In this study, flow behind rectangular vane type Vortex Generators mounted on a flat plate, is numerically simulated using the immersed boundary (IB) method. In the present work, the direct forcing IB method is employed because of its simplicity and high efficiency. Vortex Generators of two different heights are numerically investigated. The height of vanes in the first case is close to the definition of submerged/lowprofile Vortex Generators while the other case is closer to the definition of a conventional Vortex generator. The resultant highly three-dimensional flow and its transition to turbulence have been studied. Counterrotating vortices generated by these passive rectangular Vortex Generators are characterized. Streamwise evolution of non-dimensionalised maximum values of vorticity, Vortex strength, streamwise velocity and wall-normal velocity are studied. The simulations show that the IB method in conjunction with DNS effectively simulates the time-dependent flow behind an array of passive Vortex Generators placed in an initially laminar boundary layer.

In this paper, the performance of sub boundary layer Vortex Generators and conventional Vortex Generators in controlling the separation bubble has been compared and the resultant highly three-dimensional flow has been studied. Two pairs of Vortex Generators mounted symmetrically along the spanwise direction are placed upstream of separation point to produce counter-rotating vortices. Effect of these three-dimensional Vortex Generators on the separation bubble and the flow downstream has been examined. The simulations show that the length of the separation bubble is reduced by sixty two per cent due to the deployment of Vortex Generators of height 0. 33 δ while the original separation bubble is completely eliminated by the Vortex Generators of height 0. 66 δ . However the presence of larger height Vortex Generators by itself causes a small mean separation bubble downstream. The flow downstream of Vortex Generators is highly three-dimensional and zones of recirculation can be observed between regions of attached flow. Presence of adverse pressure gradient results in greater interaction between counter-rotating vortices, leading to their early breakup and higher Vortex decay rate compared to the zero pressure gradient case. Further, it is seen from the simulations that the counter-rotating array of vortices does not move away from the wall even far downstream.

This research work aims at designing a solar endurance glider for an increased flight time. The constraints for the design include reduction in weight compared to a typical glider, and improving its aerodynamic performance by application of the Vortex Generators on its wingspan. The design of each component is performed through various stages of similitude cases; furthermore, the components such as the solar panels and Vortex Generators are selected based on a decision matrix design process. This research work utilizes the ANSYS 18. 1 K-Omega SST turbulence simulation techniques in order to successfully simulate the glider at different speeds along with various angles of attack for the aerodynamics optimization. The results obtained show an improvement in the lift force from 160 N to 192 N once the Vortex Generators are installed. 16 solar cells are installed on the glider’ s wings, providing 57. 6 Watts of power. This work faces a limitation on the physical testing using a wind tunnel for validation; therefore, the team relies on the CFD simulation verification from the published data. This report details the concepts of boundary layer, design process, and glider simulation as well as the glider configurations such as the wingspan and total length. The glider should be able to maintain a flight time of at least 6 hours with Vortex Generators and solar panels.

The usefulness of the supersonic jet is inhabitable in the Aerospace industry. However, control of the supersonic jet is important for efficient mixing and noise attenuation. Particularly, asymmetric jets are better than axisymmetric jets in rapid mixing. Considering this, the experimental investigation has been carried out for the Vortex Generators or tab-controlled Mach 1.6 elliptic jet. To compare the impact of the locations of the Vortex Generators, they are deployed at the diametrically opposite locations of the nozzle outlet along the major or longest axis and the minor or shortest axis, respectively. The investigations have been carried out using the centerline pressure distributions employing the Pitot probe and the Schlieren flow visualizations. A maximum of 66.43% reduction in supersonic length has been observed from the centerline pressure distributions for the Vortex generator placed along the shortest axis. In addition, the Schlieren flow visualizations confirm substantial distortions in the shock cell structures when the Vortex Generators are placed along the shortest axis which results in noise mitigation. The study concluded that the impact of the Vortex generator, placed along the shortest axis, is superior in the manipulation of shock cell structure, efficient mixing, and thereby noise mitigation than those placed along the longest axis.

