MadSci Network: Engineering

Re: What causes burrowing hoses?

Date: Wed Aug 5 11:58:52 1998
Posted By: Justin Roux, Grad, professional engineer plus research, Intergraph UK Ltd
Area of science: Engineering
ID: 897196017.Eg

I must say that this has me rather foxed. If my wife would allow it, I would try it out in the garden.... she doesn't hold with my scientific nature. Here's a guess.

If you put a short straw into a jar of water and blow across the top (so as to make a note like in a pan-pipe) the water will be drawn up through the straw and spray in the direction you were blowing. Air-brushes work in this way.

The hose, pointing down in the ground, draws the soil surrounding the nozzle radially in towards the flow in a similar manner. This fluidises the earth around the nozzle and the spiralling, tauroid eddy should coax the hose downwards.. the process should be repetetive and self sustaining. I can't see it overcoming the stiffness of the hose, nor the friction of the soil once it's got going, but maybe while my wife is out shopping I'll investigate. Furthermore, movements in fluidised earth normally result in a downward overall journey - experiment by throwing someone into quicksand and watching what happens.

As for pulling the hose out, that's plain old air-pressure and friction - like removing a wine cork.

A great one to think upon.


Admin note:
Justin Roux later provided the following additional information:

Hello again, Scott.

Let's revisit your question long after it was posted just to show that scientists never sleep. I was discussing the burrowing hose phenomenon with my friend, Neil Adams, a fearless teacher, and a fine renaissance scientific mind. He suggested that the burrowing action may be due to differential pressures created between the flow of water at the nozzle and up the sides of the hose towards the surface. Think about it; aerodymanic lift over an aerofoil works when particles travel at different speeds but with the same mass flow rate. If that condition applied then the pressure at the fast flowing nozzle would be lower than that at the sides of the hose giving a net downward force. I have no doubt that he will try it with his class next year... Watch this space, if only to see a piture of Neil 'nine lives' Adams being dug out of the school football pitch with a fire hose in his hand.


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