Research Interests
My research centres on mathematical and computational modelling of subsurface solute transport, and in particular on how this is impacted by unresolved heterogeneity. The subsurface is an information-poor environment, and solute transport behaviour may be affected by heterogeneity at scales too small to measure and/or model on a computer. Naturally, this confounds one of the goals of hydrogeologists: making predictions. With this motivation, I seek to develop closure models to average away unresolved heterogeneity, to calibrate predictive models using macroscopic observables, and to develop error envelopes for hydrogeological predictions. Related to these overarching themes, specific areas of interest include transport behavior of reacting solutes in heterogeneous flow fields, analysis of the effect of model (as opposed to measurement) error on predictive accuracy, stochastic (especially random walk) methods, multiphase systems, and scientific computing.

Current scientific computing efforts include (i) development of the Aurora package, which allows for the anomalous transport modelling approaches developed in the academic world to be used in concert with the complex, large-scale MODFLOW models employed by practitioners, (ii) development GPU-based particle tracking codes using CUDA, and (iii) development of adjoint state code in FEniCS for exploration of error envelopes.

Publications
Publications in refereed scientific journals since 2013:
S.K. Hansen, C.P. Haslauer, O.A. Cirpka and V.V. Vesselinov (2018). Direct breakthrough curve prediction from statistics of heterogeneous conductivity fields. Water Resources Research 54(1), 271-285
S.K. Hansen, J. He and V.V. Vesselinov (2018). Characterizing the impact of model error in geophysical time series recovery inverse problems. Advances in Water Resources 111, 372-380.
S.K. Hansen, and V.V. Vesselinov (2018). Local Equilibrium and Retardation Revisited. Groundwater 56(1), 109-117.
S.K. Hansen, S. Pandey, S. Karra and V.V. Vesselinov (2017). CHROTRAN v1.0: a mathematical and computational model for in situ heavy metal remediation in heterogeneous aquifers. Geoscientific Model Development 10, 4525-4538.
S.K. Hansen, V.V. Vesselinov, Z. Lu, P.W. Reimus (2017). Inferring subsurface heterogeneity from push-drift tracer tests. Water Resources Research 53(7).
D.K. Burnell, S.K. Hansen and J. Xu (2017). Transient modeling of non-Fickian transport and first-order reaction. Advances in Water Resources 107, 370-392.
S.K. Hansen, B. Berkowitz, V.V. Vesselinov, D. O'Malley and S. Karra (2016). Push-pull tracer tests: their information content and use for characterizing non-Fickian, mobile-immobile behavior. Water Resources Research 52(12), 9565-9585.
S.K. Hansen and V.V. Vesselinov (2016). Contaminant point source localization error estimates as functions of data quantity and model quality. Journal of Contaminant Hydrology 193, 74-85.
B. Berkowitz, I. Dror, S.K. Hansen, and H. Scher (2016). Measurements and models of reactive transport in geological media. Reviews of Geophysics 54(4), pp. 930-986.
S.K. Hansen (2015). Effective ADE models for first-order mobile-immobile solute transport: limits on validity and modeling implications. Advances in Water Resources 86 Part A, pp. 184–192.
S.K. Hansen and B. Berkowitz (2015). Integrodifferential formulations of the continuous-time random walk for solute transport subject to bimolecular A + B → 0 reactions. Physical Review E 91, 032113.
S.K. Hansen and B. Berkowitz (2014). Interpretation and nonuniqueness of CTRW transition distributions: insights from an alternative solute transport formulation. Advances in Water Resources 74, pp. 54–63.
S.K. Hansen, H. Scher and B. Berkowitz (2014). First-principles derivation of reactive transport modeling parameters for particle tracking and PDE approaches. Advances in Water Resources 69, pp.146–158.
S.K. Hansen and B.H. Kueper (2014). A new model for coupled multicomponent NAPL dissolution and aqueous-phase transport, with application to creosote dissolution in discrete fractures. Water Resources Research 50, pp. 58–70.
S.K. Hansen (2013). Semianalytic solution for transport of a two-member decay chain in discrete parallel fractures. Water Resources Research 49, pp. 6105–6110.

B.Sc. 2004 Queen’s University, Canada, Mathematics and Engineering. First class honours.

M.Sc. 2007 University of Toronto, Canada, Department of Mathematics.

Ph.D. 2012 Queen’s University, Canada, Department of Civil Engineering.