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


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#776 ResX

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Posted 2011-10-21 17:42:21



If we allow flood water to flow down naturally it will follow free surface flow equation Q= cLH^1.5. Q is volumetric flow rate, cL empirical constant and H height of water column above riverbed. Or you want to use Manning equation.... This is actually the natural way water can transport itself given even a slight pressure gradient for it to move. It builds up itself layer by layer to increase H so that Q increases. Allow it undisturbed, the higher the flood flow the higher it builds up H. This nature of water flow that makes the flood looks the way we usually see.
,

If you observe free surface flow equation you can see that the water velocity higher on the top and zero at the bottom. If this equation governs out going discharge of a a bottleneck cross section the flood plain just upstream will be flooded. The water velocity is almost zero and hydraulic gradient between the bottle neck section and upstream end of the "pond" has been created is very small. It may take a long time before the this pond to be emptied. The nature of this discharge formula in fact is used for flood control for a very big reservoir (surprisingly your Bhumibol does not have this kind of flood control gate-as far as I can see-This is one of the reasons why the flood is soooo big) to slow down water release to downstream. But you don't want this equation dominates at downstream. What shall you do? Let we make up some numbers for one of the bottle necks.

Q= 4500m3/s. H =5m. Then cL 866. That makes Q=866H^1.5. Assuming the flood plain water surface area 5km2. Then we have about 25million cubic meter of water that need to be drained out based on that equation. How we can make a 25million m3 above faster? Just put t pump and suck the water out via the bottle neck. So the discharge equation for the pond becomes

Q = 866H^1.5 + pump discharge. Then the pond water level is going down faster. Or just force the water out using boat propeller. The equation becomes:

Q= 866H^1.5 + propeller discharge.

Either one the discharge will be higher. As long as the flood plain of this kind that propellers can provide meaningful impact. Otherwise .....



I am loving this semi-useless thread but I am also very very stupid, i am not sure if there is a conection :) HOWEVER, in your mathmatics and phyics i just have one question. well probably 2.

you, regardless of the amount, state that the exit for the water is a bottle neck. you assume that exit capacity to be Q
you now partially block that exit with a static mounted propeller.
therefore add resistance to the natural flow lets call that reduction amount Y
so regardless of the efficiency of the new propeller unit, your equasion cant be right, because you have not deducted the loss Y.

so wouldnt it be.. Q-y+ propeller discharge ( which i still think is a small amount)??

at the end of the day I admit to being a complete idiot so have probable misread all of this and need to go back to page one :)


Nice remark. I will right back soon.


1. Yes if you put the propeller static there then you increase resistance. But if we put energy to propeller it rotates. What the impeller of the propeller does is it provides water with momentum to move across its impeller. Thus the water travels faster. There is NO different with transfer pump concept. We provide water with kinetic energy then it moves faster.

Many people here have conceptually wrong view by believing that only the water near the propeller can be moved. The water movement vector naturally (forget about any propeller) parabolic in nature if view from the top of a straight straight river. For the river of equal depth and symmetry around its center the maximum velocity is achieved exactly at the center of the river. Near both of the river the banks that is a phenomenon called "a boundary layer effect". Water velocity is theoretically zero or close to zero.

If you look from site maximum water velocity occurs at around 0.7 X Depth (Can remember exactly but I promised I'm not far off) . Why I'm telling you this? There is theory that so called a shear stress & boundary of water. In our case that theory explains why the water just near the bank tries to maintain its zero velocity due to friction with river bank. The next layer of water tries to do so but there is not enough friction force to hold its position. Thus it travels slightly higher than zero. At the center, boundary layer effect has the least. Therefore the water travels at the maximum velocity for the given pressure gradient. Similar thing happens looking from side of the flow. Since boundary layer friction between air and water is smaller than of any solid wall (riverbed) therefore its maximum velocity does not lie symmetry with the dept.

Similar thing happens when you try to drag the water at any section to move. The water nearby will be dragged too but it will not move at the same velocity as the section you drag. It may form a very "thin" shaped parabola. I'm not really sure whether I'm right about it shape. But I can assure you I'm conceptually right This does not in any way violate conservation of energy since the some of kinetic energy being supplied to water at any point shall be equal to sum of kinetic energy for all tiny masses of water + losses.

Google parabolic water flow (image)

#777 MaxYakov

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Posted 2011-10-21 17:53:46

I just had to submit this to Mythbusters.
http://community.dis...6/m/78219326901

Would love to see them rip this idea to shreds in a "scientific" way!

