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We investigate the effects of aerodynamic loads on the performance of wing-based piezoaeroelastic energy harvesters. The rigid airfoil consists of pitch and plunge degrees of freedom supported by flexural and torsional springs with a piezoelectric coupling attached to the plunge degree of freedom. The effects of aerodynamic loads are investigated by considering a camber in the airfoil. A two-dimensional unsteady vortex-lattice method (UVLM) is used to model the unsteady aerodynamic loads. An iterative scheme based on Hamming’s fourth-order predictor–corrector method is employed to solve the governing equations simultaneously and interactively. The effects of varying the camber, its location, and the nonlinear torsional spring coefficient are determined. The results show that, for small values of the camber location, the flutter speed changes greatly on increasing the camber of the airfoil. On the other hand, for large values of the camber location, the variation of the flutter speed when changing the camber is very negligible. We demonstrate that the symmetric airfoil case is the best configuration to design enhanced wing-based piezoaeroelastic energy harvesters. Furthermore, the results show that an increase in the camber results in a decrease in the level of the harvested power. For cambered airfoils, we demonstrate that an increase in the camber location leads to an increase in the level of the harvested power. The results show that an increase in the airfoil camber delays the appearance of a secondary Hopf bifurcation.

Thermal performance of energy conversion systems is one of the most important goals to improve the system’s efficiency. Such thermal performance is strongly dependent on the thermophysical features of the applied fluids used in energy conversion systems. Thermal conductivity, specific heat in addition to dynamic viscosity are the properties that dramatically affect heat transfer characteristics. These features of hybrid nanofluids, as promising heat transfer fluids, are influenced by different constituents, including volume fraction, size of solid parts and temperature. In this article, the mentioned features of the nanofluids with hybrid nanostructures and the proposed models for these properties are reviewed. It is concluded that the increase in the volume fraction of solids causes improvement in thermal conductivity and dynamic viscosity, while the trend of variations in the specific heat depends on the base fluid. In addition, the increase in temperature increases the thermal conductivity while it decreases the dynamic viscosity. Moreover, as stated by the reviewed works, different approaches have applicability for modeling these properties with high accuracy, while intelligent algorithms, including artificial neural networks, are able to reach a higher precision compared with the correlations. In addition to the used method, some other factors, such as the model architecture, influence the reliability and exactness of the proposed models.

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We consider the problem of suppressing oscillations of an elastically mounted rigid cylinder undergoing vortex-induced vibrations by linear and nonlinear active velocity feedback controllers. Each controller relies on an actuator, which imparts an opposing force to the cylinder motion, thereby reducing its high-amplitude oscillations. A strongly coupled fluid–structure numerical model is used to solve the fluid–structure interaction equations. The results show that the choice of the active feedback controller depends on the allowable controlled amplitude of the cylinder. It is found that a cubic velocity feedback controller is more efficient than its linear velocity counterpart when very small controlled amplitudes are desired.