Performance evaluation of Hydrodynamic Vortex Separator at different hydraulic retention times applied in Recirculating Biofloc Technology system

2017 ◽  
Vol 60 (5) ◽  
pp. 1737-1747 ◽  
Author(s):  
Mingming Shi ◽  
Yunjie Ruan ◽  
Binxin Wu ◽  
Zhangying Ye ◽  
Songming Zhu
Keyword(s):  
Removal Efficiency ◽  
Element Model ◽  
Discrete Element ◽  
Operating Conditions ◽  
Phase Model ◽  
Discrete Element Model ◽  
Discrete Phase Model ◽  
Discrete Phase ◽  
Biofloc Technology ◽  
Vortex Separator

Abstract. Recirculating biofloc technology (RBFT) has been gradually acknowledged for its positive effect on the control of biofloc concentration using a hydrodynamic vortex separator (HDVS). To operate an RBFT system at maximum performance, the removal efficiency of an HDVS at different hydraulic retention times (HRTs) must be fully predictable. Hence, a numerical study of the fluid flow and particle dynamics was performed to characterize the performance of an HDVS at varying HRTs. First, flow simulation was conducted to determine an economical mesh size at an HRT of 248 s. Then, with respect to the total suspended solids (TSS) in the RBFT system and the physical properties of the flocs, two-way coupling of the dense discrete phase model (DDPM) and discrete element model (DEM) methods was used to predict floc tracking in an HDVS. Additionally, the Reynolds averaged Navier-Stokes (RANS) equations with the Reynolds stress turbulence model (RSM) were solved using the finite volume method based on the semi-implicit method pressure-linked equations (SIMPLE) pressure correction algorithm in the computational domain. Finally, pilot-scale studies were conducted to verify the simulation models. Based on the simulation results, floc management in an RBFT system is briefly discussed. Due to limited research on the numerical simulation and operating conditions of an HDVS in an RBFT system, this article describes an original investigation of the modeling approach. Keywords: Computational fluid dynamics, Dense discrete phase model, Discrete element model, Floc management, Flow field, Removal efficiency, Total suspend solids.

scholarly journals Discrete element model for general polyhedra

2021 ◽  
Author(s):  
Alfredo Gay Neto ◽  
Peter Wriggers
Keyword(s):  
Frictional Contact ◽  
Virtual Work ◽  
Particle Surface ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Principle Of Virtual Work ◽  
Dynamics Model ◽  
Railway Ballast ◽  
Multibody Dynamics Model

AbstractWe present a version of the Discrete Element Method considering the particles as rigid polyhedra. The Principle of Virtual Work is employed as basis for a multibody dynamics model. Each particle surface is split into sub-regions, which are tracked for contact with other sub-regions of neighboring particles. Contact interactions are modeled pointwise, considering vertex-face, edge-edge, vertex-edge and vertex-vertex interactions. General polyhedra with triangular faces are considered as particles, permitting multiple pointwise interactions which are automatically detected along the model evolution. We propose a combined interface law composed of a penalty and a barrier approach, to fulfill the contact constraints. Numerical examples demonstrate that the model can handle normal and frictional contact effects in a robust manner. These include simulations of convex and non-convex particles, showing the potential of applicability to materials with complex shaped particles such as sand and railway ballast.

scholarly journals Enhanced discrete phase model for multiphase flow simulation of blood flow with high shear stress

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042110080
Author(s):  
Zheqin Yu ◽  
Jianping Tan ◽  
Shuai Wang
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Multiphase Flow ◽  
Experimental Verification ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Phase Model ◽  
Force Model ◽  
Discrete Phase Model ◽  
Discrete Phase

Shear stress is often present in the blood flow within blood-contacting devices, which is the leading cause of hemolysis. However, the simulation method for blood flow with shear stress is still not perfect, especially the multiphase flow model and experimental verification. In this regard, this study proposes an enhanced discrete phase model for multiphase flow simulation of blood flow with shear stress. This simulation is based on the discrete phase model (DPM). According to the multiphase flow characteristics of blood, a virtual mass force model and a pressure gradient influence model are added to the calculation of cell particle motion. In the experimental verification, nozzle models were designed to simulate the flow with shear stress, varying the degree of shear stress through different nozzle sizes. The microscopic flow was measured by the Particle Image Velocimetry (PIV) experimental method. The comparison of the turbulence models and the verification of the simulation accuracy were carried out based on the experimental results. The result demonstrates that the simulation effect of the SST k- ω model is better than other standard turbulence models. Accuracy analysis proves that the simulation results are accurate and can capture the movement of cell-level particles in the flow with shear stress. The results of the research are conducive to obtaining accurate and comprehensive analysis results in the equipment development phase.

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