~ FREE ZOOM WEBINAR ~
IAHR Webinar on Numerical Simulation and Field Insights on Mixing Processes in Rivers and Coastal Environments

September 23, 2025, Tuesday

9am New York | 1pm UTC | 3pm Madrid | 6:30pm New Delhi | 9pm Beijing

Ensuring water quality and safeguarding aquatic ecosystems require accurate knowledge of how fluids with different properties mix in rivers and coastal environments. In an era of increasing environmental pressures – from urbanization to climate change – understanding and predicting mixing processes is more important than ever.

The IAHR/IWA joint committee on outfall systems is organizing on September 23, 2025 a webinar on Numerical Simulation and Field Insights on Mixing Processes in Rivers and Coastal Environments. This technical webinar brings together two case studies that showcase the latest advances in numerical modeling and field-based research, offering participants an opportunity to exchange experiences, discuss innovative methods, and explore how advanced modeling and monitoring can support better water quality management worldwide.

The first presentation demonstrates how OpenFOAM source codes can be applied to simulate gravity currents generated by the dense effluent from desalination plants. By avoiding conventional simplifying assumptions and fully resolving density variations, this approach provides a powerful tool to assess environmental impacts and guide more effective outfall design.

The second presentation examines mixing in meandering rivers, focusing on the North Saskatchewan River in Canada. By integrating numerical modeling with detailed field observations, the study provides valuable insights into how wastewater, industrial discharges, and agricultural runoff disperse and influence river water quality.

Speakers

Chair

Program

• Introduction to this webinar and the speak  (5 mins)
  Majid Mohammadian | Past Chair, IAHR/IWA Joint Committee on Outfall Systems; Professor, Department of Civil Engineering at the University of Ottawa, Canada

• Simulation of Density Currents using the OpenFOAM Source Codes  (25mins + 5mins Q&A)
  Sana Ramezani | Ph.D. candidate in Civil Engineering at McGill University in Montreal, Quebec, Canada

• Mixing in Meandering rivers; case study: mixing in the North Saskatchewan River  (25mins + 5mins Q&A)
  Vahid Pilechi | Water Resources Team Lead, the National Research Council Canada (NRC) Ocean, Coastal, and River Engineering (OCRE) research center

Abstracts of the Presentations

Simulation of Density Currents using the OpenFOAM Source Codes (by Sana Ramezani): Marine disposal from desalination plants involves a density current of very high salinity concentrate, typically in the range of 52 ppt to 70 ppt, which is 1.5 to 2 times the salinity of ambient seawater (33-35 ppt). Understanding the mixing of the current with its ambient is essential to assessing environmental impacts and supporting effective hydraulic design. This presentation is about numerical simulations of gravity currents using the OpenFOAM source codes. Unlike many conventional approaches, the OpenFOAM simulations are multi-processor efficient and can be conducted without making the Boussinesq approximation, allowing full resolution of density variations. The method can provide an accurate determination of the mixing and dilution of desalination effluent with the surrounding coastal water.

Mixing in Meandering rivers; case study: mixing in the North Saskatchewan River (by Vahid Pilechi): Water quality in the North Saskatchewan River has been identified as a key issue in the North Saskatchewan Regional Plan. Inputs from wastewater outfalls, industrial discharges, and agricultural runoff make it essential to understand how contaminants mix in the river. Such knowledge is critical for developing and calibrating accurate water quality models, which guide the permissible duration and magnitude of discharges. This presentation highlights a comprehensive study combining numerical modeling with in-situ field measurements. The case study of the North Saskatchewan River provides new insights into mixing processes in meandering rivers, supporting improved water quality management and environmental decision-making.

About the Speakers and Session Chair

Dr. Sana Ramezani is a Ph.D. candidate in Civil Engineering at McGill University in Montreal, Quebec, Canada. Her research focuses on numerical modelling of gravity-driven flows, including dam-break releases, impact forces on offshore structures, and simulations of non-Boussinesq density current using OpenFOAM source codes. She also has several years of professional experience as a hydraulic engineer, where she contributed to the design of water transmission systems and wastewater treatment plants.

Dr. Vahid Pilechi is the Water Resources Team Lead at the National Research Council Canada (NRC) Ocean, Coastal, and River Engineering (OCRE) research center. He is also an adjunct professor at the University of Ottawa. He holds a PhD in Water Resources Engineering from the University of Ottawa, an MSc in Marine Structures from the University of Tehran, and a BSc in Civil Engineering from Iran University of Science and Technology. Dr. Pilechi specializes in the development and application of advanced numerical methods for modeling complex coastal and riverine processes and addressing water quality challenges. In 2019, he initiated NRC’s microplastic research project, aiming to enhance our understanding of the environmental impact of microplastics in aquatic ecosystems. He now leads a multidisciplinary initiative that brings together multiple NRC research centers and collaborators from government, academia, and industry.

Dr. Majid Mohammadian is a Professor (2018) at the Department of Civil Engineering at the University of Ottawa (Canada) working on analyzing environmental problems. He is a professional Civil Engineer (P.Eng.). He obtained his Ph.D. degree from Laval University in the field of applied mathematics and has research experience at M.I.T. with a focus on the numerical simulation of hydrodynamic systems such as shallow water flows. His area of research includes numerical simulation of water bodies, and experimental and numerical modeling of marine outfall systems. He uses laser-induced fluorescence and particle image velocimetry for laboratory studies and OpenFOAM for numerical simulations. He is the former chair of the IAHR-IWA Joint Committee on Marine Outfall Systems.

More Information

• How to participate: This webinar will be held via ZOOM Webinar, please click here to register and get the Zoom Webinar link.

• More about the IAHR/IWA Joint Committee on Marine Outfall Systems

Related Events