Stretching and compression of fluid elements is key for the understanding and quantification mixing and reaction in heterogeneous porous media. We quantify the evolution of the deformation tensor in 2 and 3 dimensional Darcy-scale porous media flows using streamline coordinates. Thus, we derive a stochastic process for the stretching of a material strip in terms of a coupled continuous
time random walk which is parameterized by the statistical medium and flow properties. The derived model is compared to direct numerical simulation of flow, particle motion and Lagrangian deformation. The impact on mixing is studied for the evolution of a diffusive material blob in heterogeneous Darcy scale flow.
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