Effect Of Vortex Generators Research Articles

Tip vortex cavitation control by the micro vortex generator

The present study investigates the control effect of a vane-shaped micro vortex generator (VG) on the inception and development of tip vortex cavitation. Five different arrangements were tested by varying the position and installation angle near the tip of a NACA (National Advisory Committee for Aeronautics) 662-415 hydrofoil. The spatial and temporal evolution of the tip vortex cavity was captured using high-speed imaging. The result shows that VG can induce both streamwise vortices and bubbles that affect the cavitation inception. When the VGs are aligned parallel to the incoming flow direction, the generated bubble content is relatively small. Meanwhile, due to the interaction between the tip vortex and the streamwise vortex induced by the VG, the vortex cavity in these cases exhibits notable deformation and diameter fluctuations compared with the smooth case. As a result, the inception of cavitation is significantly delayed, resulting in a notable reduction in the sound pressure level. The optimal control is achieved when the VG is placed at the tip. Conversely, the VG mounted at a larger alignment angle generates bubbles at a high cavitation number, which causes the premature onset of vortex cavitation and results in a detrimental effect.

Cavitation erosion characteristics influenced by a microstructure at different scales

The scale effect of vortex generators, as microstructures, influences cavitation erosion remains unclear, posing a key challenge to applying vortex generators in large-scale hydraulic machinery. In this study, the vortex generators (VGs) with heights of 0.25 mm (micro-VG) and 2.5 mm (large-VG), installed at the leading edge of a smooth NACA0015 hydrofoil, were investigated through experimental and simulation methods. The results demonstrate that the vortex generators can induce tubular vortexes that enhance near-wall flow stability. After installing the VGs, the large-scale cloud cavitation is effectively controlled. On the hydrofoil with micro-VGs, this control manifests as localized, small-scale cavitation shedding and collapse, while on the hydrofoil with large-VGs, the cavitation shedding is entirely absent, which shows that larger VGs further mitigate cavitation effects. Pressure signal analysis reveals that the VGs alter the pressure fluctuation period and reduce the main frequency amplitude compared to that on the smooth hydrofoil, with larger VGs providing superior suppression of pressure fluctuations. Additionally, an improved strength function method is proposed and applied, highlighting that the reduction in large-scale cloud cavitation by the VGs contributes to decreased erosion risk on the hydrofoil, with larger VGs showing enhanced effectiveness in preventing cavitation erosion.

Thermal-hydraulic analysis of wetted airside plain fin flat tube heat exchangers and the role of vortex generators

This study addresses the demand for efficient and compact heat exchange solutions in industrial applications. Unlike previous studies that predominantly focused on round tube configurations, this research investigates the impact of vortex generators and geometrical parameters on plain-fin flat-tube designs. Using ANSYS Fluent, the study evaluated the effects of fin geometry, vortex generators, and flow conditions on thermal–hydraulic performance. The key findings revealed that vortex generators enhanced heat transfer by 5–48% by promoting fluid mixing and turbulence but also leading to an increment in friction losses reaching 35–62%, depending upon the number of vortex generators. Condensation rates increased downstream of vortex generators due to enhanced mixing with cooler surfaces. In terms of thermal–hydraulic performance, specific plain-fin configurations outperformed others, offering efficient heat transfer with relatively lower friction losses, even when compactness was considered. Some configurations were recommended for applications where heat exchanger size is less important, but high heat transfer is crucial. Lastly, it was discovered that the effect of vortex generators is more pronounced for lower to intermediate pumping powers per unit area. New empirical correlations were also derived to predict thermal–hydraulic behavior based on geometry and vortex generator placement. A comparison with the literature revealed significantly higher performance as compared to convex/concave vortex generators. Lastly, it was discovered that the effect of vortex generators is more pronounced for lower to intermediate pumping powers per unit area. Empirical correlations for “j” and “f” were correlated with all geometric parameters.

