Prominence thread as a single magnetic field line of length L, with boundaries at anchored in a photosphere. A time-dependent plasma inflow, U along the thread is introduced, with a stagnation point at s = 0 and a correspondingly uniform density profile. The critical points where the Alfvén speed equals the inflow speed are marked in red. We inject an initial torsional velocity pulse along the thread which propagates in opposite directions towards the two boundaries and follow the evolution of the pulse.