Turbulent flow and mixing in hyporheic zone

This project aims at investigating solute transport and mixing in the interface between the aquifer and the stream where the flow exchange and mixing between the surface water and groundwater occur. This region provides a significant contribution to the attenuation of pollutants and the self-purification of the river water. Diffusion and mixing are challenging to predict within this critical area and requires investigation of the solute transport and mixing ina porous medium under turbulent flow conditions. A numerical model has been developed meant to capture the mentioned phenomena. The study is grounded on the use of the random walking technique and an appropriate Lagrangian mixing model. The first one, consisting of the discretization of the solute in particles, is employed to track the motion of solute particles due to diffusion processes. The second one enables the prediction of the temporal evolution of chemical concentration in the hyporheic zone, as well as the mixing of the solute mass within the porous domain.

Pore-network of non-linear flow and solute transport

Pore network models have been developed for understanding the effects of the single pore processes on non-Darcy flow behaviour and associated solute transport processes. The impact of the micro-scale heterogeneity of porous media on the inertial flow and transition boundary between flow regimes have not been investigated. Transport characteristics of the randomly structured porous media and the influence of inertial force on longitudinal and transverse dispersion coefficients were studied.

Experimental system, visualization, and measurements

Understanding pore-scale processes in geomaterials requires study of various dynamic processes inside the pore space of geomaterials. Advanced non-destructive and fast imaging strategies using optical microscopy (confocal microscopy), X-ray computed tomography and image analysis are developed and used for real-time imaging of processes in the pore space. Image processing is used to simulate geometrical and topological characteristics of porous materials and calculate the probability density function of processes state variables.