CFD · Computational fluid dynamics

External flows (CFD)

Flow around parts, products and small structures: the forces the air exerts on them, the wind loads their structure has to carry, and how wind moves air through a space.

Flow field around an aerofoil section
What it covers

The flow around the object, and what it does to it.

  • Aerodynamic forces. Drag, lift and pressure distribution on parts and products.
  • Wind loads on structures. Pressures from defined wind scenarios, applied to a structural model to check stresses and deformations.
  • Flow behaviour around parts. Separation, wakes and sheltered zones that affect performance or dust and heat build-up.
  • Wind-driven ventilation. How openings and their position move air through a space.

Typical questions

  • What aerodynamic loads may act on a structure?
  • Which wind direction is the critical one?
  • How does a change of shape reduce drag or load?
  • Where should openings go for natural ventilation?
Worked examples

How CFD fits into a wider engineering investigation.

Typical situations, described the same way: the request, what a complete assessment has to consider, what simulation adds, and what decides the outcome.

CFD and FEA combined

Wind loading on a small structure

A manufacturer is developing a small structure or product that will be exposed to wind.

An integrated study may involve
  • Defining the intended installation conditions
  • Establishing the relevant wind scenarios
  • Aerodynamic forces from CFD or appropriate engineering methods
  • Applying those loads to a structural model
  • Stresses, deformations and critical components
  • Comparison with the applicable design requirements
What simulation adds

Loads from the flow model feed the structural model, so the whole chain from wind to stress is traceable.

Limits

Where formal certification, regulatory compliance or public safety obligations apply, the analysis must be performed within the relevant standards and professional framework.

Ventilation

Natural ventilation instead of mechanical cooling

A building or product designer wants to use natural airflow and depend less on mechanical cooling.

CFD may help explore
  • Opening and window arrangements
  • Air inlet and outlet locations
  • Wind direction and velocity
  • Internal airflow patterns
  • Stagnant or poorly ventilated regions
  • The influence of the geometry
What CFD adds

It investigates defined scenarios and supports design decisions about openings and layout.

Limits

Real environmental conditions vary. CFD can investigate defined scenarios, but it cannot guarantee performance under every possible weather condition.

Open-source CFD

Professional flow analysis, without enterprise licence costs.

Commercial CFD packages often cost thousands of euros a year per seat, and that cost ends up in the price of every study. We work with a mature open-source toolchain instead, so an SME pays for engineering time, not for software licences.

The solver, OpenFOAM, is one of the most widely used CFD codes in industry and research: steady and transient, laminar and turbulent flow.

Honest about the limits

Where a question genuinely needs a feature that only a commercial package offers, we say so before the work starts.

The workflow

  1. Geometry: FreeCAD

    The fluid domain is built from the CAD model, with details removed where they don't affect the flow.

  2. Mesh: Netgen

    The domain is meshed, with refinement near walls, openings and wherever the flow changes quickly.

  3. Solution: OpenFOAM

    Physical models and boundary conditions are set, each assumption is recorded, and convergence and sensitivity are checked.

  4. Post-processing: ParaView

    Velocities and pressures are extracted and presented as streamlines, sections and figures for the decision.

This offering is not approved or endorsed by OpenCFD Limited, producer and distributor of the OpenFOAM software via www.openfoam.com, and owner of the OPENFOAM® and OpenCFD® trade marks. Other product names are trademarks of their respective owners.

Related projects

A real project.

CFD · Mechanical design

A hydroponic laboratory in a container

The airflow corrected with CFD before construction.
See the project

All projects: CFD

Do you have an engineering question? Let's discuss it.

Tell us what you are developing, changing or trying to fix. We first look at the engineering question, then say plainly what is worth doing: a calculation, a design review, a test, a simulation, or a combination.

Complimentary first site visit & analysis Custom proposal, regardless of project scale Strict confidentiality & NDA protection