 # Summary Water and Air Flow Numerical Techniques

##### Course
- Water and Air Flow Numerical Techniques
- 2020 - 2021
- Wageningen University (Wageningen University, Wageningen)
- Earth and Environment
176 Flashcards & Notes
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• There's various types of flow models, what is ours called?
Environmental flow models
• How do we describe environmental flow models?
In terms of balance equations, where balance equations are defined as fluxes
• Name 3 techniques that can be used to solve environmental flow models? Describe their characteristics

• Finite differences (solving equations on a spatial grid at the node)
• Finite volumes (budgeting flow in control volumes; representative area attached to node)
• Finite elements (budgeting flow in control volumes with more accuracy)
• How do internal and external fluxes differ?
Internal: advection & diffusion within the system
External: Spatial (2D) eg precipitation, line (1D) or point (locally) eg exit at water reservoir
• What is implied in finite volumes and why?
Conservation of mass, as representative areas are attached to the node and the edges of this volume are budgetted
• What is the difference between state variables and parameters?
State variable (s): change over time and describe state of system at certain time & space.
Parameters: given and fixed
• What do the terms of the advection/diffusion equation mean?
1) change of state over time
2) u: advection: transport with mean velocity
3) D: diffusion: spread of molecules/turbulence
• What is an ODE as explained by Chiel?
An equation that tells you how the state variable changes over time, as a function of the state variable itself and the time.
• Which form of ODE will we use in WANT, where s is the state variable?
Ds/dt = f (t,s)
• Environmental flow models are often about storage change and fluxes. How is this represented in the simple reservoir model?
Change in storage = sum of all fluxes