# Discrete Phase Model (DPM)

## What is the Discrete Phase Model (DPM)?

Discrete Phase Model is a subsection to Multiphase flows. A discrete phase model (DPM) is used when the aim is to investigate the behavior of the particles from a Lagrangian view and a discrete perspective. The difference between the Lagrangian and the Eulerian view is that fluid behavior in the Lagrangian view is examined based on particle tracking of a particulate flow; Whereas fluid behavior is considered in the Eulerian view based on the assumption of a finite volume element in the fluid flow path.

In Discrete Phase Model, the continuous phase is solved using Navier-Stokes equations. At the same time, the discrete phase is simulated by tracking a large number of particles, bubbles, or droplets passing through the calculated continuous flow field. It should be noted that the discrete phase can exchange momentum, mass, and energy with the continuous phase. This method can be made much simpler by ignoring the interaction of particles (as well as droplets and bubbles) with each other. Of course, this can happen when the discrete phase, even with a large mass, has a much smaller volume (less than 10%) than the continuous phase. After each iteration of the continuous phase calculations, the particle paths (as well as bubbles or droplets) are calculated and determined separately.

### Dense Discrete Phase Model (DDPM)

The dense discrete phase model (DDPM) is a Lagrangian parcel-based approach that models particle collisions and uncorrelated translations using the kinetic theory of granular flows (KTGF). This approach has numerous advantages over the established Eulerian two-fluid model (TFM). These include better resolution of particle clusters and bubbles, more natural incorporation of particle size distributions, and better handling of crossing particle jets/clusters. In this study, results from the DDPM are compared to dedicated experiments and TFM simulations over a wide range of fluidization velocities, particle sizes, and bed loadings. Special attention was given to ensure that the frictional effects typical of such dense particle flows are accounted for. The DDPM proved capable of reproducing the good fit to experiments achieved by the TFM on a significantly coarser mesh.

### Discrete element method (DEM)

The discrete element method (DEM) is an intuitive method in which discrete particles collide and other surfaces during an explicit dynamic simulation. Typically, each DEM particle represents a separate grain, tablet, shot peen, etc. DEM does not apply to situations in which individual particles undergo complex deformation. Therefore, DEM is, unlike conceptually, more straightforward than the smoothed particle hydrodynamic (SPH) method in which groups of particles collectively model a continuum body. For example, DEM is well-suited for particle mixing applications. In this application, DEM is used to model the initially separated blue and white particles, and rigid finite elements are used to model two mixing augers and the box-shaped container. Another example of using DEM for a mixing application is described in the Mixing of granular media in a drum mixer.

## Discrete Phase simulations in ANSYS Fluent software

The basic theory behind the Discrete Phase modeling process can be explained through Newton’s second law of motion (i.e., ). As was mentioned in the previous paragraph, the continuous phase equations are solved first to obtain the flow field and its related parameters. Then based on different projects, one may assume various types of forces that apply on the particulate phase. The simplest force that always exists is the drag force (for spherical particles in stokes flows, Drag Force =  in which μ is the fluid viscosity, d is the particle’s diameter,  is fluid’s velocity, and  Is particle’s velocity). Finally, we can track each particle inside our continuous phase by coupling the Navier-Stokes equations with Newton’s equation.

The Discrete Phase in ANSYS FLUENT can be used to model different types of phenomena, including:

•  calculation of the discrete phase trajectory using a Lagrangian formulation that includes the discrete phase inertia, hydrodynamic drag, and the force of gravity, for both steady and unsteady flows
•  prediction of the effects of turbulence on the dispersion of particles due to turbulent eddies present in the continuous phase
•  heating/cooling of the discrete phase
•  vaporization and boiling of liquid droplets
•  combusting particles, including volatile evolution and char combustion to simulate coal combustion
•  droplet breakup and coalescence
•  Erosion or accretion

There are various types of built-in forces that can be applied to make the created project even more realistic such as Thermophoretic, Brownian, Saffman forces, etc. Also, user-defined functions are always there for modeling the forces that are not predefined in the software.

These modeling capabilities allow ANSYS FLUENT to simulate a wide range of discrete phase problems, including particle separation and classification, spray drying, aerosol dispersion, bubble stirring of liquids, liquid fuel combustion, and coal combustion.

## MR-CFD, an expert in the field of Discrete Phase simulations

With several years of experience simulating a wide range of problems in various CFD fields using Fluent software, the MR-CFD team is ready to offer extensive modeling, meshing, and simulation services. Simulation Services for Discrete Phase simulations are categorized as follows:

• CFD simulation particle separator from gas using cyclone
• Using particle droplet combustion in two and four-stroke internal combustion engine
• Simulation particle settling by the gravity body force
• Wood combustion using the discrete phase model
• Sand particle tracking in the pond riverside
• Particle tracking in spray dryer using the DPM model
• Simulation of using magneto-hydrodynamic (MHD) body force for increasing performance of cyclone
• Erosion modeling in knee

You may find the related products in the categories mentioned above in our CFD shop by clicking on the following link:

https://www.mr-cfd.com/product-category/fluent-modules/discrete-phase-model/

Our services are not limited to the mentioned subjects. The MR-CFD team is ready to undertake different and challenging projects in the Discrete Phase Modeling field ordered by our customers. You can consult with our experts freely and without charge at first, and then order your project by sending the problem details to us using the following address.

[email protected]

By entrusting your project to the MR-CFD team, you will not only receive the related project’s files (Geometry, Mesh, Fluent files). Also, you will be provided with an extensive tutorial video demonstrating how you can create the geometry, mesh, and define the needed settings in the Fluent software all by yourself. And these all come with post-technical support from the MR-CFD team.

MR-CFD experts are ready to fulfill every Computational Fluid Dynamic (CFD) needs. Our service includes industrial and academic purposes considering a wide range of CFD problems. MR-CFD serves in three main categories: ANSYS Fluent Consultation, ANSYS Fluent Training, and ANSYS Fluent Project Simulation. MR-CFD company has gathered experts from various engineering fields to ensure the quality of CFD services. Your CFD project would be done the shortest time, with the highest quality and reasonable cost.