Industrial ventilation · Computational fluid dynamics

Underground station ventilation CFD.

Diesel exhaust dispersion inside an underground railway station. A CFD-led investigation into how heat, train position, extraction ducts and fan momentum affect the air people breathe.

EXPLORE THE SIMULATIONS THE ENGINEERING OUTCOME

Project study · OpenFOAM · Buoyant flow + pollutant transport
All displayed contours originate from the supplied engineering report.

CFD / FINAL CONFIGURATIONFIG 9.3 · Z = 1.8 m

source-directed exhaust controlNO₂

Original CFD result: normalized nitrogen dioxide in the final edge-locomotive case, showing a localized near-source red region and mostly blue station interior.

BREATHING-ZONE SECTIONRECOMMENDED OPERATION

FROM THE FINAL CFD RESULT

415 mApproximate platform length

21.64 MCells in documented production mesh

210 °CModeled exhaust temperature

06Reviewed engineering configurations

01 / The intervention sequence— Explore

Ventilation and contaminant distribution

Six configurations were evaluated in the report. Scrub through the scenarios and switch between horizontal breathing-zone sections and longitudinal plume views to see how the exhaust footprint changed.

CASE 01 / 06

Corrected central stopping position

Main duct extraction on · no supplementary fans

Unfavourable

VIEW THE CFD SECTION

FIG 9.1 / CASE 01 CFD concentration plot from the first reviewed scenario.

Original report Figs 9.1–9.2 · NO₂ spatial footprint · schematic cross-case viewing sequence

Engineering finding

Correcting upper-station pressure and openings did not prevent extensive pollutant spread with the locomotive stopped centrally.

CENTRAL POSITIONEXIT POSITION

Comparison note: these historical figure exports have differing color scales, including absolute and normalized views. Compare the shape and reach of the plume, not pixel colors as a common quantitative scale. This is a sequence of distinct steady simulations, not a time animation.

Direct visual comparison

Change the source location.
Change the occupied-zone outcome.

Drag the reveal control to compare a selected earlier configuration against the edge-locomotive result. All comparison strips were extracted directly from the report's original six-case montage.

Crucial distinction: the main duct extraction remains active in the recommended case. Only the nearest supplementary fan runs outward.

Earlier scenario

← FINAL / NEAR EXITCENTRAL / EARLIER →

02 / Pollutant-field explorer— Evidence

Comparison of the resulting flow fields

Examine the original final-case field outputs. Change pollutant or cross-section without distorting the spatial proportions of the CFD plots.

Nitrogen dioxide / breathing zone

Final edge-locomotive configuration · Z = 1.8 m

NORMALIZED CONCENTRATION

Final case normalized NO2, horizontal section at height 1.8 meters.

The near-source exceedance remains, but the main station interior is largely below the selected project threshold.

Blue: lower normalized concentrationRed: higher normalized concentrationPlot display capped at C / C_limit = 5

03 / Engineering geometry— Model

Full-scale station CFD model

The computation includes platforms, the train, structural elements, extraction ducts, escalator connections and open station-end boundaries. Explore the actual model views taken from the report.

GEOMETRY / FULL MODEL Isometric CFD geometry of underground station with trains, ducts and structural parts.

Complete station computational geometry · Report Fig 4.1

ENGINEERING SUMMARY

Project scope and interpretation

Engineering question: How do exhaust configuration and source position affect airflow and contaminant dispersion in an underground railway station?
System / operating scope: Approximately 415 m station model; six documented scenarios; modeled exhaust and ventilation conditions.
Work performed: Compared six airflow and source/extraction configurations using a large three-dimensional model with documented 21.64-million-cell production mesh.
Analysis / input basis: CFD flow and species-transport calculations with geometry, mesh and operating assumptions described in the original project material.
Finding or displayed evidence: The interactive viewer compares the modeled ventilation and contaminant fields, including an NO₂ plane at breathing-zone height in the final case.
Limits / validation status: Numerical scenario predictions, not direct personal-exposure measurements or evidence of regulatory compliance.
Decision supported: Comparison of ventilation/extraction arrangements and source positioning.

Fluid Systems & Industrial Equipment →Discuss a related project →

04 / Numerical method

Geometry, meshing and transport modelling

The aim was to compare operational scenarios using resolved three-dimensional buoyant airflow and passive pollutant transport.

01 / GEOMETRY

Station reconstruction

Long enclosure, outer-track locomotive, ventilation ducts, openings, and the exit region built from drawings and iterative clarifications.

02 / MESH

Hex-dominant domain

blockMesh + snappyHexMesh with local refinement around the locomotive, duct openings and supplementary fan regions. Documented production mesh: 21.64 M cells.

03 / FLOW

Thermally buoyant RANS

OpenFOAM buoyantSimpleFoam with k–ω SST for steady velocity and temperature fields, including warm exhaust and ventilation momentum sources.

04 / DISPERSION

Four transport fields

Passive-scalar transport of CO, NOx, NO₂ and PM on the computed airflow; concentration fields compared against selected project thresholds.

Scope and limitations. Figures demonstrate comparative engineering performance, not certified air-quality compliance. Formal mesh independence was not established in the available record; NO↔NO₂ chemistry and detailed particulate settling were not modeled. The final moved-locomotive case did not have a separately documented mesh statistics log.

05 / The decision

“Better source positioning beat more fans.”

The strongest tested option moved the locomotive near the open station edge, retained the main duct extraction, and operated only the nearest supplementary fan outward.

Jet fans meaningfully improved plume directionality for central stopping, but residual pollutant hotspots remained. Source relocation reduced the long exposure path through the occupied station.

In the recommended case, most of the principal occupied zone fell below the selected project thresholds, while a localized exceedance remained near the locomotive exhaust source.

REVISIT CFD EVIDENCE ↑

Underground station ventilation CFD.