MaxYakov Posted October 19, 2011 Share Posted October 19, 2011 (edited) Water behind a screw is highly turbulent. Then please try to Google (image) - cavitation test propeller What you are going to see? A huge propeller under test. The propeller is held static and rotating. No. There is no turbulence at all. We can see a few streamlines of vortexes. A picture is worth a thousand Googles (give or take). Edited October 19, 2011 by MaxYakov Link to comment Share on other sites More sharing options...
Crushdepth Posted October 19, 2011 Share Posted October 19, 2011 Water behind a screw is highly turbulent. Then please try to Google (image) - cavitation test propeller What you are going to see? A huge propeller under test. The propeller is held static and rotating. No. There is no turbulence at all. We can see a few streamlines of vortexes. Thanks, but you are completely wrong. Have you ever looked in the wake? I have, and it is as turbulent as hell. Link to comment Share on other sites More sharing options...
Crushdepth Posted October 19, 2011 Share Posted October 19, 2011 Water behind a screw is highly turbulent. Then please try to Google (image) - cavitation test propeller What you are going to see? A huge propeller under test. The propeller is held static and rotating. No. There is no turbulence at all. We can see a few streamlines of vortexes. A picture is worth a thousand Googles (give or take). Guys, get out of the lab and look behind the boat. Particularly a large one. Link to comment Share on other sites More sharing options...
Crushdepth Posted October 19, 2011 Share Posted October 19, 2011 (edited) If you must Google The Truth you can try ship wake turbulence, or perhaps this is representative (nice diagram): Ship wakes Edited October 19, 2011 by Crushdepth Link to comment Share on other sites More sharing options...
ResX Posted October 19, 2011 Share Posted October 19, 2011 (edited) Water behind a screw is highly turbulent. Then please try to Google (image) - cavitation test propeller What you are going to see? A huge propeller under test. The propeller is held static and rotating. No. There is no turbulence at all. We can see a few streamlines of vortexes. Thanks, but you are completely wrong. Have you ever looked in the wake? I have, and it is as turbulent as hell. That doesn't really matter. As long as you can see straight flow dominates then not all energy being supplied by the propeller ends up changing water phase. Therefore majority of supplied energy actually will accelerate the water. Edited October 19, 2011 by ResX Link to comment Share on other sites More sharing options...
serenitynow Posted October 19, 2011 Share Posted October 19, 2011 (edited) Water behind a screw is highly turbulent. Then please try to Google (image) - cavitation test propeller What you are going to see? A huge propeller under test. The propeller is held static and rotating. No. There is no turbulence at all. We can see a few streamlines of vortexes. A picture is worth a thousand Googles (give or take). Guys, get out of the lab and look behind the boat. Particularly a large one. I have, many many many times. Ship's wake is generally turbulent but it depends on lots of things as to how turbulent. Ship's loading, trim, whether or not screw has controllable pitch, how "clean" (undisturbed) the water is when it meets the propeller and wave height. Edited October 19, 2011 by serenitynow Link to comment Share on other sites More sharing options...
ResX Posted October 19, 2011 Share Posted October 19, 2011 Water behind a screw is highly turbulent. Then please try to Google (image) - cavitation test propeller What you are going to see? A huge propeller under test. The propeller is held static and rotating. No. There is no turbulence at all. We can see a few streamlines of vortexes. A picture is worth a thousand Googles (give or take). Guys, get out of the lab and look behind the boat. Particularly a large one. I know what you mean. As long as the boat you are referring to moves the there is no point. It is not going to prove the argument that all supplied energy has been used up to produce turbulence. Link to comment Share on other sites More sharing options...
BuckarooBanzai Posted October 19, 2011 Share Posted October 19, 2011 Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Link to comment Share on other sites More sharing options...
