1,000 Boats To Push Flood Waters From Chao Phraya River

[cloudhopper]

I'll try one last time...

Yes, there is an effect. The effect is not zero, it's just NEAR zero. It is so close to zero that it will have NO MEASURABLE IMPACT on river flow or flood levels whatsoever.

<snip>

Agreed - not zero as some say, but very small.

Agreed not zero. In fact the near zero net effect is actually negative due to the boats obstructing the flow while they are pumping water around in small local circles.

[MaxYakov]

I'll try one last time...

Yes, there is an effect. The effect is not zero, it's just NEAR zero. It is so close to zero that it will have NO MEASURABLE IMPACT on river flow or flood levels whatsoever.

<snip>

Agreed - not zero as some say, but very small.

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be. - Lord Kelvin

If you cannot measure it, you cannot improve it. - Lord Kelvin

In science there is only physics; all the rest is stamp collecting. - Lord Kelvin

Large increases in cost with questionable increases in performance can be tolerated only in race horses and women. - Lord Kelvin

[longway]

That is not the situation we are looking for. If we can "put" a boat inside the discharge tunnel and its propeller provides thrust in the direction of flow, holding the gate opening to be the same, what do you think? Do you think that its flow rate will increase higher than 40m3/s?

Sorry for the temerity to debate a hydrologist but one more experiment.

Let's put a huge diameter pipe along the bottom of the river for 20 meters with a powerful pump inside. I concede that the water level at the upstream intake end will lower and the "tilt" of the river will steepen upstream, increasing the flow. However at the output end of our pump we find that we have increased the river level by an identical amount which flows away equally in all directions, with a slight bias toward downstream. However this is all immediately negated by the newly-formed upstream gradient we create as the humped water at the outlet now has an even steeper and far shorter gravity gradient to follow back upstream into the hole we created at the intake end. Result - localized circular flow in an open system with zero effect on the overall system flow..

Why would the level drop at the upstream end? It would be immediately replaced by 'new' water, the point is to increase water discharge as they need the rivers to drain the flood plains faster.

It will drop there because water is being removed as per ResX explanation above. It is being replaced as you say but the flow of replacement water is coming from the output side of the pump where the water level is even higher, not from upstream. Water in an unpressurized system will only flow when there is a gravity gradient between unequal heights.

I don't think this is what ResX was saying, though I am sure he will let us know one way or the other.

The way I see it, what you describe will only happen if the water upstream of the pipe cannot keep up with the water discharged on the downstream end, and if this is the case then the river is flowing below its maximum discharge rate and there is no point in pumping any water. Here the situation is the opposite, the discharge rate is well below the overflow from the flood plain so it will be replaced at least as quickly as it is removed.

I don't think there will as much of a gradient anyway.

Edited October 19, 2011 by longway

[ResX]

That is not the situation we are looking for. If we can "put" a boat inside the discharge tunnel and its propeller provides thrust in the direction of flow, holding the gate opening to be the same, what do you think? Do you think that its flow rate will increase higher than 40m3/s?

Sorry for the temerity to debate a hydrologist but one more experiment.

Let's put a huge diameter pipe along the bottom of the river for 20 meters with a powerful pump inside. I concede that the water level at the upstream intake end will lower and the "tilt" of the river will steepen upstream, increasing the flow. However at the output end of our pump we find that we have increased the river level by an identical amount which flows away equally in all directions, with a slight bias toward downstream. However this is all immediately negated by the newly-formed upstream gradient we create as the humped water at the outlet now has an even steeper and far shorter gravity gradient to follow back upstream into the hole we created at the intake end. Result - localized circular flow in an open system with zero effect on the overall system flow..

Why would the level drop at the upstream end? It would be immediately replaced by 'new' water, the point is to increase water discharge as they need the rivers to drain the flood plains faster.

