Rear Wing Research Articles

Structural Design of a Composite Trimaran

This paper presents a project of a composite trimaran structure, designed and built for competing at the Hydro Contest 2016 competition at Geneva Lake. Concept of the contest is to raise the awareness of tomorrow’s engineers, industrialists, opinion leaders and the public of what is at stake with regard to energy efficiency in the sea transportation of goods and passengers. In addition, to be the laboratory of tomorrow’s boats, particularly enabling the most innovative ideas to be developed in collaboration with the industrial partners. Designed boats must have technological innovations enabling them to achieve the most efficient use of energy. Therefore, the goal was to design, construct lightweight structure, within simple closed rules, with a satisfactory stiffens, and strength as well as to strive for more efficient transport, which means higher speed with minimal energy consumption. An analysis of project variants was made with regard to the hull shape, material, and technology of the fabrication and for the adopted variant, a computer structure model was developed, and the FEA was carried out. The structure is divided into three main sections analysed individually: hulls, front wing and rear wing along with rudder. Calculation was made for the worst load case, i.e. mass transfer, while wings were analysed at the highest advancing speed. The boat has structurally met all requirements since there were no structural problems in testing and competing.

Aerodynamic optimisation of Formula student vehicle using computational fluid dynamics

This work aims to improve the external aerodynamic characteristics of the 2017 University of Huddersfield Formula SAE vehicle. To improve dynamic performance in the SAE events, a multiple-element rear wing was developed, which incorporated adjustable elements to constitute a drag reduction system (DRS). A numerical modelling approach was adopted to produce a suitable design. A simplified model of the vehicle was created to obtain baseline coefficients of lift (CL) and drag (CD). The rear wing was optimised to find the peak configuration generating maximum downforce. The results show that the incorporated rear wing improved the vehicle’s CL from 0.21 acting in the positive Y axis (lift) to 1.15 acting in the negative Y axis (downforce), whereas the CD increased from 0.71 to 1.21. However, the DRS configuration reduced the CD to 0.79. Using the obtained lift and drag coefficients, vehicle performance was estimated, such as maximum cornering speed, straight-line top speed and straight-line acceleration capabilities. The rear wing improved the theoretical maximum cornering speed by 3.1% for a corner radius of 13 m. The DRS increased the theoretical top speed by 18.2% compared to a fixed wing configuration. Acceleration potential increased by 15.7% at 25 m/s with the DRS open. The final section of the study used an online simulator (FSAESim) to make predictions of the acceleration event time, which were compared to the track results from the 2017 Hungary SAE event. The results showed a 97% similarity.

Numerical Investigation of the Influence of the Configuration Parameters of a Supersonic Passenger Aircraft on the Intensity of Sonic Boom

Results of calculations of the sonic boom produced by a supersonic passenger aircraft in a cruising regime of flight at the Mach number M = 2.03 are presented. Consideration is given to the influence of the lateral dihedral of the wings and the angle of their setting, and also of different locations of the aircraft engine nacelles on the wing. An analysis of parametric calculations has shown that the intensities of sonic boom generated by a configuration with a dihedral rear wing and by a configuration with set wings remain constant, in practice, and correspond to the intensity level created by the optimum configuration. Comparative assessments of sonic boom for tandem configurations with different locations of the engine nacelles on the wing surface have shown that the intensity of sonic boom generated by the configuration with an engine nacelle on the windward side can be reduced by ~14% compared to the configuration without engine nacelles. In the case of the configuration with engine nacelles on the leeward size of the wing, the profile of the sonic-boom wave degenerates into an N-wave, in which the intensity of the bow shock is significantly reduced.

