This paper deals with the optimization of a synthetic jet actuator parameters in the control flow around the NACA0015 airfoil at two angles of attack: 13° (i.e. the stall angle of NACA0015) and 16° (i.e. the post stall angle of NACA0015) to maximize the aerodynamic performance of the airfoil. Synthetic jet actuator is a zero mass flux-active flow control device that alternately injects and removes fluid through a small slot at the input movement frequency of a diaphragm. The movement of the diaphragm and also the external flow around the airfoil were simulated using numerical approach. The objective of the optimization process function was maximum lift-drag ratio (L/D) and the optimization variables were jet frequency, length of the jet slot and jet location along the chord. The power coefficient of the jet was considered as a constraint. The response surface optimization method was employed to achieve the optimal parameters. The results showed that the actuator is more effective for post stall angles of attack that can lead to an enhancement of 66% in L/D.

Density is one of the basic thermo-physical properties of a fluid that should be analysed before conducting performance analysis of the fluid. In the present study, the influence of design parameters on the density of nanofluids was investigated using response surface methodology (RSM). The quadratic model generated by RSM is used to predict the performance parameters, i.e. temperature and mass concentration with reasonably good accuracy. Improved empirical correlations were proposed based on the experimental data for density prediction of the metal oxide nanofluids. Experimentally measured densities of two different nanofluids at the nanoparticle mass fraction of up to 0.2% and the temperature range of 20°C-40°C were examined. The enhancement of densities compared to the density of base fluid at 20°C and 40°C, are about 0.217% for 0.2% fraction of ZnO nanoparticles. In addition, the densities of SiO₂ nanofluids are improved 0.117% compared to the density of distilled water. Finally the RSM outputs were compared with the results obtained from the experimental data. It was observed that the optimal RSM model is accurate and the absolute maximum deviations measured values from the predicted densities of ZnO and SiO₂ nanofluids are 0.008% and 0.014% respectively.