Wing Flow Field Research Articles

Fast aerodynamic analysis method for three-dimensional morphing wings based on deep learning

Morphing wings have garnered widespread attention due to their superior aerodynamic efficiency. However, in the design process, accurately and efficiently obtaining the three-dimensional flow field of morphing wings remains a challenging issue. This paper proposes a Deep Learning-based method for predicting the flow field of a Biomimetic Morphing Wings to address this problem. Firstly, a Coordinate Transformation Mechanism is established for the studied Biomimetic Morphing Wing to ensure the consistency of grid point coordinates between different wing shapes. Secondly, a two-level Flow Field Prediction Model is constructed, consisting of grid point prediction level and physical quantity continuity adjustment level. Using this method, the flow field of the Biomimetic Morphing Wing was predicted, and the predication result were similar to those of numerical simulations. This indicates that the proposed method maintains high prediction accuracy while reducing computation time, thereby enhancing the analysis efficiency of the morphing wing's flow field.

KF-PEV: a causal Kalman filter-based particle event velocimetry

Event-based pixel sensors asynchronously report changes in log-intensity in microsecond-order resolution. Its exceptional speed, cost effectiveness, and sparse event stream make it an attractive imaging modality for particle tracking velocimetry. In this work, we propose a causal Kalman filter-based particle event velocimetry (KF-PEV). Using the Kalman filter model to track the events generated by the particles seeded in the flow medium, KF-PEV yields the linear least squares estimate of the particle track velocities corresponding to the flow vector field. KF-PEV processes events in a computationally efficient and streaming manner (i.e., causal and iteratively updating). Our simulation-based benchmarking study with synthetic particle event data confirms that the proposed KF-PEV outperforms the conventional frame-based particle image/tracking velocimetry as well as the state-of-the-art event-based particle velocimetry methods. In a real-world water tunnel event-based sensor data experiment performed on what we believe to be the widest field view ever reported, KF-PEV accurately predicted the expected flow field of the SD7003 wing, including details such as the lower velocity in the wake and the flow separation around the underside of an angled wing.

Numerical study of the effects of discontinuous ice on three-dimensional wings

Ice accretion has adverse effects on aircraft, so it is very important to study the flow field of iced wings. Unlike previous studies that typically focused on continuous ice, this paper conducts a numerical study of the flow field around discontinuous ice. A modified laminar-turbulent transition model that incorporates large separation correction is employed for the study of discontinuous ice. An iced swept wing was chosen to validate the modified model's capability in predicting aerodynamic performance. The impact of discontinuous ice on both straight and swept wings was studied. For the straight wing, the effect of discontinuous ice with different gap widths on aerodynamic characteristics was investigated. The results show that the reduction in lift caused by discontinuous ice is typically lower than that caused by continuous ice. However, at angles of attack less than 7°, small-gap discontinuous ice causes more substantial reductions in lift compared to continuous ice. This is because small-gap ice causes greater separation at the leading edge, significantly reducing the suction peak of pressure. For the swept wing, the effect of sweep on discontinuous ice was studied. It was found that the swept effect causes asymmetric separation behind the ice shape. At higher angles of attack (greater than 4°), the impact of different ice configurations on lift shows an opposite trend on swept wings compared to straight wings.

Research Progress in Numerical Simulation of Aircraft Wing Flow Field

Computational fluid dynamics has important application value and theoretical significance in engineering. Fluid mechanics has emerged as a way out of many engineering design problems. In recent years, applying fluid mechanics in the aircraft field has brought a breakthrough to problems that could not be solved previously. This paper mainly introduces the development history of the application of computational fluid dynamics in the direction of the wing and the specific application of this technology in the numerical simulation of the wing flow field. The aerodynamic characteristics of aircraft wings are related to the flight performance of the aircraft. The influence of wing aerodynamic characteristics, wing lift drag coefficient, and wing noise is a hot research issue. The influence of flow field research methods (such as numerical simulation) on the optimization and improvement process of the wing is analyzed, and the numerical results and simulation results of the flow field are found. The future development trend of the wing is proposed. Finally, it is believed that changes in airfoils will have a significant impact on aircraft performance.

