By Yehiel Gotkis
Based on the video from http://www.zmescience.com/science/simulating-black-hole-bath-tub/
Being interested in vortex science I looked into the video presented in http://www.zmescience.com/science/simulating-black-hole-bath-tub/. Observing the developments presented, I assumed that when a stringed wave (see the image below) approaches a vortex, the vortex-imposed wrenching action should cause the forward scattered strings to longitudinally compress and rise in their amplitudes, and an opposite trend should take place at the other side where the wave propagation direction opposes the direction of the vortex angular momentum. And also the vortex wrenching action should force the strings to bend and turn to propagate in the directions the wrenching action dictates.
Well, as it appeared, my expectation on the vortex action was overly too kind as compared to the actual action, much more aggressive and cruel, as well as a set of images with slightly reduced contrast, than I could expect (at least for the case presented in the cited video).
The set of images above (an original representative video snapshot from the mentioned work, and two its black&white copies with different level of contrast and brightness manipulated to better highlight the upper surface light reflections, and also a set of slightly less contrasted snapshots are shown at the end of this quick note.
In the images, the surface light reflections clearly mark the wave fronts propagating towards the vortex and the vortex circle itself.
Being not sure about the origin of the bottom shade waviness and considering relevant only the reflections by the upper water surface, I manipulated the image contrast and brightness to minimize the bottom shadow contributions. And, here are my conclusive remarks based on the corresponding image analysis:
- The wave fronts demonstrate, not perfectly, but clearly, here and there (where the light is properly reflected under given set of conditions) multiple fragments of the stringed wave structure
- The vortex counterclockwise wrenching action forces the incoming plane wave fronts to bend and turn to propagate in the counterclockwise direction around the vortex, while the nearby to the vortex wavy waters are pulled and swallowed into the vortex. Together with the information carried about the interaction details.
- The vortex pulling and bending action clearly manifests itself already quite at a distance to the funnel, especially on the side where the wave propagation direction and the direction of the vortex angular movement coincide (lower side of the image shown).
- Unfortunately, in this case the vortex wrenching action not only bends and dis-bundles the wave strings, but also smashes and rips them apart causing a complete (hardly analyzable) structural chaos in the nearby to vortex area and especially beyond it.
- The shown features are conceptually well reproduced in all, more than a dozen, snapshots extracted and analysed.
At the end, just a word about the way the authors of the cited work report on their FFT-loaded way of extracting information about the wave-vortex interference pattern. I am not a world class FFT expert, though have some relevant experience using it. Just by looking at the images, I can imagine how much noise has to be filtered out of the information mess the vortex creates to extract the buried in the noise interference bumps and dips. I always remind myself how easy in my experience was to create a periodic, though false, residual pattern when a non-perfect FFT filtering was applied. The FFT works great when the noise contribution is not a dominating factor.
Yes, BTW, pay attention what is going on these days with the LIGO data treatment approach, also heavily FFT- loaded.
A set of 12 snapshots with a slightly lessened contrast is shown below just to demonstrate how messy is the area around the vortex at different moments of time. And also numerous string-structured fragments appearing here and there all over the area around and beyond the vortex.
To help visualizing the large scale vortex circular action I am adding a one more set of images. It is about how the “matter” redistribution proceeds (steady state regime) around a vortex in a media with a very slow single-directional flow (from right to left in the images shown).
It starts with a “cloud” of a shredded floating stuff placed over the surface of the water at the right side of the exposed spot (a) With time under the action of the large scale circular vortex-induced flows was moved around and at some point developed a classical spiral galaxy pattern (b-e) with the vortex (Black Hole) pulling in and swallowing most of the stuff, the “matter”, from around (f) until it is completely exhausted.