Experimental and Numerical Analysis of the Aerodynamic Characteristics of the Flexing Wing With Active Camber Design

Racecar aerodynamic development requires well-correlated simulation data for rapid and incremental development cycles. Computational Fluid Dynamics (CFD) simulations and wind tunnel testing are industry-wide tools to perform such development, and the best use of these tools can define a race team’s ability to compete. With CFD usage being limited by the sanctioning bodies, large-scale mesh and large-time-step CFD simulations based on Reynolds-Averaged Navier–Stokes (RANS) approaches are popular. In order to provide the necessary aerodynamic performance advantages sought by CFD development, increasing confidence in the validity of CFD simulations is required. A previous study on a Scale-Averaged Simulation (SAS) approach using RANS simulations of a Gen-6 NASCAR, validated against moving-ground, open-jet wind tunnel data at multiple configurations, produced a framework with good wind tunnel correlation (within 2%) in aerodynamic coefficients of lift and drag predictions, but significant error in front-to-rear downforce balance (negative lift) predictions. A subsequent author’s publication on a Scale-Resolved Simulation (SRS) approach using Improved Delayed Detached Eddy Simulation (IDDES) for the same geometry showed a good correlation in front-to-rear downforce balance, but lift and drag were overpredicted relative to wind tunnel data. The current study compares the surface pressure distribution collected from a full-scale wind tunnel test on a Gen-6 NASCAR to the SAS and SRS predictions (both utilizing SST k−ω turbulence models). CFD simulations were performed with a finite-volume commercial CFD code, Star-CCM+ by Siemens, utilizing a high-resolution CAD model of the same vehicle. A direct comparison of the surface pressure distributions from the wind tunnel and CFD data clearly showed regions of high and low correlations. The associated flow features were studied to further explore the strengths and areas of improvement needed in the CFD predictions. While RANS was seen to be more accurate in terms of lift and drag, it was a result of the cancellation of positive and negative errors. Whereas IDDES overpredicted lift and drag and requires an order of magnitude more computational resources, it was able to capture the trend of surface pressure seen in the wind tunnel measurements.

Aerodynamics of vehicles account for nearly 80% of fuel losses on the road. Today, the use of the Intelligent Transport System (ITS) allows vehicles to be guided at a distance close to each other and has been shown to help reduce the drag coefficients of the vehicles involved. In this article, the aim is to investigate the effect of distances between a three car platoons, to their drag and lift coefficients, using computational fluid dynamics. To that end, a computational fluid dynamics (CFD) simulation was first performed on a single case and platoon of two Ahmed car models using the STAR-CCM+ software, for validation with previous experimental studies. Significant drop in drag coefficients were observed on platoon models compared to a single model. Comparison between the k-w and k-e turbulence models for a two car platoon found that the k-w model more closely approximate the experimental results with errors of only 8.66% compared to 21.14% by k-e turbulence model. Further studies were undertaken to study the effects of various car gaps (0.5L, 1.0L and 1.5L; L = length of the car) to the aerodynamics of a three-car platoon using CFD simulation. Simulation results show that the lowest drag coefficient that impacts on vehicle fuel savings varies depending on the car's position. For the front car, the lowest drag coefficient (CD) can be seen for car gaps corresponding to X1 = 0.5L and X2 = 0.5L, where CD = 0.1217, while its lift coefficient (CL) was 0.0366 (X1 and X2 denoting first to second and second to third car distance respectively). For the middle car, the lowest drag coefficient occurred when X1 = 1.5L and X2 = 0.5L, which is 0.1397. The lift coefficient for this car was -0.0611. Meanwhile, for the last car, the lowest drag coefficient was observed when X1 = 0.5L and X2 = 1.5L, i.e. CD = 0.263. The lift coefficient for this car was 0.0452. In this study, the lowest drag coefficient yields the lowest lift coefficient. The study also found that for even X1 and X2 spacings, the drag coefficient increased steadily from the front to the last car, while the use of different spacings were found to decrease drag coefficient of the rear car compared to the front car and had a positive impact on platoon driving and fuel-saving.

