Numerical investigation of the solitary wave breaking over a slope by using the finite particle method

Understanding the dynamics of sediment transport and erosion-deposition patterns in the locality of a coastal structure is vital to evaluating the performance of coastal structures and predicting the changes in coastal dynamics caused by a specific structure. The nearshore hydro-morphodynamic responses to coastal structures vary widely, as these responses are complex functions with numerous parameters, including structural design, sediment and wave dynamics, angle of approach, slope of the coast and the materials making up the beach and structures. This study investigated the sediment transport and erosion-deposition patterns in the locality of a detached low-crested breakwater protecting the cohesive shore of Carey Island, Malaysia. The data used for this study were collected from field measurements and secondary sources from 2014 to 2015. Sea-bed elevations were monitored every two months starting from December 2014 to October 2015, in order to quantify the sea-bed changes and investigate the erosion-deposition patterns of the cohesive sediment due to the existence of the breakwater. In addition, numerical modelling was also performed to understand the impacts of the breakwater on the nearshore hydrodynamics and investigate the dynamics of fine sediment transport around the breakwater structure. A coupled two-dimensional hydrodynamics-sediment transport model based on Reynolds averaged Navier-Stokes (RANS) equations and cell-centered finite volume method with flexible meshing approach was adopted for this study. Analysis of the results showed that the detached breakwater reduced both current speed and wave height behind the structure by an average of 0.12 m/s and 0.1 m, respectively. Also, the breakwater made it possible for trapped suspended sediment to settle in a sheltered area by approximately 8 cm in height near to the first main segment of the breakwater, from 1 year after its construction. The numerical results were in line with the field measurements, where sediment accumulations were concentrated in the landward area behind the breakwater. In particular, sediment accumulations were concentrated along the main segments of the breakwater structure during the Northeast (NE) season, while concentration near the first main segment of the breakwater were recorded during the Southwest (SW) season. The assessment illustrated that the depositional patterns were influenced strongly by the variations in seasonal hydrodynamic conditions, sediment type, sediment supply and the structural design. Detached breakwaters are rarely considered for cohesive shores; hence, this study provides new, significant benefits for engineers, scientists and coastal management authorities with regard to seasonal dynamic changes affected by a detached breakwater and its performance on a cohesive coast.

Dynamics of Sediment Transport and Erosion-Deposition Patterns in the Locality of a Detached Low-Crested Breakwater on a Cohesive Coast

Chlorine residual plays a key role in determining the quality of treated water and wastewater One of the most critical factors affecting chlorine decay rates is flow and ambient temperature Detailed knowledge of temperature impacts on the efficiency and performance of chlorine contact tanks will enable optimum design and operation of water and wastewater treatment infrastructures This paper develops a robust and computationally efficient three-dimensional numerical simulation model using Reynolds-averaged Navier-Stokes equations (RANS) with k - e turbulence closure model A non-reactive tracer transport model is developed by implementing three-dimensional advection-diffusion equation The Chlorine decay processes are simulated using Reynolds-averaged species transport model Temperature effects on density and viscosity is simulated through Millero and, Poisson and Vogel equations, respectively Eight scenarios with variation in inflow and ambient temperature are simulated in this study The residence time distribution (RTD) and hydraulic efficiency indexes are determined for the simulation scenarios It is shown that small fluctuation in inflow and ambient temperature cause a significant change in chlorine concentration and performance of disinfection tank The analysis of numerical simulations indicated that increase in ambient and inflow temperature can increase chlorine decay by up to 75 %, leading to undesirable disinfection consequences and disruption of water treatment processes The numerical model developed within this study was successfully validated against experimental measurements and it is shown to be robust and efficient tool to determine optimum inflow and ambient temperature configurations for high-efficiency water treatment processes and to prevent microorganism residual and by-products disinfection formation The computational framework presented in this study can inform optimum design of water and wastewater treatment processes

Modelling solute transport in water disinfection systems: Effects of temperature gradient on the hydraulic and disinfection efficiency of serpentine chlorine contact tanks

Enhancing climate resilience of vertical seawall with retrofitting - A physical modelling study

https://doi.org/10.1016/j.watres.2022.119100

Gaussian process emulation of spatio-temporal outputs of a 2D inland flood model.

This study develops an accurate numerical tool for investigating optimal retrofit configurations in order to minimize wave overtopping from a vertical seawall due to extreme climatic events and under changing climate. A weakly compressible smoothed particle hydrodynamics (WCSPH) model is developed to simulate the wave-structure interactions for coastal retrofit structures in front of a vertical seawall. A range of possible physical configurations of coastal retrofits including re-curve wall and submerged breakwater are modelled with the numerical model to understand their performance under different wave and structural conditions. The numerical model is successfully validated against laboratory data collected in 2D wave flume at Warwick Water Laboratory. The findings of numerical modelling are in good agreement with the laboratory data. The results indicate that recurve wall is more effective in mitigating wave overtopping and provides more resilience to coastal flooding in comparison to base-case (plain vertical wall) and submerged breakwater retrofit.

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Dong Shudi

Papers

Application of smoothed particle hydrodynamics in evaluating the performance of coastal retrofit structures