For those who came in late, vowel hiatus is a common term for the occurrence of consecutive vowel sounds each of which serves as the nucleus of a syllable. For example, in the word “chaotic” we see consecutive syllabic [eɪ̯ɑ̩]. In the word “reality” we see consecutive syllabic [ia̩]. In the word “aortic” we see consecutive syllabic [eɔ̩ɚ̯].
Many languages limit or forbid vowel hiatus. Strategies for this are called “vowel hiatus resolution.” Among them are …
inserting a consonant between two consecutive vowel sounds (created by compounding or affixation, for example)
turning one of the two onsecutive vowel sounds into a glide and so creating a single syllable diphthong
turning the two vowels into one vowel that shares the features of both
Vowel hiatus resolution is discussed with considerably more detail and rigor at this link: https://www.ling.upenn.edu/~gene/courses/530/readings/Casali2011.pdf
Be that as it may, I have yet to find a description of the kinds of rules that prevent the formation of words comprising only four or more consecutive vowels. From what little I’ve heard, such words have never been attested in any natural language.
I’m trying to describe a conlang that allows the occurrence of two consecutive syllabic vowels, but not more. In natural language, and in descriptions of them, what kinds of rules constrain the number of consecutive syllabic vowel sounds, what are these rules called, and how are they written or described?