In this paper the influence of ground effect on the aerodynamic character of NACA 6409 were numerically studied. The simulations of the wing were performed by three dimensional Computational Fluid Dynamic (CFD). The important aerodynamic characters such as lift and drag coefficient, lift to drag ratio were determined with variation in some principle aerodynamic parameter, for instance the angle of attack and aspect ratio. The ground clearance ( h/c ) in CFD simulation was 0.1. This simulation showed that there was enhancement on lift coefficient and reduction on drag coefficient related to incremental of aspect ratio when a aircraft flying in proximity to the ground. The κ‐ε turbulent model was used in CFD model. Numerical results were compared with experimental data of another researcher. As a application of this CFD simulation was calculating the lift‐drag coefficient and lift to drag ratio from middle wing of WIG Catamaran.

Multidisciplinary aerodynamic-structural design optimization of supersonic fighter wing using response surface methodology

PurposeFanwing airfoil is a new lift‐generating section invented in 1997 by Patrick Peebles. The early shape of the airfoil has not changed until now. So far, no research has been done to change or modify the airfoil shape in order to improve its aerodynamic performance. In this paper, possibility of changing the airfoil shape to improve its aerodynamic performance is studied. For this purpose, six different geometric shapes of the airfoil are investigated numerically to determine the best airfoil on the basis of lift and drag coefficients. Flow over the airfoil is solved by developing a computational fluid dynamics (CFD) code. The purpose of this paper is to find a more efficient configuration for the Fanwing airfoil with lower power consumption and better performance.Design/methodology/approachFlow over the airfoil is investigated by CFD. At the airfoil solid walls, the no slip condition is applied. Re‐Normalization Group k‐ε model is used for turbulence modeling. The pressure‐velocity coupling is calculated by the SIMPLEC algorithm. Second‐order upwind discretization is considered for the convection terms. Finite volume method with rectangular computational cells is used for the entire solution domain.FindingsIt is observed that the airfoil with curved bottom wall and a slot in upper wall has the maximum lift coefficient. Also, the airfoil with curved bottom wall and no slot has the minimum drag or maximum thrust (negative drag) coefficient. Therefore, instead of increasing the airfoil lift or decreasing its drag by enhancing driving motor speed with larger energy consumption, this can be done only by changing the airfoil shape. It is perceived that the airfoil lift coefficient can be augmented at least 10 percent and its drag can be reduced more than 2.8 percent only by changing its shape and no excessive power consumption. Since the airfoil shape is modified, these advantages are permanent and its benefits are cumulative through time. Eccentric vortex inside the cross flow fan that is reported earlier in the research paper is found in this airfoil, too. In addition, velocity vectors, contours of static pressure and distribution of the static pressure over the airfoils surfaces are illustrated for better understanding of the flow details.Research limitations/implicationsSince the airfoil shape is very complicated for numerical study, two‐dimensional simulation has been carried out. Also, flow over the airfoil is considered steady‐state and incompressible.Practical implicationsIn this paper, some modifications for the Fanwing airfoil are suggested in order to improve its aerodynamic performance. This is the first research for changing the configuration of the Fanwing airfoil and can be very helpful for the researchers involved in this topic as well as aerospace industries.Originality/valueThis paper is valuable for researchers in the new and up to date concept of the Fanwing airfoil. This work is original.

