Flow noise, useful in creating swirls in turbulent fluids for example, was a logical step to add to my port to OSL of Stephan Gustavsons implementation of Simplex Noise. The code is available on my blog, including a link to a YouTube video with an animated example. A still from that video is shown below.
Please note that the code as presented in the article is far from beautiful. That is no fault of Stefan but introduced by my simple minded conversion to OSL. I am sure a lot can be improved