Assessment of the Capability of 3d Stratified Flow Finite Element Model in Characterizing Meander Dynamics

Abstract

There have been attempts to simulate meander dynamics (Langbein and Leopold 1966, Oodgard 1989, Campoerale et. al 2007, da Silva and El-Tahawy 2008, Duan and Julien 2010, Blanckaert and de Vriend 2010, Esfahani and Keshavarzi 2011). Meandering geometry is complex phenomena (Chanson 2004, Wu 2008), this would include the dynamics of flow properties and of morphology. Simulating meander flow dynamics is mostly popular using either Finite Element Method (FEM) or Finite Volume Method (FVM) where are based on Eulerian description, and based on stationer grid-based methods (Wormleaton and Ewunetu 2006, Wu 2008, Duan and Julien 2010, Gomez-Gesteira et. al 2010). As such this model is lack of capability in simulating the dynamics of meander morphology; much effort is put through to overcome this issue with such as Smoothed Particle Hydrodynamics (SPH), Boundary Element Methods, Arbitrary Lagrangian Eulerian, etc. This paper has two objectives; to identify meander flow characteristics and sediment transport distribution patterns, and to simulate meander flow characteristics and sediment transport distribution patterns using FEM. This study has identified that the key of dynamics of flow characteristics are helical flow and coherent structures, and the key of dynamics of transport characteristics are erosion-deposition zone patterns. The finite element model using in this study, RMA has shown its capability to simulate the meander key characteristics above, for small deflection angles (30°) location of maximum erosion-deposition zones near the crossover of the sinuosity, for intermediate deflection angles (70°) location of maximum erosion-deposition zones between the crossover and apex of the sinuosity, and for large deflection angles (110°) location of maximum erosion-deposition zones near the apex of the sinuosity, these are agreed with experiments of Odgaard 1989, da Silva 2006, da Silva et. al 2006, and Esfahani and Keshavarzi (2012). These results can be used as a reference to develop a method to model meander morpho-dynamics.

Evaluation of Wastewater Discharge Reduction Scenarios in the Buenaventura Bay

“…A coupling scheme combining the RMA10 3D hydrodynamic and RMA11 water quality models was used to simulate the hydrodynamic and water quality conditions in Buenaventura Bay. The RMA10 model simulates the velocity, pressure, and sediment fields in three dimensions [11][12][13][14]. The system of equations that the model solves is described from equations (1) to (6).…”

“…Where x, y, and z are the coordinates of the Cartesian system; 𝑢𝑢, 𝑣𝑣, and 𝑤𝑤 are the velocities in the directions of the Cartesian system, p is the water pressure, t is time, ε xx , ε xy , ε xz , ε yx , ε yy , ε yz , ε zx , ε zy , ε zz are the eddy turbulence coefficients, g is the acceleration due to gravity, 𝐷𝐷 𝑥𝑥 , 𝐷𝐷 𝑌𝑌 , and 𝐷𝐷 𝑧𝑧 are the eddy diffusion coefficients, 𝜌𝜌 is the density of water, Γ x , Γ y , and Γ z are the external forces; 𝜃𝜃 is the salinity, and 𝜃𝜃𝜃𝜃 is the salinity source/sink. The RMA11 model, which uses the finite element method, has been used successfully to model water quality in estuaries, bays, lakes, and rivers [15][16][17][18]. It receives the velocity, temperature, and salinity fields from the RMA10 model and uses them to solve the advection-diffusion constituent transport equations [15].…”

“…The RMA 10 model used sigma coordinates and modified the system of equations to account for changes in the water surface elevation due to tides. The details of the modification can be found in the references Marthanty et al [11] and Fosati et al [12]. The finite element mesh was discretized into five layers in the vertical direction.…”

Evaluation of Wastewater Discharge Reduction Scenarios in the Buenaventura Bay

“…A one-way coupling scheme was used to couple the hydrodynamic model (RMA10) and the water quality model (RMA11), as shown in Figure 3. The RMA10 model simulates the velocity, pressure, and sediment fields in three dimensions [17][18][19][20]. Equations ( 1)-(6) describe the system of equations that the model solves.…”

“…The RMA10 model used sigma coordinates and modified the system of equations to account for changes in the water surface elevation due to tides. Details of the modification can be found in the references by Marthanty et al [17] and Fosati et al [18]. The finite element mesh was discretized into five layers in the vertical direction.…”