ResX Posted October 19, 2011 Share Posted October 19, 2011 Guys, get out of the lab and look behind the boat. Particularly a large one. I have, many many many times. Ship's wake is generally turbulent but it depends on lots of things as to how turbulent. Ship's loading, trim, whether or not screw has controllable pitch, how "clean" (undisturbed) the water is when it meets the propeller and wave height. This one has little thing to do with the propeller anyway. It will be created when the ship cuts the body of water. The propeller for a ship, especially for a big one will be located depth enough for better efficiency and to prevent cavitation. Link to comment Share on other sites More sharing options...
MaxYakov Posted October 19, 2011 Share Posted October 19, 2011 Water behind a screw is highly turbulent. Then please try to Google (image) - cavitation test propeller What you are going to see? A huge propeller under test. The propeller is held static and rotating. No. There is no turbulence at all. We can see a few streamlines of vortexes. Thanks, but you are completely wrong. Have you ever looked in the wake? I have, and it is as turbulent as hell. That doesn't really matter. As long as you can see straight flow dominates then not all energy being supplied by the propellers ends up changing its phase. Therefore majority of it is actually will accelerate the water. I'd go with ResX on this. If most of the force weren't directed aft, along the longitudinal axis, then propulsion would be VERY inefficient, rather than just somewhat inefficient. In any event, my gut tells me that it depends on the type of turbulence and the sum/direction of the force vectors of the turbulence. Another question w/r to ship wake turbulence is how much is due to the ship's hull, prop shaft supports and rudder? This also applies to aircraft propellers, particularly contra-rotating, coaxial props. Airfoils (aka airplane wings) are also an interesting example. Anyway, a consensus of two does not make it settled science (or conjecture), except in the case of AGW. Link to comment Share on other sites More sharing options...
serenitynow Posted October 19, 2011 Share Posted October 19, 2011 . Guys, get out of the lab and look behind the boat. Particularly a large one. This one has little thing to do with the propeller anyway. It will be created when the ship cuts the body of water. The propeller for a ship, especially for a big one will be located depth enough for better efficiency and to prevent cavitation. It depends. Depending on state of loading and trim part of the propeller may be out of the water at all times. anyhow, it is only a ship or a high HP tug with a Kort Nozzle that could even begin to move some water down the river. If they were tethered to a bridge, more likely than not they'd pull the bridge down. I'm talking screws of 4-7 meters diameter. Anything less is just turbulance. Link to comment Share on other sites More sharing options...
ResX Posted October 19, 2011 Share Posted October 19, 2011 Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Why it wants to do all of those things while refusing to push the body of water behind to move faster? Link to comment Share on other sites More sharing options...
TAWP Posted October 19, 2011 Share Posted October 19, 2011 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! Indeed, they'll end up drowning people in another nation if they keep this up... Link to comment Share on other sites More sharing options...
BuckarooBanzai Posted October 19, 2011 Share Posted October 19, 2011 Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Why it wants to do all of those things while refusing to push the body of water behind to move faster? Just think of it as Thai magic as reality is to much for you to get a handle on. Link to comment Share on other sites More sharing options...
MaxYakov Posted October 19, 2011 Share Posted October 19, 2011 Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Errrrr ... that would be a definite 'probably' and a definite 'maybe' (taking the liberty of breaking your question into two). Dissipates? Don't you mean 'transformed'? Link to comment Share on other sites More sharing options...
BuckarooBanzai Posted October 19, 2011 Share Posted October 19, 2011 Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Errrrr ... that would be a definite 'probably' and a definite 'maybe' (taking the liberty of breaking your question into two). Dissipates? Don't you mean 'transformed'? dis·si·pate (ds-pt) v. dis·si·pat·ed, dis·si·pat·ing, dis·si·pates v.tr. 1. To drive away; disperse. 2. To attenuate to or almost to the point of disappearing: The wind finally dissipated the smoke. See Synonyms at scatter. 3. a. To spend or expend intemperately or wastefully; squander. b. To use up, especially recklessly; exhaust: dissipated their energy. See Synonyms at waste. 4. To cause to lose (energy, such as heat) irreversibly. v.intr. 1. To vanish by dispersion: The dark clouds finally dissipated. 2. To indulge in the intemperate pursuit of pleasure. I would hazard to guess that most of you fall into 2. To indulge in the intemperate pursuit of pleasure. Cheers. Link to comment Share on other sites More sharing options...