Me too. They've done some great work using empirical approaches. You won't see a lot of theoretical physics math in their episodes - bad for ratings, I'd imagine. I'd bet also they would do just as I did to get a feel for the problem, grasp the scale and the complexity of measuring the outcome on the Chao Phraya (not to mention the logistics and other obvious problems of filming in Thailand) and decide to reproduce it on a smaller scale ... in a California irrigation canal, perhaps.

#778 Thaddeus

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Posted 2011-10-21 18:18:04



The reason I am not willing to get involved is that you cannot simplify the problem.

I believe that you can simplify the problem.

Fire a hose pipe at a brick wall and watch what happens, the water will go in all directions, eventually down being the only one.

The river is the hose pipe, the brick wall is the very very large mass of water that they are trying to force more water into.

Most of the number juggling performed by some protagonist on this thread assume that the linear movement of the water always has somewhere to go..... which it quite plainly doesn't.


Unfortunately that so called "brick" moves to sea mouth EVEN without any boat to help. If it can move without any outside help at all why it is so difficult to believe that it will move even faster if additional force is induced along the direction of it moves.

If we push a bus with 40 passengers, alone, then I doubt many or us here manage to make it move. If the bus just travels 1m/s and we are trying to push to make it travel at 2m/s do you think it is beyond reached?

There is an old theory about inertia.

Making the same basic mistake again, you cannot make a comparison with pushing a bus. Pushing the bus has little or no resistance to it, air just gets out of the way.

Trying to move water into the sea by force, is not the same at all.

Of course water flows into the sea all the time, but at the rate it will accept, if it is moving horizontally at sea level.

#779 longway

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Posted 2011-10-21 18:25:21

^ If it flows in all the time, its not like a brick wall at all then.

The river is flowing into the sea by force all the time.

#780 ResX

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Posted 2011-10-21 18:37:33




The reason I am not willing to get involved is that you cannot simplify the problem.

I believe that you can simplify the problem.

Fire a hose pipe at a brick wall and watch what happens, the water will go in all directions, eventually down being the only one.

The river is the hose pipe, the brick wall is the very very large mass of water that they are trying to force more water into.

Most of the number juggling performed by some protagonist on this thread assume that the linear movement of the water always has somewhere to go..... which it quite plainly doesn't.


Unfortunately that so called "brick" moves to sea mouth EVEN without any boat to help. If it can move without any outside help at all why it is so difficult to believe that it will move even faster if additional force is induced along the direction of it moves.

If we push a bus with 40 passengers, alone, then I doubt many or us here manage to make it move. If the bus just travels 1m/s and we are trying to push to make it travel at 2m/s do you think it is beyond reached?

There is an old theory about inertia.

Making the same basic mistake again, you cannot make a comparison with pushing a bus. Pushing the bus has little or no resistance to it, air just gets out of the way.

Trying to move water into the sea by force, is not the same at all.

Of course water flows into the sea all the time, but at the rate it will accept, if it is moving horizontally at sea level.


How do you think Bhumibol & Sirkit dams discharged out all the flood water they have collected lately. Why the dams did not flooded?

#781 WarpSpeed

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Posted 2011-10-21 18:46:57


The reason I am not willing to get involved is that you cannot simplify the problem.

I believe that you can simplify the problem.

Fire a hose pipe at a brick wall and watch what happens, the water will go in all directions, eventually down being the only one.

The river is the hose pipe, the brick wall is the very very large mass of water that they are trying to force more water into.

Most of the number juggling performed by some protagonist on this thread assume that the linear movement of the water always has somewhere to go..... which it quite plainly doesn't.

You should try referencing Mythbusters season 8 to see the energy absorption capabilities of water versus concrete or in this case brick, it makes no difference..

#782 WarpSpeed

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Posted 2011-10-21 19:04:39



Agree with WarpSpeed. Additionally, water 'flows into a 3D loop back into the depression upstream of the intake'? Are we talking meteorology here? Would that be tropical depression? The law of inertia have been suspended as well to support this? The accelerated water has mass, velocity and direction. If it didn't, boats could not be propelled efficiently, or at all.

I've been out of it folks due to a sprained ankle. Have been loosely following things and have been working on my energy model which is based on an ideal situation, to reduce nattering, what I consider, unimportant details. I don't want to post all the details/math in this post, but will give a summary:

500 boats delivering 1000 HP at propeller output (not at shaft input and addresses ONLY the Chao Phraya river - not the other two).
This simplifies/eliminates distractions such as fuel-to-engine efficiency, propeller efficiency, etc which I consider
to be a separate issues.

