Subject: Numerical modelling of scour erosion near obstacles of arbitrary shapes 

A full-time Ph.D. position is open at Ecole de Technologie Supérieure (ETS) in Montréal (QC, Canada).

THE PROJECT:
Context:
The use of CFD codes in mechanical, civil and environmental engineering has been increasing over time, however, CFD is still difficult to use when a wide range of flow conditions (meteorology, oceanology, climate change) needs to be assessed due to its computational cost.
The computational cost depends on the cost of one single run but also on the number of runs needed to evaluate the occurrence of the quantity of interest.
CFD-based methods have fewer limitations about complex geometries, breaking waves, non-linear phenomena and represent a valuable alternative for many problems. And, in response to high computational cost, the simplistic or academic test cases can be a suitable methodology for error assessment with a focus on physical process, because runs are shorter, and also their number might be reduced.

 
Figure 1: Flow pattern near bridge pier and abutment [4]



PhD Topic :
The PhD project is focused on Sediment transport in natural environment as an key issue for sustainable development. For example, sediment management in harbours generates expensive costs to maintain nautical bottom and ensure security for navigation. On the other hand, scour erosion in the vicinity of hydraulic structures such as bridges, dykes and coastal protections can destabilize or even destroy them.
Two categories of models are now available to simulate or predict sediment transport and its consequences in natural environment. The first one is traditionally based on single phase or passive tracer assumption [1]. The velocity of solid particle (sediment) is assumed equal to the velocity of the fluid carrying particle (water) except for the vertical component. The second one is based on a more rigorous treatment for the sediment phase by the two-phase approach. This new formalism enables description of velocity difference between dispersed (solid particles) and continuous (fluid) phases and authorizes momentum transfer between them. A comparison of both types of models has already been performed on sediment dumping cases [2]. Such a comparison has highlighted that the two-phase based simulations is able to capture flow pattern and sediment plume more realistically than the single-phase based models. As a consequence, the prediction of deposition or impact zone is more accurate by considering the two-phase model and some limitations of the traditional single phase model have been pointed out.
The purpose of this PhD research project is to perform similar comparisons between single and two phase based models on scour erosion near hydraulic (fluvial or coastal) structures. In this study, we will consider scouring processes near hydraulic structures which are founded on an erodible (sandy) bed under the effect of a current or wave. The 3D complex flow pattern (Figure1) presenting flow recirculation (horseshoe vortexes, Von Karman street), streamline deflection would be captured by using two available numerical models: the open source code NSMP3D [3] will be considered as research code as two-phase model. Comparison would be made on the geometry (shape and size) of scour holes, the flow patterns and turbulence. Validation of both models would be done on well-documented and academic test cases. Finally the models would be applied to a real case by considering field data by partners.
References : 
[1] C. VILLARET, L.A. VAN, N. HUYBRECHTS, D. PHAM VAN BANG, O. BOUCHER, 2010: Consolidation effects on the morphodynamics modelling: application to the Gironde estuary, La Houille Blanche, n°6-2010, 15-24.
[2] D.H. NGUYEN, F. LEVY, D. PHAM VAN BANG, K.D. NGUYEN, S. GUILLOU, J. CHAUCHAT,  2012: Simulation of dredged sediment releases into homogeneous water using a two-phase model, Advances in Water Resources, Vol. 48, 102-112.
[3] M. UH ZAPATA, D. PHAM VAN BANG, K.D. NGUYEN, 2014: An unstructured finite volume technique for the 3D Poisson equation on arbitrary geometry using a σ-coordinate system, International Journal for Numerical Methods in Fluids, DOI: 10.1002/fld.3945.
[3] M. HURTADO-HERRERA, M. UH ZAPATA, A. HAMMOUTI, D. PHAM VAN BANG, W. ZHANG, K.D. NGUYEN, 2024. Numerical investigation  of the scour around a diamond- and square-shaped pile in a narrow channel, Ocean Eng., 309(1), #118374
[4] G. HOFFMANS, 2012: The influence of turbulence on soil erosion, ISBN 9789059726826, Eburon, 248p.


PROFILE OF THE CANDIDATE:
•	Candidates should hold a Master's degree in Mechanical Engineering, Civil Engineering, Ocean Engineering, Fluid Mechanics, Numerical Analysis, or related topics.
•	Experience in scientific computing and in english environment will be a plus.
•	Linux/Unix
•	Python/Matlab/Fortran90

SCHEDULE AND CONDITIONS
Schedule:
Candidates are invited to contact Prof. D. Pham Van Bang (damien.pham-van-bang@etsmtl.ca) and Dr. Abdelkader Hammouti (abdelkader.hammouti@etsmtl.ca) via email, with a CV, a motivation letter and a transcript of Master degree.

Candidatures received after October 15th, 2024 will not be considered.
Talks with pre-selected candidates will be organized via video conferencing and the final decision should be available on November 15th.
The successful candidate is expected to be enrolled on May 1st, 2025 to start PhD program.

Conditions of employment:
The candidate will be funded for 40 months (10 sessions). The PhD scholarship is 2200 CAD/month during the first year, then 2300 CAD/month after completion of the Doctoral examination.