It will drop there because water is being removed as per ResX explanation above. It is being replaced as you say but the flow of replacement water is coming from the output side of the pump where the water level is even higher, not from upstream. Water in an unpressurized system will only flow when there is a gravity gradient between unequal heights.

I'm still trying to put cloudhopper statement in the right perspective.

[cloudhopper]

Let's look at it a different way. If the boats or pumps were placed backwards and accelerated some of the water back upstream do you think that would have ANY net effect on the overall flow? Of course not. The physics work the same in either direction.

[metisdead]

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[longway]

Let's look at it a different way. If the boats or pumps were placed backwards and accelerated some of the water back upstream do you think that would have ANY net effect on the overall flow? Of course not. The physics work the same in either direction.

Don't forget that each part of the river has differing carrying capacities. If you can put the boats in the right places it can increase the overall discharge rates.

[MaxYakov]

Let's look at it a different way. If the boats or pumps were placed backwards and accelerated some of the water back upstream do you think that would have ANY net effect on the overall flow? Of course not. The physics work the same in either direction.

Brilliant! How do you propose to measure the effect to support this hypothesis? I just happened to have this handy:

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be. -- Lord Kelvin

[bkkjames]

I have no degree is water flow dynamics or any other fancy name so don't really understand the cool sounding numbers and word being used in here by those of higher education than me.

I just look outside at the river and see reports on the news of the current state of flooding and came to the conclusion it didn't work.

[maidu]

The gov't can't be distracted by all this talk of fluid dynamics and physics. It's not a science based culture, it's hocus pocus based. When Thaksin was PM, he used to travel often to C.Mai to seek advice from a crystal ball gazer there. His whole family and everyone in power positions in Thailand are steeped in hocus pocus.

The boat idea is a placebo. Exhaustive tests have shown placebos work. It's aimed at making the Thai public think something helpful is being done. And it appears to be working as planned! ....the guise, not the purported plan to move the water out to sea faster.

[MaxYakov]

Ran across a Physics forum that was started by the Minister's Chao Phraya pumping experiment and had some interesting posts. Among them was one regarding a Polish jet boat that was capable of being converted to pump water:

Polish firemen use small flat-hull motorboats equipped with special diffusor shaping the stream of water, which may be lowered to the propeller. They were used during floods a year ago not only to drain flooded areas and streets of flooded towns, but also to improve flow in channels, narrows and gaps under bridges. Single such boat pumps 0.5m³/s at high speed. I guess ordinary boat without such diffusor is less efficient, but on other hand may pump more water at lower speeds - which is better

Do you suppose the Minister is placing an order for 75 x 10³ of these Jet Boats/Pumps as we write? Do you suppose the Poles have found a way to prevent the downstream energy from going to zero (disappearing)? Perhaps their Water Deities are more cooperative than Thailand's?

[cloudhopper]

Let's look at it a different way. If the boats or pumps were placed backwards and accelerated some of the water back upstream do you think that would have ANY net effect on the overall flow? Of course not. The physics work the same in either direction.

Brilliant! How do you propose to measure the effect to support this hypothesis? I just happened to have this handy:

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be. -- Lord Kelvin

By conventionally observing any change in river flow rate up and downstream at some far distance outside the local higher speed loop currents surrounding the boats.

[ResX]

I'll try one last time...

Yes, there is an effect. The effect is not zero, it's just NEAR zero. It is so close to zero that it will have NO MEASURABLE IMPACT on river flow or flood levels whatsoever.

<snip>

Agreed - not zero as some say, but very small.

Agreed not zero. In fact the near zero net effect is actually negative due to the boats obstructing the flow while they are pumping water around in small local circles.

As long as no vortexes and turbulence are created downstream it can be sure that the discharge leaving the cross sectional area where we anchor the propellers has increased. When water velocity at that cross sectional area increases then its water level must go down. Other wise conservation of energy will be clearly violated. Google Bernoulli Continuity Equation for more detail. The energy of water at any cross section area is the combination of its potential and kinetic, assuming water is 100% incompressible. Compressibility of water is not an issue at all as far as this discussion is concern. If you increase its kinetic energy then it has to be derived from potential energy. It follows with the water level is going down. This is non debatable scientific fundamental. That is not the main problem why we can't tell whether it works or not.