Application of vortex generators to avoid subcooled flow boiling oscillation in micro-channel

Subcooled flow boiling in micro-channels is an effective solution for high-heat-flux electronics thermal management, and the heat flux has a limitation value (i.e., limiting oscillation heat flux) due to flow boiling oscillation. The purpose of this study is to propose a new method to suppress the flow boiling oscillation (i.e., forcing bubbles to leave the channel by installing a vortex generator), experimentally verify the effect of vortex generators on suppression of flow boiling oscillation and increasing limiting oscillation heat flux, and develop a predicting correlation for this heat flux. In the experiments, the vortex generator is a helix wire with a pitch of 1.8 mm, a length of 22.5 mm, a wire diameter of 0.2 mm and a diameter of 1.8 mm; the inlet subcooling degree and mass flux range from 10 – 50 K and 750–1750 kg m−2 s−1, respectively. The results show that, the flow boiling oscillation occurs in the flow channel without vortex generators while it doesn't occur in the flow channel containing vortex generators at the same working condition; the vortex generators can raise the limiting oscillation heat flux with a maximum increment of 21.1%, which indicates that vortex generators can suppress the flow boiling oscillation. A new correlation predicting limiting oscillation heat flux in channels with vortex generators was developed, and its predictions match 95% of the experimental data within ± 20% while the average deviation is 7.6%.

Investigating the Effectiveness of Vortex Generators in Aviation through High-Fidelity CFD Analysis

Investigating the Effectiveness of Vortex Generators in Aviation through High-Fidelity CFD Analysis

Improved Effectiveness of Vane-Type Vortex Generators for Incident Shock-Induced Separation

An experimental investigation is conducted to improve the control effectiveness of an array of vane-type vortex generators (VG) implemented 6 δ upstream of an incident shock-induced separation generated using a 14-deg wedge in a Mach 2.05 flow. Initially, the effect of an array of rectangular vanes (RRV) is studied by varying the vane 1) chord to height (c/h)=7.2, 4.2, 2) angle α=24, 20, 18, and 16 deg, 3) height to boundary-layer thickness (h/δ)=0.75, 0.5, 0.3, and 0.2, and 4) interdevice spacing to height (s/h)=12, 9.5, 7.5, 6.5, 5.7, 5.5, and 5.0. Similar tests were also performed for ramp vanes (RV) with α=24 deg. Due to inherent design differences, an RRV device generates a larger region of vortex influence relative to an RV device. Therefore, reducing s/h significantly reduces the extent of uncontrolled separation regions between neighboring VGs that improves their separation control capability. The best performing RRV devices with vane height h/δ=0.5, h/δ=0.3, and h/δ=0.2 show maximum reduction in separation extent of nearly 80, 74, and 70%, respectively, relative to no control. The equivalent RV devices, however, show much reduced control effectiveness. All controls exhibit a shift in the dominant separation frequency to higher values, indicating a reduction in the overall extent of separation.

The Effect of Vortex Generators on Spray Deposition and Drift from an Agricultural Aircraft

Vortex generators (VGs) attached to the leading edge of an agricultural aircraft are purported to control airflow over the upper surface of the wing by creating small vortices that delay boundary layer separation, thereby improving the performance of the aircraft. These devices are commercially available for use in the aviation industry, primarily to increase pilot control of the aircraft. The benefits attributed to VGs remain largely descriptive and anecdotal in nature without rigorous empirical assessment in the field. The intent of this study was to evaluate whether this aerodynamic device could improve deposition or reduce drift when mounted on an agricultural aircraft. Airborne drift and ground deposition were measured with monofilament lines and Mylar cards, respectively. Deposits were expressed as percent of fluorometric response using a spectrofluorophotometer. There were 46% fewer downwind drift deposits on monofilament lines when VGs were installed than when VGs were not installed. Whether or not VGs were installed on the aircraft was the predominant factor which influenced deposition on monofilament lines. Spray deposits on Mylar cards placed at ground level downwind of the applications at three different locations (5, 10, and 20 m) varied significantly (p < 0.0001) between treatments, with corresponding 31, 54, and 61% reductions in downwind deposits when VGs were installed. While these findings overall are positive, this is the first known study of its type, and more research is warranted to better understand the role of vortex generators in the reduction in drift relative to aerially applied sprays.

