Tidal Flows and Coastal Processes
The Tidal Flows and Coastal Processes Research Group aims at the development of comprehensive numerical models for simulating tidal flows and coastal processes in estuaries and coasts. The modular models for adding in the CCHE2D and CCHE3D models are to extend the capabilities of the developed CCHE models for investigating estuarine and coastal processes including tidal waves, saltwater intrusion, water qualities, irregular wind-induced wave deformations, nearshore currents, sediment transport under the combination of waves and currents, and morphological processes.
Through developing and refining state-of-the-art numerical techniques for simulating tidal flows and coastal processes, the long-range goals of the research topics in the group are to
• Understand tidal flows and coastal/estuarine circulation processes and their impact on exchange of freshwater and saltwater, water quality, and sediment transport;
• Understand coastal and estuarine sedimentology and morphological processes in different coastal systems under irregular wave incidents due to tide, wind, and storm surge;
• Understand, through interdisciplinary research, the interactions of regional water environments between riverine and coastal/estuarine processes, and their regional impact on ecosystem and geomorphology, to facilitate the rehabilitation and sustainability of ecosystems, through the design, support and assessment of cost-effective engineering plans and management strategies.
The current research interests are focused on the following areas:
1. Development and validation of a two-dimensional coastal and estuarine circulation model capable of simulating tidal flows in coasts and estuaries (CCHE-TIDE), which has the abilities to
• Simulate tidal levels, tidal currents, residual currents in estuaries and coastal areas with complex bathymetries and boundary conditions;
• Model tidal flows with complex tributary inflows;
• Consider different external forces, e.g., non-uniform wind forces, Coriolis force, etc;
• simulate non-reflective open boundary conditions for the cases that the reflective waves need to be taken into consideration so that the tidal model can simulate not only long-wave tidal flows, but oscillatory flows with short periods;
• Simulate sediment transport by different empirical models in coastal/estuarine region;
• Modeling exchange of freshwater and saltwater, pollutant transport, and water quality in tidal flow environments.
2. Development and test of a three-dimensional unsteady free surface flow model which is capable of simulating the three-dimensional tidal flows in large-scale estuaries with the following capabilities, i.e.
• Simulating three-dimensional unsteady free surface flows with the assumption of hydrostatic pressure or non-hydrostatic pressure;
• Simulating three-dimensional oscillatory free surface flows with long and/or short periods;
• Modeling three-dimensional tidal flows in large-scale complex bathymetries and boundaries;
• Ability to handle non-reflective boundary conditions on open boundaries;
• Simulating exchange of fresh water and saltwater with consideration of variations of density, temperature, and salinity;
• Modeling sediment transport under 3D flow condition;
• High-performance computing.
3. Development and Integration of a process-based area model (CCHE2D-COAST) capable of simulating coastal processes including the capabilities of
• Modeling irregular wave deformation from offshore to onshore in complex shorelines;
• Modeling the wave-induced nearshore currents by considering radiation stresses in the shallow water models;
• Predicting wave set-up and wave set-down;
• Several options for selecting empirical formulations of sediment transport rate;
• Simulating morphodynamic changes in different coastal zones;
• Modeling different types of coastal structures in coastal zones, e.g. breakwaters, groins, artificial reefs, and so on;
• Handling “wetting and drying” in computation of shorelines;
• Considering non-equilibrium sediment transport with non-uniform size sediments which turns out to be an important field in the recent years;
Dr. Yan Ding
Dr. Mustafa Altinakar
2D numerical simulation of tidal flows in estuaries and coastal areas with complex bathymetry and boundary.
The CCHE2D-TIDE is an add-in module for CCHE2D to add the capability of simulating tidal flows in estuaries and coastal areas. The CCHE-TIDE extends the use of the CCHE2D for simulating tidal waves, tidal currents, and residual currents under the conditions of incident tidal waves (non-reflective), tributary flows, non-uniform wind force, and Coriolis force. The incident tidal waves at open-sea boundaries can be specified as time series of observed tidal levels or a combination of tidal constituents. In particular, the model provides non-reflective open boundary conditions for the cases that the reflective waves need to be taken into consideration. CCHE2D-TIDE has been tested and validated using various laboratory and field data.
The research group has developed a module for the CCHE3D model for simulation of three-dimensional tidal flows in large-scale and complex bathymetries. The CCHE3D hydrodynamic model together with the tide simulation module can simulate three-dimensional tidal waves, tidal currents, and residual currents under the conditions of incident tidal waves (non-reflective), tributary inflows, wind field, and Coriolis force.
