Assessment of flow energy harvesting in a duct by means of CFD numerical simulations

Abstract

Micro-energy harvesting devices are small-scale devices that convert ambient energy from the environment, such as light, heat, or mechanical vibrations, into electrical energy that can be used to power small electronic devices. These devices have gained increasing attention in recent years due to their potential to power autonomous microsystems, such as wireless sensors and implantable medical devices, without the need for external power sources or batteries. Micro-energy harvesting devices typically consist of a transducer that converts the ambient energy into electrical energy, a power management circuit that regulates and stores the electrical energy, and an output circuit that delivers the energy to the load. Various types of transducers have been developed, including photovoltaic cells, thermoelectric generators, and piezoelectric generators, each of which has its own advantages and limitations. The design and optimization of micro-energy harvesting devices involve many challenges, such as maximizing the energy conversion efficiency, minimizing the power losses, and ensur- ing the compatibility between the transducer and the load. Nonetheless, micro-energy harvesting devices offer a promising solution for powering low-power electronics in a sustainable and self- sufficient manner, and their development is expected to have a significant impact on a wide range of applications in the future. A miniature device, harvesting energy from the flow in a micro-channel that has been proposed and experimentally studied in the literature, is numerically studied herein. The device consists of two bluff bodies installed in the flow and a flexible diaphragm at the channel upper wall, above the bodies. Vortex shedding behind the bodies induces pressure fluctuation and causes vibration of the diaphragm; the latter is connected to a piezoelectric membrane converting mechanical energy to electrical. Although the device is easy to fabricate and install, its power output is low, justifying further research. This device has been numerically studied in the past in [21], where various bluff body shapes and configurations had been considered for a fixed inlet Reynolds number and con- clusions were drawn concerning the more effective configuration with respect to body geometry and diaphragm position. The above study is continued herein by further testing the CFD model for various grid sizes and assessing the device performance for various flow Reynolds numbers, and various blockage ratios. Additionally, the vortex shedding suppression in the device is studied, and the results are compared with the bibliography outcomes for the same device.