The aerodynamic behavior of small-scale wind turbines is primarily influenced by blade geometry and airfoil selection. This study investigates the aerodynamic performance of a four-bladed horizontal-axis wind turbine (HAWT) using the NACA 4412 airfoil through numerical simulation in Q Blade software. The rotor features a tapered blade with a radius of 0.3 m and a pitch angle of 7°, operating at an average wind velocity of 3.6 m/s. Simulations were conducted based on Blade Element Momentum (BEM) theory to analyze variations in lift coefficient (Cl), drag coefficient (Cd), moment coefficient (Cm), and power coefficient (Cp) over different angles of attack and rotational conditions. The results show that the NACA 4412 airfoil exhibits favorable aerodynamic characteristics at moderate angles of attack, with a maximum lift coefficient of approximately 1.6 and a peak lift-to-drag ratio (Cl/Cd) of around 120 at α ≈ 8°. Pressure distribution analysis indicates minimal flow separation and stable suction behavior along the upper surface, contributing to efficient lift generation. The variation of Cl and Cd over a full rotational cycle reveals periodic but smooth aerodynamic loading, suggesting stable performance and low drag fluctuation. Overall, the airfoil demonstrates high aerodynamic stability and efficiency, confirming its suitability for low-speed small-scale wind turbine applications.

This paper discusses the aerodynamics characteristics of Blended Wing Body — Baseline II E2, unmanned aerial vehicle aircraft. A computational method, Computational Fluid Dynamic (CFD) Star CCM+ software has been performed to obtain the aerodynamics characteristic of the BWB. The aerodynamic characteristics prediction of BWB-Baseline II E2 aircraft was obtained through CFD analysis using unstructured mesh and standard one — equation turbulence model, Spalart-Allmaras was selected in the investigations. Lift coefficient (CL), drag coefficient (CD) and moment coefficient (CM) were studied at flight condition of Mach 0.1 (∼34 m/s) at different angles of attack, α. The CFD results were compared with the experimental result. The results show the trend of lift curves are similar at the linear region (α = −10° to 7°) but at the higher angle of attack the trends become nonlinear. The drag coefficient for CFD simulations is greater than experimental result and there are differences in pitching moment curves between CFD simulation and experiment data which the experiment data shows a steep curve than simulation.

We compute the loads on a model-scale tidal turbine with Blade Element Momentum (BEM) theory and Computational Fluid Dynamics (CFD) simulations, and we compare the results with towing tank tests. CFD simulations are wall-resolved, steady, Reynolds-averaged Navier-Stokes simulations with a k − ω SST turbulence model, where only a 120◦ wedge domain with a single blade is resolved in a non-inertial frame of reference. We undertake a detailed uncertainty analysis to identify the sources of error. BEM uncertainty is computed with a Monte-Carlo approach based on the differences in the predictions of CFD and Xfoil for the sectional lift and drag coefficients,while CFD uncertainty is based on the errors due to the finite number of iterations and spatial resolution. The maximum error of CFD (8.0%) with respect to the experimental data is about half of that of BEM (15.5%) for the power (CP) and the thrust (CT) coefficients and both errors are within 4.1% for CFD and within 7.2% for BEM around the optimal tip-speed ratio (λ = 6.03). The BEM error is within the uncertainty associated with the imprecise knowledge of the sectional lift and drag coefficients. The sectional forces from CFD and BEM disagree at both the tip and the root, resulting in a substantial BEM underprediction of CP at high λ values (up to 15.5%), yet CT is well predicted (within 2.3%) at every λ. The CFD uncertainty is markedly smaller than the error, which is thus mostly due to a modelling error such as the turbulence model, the neglected effect of the support structure, the free surface, and the imprecise knowledge of the input conditions. Overall these results suggest that CFD provides both a maximum error and uncertainty that are substantially smaller than that of BEM, but both methods suffer from modelling errors that require further investigation.

