Particles in a Periodic Double Shear Layer

Created using ANSYS 15.0

Learning Goals

In this tutorial, you will learn to:

• Load a flow field initial condition from a file using User Defined Function (UDF).
• Use Discrete Phase Model (DPM) to simulate particles in a flow.
• Define particle injection using an injection file / Create injection files using MATLAB codes.
• Visualize particle flow in CFD-Post.

Problem Specification

In this tutorial, we study a case of particle laden flows. The purpose is to illustrate some of the complex interactions between the uid phase and a dispersed particle phase using commercially available tools. For this purpose, we study a 2D-periodic double shear layer with disceminated particles as shown bellow:

In the absence of any perturbation, a mixing layer, for instance a Ux = U tanh(y) profile, diffuses under the action of viscosity to the mean value of top and bottom velocities. On the other hand, specially manufactured oscillations in the shearing layers will lead to the evolution of vorticies. These perturbations must satisfy the Orr-Sommerfeld equation, otherwise they are suppressed by viscosity. In this tutorial we provide the initial flow condition containing the Orr-Sommerfeld perturbation in a separate input file.

The point of having vorticies develop in the flow field, is to observe the interaction of particles with these structures. In a general sense, "light" particles get trapped in flow vorticies, while "heavier" particles carrying more inertia might get expelled under a corriolis-type effect from the swirling regions to gather along stretching regions of the flow. This effect is known as preferential concentration and is illustrated in the following sketch:
[Insert preferential concentration sketch]
Formal definitions, and a thorough discussion is provided in the Pre-Analysis section.

Go to Step 1: Pre-Analysis & Start-Up

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