output array elements in rows

Dear list,

I'm looking for a function to output the elements of my array column  in
rows ? Let's say I have following table:

id = integer
nam= array char varying

id    nam
1     {"nam1","nam2","nam3"}
2    {"n1","n2"}

I think there should be available a function to expand the elements of an
array of caractères into a set of rows ?


id    nam
1     nam1
1     nam2
1     nam3
2     n1
2     n2


THANK YOU VERY MUCH FOR YOUR HELP