– Tractor trailers that transport liquid are cylinders, soda cans, water bottles etc. Why are most liquids transported in cylindrical vessels instead of square or rectangular?
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Because liquids don’t flow well on flat surfaces.
If your liquid is stored in a rectangular container and you drain it from the bottom you’re going to have some of that liquid remain on the bottom since it’s flat but if the whole thing is round and the drain is on a little bit of a curve the whole thing will drain.
It has to do with the ergonomics of the container in the case of handheld beverages. It’s a trade off of the minimum material needed(a sphere I think) and the most efficient way to transport it which is some sort of cuboid. There’s a few videos out there that explain it in much better detail.
If you fill up a square sided container with liquid the fluid pressure will try to make the side bend. In order to resist this you need to have very thick sides so they’ll be stiff enough to carry the bending and not deform outwards.
If you fill up a circular container the fluid pressures will apply forces that are carried almost entirely in tension, and can only deform the container by stretching the material. Materials are much stronger and stiffer in tension than a similarly sized object is in bending, so you can use much thinner walls.
Those corners on a rectangular storage container create easy stress points. Cylindrical containers evenly distribute pressure.
A sphere is the most efficient shape to enclose a volume. The least amount of metal is needed and pressure is equally distributed. However it’s not efficient in “stacking” – a cube has the least wasted space outside the container but with many weaknesses and high pressure points.
The cylinder is a compromise, with better than a sphere in optimization for space and the better than the cube for pressure and material use.
The engineering guy has an excellent you tube video on the creation of the aluminum soda can that discusses the cylinder as a compromise shape.
Spherical container is the best container for fluids (gas or liquid) as it deform the least in case of pressure changes.
Manufacturing spherical containers is a pain. Is done when conditions are extreme, like very high pressure or very high risk environment.
A cylinder is a very nice trade off, you need to reinforce the two ends, but the round part is very sturdy just because is round.
This advantage allows to benefit of one or more of the following: save material, save manufacturing cost, save design costs, extra strength of the container, reliability, resilience.
Downsides: squared stuff can be packed together with no air gaps, saving space. Cylinders can’t be packed together without having gaps and therefore wasting space.
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