Biologically-inspired micro air vehicles (MAVs) are miniature-scaled autonomous aircrafts which attempt to biomimic the exceptional maneuver control during low-speed flight mastered by insects. Flexible wing structures are critical elements of a nature-inspired MAV as evidence supports that the wings of aerial insects experience highly-elastic deformations that enable insects to proficiently hover and maneuver in different airflow conditions. For this study, a crane fly (family Tipulidae) forewing is selected as the target specimen to replicate both its structural integrity and aerodynamic performance. The artificial insect-sized wing is manufactured using photolithography with negative photoresist SU-8 to fabricate the vein geometry. A Kapton film is attached to the vein pattern for the assembling of the wing. The natural frequencies and mode shapes of the artificial wing are determined to characterize its vibrations. A numerical simulation of the fluid-structure interaction is conducted by coupling a finite element model of the artificial wing with a computational fluid dynamics model of the surrounding airflow. From these simulations, the deformation response and the coefficients of drag and lift of the artificial wing are predicted for different freestream velocities and angles of attack. The deformation along the span of the wing increases nonlinearly with Reynolds number from the root to the tip of the wing. The coefficient of lift increases with angle of attack and Reynolds number. The coefficient of drag decreases with Reynolds number and angle of attack. The aerodynamic efficiency, defined as the ratio of the coefficient of lift to the coefficient of drag, of the artificial wing increases with angle of attack and Reynolds number.

In this study, a numerical investigation into the sustained aerodynamic performance of a morphing wing equipped with a flexible leading edge, employing a 2-dimensional NACA0012 airfoil configuration, is conducted. The compressible governing equations of the flow are employed, simulating 2 distinct states: the airfoil without motion and the airfoil featuring a flexible leading edge with a chord length of 0.856 m, assessing various angles of attack utilizing the k-ω SST turbulence approach within Fluent software. Dynamic mesh, facilitated by a user-defined function, is utilized in Fluent software to simulate the movement of the airfoil wall at the leading edge. The study thoroughly analyzes the flow behavior concerning diverse angles of attack and deviations, evaluating their impact on aerodynamic coefficients, velocity, and pressure fields under steady-state settings. Validation of the chosen numerical approach demonstrates close alignment of the front and back coefficients with experimental settings. Outcomes from the steady-state flow simulation of the morphing wing reveal that positive deflection angles correspond to increased lift coefficients and decreased drag coefficients, with lift coefficient increases of up to 15% and drag coefficient reductions of up to 10% at specific angles. Meanwhile, the negative deflection angles have shown a decline in lift coefficients, with the drag coefficients increasing with the decrease in deflection angle. All these observations show that at the flexible leading edge, there is a considerable improvement in aerodynamic efficiency. Hence, it should find more applications in different regimes of flight.

In developing successful airship designs, it is important to fully understand the effect of the design on the performance of the airship. The aim of this research work is to establish the trend for effects of design fineness ratio of an airship towards its aerodynamic performance. An approximate computer-aided design (CAD) model of the Atlant-100 airship is constructed using CATIA software and it is applied in the computational fluid dynamics (CFD) simulation analysis using Star-CCM+ software. In total, 36 simulation runs are executed with different combinations of values for design fineness ratio, altitude and velocity. The obtained simulation results are analyzed using MINITAB to capture the effects relationship on lift and drag coefficients. Based on the results, it is concluded that the design fineness ratio does have a significant impact on the generated aerodynamic lift and drag forces on the airship.

This paper presents the aerodynamic performance of Baseline V blended wing-body aircraft via Computational Fluid Dynamic (CFD) simulation. Baseline V has a set of close-coupled tail plane that can change its incidence and tilt angle for pitch and yaw control. Based on previous research, Baseline V has insufficient longitudinal stability in term of pitch moment at zero angle of attack which is negative value at zero tail incidence angles. When tail incidence is set at −10°, the moment coefficient at zero angle of attack is zero thus not sufficient for trim flight with stable pitch moment slope. This leads to the idea of sweeping the tail of the aircraft to increase moment arm. In this paper, two cases are considered which is 0° (case I) and 30° (case II) tail sweep angle in which both cases have tail incidence at −10°. NUMECA suit is used as computational tool for this simulation. The simulated environment consists of half-model Baseline V BWB in domain 20 times the length of the aircraft with body centre plane acts as a mirror. The angle of attack used for this simulation is between -10° to +17° while airspeed is fixed at 15m/s or Mach 0.05. Due to aircraft’s small mean chord and low airspeed flight, its Reynold number is low at 1.0 x 105 even at its body chord. Therefore, Laminar Navier-Stoke Equation is used for the computational simulation. Lift, drag and pitch moment coefficients with respect to angle of attack for both tail cases are computed from the simulation. The results from the CFD simulation is then compared with wind tunnel experiment results measured at AEROLAB, Universiti Teknologi Malaysia. The result shows that the trends of lift, drag and moment coefficients against angle of attack obtained from CFD simulations are similar to plots obtained from wind tunnel experiment for both tail sweep angle cases. It is found that tail sweep angle case of 30° has slightly less lift but higher drag coefficients compared with 30° tail sweep angle case while its pitch moment coefficient at zero angle of attack has now improved to allow positive trim angle of attack. However, the former has much lower maximum lift-to-drag ratio than the latter. Â

