B What Causes the Void Formation in Discarded Yogurt During Disposal?

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The discussion centers on the observation of a void forming around a stream of yogurt as it is poured into a waste bin, which is attributed to fluid dynamics principles. The phenomenon creates a shear zone that drags fluid downwards, resulting in a visible gap around the stream. This effect is noted to occur in viscous fluids, potentially indicating that the failed yogurt behaves as a non-Newtonian fluid. However, there is no specific name for this phenomenon beyond basic fluid dynamics concepts like surface tension. The inquiry highlights an interesting aspect of fluid behavior in industrial settings.
ROGER WALL
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Hello, I don't know anything about fluid dynamics and hope someone can tell me what it is I saw the other day. I work in yoghurt factory and had to throw out a whole vat full of product (the culture died). So i pumped the product thru a say 70mm hose and poured it into a waste bin (which was being sucked out from the bottom as I filled it up - don;t know if this has something to do with it - don't think so).

Anyway as i stood mesmerised (took 20min to dispose of all the yoghurt) i noticed that a void existed around the round stream of yogurt coming out of the hose as it entered the pool of yoghurt in the container. Being a white liquid (as oppes to looking a water) it was easy to see this 0.5mm - 1mm void around the stream of yoghurt as it formed a dark shadow.

Also the yohurt in the pool was sucked down the 'outside' of the void - proabaly not surprising - like water going down a drain hole.
SO this void - does it have a name (fancy name not just surface tension, etc). Is this phenominar used for anything? Thanks, ROger.
 
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ROGER WALL said:
SO this void - does it have a name (fancy name not just surface tension, etc).
The stream of fluid entering the surface creates a shear zone below the surface, that is dragging fluid downwards outside the entering stream. That results in the gap forming in the viscous fluid at the surface, outside the entering fluid.

A failed yoghurt may be a non-Newtonian fluid.
There is no eponym that I know of for the described effect.
 

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