# numerical simulation of multiphase flows

Some examples of possible projects:

**1) DNS of a sedementing suspension in a non-Newtonian fluid**

* Motivation: much literature available on settling behavior in Newtonian fluids, but little is known about dynamics for non-Newtonian fluids despite the many applications in which the suspending fluid is non-Newtonian (e.g., in food processing)

* Goal: use DNS in order to gain understanding of bulk behavior of a sedimenting suspension in a non-Newtonian fluid from understanding of (a) settling of a single sphere under gravity and (b) the interaction of 2 spheres settling under gravity

* Approach: (a) we make use of an existing DNS/IBM code written in Fortran for fully-resolved simulation of particle-laden flows, (b) extension of code with implementation of non-Newtonian model for molecular stress, (c) study of a single and 2 simultaneously settling particles, (c) study of suspension of many simultaneously settling particles

* Requirements for prospective MSc student: good programming skills are highly desired, student should have passed the exams forModeling of Thermodynamic and Hydrodyamic System and Introduction to Multiphase Flow

* Supervisors: WP Breugem (main/responsible supervisor), M.T. Shajahan (co-supervisor)

**(2) DNS of turbulent stratified gas/liquid flow**

* Motivation: Turbulent stratified 2-phase flow is commonly encountered in transport of natural gas in a horizontal pipe. Another example is the transport of waste water in sewage systems. In industry such flows are typically modelled with a so-called two-fluid model for the cross-sectionally averaged velocities, which requires an accurate modelling of the interfacial stress.

* Goal: use DNS of stratified gas/liquid flow to obtain the interfacial stress for the smooth and wavy stratified regimes + to gain insight in the processes contributing to the stress + modelling of the interfacial stre

* Approach: (a) we make use of an existing pseudo-spectral DNS solver for single-phase flow, (b) extension of the model to 2-phase flow (jump in fluid properties over the interface, calculation of curvature from level-set approach for tracking the interface, grid refinement close to interface, coordinate transformation in vertical direction to adjust grid to deforming interface), (c) study of flow for co- and counter-current gas/liquid flow in confined channel.

* Requirements for prospective MSc student: this is a rather difficult assignment -> perseverance, strong analytical and programming skills will be needed to make this ambitious project to a success, student should have passed the exams for Modeling of Thermodynamic and Hydrodyamic System and Introduction to Multiphase Flow

* Supervisor: WP Breugem & Ruud Henkes

**(3) CFD modelling of bubble screens**

* Motivation: Bubble screens are used to avoid/hamper the intrusion of salt into fresh water when ship-locks are opened. For the design and optimization of such systems an accurate and reliable CFD model is highly desired.

* Goal: (a) development of CFD model for bubble screens to study the intrusion of salt, (b) gain understanding in dynamics of bubble screens to mitigate intrusion of salt water, (c) optimization of bubble screen system

* Approach: (a) we will make use of existing CFD packages (OpenFoam/Fluent) to model a bubble screen, (b) once (mixture / 2-fluid) model has been developed, it will be used to study the bubble screen dynamics and possibly the optimization of bubble screens for mitigating salt intrusion

* Requirements for prospective MSc student: affinity with CFD modelling,

student should have passed the exams for Modeling of Thermodynamic and Hydrodyamic System and Introduction to Multiphase Flow* Supervisors: WP Breugem & MJBM Pourquie (supervisors from TU Delft), P. van der Ven & G. Oldenziel (Deltares - a hydraulic institute in Delft)