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Message: 16 Date: Thu, 1 Jul 2004 19:55:33 -0700 (PDT) From: Alejandro Tejada <[EMAIL PROTECTED]> Subject: Re: Flow in channels To: [EMAIL PROTECTED] Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=us-ascii
on Thu, 1 Jul 2004 Jim Hurley wrote:
I have just posted an application which allows one to determine the flow rate in water channels.
I could easily imagine an ultra-complex java applet to accomplish this! ;-)
I realize this is of almost no interest to Run Revers,
There is an interesting stack showing the interaction between the eyes and diverse medicaments. I do not remember if Michael J. Lew posted a link in this list:
Good ideas in teaching pharmacology <http://www.iuphar.org/autonomical/autonomical.zip>
Al,
I wasn't able to run the the OS 9 application (get a message: can't find application), but I can guess how bezier curves might work in this example.
but it is a good illustration of the use of Bezier curves in Run Rev, allowing one to predict the velocity and flow rates in channels of arbitrary shape.
I agree that this stack is an interesting and practical use of bezier curves. Nice work, Jim!
I noticed that in channels with flat floors the water velocity is slower than in channels with cilindrical shaped floors. Is this expected?
Very perceptive of you. It is an interesting physics problem.
Flow in channels, canals, creeks, rivers, etc. are all examples of free fall under gravity. The water continues to accelerate away from the source until the gravitational force is just balanced by the frictional force. At this point the water has reached its terminal velocity.
The terminal velocity of a rock is greater than the terminal velocity of a feather because the frictional force on the rock is a smaller fraction of the gravitation force than it is for a feather.
The same thing applies to falling water, whether rain drops or stream flow. With great volumes of water the terminal velocity is large and for small volumes it is small.
And in the case you mention of the flat-bottom channel verses the round bottom you can see that the wetted perimeter is greater fraction of the cross-sectional area. (The velocity is proportional to the two thirds power of the hydraulic radius which is the ratio of area to the the perimeter.)
How is this stack used by hydraulic Engieners?
Say they wanted to build a channel to carry 40 cfs of water. How deep and wide should the channel be given the available slope of the land? Manning's formula allows them to make this determination. I'm not sure whether they have the tools to make this determination for complicated shapes. It is very difficult calculation to perform analytically. Even for a circular shape it is messy. It is relatively simple in my stack where the integrals for the area and perimeter are calculated numerically from the points that define the shape of the water's cross-section. I didn't do this for the engineers. I did it so that we (our group is "Save Our Historic Canals") could challenge the Irrigation District's EIR (Environmental Impact Report). They want to abandon the canal and put the water in a pipe. Good engineering but not good for the hundreds of people who walk the canal trail.
I find, more and more, how useful Run Rev is to me personally, simply as a tool to find answers to problems that interest me.
Jim
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