Numerical Study of Transonic Buffet on SC(2)-0518 and OAT15A with Vortex Generators

Predicting the transonic buffet and its onset is important for ascertaining the performance limits of an aircraft at its critical angle of attack. Additionally, a physical understanding of the buffet suppression technique is important for preventing shock wave oscillations. In this study, we conducted zonal detached-eddy simulations to numerically investigate the effects of vortex generators (VGs) on buffet suppression and to discuss the differing flow characteristics of the SC(2)-0518 and OAT15A supercritical airfoils when the chordwise position of the VGs is varied. The results for both airfoils equipped with VGs demonstrated significant suppression of large-scale lift oscillations across all calculation steps. VGs placed at 10% of the chord (10%c) from the leading edge produced higher time-averaged lift coefficients for both airfoils, with the OAT15A airfoil showing a particularly notable 2.5% improvement in lift coefficient, leading to a 0.82% increase in L/D ratio. The visualized results indicated that the interaction between the shock wave and VGs leads to variations in the separation point, depending on the VG chordwise position. This separation is affected by the aerodynamic characteristics of the airfoil shapes and the wake induced by the VGs, ultimately resulting in changes to the lift coefficient.

The effect of vortex generators having Clark-Y airfoil on tapered swept-back wing

In the experimental study, the effects of vortex generators (VGs) having Clark-Y airfoil and triangular VGs are investigated. The tests were carried out on a tapered swept-back wing at Re = 6.0×104 using counter-rotating vortex generators having Clark-Y airfoil at five different locations that are x/c= 0.1, 0.2, 0.3, 0.4, and 0.5 and triangular VGs at x/c=0.1 location. A load cell is used to measure forces at angles of attack (AoA) ranging from 0° to 30°. It is observed that the maximum lift coefficient (CLmax) and aerodynamic performance of VGs having Clark-Y airfoil decrease when the position of the vortex generators changes from 0.1 to 0.5. The optimal results obtained from the study show that the tapered swept-back wing with the VGs having Clark-Y airfoil exhibits a significant increase of 37.5% in the CLmax and approximately 55% in the lift to drag ratio (L/D) at x/c=0.1 compared to the baseline. At low AoA, the VGs having Clark-Y airfoil provided better lift, whereas at high AoA, the triangular VGs provided better lift.

Effects of vortex generators on endwall film cooling in a turbine vane

Film cooling is widely applied on endwalls in high-performance gas turbines to guarantee the safety and endurance of the engines. Micro ramps are employed to optimize the flow and thermal performance in internal and external cooling designs. In the current investigation, flat-surface film cooling at the blowing ratio of 1.0 and the density ratio of 2.0 is investigated with and without the micro ramp by LES. The result shows that the micro ramp effectively enhances the cooling performance by creating the ACRVP, drawing the coolant toward the wall and enlarging the film coverage. Mean and instantaneous vortical structures are analyzed. Endwall film cooling with micro ramps is studied with high and low mass flow ratios (MFR). The cooling effectiveness of the micro ramp case is 89.9% higher than the baseline case when MFR is high, while 16.3% higher than the baseline when MFR is low. Micro ramps are more effective for endwall film cooling with high MFR. The cooling effectiveness of the region in the middle of the passage improves when applying the micro ramps. In the region upstream of the leading edge, cooling performance deteriorates due to the interaction of the horseshoe vortex and the micro ramps.

