Multiphase model
- 2. What is a multiphase flow ? • Multiphase flow is a phenomena of simultaneous flow of mixtures of phases such as gases (like bubbles ) in liquid , or liquid (like droplets) in gases and similar such flows. • By multiphase flow we mean that its a mixture of phase and each phase in it has a distinct velocity field. • Multi-phase flows exist in many different forms. • Two-phase flows can be classified according to the state of the different phases : - Gas-Liquid mixture - gas-solid mixture - Immiscible-liquid mixture - Liquid-solid mixture
- 3. Multiphase Modeling by Ansys fluent : There are tow approaches for the numerical calculation of multiphas 1. The Euler – Lagrange approach : The Lagrangian discrete phase model in FLUENT follows the Euler- Lagrange approach . 2 . The Euler-Euler approach : In FLUENT, three different Euler-Euler multiphase models are available: the volume of fluid (VOF) model, the mixture model, and the Eulerian model .
- 4. Discrete Phase Model (DPM) : • Discrete Phase Model is a multiphase model in which the dispersed phase is tracked in a lagrangian reference frame . • Two different phases are defined in the DPM model: A continuous phase and a particle phase . • The discrete phase is modeled by the lagrangian method . • The continuous phase is modeled by eulerian method • The discrete and the continuous phases are coupled through sources terms in the governing equations .
- 5. Coupling between phases : • One-way coupling : • DPM source term is updated . • Source term of continuous phase is not updated - Particle motion is affected by the continuous phase . - Continuous phase is not affected by the particle flow . • Two-way coupling : • Transfer of momentum, energy and mass from particles to the continuous phase is considered by means of source terms. • Source terms of both DPM and continuous phase are updated . - Particles and continuous flow interact with each other .
- 6. Discrete Phase Modeling Setup : • Type of injection . • Initial conditions . • Turbulence Models . • Heat and mass transfer laws . • Physical Modeling inputs . • Tracking parameters . • Numerics . • Interaction with continuous phase . • Particle behavior at boundaries .
- 7. DPM Calculation - Steady Flow :
- 8. DPM Calculation - Unsteady Flow :