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Ali Zafarani Subsurface Processes Group University of California, Irvine.

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Presentation on theme: "Ali Zafarani Subsurface Processes Group University of California, Irvine."— Presentation transcript:

1 Ali Zafarani Subsurface Processes Group University of California, Irvine

2  Groundwater is one of the main resources to provide water consumption needs  Sources of pollution: Chemicals (detergents, petroleum, etc.), Radionuclides, Seawater, Pathogens  Understanding the transport mechanisms of contaminants  Designing infrastructures and hydrogeologic systems  Designing remediation systems  Estimate of damage

3  Provide pathways for fluid flow  Large scale fracture networks  Reservoirs formed in fractured rocks  Fractures appear in many kinds of geological systems

4  Advection  Transport of particle with the flow field  Dispersion (Effective Longitudinal Dispersion)  Molecular Diffusion  Taylor dispersion  Macro scale dispersion

5  3-D Navier-Stokes Equation  3-D Stokes Equation  2-D Reynolds Equation Inertial<< viscous and pressure Changes in fracture aperture are smooth Normal velocity to fracture walls are negligible 3-D  2-D Inertial forces Viscous forces Pressure term Momentum Eq. Mass Conservation

6  Fick’s first law of Diffusion  diffusive flux ~ spatial concentration gradient  Fick’s second law of Diffusion  Changes of concentration field with time Diffusion Coefficient [L 2 /T]

7  Parabolic distribution of velocity in aperture  ~ square mean velocity  ~ Mean aperture size b V

8  Dispersion caused by variety of pathways

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10 CCD Camera Porous media cell Rotating stand Uniform light source Textured glass plates provide analog to fracture surfaces. Rotating test stand holding test cells and equipped with a high resolution 12-bit CCD camera (2048 x 3072 pixels) Fracture plate 3/4” flat glass No flow boundary Inlet manifold Aluminum frame Reference wedge Clear PVC gasket Confinement pressure inlet

11  Measured light intensities are used to accurately quantify:  Fracture aperture  Solute concentrations at high resolutions over entire flow field.  Measurements can be used to calculate Solute dispersion Aperture (cm) Entrapped nonaqueous phase 3 cm

12  Constant fracture aperture (smooth walls)  Macro-scale dispersion is zero  Taylor dispersion results the plume to be stretched in flow direction (D L,Taylor )

13 Aperture mm 10 cm Experimental Simulation  Variable aperture field is measured by image system  Finger shaped forefront of solute plume shows the Macro-Dispersion

14  Simulation and Experimental results match for Hele-Shaw cell  Simulations underestimate dispersion in Rough- Walled cell  Reynolds equation underestimates variations in velocity field

15  Network fracture simulation  Scale dependent dispersion coefficients

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