THE INFLUENCE OF WINGLETS ON THE AERODYNAMIC CHARACTERISTICS AIRCRAFT WITH THE TANDEM SCHEME

«Tandem» aerodynamic aircraft scheme with comparable areas of front and rear wings is well-known in aviation.«Tandem» scheme allows increasing in lift and lifting capacity with limited wingspan. So, it has found a new application in modern unmanned aerial vehicles.However, an increase in the number of lifting surfaces also leads to aircraft drag increasing. To solve this problem on classical aerodynamic schemes winglets, small additional elements at the wingtips which reduce the induced drag and increase the lift, are used. Such an effect can be achieved by selecting the optimal geometric characteristics of the winglets.Winglets are almost not used for tandem-scheme aircraft. Theoretically, winglets installing on the front wing of the tandem aircraft allows reducing the induced drag of both the front wing and the rear wing. But the open sources do not contain the experimental confirmation. Thus, the research task of the winglets effect on the tandem aircraft aerodynamics remains unsolved.Presented investigation allows estimation of the winglets effect on lift-drag ratio, pitch, roll and yaw static stability coefficients for tandem-scheme aircraft.

DESIGN AND ANALYSIS OF AN AERODYNAMIC DOWNFORCE PACKAGE FOR A FORMULA STUDENT RACE CAR

This paper presents design of aerodynamic downforce generating devices (front wing, rear wing and diffuser) to enhance the performance of the Formula Student Race Car using numerical and experimental studies. Numerical results using computational fluid dynamics (CFD) studies were primarily validated with the experimental results performed in the wind tunnel. It was concluded that the use of a downforce package can enhance the performance of the vehicle in the competition.

Downforce variation dependence of angle of incidence modification for the rear wing of high speed vehicles

The conventional downforce devices (with fixed geometry) of high speed vehicles have parameters such as area, angle of incidence and head resistance coefficients, all with constant values. The downforce is proportional with the square of movement speed and the power consumed for the neutralization of aerodynamic road resistance is proportional with the cube of speed. The authors carried out an analytical study of downforce, adjustable/monitored by optimum incidence (modification of incidence angle of rear wing for performance improvement).

Study on airflow characteristics of rear wing of F1 car

The paper aims to investigate CFD simulation is carried out to investigate the airflow along the rear wing of F1 car with Reynold number of 3 × 106 and velocity, u = 43.82204 m/s. The analysis was done using 2-D model consists of main plane and flap wing, combined together to form rear wing module. Both of the aerofoil is placed inside a box of 350mm long and 220mm height according to regulation set up by FIA. The parameters for this study is the thickness and the chord length of the flap wing aerofoil. The simulations were performed by using FLUENT solver and k-kl-omega model. The wind speed is set up to 43 m/s that is the average speed of F1 car when cornering. This study uses NACA 2408, 2412, and 2415 for the flap wing and BE50 for the main plane. Each cases being simulated with a gap between the aerofoil of 10mm and 50mm when the DRS is activated. Grid independence test and validation was conduct to make sure the result obtained is acceptable. The goal of this study is to investigate aerodynamic behavior of airflow around the rear wing as well as to see how the thickness and the chord length of flap wing influence the airflow at the rear wing. The results show that increasing in thickness of the flap wing aerofoil will decreases the downforce. The results also show that although the short flap wing generate lower downforce than the big flap wing, but the drag force can be significantly reduced as the short flap wing has more change in angle of attack when it is activated. Therefore, the type of aerofoil for the rear wing should be decided according to the circuit track so that it can be fully optimized.

Passive variable rear-wing aerodynamics of an open-wheel racing car

A rear wing designed to improve motoring performance and enhance stability during cornering needs to generate a large downforce at a relatively low speed. If the angle of attack of the rear wing is large, then air resistance is increased during high-speed driving, and thus, fuel consumption is increased due to the large drag values. On the other hand, the performance on high-speed cornering will improve overall lap time with an increased angle of attack. To mitigate this disadvantage, we aimed to reduce the angle of attack during high-speed driving to reduce downforce and drag and thus to reduce fuel consumption. Meanwhile, during low-speed driving, for example in cornering, the angle of attack was increased and a large downforce generated to improve driving stability. In order to achieve both goals, we developed a passive-type variable rear wing. This rear wing was designed to have a three-step shape where the second step in the center was designed to swing. We first confirmed the behavior through both computer-aided engineering analysis and wind tunnel experiments, and then we constructed a full-size rear wing and measured the downforce on a student Formula SAE vehicle. The results showed that it is possible to generate a downforce of 80 N at a low speed of 30 km/h (8.3 m/s) and a downforce of 145 N at a high speed of 50 km/h (13.9 m/s).

