Numerical investigation of the effect of using a combined design of coastal wall and coastal forest in the protection and beaches stability

Due to the strategic importance of coastal areas from various aspects, their protection against waves is considered a necessity in the management and sustainable development of beaches, in this research, an attempt has been made to investigate the effective method of protecting the coastal environment, such as trees, in addition to protective structures and compared to the purely structural method, the depreciation of coastal waves and as a result the protection of beaches should be investigated in a more comprehensive way. The method used in the flow modeling is Reynolds Averaged Navier-Stokes (RANS) and (k-ω, SST) model, which is done in Open FOAM software platform. The coastal wall structure of the coastal dike structure in combination with trees was investigated under the influence of 5 different incoming wave heights. The research done with the help of the numerical model showed that the damping and weakening of the waves in the mentioned conditions compared to the beach without protection has provided acceptable results. In the most influencing of wave weakening in terms of power, the presence of coastal wall structure, dyke structure and forest cover of the coastal forest was able to help absorb the force of the waves by 1.2 times compared to the unobstructed beach, and on the other hand, the height of the wave passing by the beach was also 4.36 times compared to unobstructed mode, reduce further. The results were compared with the laboratory data. The results of numerical models were compared with the corresponding laboratory model. In this comparison, the root mean square of the normal error was 0.42 and the correlation coefficient was 0.98, which indicates the good accuracy of the numerical model and the appropriate performance of the Open FOAM software in modeling.