Shallow Water Wave Equation Simulation: Reverse Shoaling?

In summary, the conversation discusses the creation of a simulation of the shallow water wave equation in MATLAB. The equations being used are for the velocity and height, and they are iteratively updated from neighboring values. The simulation is capable of modeling traveling waves, reflection, superposition, diffraction, and refraction. However, when the depth decreases over distance, the simulation predicts a decrease in wave height instead of an increase. It is unclear if this is an issue with the model or if it is predicted by the shallow water equations.
  • #1
person123
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TL;DR Summary
My simulation of water waves using the shallow water equations predicts decreasing wave height as depth decreases.
I'm creating a simulation of the shallow water wave equation in MATLAB. I'm using the equations:

$$\frac{\partial v}{\partial t}=-g\frac{\partial \eta}{\partial x}$$
$$\frac{\partial h}{\partial t}=-h\frac{\partial v}{\partial x}$$

Iteratively updating the velocity from neighboring heights and then the height from neighboring velocities.

It's able to modeling traveling waves traveling at ##c=\sqrt{gh}## as well as reflection, superposition of waves, and (in 2D) diffraction and refraction. However, when the depth decreases over the distances, it predicts the wave height decreases instead of increases. In the attached video, for example, the water depth decreases linearly from a maximum to ##0## with increasing ##x##.

Is this decrease in wave height predicted with the shallow water equations, or do you think this is an issue with my model? Thanks!

 
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  • #2
It may be the model? I've done a 1D tsunami run-up simulation as exercise a lifetime ago, but I used a quasi-linear formulation:
1650023269635.png

1650023331485.png

This definitely did increase the waveheight with decreasing depth.
 

FAQ: Shallow Water Wave Equation Simulation: Reverse Shoaling?

What is the shallow water wave equation?

The shallow water wave equation is a mathematical model used to describe the behavior of waves in a body of water with a depth that is significantly smaller than the wavelength of the waves. It takes into account factors such as gravity, water density, and the shape of the ocean floor.

What is reverse shoaling?

Reverse shoaling is the phenomenon in which a wave that is traveling in shallow water suddenly increases in height as it reaches deeper water. This is due to the decrease in wave speed and increase in wave amplitude as the water depth increases.

How is the shallow water wave equation used to simulate reverse shoaling?

The shallow water wave equation can be solved using numerical methods to simulate the behavior of waves in different water depths. By inputting the appropriate initial conditions, such as the wave height and water depth, the simulation can show how the wave will change as it travels from shallow to deeper water.

What are the applications of reverse shoaling simulation?

Reverse shoaling simulation can be useful for predicting the behavior of waves in different water depths, such as in coastal regions or harbors. It can also be used for studying the impact of waves on structures and for designing coastal protection systems.

What are the limitations of the shallow water wave equation simulation for reverse shoaling?

The shallow water wave equation is a simplified model and does not take into account factors such as wave breaking and wave interactions. It also assumes a uniform water depth, which may not be the case in real-world scenarios. Therefore, the results of the simulation should be interpreted with caution and may need to be validated with other methods.

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