[Robotgroup] water flow

[Leslie Filip]

Did you use angled blades that were in sync with the speed of flow?  
If this is not taken into account then the result sucks. FYI I am  
talking about blobs that are around a half inch in diameter, not  
sprinkle. I think a frozen arc of blobs is magnitudes more  
interesting than a single vertical stack of droplets, granted even  
those are pretty cool looking with the fluorescent dye and UV LEDs.

I keep saying this so please if someone has seen otherwise correct  
me: "The start of laminar flow requires a ramp-up of speed within the  
output chamber before exit." This is why trying to pulse blobs with a  
plain valve does not work. It is the uniform speed and trajectory of  
water molecules in laminar flow as well as surface tension that  
allows the blobs to remain coherent.

Looking forward to the party.

Les


On 10 Aug 2006, at 12:47 PM, brooksdesign wrote:

> I tried several chopping type methods but none worked as good a my  
> sprayer hose valve thing in the sink .I have been messing with   
> chamber with water feeding in the side ,a nozzle on top and a  
> diaphram on bottom that can be pulsed by mechanical piston on a  
> crankshaft of with air pressure .I discovered this while rinsing  
> out a soap bottle ,good blobbieness .I'm building this as part of  
> the stage show I'm planning for the .....wait for it ....The last  
> party and official house dissassembly event at brooks' place in  
> Bastrop (no date yet but soon).
> -brooks
>
> -----Original Message-----
>> From: Leslie Filip <lfilip at mac.com>
>> Sent: Aug 10, 2006 7:29 AM
>> To: Austin Robotgroup Mailing List <robotgroup at puremagic.com>
>> Subject: Re: [Robotgroup] water flow
>>
>> If the blades are in a blower-type arrangement instead of a fan-like
>> arrangement it would chop the water more smoothly. The nozzle would
>> have to be shooting from within the cage though.
>>
>> Les
>>
>>
>> On 10 Aug 2006, at 2:53 AM, Leslie Filip wrote:
>>
>>> 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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