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It always happens at the last minute. My simulations have been run and converged and are ready to be presented for tomorrow morning's board meeting. Then it happens... I try to create a plot of the temperature variation along a line in my STAR-CCM+ simulation 5 minutes before the end of my day and I find my data is scattered all over the place! There's no way I could possibly present this result! Argh!!!

Thankfully, my buddy "Steve" came to the rescue. Now if you've never been introduced to Steve, you are missing out! Steve is the "go-to" guy whenever you are having difficulties setting up or running your simulations. Steve is more commonly known as "The Steve Portal" where registered users will find a vast knowledge base for CFD and all the STAR products, software downloads and other useful links.

Once again, Steve did not disappoint! I logged in and found the following article. It was precisely what I needed to finish my report so I could get home in time for my evening's barbecue!

 Why are my data points in an XY Plot randomly connected?

By default, data is not sorted when creating XY plots.  By activating the data sorting, the abscissa (horizontal axis) values are ensured to run in an increasing order.
If you are creating a scatter plot, then the plot is not affected. However if you draw a line chart, and the source data is not sorted, it could affect how the data is displayed.
In this example, the temperature change is evaluated along a line that is created on a boundary with a constrained plane derived part. The horizontal axis is the position in the Z-direction and the vertical axis is the evaluated temperature.

By default the data is displayed as a scatter graph, without any joining lines, as illustrated in the following plot:

Graph 1

When adding a line to make it a curve, you can encounter an unexpected result as illustrated in the following plot:

Graph 2

In which case you can sort the data to make it a clean curve by ticking on the sort data option in the plot properties:


The result is a clean line plot with all data along the horizontal axis in ascending order.

Graph 3

For more helpful tips from Steve, log on to The Steve Portal.

Entry to the Steve Portal, CD-adapco's customer service center web-site is permitted to registered customers of CD-adapco. To become a CD-adapco customer, click here.

Matthew Godo
STAR-CCM+ Product Manager
Stephen Ferguson
Marketing Director
James Clement
STAR-CCM+ Product Manager
Joel Davison
Lead Product Manager, STAR-CCM+
Dr Mesh
Meshing Guru
Ravindra Aglave
Director - Chemical Processing
Karin Frojd
Sabine Goodwin
Director, Product Marketing