A Discontinuity-Enriched Finite Element Method for Dynamic Multiple Crack Growth in Brittle Materials

This thesis introduces the Discontinuity-Enriched Finite Element Method (DE-FEM) for the modeling of dynamic multiple crack growth problems including branching and merging, as an alternative to eXtended/Generalized Finite Element Method (X/GFEM). DE-FEM differs from X/GFEM by placing the enriched degrees of freedom (DOFs) directly along the...

Controlling the breakup of spiralling jets: results from experiments, nonlinear simulations and linear stability analysis

We experimentally and numerically study the dynamics of a liquid jet issued from a rotating orifice, whose breakup is regulated by a vibrating piezo element. The helical trajectory of the spiralling jet yields fictitious forces varying along the jet whose longitudinal projections stretch and thin the jet, affecting the growth of perturbations....

United through separation: a study of the coalescence behaviour of separating micro-droplets

The coalescence of two droplets suspended in a viscous fluid is the focus of this study. When two droplets that are suspended in a shearing flow come in contact with each other, it is currently uncertain if the contact would result in coalescence. To be able to make such predictions, it is necessary to study the effects of the system parameters,...

Green synthesis of ultrapure La(OH)₃ nanoparticles by one-step method through spark ablation and electrospinning and its application to phosphate removal

La(OH)₃ metal engineered nanoparticles (MENPs) are efficient phosphate binders; however, complex synthesis procedures and purity as well as agglomeration issues impede their development and practical applications. Herein, a green and a one-step method in combination with the spark ablation aerosol technology and electrospinning is...

Coalescence of martensite under uniaxial tension of iron crystallites by atomistic simulations

Molecular dynamics simulations are used to study the effects of tensile loading on nucleation and subsequent growth of bcc phase in pure fcc iron. The results show that orientation variant selection occurs during the stress-induced fcc-to-bcc transformation, which leads to the coalescence of neighbouring bcc platelets with identical...

Droplet collisions of water and milk in a spray with Langevin turbulence dispersion

In this work we investigate droplet-droplet collision interactions in a spray system using an Eulerian-Lagrangian model with subgrid turbulence dispersion. The effect of different droplet viscosities on the type and frequency of droplet collision is investigated, knowledge of which is essential for industrial processes such as spray drying...

Droplet-Turbulence interactions and quasi-equilibrium dynamics in turbulent emulsions

We perform direct numerical simulations (DNS) of emulsions in homogeneous isotropic turbulence using a pseudopotential lattice-Boltzmann (PP-LB) method. Improving on previous literature by minimizing droplet dissolution and spurious currents, we show that the PP-LB technique is capable of long stable simulations in certain parameter regions....

Thermal fluctuations in capillary thinning of thin liquid films

Thermal fluctuations have been shown to influence the thinning dynamics of planar thin liquid films, bringing predicted rupture times closer to experiments. Most liquid films in nature and industry are, however, non-planar. Thinning of such films not just results from the interplay between stabilizing surface tension forces and destabilizing...

Electrolyte effects on recirculating dense bubbly flow: An experimental study using X-ray imaging

In this work, the effect of an electrolyte (up to 2 M of NaCl dissolved in water) on a homogeneous dense bubbly flow, in an airlift bubble column, is studied using nonintrusive techniques. X-ray and high-speed imaging are used to investigate the bubble size distribution, the local and the global gas-fraction profiles. The major effect of the...

Evaluation of Micromixing Models for Turbulent Mixing in Supercritical Water

Hydrothermal flames have become a very important field of study, especially for supercritical water oxidation. In supercritical water oxidation hazardous, toxic or non-biodegradable aqueous organic waste water streams can be efficiently destructed. Supercritical water oxidation takes place in a aqueous environment above the supercritical point....

Effect of viscosity on droplet-droplet collisional interaction

A complete knowledge of the effect of droplet viscosity on droplet-droplet collision outcomes is essential for industrial processes such as spray drying. When droplets with dispersed solids are dried, the apparent viscosity of the dispersed phase increases by many orders of magnitude, which drastically changes the outcome of a droplet-droplet...

Foam Flow Experiments. I. Estimation of the Bubble generation-Coalescence Function

Gas injection leads to foam formation in porous media in the presence of surfactant solutions, which is used for flow diversion and enhanced oil recovery. We present here laboratory experiments of co-injecting nitrogen and sodium C14?16 alpha olefin sulfonate with two concentrations: 20× the critical micelle concentration (CMC) in an...

Integration of Product Recovery in Microbial Advanced Biofuel Production: Overcoming Emulsification Challenges

Fermentation broth components influence droplet coalescence and hinder advanced biofuel recovery during fermentation

Developments in synthetic biology enabled the microbial production of long chain hydrocarbons, which can be used as advanced biofuels in aviation or transportation. Currently, these fuels are not economically competitive due to their production costs. The current process offers room for improvement: by utilizing lignocellulosic feedstock,...

Droplet collisions in turbulence

Liquid droplets occur in many natural phenomena and play an important role in a large number of industrial applications. One of the distinct properties of droplets as opposed to solid particles is their ability to merge, or coalesce upon collision. Coalescence of liquid drops is of importance in for example the food industry, where the shelf...

Dynamics of droplet breakup in a T-junction

The breakup of droplets due to creeping motion in a confined microchannel geometry is studied using three-dimensional numerical simulations. Analogously to unconfined droplets, there exist two distinct breakup phases: (i) a quasi-steady droplet deformation driven by the externally applied flow; and (ii) a surface-tension-driven three-dimensional...

ShopHouse Transformation: Appraisal of the pre-war shophouse and its contemporary application

We are now faced with new social problems of deteriorating sense of community and a disjointed society that is generated by the Modern city paradigms. To tackle these new problems does not mean the complete restoration of the old system. It should mean a new typology that reflects the traditional system in an innovative way. By mixing the old...

Percolation and Coalescing Particle Systems