Release 14.0
Free Surface Flows
• 例子
– 两个连续相 – 浇模(Mold filling) – 溃坝(Dam break) – 注油(Filling of a gasoline tank) – 液面晃动(Sloshing of a surface in a container) – 明渠流动(Open flow in a channel) – 处理方法:homogeneous , 相和相之间分享同样
• Power Generation – Droplet combustion – Coal combustion – Condensation & boiling – Fuel cells – Cavitation
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• Oil and Gas – Oil wells – Pipelines
• 在微尺度(分子)上的混合用质量分数的方法模拟(多组分流方法).
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Release 14.0
Continuous-Dispersed Multiphase
•一相是离散粒子(discrete particles), 液滴(droplets), 或空泡(bubbles)散 布在连续相中 • 例如:
(annular flow). • 模拟对不同区域(regimes)相间相互
作用的方法, (drag laws, interfacial area, etc.) 可能大不相同 • 模型的选择, 经验很重要!
Gas-Liquid Flow in a Vertical Pipe
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Release 14.0
Modeling Approaches
多相流模拟的两个基本方法:
• Eulerian-Eulerian
– 两相之间连续的相互作用. 假定相由流体计算域流出. – 一般来说, 每个相的体分数和流场变量单独求解. – 每个Eulerian dispersed phase具有单一直径的特征. 用标准的欧拉方法模拟三种不同
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Release 14.0
Multiphase Applications
• Chemical and Process Industry – Gas cleaning – Fluidized bed reactors – Bubble columns – Polymer production – Mixers – Dryers
–雨: air + water (droplet flow) –软饮料: Liquid + bubbles (bubbly flow) –泥浆: Water + sand (particulate flow) –含尘空气: (particulate flow) –一液体里含有不能融合的另一种液滴, 如. 醋里的油滴.
大小的空气泡泡在水中的分布情况, 需要四相的欧拉方法进行计算
• Environment – Fog – Rain – Erosion – Emission
• Biomedical – Blood flows – Eyes – Lungs
Release 14.0பைடு நூலகம்
Examples of Multiphase Flows
• Horizontal Bubble Reactor (Bubbly Flow)
的速度和场变量(volume fraction除外）
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Release 14.0
Different Multiphase Flow Regimes
• 多相流(MPF)没有一个统一模型!
• 右图中的多相流在气体流量逐渐增 加的情况下，从左到右有在连续相 中分布均匀的空泡流, 到节涌流 (slug flow, 又名活塞流 ), 到环状流
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October 16, 2020
Release 14.0
Examples of Multiphase Flows
• Cavitation (Phase Change)
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October 16, 2020
Release 14.0
Lecture 6 ANSYS CFD Multiphase
Introduction to ANSYD CFD
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October 16, 2020
Release 14.0
Multiphase in ANSYS CFX
Introduction to ANSYD CFD
Examples of Multiphase Flows • Free Surface Flow (Dam Break)
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October 16, 2020
Release 14.0
Examples of Multiphase Flows • Injection and Breakup of Liquid Droplets from a Nozzle
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© 2011 ANSYS, Inc.
October 16, 2020
Release 14.0
Multiphase Flows
• 多相流模拟指.
– 含有超过一种流体 – 每种流体由其自有流场变量描述
(u, v, w, p, r, T)
• 相或流体之间在微观层面上是混合的. 混合尺度小雨求解尺度, 但大于分子 尺度.
•若在空间上不连续, 则该相为离散相. 否则为连续相. • 允许大的密度差存在 (rc/ rd=1000, rc/ rd=10-3) • 允许大差异的速度场. •通常的例子如空泡塔器 (bubble columns)和流化床(fluidized beds).
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October 16, 2020