scholarly journals A compressible multiphase flow model for violent aerated wave impact problems

2014 ◽  
Vol 470 (2172) ◽  
pp. 20140542 ◽  
Author(s):  
Z. H. Ma ◽  
D. M. Causon ◽  
L. Qian ◽  
C. G. Mingham ◽  
H. B. Gu ◽  
...  
Keyword(s):  
Multiphase Flow ◽  
Flow Model ◽  
Volume Fraction ◽  
Vertical Wall ◽  
Homogeneous Material ◽  
Finite Volume Scheme ◽  
Advection Equation ◽  
Wave Impact ◽  
Phase Volume Fraction ◽  
Compressible Multiphase Flow

This paper focuses on the numerical modelling of wave impact events under air entrapment and aeration effects. The underlying flow model treats the dispersed water wave as a compressible mixture of air and water with homogeneous material properties. The corresponding mathematical equations are based on a multiphase flow model which builds on the conservation laws of mass, momentum and energy as well as the gas-phase volume fraction advection equation. A high-order finite volume scheme based on monotone upstream-centred schemes for conservation law reconstruction is used to discretize the integral form of the governing equations. The numerical flux across a mesh cell face is estimated by means of the HLLC approximate Riemann solver. A third-order total variation diminishing Runge–Kutta scheme is adopted to obtain a time-accurate solution. The present model provides an effective way to deal with the compressibility of air and water–air mixtures. Several test cases have been calculated using the present approach, including a gravity-induced liquid piston, free drop of a water column in a closed tank, water–air shock tubes, slamming of a flat plate into still pure and aerated water and a plunging wave impact at a vertical wall. The obtained results agree well with experiments, exact solutions and other numerical computations. This demonstrates the potential of the current method to tackle more general wave–air–structure interaction problems.

scholarly journals A relaxation scheme for a hyperbolic multiphase flow model

2019 ◽  
Vol 53 (5) ◽  
pp. 1763-1795 ◽  
Author(s):  
Khaled Saleh
Keyword(s):  
Multiphase Flow ◽  
Flow Model ◽  
Two Phase Flow ◽  
Equations Of State ◽  
Energy Inequality ◽  
Approximation Error ◽  
Finite Volume Scheme ◽  
Phase Flow ◽  
Two Phase ◽  
Relaxation Scheme

This article is the first of two in which we develop a relaxation finite volume scheme for the convective part of the multiphase flow models introduced in the series of papers (Hérard, C.R. Math. 354 (2016) 954–959; Hérard, Math. Comput. Modell. 45 (2007) 732–755; Boukili and Hérard, ESAIM: M2AN 53 (2019) 1031–1059). In the present article we focus on barotropic flows where in each phase the pressure is a given function of the density. The case of general equations of state will be the purpose of the second article. We show how it is possible to extend the relaxation scheme designed in Coquel et al. (ESAIM: M2AN 48 (2013) 165–206) for the barotropic Baer–Nunziato two phase flow model to the multiphase flow model with N – where N is arbitrarily large – phases. The obtained scheme inherits the main properties of the relaxation scheme designed for the Baer–Nunziato two phase flow model. It applies to general barotropic equations of state. It is able to cope with arbitrarily small values of the statistical phase fractions. The approximated phase fractions and phase densities are proven to remain positive and a fully discrete energy inequality is also proven under a classical CFL condition. For N = 3, the relaxation scheme is compared with Rusanov’s scheme, which is the only numerical scheme presently available for the three phase flow model (see Boukili and Hérard, ESAIM: M2AN 53 (2019) 1031–1059). For the same level of refinement, the relaxation scheme is shown to be much more accurate than Rusanov’s scheme, and for a given level of approximation error, the relaxation scheme is shown to perform much better in terms of computational cost than Rusanov’s scheme. Moreover, contrary to Rusanov’s scheme which develops strong oscillations when approximating vanishing phase solutions, the numerical results show that the relaxation scheme remains stable in such regimes.

