Over-expanded Nozzle

Created using ANSYS 16.2

Disclaimer:

This problem was inspired by the work of Balasubramanyam Sasanapuri, Manish Kumar & Sutikno Wirogo (ANSYS Inc.) on the "Simulation of flow through Supersonic Cruise Nozzle: A validation study". 

Everything was created from scratches, but the geometry was based on the pictures presented on that workshop. That work does not provide details on how the mesh was created, and there are very few words about the solver configuration. Therefore this tutorial is only inspired by that workshop, and all the results and methods presented here were obtained from the author's learning, experience and testing.

Learning Goals

In this tutorial, you will learn to:

• Obtain the diamond shocks on a nozzle using an axisymmetric geometry.
• Apply more advanced concepts of Compressible Flows and generate a more sophisticated simulation
• Qualitatively verify the CFD results from FLUENT by comparing the contour plots to the expected shape. The Verification & Validation section will give insights on how one could get a more precise comparison with real data and other more accurate simulations.

Problem Specification

We want to simulate an over-expanded nozzle in FLUENT, and try to obtain the cool "Diamond Shock" pattern shown in the this figure:

For that, we need to design a Nozzle that has a measured exit pressure smaller than the ambient pressure. Therefore, the nozzle is "too big" and ended up expanding the flow too much. The flow, trying to accommodate to that will form an oblique shock outside the nozzle

Another characteristic of over-expanded nozzle is that the "plume" of the jet gets contracted, opposed to an under-expanded nozzle where the plume "diverges" in the radial direction. 

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

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