Location: Watershed Physical Processes Research
2018 Annual Report
Accomplishments
1. Improved CCHE2D (Center for Computational Hydroscience and Engineering) model has been successfully validated and applied to watershed process analyses. Watershed hydrologic processes are modeled using simplified and parametric models for a long time, which simulate general watershed characteristics and processes. However, the predictions of many of these models are not strictly based on physics. A physically based hydrodynamic model for watershed overland flows, CCHE2D, has been developed and validated using multiple sets of experimental data by ARS researchers at Oxford, Mississippi. Data sets of measured velocities and water depth are rarely available for watershed studies. This is the first numerical simulation study utilizing measured overland flow velocity and water depth in 19 sets of experiments. The comparison of the simulation and the data indicated that the physically based numerical model produced good results: all the data measured over watershed slopes, in rills, gullies and tillage furrows, under a wide variety of experimental conditions: rainfall intensity, side in-flow, upstream in-flow, and soil types, are consistent with the model’s prediction. Four commercial licenses were granted to apply the model for individual use in their simulation projects.
2. An automatic mesh generation method has been developed and used in water resource software. Natural water bodies such as rivers and lakes have complex geometric forms which require to use irregular shaped meshes for computational models to solve water resource problems. Generating such meshes is, however, often time consuming. The faculty of the University of Mississippi, in collaboration with ARS researchers at Oxford, Mississippi, developed an automatic mesh generation method for applications with complex geometric domains. A complex shaped domain is decomposed into multiple blocks with a simpler shape to alleviate the generation difficulties; the overall mesh is then generated based on these identified blocks effectively. Studies have showed that the proposed method can successfully generate complex shaped meshes automatically and save time for overall numerical simulations.
3. An efficient mapping method for projecting topographic data to computational meshes has been developed. In CFD (Computational Fluids Dynamics) analysis in water resource related projects, topography elevation of land, riverbed, land-use mapping and other geometric distributions, have to be mapped by ARS researchers at Oxford, Mississippi, to a computational grid or mesh from a database of topography or other property distributions. This mapping is called interpolation. It is a crucial step of mesh generation that enables the computational model to recognize a specific physical problem and be used for numerical simulations. For any practice large research project, an accurate and reasonable interpolation takes a lot of calculation time. In this research, we have developed a fast interpolation method based on the idea of quick sorting optimization. According to large computation example cases, the computing time of the optimized interpolation method is reduced to less than 0.1% of the original method.
4. An update of the Center for Computational Hydroscience and Engineering (CCHE) pollutant transport and water quality model have been completed and made available to users. Water quality is an important environmental concern of human society. Water quality processes can be effectively simulated and evaluated using numerical models. The numerical models for simulating water quality and contaminant transport processes of the NCCHE, CCHE-WQ and CCHE-Chem models, have been thoroughly revised and connected to the user-friendly Graphic User Interface for easy simulation management and control. These updated models are currently being applied to simulate the water quality processes of the Pelahatchie Bay of the Rose Barnett Reservoir in Mississippi. The major objective is to study the process of the excessive sediment and nutrients in the bay induced by human activities. This is a research collaboration between ARS researchers at Oxford, Mississippi and researchers at the University of Mississippi at Oxford, Mississippi.
Review Publications
Zhang, Y., Jia, Y., Bingner, R.L. 2017. 2D automatic body-fitted structured mesh generation using advancing extraction method. Journal of Computational Physics 2. 353:316-335.
Jia, Y., Altinakar, M., Guney, M. 2017. Three-dimensional numerical simulations of local scouring around bridge piers. Journal of Hydraulic Research IAHR. DOI: https://doi.org/10.1080/00221686.2017.1356389.
Zhang, Y., Jia, Y. 2017. 2D Automatic body-fitted structured mesh generation using advancing extraction method. Journal of Computational Physics 2. 353(1)316-335 https://doi.org/10.1016/j.jcp.2017.10.018.