Recent flow-rate for Chao Phraya at 420 x 106 m3/day

Speed of Chao Phraya river used: 1 m/second - This is an estimate and, perhaps, too low/slow.
Changes in this value are a square factor by the kinetic energy formula and will have a large affect the total KE of the river
and the total KE percentage increase by the total 500,000 HP (at propeller output, not engine HP).

========> Kinetic energy of river is increased by about 15%

Note: If most of the kinetic energy added is directed with the current flow and there is minimal loss of energy due to transformation to heat and energy does not 'disappear', then (since the mass of the water has not changed) the energy increase of the river water can only be manifested only as a higher velocity of the river water.

Incidentally, given the above parameters, several of you could apply the KE formula to validate the 15% result. HP-to=Joules conversion that I used is: 1 HP = 746 Joules (from an internet converter).

500,000 HP, directly into the Chao Phraya has got to have some effect, wouldn't you think? I let you folks kick around what that effect would/might be.

Comments?


You are missing several factors, most importantly what I pointed out earlier: most of the boats used on this operation where in mid river, not moored to anything, therefore as long as they were not accelerating the thrust from the propeller is a force equal and opposite to the drag of the hull, so the net sum of force and energy delivered to the flow of water is ZERO. In simple terms the boat is pushing as much water as it is slowing down.

Second, most of the boats used are nowhere close to 1000HP in engine power, not even close. Those small river "buses", in my uninformed opinion, shouldn't have more than 100HP at most, although someone with actual data may want to chime in.

Third, the vector of the thrust at the propeller point is rearwards, but it doesn't stay that way for long due to turbulence, if it would then you wouldn't see the water churning around behind a propeller, it would be a linear flow. Some of the energy is vectored downriver, most of it is diverted in all other directions. I would guess that the net result, after you subtract the "useful" vector from the hull drag in the water you end up with a pittance of benefit out of the effort.

Fourth the Chao Phraya meanders a lot, so even if the flow from the propeller would follow the thrust line for a significant distance, then it would only end up lapping some shore or another.

Fifth the water pushed back from the propellers would find resistance from slower water in the river flow, since you can't compress water (meaningfully) the way the resistance manifests is in a local rise in the water level which will try to settle in all directions, not just down the thrustline, so you have a bulge behind the prop that spreads back, to the sides and also forward. This contributes called recirculation or a vortex ring state, where the water (or fluid) assumes a donut shaped flow around a propeller, reducing efficiency significantly. (I get to suffer that phenomena regulary flying RC helicopters). The higher the difference in speed between the propeller downwash and the surrounding fluid the more likely it is to develop recirculation, thus the anchored boats going full gas should be suffering a significant loss of efficiency from this.

I should have stressed that the 15% is for an 'ideal' situation. The energy that may contribute to increased flow will only be less than that under all other circumstances. All other factors can only subtract from that value. As we all suspect, the actual effect is probably much, much less than 15%. The main reason is that the Minister's pumping fleet probably doesn't come anywhere near the size and power of this 'ideal'. Also, the velocity of the Chao Phraya may be more than the value used in the calculation that produced the 15%.

1) All boats I've seen on Thai TV have been obviously moored. Those not obviously moored had zero speed relative to land, indicating that the were somehow also moored. This should be common knowledge by now. I agree that if the boats are NOT moored it is an entirely different physics problem.

Are we working on the same physics problem?

2) Again, this is an 'ideal' situation, using only the 500 boat number from his claim. Whether the Minister's 500 boats are equivalent is indeterminable and not even important to this model. There is also a claim that the river(s) flow was increased by 50 x 106 m3/day with some number of boats. That claim is also not part of this model. However, the model could be used as a starting point to establish the increased flow under these 'ideal' (not necessarily realistic) conditions.

Perhaps you can give us some insight w/r to the Minister's actual pumping fleet. If it is fewer than 500@1000 HP (at prop output), which it probably is, then this model could be adjusted accordingly with a proportionate lowering of the 15% 'ideal' result.

3) If there are materially untoward energy transformations due to prop wash turbulence, then perhaps that can be removed from this model through various means (like substituting a jet boats which may have less turbulence). Otherwise, that effect of this turbulence should be quantified and the 15% value adjusted downward. Can you quantify it? Hull drag is not a factor since the boats are moored for this model. The model's boats and the Minister's boats are effectively floating (but not moving) water pumps.

Can you quantify the energy transformations from turbulence that would reduce the downstream velocity of the water?

4) This is an interesting subject area which ResX and I were attempting to clarify the other evening. How, exactly, the prop wash water interacts with the river water, both immediately and over time, was not firmly established. My gut feeling is that energy transfer occurs between the accelerated water and the river water at some identifiable rate due to friction. I do not have values for that rate, but if the transfer occurs completely, before the water reaches the Bay, then all we're talking about is accelerated river water where the accelerated water cannot be easily differentiated from the non-accelerated river water.

