Design and test of synthetic jet actuator for propulsion

Abstract

Compact zero-mass pulsatile jet actuators are proposed for low speed maneuvering and station keeping of small, autonomous underwater vehicles. Hence, the optimization of synthetic jets for maximal thrust generation is being investigated. Flow field of such jets are initially dominated by vortex ring formation. Pinched-off vortices characterize the extremum impulse accumulated by the leading vortex ring in a vortex ring formation process. Relevant parameters in this process are identified to design simple and low cost zero-mass pulsatile jet actuators. Prototypes of the aforementioned actuators are built for propulsion and underwater maneuvering. The actuators could be utilized in two ways. Firstly, it can be used to improve the low speed maneuvering and station keeping capabilities of traditional propeller driven underwater vehicles. Secondly, it can also be used as a synthetic jet for flow control and drag reduction at higher cruising speeds. Also, pulsatile jets can be actuated through a variety of techniques. The two methods of such actuators include a mechanical plunger system, and a solenoid actuator. The actuators consist of a small cavity with an orifice on one side, whereas the other side has a moving diaphragm. The mechanical actuator is designed such that the orifice diameter and actuation frequency can be easily varied in order to find the optimal operation point of the actuator. Conversely, solenoid actuation shows an almost linear stroke dependency on the actuation frequency.