Computational fluid dynamics (CFD) helps engineers understand how air and airborne contaminants are likely to move through an industrial space before ductwork and extraction equipment are installed. It is especially valuable where thermal plumes, cross-draughts, moving equipment or complex building geometry make simple assumptions unreliable.
CFD does not replace measurements, engineering calculations or commissioning. It complements them by testing a proposed airflow concept and making otherwise invisible flow patterns easier to evaluate.
What a CFD simulation represents
A CFD model divides the air volume into many calculation cells and solves equations for velocity, pressure, temperature and, where relevant, contaminant concentration. The quality of the result depends on the geometry, boundary conditions, turbulence model, mesh and the accuracy of the input data.
How the simulation workflow is built
- Create the geometry: model the hall, major machines, walls, openings, hoods and supply or extract terminals that materially affect airflow.
- Define operating conditions: enter exhaust and supply airflow, temperatures, process emissions, door states and other boundary conditions.
- Generate the computational mesh: use finer cells around jets, hoods and emission sources where gradients are greatest.
- Run the aerodynamic calculation: solve the model until the selected convergence and conservation checks are satisfied.
- Interpret the results: review velocity vectors, pressure fields, thermal layers and predicted contaminant paths.
What CFD can reveal in extraction design
Capture-point positioning
A hood can appear close to the source yet miss the plume because a cross-draught pushes emissions away. CFD allows alternative positions, hood shapes and airflow rates to be compared before fabrication.
Stagnant and recirculation zones
Large machines, walls and structural elements can create pockets with weak air movement. These areas may accumulate heat or residual contamination even when the total room airflow appears adequate.
Interaction with make-up air
Supply-air jets can support capture or disrupt it. A model can show whether replacement air reaches the occupied zone gently or crosses the emission path at excessive velocity.
Energy optimisation
The objective is not simply to maximise airflow. By improving hood geometry and air distribution, the required volume may be reduced while maintaining capture. Any predicted reduction is then verified through detailed calculations and commissioning measurements.
Applications
CFD can support welding and cutting areas, paint shops, high-bay halls, thermal processes, local extraction enclosures and facilities where several ventilation systems interact. It is also useful when an existing hall has persistent hot spots, cross-draughts or contaminant migration that cannot be explained from drawings alone.
Classical calculations and CFD
Conventional design methods remain essential for hood airflow, duct velocity, pressure loss, filter loading and fan selection. CFD adds a three-dimensional view of the room and process zone. The strongest approach combines both: calculations define the equipment, while simulation tests how the surrounding airflow may affect capture.
Limits and validation
A simulation is only as reliable as its assumptions. Simplified geometry, uncertain emissions, doors that operate differently from the model or inaccurate supply-air data can change the result. Models should be checked for mass balance, sensitivity and plausible flow behaviour. Whenever possible, measurements from the existing process or commissioning are used to validate and refine the model.
When CFD is worth considering
Simulation is most useful when the cost of changing the installation after construction is high, the geometry is complex or airflow interactions are critical. It should answer defined design questions rather than produce attractive images without engineering decisions.
ALWO can integrate airflow analysis with the design of capture points, ducting, filtration and fans. Contact our technical team to discuss whether CFD would add value to your extraction project.
