Bubbles travelling through viscous liquids

  • #1
Hi,
Im doing a Invesitgation of bubbles travelling through liquids. Im blowing bubbles of fixed volume up different viscous liquids. I seem to have got a anomaly but I can't explain it
When recording one of the repeats in the foam bath I saw that the bubble rushed up the liquid. It took 1.4 seconds to travel 8cm, which was half the time compared, to the previous results I had taken. At first I simply thought that that bubble must have hit another bubble and thus having a larger volume the bubble accelerated up the tank. However in the video I took it is clear that there is no collision between any bubbles. I tried to analyse the video carefully and came to the assumption that when a bubble travels up a liquid inevitably some air will be left behind almost forming a track. Therefore if I immediately blow a bubble exactly through the same path as the previous bubble, little bubbles will start to merge to the bubble and thus making it accelerate. My analogy was like when a skier goes down a powder slope he will create tracks. If another skier comes down those tracks he will travel quicker. This is because there are fewer resistive forces acting on the bubble.
My question is if there is a specific name for this or if anybody can explain in a more scientific way.
If anybody is interested I could send them the video so you can analyse in more detail.
Thanks,
 

Answers and Replies

  • #2
Drakkith
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Hmmm... I did a little searching and found a couple of papers on this topic. I don't know if it will help, but you can give them a read.
http://www.redalyc.org/pdf/620/62026895006.pdf
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.192.9665&rep=rep1&type=pdf

One thing to note from the first paper is the following part of the 1st paragraph:

Let us consider a train of bubbles rising unconfined through still liquid. Its rise velocity can be approximated by that of a single bubble plus the velocity defect caused by the wakes (Marks, 1973).

Might you be experiencing an upward motion of the water in the column caused by the previous bubbles?
 
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