CFD-DEM analysis of hydraulic conveying bends: Interaction between pipe orientation and flow regime

• Published in: Powder technology 2021-11, Vol.392, p.619-631
• Main Authors: Zhou, Mengmeng, Kuang, Shibo, Xiao, Fei, Luo, Kun, Yu, Aibing
• Format: Article
• Language: English
• Subjects: Bend; Bends; CFD-DEM; Computational fluid dynamics; Computer applications; Conveying; Discrete element method; Elevation; Erosion rates; Flow; Fluid dynamics; Hydraulic conveying; Hydraulics; Hydrodynamics; Low pressure; Mathematical models; Pipes; Pressure; Pressure drop; Pressure loss; Stability analysis; Wear
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2021.07.052

Bends are potentially most problematic in a hydraulic conveying pipeline system. This paper presents a numerical study of hydraulic bends, with special reference to the interaction between pipe orientation and flow regime. This is done by the combined approach of computational fluid dynamics and discrete element method facilitated with a wear model. The validity of the model has been verified by comparing the measured and predicted flow properties and erosion depth. On this basis, three pipe orientations: 0° (i.e. horizontal-vertical bend), 45° (i.e. inclined bend), and 90° (i.e. vertical-horizontal bend) are simulated for the conveying speeds of 1.2 m/s, 2.0 m/s and 4.0 m/s. It covers typical flow regimes in a horizontal pipe. Via the simulation outputs, the bend performance is assessed in terms of pressure loss, conveying instability and bend erosion. The results reveal that the pressure drop and erosion rate differ for various pipe orientations and conveying speeds involving different flow regimes. The acceleration/de-acceleration of the particles exiting the bend does not result in a significant additional pressure. The vertical-horizontal bend has low erosion rates benefiting from cluster formation and low pressure, which is not the case at high conveying speeds. By contrast, the inclined bend gives the highest elevation height and does not suffer significant pressure drop, pressure fluctuation, and erosion rate under all the flow regimes considered. [Display omitted] •Flows and wall erosion of hydraulic bend are studied by the CFD-DEM approach.•Interaction between pipe orientation and conveying speed/flow regime is focused.•Pipe orientation affects flows and bend erosion but mainly at low conveying speeds.•Particle acceleration in a post-bend does not give a large additional pressure loss.•Vertical-horizontal bend has low erosion rates but only at a low conveying speed.