Closed-Open Air Column
In a closed-open pipe (like a tube with one end closed by water), the closed end is a pressure antinode (displacement node) and the open end is a pressure node (displacement antinode).
L = (n + ½) · λ/2 f = (n + ½) · v/(2L) (n = 0, 1, 2...)
Open-Open Air Column
In an open-open pipe (like a flute), both ends are pressure nodes (displacement antinodes). All harmonics are present in this case.
L = n · λ/2 f = n · v/(2L) (n = 1, 2, 3...)
