That code doesn't make a lot of sense - it looks like you skimmed the assignment and leapt into code without thinking about it.
Look closely at this bit for example:
is the character that you what to check for a vowel, why are you also using it to see if you should end the loop? WHen exactly to you expect the index to exceed the value of a chartater? Especially when the value of 'u' is actually 117? You'd need a pretty large name there ...
Do yourself a favour, and throw all of that away, sit down and think about what you want to achieve before you start to code. This may help: How to Write Code to Solve a Problem, A Beginner's Guide