Both 2D and 3D tidal models can simulate long-wave tidal flows and short-wave oscillatory free-surface flows. Click here to obtain more information on CCHE-TIDE.
2D simulation of irregular wave deformations, wave-induced nearshore currents, wave set-up and set-down, seabed change.
CCHE2D-COAST is a processes-based integrated model which is capable of simulating coastal processes in different coasts with complex shorelines such as irregular wave deformation from offshore to onshore, nearshore currents induced by radiation stresses, wave set-up, wave set-down, sediment transport, and seabed morphological changes. Formulations for sediment transport rate under the combination of wave and current are implemented in CCHE2D-COAST. It is, therefore, possible to simulate the seabed change around coastal structures (e.g. detached breakwater, groins, artificial reefs, etc). CCHE2D-COAST uses a wave model based on multi-directional spectral energy balance equation, which was validated by using different wave spectra. The nearshore current model and morphodynamic model were validated using laboratory and field data in coasts with different coastal structures.
Click here to obtain more information on CCHE2D-Tide and CCHE2D-COAST.
Ding, Y., and Wang, S. S. Y. (2005). “Optimal control of open channel flow using adjoint sensitivity analysis”, submitted to be published in ASCE Journal of Hydraulic Engineering.
Ding, Y., and Wang, S. S. Y. (2005). “Tests of capability and reliability of a model simulating coastal processes”, In: Proceeding of the World Water and Environmental Resources Congress 2005, Anchorage, Alaska, USA, May 15 – 19, 2005.
Ding, Y., and Wang, S. S. Y. (2005). “Identification of the Manning’s roughness coefficients in channel network using adjoint analysis”, International Journal of Computational Fluid Dynamics, Vol. 19, No.1, pp.3-13.
Kawahara, M., Kodama, T., and Ding, Y. (2005). “Tokyo bay test case”, to appear in Chapter 6 of the ASCE Monograph on 3D Free Surface Flow Model Verification and Validation.
Ding, Y., Wang, S. S. Y., and Jia, Y. (2004). “Development and validation of nearshore morphodynamic area model in coastal zone”, In: Advances in Hydro-Science and -Engineering, Vol.VI, Proceedings of the Sixth International Conference on Hydroscience and Engineering (CD-ROM), M. S. Altinakar, S. S. Y. Wang, K. P. Holz, and M. Kawahara eds., May 30-June 3, 2004, Brisbane, Australia.
Ding, Y., Jia, Y., and Wang, S. S. Y. (2004). “Identification of the Manning’s roughness coefficients in shallow water flows”, Journal of Hydraulic Engineering, ASCE, Vol. 130, No.6, pp.501-510.
Ding, Y. (2003). “Computation of leading eigenvalues and eigenvectors in the linearized Navier-Stokes equations using Krylov subspace method”, International Journal of Computational Fluid Dynamics, Vol. 17, No.4, pp.327-337.
Wang, S. S. Y., and Ding, Y. (2003). “On the verification and validation of coastal process simulation models”, In: Proceeding of the International Conference on Estuaries and Coasts (ICEC-2003), Nov.9-11, 2003, Hangzhou, China (Keynote Lecture).
Ding, Y., Wang, S. S. Y., and Jia, Y. (2003), “Numerical studies on simulations of waves and nearshore currents in non-orthogonal mesh system”, Proceedings of the International Conference on Estuaries and Coasts, Nov.9-11, 2003, Hanzhou, China, pp.719-726 (ISBN 7-900662-67-7/G - 79).
Ding, Y., Wang, S. S. Y. (2003). “Identification of the Manning’s roughness coefficients in channel network using adjoint analysis”, Twelfth International Conference on Finite Element Methods in Flow Problem, April 2-4, 2003, Nagoya, Japan (Invited Paper).
Ding, Y., and Wang, S.S.Y. (2003). “Test case database of tidal currents in Tokyo Bay for numerical model verification on 3-D free surface flow”, Technical Report No. NCCHE-TR-2002-11, National Center for Computational Hydroscience and Engineering, The University of Mississippi, Oxford, MS.
Ding, Y. (2002). “Enhancement of CCHE2D model for predicting tidal flows”, Joint Seminar of NCCHE and U.S. Department of Agriculture-Agricultural Research Service, Sept. 2002 (presentation file available).
Ding, Y., Jia, Y., and Wang, S. S. Y. (2001). “Identifying the Manning’s roughness in the CCHE2D model with Sakawa-Shindo method and limited-memory quasi-Newton methods”, Technical Report No. NCCHE-TR-2001-11, National Center for Computational Hydroscience and Engineering, The University of Mississippi, Oxford, MS.