This paper presents an original concept of using a composite flexible flapping Vortex Generator mounted on a heat sink fin for air side heat transfer augmentation. The main aim is to combine the advantages of hard and soft winglets in a composite one for having the highest possible enhancement. The proposed composite Vortex Generator, which is made with a thin elastic sheet is responsible for enhancing heat transfer and mixing quality performances in laminar convection air flow in a heat sink. The merged vortical structures due to oscillation by winglet swept out the thermal boundary layer and enhance thermal mixing between the fluid near the heated fin and the channel core flow. This novel concept is demonstrated using numerical simulation of the flow field with considering a two-way strongly coupled fluid-solid interaction approach in transient condition. The set of governing equations including, the continuity, momentum, and energy for a 2-D forced convection air flow are solved by the finite element method using the COMSOL Multi-Physics. The present findings show 148%, 116%, and 121% increases in the cooling rate by the composite and the two hard and soft homogeneous winglets, respectively. Numerical results are validated against the numerical data reported in the literature.

A Vortex-bladeless turbine is a device that works with Vortex-induced vibration, which is generated by wind energy. It is one of the innovative devices for wind energy harvesting with some remarkable advantages compared to classical turbines. Such wind turbines have numerous advantages, including less maintenance than classical windmills, lower manufacturing costs, and easier installation. Vortex's nobility comes from its spectacular form of harvesting energy by vibration. The mast vibrates in the wind, with lift force made with Von-Karman vortices when a moving air cross-passes over a mast (with a mean diameter of the mast D) structure. At the lower part of the mast, an elastic rod (carbon fiber) moves an alternator and harvests electricity with the least parts in contact. To optimize this technology for harvesting the potential energy, one of the critical parameters is the mean diameter D, which is analytically studied to have the largest displacement amplitude at the tip of the mast. To this end, the bladeless Generator is simulated as a one-degree-of-freedom system moving transverse with the flow direction. The mass-damping parameter (m*ζ), which depends on a mast and core fabric, is investigated. Air forces are extracted from experimental experiences, and fabrics are determined at the design stage according to references (carbon fiber for the core and carbon glass for the mast). The velocity of the air is determined according to where the bladeless Generator will be installed. In the end, the results are verified by CFD methods in fluent software. ICEM software is used for meshing the 2-dimensional model. The Piso algorithm and kω-sst model are applied to model the airflow to solve the problem.

Experiments were carried out for the numerical investigation of heat transfer enhancement in a solar air collector using different types of baffles and Vortex Generators. In this study, the Vortex Generator was implemented to increase the efficiency of the solar air collector. The variations in Nusselt number, pressure drop, friction coefficient, and thermal and exergy efficiency in four collectors with different baffles arrangement (type A, B, C, D) were investigated. Type A was chosen as the optimum collector for implementing the Vortex Generator on the absorber surface. In the solar air collector the effects of using a novel Vortex Generator-the Perforated Delta Wing Vortex Generator (PDWVG), in comparison with a flat one-the Flat Delta Wing Vortex Generator (FDWVG), were considered. In order to determine the maximum efficiency of the solar air collector, four different pitch ratios of Vortex Generators were studied. The Nusselt number and pressure drop increased with the Reynolds number but the friction coefficient decreased with Reynolds, the experimental and numerical results revealed that the thermal and exergy efficiency decreased from a specific range. The comparison of PDWVG and FDWVG showed that the presence of holes on the novel Vortex Generator led to reduced pressure drop and increased heat transfer between the airflow and the absorber surface. Increasing the number of Vortex Generator rows had a slight effect on increasing the studied parameters. The results showed that collector type A with ep=0. 55 of PDWVG improves the energy and exergy efficiency 4. 43% and 5. 29% respectively.

