Presence Of Vortex Generators Research Articles

Influence of vortex generator on performance of concentrated solar photovoltaic module in existence of heat sink

New configuration of concentrated photovoltaic thermal (CPVT) with the implementation of parabolic concentrator and heat sink combined with the vortex generator (VG) were presented in current work. The testing fluid is water and temperature-dependent features were utilized. The regime of water flow in absence and presence of VG are laminar and turbulent, respectively. Numerical simulations were done for different values of angle of VG (θ = 30°, and 60°), pitch ratio (S = 0.025, 0.0375, and 0.05), and volumetric flow rate (Q = 0.5, to 2 Lit/min). Four values for width of reflector have been applied and radiation model was utilized to derive the absorbed heat flux. The accuracy of modeling has been examined for three cases and good accommodations have been reported. The maximum values of thermal (ηth) and electrical (ηel) performance are 63.75 % and 13.96 % which happens when θ = 30°, S = 0.025, Q = 2 Lit/min. Installing VG leads to increments of ηth and ηel about 1.42 % and 2.74 %. Increase of S and θ cause performance to decrease while this function increases with rise of Q. Increase of Q causes ηth and ηel to increase about 1.17 % and 2.55 % for the best case.

Numerical investigation of aerodynamic performance of an axial fan blade equipped with vortex generators

Delay in the onset of static stall via passive vortex generators (VGs) results in more efficient equipment. Nevertheless, most studies of VGs are conducted on wind turbine blades rather than other turbomachinery devices like axial fan blades. This study is feasibility research to see whether the aerodynamic performance of axial fan blades improves in the presence of VGs. Therefore, the VGs' effect of a static blade with an elliptical profile having a maximum thickness of 8% chord length and without a twist angle is investigated. Fully resolved RANS (Reynolds-averaged Navier–Stokes) simulation with the shear stress transport k–ω turbulence model at Re = 1 × 105 is used to discover the blade flow characteristics with VGs for two types of fan, eight and twelve blades. It is shown that, in both fans, not only can implementing VGs improve the aerodynamic performance of the blade effectively but also the separation phenomenon is delayed. Furthermore, it is concluded that installing VGs performed better in the 8-blade fan, with up to a 3° separation delay, a 9.88% increase in the maximum lift coefficient, and a 48.15% decrease in the maximum drag coefficient with respect to the clean blade. Analyzing the aerodynamic performance of real axial fans considering rotary blades with twist angles equipped with VGs will be feasible in future research.

Numerical simulation of a separated flow in a ribbed channel by the RANS and LES methods

The results of numerical simulation of a turbulent flow in a flat channel in the presence of vortex generators in the form of periodic solid ribs by the RANS and LES method are presented. The Reynolds number calculated by the rib height and the average flow rate is Re = 12600. The influence of the distance between the ribs on the flow structure is investigated. The boundaries of different types of roughness and their influence on the heat transfer intensity are shown.

RETRACTED: Laminar single‐phase and two‐phase modeling of water/MgO nanofluid flow inside a rectangular microchannel with rhombic vortex generators

AbstractIn the present numerical simulation, laminar single‐phase and two‐phase nanofluid flows are investigated inside a rectangular microchannel with the vortex generators. Rhombic vortex generators with different attack angles are used for a better mixture of fluid. Water/MgO nanofluid is used as the working fluid in the volume fractions of nanoparticles φ = 0‐4% in Reynolds numbers of Re = 1‐300 at the two‐dimensional space. The presence of vortex generators with attack angles of λ = 0‐45°, and simultaneous investigation of heat transfer and flow hydrodynamic parameters distinguish this research from other similar studies. Obtained results revealed that using nanofluid with higher volume fractions, slip boundary condition on the hot wall, and using vortex generator with higher λ lead to significant enhancement of heat transfer. Also, the value of pressure drop augmentation is caused by the increase of φ and λ is significant at higher Reynolds numbers. Unlike the increase of φ, by increasing Reynolds number, the effect of slip boundary condition becomes considerable on the reduction of entropy generation. The behavior of entropy generation graphs with slip velocity boundary condition on the wall is different from the no‐slip boundary condition at Re = 300. The behavior of average entropy generation is different in the various φ, Reynolds numbers, and λ in the no‐slip boundary condition for single‐phase and two‐phase models. Also, the two‐phase model estimates flow behavior with less irreversibility.

