Flow-vis paint (Flowfish)

Alex Albon, Scuderia Toro Rosso STR14 with aero paint during the Barcelona February testing at Circuit de Barcelona-Catalunya on February 19, 2019 in Circuit de Barcelona-Catalunya, Spain. (Photo by Jerry Andre / Sutton Images)

Flow-vis paint, sometimes called Flowfish in the paddock and formally known as flow visualisation paint, is the bright fluorescent liquid Formula 1 teams spray onto the bodywork of a car to see exactly how the air moves over it. It has become the single most important on-track diagnostic tool of the modern aerodynamic era, particularly since the FIA cut wind-tunnel time and mandatory CFD budgets forced teams to spend fewer hours in the tunnel and more hours on the real track.

What is flow-vis paint in F1?

Flow-vis is a mixture of fluorescent powder and a light oil (typically paraffin) suspended so it can be sprayed onto a car through a normal spray gun. When the car runs at speed, the airflow drags the wet paint across the bodywork in the direction the streamlines are actually going. As the oil evaporates, the fluorescent particles are left behind as visible tracks, and engineers can photograph those tracks and match them against the CFD prediction.

How teams apply flow-vis

• the car is prepared with clean bodywork ahead of a designated aero run;
• flow-vis is applied at multiple locations at once, most often the front wing, front-floor edge, sidepod inlet, diffuser strakes and rear wing;
• the driver completes a lap at target speed, usually with specific corner and straight profiles;
• the paint dries on track and the flow tracks freeze onto the bodywork;
• engineers photograph the pattern in the pit lane, sometimes with UV lighting to make the fluorescence pop;
• results are compared with wind tunnel and CFD simulations to validate the model or spot separation issues.

Why flow-vis matters more since 2022

The 2022 ground-effect regulations moved most of an F1 car's downforce to the underfloor Venturi tunnels, and airflow attachment on those surfaces became far more sensitive to ride height and yaw than the old wing-led cars. Flow-vis is the only practical way to see whether the flow really is behaving on the real car the way the wind tunnel promised, especially in transitions between straight-line and high-speed cornering. Teams like Mercedes and Ferrari, both of whom struggled with wind-tunnel correlation in 2022 and 2023, spent considerable Friday practice time in that period running flow-vis after every notable set-up change.

Frequently asked questions about flow-vis paint

What is flow-vis paint in Formula 1?

Flow-vis is a fluorescent oil-based liquid sprayed on F1 bodywork to visualise how air flows over the car. When the paint dries on track it leaves streaks that show the true airflow direction, which engineers compare against CFD and wind-tunnel predictions.

Why is flow-vis paint yellow or green?

The fluorescent pigments are chosen for maximum contrast against typical carbon-fibre bodywork under natural or UV light. Yellow-green is the most common because it shows clearly in high-resolution photographs.

When do teams use flow-vis?

Mostly during pre-season testing and Friday free-practice sessions at race weekends. It is quickest to apply between short runs, and the data it produces is often decisive for validating a new floor, wing or sidepod.

Is flow-vis paint used in the wind tunnel too?

Yes. Wind tunnels use similar visualisation techniques on scale models, though the paint recipe is different because tunnel Reynolds numbers are lower than track conditions.

Why is flow-vis more important since 2022?

Because ground-effect floors are highly sensitive to ride height and yaw, and wind-tunnel correlation problems became visible for the first time on several 2022 cars. Flow-vis on the real car is the fastest way to spot where the tunnel and reality disagree.