Fig. 3

One-dimensional acoustic wave setup: The figure at top depicts the initial position of the acoustic wave and the wall. Here v denotes the velocity of the wall, which is set to \(v=0.01\). The domain to the right of the wall is penalized. The amplitude of the pulse is \(\epsilon = 10^{-3}\). Bulk of the fluid moves along with the wall at velocity v. The figure at the bottom shows the final position of the wall and the pulse after \(t=0.5\) seconds. The pulse after reflection from the wall, has reached the position \(x = 0.25\) and is seen to be travelling in the opposite direction