To me I have two problems to evaluate whether the way it is done right now provides positive impact or near zero. The problems are

(1) After the water that being supplied with kinetic energy loses it kinetic energy it will get back its potential energy. The water level just down stream is actually can be higher than the water level at the cross sectional of interest. In this case it may produce vortexes that circulating near both river banks (near zero velocity region). Or it may not. Probably some might travel downstream and some might produce vortexes. The problem is we don't know such scenario does happen currently and how they address it.

(2) When the water at the cross sectional area of interest gains its kinetic energy its pressure gradient increases. This can be viewed as the manifestation of the river flow has increased . Forget about velocity. It is flow rate that counts. The problem is how far upstream that the discharge can be influenced? I'm sure turbine discharges at Bhumibol and Sirkit cannot be influenced. It doesn't really matter how many boats we use and where we wish to anchor. If it can only effect the area just too small to concern, then what is the point? That is why we have to know control volume (Volume that can be influenced) for each array of boats that we work on. The model of actual control volume is critical to the success of this initiative. The boats have to be arranged according to the desired control volumes. It may have more than one control volume.

[MaxYakov]

Let's look at it a different way. If the boats or pumps were placed backwards and accelerated some of the water back upstream do you think that would have ANY net effect on the overall flow? Of course not. The physics work the same in either direction.

Brilliant! How do you propose to measure the effect to support this hypothesis? I just happened to have this handy:

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be. -- Lord Kelvin

By conventionally observing any change in river flow rate up and downstream at some far distance outside the local higher speed loop currents surrounding the boats.

Go for it! The Ministry of Science and Technology might have some high-accuracy flow meters that they could loan you. They're probably not using them these days.

[JetsetBkk]

I'll try one last time...

Yes, there is an effect. The effect is not zero, it's just NEAR zero. It is so close to zero that it will have NO MEASURABLE IMPACT on river flow or flood levels whatsoever.

<snip>

Agreed - not zero as some say, but very small.

Agreed not zero. In fact the near zero net effect is actually negative due to the boats obstructing the flow while they are pumping water around in small local circles.

No, not negative. Boats obstructing the flow, local circles, eddies, vectors, whatever, are all irrelevant.

I hate using the phrase "common sense" on a Thai forum but, really, where did it all go? (The common sense, I mean, not the water. )

[cloudhopper]

No, not negative. Boats obstructing the flow, local circles, eddies, vectors, whatever, are all irrelevant.

On further reflection I believe you are correct about the obstruction issue Jetset. Equilibrium is dynamically and locally restored as current speeds up around the obstruction and takes the lowest energy path i.e. from the high pressure area immediately upstream into the low pressure area immediately downstream of the obstruction without affecting the overall flow. (Ignoring all entropic, surface wave etc. losses).

And this is the exact same situation we have with a rotating propeller in the water, regardless of how it is oriented with respect to the river flow.

[ResX]

I'll try one last time...

Yes, there is an effect. The effect is not zero, it's just NEAR zero. It is so close to zero that it will have NO MEASURABLE IMPACT on river flow or flood levels whatsoever.

<snip>

Agreed - not zero as some say, but very small.

Agreed not zero. In fact the near zero net effect is actually negative due to the boats obstructing the flow while they are pumping water around in small local circles.

No, not negative. Boats obstructing the flow, local circles, eddies, vectors, whatever, are all irrelevant.

I hate using the phrase "common sense" on a Thai forum but, really, where did it all go? (The common sense, I mean, not the water. )

How the water moves from one point to another on earth surface? It sees pressure gradient, towards which direction is the highest. Then what? I think we have to look in detail the mechanic of water to transport itself. Probably there is something we don't know and all the while we thought we know. Note that, I don't mean to be rude at all.