A Three Dimensional Simulation of M-ICAR Process

2012 ◽  
Vol 516-517 ◽  
pp. 54-57
Author(s):  
Quan Yue Geng ◽  
Jie Wang ◽  
Hong Wei Zhang ◽  
Hui Jia
Keyword(s):  
Water Level ◽  
Flow Model ◽  
Hydraulic Retention Time ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Great Influence ◽  
Mixture Flow ◽  
Phase Volume Fraction ◽  
Dimensional Simulation ◽  
Settling Process

Adopting standard k-ε turbulent model and mixture flow model, settling process and decant process was simulated using 3-d numerical simulation in M-ICAR(Mixture-Intermittently Cycle Aeration Reactor) process to analyze the changes of sludge phase volume fraction. The simulation results showed that the changes of feeding wastewater had great influence on sludge settle ability in decant process, and the position of decanter needed optimized; it had no influence on sludge settle ability in settling process. For considering the lowest hydraulic retention time, the research controlled maximum feeding wastewater for 1610m3/h. Internal recycle had no influence on sludge settle ability. Two methods were proposed: the first one, the water level of decanter was set 3.9m (sludge volume fraction of this suspended area was less than 0.05), feeding velocity was 0.07 m/s; the second, keep the water level of decanter 3.75 m, reduce feeding velocity (preliminary setting feeding velocity 0.06 m/s). The two methods had no influence on sludge settle ability.

scholarly journals Low Pressure Experimental Validation of Low-Dimensional Analytical Model for Air–Water Two-Phase Transient Flow in Horizontal Pipelines

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 220
Author(s):  
Hamdi Mnasri ◽  
Amine Meziou ◽  
Matthew A. Franchek ◽  
Wai Lam Loh ◽  
Thiam Teik Wan ◽  
...  
Keyword(s):  
Multiphase Flow ◽  
Experimental Validation ◽  
Flow Model ◽  
Transient Flow ◽  
Volume Fraction ◽  
Laboratory Data ◽  
Low Pressure ◽  
Two Phase ◽  
Fluid Properties ◽  
Low Dimensional

This paper presents a low-pressure experimental validation of a two-phase transient pipeline flow model. Measured pressure and flow rate data are collected for slug and froth flow patterns at the low pressure of 6 bar at the National University of Singapore Multiphase Flow Loop facility. The analyzed low-dimensional model proposed in comprises a steady-state multiphase flow model in series with a linear dynamic model capturing the flow transients. The model is based on a dissipative distributed parameter model for transient flow in transmission lines employing equivalent fluid properties. These parameters are based solely on the flowing conditions, fluid properties and pipeline geometry. OLGA simulations are employed as an independent method to validate the low-dimension model. Both low-dimensional and OLGA models are evaluated based on the estimated two-phase pressure transients for varying gas volume fraction (GVF). Both models estimated the two-phase flow transient pressure within 5% mean absolute percent error of the laboratory data. Additionally, an unavoidable presence of entrained air within a pipeline is confirmed for the case of 0% GVF as evidenced by the pressure transient estimation. Thus, dampened oscillations in the simulated 0% GVF case exists owing to an increase in the fluid compressibility.

scholarly journals Brine Formation and Mobilization in Submarine Hydrothermal Systems: Insights from a Novel Multiphase Hydrothermal Flow Model in the System H2O–NaCl

2020 ◽  
Author(s):  
F. Vehling ◽  
J. Hasenclever ◽  
L. Rüpke
Keyword(s):  
Multiphase Flow ◽  
Flow Model ◽  
Full Range ◽  
Hydrothermal Systems ◽  
Finite Volume Scheme ◽  
Time Step ◽  
Bulk Fluid ◽  
Submarine Hydrothermal Systems ◽  
Brine Layer ◽  
Hydrothermal Flow

