Modeling and Numerical Analysis of the Solid Particle Erosion in Curved Ducts

This paper presents a modeling and computational study on particle erosion in curved ducts. It is found that the average erosion rates per impact range from to  mm3/g under current conditions. For each doubled inlet velocity, the increases of erosion rates per impact are 2–14 times. The erosion rate per impact varies with particle diameter with “√” shape through bends, which is similar to the particle deposition behavior in duct flows. The erosion rate curves per injected particle show the shapes of a 90-degree anticlockwise rotated “S” and a wide open “V,” respectively, for three larger and smaller inlet velocities. The average erosion rates per injected particle are 1.4–18.9 times those rates per impact due to huge amounts of impacting, especially for those depositing particles. It is obvious that the erosion rate distribution per impact is similar to a “fingerprint” with five clear stripes and a lower “cloud” along the bend deflection angle for the three largest particles; yet, for other smaller particles, the erosion rate distributions are much like an entire “cloud.

Yielding and hardening of flexible fiber packings during triaxial compression

This paper examines the mechanical response of flexible fiber packings subject to triaxial compression. Short fibers yield in a manner similar to typical granular materials in which the deviatoric stress remains nearly constant with increasing strain after reaching a peak value. Interestingly, long fibers exhibit a hardening behavior, where the stress increases rapidly with increasing strain at large strains and the packing density continuously increases. Phase diagrams for classifying the bulk mechanical response as yielding, hardening, or a transition regime are generated as a function of the fiber aspect ratio, fiber-fiber friction coefficient, and confining pressure. Large fiber aspect ratio, large fiber-fiber friction coefficient, and large confining pressure promote hardening behavior. The hardening packings can support much larger loads than the yielding packings contributing to the stability and consolidation of the granular structure, but larger internal axial forces occur within fibers.Comment: 14 pages, 4 figure

Molecular dynamics simulation of flow around a circular nano-cylinder

In this study, the wake flow around a circular nano-cylinder is numerically investigated with molecular dynamics simulation to reveal the micro/nano size effect on the wake flow. The cavitation occurring when Reynolds number (Re) > 101 can effectively influence the wake flow. The Strouhal number (St) of the wake flow increases with the Re at low Re, but steadily decreases with the Re after the cavitation appears. The dominant frequency of the lift force fluctuation can be higher than that of the velocity fluctuation, and be drowned in the chaotic fluctuating background of the Brownian forces when Re {\geq} 127. Also because of the strong influence of the Brownian forces, no dominant frequency of the drag force fluctuation can be observed. The Jz number, which is defined as the ratio between the mean free path {\lambda} of the fluid molecules and the equilibrium distance of potential energy {\sigma}, is newly introduced in order to consider the internal size effect of fluid. The St of the wake flow increases with the Jz until it falls to zero sharply when Jz {\approx} 1.7. It denotes the discontinuity of the fluid can eventually eliminate the vortex generation and shedding. Meanwhile, the St decreases with the Kn because of the intensification of the cavitation.Comment: 17 pages, 17 figures, 37 conference

Discrete Element Method Model of Elastic Fiber Uniaxial Compression

A flexible fiber model based on the discrete element method (DEM) is presented and validated for the simulation of uniaxial compression of flexible fibers in a cylindrical container. It is found that the contact force models in the DEM simulations have a significant impact on compressive forces exerted on the fiber bed. Only when the geometry-dependent normal contact force model and the static friction model are employed, the simulation results are in good agreement with experimental results. Systematic simulation studies show that the compressive force initially increases and eventually saturates with an increase in the fiber-fiber friction coefficient, and the fiber-fiber contact forces follow a similar trend. The compressive force and lateral shear-to-normal stress ratio increase linearly with increasing fiber-wall friction coefficient. In uniaxial compression of frictional fibers, more static friction contacts occur than dynamic friction contacts with static friction becoming more predominant as the fiber-fiber friction coefficient increases.Comment: 30 pages, 14 figures, submitted for publicatio

Opening Knowledge Graph Model Building of Artificial Intelligence Curriculum

The knowledge points setting of artificial intelligence curriculum has shortcomings in connection between theory and practices. To overcome the problem, this study designs an open knowledge point design model based on knowledge graph. Fist, to promote the construction of the knowledge graph (KG) of curriculums, associated teaching research was analyzed visually. Then the order and hierarchical structure of the knowledge points were defined, and the ontology structure of curriculum knowledge and the relationship between knowledge points and posts were designed as well. Moreover, an overall logic structure for the construction of the open KG of curriculums was proposed. Results demonstrated that high attention should be paid to the construction and concern of teaching teams for artificial intelligence algorithms and the KG of curriculum construction. Additionally, the opening model can strengthen the openness of the KG of curriculums to reinforce the close connections between classroom knowledge and practices. Research conclusions are conducive to understand the existing problems in the KG of curriculums and provide beneficial references to the integration of information technology and education

Opening Knowledge Graph Model Building of Artificial Intelligence Curriculum

The knowledge points setting of artificial intelligence curriculum has shortcomings in connection between theory and practices. To overcome the problem, this study designs an open knowledge point design model based on knowledge graph. Fist, to promote the construction of the knowledge graph (KG) of curriculums, associated teaching research was analyzed visually. Then the order and hierarchical structure of the knowledge points were defined, and the ontology structure of curriculum knowledge and the relationship between knowledge points and posts were designed as well. Moreover, an overall logic structure for the construction of the open KG of curriculums was proposed. Results demonstrated that high attention should be paid to the construction and concern of teaching teams for artificial intelligence algorithms and the KG of curriculum construction. Additionally, the opening model can strengthen the openness of the KG of curriculums to reinforce the close connections between classroom knowledge and practices. Research conclusions are conducive to understand the existing problems in the KG of curriculums and provide beneficial references to the integration of information technology and education

A new analytical solution for solving the Smoluchowski equation due to nanoparticle Brownian coagulation for non-self-preserving system

The Smoluchowski equation has become a fundamental equation in nanoparticle processes since it was proposed in 1917, whereas the achievement of its analytical solution remains a challenging issue. In this work, a new analytical solution, which is absolutely different from the conventional asymptotic solutions, is first proposed and verified for non-self-preserving nanoparticle systems in the free molecular regime. The Smoluchowski equation is first converted to the form of moment ordinary differential equations by the performance of Taylor expansion method of moments and subsequently resolved by the separate variable technique. In the derivative, a novel variable, g = m0m2/m12, where m0, m1 and m2 are the first three moments, is first revealed which can be treated as constant. Three specific models are proposed, two with a constant g (an Analytical Model with Constant g (AMC), and a Modified Analytical Model with Constant g (MAMC)), and another with varying g(a finite Analytical Model with Varying g (AMV)). The AMC model yields significant errors, while its modified version, i.e., the MAMC model, is able to produce highly reliable results. The AMV is verified to have the capability to solve the Smoluchowski equation with the same precision as the numerical method, but an iterative procedure has to be employed in the calculation.</p