ALE-FEM for Two-Phase Flows With Heat and Mass Transfer in Microchannels

2015 ◽  
Author(s):  
Gustavo R. Anjos ◽  
Norberto Mangiavacchi ◽  
Jose Pontes ◽  
John Thome
Keyword(s):  
Phase Interface ◽  
Computational Cost ◽  
Adaptive Mesh ◽  
Phase Method ◽  
Lagrangian Description ◽  
Arbitrary Lagrangian Eulerian ◽  
Two Phase Flows ◽  
Two Phase ◽  
Interface Position ◽  
Multiple Bubbles

A numerical method is described to study two-phase flows for single and multiple bubbles with phase change. The fluid flow equations are based on the Arbitrary Lagrangian-Eulerian formulation (ALE) and the Finite Element Method (FEM), creating a new two-phase method with an improved model for the liquid-gas interface in microchannels. A successful adaptive mesh update procedure is also described for effective management of the mesh at the two-phase interface to remove, add and repair surface elements, since the computational mesh nodes move according to the flow. The Lagrangian description explicitly defines the two-phase interface position by a set of interconnected nodes which ensures a sharp representation of the boundary, including the role of the surface tension. The methodology proposed for computing the curvature leads to accurate results with moderate programming effort and computational cost and it can also be applied to different configurations with an explicit description of the interface. Such a methodology can be employed to study accurately many problems such as oil extraction and refinement in the petroleum area, design of refrigeration systems, modelling of biological systems and efficient cooling of electronics for computational purposes, being the latter the aim of this research. The obtained numerical results will be described, therefore proving the capability of the proposed new methodology.

Friction Factor Equations Accuracy for Single and Two-Phase Flows

2020 ◽  
Author(s):  
Germano Scarabeli Custódio Assunção ◽  
Dykenlove Marcelin ◽  
João Carlos Von Hohendorff Filho ◽  
Denis José Schiozer ◽  
Marcelo Souza De Castro
Keyword(s):  
Pressure Drop ◽  
Friction Factor ◽  
Single Phase ◽  
Computational Cost ◽  
Two Phase Flows ◽  
Two Phase ◽  
Explicit Equation ◽  
Implicit Equation ◽  
Lower Accuracy ◽  
Statistical Metrics

Abstract Estimate pressure drop throughout petroleum production and transport system has an important role to properly sizing the various parameters involved in those complex facilities. One of the most challenging variables used to calculate the pressure drop is the friction factor, also known as Darcy–Weisbach’s friction factor. In this context, Colebrook’ s equation is recognized by many engineers and scientists as the most accurate equation to estimate it. However, due to its computational cost, since it is an implicit equation, several explicit equations have been developed over the decades to accurately estimate friction factor in a straightforward way. This paper aims to investigate accuracy of 46 of those explicit equations and Colebrook implicit equation against 2397 experimental points from single-phase and two-phase flows, with Reynolds number between 3000 and 735000 and relative roughness between 0 and 1.40 × 10−3. Applying three different statistical metrics, we concluded that the best explicit equation, proposed by Achour et al. (2002), presented better accuracy to estimate friction factor than Colebrook’s equation. On the other hand, we also showed that equations developed by Wood (1966), Rao and Kumar (2007) and Brkić (2016) must be used in specifics conditions which were developed, otherwise can produce highly inaccurate results. The remaining equations presented good accuracy and can be applied, however, presented similar or lower accuracy than Colebrook’s equation.

Optimal Configuration of Valves and Plumbing Lines in Complex Housing

2014 ◽  
Author(s):  
Pei Cao ◽  
Zhaoyan Fan ◽  
Robert Gao ◽  
Jiong Tang
Keyword(s):  
Design Optimization ◽  
Routing Algorithm ◽  
Shortest Paths ◽  
Computational Cost ◽  
Three Dimensional ◽  
Phase Method ◽  
Two Phase ◽  
Sequential Approach ◽  
Placement Optimization ◽  
Analytical Expressions

In engineering design, the volume and weight of a number of systems consisting of valves and plumbing lines often need to be minimized. In current practice, this is facilitated under empirical experience with trial and error, which is time-consuming and may not yield the optimal result. This problem is intrinsically difficult due to the challenge in the formulation of optimization problem that has to be computationally tractable. In this research, we choose a sequential approach towards the design optimization, i.e., first optimizing the placement of valves under prescribed constraints to minimize the volume occupied, and then identifying the shortest paths of plumbing lines to connect the valves. In the first part, the constraints are described by analytical expressions, and two approaches of valve placement optimization are reported, i.e., a two-phase method and a simulated annealing-based method. In the second part, a three-dimensional routing algorithm is explored to connect the valves. Our case study indicates that the design can indeed be automated and design optimization can be achieved under reasonable computational cost. The outcome of this research can benefit both existing manufacturing practice and future additive manufacturing.

