DPM Setup and Activation in ANSYS Fluent 2024 R1
#+CATEGORY: cfd
#+TAGS: DPM Fluent setup activation
#+MATURITY: growing
DPM Setup Activation :: Step-by-Step for ANSYS Fluent 2024 R1
This page walks through the complete DPM activation procedure in ANSYS Fluent 2024 R1. It covers model activation, interaction settings, injection creation, boundary conditions, and the numerical knobs that determine convergence. Target application: shisha PM2.5 simulation (3D, steady-state, inert particles).
When to Activate DPM
Activate DPM when your problem involves:
- Solid particles suspended in a gas or liquid
- Liquid droplets (spray, mist, injection)
- Bubbles in a liquid
- Evaporation, boiling, or combustion of discrete particles
- Residence time distribution analysis
Do not activate DPM when:
- The dispersed phase volume fraction exceeds 10--15% (use DDPM or Eulerian)
- You have two interpenetrating continuous phases (use VOF or Eulerian)
- Particle-particle collisions dominate (use DDPM with DEM)
Activation Procedure
Step 1 -- Enable the DPM model: 1. Open the Model tree: Models > Discrete Phase 2. Set Discrete Phase Model to On 3. Click Edit... to open the DPM dialog
Step 2 -- Choose tracking mode:
| Mode | Use Case | Setting |
|---|---|---|
| Steady | Continuous injection (draw) | Interaction unchecked (or checked for coupling) |
| Transient | Puff injection, time-varying | Unsteady Particle Tracking checked |
For shisha continuous draw: select Steady.
Step 3 -- Set interaction options: 1. In the DPM dialog, set:
- Interaction with Continuous Phase:
ONif two-way coupling is needed;OFFfor one-way - Number of Continuous Phase Iterations per DPM Iteration: 1 (default for one-way)
2. If coupling is on:
- Max Number of Iterations: 20--50
- Under-Relaxation Factor for DPM: 0.5 (lower if divergence occurs)
Step 4 -- Enable optional physics in the Physical Models tab:
- Stochastic Tracking: Enable, set Number of Tries = 10--20
- Brownian Force: Enable (for PM2.5 sub-micron -- requires UDF)
- Thermophoretic Force: Enable if temperature field is computed
- Saffman Lift Force: Optional for PM2.5
- Two-Way Turbulence Coupling: Enable only with high mass loading
Step 5 -- Create injection(s): See DPM Injection Types.
Step 6 -- Set DPM boundary conditions: See DPM Boundary Conditions.
Step 7 -- Solve: 1. Initialize the continuous phase (hybrid initialization recommended) 2. Run continuous phase to convergence (500+ iterations for steady) 3. If coupled: Calculate > Iterate with DPM iterations interleaved 4. If uncoupled: run DPM once after flow converges via Report > Discrete Phase > Iterate
Continuous Phase Prerequisites
Before enabling DPM, the continuous phase must be set up:
| Item | Recommendation for Shisha PM2.5 |
|---|---|
| Solver | Pressure-based, steady |
| Turbulence | k-omega SST (best for near-wall; or k-epsilon RNG) |
| Near-wall treatment | Enhanced wall treatment; $y^+ < 1$ for deposition |
| Material (air) | Incompressible ideal gas or constant density |
| Material (particle) | Create custom solid material: $\rho_p = 1200$ kg/m^3, $c_p = 1000$ J/(kg.K) |
| Operating pressure | 1 atm (or ambient lab pressure) |
| Temperature | Enable energy equation if bowl is heated |
DPM Material Setup
PM2.5 smoke particles need a custom material:
1. Open Materials > Solid > Create/Edit... 2. Name: pm25-smoke 3. Density: 1200 kg/m^3 (typical carbonaceous aerosol) 4. Specific heat: 1000 J/(kg.K) 5. Thermal conductivity: 0.1 W/(m.K) (not critical for inert)
Assign this material in the injection panel.
Injection Setup -- Quick Reference
For shisha PM2.5 (smoke entering from hose tip or bowl):
1. Models > Discrete Phase > Injections... > Create 2. Type: surface (inject from a zone boundary) 3. Material: pm25-smoke (the custom solid) 4. Particle Type: inert 5. Injection properties:
| Property | Value | Notes |
|---|---|---|
| Diameter | $d_{\text{mean}} = 1.0$ \mu m | Log-normal distribution |
| Spread parameter | 1.5 | Log-normal width |
| Number of parcels | 10 000 | Statistical convergence |
| Total flow rate | 5 mg/min (typical) | Match your experimental draw rate |
| Temperature | 50 degrees C (cool smoke) | Adjust to bowl outlet temp |
| Velocity | 0.5 m/s (typical draw velocity) | Or set mass flow rate |
6. Select the injection surface(s) in the Boundary Zones list 7. Click OK
TIP: Use surface injection for a known physical inlet. Use file injection to read particle data from a previous simulation or measurement.
