# Derosion Lattice Performance and Optimization in Solving an End Effect Assessed by CFD: A Case Study in Thailand’s Beach

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Theoretical Background

#### 2.1. Conservation Equations

#### 2.2. Turbulence Equations

_{t}is the eddy viscosity, and P

_{k}is the shear production of turbulence. ω is the specific dissipation rate, k is the turbulent kinetic energy, and F

_{1}is the blending function. α

_{3}, β

_{3}, and σ

_{ω3}are the specific coefficients for the SST k–ω turbulence model. ${u}_{i},{u}_{j},{u}_{k}$ represent the components of the cartesian velocities, and ${\sigma}_{k3}$ is a model constant.

#### 2.3. Volume of Fluid Equations

#### 2.4. Assessment Parameters

#### 2.4.1. Water Velocity (v)

#### 2.4.2. The Bottom Shear Stress (τ)

## 3. Methodology

#### 3.1. Conference

#### 3.1.1. Derosion Lattice (DL)

#### 3.1.2. Khao Rup Chang Beach

^{2}to creep into the shoreline. As expected, it was the most eroded area next to the rock dam structure. From the information from an expert of the Marine Department, Ministry of Transport, who is concerned and responsible for this problem, the end effect is severe during the northeast monsoon season, between October and December, when the water level, wind, and wave speed are high. To obtain accurate CFD-assessed results consistent with the actual beach profile, the necessary geological and climatic data, such as wind direction, bathymetric map, etc., were gathered from the consultants mentioned in Section 3.1 and analyzed to create the CAD models, mesh models, and the proposed conditions for simulation. In addition, the bathymetric map is included in a Supplementary Material File entitled Bathymetric_map.pdf.

#### 3.1.3. Proposed Conditions

- P0 is a case without the DL, used as a controlled case for comparison;
- P2/10° is a case with the DL placed at a position P2 with θ of 10°, etc.

#### 3.2. Models

#### 3.2.1. Fluid Model

^{3}(W × L × H) following the proposed conditions in Table 1. Compared with the dimension of the DL, we were confident that the scale of the fluid model we created was large enough to accurately monitor the waves’ flow behavior passing through the DL and the beach. Figure 7 reveals an example of a fluid model with dimensions consisting of the rock dam, sand floor, and adjustable angle of attack (θ). Lines in the sand floor represent the different depths created according to the bathymetric map. The further to the right, the deeper the water level. Accordingly, P1–P4 are the placement of positions mentioned earlier. P1 is 20 m away from the rock dam, P2 is toward the sea, P3 is overlapped with the rock dam, and P4 is adjacent to the rock dam.

#### 3.2.2. Dynamic Adaptive Mesh Model

#### 3.3. Boundary Conditions, Parameters Setting, and Analysis Setting

## 4. Results and Discussion

#### 4.1. Validation

#### 4.2. DL Performance Assessment

#### 4.3. A Proper Condition for the DL Installation

#### 4.3.1. A Proper θ

#### 4.3.2. A Suitable Placement Position

#### 4.4. Installation Outcomes

## 5. Conclusions and Suggestions

## Supplementary Materials

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**An explanatory diagram and overview of the end effect occurrence [1].

**Figure 17.**The installation outcomes: (

**a**) the first day of installation, (

**b**) viewed from the back, and (

**c**) viewed from the side, two months later after installation.

Case | Position | θ | Symbol |
---|---|---|---|

1 | P0 | - | P0 |

2 | P1 | 10° | P1/10° |

3 | P1 | 15° | P1/15° |

4 | P1 | 30° | P1/30° |

5 | P1 | 45° | P1/45° |

6 | P2 | 15° | P2/15° |

7 | P3 | 15° | P3/15° |

8 | P4 | 15° | P4/15° |

Name | Type | Value |
---|---|---|

Inlet | - -
- Velocity inlet
- -
- Open channel wave BC
- -
- Wave theory: third order Stokes
| Wave velocity = 3.496 m/s Water depth = 0 m (from MSL) Wave height = 0.5 m Wave length = 10 m |

Outlet | Pressure outlet | 0 Pa |

Top | Pressure outlet | 0 Pa |

Rock dam | Wall | - |

Wall | Wall | - |

Sym_F | Symmetry | - |

Sym_B | Symmetry | - |

Derosion Lattice | Porous media | Porosity = 0.68 Viscous resistance (inverse permeability) = 21,869.53 m ^{−2}Inertial resistance = 7.8335 m ^{−1} |

List | Setting |
---|---|

The pressure-velocity coupling method | SIMPLE |

Pressure spatial discretization | Body force weighted |

The gradient discretization | Least squares cell-based scheme |

The momentum | The second-order upwind |

The volume fraction | Compressive |

The turbulent kinetic energy | The second-order upwind |

Specific dissipation rate | The second-order upwind |

Transient formulation | Bounded second-order implicit |

Time advancement type | Adaptive: multiphase-specific |

Total time | 20 s |

Time step size | Initial: 0.006 s, Max: 0.006 s and Min: 0.00001 s |

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**MDPI and ACS Style**

Thongsri, J.; Tangsopa, W.; Kaewbumrung, M.; Phanak, M.; Busayaporn, W.
Derosion Lattice Performance and Optimization in Solving an End Effect Assessed by CFD: A Case Study in Thailand’s Beach. *Water* **2022**, *14*, 1358.
https://doi.org/10.3390/w14091358

**AMA Style**

Thongsri J, Tangsopa W, Kaewbumrung M, Phanak M, Busayaporn W.
Derosion Lattice Performance and Optimization in Solving an End Effect Assessed by CFD: A Case Study in Thailand’s Beach. *Water*. 2022; 14(9):1358.
https://doi.org/10.3390/w14091358

**Chicago/Turabian Style**

Thongsri, Jatuporn, Worapol Tangsopa, Mongkol Kaewbumrung, Mongkol Phanak, and Wutthikrai Busayaporn.
2022. "Derosion Lattice Performance and Optimization in Solving an End Effect Assessed by CFD: A Case Study in Thailand’s Beach" *Water* 14, no. 9: 1358.
https://doi.org/10.3390/w14091358