MaxYakov Posted October 19, 2011 Share Posted October 19, 2011 (edited) Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Why it wants to do all of those things while refusing to push the body of water behind to move faster? Or maybe the model operates at the molecular level? Higher-velocity prop wash intermixes with lower-velocity river water producing both heat and kinetic energy transfer (increased velocity) to the slower river water? This description looks like a friction-based model to me. There's never a fluid dynamics/molecular physicist around when you really need one and I'm Googled-out right now! Edited October 19, 2011 by MaxYakov Link to comment Share on other sites More sharing options...
WarpSpeed Posted October 19, 2011 Share Posted October 19, 2011 (edited) If you must Google The Truth you can try ship wake turbulence, or perhaps this is representative (nice diagram): Ship wakes Actually this brings up another point that may be overlooked but could be used to improve efficiency. Instead of all boats pushing directly downstream off their stern it would be more beneficial for the boats on the left bank to direct their flow to the right or towards the rivers center and the boats on the right bank to direct their flow to the left also towards the center the goal of which is to meet in the middle and create an additional vacuum effect with their combined flow working in tandem and in the least restricted part of the river. The theory being that you move more water with a jet of water then just a dispersed nozzle and it will also carry more flow around it.. This would be most effective with a line of boats crossing the river and of course the boats in the center pushing directly from their stern and larger more powerful to smaller accordingly.. Edited October 19, 2011 by WarpSpeed Link to comment Share on other sites More sharing options...
BuckarooBanzai Posted October 19, 2011 Share Posted October 19, 2011 Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Why it wants to do all of those things while refusing to push the body of water behind to move faster? Or maybe the model operates at the molecular level? Higher-velocity prop wash intermixes with lower-velocity river water producing both heat and kinetic energy transfer (increased velocity) to the slower river water? This description looks like a friction-based model to me. There's never a fluid dynamics/molecular physicist around when you really need one and I'm Googled-out right now! A prop is designed to move a boat forward and not to move the water backwards. Politicians are designed to fool anyone that will listen to their crap. And lambs are designed to follow the ram. Cheers! Link to comment Share on other sites More sharing options...
ResX Posted October 19, 2011 Share Posted October 19, 2011 (edited) . Guys, get out of the lab and look behind the boat. Particularly a large one. This one has little thing to do with the propeller anyway. It will be created when the ship cuts the body of water. The propeller for a ship, especially for a big one will be located depth enough for better efficiency and to prevent cavitation. It depends. Depending on state of loading and trim part of the propeller may be out of the water at all times. anyhow, it is only a ship or a high HP tug with a Kort Nozzle that could even begin to move some water down the river. If they were tethered to a bridge, more likely than not they'd pull the bridge down. I'm talking screws of 4-7 meters diameter. Anything less is just turbulance. What you are trying to say the power from a propeller can pull a steel bridge down but cannot force says 5m3/s of water to move 0.2m/s faster? Guys think about a pump. Or thing about a hydro turbine. Or probably think about hydro pump-turbine. Kaplan turbine is quite similar to the ship propeller. It can be a pump too. Why you can believe pump-turbine can push 100m3/s of water to raise 300m (you have to believe with this one) higher but refuse to believe the same type of machine can push 4500m3/s or water to move faster by 0.2m/s (from 1m/s) traveling down at gradient says 1m/1km? :Let we see energy required for both cases. For case 1: We need to supply net capacity 295MW to the water exclusive losses. For case 2. We need 0.990MW. Yes. We need additional power of 0.990MW to increase the speed of 4500m3/s of water from 1.00 to 1.2m/s. I just made up this speed. Am I wrong here or what? Tell me if I'm wrong. I suppose it is not hard to believe this figure is accurate, right? Some of us here even suggested that the water can be slowed down a adding a boat to the river. Similar logic works the other way around. Taking away a boat from the river will make the water moves faster right? Edited October 19, 2011 by ResX Link to comment Share on other sites More sharing options...
