Transient flow: waves
The free surface of the water is “deformed” by the wind (waves). In nature, there is a wide variety of waves (long or short wavelengths, breaking or smooth, etc.) Natural waves are irregular, for example a flat wave follows a high wave (amplitude). Aside from wind-induced waves, there are also surface waves caused by a disturbance, positive and negative surge waves and tsunami waves, which are caused by an increase in the water, such as during an earthquake. Waves carry energy, but no mass. When a wave reaches shallow water, such as near the beach, it is slowed down. The wave trough is slowed more than the wave crest. Therefore, the wave crest overtakes the trough and the waves break.
The study of the formation and effect of waves is an important field in maritime navigation, coastal protection and in the design of offshore systems (wind farms, drilling platforms). In coastal protection in particular, it is a matter of reducing the destructive power of waves and the washing away of sediment.
Δh amplitude, h average depth, c propagation velocity of the wave, λ wavelength