If cacophony is a discordant and meaningless mixture of sounds, is there a word like this, only is refers to odors? If I said "a cacophony of smells", would that make sense?
A "cacophony of smells" can work, as can "cacosmia" depending on what you are looking to do/write.
Ok - first to the overall question being asked - the whole point of written communication, whether it be literature or an essay or whatever, is to communicate. What it is that you want to have communicated is another question, but the overall thing here is to be understood.
With that in mind, I find the phrase "cacophony of smells" to be very understandable, so yes, if you were to use that phrase, I for one would understand what you were trying to say. And with the use of some descriptive language, eg.
As I entered the backstage area of the circus, my nose was assaulted with a cacophony of smells: animal dung, stale beer, cheap cigarette smoke, unwashed bodies, cloying perfume, and the unmistakable miasma of doom and depression.
That said, I was able to find a word that may fit the bill: cacosmia. Keep in mind on this that I found definitions for it that both refer to an actual "cacophony of smells" and to a medical condition where someone senses a cacophony of smells where none exists, so I'll let the reader/student decide if this is a word you'd like to use or to examine more fully.
Now let's take the example paragraph above, substitute in this new word, and see what happens:
As I entered the backstage area of the circus, my nose was assaulted with a cacosmia: animal dung, stale beer, cheap cigarette smoke, unwashed bodies, cloying perfume, and the unmistakable miasma of doom and depression.
What changed between the first and second examples? Well, we know in example one that we are dealing with someone with a good grasp of the English language - the use of "cacophony" shows that. But in the example two, the person talking is astoundingly good with the English language - or wants to be seen that way. The tone of the piece changes - perhaps not perceptively on its own, but with some other evidence, can really herald a character's intelligence, state of mind, status, and so much more.
I think the question then becomes, in the end, how do you want the reader to perceive what they are reading?