Do you have anything to contribute in this area except the lapping of water on the river's shores? Remember that in spite of the direction changes and any 'lapping', the river is still currently delivering 420 x 106 m3/day to the Bay.

5) Again, this model removes propeller inefficiencies from the calculations, not the turbulence inefficiencies. Those would also, like anything and everything else, deduct from the 15% calculated under ideal model. Can you verify the prop wash recirculation beyond 'more likely'? Remember that the prop wash is operating under physical laws of inertia and is moving at a relatively high velocity.

Can you quantify these inefficiencies and cite references?

Much Appreciate Your Comments

Sir I commend your efforts and patience I couldn't be arsed to distinguish that rubbish post. Had sand bags to locate and put up, still didn't get enough yet :( , hope there's another chance tomorrow, the water's coming up pretty quickly now.. Also going to use some rice bags as well in certain situations in the house to block off the toilets and sinks for example.

#783 MaxYakov

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Posted 2011-10-21 19:14:14



You are missing several factors, most importantly what I pointed out earlier: most of the boats used on this operation where in mid river, not moored to anything, therefore as long as they were not accelerating the thrust from the propeller is a force equal and opposite to the drag of the hull, so the net sum of force and energy delivered to the flow of water is ZERO. In simple terms the boat is pushing as much water as it is slowing down.

Second, most of the boats used are nowhere close to 1000HP in engine power, not even close. Those small river "buses", in my uninformed opinion, shouldn't have more than 100HP at most, although someone with actual data may want to chime in.

Third, the vector of the thrust at the propeller point is rearwards, but it doesn't stay that way for long due to turbulence, if it would then you wouldn't see the water churning around behind a propeller, it would be a linear flow. Some of the energy is vectored downriver, most of it is diverted in all other directions. I would guess that the net result, after you subtract the "useful" vector from the hull drag in the water you end up with a pittance of benefit out of the effort.

Fourth the Chao Phraya meanders a lot, so even if the flow from the propeller would follow the thrust line for a significant distance, then it would only end up lapping some shore or another.

Fifth the water pushed back from the propellers would find resistance from slower water in the river flow, since you can't compress water (meaningfully) the way the resistance manifests is in a local rise in the water level which will try to settle in all directions, not just down the thrustline, so you have a bulge behind the prop that spreads back, to the sides and also forward. This contributes called recirculation or a vortex ring state, where the water (or fluid) assumes a donut shaped flow around a propeller, reducing efficiency significantly. (I get to suffer that phenomena regulary flying RC helicopters). The higher the difference in speed between the propeller downwash and the surrounding fluid the more likely it is to develop recirculation, thus the anchored boats going full gas should be suffering a significant loss of efficiency from this.

I should have stressed that the 15% is for an 'ideal' situation. The energy that may contribute to increased flow will only be less than that under all other circumstances. All other factors can only subtract from that value. As we all suspect, the actual effect is probably much, much less than 15%. The main reason is that the Minister's pumping fleet probably doesn't come anywhere near the size and power of this 'ideal'. Also, the velocity of the Chao Phraya may be more than the value used in the calculation that produced the 15%.

1) All boats I've seen on Thai TV have been obviously moored. Those not obviously moored had zero speed relative to land, indicating that the were somehow also moored. This should be common knowledge by now. I agree that if the boats are NOT moored it is an entirely different physics problem.

Are we working on the same physics problem?

2) Again, this is an 'ideal' situation, using only the 500 boat number from his claim. Whether the Minister's 500 boats are equivalent is indeterminable and not even important to this model. There is also a claim that the river(s) flow was increased by 50 x 106 m3/day with some number of boats. That claim is also not part of this model. However, the model could be used as a starting point to establish the increased flow under these 'ideal' (not necessarily realistic) conditions.

Perhaps you can give us some insight w/r to the Minister's actual pumping fleet. If it is fewer than 500@1000 HP (at prop output), which it probably is, then this model could be adjusted accordingly with a proportionate lowering of the 15% 'ideal' result.

3) If there are materially untoward energy transformations due to prop wash turbulence, then perhaps that can be removed from this model through various means (like substituting a jet boats which may have less turbulence). Otherwise, that effect of this turbulence should be quantified and the 15% value adjusted downward. Can you quantify it? Hull drag is not a factor since the boats are moored for this model. The model's boats and the Minister's boats are effectively floating (but not moving) water pumps.

Can you quantify the energy transformations from turbulence that would reduce the downstream velocity of the water?

