Work being done nationwide to deal with flooding

[robblok]

3 minutes ago, impulse said:

 

And your "fact" is based on any kind of math or engineering?   Or just your perception? 

 

Using axial flow pumps to move water around is done all over the world.  Boat propellers are axial flow impellers.  In fact, the photo shows that these particular boats were purpose designed.  The concept is sound, and well accepted.   Whether they have enough HP for the amount of water requires some analysis.  Not just a glance at a photo.

 

If you can show the math that proves it doesn't work, great.  Otherwise you don't know.  And then, it's just bashing something (and someone) you don't understand.

 

I'll repeat my question from a recent, similar thread:

 

If you add 30,000 HP in the downstream direction over a period of 24 hours to a river flowing at a rate of  1 million cubic meters per minute, how much faster will you drain 50,000 acre feet of water than it would drain naturally?

 

What's the ROI of building and maintaining that infrastructure that everyone seems to think they need to spend hundreds of billions of baht on?

 

If you can't answer those questions (showing your math) I'd suggest you let the engineers on location do their jobs without commenting.

I have not been schooled in the subject your talking about, but I wonder how it works. I can understand it working if you have a continuous line of boats along the river. But how it is now.. just one line.. how can it work. I mean you push the water faster for a short distance and then the volume of water downstream will slow it down. Would the effects not be marginal in such a large river with only a few points to speed it up ?

 

I am not saying I am right, just trying to understand because in my mind it does not make much sense unless you got multiple points to speed up the water at certain distances. 

 

I just imagine myself throwing a small torpedo shape sub under water in a swimmingpool. It will go a bit and then stop going and assume the speed of the other water. Because of its size related to volume of the water its effects will be negligible on the rest of the water. 

 

Just trying to think out loud.. your the expert please tell me what is wrong in my line of thought.

 

IMHO it won't work here because there are not enough boats and not stationed together in a line to make the pushing effect continuous. 

[beau thai]

we need more long term thinking to invest in dams with hydro electric generation capability to fix flooding and become more energy efficient, if necessary with japanese or chinese investment- on the right terms!

[melvinmelvin]

 

during the massive floods 6-7 years ago there was a really big discussion on the merits of using boats

here on tvf, really long thread, lots of people involved

as far as I remember the majority concluded that there is no point in using boats, will not help

 

some also sent this to Mythbusters as smth for them to sort out

 

 

[impulse]

14 minutes ago, robblok said:

I have not been schooled in the subject your talking about, but I wonder how it works. I can understand it working if you have a continuous line of boats along the river. But how it is now.. just one line.. how can it work. I mean you push the water faster for a short distance and then the volume of water downstream will slow it down. Would the effects not be marginal in such a large river with only a few points to speed it up ?

 

I am not saying I am right, just trying to understand because in my mind it does not make much sense unless you got multiple points to speed up the water at certain distances. 

 

I just imagine myself throwing a small torpedo shape sub under water in a swimmingpool. It will go a bit and then stop going and assume the speed of the other water. Because of its size related to volume of the water its effects will be negligible on the rest of the water. 

 

Just trying to think out loud.. your the expert please tell me what is wrong in my line of thought.

 

IMHO it won't work here because there are not enough boats and not stationed together in a line to make the pushing effect continuous. 

 

Basically, you're adding kinetic energy to the water in the downstream direction.  The kinetic energy of the water is 1/2 Mass x Velocity^2.

 

Add energy with a pump (or a boat propeller) and the velocity goes up, which means that the mass flow rate increases.  And that's the objective.  To move more water out of the area faster.  It may look like an insignificant effect, but it can make a big difference over a period of time.

 

Frankly, since the idea came from Rama 9, I'm surprised they let the discussion get so disrespectful here on TVF.  I'm not defending the concept because of its originator.  The concept is used all over the world.

 

 

 

[robblok]

3 minutes ago, impulse said:

 

Basically, you're adding kinetic energy to the water in the downstream direction.  The kinetic energy of the water is 1/2 Mass x Velocity^2.

 

Add energy with a pump (or a boat propeller) and the velocity goes up, which means that the mass flow rate increases.  And that's the objective.  To move more water out of the area faster.  It may look like an insignificant effect, but it can make a big difference over a period of time.

 

Frankly, since the idea came from Rama 9, I'm surprised they let the discussion get so disrespectful here on TVF.  I'm not defending the concept because of its originator.  The concept is used all over the world.

 

 

 

I get that, but to get any kind of result don't you need a lot more kinetic energy in the water than what we have seen so far. That small line of boats is not going to accomplish much on a huge river. I am not saying the concept is flawed... just saying that the current effort is not enough to really make a difference.

[Aussie999]

13 minutes ago, impulse said:

 

Basically, you're adding kinetic energy to the water in the downstream direction.  The kinetic energy of the water is 1/2 Mass x Velocity^2.

 

Add energy with a pump (or a boat propeller) and the velocity goes up, which means that the mass flow rate increases.  And that's the objective.  To move more water out of the area faster.  It may look like an insignificant effect, but it can make a big difference over a period of time.

 

Frankly, since the idea came from Rama 9, I'm surprised they let the discussion get so disrespectful here on TVF.  I'm not defending the concept because of its originator.  The concept is used all over the world.

 

 

 

Even if what you say is correct, the increase, in flow rate down stream, would means and increase in downstream flooding, also, the barges themselves act as a minor barrier, increasing the upstream level... the whole effect is insignificant, the only thing it increases is air pollution. Another thing, just look at the flow from the pumps, I can piss more that the flow.