WarpSpeed Posted October 19, 2011 Share Posted October 19, 2011 (edited) Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Why it wants to do all of those things while refusing to push the body of water behind to move faster? Or maybe the model operates at the molecular level? Higher-velocity prop wash intermixes with lower-velocity river water producing both heat and kinetic energy transfer (increased velocity) to the slower river water? This description looks like a friction-based model to me. There's never a fluid dynamics/molecular physicist around when you really need one and I'm Googled-out right now! A prop is designed to move a boat forward and not to move the water backwards. Politicians are designed to fool anyone that will listen to their crap. And lambs are designed to follow the ram. Cheers! Eh? So a jet engine is not designed to create rearward thrust? You're losing credibility here Buckaroo... Edited October 19, 2011 by WarpSpeed Link to comment Share on other sites More sharing options...
MaxYakov Posted October 19, 2011 Share Posted October 19, 2011 Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Errrrr ... that would be a definite 'probably' and a definite 'maybe' (taking the liberty of breaking your question into two). Dissipates? Don't you mean 'transformed'? dis·si·pate (ds-pt) v. dis·si·pat·ed, dis·si·pat·ing, dis·si·pates v.tr. 1. To drive away; disperse. 2. To attenuate to or almost to the point of disappearing: The wind finally dissipated the smoke. See Synonyms at scatter. 3. a. To spend or expend intemperately or wastefully; squander. b. To use up, especially recklessly; exhaust: dissipated their energy. See Synonyms at waste. 4. To cause to lose (energy, such as heat) irreversibly. v.intr. 1. To vanish by dispersion: The dark clouds finally dissipated. 2. To indulge in the intemperate pursuit of pleasure. I would hazard to guess that most of you fall into 2. To indulge in the intemperate pursuit of pleasure. Cheers. And the remainder into the immediately preceding 1, eventually and alas. Link to comment Share on other sites More sharing options...
BuckarooBanzai Posted October 19, 2011 Share Posted October 19, 2011 Eh? So a jet engine is not designed to create rearward thrust? You're losing credibility here Buckaroo... Thrust is not linear flow. If you want me to post wing turbulent flow I will but really it is a waste of time. The basis of all these arguments are about linear flow of thrust which is not the case. The thrust from props or jets are turbulent in nature. Link to comment Share on other sites More sharing options...
MaxYakov Posted October 19, 2011 Share Posted October 19, 2011 A prop is designed to move a boat forward and not to move the water backwards. Politicians are designed to fool anyone that will listen to their crap. And lambs are designed to follow the ram. Cheers! Eh? So a jet engine is not designed to create rearward thrust? You're losing credibility here Buckaroo... Don't worry about BB. He's probably just gone into rapid dissipation. He followed a propulsion absurdity with a political whatever-that-was. Link to comment Share on other sites More sharing options...
BuckarooBanzai Posted October 19, 2011 Share Posted October 19, 2011 A prop is designed to move a boat forward and not to move the water backwards. Politicians are designed to fool anyone that will listen to their crap. And lambs are designed to follow the ram. Cheers! Eh? So a jet engine is not designed to create rearward thrust? You're losing credibility here Buckaroo... Don't worry about BB. He's probably just gone into rapid dissipation. He followed a propulsion absurdity with a political whatever-that-was. I smile at the posts I read, and it is not because of dissipation. Link to comment Share on other sites More sharing options...
