The correct german spelling is Vömel using the german umlaut 'ö'. Since in some cases the umlaut is not available, the correct german transliteration is Voemel, using 'oe' instead of 'ö'. The sound is similar to the sound 'o' in 'word'. The german sound of 'V' is the same as of the english 'F'. The occasional spelling Vomel is incorrect. All of my publications use the spelling Vömel and should be referenced using that spelling.
Like many old german names this name may have refered to an old profession. The name Vömel is related to the plant 'Fimmel' or 'Hanf' in modern german, 'hemp' in Enlgish and may have been used for the people who produced hemp.
To type the umlaut on a typical computer keyboard type
<ALT> 148, using the numeric keypad
In Microsoft word use
<CTRL><SHIFT> :
then type the letter 'o'
or just copy and paste from this page.