# 3D numerical morphodynamic models

# 3D numerical morphodynamic models

## Type

Hydromorphological models

### Basic principles

Fundamental equations for conservation of water mass and water flow momentum, time-averaged over all turbulent fluctuations (RANS = Reynolds Averaged Navier-Stokes equation) or time-averaged over only the smaller turbulent fluctuations (LES = Large Eddy Simulation). Lagrangian equations for pickup, transport and deposition of sediment particles. Exner equation for conservation of sediment mass.

### Outputs

Flow velocities, water depths, water levels, flow shear stresses. Sediment transport, bed level, erosion, sedimentation.

## Rivertypes

## Related Pressures

- Alteration of instream habitat
- Sand and gravel extraction
- Sedimentation and sediment input
- Embankments, levees or dikes
- Loss of vertical connectivity
- Impoundment
- Alteration of riparian vegetation
- Channelisation / cross section alteration

## Related Measures

- Reduce anthropogenic flow peaks
- Modify hydropeaking
- Shorten the length of impounded reaches
- Increase flood frequency and duration in riparian zones or floodplains
- Favour morphogenic flows
- Link flood reduction with ecological restoration
- Ensure minimum flows
- Manage aquatic vegetation
- Establish environmental flows / naturalise flow regimes
- Create low flow channels in over-sized channels
- Narrow water courses
- Widen water courses
- Allow/increase lateral channel migration or river mobility
- Remeander water courses
- Shallow water courses
- Add sediments
- Modify aquatic vegetation maintenance
- Initiate natural channel dynamics to promote natural regeneration
- Introduce large wood
- Remove sediments
- Remove bank fixation
- Remove or modify in-channel hydraulic structures
- Reduce impact of dredging
- Recreate gravel bar and riffles

## Useful references

### Selected software systems

Delft3D: http://www.deltaressystems.com/hydro/product/621497/delft3d-suite

FLOW-3D: http://www.flow3d.com/

iSed

SSIIM: http://folk.ntnu.no/nilsol/ssiim/

TELEMAC-3D

### Theoretical background

Hervouet J.M., Hubert J.-L., Janin J.-M., Lepeintre F., Peltier E. (1994): The computation of free surface flows with TELEMAC: an example of evolution towards hydroinformatics. Journal of Hydraulic Research, 32, extra issue, pp. 45-64. http://www.tandfonline.com/doi/abs/10.1080/00221689409498804

Olsen N.R.B (1999): Computational Fluid Dynamics in Hydraulic and Sedimentation Engineering. Class Notes, Norewgian University of Technology, Trondheim.

Tritthart M. (2005): Three-Dimensional Numerical Modelling of Turbulent River Flow using Polyhedral Finite Volumes. Wiener Mitteilungen Wasser-Abwasser-Gewässer, Band 193, Institut für Wasserbau und Ingenieurhydrologie, TU Wien. http://www.hydro.tuwien.ac.at/uploads/media/Wiener-Mitteilungen-Band-193_01.pdf

Tritthart M. and Gutknecht D. (2007): Three-Dimensional Simulation of Free-Surface Flows using Polyhedral Finite Volumes. Engineering Applications of Computational Fluid Mechanics, 1, pp. 1-14. http://jeacfm.cse.polyu.edu.hk/

### Sample applications

Olsen N.R.B (2000): A three-dimensional numerical model for simulation of sediment movements in water intakes with multiblock option. User´s Manual, Norwegian University of Science and Technology, Trondheim.

Olsen N.R.B. (2000): CFD modeling of bed changes during flushing of a reservoir. Proc., Hydroinformatics 2000, Iowa, USA.

Olsen N.R.B. (2002): Estimating meandering channel evolution using a 3D CFD model. Proc., Hydroinformatics 2002, Cardiff, pp.52-57. ISBN: 9781843390213

Tritthart M., Schober B., Liedermann M., Habersack H. (2009): Development of an Integrated Sediment Transport Model for a Large Gravel Bed River. Proceedings, 33rd IAHR Congress, Vancouver, Canada.