[impulse]

7 minutes ago, Aussie999 said:

Even if what you say is correct, the increase, in flow rate down stream, would means and increase in downstream flooding, also, the barges themselves act as a minor barrier, increasing the upstream level... the whole effect is insignificant, the only thing it increases is air pollution. Another thing, just look at the flow from the pumps, I can piss more that the flow.

 

The fact that you claim you can pee over 20 horsepower pretty much shoots your argument's credibility in the ass, doesn't it?

[yodsak]

worth a read ?

[impulse]

44 minutes ago, Aussie999 said:

Even if what you say is correct, the increase, in flow rate down stream, would means and increase in downstream flooding, also, the barges themselves act as a minor barrier, increasing the upstream level... the whole effect is insignificant, the only thing it increases is air pollution. Another thing, just look at the flow from the pumps, I can piss more that the flow.

 

You're right that the devil's in the details.  We'd need a lot of information to predict the performance, like HP installed, flow rate, amount of excess water, etc.  Or, a little information to see if they're actually working- like before and after river velocities.

 

Here's one example you'll like.  I was at Pilot 111 fishing a couple of years back when they turned on their aerator paddles.  They're tiny little fractional HP motors, so I was surprised at how they got the water moving.  It took an hour or so, but the entire pond had a circular flow at around 2 or 3 km/hr.  The water was flowing in a circular motion, not inside an enclosed pipe.  Friction losses and eddy current probably reduced the effectiveness, but the net effect was an increase in the mass flow rate within the pond.

 

If a fractional HP, low efficiency paddle pump can get the water moving, it only stands to reason that a few thousand HP and better efficiency impellers can make a difference in a larger system like a flooded river.

 

Whether it's a significant difference or not depend on the numbers.  How much HP vs how much water.   The increase in flow rate isn't negated by the boats blocking the flow, the eddy currents, the nature of an open stream as opposed to a closed pipe, friction losses (which are significant in a small pipe, but negligible in a huge river) or a dozen other factors that people are calling out.   

 

It's an engineering issue.  And, contrary to what a lot of people claim, I've worked with a lot of very competent Thai engineers.

 

[CGW]

1 hour ago, robblok said:

I get that, but to get any kind of result don't you need a lot more kinetic energy in the water than what we have seen so far. That small line of boats is not going to accomplish much on a huge river. I am not saying the concept is flawed... just saying that the current effort is not enough to really make a difference.

I agree, with enough HP it would be effective, the amount of HP to make any difference would be prohibitive as I see it.

If you are at sea and you observe the wake from a large vessel, with - for arguments sake a 100,000 HP engine, you can observe how quickly the bow wave/wake disappears (the energy dissipates due to friction & resistance?) after roughly 1 nm?

Trying to push a massive volume of water would have a similar reaction, you would have to stage propulsion to have move the water quicker - I think ?

[Aussie999]

20 hours ago, impulse said:

 

And your "fact" is based on any kind of math or engineering?   Or just your perception? 

 

Using axial flow pumps to move water around is done all over the world.  Boat propellers are axial flow impellers.  In fact, the photo shows that these particular boats were purpose designed.  The concept is sound, and well accepted.   Whether they have enough HP for the amount of water requires some analysis.  Not just a glance at a photo.

 

If you can show the math that proves it doesn't work, great.  Otherwise you don't know.  And then, it's just bashing something (and someone) you don't understand.

 

I'll repeat my question from a recent, similar thread:

 

If you add 30,000 HP in the downstream direction over a period of 24 hours to a river flowing at a rate of  1 million cubic meters per minute, how much faster will you drain 50,000 acre feet of water than it would drain naturally?

 

What's the ROI of building and maintaining that infrastructure that everyone seems to think they need to spend hundreds of billions of baht on?

 

If you can't answer those questions (showing your math) I'd suggest you let the engineers on location do their jobs without commenting.

Whether the concept is correct, the FACT is, they only move the water about 3m, increasing the water level, behind the pumps.

[impulse]

2 hours ago, Aussie999 said:

Whether the concept is correct, the FACT is, they only move the water about 3m, increasing the water level, behind the pumps.

 

Wrong.  Don't give up your day job.  Your future in hydrodynamics is pretty iffy.

 

Edit:  Here's a hint.  Look up "conservation of energy".  And the concept is related to impulse and momentum.  (how about that?)  Impulse is the (power x the time you apply that power) and momentum is the (mass x velocity).  Add energy to the water, the momentum increases.  The water doesn't "pile up".  It can't.  It moves faster.

 

 

[Aussie999]

On 8/26/2018 at 10:42 AM, impulse said:

 

Wrong.  Don't give up your day job.  Your future in hydrodynamics is pretty iffy.

 

Edit:  Here's a hint.  Look up "conservation of energy".  And the concept is related to impulse and momentum.  (how about that?)  Impulse is the (power x the time you apply that power) and momentum is the (mass x velocity).  Add energy to the water, the momentum increases.  The water doesn't "pile up".  It can't.  It moves faster.

 

 

Wrong, if the water cannot flow freely, in the containment of the river, the the increase in velocity, causes the water the stand, at a higher level, eventually rising above its containment.... wait this is flooding.

 

Very simple to understand, if you put more water, into a container (the river) than what is leaving the "container, the contain eventually fills and overflows.... simple maths.