From incompressible to compressible multiphase flow simulations in the presence of surface tension: numerical methods and applications
This talk will be a comprehensive talk about current state-of-the-art methods developed for the simulation of multiphase flow problems in the presence of surface tension forces.
During the first part we will provide a description and review of methods used to simulate problems in the presence of multiple phases paying especial attention to : (i) methods and algorithms used to track the interface position, (ii) the performance of advection methods in those cells containing a fluid mixture, and (iii) methods used to compute surface tension forces. The extension of methods widely used in the incompressible limit to problems where compressibility effects become important will be also discussed. In particular we will present the generalization of an all-Mach formulation for multiphase flows accounting for surface tension and viscous forces. The proposed numerical method, based on the Volume Of Fluid (VOF) method, stresses the importance of a consistent advection of conservative quantities and the color function to avoid any numerical diffusion of mass, momentum and energy across the interface during the advection step.
In the second part of the talk we will show fundamental and applied problems where the methods proposed are allowing to investigate flow configurations that could not be solved some years back. In particular we will focus on problems where the vorticity production at interface is relevant to predict energy dissipation. As an example of the potential of the code we will evaluate numerically vorticity production in model problems including the ligament breakup by a Rayleigh–Plateau instability, which is indeed critical to predict the vorticity generated in atomization process and bubbly flows, and the liquid jet injection problem. These tests will serve us as illustrative examples to discuss the necessary conditions to resolve all scales in multiphase problems in the presence of surface tension and viscous effects.
The influence of compressibility effects will be discussed for problems related to the collapse of bubbles close to a wall and the impact of a liquid jet on a corrugated surface. The codes will be validated for simplified configurations and tested in complex configurations that require a high robustness of the solver.
Applications of optical techniques for the characterization of multiphase flows
(Juliana Braga Rodrigues Loureiro)
This talk will cover the general aspects of optical methods for multiphase flow characterization. The precise experimental characterization of two-phase flow parameters is challenging due to difficulties imposed by time varying interfaces, as well as due to potential flow disturbance caused by sensor probes. In this context, optical methods present advantage due to non-intrusive characteristic of several techniques. This talk will cover shadowgraph method for multiphase flow characterization, which has provided relevant contributions on the understanding of flow phenomena. Additionally, the principles of velocimetry methods, such as particle image velocimetry (IPV) and laser doppler velocimetry (LDV) will be discussed, as well as advantages and disadvantages of each method will be presented.
Mechanistic modeling of multiphase flow
(Rigoberto Eleazar Melgarejo Morales)
This talk will cover general aspects of multiphase flow, including description of fundamental parameters, as well as modelling approaches for their prediction. Void fraction, pressure drop and other parameters will be presented focused on applications for one-dimensional models. The predictive methods for some parameters on two-phase flow will be presented and discussed, with emphasis on the range of validity of each method.
Thermodynamic for liquid-vapor equilibria
(Jose Roberto Simões Moreira)
This talk will comprise aspects of thermodynamic potentials, including conditions of phase equilibria for multiphase systems, focusing on liquid-vapor conditions. These aspects are essential for modelling and understanding of boiling and condensation processes, including incipience of bubble nucleation and droplet formation in homogenous conditions. Additionally, this talk will address aspects of phase change phenomena, including introductory aspects of homogenous and heterogeneous nucleation.
(Marcio da Silveira Carvalho)
In most applications, microscale multiphase flow behavior is governed by the balance between capillary and viscous, or viscoelastic in case of polymer solutions, forces. Fundamental understanding of capillary hydrodynamics may lead to important technology development in different areas, including the manufacturing of optical and specialty films, printed electronics, inkjet printing, biological sensors, CO2 sequestration and enhance oil recovery.
Interfacial tension acts in different ways in the interface between two immiscible fluids. The interfacial force along a curved interface leads to a pressure discontinuity that is proportional to the interface curvature. If the interfacial tension is non-uniform, because of temperature or composition gradients, it leads to tangential stresses along the interface that can completely change the flow behavior.
In this lecture, we present the fundamentals of capillary hydrodynamics and discuss industrial examples where it is relevant. The first example is related to the manufacturing of functional films by slot coating process. Slot coating is one of the preferred methods to obtain a thin and uniform liquid layer over a moving substrate. The coated film must have a particular microstructure in order to function as designed. In many applications, such as solar panels, printed electronics and batteries, the coating liquid is a suspension of particles. The rheology of these systems may be quite complex and depends on the particle concentration and orientation with respect to the flow. Moreover, particles can migrate driven by different mechanisms leading to a non-uniform particle distribution in the flow. The fundamental understanding of this problem and its impact on the coating process are not well understood. We analyze slot coating flows of particle suspensions, investigating particle distribution and orientation and how process parameters may affect the final structure of the coated layer.
The second example is associated with displacement flows in porous media, with application in oil recovery. A porous media can be thought as a 3D network of constricted micro channels, e.g. a very complex microfluidic device. We study the effect of complex dispersions (oil-water emulsions and soft microcapsules suspensions) in the pore scale. Visualization of the flow of complex fluids through a transparent network of micro-channels, which serves as a model of a porous media, reveals how the pore blocking by the dispersed phase improves pore-level displacement efficiency, leading to lower residual oil saturation. In the case of soft capsule dispersions, the degree of pore level mobility reduction is controlled by the elastic properties of the capsule shell, which are fabricated using capillary microfluidic devices.
Spatio temporal filter velocimetry: fundamentals and applications
Spatiotemporal filter velocimetry (SFV) is a velocimetry based on image processing of time-series images of particles following fluid motion. It enables us to measure velocity distribution like PIV in accuracy as high as LDV. The principle and fundamentals of SFV are presented in this talk. Applications of SFV to multiphase flows are also introduced to demonstrate the ability of SFV.
Two challenges for the sizing of long oil tie-backs: the prediction of slugs and the impact of physical chemistry on multiphase flow
8 years of academic research
PhD at Delft University of Technology, The Netherlands, on the liquid film and droplets in annular flow
Post-doc at Institut de Mécanique des Fluides de Toulouse (IMFT), France, on the modeling of a turbulent cloud of droplets with coalescence
2 years at the research institute Sintef in Norway, with work on gas-liquid pipe flow (in particular slug flow) and liquid-liquid pipe flow
7 years at TOTAL in R&D on multiphase flow. Mainly on multiphase flow in pipes, but now also trying to make the link between physical chemistry and multiphase flow
Numerical simulation of Newtonian and non-Newtonian two-phase flows
In the first part of this lecture, we introduce some common properties of non-Newtonian fluids, in particular elasticity and yield-stress, and how they can be incorporated into direct numerical simulations by coupling a representative constitutive equation with a Navier-Stokes solver. Some common constitutive equations will be introduced and compared. Further, we will review two ways to model two-phase flows involving non-Newtonian fluids, by a level set method and by a front tracking method.
The second part of the lecture will focus on recent advances in the field of non-Newtonian flows in single and two-phase: droplet and particle motion in laminar shear flows of yield-stress fluids, the structure of turbulent channel flow in single-phase of polymeric and elastoviscoplastic fluids, and finally, we will look at surfactant-laden droplets in turbulent flows.