Mach 3.5 Compression Corner Control Using Microvortex Generators

An experimental investigation has been performed to examine the effect of vortex generators (VGs) on a compression corner flow separation. Experiments are conducted at Mach 3.5 along a 23° compression corner with turbulent inflow boundary-layer and Reynolds number 27×104 based on the 6.2-mm boundary-layer thickness. Micro-ramp, standard ramped-vane, and inverted ramped-vane VGs all cause the separation line to ripple and become more three-dimensional, but none eliminate it altogether. Vane-type VGs produce a stronger control effect than micro-ramps. Inverted vanes tend to generate large areas of near-wall low-momentum flow that locally increase separation length, making standard vane configurations more effective at reducing separation size. Velocimetry measurements show that the VG-induced vortices remain coherent and capable of exchanging momentum within the boundary-layer, even downstream of the interaction. Enhanced flow three-dimensionality causes an intensification of areas of increased and decreased momentum downstream of reattachment, resulting in significant flow distortion. Increased near-wall turbulent fluctuations are observed upstream of the interaction in areas where separation length is reduced. These findings are used to propose a mechanism of VG control, highlighting the role of VGs in enhancing mixing in the separated shear layer, leading to earlier reattachment and an overall reduction in separation length.

Effects of vortex generators and pulsation on compound angle film cooling

Compound angle film cooling is widely applied in modern turbine engines to provide reliable protection for the components. As passive and active methods, vortex generators enhance the thermal performance significantly, and pulsation coolant jet increases film cooling effectiveness when the compound angle is low. In the current study, the effects of vortex generators, pulsation, and their interactions have been investigated in film cooling with compound angles of 0 deg, 30 deg, and 60 deg. Cooling efficiency distribution is analyzed considering the coolant amount and separation condition. The downwash anticounter-rotating vortex pair (anti-CRVP) generated by vortex generators effectively increases film cooling effectiveness (FCE) in compound angle film cooling. Pulsation enhances the cooling performance by reducing the coolant separation when the lateral angle to the freestream is 0 deg; however, the performance is poor with 30 deg and 60 deg. Vortex generators are less efficient in enlarging the film coverage when pulsed jets are employed due to less coolant close to the surface. Moreover, mean and instantaneous vortex structures are illustrated to show the evolvements and interactions of the anti-CRVP, the counter-rotating vortex pair, the separated wakes, and the asymmetric vortex.

Interaction mechanism between cloud cavitation and micro vortex flows

Micro vortex generators (micro-VGs) could affect cavitation, but the control mechanism is not yet fully understood. Simulating and analyzing the effect of micro vortex generators (micro-VGs) on cloud cavitation is crucial as it can help in suppressing the collapse of cavitation clouds, which is beneficial for marine machinery. In this work, micro-VGs were installed parallel to the initiation of the attached cavity on a NACA0015 hydrofoil. A compressible simulation method was used to obtain the cavitating flows around both the smooth hydrofoil and the one with micro-VGs. Subsequently, the generation of micro vortex flows and the effect of micro-VGs on transient evolution of cloud cavitation were analyzed. The results indicate that the installation of triangular micro vortex generators alters the flow vectors around them, inducing micro vortex flows with opposite rotational directions behind adjacent vortex generators. These vortex generators potentially affect cavitation on the hydrofoil by modifying pressure distribution, vortex structures, and turbulent kinetic energy. Under the specified cloud cavitation operating condition, the shedding and collapse of clouds on the smooth hydrofoil are replaced by the partial separation and collapse of sheet cavitation on the hydrofoil with micro-VGs. Despite a minor loss in time-averaged lift, the lift-to-drag ratio is improved, and the stability of the flow field is enhanced. After installing micro-VGs, the pressure fluctuation is primarily caused by the partial collapse and separation of sheet cavitation. Installing micro VGs at the hydrofoil's leading edge suppresses pressure pulsation.

