Mechanism of pressure recovery in jet-type actuators

Jet-type actuators generating synthetic jets became recently very important for control of flow past bodies. In contrast to mechanical pulsators usually used in them, a number of advantages especially for the hybrid-synthetic jet versions bring fluidic no-moving-part valves. The paper presents an example of such a valve used for flow separation control on a wing wind tunnel model. Usual fluidic valves have large and long collector diffusers, which cause problems with stowage inside the model but so far were considered necessary for the required pressure recovery. Somewhat surprisingly, this study demonstrates that a substantial amount of the pressure recovery actually takes place before the flow enters the diffuser. This is an important information for actuator designers, who – it seems – have so far concentrated their attention in valve development and improvement at a wrong part of the devices.