4) This is an interesting subject area which ResX and I were attempting to clarify the other evening. How, exactly, the prop wash water interacts with the river water, both immediately and over time, was not firmly established. My gut feeling is that energy transfer occurs between the accelerated water and the river water at some identifiable rate due to friction. I do not have values for that rate, but if the transfer occurs completely, before the water reaches the Bay, then all we're talking about is accelerated river water where the accelerated water cannot be easily differentiated from the non-accelerated river water.

Do you have anything to contribute in this area except the lapping of water on the river's shores? Remember that in spite of the direction changes and any 'lapping', the river is still currently delivering 420 x 106 m3/day to the Bay.

5) Again, this model removes propeller inefficiencies from the calculations, not the turbulence inefficiencies. Those would also, like anything and everything else, deduct from the 15% calculated under ideal model. Can you verify the prop wash recirculation beyond 'more likely'? Remember that the prop wash is operating under physical laws of inertia and is moving at a relatively high velocity.

Can you quantify these inefficiencies and cite references?

Much Appreciate Your Comments

Sir I commend your efforts and patience I couldn't be arsed to distinguish that rubbish post. Had sand bags to locate and put up, still didn't get enough yet :( , hope there's another chance tomorrow, the water's coming up pretty quickly now.. Also going to use some rice bags as well in certain situations in the house to block off the toilets and sinks for example.

Thank you so much (my ankle is only part of my pain). I hope it goes well. Should I have the Minister send over a boat or two?

Still waiting here in Nana for our 'fair share'.

Edited by MaxYakov, 2011-10-21 19:41:03.


#784 WarpSpeed

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Posted 2011-10-21 19:14:56

I just had to submit this to Mythbusters.
http://community.dis...6/m/78219326901

Would love to see them rip this idea to shreds in a "scientific" way!

I would too just like the misconception people had about the plane that couldn't take off from a platform traveling in the opposite direction. I think as in that case those here thinking it has no effect are going to find themselves speechless or gobsmacked as the English would say.

Edited by WarpSpeed, 2011-10-21 19:15:22.


#785 WarpSpeed

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Posted 2011-10-21 19:22:53




The reason I am not willing to get involved is that you cannot simplify the problem.

I believe that you can simplify the problem.

Fire a hose pipe at a brick wall and watch what happens, the water will go in all directions, eventually down being the only one.

The river is the hose pipe, the brick wall is the very very large mass of water that they are trying to force more water into.

Most of the number juggling performed by some protagonist on this thread assume that the linear movement of the water always has somewhere to go..... which it quite plainly doesn't.


Unfortunately that so called "brick" moves to sea mouth EVEN without any boat to help. If it can move without any outside help at all why it is so difficult to believe that it will move even faster if additional force is induced along the direction of it moves.

If we push a bus with 40 passengers, alone, then I doubt many or us here manage to make it move. If the bus just travels 1m/s and we are trying to push to make it travel at 2m/s do you think it is beyond reached?

There is an old theory about inertia.

Making the same basic mistake again, you cannot make a comparison with pushing a bus. Pushing the bus has little or no resistance to it, air just gets out of the way.

:w00t: No resistance to moving a bus?? Surely you jest? To start with there's rolling resistance from several huge tires far more then any resistance then any water will ever create. I leave it at just that but there is resistance in every one of the contacts points of the axles, the brakes and so on..

#786 TommyDee

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Posted 2011-10-21 20:11:14


Say there ResX just curious what university?

edit - sorry, which university?


I'm not an academician. Not in Thailand.


Let me try to build up a simple idealized model regarding the subject we are currently discussing. We know that the current flow of CP river is 420 X 10^6m3 (4861m3/s). Assuming we can build a surface water tunnel (2km wide) right from Bhumibol dam up to the river mouth. The total distance is 500km (I just made up a number). At the Bhumibol side, water level elevation is 250m above sea level. Near river water level elevation is 2 m from the upper flow level and exactly zero from the riverbed. The water velocity for full laminar flow is 1.22m/s (it is definitely laminar anyway) . Don't worry I have calculated it for you the water velocity is correct. Note that too that the only driving force that that moves a huge amount of water is PRESSURE GRADIENT, assuming you can take for granted gravitational acceleration is there. :D.

I ask you a question: Why the water moves from the Bhumibol dam to its river mouth? If you answer because of the gravity, then I will give you half of the scores. Why? Because the water inside the glass of the Bhumibol staff does not make up the river mouth. The right answer is because of the present of pressure gradient 250 meter for every 500km horizontal distance (Hydraulic gradient =0.5m/km) and nothing stops the water to flow down due to gravitational force.

