Associate Research Fellow  | Flow & Morphology

EIT Member of PEO and APEGBC, Canada

Mohsen Ebrahimi

May 2015 - Present

This is an ongoing project for studying debris effects on hydrodynamics and scour at pier/bridges having a geometry similar to that of masonry bridges. I do the experimental phase of the project in a 0.65m-wide recirculating flume. Pier/bridges blocked by debris will be physically modelled to investigate debris effect on flow velocity pattern, scour and hydrodynamic pressure and forces. For further information, please refer to the project blog here

Following papers are published 

  • Ebrahimi, M., Kahraman, R., Kripakaran, P., Djordjević, S., Tabor, G., Prodanović, D.M., Arthur, S., Riella, M. (2017). “Scour and Hydrodynamic Effects of Debris Blockage at Masonry Bridges: Insights from Experimental and Numerical Modelling.” 37th IAHR World Congress, Kuala Lumpur, Malaysia.
  • Ebrahimi, M., Kripakaran, P., Djordjević, S., Tabor, G., Prodanović, D.M., Arthur, S., Kahraman, R. (2016). “Hydrodynamic Effects of Debris Blockage and Scour on Masonry Bridges: Towards Experimental Modelling” 8th International Conference on Scour and Erosion, Oxford, UK.

with the following one in preparation stage

  • ​Ebrahimi, M., Kahraman, R., Riella, M., Kripakaran, P., Djordjević, S., Tabor, G., Prodanović, D.M., Arthur, S., Kahraman, R. “Experimental study of scour due to debris blockage at a masonry-like bridge pier.”
  • Ebrahimi, M., Kripakaran, P., Djordjević, S., Tabor, G., Prodanović, D.M., Arthur, S., Kahraman, R. “Physical modelling of debris in morphological experiments: A review.”

​Risk assessment of masonry bridges under flood conditions: hydrodynamic effects of debris blockage and scour

Centre for Water Systems, University of Exeter, United Kingdom

Sept. 2006 - Sept. 2008

Two cases of 2D vertical morphological changes in channel flows were simulated in this project. In the first case, scour in transition from a fixed-bed to an erodible bed was simulated, and the results were verified using available experimental data. In the second case, trench migration was simulated and results were validated using data from previous researchers. Simulations were carried out via programming in Fortran, where sediment transport and morphological modules were added into a previously developed non-hydrostatic current model with k-ε turbulence model.

In this project, sediment concentrations in the flow field were calculated via solving advection-diffusion equiation using finite volume method and time-splitting technique in a rectangular boundary fitted coordinate system. Advection equation was solved explicitly by the 1st-order backward  scheme, and diffusion equation was solved implicitly using double-sweep algorithm. Boundary condition of sediment concentration at the bed was identified using the stochastic method introduced by van Rijn.

This project resulted in the following publications:

  • Ebrahimi, M. (2008). "Numerical modeling of deformation of alluvial bed in rapidly varied flow." MSc Thesis, University of Tehran, Iran (In Persian).
  • Ebrahimi, M., Badiei, P. (2008). “Simulation of sedimentation in trenches using a two-dimensional vertical numerical model.” Proc. 8th International Conference on Coasts, Ports, and Marine Structures, Tehran, Iran, November 2008, pp. 145-148.
  • Ebrahimi, M., Badiei, P. (2008). “Numerical simulation of sediment transport in a two-dimensional unsteady, rapid flow.” Proc. 4th National Conference of Civil Engineering, Tehran, Iran, Apr. 2008, Vol. 2 (In Persian).

Numerical modeling of 2D scour and trench migration in rapidly varied flow

Dept. of Civil Engineering, University of Tehran, Iran


Jan. 2009 - Jan. 2015

Jan. 2009 - Jan. 2013

In this project, which was again carried out under constructive supervision of Professor Ana Maria da Silva, a method to fix movable beds in river-related laboratory research or physical model studies was proposed. The method avoids using harsh chemicals and ensures that the granular roughness of the original movable bed is maintained.

This methods uses sand-cement mixture for stabilizing the movable boundary, and is reported in the following articles:

Developing a cement-based method to stabilize sand in experimental tests

River and Estuarine Morphodynamics Lab., Queen's University, Kingston, Canada

Flow patterns, bank erosion, and planimetric changes in meandering streams: an experimental study

River and Estuarine Morphodynamics Lab., Queen's University, Kingston, Canada

This project, which was carried out under wonderful supervision of Professor Ana Maria da Silva, was a laboratory modeling of flow, bank erosion and planimetric changes in meandering streams. It aimed at 1) studying flow patterns in meandering streams; 2) evaluating existing equations for estimating bank erosion; and 3) providing insight into the planimetric fate of the meandering rivers. This included the following:

  • Laboratory experiments of flow patterns, bank erosion and planform evolution of meandering streams
  • Measurement of flow velocities using ADV's
  • Surveying morphological changes using conventional techniques and laser scanning
  • Data analysis and visualization

Based on the results, following papers were published

Several other articles are in preparation and submission stage.