Dynamic stall of pitching tubercled wings in vortical wake flowfield

In consideration of the turbulent inflow condition of engineering applications, the flow mechanisms of dynamic stall of a tubercled airfoil have been comprehensively analyzed with an upstream cylinder. Numerical simulation of the flowfield of a tubercled wing with NACA0021 (National Advisory Committee for Aeronautics) airfoil has been conducted with the large eddy simulation model. Then, flow mechanisms have been analyzed based on the aerodynamic performances and flow structure descriptions. Meanwhile, proper orthogonal decomposition (POD) analysis has been carried out at both trough and peak sections to reveal the flow dynamics. It turns out that the dynamic stall process vanishes, and performances would be obviously impacted by the incoming cylinder wake in the case of αA=5° due to the enforced resistance of adverse pressure gradient. Furthermore, the first leading POD mode corresponds to the pitching movement at both trough and peak sections, while the high-order modes represent the influence of cylinder wake. Eventually, the influence of pitching amplitude has also been discussed in the case of αA=15°. Different from the case of αA=5°, dynamic stall phenomenon emerges, and the influence of wake impingement could be barely detected from the mode information except for the third mode at the trough section. The detachment of the dynamic stall vortex takes place corresponding to the dynamic stall onset, which is driven by the streamwise pressure gradient near the trough leading-edge.

Numerical investigation of the quasi-vortex-ring state of the propulsive wing in vertical descent

A multi-axis propulsive wing aircraft is a new type of vertical takeoff and landing aircraft. When the aircraft descends vertically, it enters a quasi-vortex-ring state (QVRS) similar to the vortex-ring state of the rotor. Based on the computational fluid dynamics method, the sliding grid technique was used to simulate and analyze the QVRS of a single propulsive wing in vertical descent. First, a computational method for the propulsive wing flow field was established, and the variation laws of the aerodynamic forces of the propulsive wing were analyzed. Then, the change in the flow field structure and wake of the propulsive wing was further studied, and the evolution mechanism of the QVRS of the propulsive wing was explained. Finally, recovery strategies for the QVRS and windmill–brake state (WBS) of the propulsive wing were proposed. The simulation results show that when the descent speed is less than the critical speed, the propulsive wing enters the QVRS. The interaction between the propulsive wing wake and reverse airflow provides an aerodynamic amplification of up to 17.3%; thus, the propulsive wing has satisfactory safety in the QVRS. When the descent speed is greater than the critical speed, the propulsive wing enters the WBS and its aerodynamic force is almost zero. The aerodynamic force of the propulsive wing can be increased by increasing the rotational speed of the cross-flow fan. Then, the descent speed of the propulsive wing slows down and the propulsive wing recovers from the dangerous state.

Efficiency Enhancement Design Approach in the Side Wing of a FSAE Car Utilizing a Shutter-Like Fairing Structure

Aerodynamical design is one of the critical technologies in race car engineering, and favorable race car aerodynamics is supposed to provide sufficient negative lift force and keep the center of pressure in the vicinity of center of mass. Taking the Formula Society of Automotive Engineers (FSAE) cars as an example, side wing structure is frequently adopted for better grip in the mid-back of short wheelbase, open wheel race cars. This research designs a shutter-like fairing structure and utilizes it to weaken the vorticity and reinforce the pressure of side wing flow field. The sensitivity of side wing aerodynamic efficiency to shutters’ key parameters is analyzed, and optimized shutters’ key parameters for a prototype FSAE race car are obtained through computational fluid dynamics simulations. Results indicate that over 10% enhancement in side wing aerodynamic efficiency can be achieved by applying optimized shutters.

Numerical study on aerodynamic characteristics of two-dimensional propulsive wing in cruise and hover

The propulsive wing vehicle is a new concept vehicle, which is driven by a cross-flow fan (CFF) embedded in the trailing edge of the wing. The propulsive wing vehicle is capable of cruising and hovering at high angles of attack with very high aerodynamic force coefficients, and has the potential to become a new type of vertical take-off and landing (VTOL) vehicle. The cruise and hover states of the propulsive wing vehicle are defined, and a numerical model of the two-dimensional propulsive wing is established. Based on the computational fluid dynamics (CFD) method, the rotation of the CFF is simulated by using the sliding mesh technique. The effects of cruise speed, angle of attack and CFF rotation speed on the aerodynamics of the two-dimensional propulsive wing are evaluated, and the mechanism of the propulsive wing flow field changes is revealed. The results show that the propulsive wing has a very high lift coefficient of up to 60 at low speed and high angle of attack cruise, and a high thrust coefficient of up to 40 at low speed and small angle of attack cruise. The aerodynamic force of the propulsive wing fluctuates periodically with the rotation of the CFF, and the amplitude of the fluctuation is related to the vorticity of the CFF blade shedding vortex. In hover, the flow field of the propulsive wing is affected by the geometry and wake deflection into an asymmetric distribution, forming a vortex on each side of the airfoil, and the vortex diameter varies with the CFF rotation speed, which in turn has an impact on the hovering performance of the propulsive wing.

