Ansys CFX – Free Surface 3D

Written by cfd.ninja

March 12, 2020

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Free surface is the surface of a fluid that is subject to zero parallel shear stress, such as the interface between two homogeneous fluidsfor example, liquid water and the air in the Earth’s atmosphere. Unlike liquidsgases cannot form a free surface on their own. Fluidized/liquified solids, including slurriesgranular materials, and powders may form a free surface.

A liquid in a gravitational field will form a free surface if unconfined from above. Under mechanical equilibrium this free surface must be perpendicular to the forces acting on the liquid; if not there would be a force along the surface, and the liquid would flow in that direction. Thus, on the surface of the Earth, all free surfaces of liquids are horizontal unless disturbed (except near solids dipping into them, where surface tension distorts the surface in a region called the meniscus).

In a free liquid that is not affected by outside forces such as a gravitational field, internal attractive forces only play a role (e.g. Van der Waals forceshydrogen bonds). Its free surface will assume the shape with the least surface area for its volume: a perfect sphere. Such behaviour can be expressed in terms of surface tension. It can be demonstrated experimentally by observing a large globule of oil placed below the surface of a mixture of water and alcohol having the same density so the oil has neutral buoyancy.

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In this tutorial you will learn to simulate a free surface in 3D using ANSYS CFX. First, we will build a geometry and then we will generate the mesh using a structured mesh in Ansys Meshing.

Ansys CFX – NACA 4412 (Structured Mesh)

Ansys CFX – NACA 4412 (Structured Mesh)

The NACA four-digit wing sections define the profile by:
First digit describing maximum camber as percentage of the chord.
Second digit describing the distance of maximum camber from the airfoil leading edge in tenths of the chord.

OpenFOAM vs ANSYS CFX

OpenFOAM vs ANSYS CFX

OpenFOAM is the free, open source CFD software developed primarily by OpenCFD Ltd since 2004. It has a large user base across most areas of engineering and science, from both commercial and academic organisations.

We share the same tutorial in 2D using ANSYS Fluent.

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