We let the water flow undisturbed. It flows down in harmony at the speed of 1.22m/s as long as 4,861m3/s is supplied by the Bhumibol dam. Let us start it from here the effect adding kinetic energy to the flow. First experiment. Let put the pump at the outlet. Let us assume the pump has discharge capability of 1000m3/s. I don't to put a boat for this test to prevent the other the other debated subject to enter into this conceptual discussion. What will happen next?

Anybody wish to try? Note that the actual scenario is definitely not as simple as this idealized model. But the Physics laws do not change just because the system of equations become more complex.

No prize for the right answer.

Hint: Please don't solve using the second order differential equation and using Navier -Stokes Equations. They are not required to solve this type of problem.





I did it with my fingers and only one foot. the answer is 4




right?


apple in the email sir xxx

#787 BuckarooBanzai

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Posted 2011-10-21 20:46:46

Just thought I would say I am still here observing the flow. I have been so gobsmacked with the new physics as presented by those that have posted about 80% of the glorious discovery of new Thai Physics that I am just speechless. I am also speechless because I sprained my jaw muscles because of excessive laughter.

With ResX quoting laminar flow, speed limits of water on a slope, and parabolic water flow, I lost all sense of reality and also lost any desire to re-post what I have posted in the past due to an epidemic of deaf ear syndrome.

I believe repetition does not prove what is true and what is balderdash - unlike those that wish to re-post again and again what they perceive to be true.

#788 ResX

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Posted 2011-10-21 21:30:43




The reason I am not willing to get involved is that you cannot simplify the problem.

I believe that you can simplify the problem.

Fire a hose pipe at a brick wall and watch what happens, the water will go in all directions, eventually down being the only one.

The river is the hose pipe, the brick wall is the very very large mass of water that they are trying to force more water into.

Most of the number juggling performed by some protagonist on this thread assume that the linear movement of the water always has somewhere to go..... which it quite plainly doesn't.


Unfortunately that so called "brick" moves to sea mouth EVEN without any boat to help. If it can move without any outside help at all why it is so difficult to believe that it will move even faster if additional force is induced along the direction of it moves.

If we push a bus with 40 passengers, alone, then I doubt many or us here manage to make it move. If the bus just travels 1m/s and we are trying to push to make it travel at 2m/s do you think it is beyond reached?

There is an old theory about inertia.

Making the same basic mistake again, you cannot make a comparison with pushing a bus. Pushing the bus has little or no resistance to it, air just gets out of the way.

Trying to move water into the sea by force, is not the same at all.

Of course water flows into the sea all the time, but at the rate it will accept, if it is moving horizontally at sea level.


Have you seen how a series of axial fans are used to discharge out exhaust gasses a from road tunnel? I have a few photos to share. Unfortunately I don't know how to attach them with my post. If you are interested to see this is the link. If the principle works for air why not it works for water? Just curious.

http://www.howden.co...ion/default.htm

#789 BuckarooBanzai

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Posted 2011-10-21 21:36:28

Have you seen how a series of axial fans are used to discharge out exhaust gasses a from road tunnel? I have a few photos to share. Unfortunately I don't know how to attach them with my post. If you are interested to see this is the link. If the principle works for air why not it works for water? Just curious.
http://www.howden.co...ion/default.htm


A tunnel has laminar flow and intermittent input of energy will create a current that will go the length of the enclosed tunnel. This does not relate to the flow of an open system like a flood plane.

#790 ResX

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Posted 2011-10-21 21:39:09



Say there ResX just curious what university?

edit - sorry, which university?


I'm not an academician. Not in Thailand.


Let me try to build up a simple idealized model regarding the subject we are currently discussing. We know that the current flow of CP river is 420 X 10^6m3 (4861m3/s). Assuming we can build a surface water tunnel (2km wide) right from Bhumibol dam up to the river mouth. The total distance is 500km (I just made up a number). At the Bhumibol side, water level elevation is 250m above sea level. Near river water level elevation is 2 m from the upper flow level and exactly zero from the riverbed. The water velocity for full laminar flow is 1.22m/s (it is definitely laminar anyway) . Don't worry I have calculated it for you the water velocity is correct. Note that too that the only driving force that that moves a huge amount of water is PRESSURE GRADIENT, assuming you can take for granted gravitational acceleration is there. :D.

I ask you a question: Why the water moves from the Bhumibol dam to its river mouth? If you answer because of the gravity, then I will give you half of the scores. Why? Because the water inside the glass of the Bhumibol staff does not make up the river mouth. The right answer is because of the present of pressure gradient 250 meter for every 500km horizontal distance (Hydraulic gradient =0.5m/km) and nothing stops the water to flow down due to gravitational force.

