Introducing Gerris to Rescale

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Gerris is an open-source CFD software tool developed by Dr. Stéphane Popinet of the National Institute of Water and Atmospheric research (NIWA) in New Zealand. While originally developed for modeling complex wind patterns, the code has been used across the world to model complex flows such as spacecraft re-entry dynamics, drag on aircraft airfoils and fuel injections in car and rocket engines.

As part of Rescale’s continuing efforts to support all of the tools that our customers need, we have added Gerris to our library of available software. To demonstrate the utility of the Gerris tool, we ran a simple flow visualization and created a tutorial. This example simulation is a CFD analysis of 2D viscous flow around a heated cylinder.

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Initial Setup and Formation of Vortex Tail

This simulation outputs a series of images showing how vortices develop behind the cylinder as time passes. The resulting pattern of alternating vortices is known as a Bénard–von Kárman vortex street.

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Run 1 with r=0.06 (Above) and Run 9 with r=0.1 (Below)

Next, we used this simulation to study the effect that changing the diameter of the cylinder may have on the turbulence caused. To do this, we ran a parallel process DoE to evaluate a range of diameters ranging from 0.06 to 0.1 in increments of 0.005 length units.

Run 1 (Top) is a cylinder with a radius of 0.06, and Run 9 (Bottom) is a cylinder of radius 0.1. Apart from the change in radius, both cases have the same initial conditions. These two images also represent the same step in the simulation. In the case with the larger cylinder, the Bénard-Von Kármán Vortex Street is less uniform due to the increase in the size of the vortices formed.

If you want to learn more about Gerris, Gerris has a number of tutorials and examples at its website that are great tools for a first time Gerris user. Those tutorials can be found here: http://gfs.sourceforge.net/tutorial/tutorial/tutorial1.html

You can complete this Gerris tutorial here:
http://www.rescale.com/resources/analysistools/gerris-2d/.

If you have any other questions, please contact us at support@rescale.com

This article was written by Alan Humphrey.