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It's funny, because in my much younger days I dropped out of college and worked as a mechanic for 3 years. In the automotive world and internal combustion World, manifold has a much different meaning, though related.

Basically, a manifold means something that takes the flow of gases from a one-to-many or a many-to-one.

An intake manifold takes one single entry point for air feeding the engine and splits up into a separate input for each cylinder.

An exhaust manifold takes the hot exhaust from each cylinder separately and combines them into one big pipe.




A similar notion exists in the fire service, where a manifold is an appliance for combining or splitting water supply lines. A typical example of a fire service manifold would be an appliance with 3 2.5" threaded ports and a single 5" Storz port, which can be used to either merge multiple 2.5" or 3" supply lines into one 5" supply line, or to divide the flow from a 5" line up into multiple smaller lines.

Example: http://fireflowtechnology.com/wp-content/uploads/2015/04/100...


And on a smaller scale, ordinary water plumbing :-).


And I always think of the mathematical definition. It's nice to see the mechanical terminology explained. Thanks!


Sorry, I was not aware of that! It was not my intention to mislead you. Hope you enjoyed the article nonetheless :-)


Plenum is also used to describe automotive intakes, and has a physics meaning as well.


> An exhaust manifold takes the hot exhaust from each cylinder separately and combines them into one big pipe.

Does that have anything to do with “many-fold?”


Yes, the original Old English was Manigfeald which means exactly that.


That's what manifold means to me as well.

Though, there are exceptions to the "one" part, like intake manifolds with two inlets (dual plane is common), exhaust manifolds with two outlets (common on inline 6 engines), and also some really odd setups: https://speedmaster79.com/media/catalog/product/cache/1/thum...


That picture looks like an intake for a V8 and each trumpet is still for an individual cylinder; it's just that the intake ports on the heads are paired up for manufacturing and thermal efficiency.


My point was that manifolds aren't all many to one. This one is clearly many to many.


> Basically, a manifold means something that takes the flow of gases from a one-to-many or a many-to-one.

A perfectly sensible meaning given the construction of the word. There is something about mathematics and linguistics (and to some extent CS) that encourages the creation of confusing, meaningless names like "accusative (case)", "(algebraic) ideal" and "(geometric) manifold".


> A perfectly sensible meaning given the construction of the word. There is something about mathematics and linguistics (and to some extent CS) that encourages the creation of confusing, meaningless names like "accusative (case)", "(algebraic) ideal" and "(geometric) manifold".

Confusing is hard to argue, but meaningless is, I think, hard to defend. These all have meanings; I could speak to the latter two, and I'm sure a linguist could speak to the former. They may not be obvious meanings, but that's not the same as saying they're meaningless. (I regard much business jargon, for example, as literally meaningless, defined only in terms of other words that also seem meaningless to me; but I'm sure an MBA would take issue with that characterisation.) I don't know who coined 'manifold', but 'ideal', for example, was literally Kummer's word coined to describe things that behaved like, but weren't quite, numbers in the ordinary sense (https://en.wikipedia.org/wiki/Ideal_number )—much like the "ideal points" of hyperbolic geometry (https://en.wikipedia.org/wiki/Ideal_point).

(EDIT: Fortunately no_identd knows more about the history of 'manifold' than I do (https://news.ycombinator.com/item?id=19659571).)


I don't think "encouragement" is quite right, ambiguities are somewhat the default - it's the opposite of encourage, an absence of something, there must be a competitive force present to reduce their likelihood.

I think there are less ambiguities in common language because they share so much context and compete; where as there is enough separation between certain disciplines for the semantics of esoteric words to evolve and coexist independently without issue until viewed externally where it appears ambiguous - this is even true for mathematical notations.



Isn't this like a multiplexer/demultiplexer in electronics/signal processing?


A multiplexer/demux takes one of many inputs and routes them to a single output, or vice versa. A manifold has no valving, so it's a mixer/adder instead.


PWM-switched mux/demux with signal input then :).


still not quite. more like a node where you join parallel circuits back together; the total volume of stuff moving, current, is the addition of everything coming in, rather than blocking and switching things.


You could at least say that the ground plane on a circuit board is an exhaust manifold


I actually clicked the link expecting exactly that explanation.


Sorry! It just goes to show that I am living in a filter bubble of mathematics. My intention was not to deceive you :-)


No need to apologize. Words have different meanings.


Not at all - I got more than I bargained for and learned something new!


This is also the general usage for chemists... As a chemistry and math major during my college days it was confusing to say the least.


I took apart a furnace once to replace an igniter.

I was thinking I was going to find a series of pipes or tubes fitted together.

Instead I found just two pieces of pretty thick sheet metal, close to plate thickness. They just went through a metal bender to form the pipes, and bolted together with a gasket in between.

Maybe that's how it got started. A plane, wrapped around something.




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