drag and interactions between fluid and polydisperse particles in saturated granular materials, Computers and Geotechnics, Vol: 117, Pages: 1-16, ISSN: 0266-352X

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 fluid dynamics (CFD) models employing fluid cells that contain a number of particles. Empirical drag models are used to predict the fluid-particle interaction forces using the flow Reynolds number and fluid cell porosity. Experimental verification of the forces predicted by these models at the particle-scale is non-trivial. This contribution uses a high resolution immersed boundary method to model the fluid flow within individual voids in polydisperse samples of spheres to accurately determine the fluid-particle interaction forces. The existing drag models are shown to poorly capture the forces on individual particles in the samples for flow with low Reynolds number values. An alternative approach is proposed in which a radical Voronoi tesselation is applied to estimate a local solids volume fraction for each particle; this local solids fraction can be adopted in combination with existing expressions to estimate the drag force. This tessellation-based approach gives a more accurate prediction of the fluid particle interaction forces.

Journal article

You Q, Sokolov M, Grigartzik L, Hintz W, van Wachem BGM, Henrich-Noack P, Sabel BAet al., 2019, How Nanoparticle Physicochemical Parameters Affect Drug Delivery to Cells in the Retina via Systemic Interactions, MOLECULAR PHARMACEUTICS, Vol: 16, Pages: 5068-5075, ISSN: 1543-8384

Journal article

Denner F, van Wachem BGM, 2019, Numerical modelling of shock-bubble interactions using a pressure-based algorithm without Riemann solvers, Experimental and Computational Multiphase Flow, Vol: 1, Pages: 271-285, ISSN: 2661-8869

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 promising alternatives to classical density-based algorithms based on Riemann solvers. The current paper investigates the predictive accuracy of fully-coupled pressure-based algorithms without Riemann solvers in modelling the interaction of shock waves with one-dimensional and two-dimensional bubbles in gas-gas and liquid-gas flows. For a gas bubble suspended in another gas, the mesh resolution and the applied advection schemes are found to only have a minor influence on the bubble shape and position, as well as the behaviour of the dominant shock waves and rarefaction fans. For a gas bubble suspended in a liquid, however, the mesh resolution has a critical influence on the shape, the position and the post-shock evolution of the bubble, as well as the pressure and temperature distribution.

Journal article

Pinheiro AP, Vedovoto JM, Neto ADS, van Wachem BGMet al., 2019, Ethanol droplet evaporation: Effects of ambient temperature, pressure and fuel vapor concentration, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, Vol: 143, ISSN: 0017-9310

Journal article

Jebelisinaki F, Boettcher R, van Wachem B, Mueller Pet al., 2019, Impact of dominant elastic to elastic-plastic millimeter-sized metal spheres with glass plates, POWDER TECHNOLOGY, Vol: 356, Pages: 208-221, ISSN: 0032-5910

Journal article

Evrard F, Denner F, van Wachem B, 2019, A multi-scale approach to simulate atomisation processes, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, Vol: 119, Pages: 194-216, ISSN: 0301-9322

Journal article

Marnani AK, Bueck A, Antonyuk S, van Wachem B, Thevenin D, Tomas Jet al., 2019, The Effect of Very Cohesive Ultra-Fine Particles in Mixtures on Compression, Consolidation, and Fluidization, PROCESSES, Vol: 7

Journal article

Sufian A, Knight C, O'Sullivan C, Van Wachem B, Dini Det al., 2019, Ability of a pore network model to predict fluid flow and drag in saturated granular materials, Computers and Geotechnics, Vol: 110, Pages: 344-366, ISSN: 0266-352X

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 tetrahedral Delaunay cells. Two local conductivity models are compared in simulating fluid flow in the PNM. The local pressure field was very accurately captured, while the local flux (flow rate) exhibited more scatter and sensitivity to the choice of the local conductance model. PNM based on the MDT clearly provided a better correlation with the IBM. There was close similarity in the network shortest paths, indicating that the PNM captures dominant flow channels. Comparison of streamline profiles demonstrated that local pressure drops coincided with the pore constrictions. A rigorous validation was undertaken for the drag force calculated from the PNM by comparing with analytical solutions for ordered array of spheres. This method was subsequently applied to all samples, and the calculated force was compared with the IBM data. Linear graded samples were able to calculate the force with reasonable accuracy, while the bimodal samples exhibited slightly more scatter.

