Modelling Turbulent Flows near Coastal Structures Using Various Turbulence Models

Introduction. The reduction in beach width due to erosion is a significant issue that can either be mitigated or exacerbated by coastal protection structures. Modelling breaking waves near the coast and around coastal structures can be used to determine their impact on the dynamics of the coastal zone. The objective of this study is to model and analyze the dynamics of turbulent structures around a single breakwater, obtained using two turbulence modelling schemes: RANS and LES.
Materials and Methods. Turbulence induced by breaking waves was investigated. The modelling was based on bathymetric measurements conducted along the Azov Sea coast and a three-dimensional wave hydrodynamics model supplemented with various turbulence calculation configurations.
Results. Modelling results of wave processes generating turbulent flows in the presence of coastal protection structures using different turbulence models were obtained. Results obtained based on Reynolds-averaged Navier-Stokes (RANS) equations are compared with the results of Large Eddy Simulation (LES) approach with Smagorinsky dynamic subgrid-scale model (DSM).
Discussion and Conclusions. The results showed that wave heights simulated by LES were higher than those simulated by RANS in the front and leeward regions of the coastal protection structure and were lower in its upper part. Thus, according to LES, a greater amount of wave energy was preserved after passing over the breakwater. Velocity vectors of the water medium showed the formation of a vortex when LES was used, whereas no evidence of such turbulent vortices was detected in the case of RANS, confirming the better performance of LES for turbulence modelling in the coastal zone. According to the presented results, LES is the preferred tool for generating turbulence under incoming wave conditions in engineering practices.

1. Alekseenko Е., Roux B., Sukhinov А., Kotarba R., Fougere D. Coastal hydrodynamics in a windy lagoon. Nonlinear Processes in Geophysics. 2013;20(2):189–198. (In Russ.). https://doi.org/10.1016/j.compfluid.2013.02.003

2. Chang Y.S., Hanes D.M. (2004) Suspended sediment and hydrodynamics above mildly sloped long wave ripples. Journal of Geophysical Research – Oceans. 2004;109:07022. http://doi.org/10.1029/2003JC001900

3. Higuera P., Lara J.L., Losada I.J. Three-dimensional interaction of waves and porous coastal structures using OpenFOAM. Part I: Formulation and validation. Coast Engineering. 2014;83:243–258. https://doi.org/10.1016/j.coastaleng.2013.08.010

4. Kim Y., Zhou Z., Hsu T.-J., Puleo J.A. Large eddy simulation of dam-break-driven swash on a rough-planar beach. Journal Geophys Res-Oceans. 2017;122(2):1274–1296. https://doi.org/10.1002/2016JC012366

5. Lubin P., Vincent S., Abadie S., Caltagirone J.-P. Three-dimensional large eddy simulation of air entrainment under plunging breaking waves. Coast Engineering. 2006;53(8):631–655. https://doi.org/10.1016/j.coastaleng.2006.01.001

6. Miquel A.M., Kamath A., Chella M.A., Archetti R., Bihs H. Analysis of different methods for wave generation and absorption in a CFD-based numerical wave tank. Journal of Marine Science and Engineering. 2018;6:1–21. https://doi.org/10.3390/jmse6020073

7. Protsenko S., Sukhinova T. Mathematical modelling of wave processes and transport of bottom materials in coastal water areas taking into account coastal structures. MATEC Web of Conferences. 2017;132:04002.

8. Ranasinghe R., Larson M., Savioli J. Shoreline responses to a single shore-parallel submerged breakwater. Coastal Engineering. 2010;57(1):1006–1017. https://doi.org/10.1016/j.coastaleng.2010.06.002

9. Sukhinov A.I., Chistyakov A.E., Protsenko E.A. Mathematical Modelling of Sediment Transport in the Coastal Zone of Shallow Reservoirs. Mathematical Models and Computer Simulations. 2014;6(4):351–363. https://doi.org/10.1134/S2070048214040097

10. Sukhinov А.I., Sukhinov A.A. Reconstruction of 2001 Ecological Disaster in the Azov Sea on the Basis of Precise Hydrophysics Models. Parallel Computational Fluid Dynamics, Multidisciplinary Applications. 2005:231–238. https://doi.org/10.1016/B978-044452024-1/50030-0

11. Zhou Z., Hsu T.-J., Cox D., Liu X. Large eddy simulation of wave-breaking induced turbulent coherent structures and suspended sediment transport on a barred beach. Journal of Geophysical Research – Oceans. 2017;122:207–235.

12. The official website of Earth observing system. URL: https://eos.com/landviewer/account/pricing (accessed: 16.01.2024)

13. The official website of NASA Worldview. URL: https://worldview.earthdata.nasa.gov (accessed: 18.01.2024)

14. The official website of Roscosmos Geoportal. URL: www.gptl.ru (accessed: 20.02.2024)