Active Rear Wing System Aerodynamic Optimisation for Truck Trailers

Active Rear Wing System Aerodynamic Optimisation for Truck Trailers

Genetic algorithm-based optimization design method of the Formula SAE racing car’s rear wing

The aerodynamic devices play an important role on the performance of the Formula SAE racing car. The rear wing is the most significant and popular element, which offers primary down force and optimizes the wake. In traditional rear wing optimization, the optimization variables are first selected, and separately enumerated according to the analyzing experience of the racing car’s external flow field, and thus the optimal design is chosen by comparison. This method is complicated, and even might lose some key sample points. In this paper, the attack angle of the rear wing and the relative position parameters are set as design variables; then the design variables’ combination is determined by the DOE experimental design method. The aerodynamic lift and drag of the racing car for these variables’ combinations are obtained by the computational fluid dynamics method. With these sample points, the approximation model is produced by the response surface method. For the sake of gaining the best lift to drag ( FL/ FD) ratio, i.e. maximum down force and the minimum drag force, the optimal solution is found by the genetic algorithm. The result shows that the established optimization procedure can optimize the rear wing’s aerodynamic characteristic on the racing car effectively and have application values in the practical engineering.

Aerodynamic Analysis of Grand Prix Cars Operating in Wake Flows

The effect of the upstream wake of a Formula 1 car on a following vehicle has been investigated using experimental and computational methods. Multiple vehicle studies in conventional length wind tunnels pose challenges in achieving a realistic vehicle separation and the use of a short axial length wake generator provides an advantage here. Aerodynamic downforce and drag were seen to reduce, with greater force reductions experienced at shorter axial spacings. With lateral offsets, downforce recovers at a greater rate than drag, returning to the level for a vehicle in isolation for offsets greater than half a car width.The effect of the wake was investigated in CFD using multiple vehicle simulations and non-uniform inlet boundary conditions to recreate the wake. Results closely matched those for a full two-vehicle simulation provided the inlet condition included unsteady components of the onset wake. Creating a nonuniform inlet condition allowed the wake parameters to be modified to test sensitivity to different wake features. Dynamic pressure deficit in the wake is shown to have the greatest impact on the following vehicle, reducing loading on the downforce producing surfaces. Wake up-wash and vortex flows are shown to have a smaller effect on downforce generated by the following car, but have an important role in diverting the dynamic pressure deficit upwards and over the following car.Future regulation changes, aimed at reducing the downforce loss experienced when following another car, should aim to reduce the velocity deficit onset to the following car; either by reducing wheel and underbody wakes, or by extracting the wake using up-wash from the rear wing.

Diffraction as a reason for slowing down light pulses in vacuum

The mean velocity of a finite-size short light pulse in a far zone is defined as the vectorial sum of velocities of all rays forming the pulse. Because of diffraction, the mean pulse velocity defined in this way is always somewhat smaller than the speed of light. The conditions are found when this slowing-down effect is sufficiently pronounced to be experimentally measurable. Under these conditions the original Gaussian shape of a pulse is found to be strongly modified with significant lengthening of the rear wing of the field envelope. Schemes for measuring these effects are suggested and discussed.

