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I think it has something to do with pressure distribution.For the Same volume which of these will hold the water at less pressure cylinder or sphere.And which has larger surface area or volume between the cylinder or sphere

2007-10-04 17:48:25 · 5 answers · asked by Anonymous in Science & Mathematics Engineering

5 answers

One factor is, as noted, that curved surfaces handle pressure better than a flat one. Think of how the sides of a cardboard milk carton bow out to become curved.

Cylinders are much easier to manufacture than other round shapes, but they don't work too well as end-caps so for that, something closer to spherical is used.

But there is another factor: easy of use - including loading and unloading the cargo, and cleaning the tank. Sharp corners are hard to clean and liquid settles in flat spots.

But if you look at the tanker trucks on the road, you will see that there is a variety of styles. Not all are simple circular cylinders with spherical end-caps. Some are oval cylinders; some look like two frustums (pieces of cones) with their fat ends together; etc.

Most of these difference are due to the needs of the cargo being transported - trucks carrying toxic chemicals have to be cleaned more thoroughly; viscous goods (honey, molasses, etc.) don't flow as well so need sides that slope more steeply to the lowest point where they can be pumped out; etc.

But there are also economic issues: the more the tank can hold, the cheaper it is to transport each unit. But various states have size and weight limitations for trucks. Having a truck that can carry more while still staying within the limits brings in more income. If you can do it without spending too much more on the truck, changing the truck's shape may pay.

Here's a picture of a "double conical trailer". Note that while the ends are domed, they clearly are not spherical:
http://www.fortworthfab.com/id22.htm

And here is a tank with an elliptical cross-section (taller than it is wide):
http://www.fortworthfab.com/id26.htm

And here is a truck designed to ship lime slurry.
http://www.fortworthfab.com/id34.htm

And from John McPhee's lovely article in the New Yorker (http://www.newyorker.com/archive/2003/02/17/030217fa_fact4):

"The architecture of the tank says what is in it." If a tank has gasoline inside, it has a full-length permanent manway on top, and, seen from the rear, is a recumbent oval. If a truck is a water wagon, the tank—rear view—is rectangular. A perfect circle ambiguously suggests asphalt, milk, or other food. If the vessel is all aluminum and shaped in tiers like nesting cups, it is a food-grade pneumatic hopper full of flour, granulated sugar, and things like that. If stiffeners are exposed—a series of structural rings circling and reinforcing the tank—the vessel is uninsulated, generally operates in a warm climate, and often hauls flammables and combustibles. Ainsworth said, "That is what mine looks like without the designer dress" (the stainless mirror sheath). The double conical side view speaks of chemical hazmats.

2007-10-05 21:22:32 · answer #1 · answered by simplicitus 7 · 0 0

true, aerodynamics would most likely be a factor, but i think becauues of its ability to withstand the pressure of water. Spheres and cylinders aare one of the stronger shapes, thats why butane cans are cyldrical, but have an inverted half sphere on the bottom. As for your question. I believe the cylinder will hold the water at less pressure simply because it would be bigger and the metal will expand (even a fraction) much easier than a sphere. which has the larger volume?

assume a cylinder 4 meters tall with a diameter of 4 meters.
and a sphere is 4 meters in diameter. And assume they are both filled 90% of their capacity. (im orunding results to 2 decimal)

Volume of cyliner= pie x r2 x H =50.27m3 x .9 = 45.243

Volume of sphere =4/3¶r3= 33.51 x .9 = 34.41

there you go, a cylinder will hold more water

2007-10-04 18:14:59 · answer #2 · answered by Anonymous · 1 0

For the 2nd part of the answer.

Surface area is not directly related to volume.
For the same surface area a sphere will have a larger volume than the cylinder.

2007-10-04 18:44:19 · answer #3 · answered by Kirk B 1 · 0 0

Basically it is for stability. If the tank were rectangular with vertical walls, the fluid would have a "free surface effect" as the tanker went into a curve or turn. That is, the liquid would try to shift to one side which would change the center of gravity of the trailer. And depending on the specific gravity of the liquid could easily create upsetting moments. A round tank vastly reduces the free surface effect in that it doesn't have a vertical wall to rebound from. And the rebounding of the fluid would be at different speeds, angles & enertia. SN

2007-10-05 00:40:45 · answer #4 · answered by Steve N 1 · 0 0

Three possible reasons:

Aerodynamics to reduce drag from air friction.
Spheres can handle pressure better than flat plates (guess).
More volume can be contained in the sphere than the cylinder for the same amount of surface material used.

2007-10-04 18:00:24 · answer #5 · answered by Anonymous · 0 1

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