The effects of vortex generators on the characteristics of the tip hydrofoil and the horizontal axis tidal turbine blade

The blade of horizontal axial tidal turbine (HATT) will experience unsteady characteristics, such as dynamic stall, hysteresis loop, and stall delay, leading to unsteady loads that challenge its performance and survivability in the complex ocean environment with turbulent flow, waves, and shear flow. Installing vortex generators (VGs) on the blade surface effectively controls flow separation and improves the performance of the HATT blades. However, most existing VGs studies focus on two-dimensional models that do not consider the tip vortex, requiring further research to investigate the influence of VGs on the blade tip and their potential benefits. This study investigates the static and dynamic effects of different VGs parameters on the NACA63820 hydrofoil installed at the tip through hydrofoil water tunnel experiments and numerical simulations to understand the advantages of using VGs in this configuration. The results show that VGs alter the pressure distribution on the hydrofoil's surface, leading to the formation of pressure humps in the pressure curve of the hydrofoil section. The number and orientation of these humps depend on the openings of the VGs. This study comprehensively analyzes the factors causing these humps and their effects. In conclusion, installing appropriate VGs at the tip significantly improve the hydrofoil's performance and reduce the size of the hysteresis loop opening. Comparing different VGs identifies optimal parameters for HATT blades and evaluate their performance through numerical simulations. The results show that installing VGs at the 30% chord position of the airfoil section can improves the power coefficient by 1.6% at the optimal blade tip speed and broadens the operating range of the HATT.

Effect of Vortex Generations on Aerodynamic Performance of Rough Wind Turbine Airfoil

Experimental investigations were carried out in wind tunnel facilities to assess the effect of vortex generators on the aerodynamic characteristics of a NACA4418 airfoil, particularly in scenarios where surface roughness is precipitated by environmental elements like dust, sand, and insects. These elements are known to adversely affect the efficiency of power generation. These studies meticulously analyzed the airfoil’s pressure distribution and its aerodynamic coefficients, taking into account the roughness positioned at varying locations along the chord. Special attention was given to the roughness located at 0.2c due to its pronounced impact on aerodynamic efficiency. The research highlighted that vortex generators play a crucial role in mitigating boundary layer separation, thereby enhancing the lift-to-drag ratio, especially at higher angles of attack. Notably, the deployment of vortex generators on airfoils affected by surface roughness resulted in a more pronounced improvement, elevating the maximum lift coefficient by 11.6% compared to their effect on smooth airfoils. Furthermore, the study revealed that an increase in the Reynolds number significantly augments the benefits provided by vortex generators, improving the lift coefficient and delaying the stall angle for airfoils with surface roughness, while also shifting the boundary layer separation point towards the airfoil’s trailing edge.

Effects of Downstream Vortex Generators on Film Cooling a Flat Plate Fed by Crossflow

Abstract Counter-rotating vortices, formed by the interaction of film-cooling jets and the hot gas flow, adversely affect the performance of conventional film-cooling designs. Downstream vortex generators have been shown to improve cooling effectiveness by mitigating the effects of the counter-rotating vortices and by deflecting the cooling jet laterally. In this study, computational and experimental methods were used to examine how cylindrical film-cooling holes (D = 3.2 mm, L/D = 6, p/D = 3, α = 30 deg) with and without downstream vortex generators perform when the coolant supply channel is perpendicular to the direction of the hot gas. For this study, the hot gas had a temperature of 650 K and an average Mach number of 0.23. The hot-gas-to-coolant temperature ratio was 1.9, and two blowing ratios (0.75 and 1.0) were studied. Results from the computational fluid dynamics study show how crossflow affects the interaction between the film-cooling jet and hot gas flow with and without downstream vortex generators. The experimental measurements were based on infrared thermography in a conjugate heat transfer environment. Results were obtained for film-cooling performance in terms of overall effectiveness, film effectiveness, and local heat transfer coefficients. The downstream vortex generators can increase the laterally averaged effectiveness by a factor of 1.5 relative to cylindrical holes, but this higher performance is restricted to low crossflow velocities and higher blowing ratios.

