Development and validation of a 3D numerical model to simulate floods in natural channels

George Constantinescu, Daniel Horna Munoz

Friday 3 july 2015

8:30 - 8:45h at Oceania Foyer (level 0)

Themes: (T) Flood risk management and adaptation, (ST) Flooding along in rivers and coasts

Parallel session: 14L. Floodrisk - Flooding

The paper discusses the development and validation of a 3D RANS model using the commercial code STAR-CCM+ to simulate flooding in natural streams. The Volume of Fluid (VOF) method is used to calculate the deformations of the free surface. The k-_ turbulence model is used to account for turbulence effects. Simulation results for this type of applications conducted on meshes containing 1-10 million grid cells show that the code scales well. Validation results are presented for a standard test case corresponding to steady flow in an S-shaped open channel of trapezoidal cross section. The predictions of the free surface deformations and streamwise velocity profiles in selected cross sections are found to agree well with experimental data. Then, the model is applied to predict flow and free surface elevations in a 1-km long reach of the Iowa River near Iowa City. The simulations successfully capture the centerline variation of the free surface elevation, while mass conservation errors are small across the domain. A main application of the present model will be to perform unsteady flow simulations corresponding to the propagation of a flood wave in natural channels and to assess the performance and limitation of popular 2D models used to predict flood propagation in natural environments.