*2.2. Wave Generation*

A hollow cylinder with a diameter of 10 cm and height of 40 cm was used in the experiment to artificially create waves in the flume. The cylinder was placed horizontally on one end of the flume and then it was moved up and down the water surface to create the first wave as shown in Figure 3a; when the first wave propagated to the other end of the flume, a reflected wave was formed and then propagated in the opposite direction. The cylinder was moved up and down the water surface to produce the second wave as shown in Figure 3b; when two waves collided in the middle of the flume, a superposition occurred (Figure 3c); then, the two waves continued to advance in their respective directions (Figure 3d), and a reflected wave was formed simultaneously at each side wall of the flume.

**Figure 2.** Schematic diagram of wave flume.

*2.2. Wave Generation* 

*2.2. Wave Generation* 

When the first wave was located at the hollow cylinder, the cylinder was moved up and down at the frequency of the wave to increase the amplitude of the wave or to supplement the energy lost during the propagation (Figure 3e). The second wave collided with the first wave in the middle of the flume after being reflected by the side wall of the flume and then they separated (Figure 3f); we supplemented the energy lost during the propagation in the same way. Continuous waves with different frequencies were formed in the flume in this way. directions (Figure 3d), and a reflected wave was formed simultaneously at each side wall of the flume. When the first wave was located at the hollow cylinder, the cylinder was moved up and down at the frequency of the wave to increase the amplitude of the wave or to supplement the energy lost during the propagation (Figure 3e). The second wave collided with the first wave in the middle of the flume after being reflected by the side wall of the flume and then they separated (Figure 3f); we supplemented the energy lost during the propagation in the same way. Continuous waves with different frequencies were formed in the flume in this way. directions (Figure 3d), and a reflected wave was formed simultaneously at each side wall of the flume. When the first wave was located at the hollow cylinder, the cylinder was moved up and down at the frequency of the wave to increase the amplitude of the wave or to supplement the energy lost during the propagation (Figure 3e). The second wave collided with the first wave in the middle of the flume after being reflected by the side wall of the flume and then they separated (Figure 3f); we supplemented the energy lost during the propagation in the same way. Continuous waves with different frequencies were formed in the flume in this way.

a superposition occurred (Figure 3c); then, the two waves continued to advance in their respective

a superposition occurred (Figure 3c); then, the two waves continued to advance in their respective

*J. Mar. Sci. Eng.* **2019**, *7*, x FOR PEER REVIEW 4 of 10

A hollow cylinder with a diameter of 10 cm and height of 40 cm was used in the experiment to artificially create waves in the flume. The cylinder was placed horizontally on one end of the flume and then it was moved up and down the water surface to create the first wave as shown in Figure 3a; when the first wave propagated to the other end of the flume, a reflected wave was formed and then propagated in the opposite direction. The cylinder was moved up and down the water surface to

A hollow cylinder with a diameter of 10 cm and height of 40 cm was used in the experiment to artificially create waves in the flume. The cylinder was placed horizontally on one end of the flume and then it was moved up and down the water surface to create the first wave as shown in Figure 3a; when the first wave propagated to the other end of the flume, a reflected wave was formed and then propagated in the opposite direction. The cylinder was moved up and down the water surface to

*J. Mar. Sci. Eng.* **2019**, *7*, x FOR PEER REVIEW 4 of 10

**Figure 3.** Schematic diagram showing the wave generation. **Figure 3.** Schematic diagram showing the wave generation. **Figure 3.** Schematic diagram showing the wave generation.

In the flume experiment, the length of the flume was short (120 cm), and the wave propagated from one side wall of the flume to the other within a short time, so that two waves were superposed together in the flume to form the standing wave. Only the waveforms in Figure 3e, f could be seen in the flume during the experiment, as shown in Figure 4. In the flume experiment, the length of the flume was short (120 cm), and the wave propagated from one side wall of the flume to the other within a short time, so that two waves were superposed together in the flume to form the standing wave. Only the waveforms in Figure 3e,f could be seen in the flume during the experiment, as shown in Figure 4. In the flume experiment, the length of the flume was short (120 cm), and the wave propagated from one side wall of the flume to the other within a short time, so that two waves were superposed together in the flume to form the standing wave. Only the waveforms in Figure 3e, f could be seen in

the flume during the experiment, as shown in Figure 4.

(**a**) wave crest (**b**) wave trough (**a**) wave crest (**b**) wave trough

**Figure 4.** Experimental photographs showing the wave generation. **Figure 4. Figure 4.**  Experimental photographs showing the wave generation. Experimental photographs showing the wave generation.