Numerical Study on the Effect of Vortex Generators on the Aerodynamic Drag of a High-Speed Train

Numerical Study on the Effect of Vortex Generators on the Aerodynamic Drag of a High-Speed Train

The effect of three-type Vortex Generators (VGs) on NACA-0015 hydrofoil cavitation formation at different angles of attack

Cavitation, the formation of vapor bubbles on hydrofoil surfaces, poses a significant challenge to the performance and durability of marine vessels utilizing hydrofoils. Vortex generators, small structures embedded on the hydrofoil surface, have emerged as a potential solution for mitigating cavitation, but the optimal shape of vortex generators for achieving maximum cavitation resistance remains an open question. This study aims to address this challenge by systematically investigating the impact of rectangular, triangular, and circular vortex generators on the cavitation characteristics of a NACA-0015 hydrofoil. Utilizing computational fluid dynamics (CFD) simulations, the influence of these vortex generator shapes on cavitation inception and critical cavitation numbers will be evaluated under varying angles of attack and flow velocities. The findings of this study will provide valuable insights into the design and optimization of vortex generators for hydrofoil applications. Despite the effectiveness of vortex generators in mitigating cavitation, the optimal vortex generator shape for specific hydrofoil designs and operating conditions remains unclear. The precise mechanisms by which vortex generators suppress cavitation are not fully understood, requiring further investigation to optimize their design and placement. The durability and long-term performance of vortex generators under various environmental conditions, including turbulence and corrosion, warrant further evaluation. By addressing these unsolved challenges, this study will contribute to the advancement of vortex generator technology and its practical application in hydrofoil systems, leading to more efficient and reliable marine vessels.

Numerical study of the vortex generators effects in a corrugated channel for turbulent flow

Vortex Generators (VGs) are one of many techniques used to improve the efficiency of heat exchangers. In this paper, we will investigate in a numerical study a rectangular winglet and a long winglet VGs inside a corrugated channel with a change of Rynolds number from 5000 to 17500. The role of VGs is to manupilate flow, which increases the Nusselt number (Nu) and increases the friction coefficient, which are considered disadvantages. For that, we calculate the thermal performance coefficient PEC to see if VGs give us more heat compared to what we will lose from friction, and the results show a good PEC greater than 1, and comparing between rectangular and long VGs, we have almost the same results with a small difference in NU for rectangular VGs being higher than long VGs, and the coefficient of friction is smaller, which means we are battered. The results are discussed in detail in this paper.

Effect of aero-shaped vortex generators on NACA 4415 airfoil

A parametric study was carried out to investigate the effect of aero-shaped vortex generators (AsVGs) on NACA 4415 airfoil by comparing conventional vortex generators (CVGs). Force and flow visualization experiments were carried out for the CVGs and AsVGs at Re = 1.4 × 105. Six different configurations were selected for the positioning of the CVGs to investigate the best one. The best configuration was applied to the Aero-shaped VGs type, which is generated with the S1223 airfoil model. The results indicated that even if AsVGs did not show better performance to delay the stall angle when compared with the CVGs, in some positions they produced the same stall performance as the CVGs. Moreover, aero-shaped VGs increased the lift coefficient (CL) more than the conventional ones in the pre-stall region. At x/c = 0.1, CL and CD improve by up to 107.7% and 23.39% compared to baseline, respectively. At α = 18° and Re = 0.8 × 105, AeM5 at x/c = 0.1 increased the CL by 102.45% compared to the baseline model. While the CVGs increased the lift coefficient (CL) and postponed the stall (α) angle up to 4° according to the baseline model, the CVGs also caused an overall increase in the drag coefficient (CD). AsVGs decreased the drag coefficient (CD) more than conventional ones. Lift to drag ratio (L/D) of AsVGs is higher than that of the CVGs. The results of the surface oil flow visualization showed that both CVGs and AsVGs segmented the laminar separation bubble (LSB) and formed attached flow zones on the airfoil surface. As a result, AsVGs can be used as an alternative to CVGs in flow control applications.