Multiphase Flow

We have developed a monolithic Newton-multigrid solver for multiphase flow problems which solves velocity, pressure and interface position simultaneously. The main idea of our work is based on the formulations discussed in [1], where it points out the feasibility of a fully implicit monolithic solver for multiphase flow problems via two formulations, a curvature-free level set approach and a curvature-free cutoff material function approach. Both formulations are fully implicit and have the advantages of requiring less regularity, since neither normals nor curvature are explicitly calculated, and no capillary time restriction. Furthermore, standard Navier-Stokes solvers might be used, which do not have to take into account inhomogeneous force terms. The reinitialization issue is integrated with a nonlinear terms within the formulations.The nonlinearity is treated with a Newton-type solver with divided difference evaluation of the Jacobian matrices. The resulting linearized system ins...

Miscible viscous fingering (VF) classically occurs when a less viscous fluid displaces a miscible more viscous one in a porous medium. We analyze the influence on such VF of differential diffusion between two species each of them influencing the viscosity of the fluids at hand. We show that such double diffusive effects can destabilize the classically stable situation of a

We investigate steam condensation induced water hammer (waha) phenomena and present experimental and theoretical results. The experiments were performed in the PMK-2 facility, which is a full-pressure thermohydraulic model of the nuclear power plant of VVER-440/312 type and located in the Atomic Energy Research Institute Budapest, Hungary. The present experimental setup is capable to measure water hammer phenomena in a wide range of steam pressure, cold water temperate and floating mass rate at a high level of accuracy. On the theoretical side waha is studied and analyzed with the WAHA3 model based on two-phase flow six first-order partial differential equations that present one dimensional, surface averaged mass, momentum and energy balances. A second order accurate high-resolution shock-capturing numerical scheme was applied with different kind of limiters in the numerical calculations. The applied two-fluid model shows some similarities to Relap5 which is widely used in the nucle...

The stability of a partially mobile thin liquid plane-parallel film between two gas or oil phases is studied. The long wave approximation is used to analyze the influence of soluble ionic surfactants and non-surface active background electrolyte on the increment/decrement of fluctuations. The material properties of the corresponding multiphase flow and interfaces are taken into account. The equilibrium state of the film is described by the classical DLVO theory in which the Van der Waals and electrostatic disjoining pressures are included. The fluctuation analysis of the electro-diffusion fluxes, velocity of the components, concentrations, electric potential and film thickness give the analytical criteria for stability of the equilibrium state. Numerical results show changes of the stability region with increasing surfactant concentration and significant influence of the background electrolyte. The stabilizing effects of the Gibbs elasticity, surface and bulk viscosities are demonst...

In high-velocity free-surface flows, the interactions between the fast-flowing flow and the atmosphere can lead to strong air-water mixing through the free-surface. The flow resistance may be derived from momentum and energy considerations. This was undertaken through some theoretical development based upon an extension of traditional integral approaches to air-water flows, with the re-analyses of detailed air-water measurements in both prototype spillways and large-size physical models. Both the momentum and energy approaches yielded close results in terms of the Darcy-Weisbach friction factor. Based upon the same data sets, the absence of correction coefficients was found to underestimate the residual energy, compared to the detailed calculations using the relevant air-water kinetic energy and pressure correction coefficients. The finding has basic design implications, which are discussed.

It is almost impossible to solve the modern fluid flow problems without the use of Computational Fluid Dynamics (CFD). In petroleum industry, flow simulations assist engineers to develop the most efficient well design and it is essential to understand the multiphase flow details. However, despite the high accuracy, performing the numerical simulation fall short in providing the required results in timely manner. This article presents two case studies of Smart Proxy Models (SPM) utilizing artificial intelligence (AI) and Machine Learning (ML) techniques to appraise the behavior of the chaotic system and predict the dynamic features including pressure, velocity and the evolution of phase fraction within the process at each time-step at a much lower run time. Proposed cases concentrate on 2-D dam-break and 3-D fluidized bed problems, using OpenFOAM and MFiX, CFD software applications, respectively. This paper focuses on building and improving the artificial neural network (ANN) models ...

The icing, or the formation of ice on the airfoil of an aircraft, is a complex phenomenon which contribute many factor. When an aircraft passes through a cloud of supercooled droplets, the impact destroys the metastabile equilibrium, emphasizing the freezing and the collecting of ice on aircraft components. The ice, collecting in various shape on the airfoils, reduces the aerodynamic efficiency. There are many factor which affect the icing like the liquid water content (LWC), the diameter of the droplets, the temperature of the air and, very important, the operational condition of the aircraft. The icing wind tunnels with suitable aerodynamic flow and icing cloud characteristics are used to support on-ground the aircraft icing certification process. The water droplet spectrum and the liquid water content required for the test conditions are injecting in the tunnel by means of an array of spray nozzles.In this paper air supplied nozzles are characterised by use of PDA system to evalu...

This paper presents a new type of super-cavitating hydrofoil section designed to have optimal performance both in supercavitating conditions and in pre-cavitating conditions (including transitional regime). The main hydrodynamic characteristics are given in terms of lift drag and cavity shape at different angles of attack and cavitation numbers. The optimum performance is reached through a particular design philosophy illustrated in the paper which is intensely based on multi-phase URANSE flow simulations, using a bubble dynamic cavitation model to follow the generation and evaporation of the vapor phase.in the fully turbulent unsteady viscous flow. The new profile family, initially created for hydrofoil crafts, may result useful also for applications on super-cavitating or surface-piercing propellers.

The transport of methane from marine sediments into the seawater and then into the atmosphere is important in the context of its role as a greenhouse gas. In the present work, we use an artificial laboratory setup in order to investigate the mechanisms of flow and transport induced by rising gas in a permeable sediment We use a combination of the experimental techniques Particle Image Velocimetry (PIV), 3D Planar Laser-induced Fluorescence (3D PLIF) and refractive-index matching for the visualization and quantification of different aspects of this multiphase flow phenomenon. The gas injected continuously into the sediment leads to a cone-shaped structure of trapped gas and to a spatially and temporally fluctuating escape of bubbles at the upper interface. The temporal variability of the total volume of trapped gas results in fluctuations of liquid velocities in the sediment pores and therefore leads to an enhanced mixing of solutes in the sediment. Furthermore, the highly resolved 3...

Electrical Capacitance Volume Tomography (ECVT) has emerged as an attractive technology for addressing instrumentation requirements in various energy-related multiphase flow systems. ECVT can monitor multiple flow conditions and reconstruct real-time 3D images from capacitance measurements using a large set of electrode plates placed around the processes column enclosing the sensed flow system. ECVT is non-intrusive and allows the measurement of changes in mutual capacitance between all possible plate pair combinations. The objective of this paper is to provide a comprehensive review of recent advances in ECVT, enabling robust monitoring of multiphase flows, especially water-containing multiphase flows.