The aerodynamic performance of a three-wheeled vehicle was analysed using a Computational Fluid Dynamics (CFD) approach to evaluate its drag coefficient (Cd) and lift coefficient (Cl) under varying flow and environmental conditions. The study investigates the effects of velocity, air temperature, and density on aerodynamic forces, providing insights into their influence on vehicle stability and efficiency. A parametric analysis was conducted over a range of velocities (1–100 m/s), temperatures (223–328 K), and air densities corresponding to different altitudes (-1000 m to 80,000 m). The results indicate a direct correlation between velocity and aerodynamic forces, with Cd and Cl increasing non-linearly at higher speeds. Conversely, temperature variations showed negligible impact on aerodynamic performance, while decreasing air density at higher altitudes significantly reduced drag and lift forces. Additionally, a grid independence test was performed to ensure numerical accuracy, confirming that mesh refinement beyond a critical threshold yielded minimal variation in results. The three-dimensional model of the vehicle was developed in Fusion 360, and CFD simulations were conducted using ANSYS to assess aerodynamic behavior. The findings highlight the potential for aerodynamic optimization in three-wheeled vehicle design, emphasizing the need for refined body shaping and flow management strategies to enhance efficiency and stability. The motivation behind selecting a three-wheeled vehicle lies in its growing adoption for urban mobility, given its lightweight structure, lower manufacturing costs, and energy efficiency. However, its aerodynamic characteristics remain a critical factor in ensuring stability, particularly at higher speeds. This study highlights the potential for aerodynamic optimization in three-wheeled vehicle design, emphasizing the need for refined body shaping and flow management strategies to enhance efficiency and stability. This study serves as a foundation for future aerodynamic improvements in alternative vehicle designs, contributing to advancements in energy-efficient transportation.

