Plume Spreading Research

Groundwater is an essential natural resource, but vulnerable to contamination, so we spend billions of dollars annually on groundwater remediation. One approach to groundwater remediation is to inject a treatment solution to destroy contaminants in place; this is called in-situ remediation. In-situ remediation often requires spreading an injected plume of treatment solution into the contaminated groundwater, but the laminar flows characteristic of porous media prevent the turbulence that generates plume spreading in most engineered reactors. The resulting difficulty in spreading is a widely recognized, fundamental problem in groundwater remediation.

The research described here, in collaboration with Roseanna Neupauer from the University of Colorado Boulder, approaches this fundamental problem starting with a simple idea from chaos theory: When turbulent mixing is not possible, the best way to spread one fluid into another is by chaotic advection. The essence of chaotic advection is actually quite simple: One needs to impose plume stretching and folding as shown in the animations below. This work, with many other collaborators and students, has established the subfield of engineered injection and extraction.

Along the way, beyond chaotic advection, we have learned how to optimize plume spreading for sorbing solutes, demonstrated reversible hydrodynamic dispersion, and mitigated the notorious wall effect in porous media experiments.

Animations

These animations illustrate chaotic advection by engineered injection and extraction (Mays and Neupauer 2012).

• Mays-Neupauer-Stretching-Folding.wmv, four cycles of the 12-step pumping sequence.
• Mays-Neupauer-Periodic-Points.wmv, same as above, but shown with the four period one points and an unstable manifold.

Publications

• Injecting heated water generates longer plume interfaces (Tigera et al. 2023).
  
• Experiments and simulations demonstrate engineered injection and extraction (Sather and Roth et al. 2023).
  
• Engineered injection and extraction provides hydraulic building blocks for groundwater remediation (Sather et al. 2022).
• Experimental evidence that hydrodynamic dispersion can be reversible (Neupauer et al. 2021).
• Laser-induced fluorescence imaging in refractive index-matched porous media (Roth et al. 2021).
• Injection and extraction drives mixing at multiple scales (Neupauer et al. 2020).
• Wall effect mitigation techniques for experiments with planar walls (Roth et al. 2020).
• Simulations and experiments lay the foundation for future field testing (Mays and Neupauer 2017).
• Pumping schemes for sorbing contaminants are optimized separately (Piscopo et al. 2016).
• Pumping schemes can be optimized with multi-objective evolutionary algorithms (Piscopo et al. 2015).
• Sorbing contaminants require different engineered injection and extraction (Neupauer and Mays 2015).
• Aquifer heterogeneity increases spreading and changes nature of chaotic advection (Neupauer et al. 2014).
• Simulations indicate that chaotic advection accelerates contaminant degradation (Piscopo et al. 2013).
• Discussion of practical and regulatory benefits of avoiding re-injection (Mays and Neupauer 2013).
• Theoretical demonstration of chaotic advection by stretching and folding (Mays and Neupauer 2012).

updated 4/28/2023