Why do ships have cicular windows,why not square ones?
In: Physics
Squares have 4 points of pressure, circles have more distributed pressure.
So circular windows are stronger
And for more amazing facts… manholes are round, to prevent cover from falling in and killing man…
It’s like standing on a bowl vs standing on a box. If you stand on a cardboard box, there are 4 corners and 4 sides holding you up. If you lean to one side, all of your weight is on that side. If you lean to a corner, theres a lot of pressure pulling the corner apart. If one side buckles, or one corner fails, the box tips over and you fall.
Now imagine standing on a bowl. The weight is evenly distributed around the entire thing. You can put all your weight on one side or the other, but it doesn’t really break that easily.
On a ship, there’s a chance that you face a large wave and it slaps against the window. In a plane, there is a lot of pressure in the cabin pushing outwards. These repeatedly changing pressures can lead to the metal frame around the corners of a window becoming weaker over time, like when you bend a paperclip back and forward until it snaps.
If you push on any shape but a circle, pressure is created. Pressure is bad and leads to failure. Circles distribute that pressure fairly evenly so less stress.
The hulls of ships are constantly flexing with the changing pressures from the ocean. This flexing exerts pressure on the windows as well.
A round shape withstands this pressure much better than a square shape would. An arch is one of the strongest shapes in architecture. A circle is pretty much just an all-sided arch.
Other people have already given great answers but if you want to do a bit more reading on this subject search up the DeHavilland Comet crashes, which were caused by fatigue cracks resulting from square windows.
Interesting anecdotes, I actually studied Aircraft Engineering at the University that originally started as DeHavilland’s technical college where they trained new engineers. So they were the ones responsible for the design that caused the crashes and were the first to identify the causes. Surfice to say, this was a big topic that was covered in my degree…
It’s about the shape of the hole in the ship. A round hole has no corners, corners can crack and cracks in ships are trouble.
When we are talking about strength, the most obvious analogy is water. Imagine a stream of water in a river. If you put something square-shaped in there, you would see vortices around, especially a lot of them near each corner. If you put something circular-shaped in the same stream, you also would see vortices but they would be smaller.
If we talk about the force-carrying structure, we could imagine internal forces as a stream in the river (structural part). And holes in part would create similar “vortices”, so-called stress (for simplicity, let’s say stress is internal force) concentrations. Those concentrations are locally increasing stresses. So, by that analogy, a circular hole would create smaller “vortices” than a square, therefore a circular hole would increase internal forces less than a square hole.
What might really blow your mind is that sometimes solid structures can be stronger with holes placed in then.
In stress analysis a popular term is “stress concentration”. If you apply load to a square and a circular shape, calculate stress you’ll see the sharp corners in a square have the highest stresses. We try to avoid sharp changes in corners as much as possible due to this and a circular object is the best possible answer with no sharp corners.
A ductile material like steel may deform a bit due to stress concentration but a brittle material like glass will simply just break if the stress is more than the material limit. Even ductile materials will fail over time due to fatigue if the load is cyclic , so where possible sharp corners are avoided.
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