In this work, a framework to perform high fidelity Computational Fluid Dynamics (CFD) analysis of dynamically morphing airfoils and wings is presented. An unsteady parametric method to model the deforming motion is proposed and then implemented in a User-Defined Function (UDF). The UDF is used for driving dynamic mesh in ANSYS Fluent. First, the framework is applied to a 2D airfoil equipped with a morphing Trailing-Edge Flap (TEF). A numerical validation of the steady and unsteady predictions is then performed against published data. Furthermore, the aerodynamic efficiency of the morphing concept is compared to an airfoil with a hinged TEF. It is found that an average of 6.5% increase in lift-to-drag ratio can be achieved with the morphed flap. The framework is then used to study the flow response to a 2D downward flap deflection at various morphing frequencies. The slope of time histories of lift and drag coefficients were found to be proportional to the morphing frequency during the morphing phase. Contrary to the lift, however, the drag experiences an overshoot in its instantaneous values, resulting in efficiency loss for all frequencies before settling to a steady. This finding indicates the presence of unsteady effects that need to be taken into account during the design phase. Qualitative analysis reveals some similarities between rapid morphing and ramp-type pitching motion. The framework is developed further to study continuous active flow control using a harmonically morphing TEF and its effect on the aerodynamic performance and acoustic spectra. The parametric method is modified to model the low amplitude (0.1 and 0.01% of the chord) harmonic morphing (combined upward and downward motion) in the TEF and the Ffowcs-Williams and Hawkings acoustic analogy was used for noise prediction. For this part of the work, a hybrid Reynolds-averaged Navier–Stokes–Large Eddy Simulation (RANS-LES) model, Stress-Blended Eddy Simulation (SBES), is used. It is shown that the 0.1% morphing amplitude induces higher sound pressure levels around the morphing frequency, and that all the morphing cases induce a shift in the main tone to a higher frequency, with a 1.5 dB reduction in the sound pressure levels. Apart from noise abatement, it is found that for a morphing frequency of 800 Hz and 0.01% amplitude it is possible to achieve up to 3% increase in aerodynamic efficiency. Finally, a framework extension from 2D to 3D is proposed, by extending the parametrization method to model both the morphed TEF and the seamless flap side-edge transition between the morphing and static parts. A comparative study between a wing with a statically morphed flap and one with a hinged flap reveals that the morphed flap produces higher lift and lower drag resulting in an enhanced aerodynamic efficiency (CL/CD) of up to 40%. This enhanced efficiency is mainly due to the absence of gaps and the contribution of the seamless transition to lift generation. The unsteady analysis of the 3D dynamically morphed wing shows the presence of the drag overshoot, which is consistent with the 2D results. Finally, when comparing 2D and 3D CFD results, it is observed that 2D results tend to over-predict both the lift and drag. This is because 2D analysis assumes that the entire span is deflecting whereas the 3D wing would only have a portion of the flap deflecting. The framework established in this thesis can be easily applied to other types of airfoils, leading-edge morphing, as well as wind and tidal turbine blades.

PurposeThis paper aims to deal with the numerical investigation of laminar separation bubble (LSB) characteristics (length and height of the bubble) of SS007 airfoil at the chord Reynolds number of Rec = 0.68 × 105 to 10.28 × 105.Design/methodology/approachThe numerical simulations of the flow around SS007 airfoil were carried out by using the commercial fluid dynamics (CFD) software, ANalysis system (ANSYS) 15. To solve the governing equations of the flow, a cell-centred control volume space discretisation approach is used. Wind tunnel experiments were conducted at the chord-based Reynolds number of Rec = 1.6 × 105 to validate the aerodynamic characteristics over SS007 airfoil.FindingsThe numerical results revealed that the LSB characteristics of a SS007 airfoil, and the aerodynamic performances are validated with experimental results. The lift and drag coefficients for both numerical and experimental results show very good correlation at Reynolds number 1.6 × 105. The lift coefficient linearly increases with the increasing angle of attack (AOA) is relatively small. The corresponding drag coefficient was found to be very small. After the formation of LSB which leads to burst to cause airfoil stall, the lift coefficient decreases and increases the drag coefficient.Practical implicationsLow Reynolds number and LSB characteristics concept in aerodynamics is predominant for both civilian and military applications. These include high altitude devices, wind turbines, human powered vehicles, remotely piloted vehicles, sailplanes, unmanned aerial vehicle and micro aerial vehicle. In this paper, the micro aerial vehicle flight conditions considered and investigated the LSB characteristics for different Reynolds number. To have better aerodynamic performances, it is strongly recommended to micro aerial vehicle (MAV) design engineers that the MAV is to fly at 12 m/s (cruise speed).Social implicationsMAVs and unmanned aerial vehicles seem to give some of the technical challenges of nature conservation monitoring and law enforcement a versatile, reliable and inexpensive solution.Originality/valueThe SS007 airfoil delays the flow separation and improves the aerodynamic efficiency by increasing the lift and decreasing the drag. The maximum increase in aerodynamic efficiency is 12.5% at stall angle of attack compared to the reference airfoil at Re = 2 × 105. The results are encouraging and this airfoil could have better aerodynamic performance for the development of MAV.