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Home > Teams > MEIGE team > Research Topics > Environmental Engineering

Scour around structures

(J. Chauchat)

When a hydraulic structure is placed in a flow, its presence will modify the flow pattern in its vicinity resulting in various processes such as flow contraction, horseshoe vortex formation upstream the structure, lee-wake vortices formation or pressure differentials in the soil. These mechanisms can strongly affect the local sediment transport capacity and can lead to the formation of a scour hole around the structure or liquefaction. Scour is probably the primary cause of bridge failure. In the state-of-the-art models the local sediment transport rate is parameterized based on the local fluid bed shear stress and the local bed slope by using empirical formula obtained in steady and uniform channel flows. The physical mechanisms associated with the presence of a structure mentioned above are not accounted for in a physically consistent way. During T. Nagel PhD we have demonstrated the capability of the turbulence averaged two-phase flow model to reproduce the scour phenomenon around a vertical cylinder (see movie).

Two-phase flow simulation of scour around a vertical cylinder performed with sedFOAM (k-omega-Wilcox2006 turbulence model and mu(I) rheology). PhD T. Nagel 2018 - French ministry of research/COOPERA project funded by région ARA.

The same model has been applied to the configuration of a pipeline deposited on a sand bed by A. Mathieu (Master Thesis, 2017). The model is able to reproduce the 3 stages of scour: the onset, the tunneling and the lee-wake erosion stage. Some improvements are still needed especially concerning the onset where the pore pressure feedback on the granular rheology should probably be taken into account. The interaction between lee-wake vortices and sediment dynamics also requires further work.

Two-phase flow simulation of scour around a horizontal cylinder performed with sedFOAM (k-omega-hybrid turbulence model and mu(I) rheology). Master thesis of A. Mathieu 2017 - funded by ANR Segsed.

Funding :
-  COOPERA/bourse CMIRA région ARA (2015-2017) – PI J. Chauchat

PhD Students
-  Thèse T. Nagel (IMEP2 2014-2018)
-  Master A. Mathieu (ANR SegSed 2017)
- collab. Prof. T.-J. Hsu (Univ. Delaware, USA)
- collab. Prof. X. Liu (Penn State Univ., Pennsylvania, USA)