Project · Test bench

WINDTUNNEL

Bench-scale wind tunnel for flow visualisation, built for teaching and demonstration. A 1.29 m duct with a bellmouth intake, run from custom boards.

Bench status
Type	Bench wind tunnel
Intake	Bellmouth
Visualisation	Vapour trails
Control	Onboard web server
Mass	Not yet measured
Stage	Ready for demonstrations

Full specification All four programmes

CAD render of the wind tunnel test section: a rectangular bolted section with a model mounted inside, the electronics compartment below it, and the diffuser opening out to the right — CAD render. Test section, electronics compartment and the start of the diffuser

Test section: 70 × 200mm
Overall length: 1.29m
Diffuser exit: 255mm
Flow range: 10–40km/h

Project

Vapour trails at 10–40 km/h

Everything on this bench serves one job: making the flow visible inside a 70 × 200 mm working section.

Air enters through a 221 mm bellmouth intake, passes a honeycomb flow straightener and a contraction cone, and reaches the 70 × 200 mm working section, which has a 170 × 85 mm window to watch through. A diffuser then opens the duct back out to 255 mm. A 5 V mist maker feeds vapour into the stream and an addressable LED strip lights the section, so the trails read against the background. Speed through the section is measured with a pitot tube.

Control is a web server running on the tunnel's own boards, so it is driven from a phone or a laptop on the same network rather than from a dedicated console. The electronics are custom PCBs. The assembly is modular: the bolted flanges between sections mean one section can be changed without rebuilding the tunnel.

The complete wind tunnel on a laboratory bench, printed in black: the vapour vessel and bellmouth intake at the left, the contraction cone, the lit test section with its electronics compartment below, the diffuser, and the exit chamber at the right. The printed general arrangement drawing lies on the bench at the left — The complete 1.29 m bench, intake at the left to exit at the right. Laboratory, May 2026

Reference sheet

WindTunnel dimensions and systems

Duct and test section · as built
Test section	70 × 200 mm
Viewing window	170 × 85 mm
Overall length	1.29 m
Inlet diameter	221 mm, bellmouth
Largest diameter	255 mm, at the diffuser exit
Mass	Not yet measured

Flow and visualisation · as measured
Flow range	10–40 km/h
Measured with	Pitot tube
Visualisation	Vapour trails, 5 V mist maker
Lighting	Addressable LED strip

Control and electronics · as built
Control	Onboard web server
Boards	Custom PCBs
Construction	Modular, bolted flanges
Power draw	Not yet measured

Mass and power draw are the two figures this bench has never had put to it, so they are marked rather than filled in. Everything else above is dimensioned on the general arrangement below. Two readings worth naming: the 170 and 85 marked across the test section are its viewing window, not the section itself, and the bellmouth is drawn at 221,03, published here as 221 mm.

General arrangement drawing of the wind tunnel, white lines on black. The elevation runs left to right: vapour vessel and pressure equaliser, bellmouth intake dimensioned 221,03, flow straightener, contraction cone, test section dimensioned 170 by 85, diffuser, and the 255 mm chamber, under an overall dimension of 1290,05. Three detail views below it: section A-A through the honeycomb flow straightener, the electronics compartment at 1:2, and the end elevation — General arrangement, as drawn. Flow runs left to right, bellmouth intake to diffuser. The labels are Portuguese, as drawn

Contact

What you can run in it

The working section is 70 × 200 mm and the assembly is modular, so a section can be changed for a different profile. If you teach fluid mechanics, or you need a particular flow made visible, tell us what you need to see.