Boundary Conditions for DPM Particles
For each boundary zone, set the DPM behavior in Cell Zone Conditions > Boundary Conditions > [zone] > DPM tab:
| Boundary | DPM Behavior | Use Case |
|---|---|---|
| Inlet (air) | escape | Air enters; particle tracks from it |
| Outlet (exhaust) | escape | Particles leave domain at exhaust |
| Walls (glass/body) | trap or reflect | Trap = particle sticks; Reflect = bounce |
| Bowl surface | trap | Smoke deposits on bowl inner walls |
For trap: particle is removed at the wall. Use this for deposition analysis. For reflect: particle bounces. Specify normal and tangential restitution coefficients.
Numerical Settings -- Max Steps and Tolerance
| Setting | Recommended Value | Notes |
|---|---|---|
| Max Steps | 50 000 (3D domain) | Larger if particles stay in domain long |
| Tolerance | $1 \times 10^{-5}$ | Tighter tolerance --> more accurate trajectory |
| Length Scale | Mesh-based (default) | Use Refine Path for highly curved paths |
| Timescale Control | Variable time-step | Default; adjusts step per trajectory region |
| Accuracy Control | On | Refines trajectory near boundaries |
TUI commands for DPM numerics: ``` solve/set/dpm-iterations <n> solve/set/dpm-under-relaxation <factor> define/models/dpm/interaction> max-steps <n> ```
See DPM Numerics -- Solver Settings and Convergence for details.
Steady vs Transient DPM -- Quick Decision
| Mode | When to Use | Fluent Setting |
|---|---|---|
| Steady | Continuous draw, constant injection | Interaction with Continuous Phase |
| Transient | Puff-by-puff, time-varying injection | Unsteady Particle Tracking |
For shisha steady draw: use Steady DPM tracking. The injection is constant. The flow field is steady-state. Particles reach terminal trajectories.
For later transient study (puff): switch to Transient. Enable Unsteady Particle Tracking and set a time-step for the particle integration.
Workflow Summary
``` 1. Solve continuous phase to convergence
| -- Pressure-based, steady, k-omega SST |
| -- 500+ iterations until residuals drop below 1e-4 |
2. Enable DPM
| -- Models > Discrete Phase > On |
| -- Steady tracking |
| -- Stochastic tracking: 10 tries |
| -- Physical models: Brownian (UDF), thermophoretic |
3. Create injection
| -- Surface injection at smoke source |
| -- Material: pm25-smoke (inert, rho=1200, d_mean=1.0 um) |
| -- Log-normal distribution, spread=1.5 |
| -- 10 000 parcels |
4. Set boundary conditions
| -- Walls: trap or reflect |
| -- Outlets: escape |
5. Run DPM
| -- Uncoupled: Report > Discrete Phase > Iterate |
| -- Coupled: Calculate > Iterate with DPM iterations |
6. Post-process
| -- Particle tracks |
| -- DPM concentration contours |
| -- Sample files on planes |
| -- Statistics (escape/trap counts) |
```
See Also
- DPM Theory -- Governing Equations
- DPM Injection Types
- DPM Boundary Conditions
- DPM Physical Models -- Fluent Panel
- DPM Numerics -- Solver Settings
- DPM Post-Processing Guide
- Shisha PM2.5 DPM Case Study
- DPM Coupling -- One-Way vs Two-Way, Source Terms, and Decision LogicCFD - DPM
- DPM Drag Models -- All Drag Laws, Validity Ranges, and UDF ImplementationCFD - DPM
- DPM Heat and Mass Transfer -- Convective Heating, Evaporation, Boiling, and RadiationCFD - DPM
- DPM Post-Processing Guide — ANSYS Fluent 2024 R1CFD - DPM
- Shisha PM2.5 DPM Case Study -- Setup, Configuration, and ValidationCFD - DPM
- DPM Theory -- Governing Equations, Parcels, and Particle Force BalanceCFD - DPM
- DPM Turbulence Interaction -- Discrete Random Walk, Stochastic Tracking, and DRW Deep DiveCFD - DPM