Cantilever beams with piezoelectric coating are the most widely used form of strain-driven energy harvesting. Almost all prior research on cantilever beam shapes aimed at enhancing energy output accounts for beams fully coated with piezoelectric materials. While a larger coating area, up to a certain limit, can enhance energy output, it also escalates the cost of the structure, as piezoelectric materials are very expensive. Output power density over the length of the beam/piezoelectric material varies significantly. Hence, a partially coated beam with an optimized positioning of piezoelectric material can not only cut the cost of the system but also warrant a higher output power density. On the other hand, optimizing the base beam shape always remains one of the top approaches to increasing the power output. As such, this work aims to select a cantilever beam design by investigating a wide variety of cantilever beam shapes while the beam is partially coated with the piezoelectric material to maximize the power output capacity of the harvester. In the first part of the study, an efficient size of the piezoelectric material and its placement in the host beam are selected based on the power capacity of the system. Next, the selected effective size and placement of the piezoelectric material is implemented in a wide range of cantilever beam shapes (e.g., trapezoidal, triangular, V-cut, concave, and convex) to select a host beam design for maximizing the output power density. To ascertain a comparable argument, the surface area, volume, and mass of all the considered beam shapes are kept consistent, as these parameters influence the power output of the harvester. The geometry of each shape is systematically varied to understand the effect of geometric configuration on the output power density. Additionally, an analysis is conducted to validate that the findings/selection of this study are independent of the thickness of the host beam or piezoelectric material.

Cantilever beams are the most widely used form of strain-driven energy harvesting, which uses piezoelectric materials. Although researchers are constantly seeking improved power output from cantilever-beam-driven piezoelectric energy harvesters, a systematic and fundamental analysis of the effect of beam geometry on the power capacity of energy harvesters warrants further investigation. Most of the previous research accounts for beams that are fully coated with piezoelectric material. While a larger coating area increases energy output, it also escalates costs as piezoelectric materials are very expensive. Considering the high cost of piezoelectric materials when dealing with limited piezoelectric material, enhancing power output can be achieved by employing a larger base beam and coating a portion of it at the fixed end. As such, the aim of this work is to investigate a wide variety of cantilever beam shapes (e.g., trapezoidal, triangular, V-cut, concave, and convex) with partial piezoelectric material coating on the base beam to maximize the power output capacity of the harvester. To ascertain a comparable argument, the surface area, volume, and mass of all the considered beam shapes are kept consistent, as these parameters influence the power output of the harvester. The geometry of each shape is systematically varied to understand the effect of geometric configuration on the output power density. Finally, the power capacities of all types of beams are compared, and a design is proposed to obtain the maximum power output. It was found that when the surface area of both the beam and piezoelectric material is kept constant and piezoelectric material is located at the fixed end, a trapezoidal beam with a smaller base width and larger free end width is the most efficient in generating power as long as the structural integrity is maintained. The finding is completely opposite as was suggested by previous studies, which proposed that a trapezoidal beam with a smaller free end yields higher output. Instead, this study demonstrates that an inverted trapezoidal beam produced higher output, considering partial coating compared to the full beam coating used in previous studies. Additionally, a correlation is presented on how the beam resonance frequency shifts with variation in beam parameters.

Achieving axisymmetric boundary conditions in turbulent swirl flows and predicting thermo-fluidic behaviours within a nozzle is often a challenge due to the difficulties of measurement diagnostics. Adding nanoparticles to ase fluids exacerbates the complexity because of the regeneration of effective properties of the fluid medium. As such, this study numerically investigates the flow and thermal characteristics for the effect of swirl and nanofluids of incompressible turbulent liquid jets. The results show that the axial and tangential velocity profiles for water-based nanofluids resemble to those for water in no-to-high swirl flows. The surface Nusselt number for strong swirl flow reduces with axial distances at isothermal wall condition, and the Nusselt number is strongly dependent on types of nanofluid for isoflux condition. Water-based nanofluids cause higher heat transfer compared to Dowtherm+Al₂O₃ and Syltherm800+ Al₂O₃. The average Nusselt number and the pressure drop are found to be the largest for 10% volume fraction. The increase of thermal-hydraulic performance factor for nanofluids after nozzle convergence is steeper for highly swirling flow than for non-swirling and medium swirling cases. A strong turbulent kinetic energy is observed immediately after the nozzle converging section for all nanofluid cases and Dowtherm+Al₂O₃ shows relatively uniform distributions across the nozzle.