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Accelerating CFD-DEM simulation of dilute pneumatic conveying with bends
Jun Du,Guoming Hu,Ziqiang Fang,Wenjie Gui 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.2
The computational cost is expensive for CFD-DEM simulation, a larger time step and a simplified CFD-DEM model can be used to accelerate the simulation. The relationship between stiffness and overlap in non-linear Hertzian model is examined, and a reasonable time step is determined by a new single particle test. The simplified model is used to simulate dilute pneumatic conveying with different types of bends, and its applicability is verified by compared with the traditional model. They are good agreement in horizontal-vertical case and vertical-horizontal case, and show a significant differences in horizontal-horizontal case. But the key features of particle rope formed in different types of bends can be obtained by both models.
Accelerating CFD-DEM simulation of dilute pneumatic conveying with bends
Du, Jun,Hu, Guoming,Fang, Ziqiang,Gui, Wenjie Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.2
The computational cost is expensive for CFD-DEM simulation, a larger time step and a simplified CFD-DEM model can be used to accelerate the simulation. The relationship between stiffness and overlap in non-linear Hertzian model is examined, and a reasonable time step is determined by a new single particle test. The simplified model is used to simulate dilute pneumatic conveying with different types of bends, and its applicability is verified by compared with the traditional model. They are good agreement in horizontal-vertical case and vertical-horizontal case, and show a significant differences in horizontal-horizontal case. But the key features of particle rope formed in different types of bends can be obtained by both models.
Chao Li,Baihong Li,Guoming Gao,Lijun Zhang,Shu Zhang,Lei Zhang,Jun Xiang,Song Hu,Yi Wang,Xun Hu 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.125 No.-
Drying at 100 C is a common practice for processing many biomasses for their further thermochemicalconversion via the routes such as pyrolysis. The drying temperature of 100 C is low, but might not be toolow to cause any impact on pyrolytic behaviors of a biomass feedstock. In this study, varied scenarios ofthermal pretreatment of poplar sawdust (oven-drying, boiling in water and microwave heating) at 100 Cwere screened for probing their potential influence on the pyrolytic behaviors at 500 and 750 C. Comparing with oven-drying, boiling in water (cooking) and microwave heating at 100 C could removesome oxygen-containing species, increasing carbon content of the pretreated sawdust and promotingcarbonization in pyrolysis. This enhanced formation of biochar, heavy p-conjugated organics in bio-oil,but suppressed generation of gas. The cooking or microwave heating pretreatment also promoted aromatizationto form the biochar of higher thermal stability, higher crystallinity, and higher aromatic degree,due to the enhanced deoxygenation reactions in the pyrolysis. The in-situ IR characterization suggestedthat microwave pretreatment promoted generation of unsaturated ketones and also the species with olefinicC = C, favoring their further aromatization. The cooking pretreatment impacted transformationroutes of the oxygen-containing organics, thus modifying pyrolysis behaviors of the pretreated sawdust.
Learning Multiple-Gait Quadrupedal Locomotion via Hierarchical Reinforcement Learning
Lang Wei,Yunxiang Li,Yunfei Ai,Yuze Wu,Hao Xu,Wei Wang,Guoming Hu 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.9
Over long periods of evolution, legged animals have developed the capability to use a variety of gaits to move efficiently and flexibly at different speeds. To enable quadruped robots to acquire this ability, this study proposes a two-stage training hierarchical framework that can have quadruped robots generate energy-efficient multiple-gait locomotion, consisting of a gait selection policy module and a react controller module. The parameters of both modules are optimized using reinforcement learning. The experimental results in the simulation demonstrate that the proposed method can generate energy-efficient multiple-gait quadrupedal locomotion compared to previous methods. To validate the robustness and effectiveness of the method, we constructed a closed-chain quadruped robot and deployed the controller trained by the method to the robot. The experimental results in the real world suggest that the controller can enable the robot to move stably and efficiently in different gaits. The main contribution of this paper is that the authors propose a novel hierarchical framework, which makes quadruped robots use an optimal gait at a specific speed and smoothly switch to another one after getting a different speed command. These behaviors are automatically produced through simulation training, eliminating the need for the tedious work of designing gaits and modulating controllers. Experimental results showcase that the proposed method has significant advantages compared to previous methods.