[BabySun]

Ran across a Physics forum that was started by the Minister's Chao Phraya pumping experiment and had some interesting posts. Among them was one regarding a Polish jet boat that was capable of being converted to pump water:

Polish firemen use small flat-hull motorboats equipped with special diffusor shaping the stream of water, which may be lowered to the propeller. They were used during floods a year ago not only to drain flooded areas and streets of flooded towns, but also to improve flow in channels, narrows and gaps under bridges. Single such boat pumps 0.5m³/s at high speed. I guess ordinary boat without such diffusor is less efficient, but on other hand may pump more water at lower speeds - which is better

Do you suppose the Minister is placing an order for 75 x 10³ of these Jet Boats/Pumps as we write? Do you suppose the Poles have found a way to prevent the downstream energy from going to zero (disappearing)? Perhaps their Water Deities are more cooperative than Thailand's?

He doesnt need to buy water pumps,notice,that they used motorboats with special deffusor.Bangkok have thousands of motorboats already,they just need diffusors.No need to buy!Bangkok is famous for..."copy".

diffusor is simple piece of metal or plastic,anybody can make it.

However! water in ChiaoPraya is special - it doesnt follow laws of physics,energy tends to disapear in it without trace,pumps do not work ,flash floods appear out of nowhere.Truly magic river!

Lets pray instead.

Edited October 19, 2011 by BabySun

[wallswod]

Lets pray instead.

Because Thai science aint going to help.

[TAWP]

Can everybody that insist that this has infact, as stated, had a 5-10% increase on the waters speed please write so?

Getting tedious people having huge Strawman arguments for several pages now - no-one is saying the outcome is exactly 0%.

Many are claiming it has much less impact than the stated '5-10%' and to a too high of a cost for the real effect.

[cloudhopper]

no-one is saying the outcome is exactly 0%.

I am saying the outcome is exactly zero effect.

[Rinrada]

Seem to remember that the navy were buying some old rusty ex German Nuc U Boats think in exchange for bananas or sumit....however looks like it was (asuume they got them) a good deal.

Can use the subs to push away all the water beneath the waves.....

[AleG]

Can everybody that insist that this has infact, as stated, had a 5-10% increase on the waters speed please write so?

Getting tedious people having huge Strawman arguments for several pages now - no-one is saying the outcome is exactly 0%.

Many are claiming it has much less impact than the stated '5-10%' and to a too high of a cost for the real effect.

Assuming the 10% increase figure for 1000 boats and the Science Minister statement that it would take 75000 boats to do the job thoroughly... Then they'll get the water moving at 750% faster rate.

I tell you, they'll hose Malaysia out of the way!

[ResX]

Conservation of momentum & 1000boats debate.

Says a 500kg speed boat with a 100kW engine can attain its maximum speed of 5m/s on the stationary water. Then the engine produces momentum equals to 2500kgm/s. We holds this boats stationary facing the flow of Chao Phraya with its engine in full throttle. The previous 500kgm/s momentum cannot disappear just because you want to win a debate (just joking). Rather it has been transferred to water. So, ideally the speed boat can add speed to 0.5cubic meter per second of water (500kg) by 5m/s. If we put 30 similar speed boats at one cross sectional area of flow path of interest how fast the water speed for that cross section area can be increased? Take the flow rate of the river as 4000m3/s

I think this is quite reasonable question that may help you to get theoretical impact that the boats can give. Let us forget about what happen after that. Anybody wants to try? No prize for the right answer.

Edited October 19, 2011 by ResX

[ResX]

I would encourage believers in the push water out to sea theory to go and take a look at the river. Its huge, more than half a kilometer across. Then go take a look at some of the boats 'pushing'. They aren't running at full throttle.

This is a PR exercise. Wake up.

Wide awake, thanks. The theory works irrespective of the size of the river.

Unfortunately, the Chao Phraya is so big that the effect will be very small.

