DPM Post-Processing Guide — ANSYS Fluent 2024 R1

#+CATEGORY: cfd

#+TAGS: DPM post-processing visualization tracks concentration

#+MATURITY: growing

DPM Post-Processing :: Master Guide for ANSYS Fluent 2024 R1

This page covers every post-processing tool Fluent provides for DPM results: Particle Tracks graphics, DPM Concentration contours, DPM Summary reports, animation of transient tracks, and the CFD-Post workflow for publication-quality output. Target application: shisha PM2.5 simulation (3D, steady-state, inert particles).

Overview — What You Get After a DPM Run

After a DPM calculation completes, Fluent stores the following per-particle data:

• Final position ($(x, y, z)$)
• Final velocity ($(u, v, w)$)
• Diameter (if changing)
• Temperature (if heat transfer active)
• Status: escaped, trapped, incomplete (hit max steps)
• Residence time (time-in-domain)
• Wall impact data (position, velocity, angle, diameter)

All post-processing tools read from this stored data. The data persists until you re-run the DPM iteration or reload a different case.

Particle Tracks

Access: Graphics and Animations > Particle Tracks > Settings...

The Particle Tracks display renders 3D trajectories of a sample of parcels through the domain. This is the primary qualitative tool for understanding where particles go.

Settings panel:

Color-by options (most useful first): 1. Residence Time — shows how long particles linger in regions 2. Diameter — shows size evolution (relevant if evaporation active) 3. Velocity Magnitude — shows acceleration/deceleration zones 4. Particle Temperature — shows heating/cooling along trajectory 5. Injection ID — distinguishes multiple injection sources

TIP: With 10 000 parcels, rendering all tracks overwhelms the display. Set Skip = 50 to render 200 representative tracks, then toggle to Skip = 1 for a detailed view of a subset.

Saving track data: 1. In the Particle Tracks dialog, click Save.../Save.../ 2. Fluent writes a data file with columns: x y z u v w d T status time injection-id 3. This file can be read back as a file injection for replay or imported into external post-processing tools

TUI commands for Particle Tracks

``` ; Display particle tracks display/particle-tracks settings

; Set injection display/particle-tracks settings > injection-names <name>

; Color by residence time display/particle-tracks settings > color-by residence-time

; Set skip factor display/particle-tracks settings > skip <N>

; Save track data to file sample/particle-tracks <filename>

; Sample specific injection sample/particle-tracks <filename> <injection-name> ```

DPM Concentration Contours

Access: Contours > DPM Concentration

DPM Concentration contours show the spatial distribution of particle mass or number concentration on any surface (plane, iso-surface, boundary wall). This is the primary quantitative visualization tool for exposure analysis.

Two concentration variables:

How Fluent computes concentration: Fluent bins parcels into cells, then divides the total particle mass (or count) in each cell by the cell volume. For steady tracking, the concentration represents a time-averaged field. For transient tracking, it is an instantaneous snapshot.

Contour settings for shisha PM2.5: 1. Contours of > DPM > DPM Concentration 2. Surface: select a cutting plane (e.g., mid-plane through the bowl) or the outlet plane 3. Range: Auto (or set manually based on expected concentration) 4. Levels: 20 (smooth gradient) 5. Node Values: ON (interpolated) 6. Draw Mesh: ON (optional, shows cell structure)

Number density from mass concentration: $$n = \frac{C_{\text{mass}}}{\rho_p \cdot \frac{\pi}{6} d_p^3}$$

For PM2.5 with $\rho_p = 1200$ kg/m^3 and $d_p = 1 \mu$m: $$n = \frac{C_{\text{mass}}}{1200 \times \frac{\pi}{6} (10^{-6})^3} = \frac{C_{\text{mass}}}{6.28 \times 10^{-16}} \approx 1.59 \times 10^{15} \times C_{\text{mass}} \text{ particles/m}^3$$

Breathing-zone quantification: See DPM Concentration Fields — Mass and Number Quantities for detailed procedures on extracting concentration at specific locations (mouth/nose height).

DPM Summary Report

Access: Reports > Discrete Phase > Summary...

The DPM Summary report provides aggregate statistics over all tracked parcels:

Interpreting the summary for shisha:

• Escaped through outlet = smoke that exits the device
• Trapped on walls = deposition on glass or body surfaces
• Incomplete = numerical issue (increase max steps; see DPM Numerics)
• The ratio Trapped / (Trapped + Escaped) gives the deposition fraction

TUI command: ``` report/dpm-summary ```

Wall Deposition — Reporting Trapped Particles

For trap boundaries, Fluent records every particle impact. Use these reports to quantify where particles deposit.

Surface integrals for DPM:

Per-wall-zone deposition mass: 1. Reports > Discrete Phase > Wall Fluxes... 2. Select wall zones 3. Fluent reports: mass trapped, mass escaped, net mass flux

*Animation of Transient Particle Tracks :PROPERTIES: :ID: cfd_dpm-post-processing--animation :CUSTOM_ID: cfd_dpm-post-processing--animation :END:

For transient DPM tracking, Fluent can animate particle positions over time.

Setup: 1. Graphics and Animations > Particle Tracks > Settings... 2. Enable Animate (in the Options section) 3. Set Frame Count and Duration 4. Run transient DPM calculation 5. Fluent updates the track display at each time step

Exporting animation: 1. File > Animation > Record... 2. Set format (MP4, GIF, or image sequence) 3. Set Recording Window to your graphics window 4. Run the calculation; Fluent records frames automatically

For steady tracking: No animation is available (all tracks are computed simultaneously). Instead, use Skip and Color by Residence Time to convey temporal information statically.

CFD-Post Workflow

ANSYS CFD-Post provides more advanced visualization than Fluent's built-in graphics. For publication-quality figures, export from Fluent and post-process in CFD-Post.

Export procedure: 1. In Fluent: File > Export > EnSight Case... 2. Select Output volume = ALL 3. Select Output surface = ALL 4. Enable Write DPM particle data 5. Save the .case and .geo files

In CFD-Post: 1. Load the .case file 2. Particle tracks appear under Particle Tracks in the navigator 3. Create contours, vector plots, and streamlines from the particle data 4. Use Expressions to compute derived quantities (concentration, number density)

CFD-Post-specific advantages:

• Higher-quality rendering (anti-aliased lines, better color maps)
• Iso-surfaces of particle concentration
• Particle tracks colored by multiple variables simultaneously (using Variable selector)
• Clip planes for internal views
• Direct LaTeX-compatible figure export

Post-Processing Checklist for Shisha PM2.5

See Also

• DPM Theory -- Governing Equations
• DPM Setup and Activation
• DPM Sample Files — Cutting Planes and Iso-Surfaces
• DPM Concentration Fields — Mass and Number Quantities
• DPM Erosion and Accretion Maps
• DPM Statistics — Histograms and Residence Time
• Shisha PM2.5 DPM Case Study