An experimental study on the influences of wind erosion on water erosion

In semi-arid regions, complex erosion resulted from a combination of wind and water actions has led to a massive soil loss and a comprehensive understanding of its mechanism is the first step toward prevention of the erosion. However, the mutual influences between wind erosion and water erosion have not been fully understood. This research used a wind tunnel and two rainfall simulators and simulated two rounds of alternations between wind erosion and water erosion（i.e., 1^（st） wind erosion–1^（st） water erosion and 2^（nd） wind erosion–2^（nd） water erosion） on three slopes（5°, 10°, and 15°） with six wind speeds（0, 9, 11, 13, 15, and 20 m/s） and five rainfall intensities（0, 30, 45, 60, and 75 mm/h）. The objective was to analyze the influences of wind erosion on succeeding water erosion. Results showed that the effects of wind erosion on water erosion were not the same in the two rounds of tests. In the 1^（st） round of tests, wind erosion first restrained and then intensified water erosion mostly because the blocking effect of wind-sculpted micro-topography on surface flow was weakened with the increase in slope. In the 2^（nd） round of tests, wind erosion intensified water erosion on beds with no rills at gentle slopes and low rainfall intensities or with large-size rills at steep slopes and high rainfall intensities. Wind erosion restrained water erosion on beds with small rills at moderate slopes and moderate rainfall intensities. The effects were mainly related to the fine grain layer, rills and slope of the original bed in the 2^（nd） round of tests. The findings can deepen our understanding of complex erosion resulted from a combination of wind and water actions and provide scientific references to regional soil and water conservation.

Limits on rough-particle sizing with low-defocus interferometric imaging

We present a rigorous theoretical model for the influence of the aperture in interferometric out-of-focus imaging. We investigate the role of this effect on the properties of speckle-like patterns generated by irregular, rough particles. Finally, we determine the conditions under which these patterns are no longer representative of particle size but of the aperture itself and the defocus parameter.

Structural Evolution in Flowing Immiscible Blends in the Presence of Rough Particles:Dependence of Shear Rate and Blend Ratio

The influence of polystyrene particles with different nanoscale roughnesses on the morphology of polyisobutylene/poly-dimethylsiloxane blends was studied under shear flow by using confocal laser scanning microscopy.It was found that the surface roughness of particles strongly affected their diffusion and distribution behaviors,thereby determining the size and spatial arrangement of droplets in the blends.The roughness effect of particles was found to possess a strong dependence on both the blend ratio and the shear rate.The result suggested that the particle roughness can serve as a new parameter to control the structure-property correlation in particle-filled polymer blends,especially under slow flow.

Two-fluid modelling for cylindrical fluidized beds using kinetic theory for rough spheres

Recently,we have extended the kinetic theory of granular flow (KTGF) to include friction between the spherical particles and tested it in rectangular geometries.In this study,the extended KTGF implemented in cylindrical coordinates is used to model the more-commonly employed cylindrical bubbling fluidized beds.Special attention is paid to the anti-symmetric part of the velocity gradient in the solids stress tensor.For verification of the implementation,a comparison of the present model in the limit of zero friction with the original (frictionless) KTGF model was made.Subsequently,simulations of bubbling fluidized beds of inelastic particles were performed using our extended KTGF and an effective KTGF model for inelastic particles of Jenkins and Zhang.The simulation results show good agreement for the time-averaged solids volume fraction distribution and solids circulation patterns.Finally,our model is validated by predicting the individual bubble behavior in dense bubbling fluidized beds containing different granular materials in a comparison with experimental data from Verma et al.(2014).The extended KTGF leads to an improved agreement with experimental bubble data.Compared to previous work (Yang et al.,2016b,2017c),and by introducing cylindrical coordinates,the current work demonstrates that the extended KTGF improves predictions for the temporal bubble behavior of cylindrical fluidized beds.