I was thinking about how to get water to arid places, and I realised that you need very fast moving flows to get enough water through a pipe of reasonable gauge to make the enterprise viable. However water is slowed by friction in ordinary pipes, making long distances difficult.

If the friction could be overcome or reduced, it might be possible to better bring water to where it is needed.

The only way I see to move water quickly is to float the water down the tube using some sort of electrostatic or magnetic levitation. However I don't know if this would be possible. The interior of the tube could be at low pressure and the water could move at very high speeds if this could be accomplished.

Perhaps one could harvest the heat energy from the air / solar radiation in arid places and use it to power a propulsion system to compensate for the friction? Like with solar panels or something?

Edit: LOL @ the tags

What about converting the water to a gas (which I'm assuming has less friction) and pumping it that way?

I guess there would have to be something on the other end to effeciently convert it back to a liquid, though.

But it would be a shitload less dense, so you would need a very high volumetric flow rate (read: huge pipe or very fast moving steam) to get much water out the other end.

im sure youd get more answers in DIY.

anyway, why not just use wider pipe? sure it costs more but making a special material that reduces friction would also be really expensive, and any system to propel the water would also be expensive

a large, cylindrical pipe is effective for reducing surface area, which is good

You don't need high velocity flow as much as high volume. I.e. Large pipes. Gravity's useful for the pressure source. Lookit the roman aquaducts.

In abscence of high up sources of water, waterpumps, and water towers.


Srsly. In any case, if I remember correctly, most losses are from turbulent flow in the water.

Is the turbulent flow caused by the water on the outside being slowed by friction? If so then some sort of mixing system is needed, perhaps making the flow rotate would stabilise the stream somewhat?

For water pipe over hundreds, or thousands of miles of miles speeding the water stream up seems the best way to increase utilisation of investment. Would some sort of lubricant work on the inside of the pipe? I think it'd be hard to push water at any speed with it rubbing against solid matter.

Coat the insides with some hydrophobic substance? It might make the water dirty though.

I think you're missing something here. Water is not a solid. It does not need lubricant, because it is its own lubricant.

Also, friction does not cause losses in pipes. At least not in the way you're thinking. One of the basic tenets of fluid dynamics is that velocity of a fluid at a surface is 0. That is there are no dosses due to friction between a fluid and the pipe wall. However, the pipe wall's roughness causes eddies in the fluid. The rougher the wall, the bigger eddies it creates, and the more loss you have.

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Now, there are two ways to increase flow. One is increasing velocity, the other is increasing diameter. Increasing velocity also increases pressure losses quadratically while increasing flow linearly. Increasing diameter decreases pressure losses linearly (and then some actually) and increases flow quadratically.

Now I'm not saying, that decreasing the frictional losses by using some smoother material wouldn't work, its just that usually the costs associated with doing such are prohibitive for large systems, with the alternative of making bigger pipes.

There are several things to consider when trying to irrigate a distant, area, and these problems can't be condensed to simply, "we need to make water move faster."

So, a big smooth pipe.

I think the biggest issue of irrigating arid regions isn't getting the water there, it's stopping it from GOING anywhere once you get it there! Deserts are deserts for a reason. Any moisture there is going to evaporate in a snap! That's why places like Las Vegas are wasting millions of gallons from the western US's water reservoirs. All the vegas yuppies want to have green lawns, and all the hotels want fountains. Well, guess what: water EVAPORATES when it's hot! And that's why the Colorado River never reaches the sea.