We let the water flow undisturbed. It flows down in harmony at the speed of 1.22m/s as long as 4,861m3/s is supplied by the Bhumibol dam. Let us start it from here the effect adding kinetic energy to the flow. First experiment. Let put the pump at the outlet. Let us assume the pump has discharge capability of 1000m3/s. I don't to put a boat for this test to prevent the other the other debated subject to enter into this conceptual discussion. What will happen next?

Anybody wish to try? Note that the actual scenario is definitely not as simple as this idealized model. But the Physics laws do not change just because the system of equations become more complex.

No prize for the right answer.

Hint: Please don't solve using the second order differential equation and using Navier -Stokes Equations. They are not required to solve this type of problem.





I did it with my fingers and only one foot. the answer is 4




right?


apple in the email sir xxx



Good answer Sir. You get it right. I will raise the stake now since you a good. How many pumps of similar capacity to bring down water level inside the tunnel for the first 4km from river mouth and where the pumps should be placed?:D

Edited by ResX, 2011-10-21 21:47:51.


#791 ResX

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Posted 2011-10-21 21:46:47


Have you seen how a series of axial fans are used to discharge out exhaust gasses a from road tunnel? I have a few photos to share. Unfortunately I don't know how to attach them with my post. If you are interested to see this is the link. If the principle works for air why not it works for water? Just curious.
http://www.howden.co...ion/default.htm


A tunnel has laminar flow and intermittent input of energy will create a current that will go the length of the enclosed tunnel. This does not relate to the flow of an open system like a flood plane.


In physics that is not a close conduit relative to those two fans. The diameter of the tunnel is vastly bigger than those two fans. You can't say this as an enclosed tunnel as far as the two fans are concern. Even if you think it is a closed system, the river cross sectional area also similar to this tunnel since it is enclosed by two banks and a riverbed.

#792 BuckarooBanzai

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Posted 2011-10-21 22:01:09



Have you seen how a series of axial fans are used to discharge out exhaust gasses a from road tunnel? I have a few photos to share. Unfortunately I don't know how to attach them with my post. If you are interested to see this is the link. If the principle works for air why not it works for water? Just curious.
http://www.howden.co...ion/default.htm


A tunnel has laminar flow and intermittent input of energy will create a current that will go the length of the enclosed tunnel. This does not relate to the flow of an open system like a flood plane.


In physics that is not a close conduit relative to those two fans. The diameter of the tunnel is vastly bigger than those two fans. You can't say this as an enclosed tunnel as far as the two fans are concern. Even if you think it is a closed system, the river cross sectional area also similar to this tunnel since it is enclosed by two banks and a riverbed.


The difference is in laminar and turbulent flow which you cannot seem to get a handle on.

With a flood bypass channel, which is laminar in nature because it is smooth without obstructions, it is often necessary to slow down the speed of the river because in a laminar system the water continues to accelerate due to gravity.

But in a river and flood plane situation energy is expended in all directions and no significant velocity is achieved. A meandering turbulent river has a great deal of resistance to the flow of water from point A to point B. Trying to speed up the river is the same a using a fan to speed up the wind!

A laminar channel has no such resistance. Do you begin to see the difference?

Edit - as to the tunnel it is indeed a closed system and the fans can propagate the energy downstream so to speak. This is not the same as the CP river!

Edited by BuckarooBanzai, 2011-10-21 22:03:36.


#793 ResX

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Posted 2011-10-21 22:02:39




The reason I am not willing to get involved is that you cannot simplify the problem.

I believe that you can simplify the problem.

Fire a hose pipe at a brick wall and watch what happens, the water will go in all directions, eventually down being the only one.

The river is the hose pipe, the brick wall is the very very large mass of water that they are trying to force more water into.

Most of the number juggling performed by some protagonist on this thread assume that the linear movement of the water always has somewhere to go..... which it quite plainly doesn't.


Unfortunately that so called "brick" moves to sea mouth EVEN without any boat to help. If it can move without any outside help at all why it is so difficult to believe that it will move even faster if additional force is induced along the direction of it moves.

If we push a bus with 40 passengers, alone, then I doubt many or us here manage to make it move. If the bus just travels 1m/s and we are trying to push to make it travel at 2m/s do you think it is beyond reached?

There is an old theory about inertia.

Making the same basic mistake again, you cannot make a comparison with pushing a bus. Pushing the bus has little or no resistance to it, air just gets out of the way.

Trying to move water into the sea by force, is not the same at all.

Of course water flows into the sea all the time, but at the rate it will accept, if it is moving horizontally at sea level.


