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Posted on December 18, 2008 @ 09:18:00 AM by Paul Meagher
This is the last installment in a 4 part blog series:
Today I want to do a simple water load calculation whose purpose is to increase our confidence that the Surface Load Package developed so far is capable of generating correct answers to surface load questions
Assume the water load we want to calculate is contained within a square tank that is 10 feet long by 10 feet wide and filled to a height of 1 foot.
According to the USGS Water website, a cubic foot of water weights 62 lbs per cubic foot. If we multiply 62 lbs by the number of cubic feet of water we have, 10 x 10 x 1 = 100 ft3, then we get a total water load of 6200 lbs in our water tank.
This water_load.php script can be used to compute the same answer:
<?php
include "../SurfaceLoad.php";
// 10 x 10 surface area
$load_area = "[0,0][0,10][10,10][10,0]";
// 1 foot of water
$load_height = 1;
// Weight of water in lbs per cubic foot volume
$load_unit_weight = 62;
$load = new SurfaceLoad($load_area, $load_height, $load_unit_weight);
$load->toHTML();
?>
When you point your browser at the water_load.php script you see this:
Volume: 100 ft3
Load: 6,200 lbs
So the software generated the correct answer for a simple case whose answer we can calculate in our heads. Hopefully it works for more complex polygons :-).
One calculation that I would like to do would be one that computes the amount of energy contained in an elevated tank of water. It might begin with the surface load calculation and then combine that information with other data about the setup (i.e., height of the tank above the ground) to compute the amount of potential energy in the setup. The reasons for wanting to do this calculation have to do with a pet idea about how the energy from the tides of the Bay of Fundy might be harvested. The idea is essentially to use the high tide to fill up a massive water container that releases the water at low tide to crank hydro-electric turbines. You should also be able to harvest energy from the inflow of water into this water container. I originally ran accross this idea on the Half Bakery website and have been casually musing about it ever since.
The current paradigm for harvesting Fundy tidal energy involves installing underwater windmill-like turbines. This paradigm is apparently encountering some harsh realities where recent monitoring of the Fundy bottom suggests that massive mud-imbued chunks of ice can potentially ride along the bottom and smash into the turbines. Perhaps we should look at a different paradigm for harvesting power from the massive Fundy tides? Above-ground hydroelectric? How massive would this water container have to be? How much power could be generated?
Another avenue that I would like to explore at some point would be adapting the concept of "load" to other domains: solar loads, wind loads, ecological loads, etc...
I don't think I will have the time to seriously explore these ideas so I'll end this "Calculating Loads" blog series for now.
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