@article{fazelpour_daniels_2023, title={Controlling rheology via boundary conditions in dense granular flows}, ISSN={1744-6848}, url={https://doi.org/10.1039/D2SM00683A}, DOI={10.1039/d2sm00683a}, abstractNote={Boundary shape, particularly roughness, strongly controls the amount of wall slip and internal pressure in dense granular flows.}, journal={SOFT MATTER}, author={Fazelpour, Farnaz and Daniels, Karen E.}, year={2023}, month={Feb} }
 @article{desai_fazelpour_handwerger_daniels_2023, title={Forecasting landslides using community detection on geophysical satellite data}, volume={108}, ISSN={2470-0045 2470-0053}, url={http://dx.doi.org/10.1103/PhysRevE.108.014901}, DOI={10.1103/PhysRevE.108.014901}, abstractNote={As a result of extreme weather conditions, such as heavy precipitation, natural hillslopes can fail dramatically; these slope failures can occur on a dry day, due to time lags between rainfall and pore-water pressure change at depth, or even after days to years of slow motion. While the prefailure deformation is sometimes apparent in retrospect, it remains challenging to predict the sudden transition from gradual deformation (creep) to runaway failure. We use a network science method-multilayer modularity optimization-to investigate the spatiotemporal patterns of deformation in a region near the 2017 Mud Creek, California landslide. We transform satellite radar data from the study site into a spatially embedded network in which the nodes are patches of ground and the edges connect the nearest neighbors, with a series of layers representing consecutive transits of the satellite. Each edge is weighted by the product of the local slope (susceptibility to failure) measured from a digital elevation model and ground surface deformation (current rheological state) from interferometric synthetic aperture radar (InSAR). We use multilayer modularity optimization to identify strongly connected clusters of nodes (communities) and are able to identify both the location of Mud Creek and nearby creeping landslides which have not yet failed. We develop a metric, i.e., community persistence, to quantify patterns of ground deformation leading up to failure, and find that this metric increased from a baseline value in the weeks leading up to Mud Creek's failure. These methods hold promise as a technique for highlighting regions at risk of catastrophic failure.}, number={1}, journal={Physical Review E}, publisher={American Physical Society (APS)}, author={Desai, Vrinda D. and Fazelpour, Farnaz and Handwerger, Alexander L. and Daniels, Karen E.}, year={2023}, month={Jul} }
 @article{amini_tuohey_long_zhang_morton_daniels_fazelpour_hapgood_2022, title={Photoelastic stress response of complex 3D-printed particle shapes}, volume={409}, ISSN={1873-328X}, url={https://doi.org/10.1016/j.powtec.2022.117852}, DOI={10.1016/j.powtec.2022.117852}, abstractNote={Stress visualization within 3-dimensional particles could provide significant insights for understanding of the behaviors of complex particles. However traditional photoelastic methods are only able to produce simple particle shapes. Recently, 3D-printing has created new possibilities for enhancing the scope of stress analysis of physically representative particles. We report the results of X-ray computed tomography and 3D-printing, combined with traditional photoelastic analysis, to visualize strain for particles ranging from simple 2D discs to complex 3D-printed coffee beans, including internal voids. The relative orientation of the print layers and the loading force can affect the optical response of the discs without affecting the mechanical properties. Furthermore, a semi-quantitative measurement of the generated stresses within 3D-printed complex particle is presented. Potential limitations and areas of future interest for stress visualization of 3-dimensional particles are also outlined. • 3D printing photoelastic UV-curable resin enables stress analysis of complex particles. • Ray tracing confirms shadow at multiple faces of complex particles is from refraction. • Print orientation affects optical properties of 3D printed discs with applied load. • Semi-quantitative stress measurement can be obtained from complex 3D printed particles.}, journal={POWDER TECHNOLOGY}, author={Amini, Negin and Tuohey, Josh and Long, John M. and Zhang, Jun and Morton, David A. and Daniels, Karen E. and Fazelpour, Farnaz and Hapgood, Karen P.}, year={2022}, month={Sep} }
 @article{fazelpour_tang_daniels_2022, title={The effect of grain shape and material on the nonlocal rheology of dense granular flows}, volume={1}, ISSN={["1744-6848"]}, url={https://doi.org/10.1039/D1SM01237A}, DOI={10.1039/d1sm01237a}, abstractNote={Nonlocal rheologies allow for the modeling of granular flows from the creeping to intermediate flow regimes, using a small number of parameters. In this paper, we report on experiments testing how particle properties affect the model parameters used in the Kamrin & Koval cooperative nonlocal model, using particles of three different shapes (circles, ellipses, and pentagons) and three different materials, including one which allows for the measurement of stresses via photoelasticity. Our experiments are performed on a quasi-2D annular shear cell with a rotating inner wall and a fixed outer wall. Each type of particle is found to exhibit flows which are well-fit by nonlocal rheology, with each particle having a distinct triad of the local, nonlocal, and frictional parameters. While the local parameter b is always approximately unity, the nonlocal parameter A depends sensitively on both the particle shape and material. The critical stress ratio μs, above which Coulomb failure occurs, varies for particles with the same material but different shape, indicating that geometric friction can dominate over material friction.}, journal={Soft Matter}, author={Fazelpour, Farnaz and Tang, Zhu and Daniels, Karen E.}, year={2022}, month={Jan} }