[Robotgroup] water flow

[Leslie Filip]

Gray,

I believe it is still laminar flow you are wanting, only that instead  
of constant streams you want blobs. In order to accomplish this the  
material has to have a ramp up of speed inside the laminar flow tube  
before it exits. In the examples I have seen, it was not possible to  
have a series of closely spaced blobs using only control valves.  
There may be a solution.

If you have an arc of laminar flow water, I believe you could  
mechanically chop it into blobs, removing the water where you want  
space. Think of the way a jet engine's blades are tilted. As the  
water passed through rotating blades the entry point and exit point  
of the blades in the water column would coincide with the forward  
motion of the water arc, thus chopping it into a series of small  
cylinders. Then through surface tension, each cylinder would reshape  
itself into blobs. It is the lack of uncontrolled angular momentum  
that allows the blob to remain a blob.

There is a limit to the speed at which the water can travel as a  
blob, however. When the speed goes beyond a certain point, the air  
pressure at the front of the blob destabilizes it. In a parabolic  
arc, this is as true for the speed at which the water exits the  
nozzle as it is for the descent.

The arcs I saw in Las Vegas in some of the smaller water gardens went  
about 10-12 feet without a problem. The arcs are more prone to  
destabilization than blobs due to surface tension and the differing  
speed from one part of the column to another. I don't think there  
would be any problem at all with blobs remaining blobs over this  
distance.

Les


On 09 Aug 2006, at 5:26 PM, Gray Mack wrote:

> What I am looking for is a term for creating liquid
> blobs. How big they can be and stuff based on driping
> from a drop tower or launched.
>
> Another approach- Put some LED's, a microcontroller, a
> capacitor, and an inductor+rectifier into a bunch of
> ping pong balls. Fire them from an air blower/cannon
> at synchronized intervals in an arch or straight down
> or through a clear pipe and when they land they roll
> to a hopper to be recycled. As they are loaded into
> the cannon the capacitor is charged through the
> inductor via a varying magnetic field at the cannon
> and instructions on when to light up are also sent
> through the field to each ball. The capacitor has
> enough power to blink LEDs a few times during its
> travel as directed by the cannon.
> -Gray
>
> --- Shane Geiger <sgeiger at ncee.net> wrote:
>
>> FYI:  http://en.wikipedia.org/wiki/Laminar_flow
>>
>>
>>
>>
>> Paul Atkinson wrote:
>>> Gray,
>>>
>>>   I don't think you'll have a problem if you
>> aren't susceptible to jitter between pulses (as
>> stepper motors are.)
>>>
>>>   You may have to have a special driver (giveio)
>> or something like that to access the parallel port
>> under Win XP/NT/2k if memory serves.
>>>
>>>   The opposite of laminar flow is turbulent flow.
>>>
>>>   Paul
>
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