Journal of Marine Science and Technology

Journal of Marine Science and Technology

numerical modeling of the Effect of Cylindrical Obstacles on coastal Waves using OpenFOAM

Document Type : Original Manuscript

Authors
Fatameh Ghasemi Pirbalouti 1
Elham Ghanbari Adivi 1
Rohollah Fatahi Nafchi 1
Ehsan Khavasi 2
1 Department of Water Engineering, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran.
2 Department of Mechanic Engineering, Faculty of Engineering, Zanjan Universi, Zanjan, Iran.
10.22113/jmst.2022.354486.2489
Abstract
ABSTRACT
One of the coastal protection techniques is the use of breakwaters. This study aims to investigate the effect of pile breakwaters on coastal waves. These breakwaters are similar to a porous structure. They are preferred over other impenetrable coastal structures due to their increased roughness and resistance to the current, their relatively low cost, economic savings, greater environmental compatibility, and preservation of natural landscapes. Considering rigid cylindrical obstacles on the coast with constant slopes, the effect of their roughness on flow patterns and waves by numerical modeling in OpenFOAM software was investigated. The method used in flow modeling is the RANS method and k-ω, SST model.
Modeling was performed in two modes with and without barriers for three different heights of wave. The results were compared with laboratory data. The absorbed force for wave height of 6, 9, and 12 cm in the numerical model was 17.14, 4.23, and 7.86 percent, respectively, with the laboratory model, Also, the mean square root of normal error was 0.07, and the correlation coefficient was 0.99, which indicates the conformity of two numerical and laboratory models and the appropriate performance of Open FOAM software in modeling.
Keywords: Coast protection, Pile breakwater, Wave energy,
 

INTRODUCTION

Coastal zones are dynamic ecosystems where land meets the sea, characterized by their variability due to natural factors and human activities. Climate change has made these areas more susceptible to extreme weather events and natural disasters, such as storms and flooding. Acknowledging the value of our shores, it is imperative to enhance our understanding of coastal engineering and to implement diverse and effective strategies for shoreline protection. Employing breakwaters is one method of safeguarding our beaches. This research examined the impact of Cylindrical Obstacles on wave patterns through computational simulations conducted in the OpenFOAM software.

MATERIALS AND METHODS

The numerical model was set up and executed using Open Foam software. For this two-phase flow issue, the interFoam solver, improved with the Volume of the Fluid method, was utilized for simulations. Turbulence in the flow was represented using the Reynolds-averaged Navier-Stokes (RANS) equations and the k-ω SST
turbulence models. The model was performed in two modes with and without barriers for three different heights of wave. Rigid cylindrical obstacles had a diameter of 0.9 cm and a height of 32 cm. They were contracted at a length and width of 45×45 cm and distances of 15×15 cm, with staggered layout. In all three wave heights, the presence of obstacles greatly causes the force of waves to dissipate relative to the unobstructed state.

Results

With wave heights of 6, 9, and 12 cm, the obstacles dissipated 47.17, 68.68, and 76.42 percent more than the unobstructed state of wave force, respectively. As the wave height increases, the obstacles absorb more force. At a wave height of 12 cm, obstacles to a wave height of 9 and 6 cm, respectively, 32.35 and 72.45 (compared to no force dimension) absorbed more power. In the discussion of wave mortality in obstacle scenarios compared to unobstructed scenarios, the ability of obstacles to reduce wave height and its mortality averaged 20.88%. The percentage of wave attenuation decreases with increasing wave height, and obstacles reduce a smaller percentage of water height The highest decrease in wave height was related to the wave height of 6 cm, and the lowest decrease was related to the wave height of 12 cm by 84.44% and 47.98%, respectively. The presence of obstacles in the path of wave movement causes a decrease in the speed of the wave and creates a separation zone behind the barriers. Therefore, the wave passes through the protected area and enters the coastal area over a longer period.

DISCUSSION AND CONCLUSION

The results were compared with laboratory data. The absorbed force for wave height of 6, 9, and 12 cm in the numerical model was 17.14, 4.23, and 7.86 percent, respectively, with the laboratory model, Also, the mean square root of normal error was 0.07, and the correlation coefficient was 0.99, which indicates the conformity of two numerical and laboratory models and the appropriate performance of Open FOAM software in modeling. From the general comparison of the results, the creation of an area with rigid cylindrical barriers on the sea face of the coast helps to protect the coast from the advance of the waves and their flooding.
Keywords
Coast protection
Pile breakwater
Wave energy
k-ω
SST

Subjects

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Journal of Marine Science and Technology
Volume 23, Issue 3
Summer 2024
Pages 22-38

  • Receive Date 30 August 2022
  • Revise Date 18 December 2022
  • Accept Date 24 December 2022
  • Publish Date 22 July 2024