A new idea is presented in this paper for improving the performance of solar air heater (SAH) designed for space heating by employing a thin flexible guide Winglet. In addition to the role of Winglet in pushing the convective airflow toward the heated surface, it behaves as a vortex generator (VG) due to its vibration by fluid-solid interaction (FSI) that causes flow mixing and breaking thermal boundary layer. In flow simulation, the finite element method (FEM) is employed with considering a two-way strongly-coupled FSI approach at transient condition. Numerical solution of the governing equations, including the continuity, momentum and energy for convective flow and the equation of motion for VG are obtained by COMSOL multi-physics. The well-known  model is employed for computation of turbulent stress and heat flux. The present numerical results are validated against the most recent relevant literature. To provide a clear and deep understanding of the proposed concept, extensive comparisons are made between different test cases. Results reveal considerable performance enhancement of SAH with elastic guide Winglet compared with clean solar air heater (CSAH), such that 56% increase in the natural airflow rate and 9% decrease in the average absorber temperature is seen because of the flapping Winglet. But, the air outlet temperature decreases about 14% due to flapping VG.  This study aims to make the proposed SAH as an essential renewable thermal-solar system more efficient and attractive so that this improvement pushes the industrial society toward more sustainable infrastructure.

The study's goal is to create a radiator-like device with fixed rectangular duct Winglets that circulate glycerol/water fluids with varying concentrations of copper oxide Nanofluids for improved heat transfer and cooling performance under all working situations. Hot water enters the rectangular duct at one end, while the cooling working fluid enters at the other. The findings of the experiment are compared with the computational fluid dynamics model of rectangular duct-Winglets for glycerol/water, glycerol/water of 0.1, 0.2, 0.3, and O.4% weight of copper oxide Nanofluids working fluids at a flow rate of 0.1, 0.2, 0.4, and 0.3 liters per minute. The findings demonstrated that the magnetohydrodynamics effect, which is based on the radiation parameter, increased as the flow through a region's heat transfer, causing a higher temperature and pressure drop in the glycerol/water-0.3% weight Copper oxide Nanofluids at 0.3 L/min flow rate. The results of the experimental for glycerol/water with 0.3% wt Copper oxide Nanofluids at 0.3 L/min flow rate showed that the pressure and temperature drop at Reynolds number 5400 were 19.8 kPa and 9.8 °C with its relevant friction factor and Nusselt’s number 0.0113 and 12.97 respectively.

In this research, a low speed wind tunnel test has been carried out to investigate the effects of adding grid Winglet, its size and number of fingers on the flow pattern over the upper surface of a wing model and its aerodynamic coefficients. The investigation has been performed for different angles of attack ranging from -2 to 21 degrees and at a free stream velocity of 24.7 m/sec, corresponding to the Reynolds number of 101000. The model has a rectangular shape with an aspect ratio of 4.75. Wing section airfoil is NACA 23016. Flow visualization is performed using tuft over the upper surface of the wing and lift & drag coefficients are measured. The obtained results show that at low angles of attack (lower than 6 degree), adding the grid Winglet has no effect on the lift & drag coefficients. However, at higher angles of attack, its effect increases. Maximum amount of lift and minimum amount of drag is for the case that the grid Winglet has 4 fingers sorted from long to short.

In the era of rapid technological developments, the green aircraft and Winglets of airplanes play a crucial role in reducing fuel consumption and its ensuing pollution. In this regard, the novelty of this paper is to focus on investigating the effect of the different geometrical parameters of Winglets planforms on improving the aerodynamic performance of a wing with a supercritical airfoil (NACA 641412) at lower Reynolds numbers (take-off and landing phase). These investigations were conducted experimentally in a wind tunnel by force measurements through an external force balance. The aerodynamic coefficients of CL and CL/CD were obtained for the clean wing and nine various Winglet planforms at a wide range of angles of attack from-4° to 20° and Reynolds numbers from Re=0. 99×105 to Re=1. 98×105. Furthermore, to get better insight into the physics of the flow, the numerical simulation of specific cases was carried out. According to the force measurement and vorticity magnitude results, among single Winglets of W1, W2, W3, and W4, the W1 Winglet with vertical height and linear side showed a better performance in all Reynolds numbers with a maximum lift increment of 26%, also, the W7 Winglet planform represented the best performance as in double Winglets with a maximum lift-todrag ratio increment of 40%

The main objective of the current study is to investigate the vortex generator supporting , n-tube heat transfer surface equipped with inline elliptical tubes by performing numerical simulations governed by finite volume method. It also aims at minimizing air-side thermal resistance using rectangular Winglet pairs. Then, the thermo-fluid performance of the baseline model was evaluated for the circular and elliptical tube congurations. According to the , findings, while the former increased the heat transfer, the latter decreased the pressure drop. The effect of the span-and stream-wise separation of the split Winglet pair and attack angle on the heat transfer and pressure drop performance was also examined in detail, the results of which were presented in the forms of Nu, f, and. The optimum stream-and span-wise locations for the front and rear Winglet pairs were identified based on highest enhancement factor. It was also found that the optimum attack angle of the front and rear Winglet pairs was different for the maximum enhancement factor.

Micro Air Vehicles (MAVs) are increasingly being used for civil and military surveillance. As the surveillance requirements are increasing, improving the range of MAVs becomes imperative. The performance of MAVs can be improved if the induced drag due to wingtip vortices can be reduced. In the present study, we try to decrease the induced drag caused by the wingtip vortices, which makes up a major part of the total drag, by introducing a Winglet. A unique yet simple design, which has not yet been studied thoroughly, is explored. Inspiration is taken from the feather structures of birds to design the proposed Winglet. The performance of a fixed-wing MAV at a free stream velocity (U∞) of 20 m/s is studied. Multiple Winglet configurations are used to compare the results with the baseline wing. An incompressible, steady three-dimensional simulation is carried out using the k-ω SST turbulence model. The experimental studies carried out for the baseline wing matched well with those obtained from CFD. Since the numerical model is valid, only computational study is done for the modified wing. The stall angle of the baseline wing is around 26°. Numerical results show that when the proposed Winglet is used, the stall angle for the wing is increased to around 32°. The use of the Winglet did not produce a considerable advantage at the lower Angle of Attack (AOA), but at higher AOA, the lift coefficient (CL) was considerably higher. The overall drag coefficient (CD) was higher at lower AOA when the Winglet is used. But at AOAs greater than 5°, the CD reduced. Other effects of the Winglet are addressed in terms of improvement in Lift-to-Drag ratio (L/D) and reduction in vorticity. The effect of the location and number of the feathers was studied to come up with an optimum Winglet configuration. The experiments were carried for the wing with optimum Winglet configuration and the results agreed fairly with the numerical results.