Vortex rings can maintain their structure during motion and achieve long-distance transport with low energy consumption, which is a fluid transport method with great energy-saving potential. In this paper, a reciprocating Vortex ring Generator structure is designed, which can generate two Vortex rings during the reciprocating motion of one piston, making full use of the thrust in the reciprocating motion period of the piston and improving the Vortex ring generation frequency compared with traditional Vortex ring Generators. For the characteristics of long-distance transport of Vortex rings, an experimental platform is designed and built, and 277 sets of experiments are carried out with different geometric parameters. The results show that the effect of generating two Vortex rings could be achieved under other parameter conditions, except for some parameter conditions where the diameter ratio D1/D2 = 4. By analyzing the influence of baffle width ratio, length ratio, and diameter ratio on the moving distance of Vortex rings, the performance of the Vortex ring Generator is preliminarily studied. In 277 sets of experiments, the maximum moving distance ratio x1 of Vortex ring 1 is 13. 7 when L1/L2 = 2. 4, D1/D2 = 2, and w1 = 0. 2. And the maximum moving distance ratio x2 of Vortex ring 2 is 20 when L1/L2 = 2, D1/D2 = 2. 5, and w2 = 0. 2.

This article presents a comprehensive approach to enhance heat transfer rates in a 3D channel using Ferrofluids. The study investigates the individual and combined impacts of rectangular winglet Vortex Generators and magnetic fields on flow characteristics, heat transfer enhancement, and entropy generation. Numerical solutions are derived for the governing partial differential equations using the finite volume technique and the SIMPLE algorithm. The investigation assesses the influence of key parameters, including the type of rectangular winglet Vortex Generator (simple, concave, and convex), Reynolds number, and magnetic field strength. Optimal operational conditions are identified based on thermodynamics' first and second laws. This study has been conducted in three steps, and the interaction of created vortices and their effect on heat transfer, pressure drop, and entropy production were investigated. In the first step, the effect of the Vortex Generator in different Reynolds has been investigated. In the next step, the impact of applying a magnetic field at different intensities by a current-carrying wire has been studied in a channel without Vortex Generators. Finally, the application of Vortex Generators and magnetic fields has been investigated simultaneously. The results showed that using the concave Vortex Generator in the absence of a magnetic field increased the heat transfer by 50% and pressure drop by 60%. Applying a magnetic field in the channel without Vortex Generators has increased heat transfer and pressure drop by 70% and 118%, respectively. Moreover, it is observed that the magnetic field induces a greater pressure drop penalty than the Vortex Generator for achieving the same heat transfer augmentation. The simultaneous application of magnetic field and Vortex Generator has also increased the heat transfer and pressure drop by 200% and 269%, respectively, for simple Vortex Generators.

Flow separation is mostly an undesirable phenomenon and boundary layer control is an important technique for flow separation problems on airfoils and in diffusers. Longitudinal (streamwise) vortices are produced by the interaction between jets and a freestream. This technique is known as the Vortex Generator jet method of separation, or stall control. The Vortex Generator jet method is an active control technique that provides a time-varying control action to optimize performance under a wide range of flow conditions because the strength of longitudinal vortices can be adjusted by varying the jet speed. In the present study, an active separation control system using Vortex Generator jets with rectangular orifices has been developed. The active separation control system can be practically applied to the flow separation control of a two-dimensional diffuser. It was confirmed that the proposed active separation control system could adaptively suppress flow separation for the flow fields caused by some changes in freestream velocity and the divergence angle of the diffuser.

The compressor cascade performance is significantly restricted by the secondary flow mainly presented as the trailing edge separation and corner stall. This paper develops a synthetic flow control approach in a high turning cascade using the Vortex Generator and slot jet approach. Numerical simulations were conducted to assess the flow control benefits and illustrate the flow control mechanisms. Four configurations, the baseline, the two individual approaches and the synthetic approach, were simulated to compare the separation control effects. The simulations show that all the three configurations achieve considerable improvements of the cascade performance and the cascade sensitivity to incidence angle is greatly decreased. The synthetic approach improves the most among them which is almost the superposition of the two individual ones. In the synthetic approach, the trailing Vortex induced by the Vortex Generator suppresses the end wall cross flow and deflects the passage Vortex, and then prevents the production of corner stall; at the same time, the slot jet speeds up the trailing edge separation caused by the cascade high camber. Owing to the combination of the two aspects, the synthetic approach restricts the developments of secondary flow and vortices in the cascade, and improves the outflow uniformity. The synthetic approach nicely utilizes the advantages of the two individual approach while avoids the shortages by the complementation, so it can achieve more powerful flow control effects. At the end, vortices models are established to illustrate the secondary flow structure and the flow control mechanisms.