WarpSpeed Posted October 19, 2011 Share Posted October 19, 2011 (edited) Eh? So a jet engine is not designed to create rearward thrust? You're losing credibility here Buckaroo... Thrust is not linear flow. If you want me to post wing turbulent flow I will but really it is a waste of time. The basis of all these arguments are about linear flow of thrust which is not the case. The thrust from props or jets are turbulent in nature. I agree posting wing turbulence is just a waste of time, nobody is talking about wing turbulence just try and stand behind a jet engine at full throttle some time, with brakes on before take off and once you've stopped tumbling like a ping pong ball in Patong a few hundred yards later and get up to wipe down your bloody arms (and that's not just using a British euphemism) then tell us again how it doesn't have rearward thrust! But don't take my word for it take theirs! http://www.youtube.com/watch?v=KLyR6kuqfzU Jet engine blows away truck Edited October 19, 2011 by WarpSpeed Link to comment Share on other sites More sharing options...
ResX Posted October 19, 2011 Share Posted October 19, 2011 Why do you people hate the truth. The energy dissipates with heat, vortexes, movement of debris, and lapping of waves against the shore. Do you really love to argue so much that the truth doesn't matter any more? Why it wants to do all of those things while refusing to push the body of water behind to move faster? Or maybe the model operates at the molecular level? Higher-velocity prop wash intermixes with lower-velocity river water producing both heat and kinetic energy transfer (increased velocity) to the slower river water? This description looks like a friction-based model to me. There's never a fluid dynamics/molecular physicist around when you really need one and I'm Googled-out right now! A prop is designed to move a boat forward and not to move the water backwards. Politicians are designed to fool anyone that will listen to their crap. And lambs are designed to follow the ram. Cheers! But when they study the thrust that a propeller can deliver they hold the propeller standstill... Link to comment Share on other sites More sharing options...
MaxYakov Posted October 19, 2011 Share Posted October 19, 2011 Eh? So a jet engine is not designed to create rearward thrust? You're losing credibility here Buckaroo... Thrust is not linear flow. If you want me to post wing turbulent flow I will but really it is a waste of time. The basis of all these arguments are about linear flow of thrust which is not the case. The thrust from props or jets are turbulent in nature. See attachment. Abstract---The propeller wake from a ship may be important for an understanding of ship wakes in radar images. Interpretation of wake imagery promises to be useful in wide area maritime surveillance using satellites. A rotating propeller creates a wake, which can be visualized as a rotating horizontal column of water with both linear and angular momentum. This slowly broadens astern due to eddy diffusion as water surrounding the column becomes entrained within the wake. Purely linear momentum and purely angular momentum wakes are quite well understood both in theory and in practice. The purpose of this paper is to examine the combination of these wakes as occurs for a ship's propeller. The result is illustrated by applying it to the Queen of Alberni ferry. CombinedWakes.pdf Link to comment Share on other sites More sharing options...
BuckarooBanzai Posted October 19, 2011 Share Posted October 19, 2011 Eh? So a jet engine is not designed to create rearward thrust? You're losing credibility here Buckaroo... Thrust is not linear flow. If you want me to post wing turbulent flow I will but really it is a waste of time. The basis of all these arguments are about linear flow of thrust which is not the case. The thrust from props or jets are turbulent in nature. Nobody is talking about wing turbulence just try and stand behind a jet engine at full throttle some time, with brakes on before take off and once you've stopped tumbling like a ping pong ball in Patong a few hundred yards later and get up to wipe down your bloody arms (and that's not just using a British euphemism) then tell us again how it doesn't have rearward thrust! But don't take my word for it take theirs! http://www.youtube.com/watch?v=KLyR6kuqfzU Jet engine blows away truck Please. Stop the BS. Take a reading 200 meters away and you will witness the dissipation of the energy. If you think thrust will move the water all the way down to the mouth of the river you are beyond help. Link to comment Share on other sites More sharing options...
longway Posted October 19, 2011 Share Posted October 19, 2011 (edited) Any results from the boats available? Edited October 19, 2011 by longway Link to comment Share on other sites More sharing options...
.png.3b3332cc2256ad0edbc2fe9404feeef0.png)
.thumb.jpg.bc523c85a8d558dbc282dca7a2e602c9.jpg)
Recommended Posts