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The initiation and propagation of wormhole near the wellbore during the process of water injection was investigated through finite element simulations. To describe the problem, a multi-physics coupling model, in which hydrodynamics, geomechanics and erosion were coupled, was built. By constructing a reservoir model with stochastic and inhomogeneous porosity this study found that the initial porosity plays an important role in the geometry and evolution direction of wormhole. The effects on the erosion rate and wormhole area under the consideration of parameters such as flow flux, erosion coefficient and pore pressure were elucidated. Furthermore, wellbore with multi-perforations was studied to investigate possible interactions between the perforations due to Darcy flow. The simulation results show that the wormhole is more likely to form around the longer perforations. With the increase of the angle between two perforations, the wormhole around the cusp of perforations is more likely to form while the wormhole around the wellbore is restrained. This work provides an insight to guide the design of perforation pattern and application of injection in terms of optimization of the hydrocarbon production. [ABSTRACT FROM AUTHOR]

Co‐free O3‐type NaNi0.5Mn0.5O2 cathode material for sodium‐ion batteries has shown great promise due to its high theoretical capacity and plentiful Na reservoir. However, the rapid capacity recession caused by harmful phase transition and large volume strain severely restricts their practical application. Herein, the obstacle is well addressed by constructing a P2&O3 biphasic structure via a customized boron‐doping strategy. The light‐weight boron doping in the interstitial position reduces the energy gap of the formation energy of P2 and O3 structure, which induces the formation of P2&O3 biphase in high Na state. In addition, the biphasic structure exhibits near zero volume strain due to the lattice interlocking effect of P2&O3, as identified by in situ X‐ray diffraction measurement. As a result, it presents a remarkable cyclability with a capacity retention of 85.2% over 1000 cycles at a high rate of 5 C. More importantly, a pouch‐type full‐cell device can exhibit a long cycling life with 70.8% capacity retention over 150 cycles at 0.1 C. This work can offer a new inspiration for designing advanced high sodium electrode materials via light element doping for future energy storage devices. [ABSTRACT FROM AUTHOR]

The effect of interlayer shear on bending property of multi-layer graphene is investigated using molecular dynamics simulations. Interlayer shear modulus is three orders lower than in-plane Young's modulus, thus the bending behavior is dominated by interlayer shear. Continuum theory and atomistic simulations show that bending rigidity is proportional to layer number when the layer number exceeds 5. The small difference of these two proportional constants results from the stacking pattern, and turbostratic stacking decreases the interlayer shear modulus. For layer number smaller than 4, intrinsic ripples also play an important role and further decrease the interlayer shear modulus. [ABSTRACT FROM AUTHOR]