Journal article

Xiao C-N, Fond B, Beyrau F, T'Joen C, Henkes R, Veenstra P, van Wachem Bet al., 2019, Numerical Investigation and Experimental Comparison of the Gas Dynamics in a Highly Underexpanded Confined Real Gas Jet, FLOW TURBULENCE AND COMBUSTION, Vol: 103, Pages: 141-173, ISSN: 1386-6184

Journal article

Shen L, Denner F, Morgan N, Wachem BV, Dini Det al., 2019, Transient structures in rupturing thin-films: Marangoni-induced symmetry-breaking pattern formation in viscous fluids

In the minutes immediately preceeding the rupture of a soap bubble,distinctive and repeatable patterns can be observed. These quasi-stabletransient structures are associated with the instabilities of the complexMarangoni flows on the curved thin film in the presence of a surfactantsolution. Here, we report a generalised Cahn-Hilliard-Swift-Hohenberg modelderived using asymptotic theory which describes the quasi-elastic wrinklingpattern formation and the consequent coarsening dynamics in a curvedsurfactant-laden thin film. By testing the theory against experiments on soapbubbles, we find quantitative agreement with the analytical predictions of thenucleation and the early coarsening phases associated with the patterns. Ourfindings provide fundamental physical understanding that can be used to(de-)stabilise thin films in the presence of surfactants and have importantimplications for both natural and industrial contexts, such as the productionof thin coating films, foams, emulsions and sprays.

Working paper

Perrier H, Denner F, Eaton MD, van Wachem BGMet al., 2019, On the numerical modelling of Corium spreading using Volume-of-Fluid methods, NUCLEAR ENGINEERING AND DESIGN, Vol: 345, Pages: 216-232, ISSN: 0029-5493

Journal article

You Q, Hopf T, Hintz W, Rannabauer S, Voigt N, van Wachem B, Henrich-Noack P, Sabel BAet al., 2019, Major effects on blood-retina barrier passage by minor alterations in design of polybutylcyanoacrylate nanoparticles, JOURNAL OF DRUG TARGETING, Vol: 27, Pages: 338-346, ISSN: 1061-186X

Journal article

Denner F, van Wachem BGM, 2019, Corrigendum to “Pressure-based algorithm for compressible interfacial flows with acoustically-conservative interface discretisation” (Journal of Computational Physics (2018) 367 (192–234), (S0021999118302535) (10.1016/j.jcp.2018.04.028)), Journal of Computational Physics, Vol: 381, Pages: 290-291, ISSN: 0021-9991

The authors regret that the definition of the Second-Order Backward Euler scheme for a varying time-step, given in Eq. (18), is incorrect. Assuming a varying time-step is applied, the Second-Order Backward Euler scheme (also often called BDF2 scheme) for the transient derivative of a general flow variable ϕ at cell P is defined, following the derivation given in Appendix A, as[Formula presented] where [Formula presented] is the current time-step, [Formula presented] is the previous time-step, [Formula presented], superscript (t) denotes the value at the new time-level, superscript [Formula presented] denotes the value at the previous time-level and superscript [Formula presented] denotes the value at the previous-previous time-level. Since the correct version of the Second-Order Backward Euler scheme as given above was already implemented in the software framework used to develop the proposed pressure-based algorithm, this correction has no effect on the presented results or the findings of the article. The authors would like to apologise for any inconvenience caused.

Journal article

Roloff C, Lukas E, van Wachem B, Thevenin Det al., 2019, Particle dynamics investigation by means of shadow imaging inside an air separator, CHEMICAL ENGINEERING SCIENCE, Vol: 195, Pages: 312-324, ISSN: 0009-2509

Journal article

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