AbstractNumerical models have become indispensable tools for investigating submarine hydrothermal systems and for relating seafloor observations to physicochemical processes at depth. Particularly useful are multiphase models that account for phase separation phenomena, so that model predictions can be compared to observed variations in vent fluid salinity. Yet, the numerics of multiphase flow remain a challenge. Here we present a novel hydrothermal flow model for the system H2O–NaCl able to resolve multiphase flow over the full range of pressure, temperature, and salinity variations that are relevant to submarine hydrothermal systems. The method is based on a 2-D finite volume scheme that uses a Newton–Raphson algorithm to couple the governing conservation equations and to treat the non-linearity of the fluid properties. The method uses pressure, specific fluid enthalpy, and bulk fluid salt content as primary variables, is not bounded to the Courant time step size, and allows for a direct control of how accurately mass and energy conservation is ensured. In a first application of this new model, we investigate brine formation and mobilization in hydrothermal systems driven by a transient basal temperature boundary condition—analogue to seawater circulation systems found at mid-ocean ridges. We find that basal heating results in the rapid formation of a stable brine layer that thermally insulates the driving heat source. While this brine layer is stable under steady-state conditions, it can be mobilized as a consequence of variations in heat input leading to brine entrainment and the venting of highly saline fluids.

Particle Tracking Velocimetry Measurement of Bubble-Bubble Interaction

2003 ◽  
Author(s):  
Masa-aki Ashihara ◽  
Atsuhide Kitagawa ◽  
Masa-aki Ishikawa ◽  
Akihiro Nakashinchi ◽  
Yuichi Murai ◽  
...  
Keyword(s):  
Multiphase Flow ◽  
Particle Tracking ◽  
Particle Tracking Velocimetry ◽  
Volume Fraction ◽  
Vertical Wall ◽  
Measurement Data ◽  
Vertical Direction ◽  
Interaction Patterns ◽  
Bubble Interaction ◽  
Sliding Bubbles

Bubble-bubble interaction is a quite fundamental issue to understand multiphase flow dynamics and to improve mathematical models of dispersed multiphase flow for higher volume fraction of dispersion. In this study, the bubble-bubble interaction is measured using Particle Tracking Velocimetry (PTV) in various environments. First, bubbles sliding on a vertical wall are measured using 2-D PTV. Second, the free rising bubbles in an unbounded space are measured applying 3-D PTV. Third, the simultaneous measurement for gas and liquid phases in the layer of wall-sliding bubbles is carried out. The measurement data have shown that the average bubble-bubble interaction patterns in the wall-sliding bubbles and in the free rising bubbles were attractive in the vertical direction and repulsive in the horizontal direction. The relation between the carrier phase flow structure and the bubbles’ motion is detected to explain the mechanism of the bubble-bubble interaction.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

scholarly journals Estimating the phase volume fraction of multi-phase steel via unsupervised deep learning

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sung Wook Kim ◽  
Seong-Hoon Kang ◽  
Se-Jong Kim ◽  
Seungchul Lee
Keyword(s):  
High Performance ◽  
Materials Science ◽  
Volume Fraction ◽  
Training Data ◽  
Phase Fraction ◽  
Phase Volume ◽  
Generative Adversarial Network ◽  
Phase Volume Fraction ◽  
Original Dataset ◽  
Multi Phase

AbstractAdvanced high strength steel (AHSS) is a steel of multi-phase microstructure that is processed under several conditions to meet the current high-performance requirements from the industry. Deep neural network (DNN) has emerged as a promising tool in materials science for the task of estimating the phase volume fraction of these steels. Despite its advantages, one of its major drawbacks is its requirement of a sufficient amount of training data with correct labels to the network. This often comes as a challenge in many areas where obtaining data and labeling it is extremely labor-intensive. To overcome this challenge, an unsupervised way of learning DNN, which does not require any manual labeling, is proposed. Information maximizing generative adversarial network (InfoGAN) is used to learn the underlying probability distribution of each phase and generate realistic sample points with class labels. Then, the generated data is used for training an MLP classifier, which in turn predicts the labels for the original dataset. The result shows a mean relative error of 4.53% at most, while it can be as low as 0.73%, which implies the estimated phase fraction closely matches the true phase fraction. This presents the high feasibility of using the proposed methodology for fast and precise estimation of phase volume fraction in both industry and academia.

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