Jet And Vortex Actuator Research Articles

Numerical investigation of a jet and vortex actuator in a cross flow boundary layer

The performance of a zero-net-mass-flux Jet and Vortex Actuator (JaVA) was numerically investigated in a two-dimensional-cross-flow flat-plate laminar boundary layer. The JaVA is an active flow control device that can be used for flow separation control and thus can delay/prevent boundary layer separation. In this study, an unsteady, incompressible flow solver has been used to study the flow fields generated by a JaVA in a water channel. Detailed quantitative information about the performance of the JaVA on a flat-plate boundary layer is obtained. JaVA-induced boundary-layer profiles are clearly ‘fuller’ at the wall and hence more resistant to flow separation. The ‘positive’ effects of the JaVA with different operating regimes on various boundary-layer flow characteristics such as displacement thickness, shape factor and the friction coefficient are presented in this study. Selecting the appropriate governing parameters in conjunction with cross-flow properties, the velocity profile can be tuned in a boundary layer to delay or prevent separation.

Active flow control applications with a jet and vortex actuator in a laminar cross flow

In this study the effect of an oscillatory, zero-net-mass flux device called a Jet and Vortex Actuator (JaVA) on the laminar boundary layer is investigated. The JaVA can be utilized to energize the boundary layer over a flat plate by creating jets and vortices thus it can delay or prevent boundary layer separation if it is used properly.It appears to produce qualitatively different flow regimes depending on its actuation parameters, e.g. frequency and amplitude or subtle changes in geometry such as the position of the actuator plate with respect to the JaVA-cavity. This latter effect was only discovered recently. Since little is known about the underlying fluid dynamics and because of a complete lack of unsteady data, a device is designed and built for experiments in water. Unsteady flow fields have been recorded for visualization and furthermore quantitative evaluation by means of Particle Image Velocimetry (PIV) has been carried out in addition to numerical simulations. Results show that the JaVA-induced vortices ejected into the flat plate boundary layer significantly enhance the velocity profiles and its characteristics such as the displacement thickness and the momentum thickness if the plate is oscillating at high frequencies as it is flush-mounted or inside the cavity. But if the plate is extracted out of the cavity then there is no improvement in the flow fields hence separation can be delayed or prevented for long downstream distances only if the actuation parameters and plate positions are selected properly.