ENV5056 Numerical Modeling of Flow and Contaminant Transport in Rivers. Asst. Prof. Dr. Orhan GÜNDÜZ

Transcription

1 ENV5056 Numerical Modeling of Flow and Contaminant Transport in Rivers Introduction Asst. Prof. Dr. Orhan GÜNDÜZ

2 Course Outline 1. Basics 2. Fundamental Characteristics of Rivers 3. Flow Modeling 4. Contaminant Transport Modeling 5. Numerical Solution Procedures 6. Calibration 7. Model Packages 8. Model Applications 2

3 Basics Model Dimensionality 1-D Models: Typically along the flow direction 2-D Models: X-Y or X-Z planes 3-D Models: X-Y-Z domain Y (Transverse Dimension i.e., lateral direction) X (Direction of Flow) Z (Vertical Dimension i.e., depthwise) 3

4 Directions of Flow Y X Z 4

5 Model Selection 1-D Model: Typicalin river modeling, no major changes in flow and contaminant characteristics in transverse and vertical directions 2-D Model: Can be a depth-averaged model in X-Y plane (a shallow but wide river) or a transversely-averaged model in X-Z plane (a deep but not so wide river) 3-D Model: Most general model with all major directions considered, representing reality with highest accuracy 5

6 Some Examples of Model Selection 1-D model (shallow and narrow river) Ex: Fırtına Creek, Turkey 1-D model (possibly shallow and narrow river) 6

7 Some Examples of Model Selection 2-D model (X-Y) (a wide but possibly shallow river) Ex: Seine River, France 2-D model (X-Z) (a deep and moderately narrow river) Ex: Yangtze River, China 7

8 Some Examples of Model Selection 3-D model (X-Y-Z) (a wide and possibly deep river) Ex: Narmada River, India 3-D model (X-Y-Z) (a wide and deep river) Ex: Mississippi River, USA 8

9 Model Selection Model selection depends on a variety of factors: 1. Objective of modeling 2. Complexity required 3. Morphology of the river 4. Flow only or flow/transport modeling 5. Validity of assumptions to be used in reduced dimensionality modeling 6. Expertise of the modeler 7. Data availability (although this should normally not be a factor, in many cases, it is) 9

10 Common Modeling Packages 1. QUAL2K (1-D) 2. CE-QUAL-RIV1 (1-D) 3. CE-QUAL-W2 (2-D) 4. EPD-RIV1 (1-D) 5. WASP (1-,2-,3-D) 6. HEC-RAS (1-D) 7. EFDC (1-,2-,3-D) 8. AQUATOX (??) 10

11 QUAL2K QUAL2K is a river and stream water quality model that is intended to represent a modernized version of QUAL2E 1. One dimensional. The channel is well-mixed vertically and laterally. 2. Branching. The system can consist of a mainstemriver with branched tributaries. 3. Steady state hydraulics. Non-uniform, steady flow is simulated. 4. Diurnal heat budget. The heat budget and temperature are simulated as a function of meteorology on a diurnal time scale. 5. Diurnal water-quality kinetics. All water quality variables are simulated on a diurnal time scale. 6. Heat and mass inputs. Point and non-point loads and withdrawals are simulated. 7. Implemented within Microsoft Excel 8. Unequal segmentation possible 11

12 CE-QUAL-RIV1 CE-QUAL-RIV1 is a one-dimensional hydrodynamic and water quality model, that resolves longitudinal variations in hydraulic and quality characteristics and is applicable where lateral and vertical variations are small. 1. One dimensional structure 2. Unsteady model 3. Two components: Hydraulic model (RIV1H) and Water quality model (RIV1Q) 4. Hydrodynamic model solves St. Venant equations as the governing flow equations using the widely accepted four-point implicit finite difference numerical scheme 5. Water quality model could simulate 12 state variables: temperature, carbonaceous biochemical oxygen demand (CBOD), organic nitrogen, ammonia nitrogen, nitrate + nitrite nitrogen, dissolved oxygen, organic phosphorus, dissolved phosphates, algae, dissolved iron, dissolved manganese, and coliform bacteria. 6. Numerical accuracy for the advection of sharp gradients is preserved in the water quality code through the use of the explicit two-point, fourth-order accurate, Holly-Preissman scheme. 12

13 CE-QUAL-W2 CE-QUAL-W2is a water quality and hydrodynamic model in 2D (longitudinal-vertical) for rivers, estuaries, lakes, reservoirs and river basin systems. 1. Two dimensional structure (longitudinal and vertical) (laterally averaged) 2. Unsteady model 3. Widely applied to stratified surface water systems (narrow water bodies such as rivers, estuaries and reservoirs) 4. Solves for water levels, horizontal and vertical velocities, temperature, and 21 other water quality parameters (such as dissolved oxygen, nutrients, organic matter, algae, ph, the carbonate cycle, bacteria, and dissolved and suspended solids) 5. Implements 2-D hydrdynamicsand constituent transport routines: Quickest/Ultimate algorithms 13

14 EPD-RIV1 EPD-RIV1 is a one-dimensional (cross-sectionally averaged) hydrodynamic and water quality model. The computational model is based upon the CE-QUAL-RIV1 model. 1. One dimensional structure similar to CE-QUAL-RIV1 2. Hydrodynamics + Transport modules 3. Unsteady model 4. Simulates 16 state variables: water temperature, nitrogen species (or nitrogenous biochemical oxygen demand), phosphorus species, dissolved oxygen, carbonaceous oxygen demand (two types), algae, iron, manganese, coliform bacteria and two arbitrary constituents 5. The model was designed for the simulation of dynamic conditions in rivers and streams for the purpose of analyzing existing conditions and performing waste load allocations, including allocations of Total Maximum Daily Loads (TMDLs) 14

15 WASP WASP is a dynamic compartment-modeling program for aquatic systems, including both the water column and the underlying benthos. WASP allows the user to investigate 1, 2, and 3 dimensional systems, and a variety of pollutant types. 1. Can run in different dimensions (1-D, 2-D or 3-D) 2. Can also be linked with hydrodynamic and sediment transport models that can provide flows, depths velocities, temperature, salinity and sediment fluxes 3. Unsteady model 4. Variable complexity 5. Widely used till today 15

16 HEC-RAS HEC-RAS is a river analysis system that can perform one dimensional steady, unsteady flow hydraulic computations, sediment transport and water quality modeling 1. One-dimensional model 2. Designed for hydraulic computations in rivers 3. Can be run in steady and unsteady modes 4. Steady and unsteady water surface profiling in rivers 5. Sediment transport with moving bed boundary 6. Water quality analysis 7. Sophisticated GUI 8. GIS integration 16

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