Sukhotin's algorithm (introduced by Boris V. Sukhotin) is a statistical classification algorithm for classifying characters in a text as vowels or consonants. It may also be of use in some of substitution ciphers and has been considered in deciphering the Voynich manuscript, though one problem is to agree on the set of symbols the manuscript is written in.
References
Sukhotin's algorithm Wikipedia(Text) CC BY-SA