Investigation and Analysis on Racing Car Front Wings

A great number of studies have been done on aerodynamic test for the racing car. Due to critical competition among the racing car teams, the results of the studies will only been published when they are obsolete. This study was conducted by using the Computational Fluid Dynamics (CFD) utilising SolidWorksTM to perform simulations about the airflow on the front and rear wings of a racing car with different angles of attack. The analysis generates the theoretical Lift force, Down force, and Drag force for a racing car wing. Consequently, at higher velocity, the down force and interrelated induced drag increases. The maximum speed on a straight part is thus reduced due to the increase in induced drag. Finally, tests from the C15 wind tunnel also show similar trends to those derived from the simulations. Compared with results of Model geometry and wind tunnel tested, it is shown that an angle between -10° and -20° below the horizontal indicates the stalling conditions.

Aerodynamics of two-dimensional flapping wings in tandem configuration

This paper reports a fundamental investigation on the aerodynamics of two-dimensional flapping wings in tandem configuration in forward flight. Of particular interest are the effects of phase angle (φ) and center-to-center distance (L) between the front wing and the rear wing on the aerodynamic force generation at a Reynolds number of 5000. Both experimental and numerical methods were employed. A force sensor was used to measure the time-history aerodynamic forces experienced by the two wings and digital particle image velocimetry was utilized to obtain the corresponding flow structures. Both the front wing and the rear wing executed the same simple harmonic motions with φ ranging from −180° to 180° and four values of L, i.e., 1.5c, 2c, 3c, and 4c (c is the wing chord length). Results show that at fixed L = 2c, tandem wings perform better than the sum of two single wings that flap independently in terms of thrust for phase angle approximately from −90° to 90°. The maximum thrust on the rear wing occurs during in-phase flapping (φ = 0°). Correlation of transient thrust and flow structure indicates that there are generally two types of wing-wake interactions, depending on whether the rear wing crosses the shear layer shed from the front wing. Finally, increasing wing spacing has similar effect as reducing the phase angle, and an approximate mathematical model is derived to describe the relationship between these two parameters.

Flight dynamics model for preliminary design of PrandtlPlane wing configuration with sizing of the control surfaces

This paper deals with the evaluation of the flight dynamics response of aircraft with a PrandtlPlane configuration by means of simple models to be used during the preliminary design. The study is completed by a method for an initial sizing of the elevators and the ailerons (positioned on both the front and the rear wing) in order to achieve adequate handling qualities. The flight dynamics model considers the rigid aircraft, the steady aerodynamics, and separating the longitudinal and the lateral-directional motions. The force derivatives are extrapolated through a VLM solver whose the reliability of the results has been proven. The methods have been applied on the IDINTOS aircraft with the conclusion that we obtain a proper longitudinal dynamic response with a reduced Margin of Stability because of the very high values of the aerodynamic damping Mq and the pitch stiffness Malpha.

Aerodynamic Model for Tandem Flapping Wings

An aerodynamic model for tandem flapping wings is proposed. The model attempts to represent insects such as the dragonfly. Two advances are presented: the aerodynamic model with tandem wings flapping simultaneously, and the wing-stroke optimization. The aerodynamic model accounts for the inflow effects of the front wing (forewing) on the rear wing (hind wing). The stroke is optimized at two flight conditions (acceleration and level flight) by using a heuristic optimization procedure (particle swarming). The vector of the design variables consists of 28 independent parameters (14 per wing), each with a constrained range derived from the maximum available power, the flight muscle ratio, and kinematics of real insects. The cost function is the propulsive efficiency coupled with constraints for flight stability. Prediction of the level flight efficiency is in agreement with the flight muscle efficiency. The maximum acceleration is found to be dependent on the size of the flight muscle. Finally, a study of the wing shape is presented for both level and accelerating flight conditions.