Low-Reynolds-Number Flowfield of Wing with Control Surface in Propeller Slipstream

An experimental study is conducted on a NACA 0012 airfoil with a control surface to investigate the influence of a propeller slipstream under a low-Reynolds-number condition. To investigate the influence of the propeller slipstream on a wing surface, the flowfield on the wing surface is visualized using a temperature-sensitive paint when the chord-based Reynolds number is equal to . The control surface performance improves in the installed-propeller condition because the propeller slipstream suppresses the laminar separation bubble. Finally, we suggest that the propeller should be installed ahead of the control surface to benefit from the effect of the propeller slipstream under the low-Reynolds-number flight condition.

A review of installation effects of ultra-high bypass ratio engines

The adoption of ultra-high bypass ratio (UHBPR) engines has been long recognised to bring about reduction of specific fuel consumption and noise emission. In the need to fulfil ambitious environmental targets and mitigate the aviation sector impact, they represent a smoother technology change, compared to futuristic aircraft designs featuring electric, distributed and boundary layer ingesting propulsion. However, the challenges related to UHBPR adoption can prevent a real system performance improvement, due to interdependent counteracting factors and enhanced interference between engine and airframe. This paper reviews the installation effects on underwing-mounted UHBPR turbofan engines, first presenting the cycle design studies and how they are affected by considering integration. The advancements in nacelle components modelling and optimisation are then reviewed, where new numerical models, statistical methods and optimisation algorithms are employed to tackle the inherently multi-objective problems. The computational estimation of installation effects and the studies on optimal engine position are also presented, highlighting the overall effect on the aerodynamic characteristics. Finally, the wind tunnel tests using powered engine simulators are discussed. The tools developed to quantify the thrust and drag figures of installed propulsors and obtain indications on their best underwing location now allow quite accurate estimations, both in numerical and experimental simulations. The higher level of interaction and the increased mutual sensitivity of engine operation and wing flow field, however, suggest the need to elaborate closely coupled methods to correctly replicate these effects and an assessment of current wind tunnel practices for the design and operation of powered engine simulators.

Numerical investigation of the effects of different parameters on the thrust performance of three dimensional flapping wings

After billions of years of evolution, many creatures employing flapping wing in nature tend to have excellent flight capabilities. To understand the bionic wings flow mechanism will be helpful to design high performance underwater vehicles and new conception aircrafts. The geometric parameters, kinematic parameters and flow parameters have great effects on the bionic wings thrust performance. Facing the diverse parameters, it's very difficult to explore the three-dimensional (3D) bionic flapping wing flow mechanism with traditional numerical simulation method. In this paper, a general large-scale parallel solver using Immersed Boundary-Lattice Boltzmann Method (IB-LBM) was developed. The evolution procedures of the 3D flapping wing leading edge vortex and wake flow vortex structures were analyzed in detail. Our study explained the 3D flapping wing thrust performance variation with different wing shapes, aspect ratios and pitch-bias angles of attack. Using Chinese supercomputer TianHe-II presents a wide range of possibilities for the further development of parallel IB-LBM, employing tens of millions grids will help us to obtain more complete and accurate 3D flapping wing flow field information. It's indicated that the obtuse wing has the best thrust performance compared with other sharp wing shapes. With the increase of the aspect ratio, the thrust coefficient of flapping wing increases firstly and then decreases, and with pitch-bias angles of attack increases, the thrust coefficient decreases quickly or even shown resistance phenomenon at the large pitch-bias angel of attack. The discussion of these parameters will provide a theoretical basis for improving flapping-like vehicles propulsive performance.

Aerodynamic characteristics and flow field of delta wings with the canard

Now, many kinds of explorations for outer planets have been proposed around the world. Among them Mars attracts much attention for future exploration. Orbiters and landers have been used for Mars exploration. Recently as a new exploration method, the usage of an airplane has been seriously considered and there are some development projects for Mars airplane. However, the airplane flying on the Earth atmosphere cannot fly on the Mars atmosphere, because atmospheric conditions are much different each other. Therefore, we focused on the usage of the airplane with unfolding wings for Mars exploration. These unfolding wings are designed as delta wings. However, delta wings do not have enough aerodynamics characteristics in a low speed region. In this study, to improve the aerodynamic characteristics of delta wings, we have proposed the usage of canard wings. The purpose of this study is to examine the effectiveness of canard wings to improve aerodynamic characteristics in a low speed region. CFD analysis is performed using four wing models with different canard shapes. The result shows that the usage of canards is effective to improve aerodynamic characteristics of delta wings in a low speed region. In addition, increasing lift coefficient is possible by changing the shape of canards.

