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The wingtip device plays an important role in increasing the range of UAVs because the winglets can effectively reduce the induced drag. The purpose of this paper is to explore the influence of wingtip device parameters on the lift-to-drag ratio of UAVs. Using the Fluent analysis system, the drag reduction performance of the winglet-winglet structure based on a UAV was analyzed at different angles of attack. Firstly, from the perspective of aerodynamic performance, the optimal cant and sweep angles of the blended winglets were selected by simulations. Then, the best-blended winglet and the blended split were simulated and analyzed, and the difference between the two on the lift-to-drag ratio and the flow field around the wing were compared. Compared with the traditional wind tunnel test, the CFD technology used greatly shortens the research cost and experimental cycle and provides help for the design of the UAV wingtip work.

The upper surface of the wing is constantly observed by experts on the wing. In this area, a variety of phenomena cause how much aerodynamic performance is demonstrated. Changing or adding geometry to the wing changes the flow characteristics of the upper surface. The use of winglets will certainly change the flow characteristics around the wingtip which will have a large effect on the area behind and next to the winglet itself. This research was carried out using Ansys 19.1 and the turbulent k-ω SST model. The airfoil used is Eppler 562 which is commonly used in unmanned aerial vehicles. Freestream flow velocity that will be used is 10 m/s (Re = 2.34 x 104) with an angle of attack (α) = 12° and 15°. From this study, it was found that the pressure contour in the y-z plane showed a reduction in area and intensity through the use of winglets. Secondary flow formed by using the forward wingtip fence results in a smaller area around the wingtip area than other configurations. Besides, the value of pressure on the upper surface which is equipped with a forward wingtip fence shows that pressure is still quite high when compared to the others.

The tip vortices shed by two marine propellers are studied, relying on large-eddy simulation, using a cylindrical grid consisting of 5 billion points. A tip-loaded design, featuring winglets at the tips of its blades, is compared against a conventional one at the design advance coefficient and a model-scale Reynolds number equal to 432 000. The tip-loaded propeller achieves improved performance, but produces also more intense tip vortices. The propeller with winglets actually generates two vortices from the tip of each blade, originating at the edge of each winglet and at the junction between the winglets and the blades. They merge at a short distance downstream, within a diameter from the propeller plane. The helical vortices originating from this merging process experience a slower instability, in comparison with the tip vortices in the wake of the conventional propeller, persisting further downstream, due to the weaker shear with the wakes shed by the following blades. The results of the simulations highlight that splitting the single tip vortex of a conventional propeller into two smaller vortices by means of winglets does not imply necessarily the generation of weaker vortices and lower negative peaks of pressure at their core: the geometry of the winglets needs to be carefully optimized to achieve this target.

This study investigates the potential of adaptive winglets with variable twist angles to improve the aerodynamic and energy performance of the Bombardier CRJ700. CFD simulations conducted in Star-CCM+, validated with a level-D flight simulator at LARCASE, reveal that twist adaptation can significantly reduce drag. A trajectory-based performance analysis shows that, during climb, adaptive winglets can reduce fuel consumption and climb time by up to 1.24% and 1.82%, respectively, or an increase of the ground distance by up to 2.67%. In cruise, fuel savings reach up to 0.4%. These results highlight the effectiveness of adaptive winglets in enhancing regional jet efficiency.

The effects of winglet offset distance, winglet coverage, and winglet cross section on the over-tip leakage loss for the plane tip have been investigated experimentally in a turbine blade cascade for a tip gap height-to-span ratio of h / s = 1.36 %. The results show that the over-tip leakage loss for the full coverage winglet increases steeply with increasing the winglet offset distance. This loss generation is attributed to flow disturbances over the forward-facing and backward-facing steps within the tip gap. The winglet flush mounted to the tip surface provides the best result. With the leading edge winglet portion or without it, the both-side winglet always provides better aerodynamic performance than the corresponding pressure-side winglet or suction-side winglet. Longer coverage of the both-side winglet leads to lower loss. Therefore, the full coverage winglet performs best in the loss reduction for the plane tip. In general, thinner winglet leads to better aerodynamic result, and the winglet cross section having a slant bottom surface with the smallest thickness at its outer end is recommended.

