A superposition lattice Boltzmann approach to a 1D-2D shallow water system
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Abstract:
A superposition coupling method (SCM) is proposed to achieve high-precision cross-dimensional simulation coupling of one-dimensional and two-dimensional lattice Boltzmann method (LBM) hydrodynamic model. Hydrodynamic simulation of shallow water systems in complex topographic regions often requires cross-dimensional modeling, which can introduce boundary approximation issues, particularly in scenarios such as river-lake junctions, floodplains, and estuary areas. To solve the shallow water equations (SWE) in cross-dimensional scenarios, the SCM involves creating an artificial overlapping zone at the boundary of the 1D and 2D LBM models, facilitating the exchange of hydrodynamic information between the two models. Within this overlapping zone, a zero-gradient boundary condition is applied to derive the necessary variables for coupling. The 1D-2D coupled model was validated against benchmark models for circular cavity jet flow and sharp curved channel flow, demonstrating comparable accuracy to the full 2D model. In shallow water flow numerical simulation, typically different dimensional models are employed based on the topography and topology of the flow, which are crucial factors influencing water body movement. 1D models are generally more efficient for simulating the movement characteristics of large river channels, while 2D models are more suitable for large bodies of water with extensive free surfaces, such as floodplains, lakes, or reservoirs, provided accurate topographic data is available. Consequently, 1D and 2D models are often coupled to leverage their respective advantages. The proposed 1D-2D LBM coupling method utilizes a superposition approach, where the two models share an overlapping zone at their boundary. This zone serves as a buffer for exchanging hydrodynamic information between the models. The zero-gradient boundary condition is applied within the overlapping zone to ensure mass and momentum conservation. The method was implemented by calculating the velocity and depth at the boundaries of the 1D and 2D models and using these values to update the particle distributions within the overlapping zone. This process was iterated until convergence was achieved. The proposed coupling model was evaluated in comparison to benchmark models for circular cavity jet flow and sharp curved channel flow. The results showed that the coupling model produced water depth and velocity profiles that were in good agreement with those of the full 2D model, with minimal differences. The root mean square errors (RMSE) for water depth and velocity were within acceptable ranges, indicating the accuracy and reliability of the coupling method. The superposition approach for coupling 1D and 2D LBM hydrodynamic models provides a robust and efficient solution for simulating shallow water flows in complex topographic regions. The method leverages the strengths of both 1D and 2D models, providing accurate and reliable results while maintaining computational efficiency. The successful application of this method expands the capabilities of LBM in hydrodynamic simulation and demonstrates its potential for solving other multi-dimensional coupling problems, such as 1D-3D coupling or solute transport coupling.