Effect of anhedral on a reverse delta wing

The effect of anhedral on the vorticity flowfield and aerodynamic loadings of a slender reverse delta wing was studied experimentally. The addition of anhedral always led to a reduced lift and lift-to-drag ratio in comparison with their clean-wing counterparts. The drag was increased with increasing anhedral compared to the clean wing at the same lift condition. The reverse delta wing vortex retained its regularity to a higher angle of attack as the anhedral was increased. The persistent outboard location of the reverse delta wing vortex suggests that the lift force was mainly produced by the pressure exerted on the bottom surface of the wing. The anhedral also led to an increased vorticity level and tangential velocity.

低雷诺数下翼型绕流的LBM数值模拟

Lattice Boltzmann Method (LBM)是一种近年来发展的基于分子动理论的数值方法，它具有计算简单、边界易于处理的特点。本文基于采用D2Q9模型的LBM方法对NACA0012翼型进行了数值模拟与分析，数值结果表明：对于简单翼型的低雷诺数、非定常湍流流场，LBM方法的数值结果与CFL3D参考值可以很好的吻合。因而，该方法对于低雷诺数下简单翼型流场计算是一种有效的计算手段。 Lattice Boltzmann Method (LBM) is a numerical method based on molecular dynamics theory de-veloped in recent years. It has the characteristics of simple calculation and easy boundary treat-ment. In this paper, the flow with low Reynolds number for NACA0012 airfoil were analyzed and simulated based on LES method with D2Q9 model. The numerical results show that the numerical results of the LBM method fairly agree with the reference value of CFL3D for the low Reynolds number and the unsteady turbulent flow field of the simple airfoil. Thus, this method is effective for calculating the wing flow field at low Reynolds number.

AVT-183 diamond wing flow field characteristics Part 1: Varying leading-edge roughness and the effects on flow separation onset

Experimental investigations on a 53° leading-edge sweep diamond wing configuration with rounded leading-edge contour are presented. The analyses pertain to recent work that was conducted within the NATO Science and Technology Organization (STO) task group AVT-183 (Applied Vehicle Technology panel). The results were obtained in a low-speed wind tunnel facility and include aerodynamic forces and moments, and time-averaged surface pressures. Special emphasis is placed on the effects of different surface roughness, which was applied in the experimental analyses at the wing leading edge to fix turbulent boundary-layer characteristics. The results show that the flow separation onset and the emerging leading-edge vortex are very sensitive to the roughness height and any leading-edge contour modification. Compared to the free transition case, both reasonably-tripped and over-tripped cases are obtained, which is discussed in detail. Moreover, measurement repeatability issues are reviewed from a short-term and a long-term perspective. As an outcome, one specific leading-edge roughness is selected for the target flow conditions, which provided the baseline for subsequent flow field investigations and general CFD validation within the task group AVT-183.

AVT-183 diamond wing flow field characteristics Part 2: Experimental analysis of leading-edge vortex formation and progression

Experimental flow field investigations are presented on a 53° leading-edge sweep diamond wing configuration with rounded leading-edge contour. The analyses pertain to recent work that was conducted within the NATO Science and Technology Organization (STO) task group AVT-183 (Applied Vehicle Technology panel). The results obtained in a low-speed wind tunnel facility depict the overall aerodynamic characteristics as function of the angle of attack, and mean and turbulent flow field characteristics at one specific angle of attack, namely α=12°. Both Stereo Particle Image Velocimetry and Hot-Wire Anemometry are applied to detect the emerging flow phenomena in several chordwise sections including near-wall data. Details of the leading-edge vortex formation and progression are analyzed and discussed. Over almost the entire length of its existence, the leading-edge vortex is characterized by retarded axial flow, thus showing vortex bursting tendencies. The corresponding turbulent fluctuations show maxima close to the evolution of the leading-edge vortex and decrease towards the trailing edge. The observed flow separation onset and progression are significant for the AVT-183 diamond wing configuration, and more generally for a moderately-swept low-aspect-ratio wing with rounded leading-edge contour. Following, the derived flow field characteristics provide a high-quality data base, which is suitable for general CFD validation.