In this study, the thermohydraulic performance of rectangular‐winglet vortex generators (VGs) with different hole configurations (a central hole, dual‐edge holes, a leading‐edge hole, and a trailing‐edge hole) was numerically investigated. In addition, airflows through solar air heater ducts enhanced with these VGs were simulated using the realizable k‐epsilon model with a wall function at Reynolds numbers (Re) from 3000 to 20,000 and a Prandtl number ( P r ) of 7.070. A constant blockage ratio, defined as the ratio of the VG surface area to the cross‐sectional area of the airflow duct, was maintained. Overall, the results showed that the VG with a trailing‐edge hole achieved the highest thermal enhancement factor (TEF), ranging from 1.394 to 1.600. The central‐hole VG exhibited slightly lower TEF, between 1.424 and 1.578. In contrast, the dual‐edge‐hole and leading‐edge‐hole VGs produced lower TEFs, ranging from 1.301 to 1.541 and 1.282 to 1.567, respectively. Several temperature distribution plots, velocity plots, and pathline plots were utilized to investigate the cause of the performance differences. These visualizations ultimately revealed that the observed variations in thermohydraulic performance were attributed to distinct flow structures induced by the different hole configurations and Re values. In light of these findings, it can be concluded that the trailing‐edge‐hole VG is the most preferred option, while the central‐hole VG serves as a viable alternative, offering nearly equivalent performance. In contrast, the leading‐edge‐hole and dual‐edge‐hole VGs are less efficient and not recommended.

The efficient use of renewable energy sources becomes necessary due to rise in energy demand and dwindling traditional energy sources. In present work, solar water heating system (SWHS) is modified to improve its thermohydraulic performance. The absorber tube of the SWHS is modified by inserting the delta-shaped winglets (DSW) of different configurations inside it. Following variations of DSW geometrical parameters are considered in this study: pitch ratio ( P Rd ) from 0.5 to 2.0, blockage ratio ( B Rd ) from 0.1 to 0.25, attack angle ( α ) from 15˚ to 60˚, spacer length S w from 0 to 600 mm and Reynolds number from 200 to 1800. The results of the experiments reveal that out of considered geometrical parameters, DSW of geometrical parameters; P Rd of 0.5, B Rd of 0.2, α of 45˚and S w of 0 mm affect Nusselt number ( Nu ) and friction factor ( f ) optimally. The empirical correlations for Nu , f and thermohydraulic performance ( η w ) are developed from experimental values. Modelling for predictions of Nu , f and η w using artificial neural networks (ANNs) is also executed. The values of Nu and f obtained experimentally and from developed correlation are within bias errors of 10.9% for Nu and 9.5% for f , respectively. Novel aspects of this research include the utilisation of DSW hindrance promoters in the absorber tube for performance enhancement, development of empirical correlations, and predictions of outcomes using artificial neural networks. Correlation generation and modelling using the ANNs technique are essential aspects of this study that help to optimise the design parameters of similar type of SWHS.

Blade design is a fundamental and critical aspect of wind turbine technology. Enhancing the aerodynamic performance of turbine blades remains a key research focus in the field of wind energy. This project, based on the current state of wind power technology in Europe, compares and analyses three different types of horizontal-axis wind turbine blades, with particular emphasis on the function and performance of winglets (or sharklets) installed at the blade tips. The findings indicate that both tapered swept-back blades and elliptical blades can significantly improve the lift-to-drag ratio. Furthermore, incorporating winglets at the blade tips helps to mitigate wingtip vortices, thereby reducing induced drag. Overall, tapered swept-back blades are better suited for widespread commercial application, offering comparable aerodynamic performance to elliptical blades while allowing for a simpler manufacturing process.

The paper outlines an algorithm for the rapid aerodynamic evaluation of winglet geometries using the TORNADO Vortex Lattice Method. It is a very useful tool to obtain a first approximation of the aerodynamic properties and for performing an optimization of the geometry design. The TORNADO tool is used to systematically calculate the aerodynamic characteristics of various wings with wingtip devices. The fast response of the aerodynamic models allows obtaining a set of results in a remarkably short time. Therefore, the development of an algorithm to generate wing geometries with great ease and complex shapes is of vital importance for the mentioned optimization process. The basic outline of the algorithm, the equations defining the wing geometries, and the results for unconventional wingtip devices, such as blended winglets and spiroid winglets, are presented. Finally, this algorithm allows designing a procedure to study the improvement of aerodynamic properties (lift, induced drag, and moment). Some examples are included to illustrate the capabilities of the algorithm.

The aerodynamic characteristics and flow field distribution of wind turbines with the addition of V-flat winglets and V-winglets are investigated to investigate the effects of power, blade surface pressure, and flow field distribution of wind turbines with different V-winglets at rated operating conditions. The results show that the installation of V-winglets at the blade tip can increase the total power of the wind turbine. The V-winglets have better aerodynamic performance, and the total power is 1.57% higher than that without the winglets at rated operating conditions. The presence of V-winglets increases the pressure difference on the blade tip surface, and the pressure difference on the blade tip surface is more significant for flat V-winglets than for V-winglets. The V-winglets weaken the intensity of the blade tip disturbance, which makes the blade tip vortex V-shaped airfoil reduce the intensity of leaf tip disturbance and makes the vortex nucleus position far away from the leaf tip area. This can reduce the adverse effect of the leaf tip vortex on the main body of the blade.