Huh? I thought the "u" part is the one with two little dots on top of "u"??? No wonder weird characters came out when I tried pinyin... This is so frustrating...
The u with two dots in PinYin is called U-umlaut in German, and pronounced the same way. Example is as in 鱼 (Yü) vs. Über. When using pinyin input in computer, if you type u, the computer will suggest either ü or u based on the context and consonant in front of it. The safest way in most pinyin based input method is to use V instead of U after typing the consonant. The reason for that trick is because Pinyin does not use letter V and it looks similar to U and Ü. In other words computer input method substitute letter Ü with V.
I don't know if you are confused by wikipedia's entry of Pinyin or some other way. Anyway the wiki page put ü or u in the same place to pronounce the sound as in 鱼. This is wrong. (A reason I hate wikipedia which allows falseness to spread unchecked) The two letters are never interchangeable in the standard, however it becomes an accepted corruption in the computer era due to the fact that most Chinese computer keyboard is essentially US English keyboard which lacks letter Ü and nobody bothers to find the V trick.
