Numerical and experimental hydrodynamic studies of a lagoon pilot

Area of Science:

• Environmental Engineering
• Fluid Dynamics
• Computational Modeling

Background:

• Residence time distribution (RTD) is critical for characterizing, designing, and modeling environmental engineering processes, particularly in wastewater and waste treatment.
• Homogeneous fluid distribution is essential for optimal process performance, and understanding RTD helps identify and mitigate issues like short-circuiting and dead zones.

Purpose of the Study:

• To present and compare two numerical methods for predicting theoretical residence time distributions using the finite volume method.
• To validate these numerical methods by comparing predictions with experimental measurements of mean residence times in a lagoon.

Main Methods:

• Solving a transport equation for the local mean age of the fluid to obtain a spatial distribution of fluid age.
• Simulating a virtual particle stream (tracer) in a Lagrangian reference frame to generate an exit time distribution histogram.

Main Results:

• Both methods provide theoretical predictions of residence time distributions.
• The study validates the relevance of these numerical methods through comparison with experimental data from a lagoon.
• The methods allow for the instantaneous determination of geometrical flow characteristics influencing residence time dispersion.

Conclusions:

• The presented numerical methods offer valuable tools for predicting residence time distributions in environmental engineering processes.
• Accurate RTD prediction can significantly improve the design of water and waste treatment facilities, preventing undesirable flow patterns.
• These methods contribute to the development of more efficient and effective environmental engineering solutions.