Fluid dynamics keep astonishing scientists. Every video or animation of a fluid dynamics experiment brings new information and provides stunning displays.
Here are a few video from the APS Fluid Motion gallery.
Starfish larvae generate vortices when swimming which it utilizes to capture and eat algae.
In a previous post I shared with you an image of milk vortices created in a hot coffee cup. Today I share with you a demonstration of vortex formation using a free jet of air of a speed higher than that (stagnant) surrounding it.
This is one case of fluid instability called the Kelvin-Helmholtz instabilities (KHI) which occurs when two fluids have different velocities. A very popular and practical example of it are sea surface waves which are created due to the velocity difference between the water and wind.
More accurately, the shear force applied by one fluid (air in this case) on the other (water) creates a shear stress in the other fluid which if greater than the surface tension of the second fluid results in the KHI.
It is also common in clouds and on gas planets like Saturn and Jupiter as the following image of Saturn show.
Image credit: NASA/JPL/Space Science Institute
Universite Paris-Sud & Universite Paris-Saclay launched a website for the structural geology collection at University of South Paris (Paris-Sud). They call it the “StructuroTheque“.
The website allows you to investigate the items in details through a zoom lens as well as providing some details about the structure’s details and location of origin. Items are categorized by
The website allows you to view the collection as a flat gallery and on a map.
Ibrahim El Merehbi 
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