Hold a minute. If the water can travel there hundreds of km from upstream without energy being supplied, does it need that much energy to move after all? As Bhumibol operators. Almost every day night the "push" 75-159m3/s of water to enter their dam over the last few years. Hopefully they didn't do that during the recent heavy downpour.

Edited October 19, 2011 by ResX

[MaxYakov]

Seem to remember that the navy were buying some old rusty ex German Nuc U Boats think in exchange for bananas or sumit....however looks like it was (asuume they got them) a good deal.

Can use the subs to push away all the water beneath the waves.....

Flood refugee housing would be a more practical use, capacity aside.

[cloudhopper]

I think this is quite reasonable question that may help you to get theoretical impact that the boats can give. Let us forget about what happen after that.

I imagine the science minister also wants to forget about what happens after that. But what does in fact happen is that whatever energy is imparted to the water causes it to bulge up and out in all directions and return to the low pressure area in front of the propeller by the lowest energy path. Just as it would on a lake. And as you have pointed out a river is nothing but a tilted lake with a drain at one end and a source at the other.

[GentlemanJim]

ResX and all the others insisting on trying to show numbers with your very very limited understanding of the conservation of energy and conservation of momentum in this particular case. Will you all pleeeeeease give it up. It does not matter if you can prove that the overall result got 1000 m3 of water out of the river mouth .0000001 knot quicker than it originally would have done without the boats. The practical FACT is that in terms of the crisis and the effort to prevent flooding the effort is achieving absolutely NOTHING! All of your attempts at crunching basic numbers is producing figures that are totally meaningless, and do nothing other than exercise your brains in the same way doing a few suduko puzzles would do. So please spare us all from the meaningless drivel that is coming from the keyboards. It is getting really tiresome.

MaxYakov

often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be. -- Lord Kelvin

The key phrase is 'measure'. In this case it does not matter what the numbers are, because they are so small that you cannot measure them to have any meaningful effect, and when Lord Kelvin stated this he was researching into a completely different ball game.

[AleG]

Conservation of momentum & 1000boats debate.

Says a 500kg speed boat with a 100kW engine can attain its maximum speed of 5m/s on the stationary water. Then the engine produces momentum equals to 2500kgm/s. We holds this boats stationary facing the flow of Chao Phraya with its engine in full throttle. The previous 500kgm/s momentum cannot disappear just because you want to win a debate (just joking). Rather it has been transferred to water. So, ideally the speed boat can add speed to 0.5cubic meter per second of water (500kg) by 5m/s. If we put 30 similar speed boats at one cross sectional area of flow path of interest how fast the water speed for that cross section area can be increased? Take the flow rate of the river as 4000m3/s

I think this is quite reasonable question that may help you to get theoretical impact that the boats can give. Let us forget about what happen after that. Anybody wants to try? No prize for the right answer.

The issue is that a propeller downwash is not a laser beam, it diffuses and disperses in the turbulent flow, so the thrust vector behind the propeller is pointing forward but down the river its going all over the place, not just downstream.

It's like trying to push a rope in one direction, it just doesn't go anywhere.

Earlier someone was comparing the boats with using pump, the difference that seemed to escape that particular poster is that a pump usually pumps through a pipe or hose from one point to another, so there's only one way the fluid can go, along the pipe, and it doesn't spill along the way.

On a river with insignificant propellers (relative to the size of the river) the water flow pushed back will sooner than later form eddies and waves that will amount to the water moved up and down, sideways and back and forth, the net downriver "thrust" would be negligible.

Besides, in your analysis you forget the boat's drag in the water, for a boat not accelerating, if you subtract the drag to the thrust you get exactly 0.

If you want to play tricks by accelerating against the current upstream and then floating downstream to repeat the process, any gains in momentum in the river flow by the propeller accelerating the water will be negated by the momentum transferred back to the boat as it stops and begins to be carried back downstream.

[longway]

The boats are moored