Rectangular S-duct diffusers are widely used in air-intake system of several military aircrafts. A well-designed diffusing duct should efficiently decelerate the incoming flow, over a wide range of incoming conditions, without the occurrence of stream wise separation. A short duct is desired because of space constraint and aircraft weight consideration, however this results in the formation of a secondary flow to the fluid within the boundary layer. The axial development of these secondary flows, in the form of counter rotating vortices at the duct exit is responsible for flow non-uniformity and flow separation at the engine face. Investigation on S-shaped diffusers reveals that the flow at the exit plane of diffusers is not uniform and hence offers an uneven impact loading to the downstream components of diffuser. Experiments are conducted with an S-shaped diffuser of rectangular cross-section at Re=1.34´105 to find out the effects of the corners (i.e. sharp 90o, 45o chamfered etc.) on its exit flow pattern. A ‘fishtail’ shaped submerged Vortex Generators (VG) are designed and introduced at different locations inside the diffusers in multiple numbers to control the secondary flow, thereby improving the exit flow pattern. It is found that the locations of the VG have a better influence on the flow pattern rather than the number of the VG used. The best combination examined in this study is a 45o chamfered duct with 3´3 VG fixed at the top and bottom of the duct inflexion plane.The results exhibit a marked improvement in the performance of S-duct diffusers. Coefficient of static pressure recovery (CSP) and coefficient of total pressure loss (CTL) for the best configuration are reported as 48.57% and 3.54% respectively. With the best configuration of VG, the distortion coefficient (DC60) is also reduced from 0.168 (in case of bare duct) to 0.141.

An empirical and numerical study was conducted to investigate the flow characteristics in a diffuser fitted with different arrangements of Wing Vortex Generators (WVGs), including Delta Wing Vortex Generators (DWVGs) and Rectangular Wing Vortex Generators (RWVGs). The flow at the diffuser inlet was uniform, and its development was analyzed. The WVGs were positioned near the inlet. The Reynolds number (Re), calculated based on the diffuser length and inlet velocity, ranged from 17,000 to 43,000. The loss coefficient (K) decreases as Re increases in the smooth diffuser and declines further in roughened cases, primarily due to reduced flow separation. By mitigating flow separation and enhancing pressure recovery (CP is defined as the ratio of the pressure increase to the dynamic pressure at the diffuser throat), the WVGs improve the pressure coefficient (CP) compared to the smooth case. The increase in CP is more pronounced for RWVGs than DWVGs in all tested configurations, indicating that RWVGs are more effective at controlling flow separation. Additionally, three RWVG pairs produce a higher skin friction factor (Cf) than other configurations.

The main purpose of this article is to provide a critical analysis of published research on these heat transfer surfaces. Important experimental methods and numerical procedures are explained, and many types of Vortex Generators are described. The phenomenon of flow attributed to Vortex Generators mounted, connected, pierced, or placed inside surfaces that transmit heat was also examined. In addition, recommendations for applying Vortex generator (VGs) technology to improve air-side heat transfer are provided, as well as information on the thermal performance of newly proposed VG heat transfer surfaces. The performance of air-side heating surfaces can often be significantly improved through the use of Vortex Generators. However, their effectiveness can be greatly affected by many factors, including fluid flow rate, pipe geometry (diameter, shape, pitch, in-line or staggered configuration), fin type, and geometry of the Vortex generator (height, length, shape, angle of attack, etc.). Circular fin-tube heat exchangers generally perform worse in terms of thermal-hydraulic efficiency than flat-tube-fin and oval-tube-fin heat-exchanging devices, and more recently, suggested Vortex Generators. Most current heat exchanger optimization methods focus only on thermal-hydraulic performance.

