Abstract
High frequency surface acoustic waves with MHz order are able to generate intense acoustic streaming flow transformed from the attenuation of acoustic radiation pressure in viscous fluid. We here demonstrate the fluid propulsion force onto the device of SAW chip as a reaction force based on the change of momentum flux of acoustic streaming flow. A pendulum force balancing method is established to simply quantify 40 MHz SAW propulsion force onto lithium niobate (LN) chip. Propulsion force with 5 mN can be easily generated by applying ∼1 W power to SAW device. A theoretical model, along with acoustic streaming profile via particle image velocimetry, is proposed to explain the propulsion force based on applied power and different fluid viscosity. Finally, we propose a model optimizing LN chip size to perform maximum propulsion force per unit device area. The maximum force of ∼ 10 mN/cm2 with 1 W power using 40 MHz SAW has been performed in water. With high-frequency, short attenuation length, relatively low applied power and large propulsion force per surface area, it shows great potential of SAW-induced thruster for underwater silent propulsion and transportation.
Highlights
Efficient underwater propulsion has long been essential to the operation of autonomous underwater vehicles (AUV) [1]
In spite of ample research on surface acoustic waves (SAW)-induced acoustic streaming reported in the literature over the years, the ability of acoustic streaming to produce a reaction force upon the device that is the source of the acoustic streaming has not been investigated in detail
The angle of deflection of this pendulum can be used to quantify the force generated by acoustic streaming from the SAW device
Summary
Efficient underwater propulsion has long been essential to the operation of autonomous underwater vehicles (AUV) [1]. As the size of submersibles decrease to the millimeter and smaller scales, electrical motors are all that remain to drive the propulsion mechanisms in submersibles, even though propellers are well-known to suffer from poor efficiency at such small scales, and produce torque steer that is difficult for a small craft to overcome [3]. Notwithstanding this issue, Li et al [4] recently demonstrated acoustic-induced propulsion by a lead zirconate titanate (PZT) piezoelectric element used to drive a propeller as an underwater piezoelectric thruster. Waterjet propulsion was briefly introduced in [2], regardless of scale
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