Compact open circuit wind tunnels
Blower type wide-angle open circuit wind tunnel for propellers
We started this project because we needed an accessible facility to run dynamic tests on propellers.
When we kicked off the design in April 2025, our starting point was:
1) An existing blower-type fan with fixed performance and size.
2) Some available space in the underground floor.
That was it. With these two constraints, the requirement was to build a wind tunnel
capable of testing the largest possible propeller diameters at the highest possible speeds!
The fan design forced us to place it at the tunnel’s inlet, while the room layout dictated an open-circuit configuration.
To achieve the best possible flow quality in the working section—meaning minimal turbulence and angularity—we needed a contraction section with the highest feasible area ratio. That, in turn, required a wide-angle diffuser to make the contraction fit within our limited space.
Step by step, the tunnel’s shape and size naturally emerged from these constraints.
What’s ready now:
- Overall design and structural plans
- CFD analysis of the tunnel and honeycomb
Next steps:
1) CFD analysis of the tunnel inside the room,
2) Purchase of pressure and velocity sensors,
3) Explore, improve, and manage the flow quality in the working section, and eventually
Test real propellers and enjoy the expansion of our design capabilities!
We started this project because we needed an accessible facility to run dynamic tests on propellers.
When we kicked off the design in April 2025, our starting point was:
1) An existing blower-type fan with fixed performance and size.
2) Some available space in the underground floor.
That was it. With these two constraints, the requirement was to build a wind tunnel
capable of testing the largest possible propeller diameters at the highest possible speeds!
The fan design forced us to place it at the tunnel’s inlet, while the room layout dictated an open-circuit configuration.
To achieve the best possible flow quality in the working section—meaning minimal turbulence and angularity—we needed a contraction section with the highest feasible area ratio. That, in turn, required a wide-angle diffuser to make the contraction fit within our limited space.
Step by step, the tunnel’s shape and size naturally emerged from these constraints.
What’s ready now:
- Overall design and structural plans
- CFD analysis of the tunnel and honeycomb
Next steps:
1) CFD analysis of the tunnel inside the room,
2) Purchase of pressure and velocity sensors,
3) Explore, improve, and manage the flow quality in the working section, and eventually
Test real propellers and enjoy the expansion of our design capabilities!
Construction process:
Our blower
The very first version of the tunnel
CADFlo CFD analysis:
Flow straightening and turbulence management
To ensure uniform flow in the working section, the tunnel is equipped with
four stainless steel screens and a honeycomb section.
- Screens (4 pcs): 1×1 mm mesh, 0.24 mm wire thickness — porosity 0.61
- Honeycomb: 19×19×150 mm cells, 0.45 mm strip thickness — porosity 0.93
This combination effectively reduces flow angularity and large-scale
turbulence before the contraction.
To ensure uniform flow in the working section, the tunnel is equipped with
four stainless steel screens and a honeycomb section.
- Screens (4 pcs): 1×1 mm mesh, 0.24 mm wire thickness — porosity 0.61
- Honeycomb: 19×19×150 mm cells, 0.45 mm strip thickness — porosity 0.93
This combination effectively reduces flow angularity and large-scale
turbulence before the contraction.
Flow straightening and turbulence
management
To ensure uniform flow in the working
section, the tunnel is equipped with four
stainless steel screens and a honeycomb
section.
- Screens (4 pcs): 1×1 mm mesh, 0.24 mm
wire thickness — porosity 0.61
- Honeycomb: 19×19×150 mm cells, 0.45 mm
strip thickness — porosity 0.93
This combination effectively reduces flow
angularity and large-scale
turbulence before the contraction.
management
To ensure uniform flow in the working
section, the tunnel is equipped with four
stainless steel screens and a honeycomb
section.
- Screens (4 pcs): 1×1 mm mesh, 0.24 mm
wire thickness — porosity 0.61
- Honeycomb: 19×19×150 mm cells, 0.45 mm
strip thickness — porosity 0.93
This combination effectively reduces flow
angularity and large-scale
turbulence before the contraction.
Suction type open circuit wind tunnel with fan array
We started this project in May 2026 to add more flexibility to the first wind tunnel design. Rather than using a blower, we turned to the suction type and an array of fans to naturally improve the flow quality (turbulence intensity and angularity) while keeping the tunnel affordable.
The requirements included:
1) The maximum tunnel length
2) The maximum cross-section size
3) The minimum working section size, and
4) The speed in the working section.
It was interesting to explore a wide range of speeds in the working section and track how the required power increases with speed.
We also ran the design and analysis for three cross-sectional shapes: round, square, and square with rounded corners. While the trends are obvious, it is helpful to estimate and compare the numbers.
The current state of the project:
exploring the design space and specifying the project requirements.
The requirements included:
1) The maximum tunnel length
2) The maximum cross-section size
3) The minimum working section size, and
4) The speed in the working section.
It was interesting to explore a wide range of speeds in the working section and track how the required power increases with speed.
We also ran the design and analysis for three cross-sectional shapes: round, square, and square with rounded corners. While the trends are obvious, it is helpful to estimate and compare the numbers.
The current state of the project:
exploring the design space and specifying the project requirements.
