Dominic Read,
Intuitive feel for how water acts is hard to learn in a classroom but comes naturally when you play in moving water. Having spent a large chunk of my life playing in white water, either in a raft or kayak I have a fairly good feel for water, but like all intuitions, it can suffer inaccuracies when under scientific scrutiny. I�m quite interested to see if my observations have scientific merit or are just mad ramblings. 1. The water on a river definitely is faster in the center below the surface. It seems to have distinct boundaries with each layer flowing a different speed. If you�re swimming you can feel the difference and often get sucked down by the lower pressure that exists in the faster water. (like a wing, where the air on top moves faster causing lift). 2. The water tends to be parallel with the bottom when you look lengthwise, but you will notice a distinct difference of the center being higher then the edges in a cross section. I don�t know the science causing this but have always attributed it to the faster center causing a vacuum that �sucks� the edges inward. During flood conditions, you can see a distinct hump as you look across the river. A Second point here is that water likes to be stable (laminar) as it flows. If something disturbs it�s flow turbulence is caused temporarily with the water eventually reorganizing itself. 3. Like your rolling marble ball, an equilibrium speed will be reached. A river�s natural flow has a main conduit of water flowing fastest in the center. This water pushes against the slower water along the bottom causing an outward flow which when it reaches the edge returns to the center along the surface (thus if you ever get caught in a river and can�t seem to swim to shore� dive to the bottom). This inward bound water then collides with the main water conduit and cycles back to the shore again. This results in higher friction then just linear flow, there is the angular flow plus the inward flow water striking the main conduit which causes backpressure on the system. 4. As far as mental models, I think Tesla�s �One-Way Valve� would help your basic understanding of resistance to flow. HYPERLINK "http://www.dogpawz.com/skylos/tesla/1329559.html"http://www.dogpawz.com/sky los/tesla/1329559.html Lawrence Balisky _____ From: ReadFamily [mailto:[EMAIL PROTECTED] Sent: Wednesday, September 22, 2004 2:45 PM To: [EMAIL PROTECTED] Subject: [microhydro] How does water flow I am trying to build mental model so that I can explore some possibilies about micro hydro (maybe nano hydro) in my head. I understand what happens to a marble on an inclined plane, how the component of gravity along the plane causes linear and angular acceleration, how there is a maximum velocity, limited by friction with the plane and air resistance, but I find that when I try to understand the same thing with an inclined trough with water in it that I dont have an intuitive feel for it. It suprises me that water doesnt run faster. Is there really that much friction between the water at the edges of a trough and the water running in the center? Where is the water running fastest, in the center of the trough probably, but at the surface, or below the surface. Would the water run at the same speed on an infinitely long incline as it would with an incline ending in a 'waterfall'. With no incline the water surface would be parallel to the bottom of the trough. As the trough is inclined, does the surface stay parallel to the bottom, or is there an angle? What would be the difference between a rough surface to the trough (rough like unfinished aluminum) and a teflon finish, or a mirror finish. Does anyone have any useful mental models to share to help me understand intuitively how water behaves in an open trough? Dominic Read Just getting my feet wet. ----- Original Message ----- From: "Fly Boy" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, September 22, 2004 1:52 PM Subject: RE: [microhydro] I have a stream flowing through my yard, what can I do with it? > Thanks everyone for your comments. To answer some of the questions raised: > > I desire to sell 100% of the power. > > Using both my property and the neighbors I will have 145m head and taking > the contours of the land into account, 1,900m of pipe. > > I would like to keep the budget low with a DIY approach where possible. I > have a 200 series highhoe which should help keep the cost of laying pipe > down to a minimum. > > A few questions that I still have are: > > 1. How do I ball park the cost of the project. (What are the different > components that I will need? Turbine, generator, etc.) > > 2. What type of pipe is needed? Will plastic pipe work? (according to > Joseph Hartvigsen's data I'm guessing I will need about 50cm diameter pipe.) > > 3. Does anyone know an approximate amount BCHydro would pay for my > electricity? Without that figure I'm just shooting in the dark. Their > office told me it was decided on a contract basis so could not venture a > guess. > > Thanks, > Lawrence Balisky > > -----Original Message----- > From: Cesar Soriano [mailto:[EMAIL PROTECTED] > Sent: Tuesday, September 21, 2004 12:45 AM > To: [EMAIL PROTECTED] > Subject: Re: [microhydro] I have a stream flowing through my yard, what can > I do with it? > > > Lawrence, > > you have a very nice site specially if this is an abrupt fall sinse you did > not mention the slope of the stream. > > with some simple estimates, at 95 meters head and at the average flow, you > can put up a 200 kWs micro hydro power plant and at the lowest of 0.21 cms, > you have a firm plant capacity of 97 kWs. These are just estimates using an > efficiency of 50% to consider losses. You can even generate more if you > involve the property of your good neighbor. > > The grid you are referring to must be what is called a singel wire earth > return (swer) electric line. you can ask the utility maintaining the line > the voltage rating of that system. > > first thing, do you plan to sell the generated energy? or generate only for > your own consumption? > > regards. > > _________________________________________________________________ > Designer Mail isn't just fun to send, it's fun to receive. Use special > stationery, fonts and colors. > HYPERLINK "http://join.msn.com/?pgmarket=en-ca&page=byoa/prem&xAPID=1994&DI=1034&SU=ht t"http://join.msn.com/?pgmarket=en-ca&page=byoa/prem&xAPID=1994&DI=1034&SU=h tt p://hotmail.com/enca&HL=Market_MSNIS_Taglines > Start enjoying all the benefits of MSN� Premium right now and get the > first two months FREE*. > > > > > > Does your company feature in the microhydro business directory at HYPERLINK "http://microhydropower.net/directory"http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! > > NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. > > More information on micro hydropower at HYPERLINK "http://microhydropower.net"http://microhydropower.net > > To unsubscribe: send empty message to [EMAIL PROTECTED] > Yahoo! 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