The present work discusses the aerodynamic behaviour of a typical SUV car model mounted with three Vortex Generators (VGs) similar to the shape of a right-angled triangle in four different yaw angle configurations, the results of which have been quantitatively assessed in the sub-sonic wind tunnel and by using realizable (k-ε ) model. The VG positioned in the middle is kept in the fixed state while the yaw position of VGs on either side has been modified and its significance is presented in this article. The pressure distribution data along the central plane of the car model for all the cases have been obtained by using 32 channel digital pressure scanner that is connected with the pressure tapings prepared in the symmetrical plane of the car model. Simultaneously two separate cantilever type load cell setup is used in this work to measure the magnitude of drag and lift force with measuring sensitivity of about 0. 01N. From the experiments, it is determined that the car model with outer VGs heading the rear windshield and central plane possess the maximum drag and lift coefficient reduction rate of about 4. 35% and 3. 23% respectively compared to car model without VGs. In addition to these findings it is also determined that the vehicle model with VGs positioned perpendicular to the wind stream direction exhibited strong drag magnitude than that of the vehicle without VGs. This increased drag can be utilized for rapid deceleration of vehicle motion (Aerodynamic braking) particularly at the instance of vehicle is running at high speed conditions. The realizable (k-ε ) model estimated the drag and lift coefficient closer to that of wind tunnel results and exhibited a maximum error deviation of 2. 38%. Further, realizable (k-ε ) model predicted the existence of the magnitude of velocity gradient, intensity of turbulent kinetic energy variation and streamlined pattern of velocity gradient around the vehicle with VGs compared to the case of vehicle model without VGs at its rear end.

In this research, aerodynamic performance of a double s-shaped serpentine inlet duct is numerically investigated by using of blowing Jet Vortex Generators flow control technique. At first, turbulence equations are validated by comparing the numerical results with experimental test data of a standard inlet, and aerodynamic loss parameters of a sample serpentine inlet are estimated in flight condition of Mach=0. 7 at Altitude=9000m. Then the effect of active flow control technic on the loss parameters are studied by installing two sets of 20 blowing Vortex Generators on the upper and lower walls of the duct in 5 separated and integrated arrangement schemes by simulating 0. 01 and 0. 02 blowing mass flow ratios. By comparing between 5 schemes with clean duct in the fields of blowing mass flow ratio, 2% blowing ratio has better improvement results in all schemes. In the field of arrangement position, C3 and C5 schemes respectively by 3. 1% and 3. 12% increase in total pressure recovery, 67. 16% and 64. 66% decrease in DC(60) distortion coefficient and 71. 8% and 64. 5% decrease in DPCP coefficient at 2% blowing mass flow ratio, are selected as the best flow control scheme.

Investigating the effects of aerodynamic characteristics in the automotive segment has been one of the thrust areas of research in the recent years. Extensive research had been carried out earlier in minimizing the aerodynamic drag of the car body and to study the effects using passive air flow deflectors. Little work has been conducted on semi-active or actively controlled air flow modification techniques. In order to contribute new knowledge in the chosen area and to draw the attention of current researchers the present work focuses on the study of aerodynamic characteristics of a typical sedan car model equipped with three numbers of delta shaped Vortex Generators (VGs) as an aerodynamic add-on device to delay the early flow separation of air from the vehicle body. The yaw angles of the VGs are semi actively controlled using mini stepper motors. The middle VG is kept stationary, whereas the other two VGs orientation has been modified and the results have been studied. The aerodynamic property of a car model mounted with four distinct yaw angle configurations obtained by means of mini stepper motor has been quantitatively evaluated by sub-sonic wind tunnel tests and computational analysis. From the experiments the peak drag and lift coefficient reduction rates of 4. 53% and 2. 55% respectively have been observed in the case of car model with Vortex Generators having leading edges facing the rear end and the mid plane of the car respectively when compared with the car model without Vortex Generators. Numerical simulation using realizable (k-ε ) model predicted the drag and lift coefficient reduction rates closer to the experimental values and also it predicted the existence of magnitude of turbulent kinetic energy variation in the roof portion of the car model with four dissimilar configurations of Vortex Generators relative to the case of car model without Vortex Generators.