Introduction to Coupled CFD-DEM Modeling
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The document provides an overview of coupled CFD-DEM modeling approaches, detailing micro, meso, and macro scales in fluid-particle interactions. It discusses how particle motion and interactions with fluid are modeled using various conservation equations and closure laws, emphasizing the importance of mesh size relative to particle size. The piece also references a specific formulation and application within multiphase flows.
Introduction to Coupled CFD-DEM Modeling
- 1. Introduction to Coupled CFD-DEM Modeling By: Submitted To: Khusro Kamaluddin 801783008 Dr. S.S. Mallick
- 2. Multi-phase Modeling CFD → Eularian Eularian Approach → Fluid & Particles are considered to be in a continuum CFD-DEM → Eularian Lagrangian Approach → Fluid is considered to be in continuum → Individual particles are tracked using lagrangian approach
- 3. Modelling Approaches Micro Scale Trajectory of each particle is calculated through eqn of motion Meso Scale Both fluid and particle are considered interpenetrating continua Conservation eqns are solved over a mesh of cells Mesh size is small enough to capture features of flow and large enough to allow averaging the properties Macro Scale The motion of fluid along with particles is treated as 1 Dimensional Multi Scale
- 4. Multi-Scale Approach ① Micro Approach (Fluid-Micro, Particle-Micro) o Governed by Navier Stokes Eqn oEmpirical relations for drag and lift are not required o Used when : Inertial force of particle is very small (Liquid-particle) Fluid lubricating effect is significant (Dense-phase liquid-particle flow) oExample : Direct Numerical Simulation-Discrete Element Method(DNS-DEM)
- 5. Multi-Scale Approach ② Meso Approach (Fluid-Meso, Particle-Meso) o In addition to the fluid the assemblage of particles is considered as the second continuum phase. oFlow field is divided into small cells to capture emotion of both phases. o𝐶𝑒𝑙𝑙 𝑆𝑖𝑧𝑒 > 𝑃𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑆𝑖𝑧𝑒 oModelling is done by using Momentum Conservation Mass Conservation At each cell, leading to Averaged Navier Stoke’s Equation and continuity Equation.
- 6. Multi-Scale Approach ② Meso Approach (Fluid-Meso, Particle-Meso) oCapturing Solid particle motion greatly depends on closure law used. oSome simplifications in closure law improve commercial applicability bur reduce generality of the approach. oUsed in : Non-reacting and reacting multiphase flow at lab level.
- 7. Multi-Scale Approach ③ Macro Approach (Fluid-Macro, Particle-Macro) oConservation eqns are written for bubbles and emulsion o1D description of gas-particle flow oMain output is generally the pressure drop due to flow of fluid and particles. oDarcy Weisbach Eqn in used for fluid pressure drop. oParticles are balanced by fluid drag formula(Momentum Balance) oExample: Two Phase Modelling(TPM) of fluidization
- 8. Multi-Scale Approach ④ Macro-Micro Approach (Fluid-Macro, Particle-Micro) oEmpirical correlations are utilized to calculate forces acting on the particles (i.e. drag and lift) oTranslation and rotational motion of particles → Based on Newton’s and Euler’s second law. oAt low particle concn → Effect of particle on fluid motion is neglected oAt high particle concn → Closure law should be modified to account for the closeness of surrounding particles. oGenerally in this approach the flow field that varies in one dimension only is not discretized.
- 9. Multi-Scale Approach ④ Meso-Micro Approach (Fluid-Meso, Particle-Micro) oReferred to as CFD-DEM oFlow Field is divided into cells o𝐹𝑙𝑜𝑤 𝐹𝑖𝑒𝑙𝑑 > 𝑀𝑒𝑠ℎ 𝑆𝑖𝑧𝑒 > 𝑃𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑆𝑖𝑧𝑒 oEffect of particle on fluid is calculated by considering volume fractions of each phase and momentum exchange.
- 11. Reference • Coupled DEM-CFD Modeling Formulation, Implementation and application to multiphase flows, H. R. Norouzi, R. Zarghami, R. S.Gharebagh, N. Mostoufi, 2016 John Wiley & Sons