When a drop of water falls onto a calm lake, we see ripples forming and propagating from the point where the drop hits the water surface. Such small waves are in fact disturbances due to the falling drop.
So how about disturbances taking place in a gas, for example air? Will they lead to waves in the gas flow? The answer is certainly yes. Particularly, different types of waves occur when the gas flow is compressible. Due to the compressibility of gas, some of them are compression waves and others may be expansion waves. One good example is the compression wave (or shock wave) generated when popping a champagne cork.
In this lesson, we will introduce two distinct compressible waves. We will also briefly go through how they are formed, what their characteristics are and what impact these waves have on the flow properties.
Here are the accompanying handouts for this lesson.