Computational Flow Prediction and Design Optimization of Vortex Generators for a Conventional Passenger Car

Vehicle aerodynamics is a vital physics in the design of an automotive vehicle. The main purpose of the automotive aerodynamics is to reduce drag force, wind noise, minimizing noise emission and preventing the undesired lift forces to avoid aerodynamic instability at high speeds. The shape of the vehicle body is to be designed in such a way that drag force caused by the pressure and viscous effects is less. The present analysis focuses on the drag reduction technique used for a passenger car \ using vortex generator. The main purpose of using Vortex Generators (VGs) is to disturb the airflow running over the car body and hence to produce a swirl of air in-between the high energy and low energy streams. In this paper, different shapes of vortex generators are considered and numerically investigated using Computational Fluid Dynamics (CFD). The flow characteristics around the car body with and without vortex generators are predicted and compared. The drag forces obtained using CFD simulations are compared with various vortex generator configurations. The present analysis also investigates the combined effect of spoiler with vortex generators and the change in aerodynamic characteristics of the car body is presented. The flow interference over the spoiler due to the presence of vortex generators is predicted to compare the changes in negative lift produced during high speeds. From the CFD analysis it is observed that there is less co-efficient of drag in ramped type VGs in comparison with other VGs.

Влияние вдува малоразмерных струй различных конфигураций на структуру и акустическое излучение сверхзвуковой струи

The work is devoted to experimental study of the structure and acoustic radiation of a supersonic underexpanded jet Ma = 1, Npr = 5 with the presence of vortexgenerators in the form of small-sized jets injections. Ten different configurations were tested, in which following the gas-dynamic and geometrical parameters of the microjets were changed one by one: microjets pressure, the injection distance from the main nozzle section, azimuthal, tangential, and axial angles of micronozzles inclination. The flow visualization, azimuthal Pitot pressure profiles and characteristics of jet noise in the far field were obtained. It has been revealed that the injection of microjets in general leads to an increase in the jet long-range and a decrease in its mixing. The advantageous parameters of the microjets injection for reducing the jet acoustic emission are the injection point vicinity to the main nozzle section, micronozzles inclination to main jet axis and the small tangential angle of micronozzles. The micronozzles quantity effect is non-linearly in relation to the structure and the jet noise. The average pressure measuring distribution near artificial longitudinal vortices in a jet stream cannot predict the characteristics of its mixing and acoustic radiation.

Influence of vortex generator on cylindrical protrusion aerodynamics at various Mach numbers

Effects of vortex generator on the flow field around vertically wall mounted cylindrical protrusion were carried out computationally at different Mach numbers. The flow field around cylindrical protrusion of three different heights with a ramp type vortex generator is analyzed. Three dimensional steady implicit formulation with standard k-ω turbulence model is used. Results obtained through present computation are validated with the existing experimental results at Mach 2.0. Good agreement between computation and experimental result has been achieved. Present result indicates that the presence of vortex generator will alter the flow field around cylindrical protrusion. It is observed that the vortex generator can also help in reduction of aerodynamic drag acting on cylindrical protrusion at various Mach numbers.

Numerical and experimental investigations of shape and location of vortex generators on fluid flow and heat transfer in a constant heat-fluxed rectangular duct

A numerical and experimental study was conducted for heat transfer enhancement and fluid flow in a constant heat-fluxed rectangular wooden duct fitted with two shapes of vortex generators (circular and square). These vortex generators are of the same area and placed at two different locations ([Formula: see text] and [Formula: see text]) ahead of the heater set and for Reynolds number from 32,000 to 83,000. The numerical and experimental results show an enhancement of heat transfer with the presence of vortex generators. This enhancement depends on the shape and location. Also, the numerical results show saving of 27% of the heater power with the presence of vortex generator. The experimental results of temperature distribution, Nusselt number distribution, effectiveness distribution, and pressure drop values of flow over heaters with vortex generators were reported and compared with the flow over heaters without vortex generators. The results show that heat transfer was enhanced by 2.186%−3.75% using circular type, and it enhanced by 1.3%−1.94% using square type. Also, pressure drop at the outlet of the duct increases by 166.7%−400% when using circular vortex generators and increases by 133.3%−300% when using square vortex generators. These values were obtained for the velocity ranging between 4 and 10 m/s and when vortex generators were placed at location [Formula: see text]. Finally, correlation equations for Nusselt number were obtained at location [Formula: see text] ahead of the heater set.