Probabilistic Optimization of Two-Phase Flow Using Bayesian Models

2014 ◽  
Author(s):  
Kenji Miki ◽  
Arun Subramaniyan ◽  
Madhusudan Pai ◽  
Preetham Balasubramanyam
Keyword(s):  
Gas Turbines ◽  
Two Phase Flow ◽  
Flow System ◽  
Probabilistic Approach ◽  
Computational Cost ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Flow Configuration ◽  
Flow Systems

Gas-liquid two-phase flows are encountered in a variety of applications such as turbo-machinery flows, gas-turbines, ram-jet and scram-jets, automotive engines and aircraft engines. Designing systems to control such flows is enormously challenging owing to the addition of new non-dimensional groups that characterize the two-phase flow system compared to a single-phase flow. Additionally, two-phase flows can exhibit non-linear hydrodynamic instabilities that determine the overall behavior of the system. In this study, we choose a generic two-phase flow configuration that exhibits known complexities in realistic two-phase flow systems. The goal of the study is to optimize the geometry of the two-phase flow configuration with minimal computational cost. We propose a probabilistic approach to model the stochastic system and optimize the two-phase flow system under uncertain inputs. The potential benefits of the approach are highlighted along with future directions for using probabilistic design techniques to optimize two-phase flow systems.

A Novel Approach to Model Thermo-Fluids of Gearbox Systems

2013 ◽  
Author(s):  
Miad Yazdani ◽  
Marios Soteriou ◽  
Barbara Botros ◽  
Hailing Wu ◽  
Joe Liou ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Mechanics ◽  
Automobile Industry ◽  
Driving Forces ◽  
Fluid Model ◽  
Phase Interface ◽  
Computational Cost ◽  
Operating Conditions ◽  
Two Phase ◽  
Ansys Fluent

Gearboxes are integral machine components that determine the capability and reliability of many aerospace and automobile industry systems. Continuous demand for higher efficiency and reliability, increased load-carrying capacity and endurance life, smaller size, lower weight, lower noise and vibrations, prolonged service intervals and low costs are the main driving forces in the development of gear drives in the future. For many gearboxes, the thermo-fluids of the gas/oil/solid system determine the gearbox performance and its durability and life. However, there is a very limited predictive capability of the thermo-fluid characteristics of gearbox due, in large part, to its excessive complexity. In this paper, we present a coupled thermo-fluid model for the simulation of the two-phase flow along with the heat transfer within gearbox systems in a conjugate fashion. The primary challenge is the enormous separation of fluid-mechanics and heat-transfer time-scales which makes the conventional way of solving the coupled thermo-fluid system of equations computationally prohibitive. In contrast, the approximate approach developed in this study exploits this separation of scales to provide an accurate representation of the long-term, time dependent thermo-fluid state of the gearbox at a modest computational cost. The commercial package ANSYS FLUENT is used to solve URANS equations for fluid mechanics and VOF for the two-phase interface capturing, while the energy equation is modified through user-defined functions to solve for the temperature field inside the fluid and solid components. In addition, the heat generation raised by the meshing of the gears is provided by a separate model based on gear geometry and operating conditions. The approach is verified against a full-fidelity simulation for a simplified and accelerated gear system and is validated against experiments.

A Comparison Study of Numerical Methods for Compressible Two-Phase Flows

2017 ◽  
Vol 9 (5) ◽  
pp. 1111-1132 ◽  
Author(s):  
Jianyu Lin ◽  
Hang Ding ◽  
Xiyun Lu ◽  
Peng Wang
Keyword(s):  
Numerical Methods ◽  
Numerical Experiments ◽  
Mass Conservation ◽  
Detailed Comparison ◽  
Equation Model ◽  
Bubble Collapse ◽  
Comparison Study ◽  
Two Phase Flows ◽  
Two Phase ◽  
Interface Position

AbstractIn this article a comparison study of the numerical methods for compressible two-phase flows is presented. Although many numerical methods have been developed in recent years to deal with the jump conditions at the fluid-fluid interfaces in compressible multiphase flows, there is a lack of a detailed comparison of these methods. With this regard, the transport five equation model, the modified ghost fluid method and the cut-cell method are investigated here as the typical methods in this field. A variety of numerical experiments are conducted to examine their performance in simulating inviscid compressible two-phase flows. Numerical experiments include Richtmyer-Meshkov instability, interaction between a shock and a rectangle SF6 bubble, Rayleigh collapse of a cylindrical gas bubble in water and shock-induced bubble collapse, involving fluids with small or large density difference. Based on the numerical results, the performance of the method is assessed by the convergence order of the method with respect to interface position, mass conservation, interface resolution and computational efficiency.

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