Here, boundary conditions are as if there is a valve upstream that’s been rapidly shut, so a low pressure wave builds up and propagates to the right decelerating the liquid to a standstill state and then reflects at the end of the line at an ambient pressure boundary and propagates back to the left accelerating the liquid in the opposite direction to refill the line, then when it hits that shut valve again, a high pressure wave generates and propagates to the right stopping the liquid from refilling the line and then reverses its direction when it reflects back, the cycle repeats with lower intensity waves until viscosity and pipe line destruction, if it’s not strong enough, dissipates this energy, liquid water with compressible liquid model was used in this simulation.