It is a question of the prefix “un” which can be both reversive or intensitive, and yes, in the sense on untangle they have the same meaning:
Ravel probably comes from the Dutch word ravelen, meaning to 'fray out, tangle', and was first used in late Middle English with the sense of 'entangle, confuse'. Interestingly, the more commonly used verb definitions of ravel in Modern English actually have the opposite meaning: 'untangle', for example 'ravel something out'; and 'unravel; fray, as in a 'ravelled collar' (the latter not in American usage). It's only the third verb definition, 'confuse or complicate', and the noun meaning, 'a tangle, cluster, knot', that are closer to the original meaning
Unravel:
c. 1600 (transitive), from un- (2) + ravel (v.). Intransitive from 1640s. "The prefix is either reversive or intensive, according as ravel is taken to mean 'tangle' or 'untangle'" [Century Dictionary]. (Etymonline)
Unravel, is a verb which means to either 'undo', for example twisted threads, or to 'investigate and solve or explain' something which is complex or puzzling. A couple of examples of using unravel are:
(fandom-grammar)