When Dyson launched the Airwrap in 2018, the marketing focused on one claim: it curls hair using air, not extreme heat. The mechanism behind this was described simply as the "Coanda effect." Most coverage stopped there — a name without an explanation. This article provides the actual physics: what the Coanda effect is, why it causes hair to wrap around the barrel, and what the engineering constraints are that determine when it works and when it doesn't.
What Is the Coanda Effect?
The Coanda effect is a phenomenon in fluid dynamics first described by Romanian engineer Henri Coanda in the 1930s. It describes the tendency of a fluid jet (gas or liquid) to adhere to an adjacent curved surface rather than continuing in a straight line. The mechanism: when a high-velocity jet of fluid is directed tangentially along a curved surface, a low-pressure zone forms between the jet and the surface (via the Bernoulli principle — faster-moving fluid has lower pressure). This low-pressure zone draws the jet toward the surface. The jet then follows the curve, maintaining contact through a balance of centrifugal force (trying to continue in a straight line) and the low-pressure adhesion pulling it toward the surface.
Coanda first observed this effect with a stream of water from a spoon — the water clung to the spoon's curve rather than falling straight. Dyson's patent applies the same principle at microscale: high-velocity air from the barrel slot clings to the barrel surface, and hair is carried with it.
How Dyson Applies the Coanda Effect to Hair Styling
In the Airwrap, a high-velocity air jet is expelled through a thin annular gap at the base of the barrel. The air exits at high velocity (Dyson's V9 motor accelerates air to approximately 42 m/s within the handle). This high-velocity jet is directed tangentially to the barrel's curved surface. Via the Coanda effect, the jet adheres to the barrel surface and flows along it in a spiral path. As the jet spirals around the barrel, it creates a low-pressure zone between the barrel surface and the surrounding air. This low-pressure zone acts as a suction force that draws nearby objects — including individual hair strands — toward the barrel surface. Once a hair strand is drawn close enough, the spiral airflow wraps it around the barrel and holds it there during the styling cycle.
The Bernoulli Principle — The Physics Behind the Adhesion
The Bernoulli principle states that in a flowing fluid, an increase in velocity corresponds to a decrease in pressure. In the Airwrap's barrel: the high-velocity air jet creates a region of lower pressure adjacent to the barrel surface. The surrounding still air (at atmospheric pressure) pushes the jet — and anything entrained in it — toward the lower-pressure region at the barrel surface. Hair is effectively pushed onto the barrel by atmospheric pressure differential, not gripped mechanically.
42 m/s
Air velocity at the Dyson Airwrap barrel slot
Dyson engineering specifications
Why the Barrel Diameter Determines the Curl Type
The diameter of the barrel directly determines the radius of the curl produced. A smaller barrel (e.g., 30mm diameter) produces tighter curls — the hair wraps around a smaller circumference, creating a tighter hydrogen bond pattern as it cools. A larger barrel (e.g., 40mm) produces looser waves. This relationship follows simple geometry: curl radius ≈ barrel radius. Hair that is set on a 30mm barrel, cooled, and released will spring back to approximately a 35–45mm curl radius (some elasticity returns as the hydrogen bonds partially relax after removal from the barrel).
Why Temperature Still Matters — Even at 150°C
The Coanda effect handles the mechanical curl formation — the hair is physically wrapped around the barrel by airflow, not by heat. But heat is still necessary: hydrogen bonds in the hair (which define its shape) must be temporarily broken and reformed in the new curl configuration for the style to last. This requires sufficient thermal energy. At 150°C, the Airwrap provides enough thermal energy to break and reform hydrogen bonds without reaching the disulfide bond disruption threshold (~195–200°C). The result: the style holds (hydrogen bonds reset) without the protein damage of higher temperatures (disulfide bonds remain intact).
The Limitations — When Coanda Does Not Work Well
Very Thick or Coarse Hair
Very thick or coarse hair requires more wrapping force than the low-pressure differential can reliably provide. Thick hair has higher mass and stiffness, requiring more force to wrap. The Airwrap's airflow generates sufficient force for fine to medium hair in most conditions; very thick or resistant hair may require smaller sections and more passes.
Soaking Wet Hair
The Coanda mechanism works best at 80%+ dry. Very wet hair is too heavy and slick for the low-pressure adhesion to grip and wrap consistently. This is why Dyson recommends pre-drying before using the styling barrels.
Very Short Hair (Under ~15cm)
Insufficient length to wrap around the barrel and create a defined curl. The tool still dries and smooths effectively, but the Coanda curl mechanism requires minimum length to function.
The Patent and Its Implications
Dyson filed patent US9554636B2 in 2016 describing the Coanda-effect hair styling mechanism. As aspects of this patent have narrowed or expired, competitors (notably Shark) have developed their own Coanda-style implementations. These competitors achieve similar hair-wrapping results through slightly different air slot geometry and flow paths — the physics is the same, the specific implementation differs enough to avoid infringement.
Frequently Asked Questions
What is the Coanda effect in the Dyson Airwrap?
A fluid dynamics principle where high-velocity air adheres to a curved surface, creating a low-pressure zone that draws hair toward and around the barrel without mechanical clamps.
Does the Coanda effect really work for hair?
Yes — for fine to medium hair, the Coanda mechanism consistently wraps hair around the barrel and produces defined curls at temperatures significantly lower than conventional curling irons.
Why does the Dyson Airwrap not work well on thick hair?
Thick hair's higher mass and stiffness requires more wrapping force than the aerodynamic low-pressure differential can reliably supply without smaller sections.
Who invented the Coanda effect?
Romanian engineer Henri Coanda, who described the fluid adhesion phenomenon in the 1930s after observing that fluid jets cling to curved surfaces rather than continuing in straight lines.
Can any air styling tool use the Coanda effect?
Yes — Dyson's core Coanda patents have narrowed since 2022, allowing competitors like Shark to develop similar air-wrapping tools using Coanda-principle mechanisms.
