problem related to fluid mechanics

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vasuvasu Participant Join Date: Mar 2009 Posts: 1	problem related to fluid mechanics 03/29/2009 4:20 AM
	An artificial open channel width 1m, depth 1m, in which water is flowing with velocity 1m/s. A water wheel is mounted on open channel .The water wheel blade dimensions are equal to Channel width and channel depth. The number of blades on water wheel is designed in such away that one blade is always at middle position as if water flow is completely stopped. Calculate the HP generated by water wheel? If the kinetic energy of water is less than water wheel resistance, the water flow stops so how much force acts on Water wheel due to weight of water If " X "force acts on water wheel and the resistance of water wheel is less than X amount of force. Then how much amount of HP water wheel can generate.
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Anonymous Poster	#1 Re: problem related to fluid mechanics 03/29/2009 4:21 AM
	Read the book and do your own homework.
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sb Guru Join Date: Mar 2007 Posts: 2550 Good Answers: 103	#2 Re: problem related to fluid mechanics 03/29/2009 4:37 AM
	Hello Guest that is my comment () This was the homework given for sunday. The answer to be submitted on monday. Correct answer will carry 10 marks. Every thing is 1 so answer also 1 ? How on blade can completely stop the flow ? Is it continuous disk with seal and no individual blades ? Then how the KE will be transferred ? what is the blade angle ? The water at 1m/s is at what position ? definitely not along the walls. When the water is blocked, it will pile up and overflow (open channel ) and then no KE it is only the potential energy ... (best to copy from your neighbour ? ) __________________ Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
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Ed Weldon Guru Join Date: Oct 2008 Location: I'm outa here Posts: 1924 Good Answers: 196	#3 In reply to #2 Re: problem related to fluid mechanics 03/30/2009 1:05 AM
	sb is right. In other words the power output is zero. That is because the the flow velocity is a given, 1 m/s and assumed therefore to be unchangeable. Therefore the kinetic energy content of the water is unchanged. This can only be the case when no energy is extracted by the water wheel. In the real world there will be some friction losses as well as fluid losses as the wheel blade moves in and out of the water at approximately the same velocity as the water. Since no relevant conditions are given these real world effects must be considered to be negligible for the purpose of answering the question at hand. Again in the real world application of an undershot water wheel there are some additional physical constraints that need be stated for a practical calculation of performance to be presented. So this is really a trick question and a poorly stated one at that. If it is coming from someone who calls himself a "teacher" perhaps a bit of reflection is called for. Ed Weldon
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Physicist? Guru Join Date: Apr 2007 Posts: 3531 Good Answers: 59	#4 Re: problem related to fluid mechanics 03/30/2009 4:51 PM
	Agree with antimony and with Ed, badly framed question, but answer as written is zero. However, for full marks you probably need to answer the implied second question about the upper bound of the power that could be extracted. For the bound you can forget the mechanism and consider only the kinetic energy; for the marks you need to consider the implications as well (how do you get rid of the water you have stopped). From here on in, you have to do the work for yourself.
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sb Guru Join Date: Mar 2007 Posts: 2550 Good Answers: 103	#5 In reply to #4 Re: problem related to fluid mechanics 03/31/2009 12:12 AM
	how do you get rid of the water you have stopped Irrigation of a large field ? The size and flow looks to be OK ? __________________ Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
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Physicist? Guru Join Date: Apr 2007 Posts: 3531 Good Answers: 59	#6 In reply to #5 Re: problem related to fluid mechanics 03/31/2009 5:01 AM
	How does the water move to cover the full area? (I won't answer immediately on the basis that it's probably homework - but I may answer in a few weeks' time if someone reminds me)
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sb Guru Join Date: Mar 2007 Posts: 2550 Good Answers: 103	#7 In reply to #6 Re: problem related to fluid mechanics 03/31/2009 7:05 AM
	the full area ? of what ? channel ? __________________ Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
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Physicist? Guru Join Date: Apr 2007 Posts: 3531 Good Answers: 59	#8 In reply to #7 Re: problem related to fluid mechanics 03/31/2009 11:22 AM
	The width of large field multiplied by the initial depth
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Anonymous Poster (1); Ed Weldon (1); Physicist? (3); sb (3)

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