Events

Civil and Environmental Engineering PhD Dissertation Defense: Hussein Al-Zubaidi
Wednesday, May 23, 2018 - 10:00am

The Department of Civil and Environmental Engineering is pleased to announce Hussein Al-Zubaidi's PhD Dissertation Defense: "3D Hydrodynamic, Temperature, and Water Quality Numerical Model for Surface Waterbodies: Development, Verification, and Field Case Studies."

Date: Wednesday, May 23, 2018
Time: 10:00am
Location: Engineering Building 315
Adviser: Dr. Scott Wells

Numerical modeling has become a major tool for managing water quality in surface waterbodies such as rivers, lakes, reservoirs, and estuaries. Since the two-dimensional longitudinal/vertical model CE-QUAL-W2 is a well-known model and it has been applied to thousands of waterbodies around the world successfully, its numerical scheme was adapted to develop a new three-dimensional numerical model for simulating hydrodynamics, temperature, and water quality in surface waterbodies. Finite difference approximations were used to solve the fluid dynamic governing equations of continuity, free water surface, momentums, and mass transport. No coordinate transformations were performed and the z-coordinate system has been used. A novel numerical approach was used for the numerical formulation of the three-dimensional scheme. This approach forced the numerical solution of the free surface equation to be a tri-diagonal matrix form rather than a more computationally intensive penta-diagonal matrix solution. This new approach was done by linking a method called line-by-line with the free water surface numerical solution. Another new approach was that the three-dimensional numerical scheme involved a simultaneous solution of hydrodynamics and water quality at every model time level instead of saving the hydrodynamic results to be used later for water quality simulation. Hence, this scheme allowed feedback between the hydrodynamics and water quality every time step. In addition, various unique numerical algorithms were employed from CE-QUAL-W2 such as the W2 turbulent model, selective withdrawal theory, surface heat fluxes, and water quality sources and sinks, making the three-dimensional model built on well-tested algorithms in field. To test the model structure and assumptions, an analytical verification was performed by comparing model predictions to known analytical exact solutions test cases. Good agreement was showed by the model for all of these tests. Model errors were evaluated by incorporating within the model a computation of the
volume balance over the simulation period. Sensitivity tests were also made varying bed and wind shear.

The model was also applied to three reservoirs in the USA as field case studies (Lake Chaplain in WA, Laurance Lake in OR, and Cooper Creek Reservoir in OR). The model was validated by comparing the model predictions of water levels, velocities, vertical temperature profiles, and dissolved oxygen with field data. Through these real applications, we showed the good agreement of the 3D model predictions with field data in terms of error statistics. The model results of each field case study were discussed separately.