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Piezoelectric wind-induced vibration energy harvesters (PWVEHs) offer a promising solution for powering wireless sensor networks by converting wind energy into electrical energy. While conventional PWVEHs rely on vortex-induced vibration (VIV) and galloping to work, little has been done to investigate the coupling mechanisms between VIV and galloping and their influences upon energy harvesting performances of flow-induced vibration (FIV). To address this, we propose 36 bluff bodies (BBs) with various frontbody and afterbody shape combinations and conduct FIV experiments in a wind tunnel. The voltage output of each BB is recorded and analyzed based on whether pure VIV, pure galloping vibration, or concurrent VIV-galloping vibrations are involved. Hysteresis analyses are performed for BBs exhibiting concurrent VIV-galloping vibrations. The energy harvesting performances of all BBs are compared to circular and square cross-section BBs, revealing a BB shape that achieved 23.18 % and 16. 57 % higher maximum output than circular and square BBs, respectively. Computational analysis is conducted to investigate the flow field behind the given BBs. These findings provide valuable insights for developing efficient energy harvesters utilizing VIV and galloping by optimizing the involved BBs. [ABSTRACT FROM AUTHOR]

This paper presents a compact motor (6 mm in diameter) with a single piezoelectric stack actuator and a frame structured stator, which works under the principle of natural inchworms. Preliminary motion analysis and dynamic modeling are conducted based on the assumption of structural rigidity. The prototype can generate output torque of about 279 nNm and speed up to 200 rpm with a power input of 60 Vpp at the frequency of 12.7 kHz. In addition, rotational concentricity of the motor is discussed via analyzing captured video of the operating motor. Compared with the previous prototype that is 17 mm in diameter, the simplicity of the motor structure provides an effective miniaturization solution, which is important to many applications such as medical instruments and consumer electronics. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of flow control with blowing and suction in the whole structure consisting of an aggressive S-shaped air intake accompanied by a downstream fan stage. The results show that the effect of blowing-suction flow control is neither the simple summation of the effects of a single blowing control and a suction control nor the simple differences between them. It is the best one among three flow control techniques studied in this paper. The approach to selecting the optimum flow control scheme via simulating the single air intake, and afterward performing the numerical simulation of whole passage, has a certain rationality. With the blowing-suction flow control, the maximum isentropic efficiency and maximum total pressure ratio of the fan stage increase by 2.70 and 3.13%, respectively. Moreover, the rotor of the fan stage has a significant effect in reducing circumferential distortions. Due to the influence of the rotating fan rotor, the low-energy region at the lower side of the cross sections decreases gradually when approaching the fan-stage inlet. The low-energy fluid always exists in several blade passages after it enters the fan stage. Using the blowing-suction flow control, the relative total pressure of fluid in these low-energy passages increases to an extent. Streamlines in the fan stator flow passages and on stator blades show that the blowing-suction flow control in the air intake can improve the fan stator flow pattern, reducing the flow separation in general. [ABSTRACT FROM AUTHOR]