Sir... Water cannot flow horizontally if no energy is supplied and it has zero momentum. I think you are confusing with your own premise. First you said the water can move horizontally. Then you said the water cannot be made to move horizontally by any mean. Which one is which?

#794 GentlemanJim

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Posted 2011-10-21 22:08:26

@ BuckarooBanzai

Mate, if you engage these people you will go mad I promise. They are making it up as they go along and laughing at the reaction.


Mods, can this be transported to the Farang Pub Forum yet?

More of the threads Four Musketeers!




#795 ResX

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Posted 2011-10-21 22:08:40




Have you seen how a series of axial fans are used to discharge out exhaust gasses a from road tunnel? I have a few photos to share. Unfortunately I don't know how to attach them with my post. If you are interested to see this is the link. If the principle works for air why not it works for water? Just curious.
http://www.howden.co...ion/default.htm


A tunnel has laminar flow and intermittent input of energy will create a current that will go the length of the enclosed tunnel. This does not relate to the flow of an open system like a flood plane.


In physics that is not a close conduit relative to those two fans. The diameter of the tunnel is vastly bigger than those two fans. You can't say this as an enclosed tunnel as far as the two fans are concern. Even if you think it is a closed system, the river cross sectional area also similar to this tunnel since it is enclosed by two banks and a riverbed.


The difference is in laminar and turbulent flow which you cannot seem to get a handle on.

With a flood bypass channel, which is laminar in nature because it is smooth without obstructions, it is often necessary to slow down the speed of the river because in a laminar system the water continues to accelerate due to gravity.

But in a river and flood plane situation energy is expended in all directions and no significant velocity is achieved. A meandering turbulent river has a great deal of resistance to the flow of water from point A to point B. Trying to speed up the river is the same a using a fan to speed up the wind!

A laminar channel has no such resistance. Do you begin to see the difference?

Edit - as to the tunnel it is indeed a closed system and the fans can propagate the energy downstream so to speak. This is not the same as the CP river!


Given that Reynold number =20 what do you think the flow is laminar? How about Re =2000 will the flow is still laminar?

#796 BuckarooBanzai

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Posted 2011-10-21 22:10:27

Sir... Water cannot flow horizontally if no energy is supplied and it has zero momentum. I think you are confusing with your own premise. First you said the water can move horizontally. Then you said the water cannot be made to move horizontally by any mean. Which one is which?


Perhaps you would like to explain a siphon? Water moving uphill? NoWayMan! If their is pressure on one side of a horizontal channel and a lack of pressure on the other side of the channel the water will flow. The energy comes from the differential in pressure. MyPenRai!

#797 BuckarooBanzai

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Posted 2011-10-21 22:16:28

Given that Reynold number =20 what do you think the flow is laminar? How about Re =2000 will the flow is still laminar?


In fluid mechanics, the Reynolds number Re is a dimensionless number that gives a measure of the ratio of inertial forces to viscous forces and consequently quantifies the relative importance of these two types of forces for given flow conditions.

Just what are you applying these Re numbers to?

#798 BuckarooBanzai

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Posted 2011-10-21 22:18:24

@ BuckarooBanzai

Mate, if you engage these people you will go mad I promise. They are making it up as they go along and laughing at the reaction.

Mods, can this be transported to the Farang Pub Forum yet?

More of the threads Four Musketeers!


Sometimes the mentally challenged become a challenge!

Edit - took out media.

Edited by BuckarooBanzai, 2011-10-21 22:19:25.


#799 GentlemanJim

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Posted 2011-10-21 22:43:49


@ BuckarooBanzai

Mate, if you engage these people you will go mad I promise. They are making it up as they go along and laughing at the reaction.

Mods, can this be transported to the Farang Pub Forum yet?

More of the threads Four Musketeers!


Sometimes the mentally challenged become a challenge!

Edit - took out media.


I totally admire your resilience. I was beginning to wonder if they were the Borg! :)

#800 ResX

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Posted 2011-10-21 22:44:01


Given that Reynold number =20 what do you think the flow is laminar? How about Re =2000 will the flow is still laminar?


In fluid mechanics, the Reynolds number Re is a dimensionless number that gives a measure of the ratio of inertial forces to viscous forces and consequently quantifies the relative importance of these two types of forces for given flow conditions.

Just what are you applying these Re numbers to?


I think you have to goggle more. Anyway, you get it right but I know you just goggled it out. Do you thing Reynold is crazy? What does his dimensionless number has anything to do with water? I do beleive he is crazy. And the persons who keep on using his number as equally crazy.:D

Without knowing Reynold number you can't tell whether any flow is laminar or turbulence or in transition zone.





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