In this blog post, we’ll take a step-by-step look at the structure and fluid dynamics principles that allow blade-less fans to generate a strong breeze, even though they appear to have no external rotating blades.
Why Were Blade-Less Fans Invented?
For families with children, traditional fans with blades are always a source of concern. Because there’s a risk that a child might stick their hand or an object into the fan blades and get hurt, parents often use products with protective covers or fine-mesh safety guards; however, these measures alone are not enough to provide complete peace of mind. For this reason, when “blade-less” designs—such as those from Dyson, where no rotating blades are visible on the outside—emerged, many consumers took an interest in this new approach to addressing safety concerns.
Basic Structure and Overall Operation Overview
The most striking features of a bladeless fan are the ring-shaped air channel at the top and the cylindrical base at the bottom. Inside the base are a motor and an intake fan, so no rotating blades are visible from the outside. This fan draws in ambient air and directs it into the channel inside the ring.
The air that travels along the inside of the ring is ejected at high speed through very narrow gaps. This high-speed airflow causes a phenomenon called “entrainment,” which draws in the surrounding air, while simultaneously altering the pressure distribution around the ring to encourage even more surrounding air to move along with it. As a result, the actual amount of wind felt by the user is much greater than the air directly drawn in by the fan inside the base.
Therefore, there are two key points to understanding this product. First, how air is drawn in through the base; and second, how the air rapidly expelled from the ring draws in surrounding air to create a larger airflow.
Air Intake: The Role of the Hidden Fan
Inside the cylindrical base is a fan that draws in air. As this fan rotates, it draws in surrounding air and directs it through passages inside the ring; the air is then expelled through narrow gaps at the ring’s edge. Although it appears to have no blades, a fan is actually present inside; strictly speaking, it is not “completely bladeless” but rather a design that conceals rotating blades within.
Bernoulli’s Principle and the Role of the Ring’s Cross-Section
The concept most frequently cited when explaining the operating principle of a bladeless fan is Bernoulli’s principle. Generally, as the velocity of a fluid increases, its static pressure tends to decrease, and as velocity decreases, static pressure tends to increase. This relationship is a fundamental principle of fluid dynamics often cited when explaining the lift generated by an airplane wing.
The ring cross-section of a bladeless fan is designed to be relatively flat on the outside and curved on the inside. This structure helps the air flowing inside the ring accelerate rapidly, and the high-speed airflow passing through the narrow gap alters the pressure distribution around the ring. At the same time, the ejected air causes an entrainment effect, pulling in the surrounding stationary air and further increasing the airflow.
In other words, the strong airflow of a bladeless fan cannot be explained by the Bernoulli principle alone; it is the result of the combined effects of entrainment caused by high-speed ejection, induced flow, and changes in pressure distribution. Thanks to these effects, the total airflow passing through the ring can be much greater than the volume of air directly moved by the fan inside the base.
Significance of the Design and Conclusion
To summarize, a bladeless fan draws air in through the fan inside the base, directs it into the ring, and ejects it at high speed through the narrow gaps at the ring’s edge. During this process, entrainment—which draws in surrounding air—and induced flow occur, creating an even greater airflow. In other words, the key lies in a design that does not simply push air outward but moves the surrounding air along with it.
This technology does not represent a new invention of fluid dynamics principles but rather an example of combining well-known principles with sophisticated mechanical design. It is significant in that it eliminates exposed rotating blades to enhance safety and delivers a user experience featuring a smoother, more uniform breeze.
