Controlling fluid jet direction without excess electricity or moving parts

Many large-scale commercial and industrial airflow systems benefit from precise control of jet direction. However, doing so is difficult. Passive methods lack the ability to adjust the jets as needed, while active methods, such as flaps or fluidic actuators, contain moving parts or require continuous electricity input.

As an alternative, Shunsuke Hoshikawa and Satoshi Ogata combined plasma actuators with the Coanda effect — a phenomenon whereby fluid jets tend to attach to and follow curved surfaces — to create a low-power method of directing airflow.

Plasma actuators based on dielectric barrier discharge are a popular method of controlling airflow. When current is applied to the device, it ionizes nearby particles, generating an electric field that exerts a force on the surrounding air. This method does not require moving parts but needs continuous application of electricity to function.

In experiments with plasma actuators, the authors noticed an interesting phenomenon.

“During our experiments, we found that the jet remained deflected after the plasma actuator was switched off under certain conditions,” said Hoshikawa. “This observation motivated us to identify these conditions systematically.”

The authors paired their plasma actuator with a curved surface to take advantage of the Coanda effect. This pairing created a hysteresis effect that allowed them to toggle the jet direction — following or not following the curved surface — with minimal electrical input.

Their further tests showed that the most important parameters for jet direction control were the diameter and mounting angle of the Coanda surface and the nozzle throat height.

“Our next step will be to investigate how the flow induced by the plasma actuator affects the jet velocity distribution,” said Hoshikawa. “In particular, precise measurements of the near-wall velocity distribution will help clarify how local flow acceleration influences the classification based on dimensionless parameters. This will allow us to identify the plasma actuator operating conditions required to switch the jet direction and further reduce power consumption.”

Source: “Sustained jet direction control using a dielectric barrier discharge plasma actuator combined with the Coanda effect,” by Shunsuke Hoshikawa and Satoshi Ogata, Physics of Fluids (2026). The article can be accessed at https://doi.org/10.1063/5.0329229 .