16-fsurf

# 16-fsurf - Lecture 16 Free Surface Flows Applied...

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1 Lecture 16 - Free Surface Flows Applied Computational Fluid Dynamics Instructor: André Bakker © André Bakker (2002-2006) © Fluent Inc. (2002)

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2 Example: spinning bowl Example: flow in a spinning bowl. Re = 1E6 At startup, the bowl is partially filled with water. The water surface deforms once the bowl starts spinning. The animation covers three full revolutions.
3 Example: splashing droplet

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4 Example: pouring water A bucket of water is poured through the air into a container of kerosene. This disrupts the kerosene, and air bubbles formed soon rise to the surface and break. The three liquids in this simulation do not mix, and after a time the water collects at the bottom of the container. The sliding mesh model is used to model the tipping of the bucket.
5 VOF Model Volume of fluid (VOF) model overview. VOF is an Eulerian fixed-grid technique. Interface tracking scheme. Application: modeling of gravity current. Surface tension and wall adhesion. Solution strategies. Summary.

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6 Modeling techniques Lagrangian methods: The grid moves and follows the shape of the interface. Interface is specifically delineated and precisely followed. Suited for viscous, laminar flows. Problems of mesh distortion, resulting in instability and internal inaccuracy. Eulerian methods: Fluid travels between cells of the fixed mesh and there is no problem with mesh distortion. Adaptive grid techniques. Fixed grid techniques, e.g. volume of fluid (VOF) method.
7 Volume of fluid model Immiscible fluids with clearly defined interface. Shape of the interface is of interest. Typical problems: Jet breakup. Motion of large bubbles in a liquid. Motion of liquid after a dam break. Steady or transient tracking of any liquid-gas interface. Inappropriate if bubbles are small compared to a control volume (bubble columns).

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8 Assumes that each control volume contains just one phase (or the interface between phases).
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