In most words, the arrangement of the five major vowels A, E, I, O, and U, irrespective of the consonants, does not follow any particular pattern. In some words, however, vowels do exhibit specific patterns.
"Vowel Patterns in the OED,"
Word Ways: Vol. 37
, Article 4.
Available at: http://digitalcommons.butler.edu/wordways/vol37/iss2/4