Mixed convective heat transfer from vertical fin array in the presence of vortex generator

Vortex induced non-Boussinesq laminar mixed convective heat transfer in a shrouded vertical non-isothermal fin array has been investigated numerically taking into account the variable transport properties. Computations are performed for the parametric range: Grashof number=4.3–8.4×105, Reynolds number=1280–2667, dimensionless fin spacing=0.2–0.5 and dimensionless clearance=0.0–0.25. Computations demonstrate inclusion of vortex generator results in a rise of pressure drop across the duct length to a value as high as 150% which is compensated by the substantial enhancement in heat transfer, as high as 200% locally and 20% globally compared to without vortex generator. Finally, overall Nusselt number is well correlated with the governing parameters of the problem.

Effect of Vortex Generators and Integral Splitter Plate on Heat Transfer and Pressure Drop for Laminar Flow Past Channel-Confined Tube Banks

Three-dimensional numerical computations are carried out to study heat transfer and pressure drop characteristics for laminar flow past circular tube banks in staggered and in-line arrangement confined within a narrow rectangular channel. A finite-volume based computational code has been developed for the computations. Vortex generators mounted near the upstream tube promote fluid mixing and enhance heat transfer in stagnant wake zone behind the tubes but offer extra pressure drop penalty. A splitter plate attached to the rear of the upstream circular tube acts as an extended heated surface and is expected to reduce the extra pressure drop due to vortex generators. The objective of this study is to find the configuration of tube arrangement in the presence of vortex generators and splitter plate that would be associated with enhanced heat transfer and reduced pressure drop. Heat transfer and pressure drop characteristics are presented for different lengths of the splitter plate in the absence and presence of vortex generators for both in-line and staggered arrangement of circular tubes.

Numerical Study of Flow and Heat Transfer for Flow Past Inline Circular Tubes Built in a Rectangular Channel in the Presence of Vortex Generators

A three-dimensional numerical study has been carried out for laminar flow of air past an inline arrangement of circular tubes built-in with a rectangular channel in the presence of vortex generators. The governing equations of momentum and energy are solved with the help of a developed computational code based on finite-volume technique. Computed flow and temperature field results are analyzed with an aim to find an optimum location of vortex generators resulting in the maximum enhancement of heat transfer causing a minimum increase in pressure drop. To find the optimized location of vortex generators, the effect of variation of the Reynolds number on flow and heat transfer has also been studied.

Flow visualization of annular and delta winlet vortex generators in fin-and-tube heat exchanger application

This study presents flow visualization and frictional results of enlarged fin-and-tube heat exchangers with and without the presence of vortex generators. Two types of vortex generators and a plain fin geometry were examined in this study. For plain fin geometry at Re=500, the horseshoe vortex generated by the tube row is not so pronounced, and the horseshoe vortex separates into two streams as it flows across the second row and consequently loses its vortical strength. This phenomenon may supports the “maximum phenomenon” in low Reynolds number region reported by previous studies. With the presence of annular vortex generator, the presence of a pair of longitudinal vortices formed behind the tube is seen. The strength of the counter-rotating vortices increases with the annular height and the strength of the longitudinal vortices is so strong that may swirl with the horseshoe vortices and other flow stream. For the same winlet height, the delta winlet shows more intensely vortical motion and flow unsteadiness than those of annular winlet. This eventually leads to a better mixing phenomenon. However, it is interesting to know that the corresponding pressure drops of the delta winlet are lower than those of annular winlet. Compared to the plain fin geometry, the penalty of additional pressure drops of the proposed vortex generators is relatively insensitive to change of Reynolds number.