Flood diversion tunnel on the Altbach in Kloten

Michel Kuhlmann, 22 March 2022

Hydraulic verification of structure dimensioning using 3D CFD multiphase modelling.

View of the inlet structure into the tunnel.

As part of the extension of the Glattalbahn from Zurich Airport via Kloten in the direction of Bassersdorf, a tunnel to relieve flood peaks of the Altbach is currently being planned on behalf of "VBG Verkehrsbetriebe Glattal AG". The verification of the structure dimensioning were done using numerical 3D-CFD multiphase modelling with a water and air phase.

In addition to showing the flow situation in the inlet, outlet and tunnel, the transient behaviour was simulated with initially empty and full tunnel.

The simulations were split up into three sub-models: Inlet, tunnel and outlet structure. Sensitivity of the mesh-discretisation and of the turbulence-model was investigated. The deposition of suspended load was approximated in a first step by Lagrangian particles. In addition, hydraulic parameters were provided, which served as boundary conditions for physical models of the inlet structure at the Laboratory of Hydraulics, Hydrology and Glaciology VAW of the ETH Zurich.

With the help of the numerical 3D modelling, an understanding of the flow of the entire structure for steady-state and transient conditions could be obtained and the dimensions of the structure could be confirmed.

Further information is available at glattalbahn.ch.

Sections of flow velocities in the inlet structure at HQ300.

Longitudinal section of flow velocities in the inlet shaft to the culvert tunnel at HQ300. Top: k-Epsilon turbulence model; Bottom: k-Omega SST turbulence model.

View of flow velocities in the outlet structure at HQ300.

Contact person

Michel Kuhlmann

Michel Kuhlmann

MSc. Env. Science ETH

Head of Division Surface Water/CFD

E-Mail:  michel.kuhlmann@tkconsult.ch
Tel.: +41 (0) 44 288 81 82