Ultralight amphibious PrandtlPlane: the final design

The IDINTOS project, co-founded by the Regional Government of Tuscany (Italy), concerns the design of a ultralight amphibious PrandtlPlane and the manufacturing of a flying prototype. A consortium of universities and private companies participated to the project, coordinated by University of Pisa. The paper describes the general design of the aircraft, including aerodynamics, hydrodynamics, structures, propulsion, undercarriages and interior design etc. The aircraft presents a PrandtlPlane wing configuration in order to improve the aerodynamic efficiency and to enhance the safety with respect to stall and manoeuvrability. The control surfaces (ailerons and elevators) are located on both front and rear wing so that the flight mechanics results different with respect to the conventional aircraft. The solution adopted for the propulsion system consists of two ducted propellers that are set laterally on the fuselage. The flap system is made of Fowler flaps in the front wing and plain flaps in the rear one. The interior design of the cabin has been oriented towards a better ergonomic position of the passengers whereas the dispositions of the commands wants to minimize the possibility of any human errors.

Optimization of SAE Formula Rear Wing

The main goal of this work was to prove the superiority of a slat vs. a second rear flap in the SAE formula rear wing design, combined with a 3D curved rear flap, for low velocities, by optimization of the rear wing design. Two different main designs were compared, with five different height positions of the main wing and complete analysis carried out of the attack angle on wing performance. A numerical approach was used to test the hypothesis with 3D shear stress transport (SST) Reynolds-averaged Navier-Stokes (RANS) simulation, incorporating the whole formula. A practical use of this work is in designing a rear wing for maximum downforce within the available rules and regulations. It was found that the multi-element wings were suitable for low speeds and that the base design with two flaps should not be positioned too low. The downforce increases with the height of the wing and reaches its maximum value at 8° angle of attack. For this reason, the new curved design was proposed, including a slat and only one flap. The new wing can cope with a greater angle of attack, has a greater lift coefficient, as well as greater maximal downforce. The advanced design resulted in an increase of downforce of about 6 % at the same wing height.

Automobile aerodynamics influenced by airfoil-shaped rear wing

Computational model is developed to analyze aerodynamic loads and flow characteristics for an automobile, when the rear wing is placed above the trunk of the vehicle. The focus is on effects of the rear wing height that is investigated in four different positions. The relative wind incidence angle of the rear wing is equal in all configurations. Hence, the discrepancies in the results are only due to an influence of the rear wing position. Computations are performed by using the Reynolds-averaged Navier-Stokes equations along with the standard k-e turbulence model and standard wall functions assuming the steady viscous fluid flow. While the lift force is positive (upforce) for the automobile without the rear wing, negative lift force (downforce) is obtained for all configurations with the rear wing in place. At the same time, the rear wing increases the automobile drag that is not favorable with respect to the automobile fuel consumption. However, this drawback is not that significant, as the rear wing considerably benefits the automobile traction and stability. An optimal automobile downforce-to-drag ratio is obtained for the rear wing placed at 39 % of the height between the upper surface of the automobile trunk and the automobile roof. Two characteristic large vortices develop in the automobile wake in configuration without the rear wing. They vanish with the rear wing placed close to the trunk, while they gradually restore with an increase in the wing mounting height.

Experimental study comparing racecar aerodynamic downforce-generating devices using scale model NASCAR COT

The performance and safety of the rear wing and spoiler employed on the National Association of Stock Car Auto Racing (NASCAR) COT (car of tomorrow) racecar are experimentally studied using 10 % scale models in a water channel. Particle image velocimetry is used to qualitatively examine the differences in flow structures between the two downforce-generating devices under 0 and 180-degree yaw cases. The latter is important due to an issue with the COT flipping into the air when at extreme yaw (i.e. during a crash). At zero yaw, it is observed that smaller length scales of the flow structures in the wake of the wing compared to those in the wake of the spoiler, provide more predictable handling for racecars in close proximity and may allow more safe and competitive racing. At 180-degree yaw, it is observed that wake-structure interactions may not allow proper operation of anti-flipping devices (roof flaps) on the winged car. In the extreme yaw case, local flow scales are examined and show much stronger Reynolds number (Re) dependence for the wing than the spoiler.