小展弦比薄机翼精细化气动优化设计研究

For aerodynamic design of figher wings with the feature of small aspect ratio, the plat shape, camber-twist and thickness modification are mainly concerned and refined design of the airfoil is neglected. Therefore, Euler equation combined with boundary layer is the main technique to calculate the aerodynamic characteristics. Taking a typical fighter wing as an example, Euler equation and RANS equation are respectively utilized to calculate the flow field of the figher wing. From the result, the flow details cannot be captured by Euler equation which reveals that Euler equation is not qualified for refined design of figher wing. Airfoil aerodynamic design optimization is carried out and it is inferred that the results of airfoil design does not hold in small aspect ratio wing. Therefore, for small aspect ratio wing, airfoil design optimization must be conducted in 3-D circumstance. A 3-D aerodynamic design optimization frame is built which consists of FFD parameterization method, robust mesh deformation technique, Kriging surrogate model and PSO optimization algorithm. Employing the optimization frame, a single objective design is carried out at transonic state and a multi objective design is conducted at transonic/supersonic states. Aerodynamic characteristics are greatly improved from the design results.

Unsteady Aerodynamic Response of a Rapidly Started Flexible Wing

Effects of camber and camber-change due to elastic deflection for aspect ratio 4.25 wings were examined for the classical unsteady problem of rectilinear translational acceleration. Direct force measurements and flow visualization by laser illumination of fluorescent dye allowed for the tracking of force history vs. evolution of the flowfield of rigid flat, rigid cambered, and flexible membranous wings. At low incidence (10 degrees and below), Wagner's approximation provides an accurate prediction of the time-evolution of lift for the rigid wings, beyond which flow separation leads to peaks in the force history and the camber-effect is no longer additive to the incidence effect. Both the rigid uncambered and cambered wings reach peak lift at 35 degrees, whereas the flexible wing experiences a form of stall-delay and reaches peak lift at 50 degrees. Due to the aeroelasticity of the flexible membrane, flow over the suction surface remains attached for much higher incidence angles than for the rigid wings. For incidence angles less than 30 degrees, the flexible wing's peak lift is lower than that of its rigid counterparts. However, beyond 30 degrees, the flexible wing experiences an aeroelastically-induced stall delay that allows lift to exceed the rigid analogs.

The visualization experiment and theoretical analysis of the flow field of honeybee flapping-wing

The goal of this study is to show characteristics of flow field of honeybee wings' flapping with performing multiple sets of flow visualization experiment in low-speed smoke tunnel. Periodic flow field structures of far and near field of the honeybee were imaged using high-speed camera,and leading edge vortex,trailing edge vortex and wing tip vortex were analized.At the trailing edge of the wing, the downstroke stopping vortex and upstroke starting vortex were generated at the end of the down stroke. Both the forewing and hindwing could flex and rotate at the stroke reversal, leading the circular rectors of the trailing edge vortex of the forewing and hindwing to be in the opposite direction. The size of the leading edge vortex was increasing from wing root to wing tip, and the spanwise flow structure was composed of leading edge vortex and trailing edge vortex. At the end of the down stroke, the scroll generated by the wing tip vortex was connected with the wing margin circular rector, respectively forming the independent vortex rings on right and left wings. Meanwhile downstroke lift was estimated utilizing the vortex ring theory.

The aerodynamic performance of flexible wing in plunge

Inspired by the fact that flexible wing in nature possesses advance aerodynamic performance, a numerical experiment is applied to investigate the aerodynamic performance of flexible wing in plunge motion, where the incompressible Navier-Stokes (N-S) equations coupled with the structural dynamic equation for the motion of the wing is solved. A two-dimensional, elastic and inextensible beam model wing is considered at Re = 1256. The harmonic plunge motion is specified at the leading edge of wing, and the other part of wing is responded passively deforming by the aerodynamic force. By analyzing the flow field, aerodynamic force and energy efficiency of different flexibility wings, it is found that the flexibility influences the aerodynamic characteristics of the plunge wing greatly and when the plunge frequency is less than the structural frequency the flexibility can increase the thrust force and the energy efficiency of the wing, and the maximum energy efficiency is obtained when the wing plunge near the resonance. Moreover, a lighter wing possesses larger energy efficiency than a heavier wing, but it may not be functioning for too light wing. The results obtained in this study will provide physical insight into the understanding of fluid and structure interaction problem.