Shock Reduction through Opposing Jets—Aerodynamic Performance and Flight Stability Perspectives

In this research paper, investigations of counter flow (opposing) jet on the aerodynamic performance, and flight stability characteristics of an airfoil with blunt leading-edge in supersonic regime are performed. Unsteady Reynolds-Averaged Navier-Stokes ( U R A N S ) based solver is used to model the flow field. The effect of angle of attack ( α ), free-stream Mach number ( M ∞ ), and pressure ratio ( P R ) on aerodynamic performance of airfoil with and without jet are compared. The results indicate that the opposing jet reduces drag from 30 % to 70 % , improves the maximum lift-to-drag ratio from 2.5 to 4.0, and increases shock stand-off distance from 15 % to 35 % depending on flow conditions. The effect of opposing jet on longitudinal flight stability characteristics, studied for the first time, indicate improvement in dynamic stability coefficients ( C m q + C m α ˙ ) at low angles of attack. It is concluded that the opposing jet can help mitigate flight disturbances in supersonic regime.

Download Full-text

Modification impact on aerodynamic performance of hypersonic waverider

The Aeronautical Journal ◽

10.1017/s0001924000005844 ◽

2011 ◽

Vol 115 (1168) ◽

pp. 325-334 ◽

Cited By ~ 3

Author(s):

C. Xiao-Qing ◽

H. Zhong-Xi ◽

L. Jian-Xia ◽

G. Xian-Zhong

Keyword(s):

Leading Edge ◽

Aerodynamic Performance ◽

Hypersonic Vehicles ◽

Flow Conditions ◽

Aerodynamic Coefficient ◽

High Lift ◽

Computational Fluid Dynamics Cfd ◽

Drag Ratio ◽

Lift To Drag Ratio ◽

Sharp Leading Edge

Abstract Waverider serves as a good candidate for hypersonic vehicles. The typical waverider has sharp leading edge and no control face, which is inappropriate for practical use. This paper puts forward a method modifying the waverider, and the modification impact on the performance of waverider at hypersonic flow conditions is studied. The modification is based on blunted waverider, includes cutting the tip and introducing two control wings. The modification’s effect on aerodynamic performance is obtained and analysed through Computational Fluid Dynamics (CFD) techniques. When blunted with 2cm radius, the waverider retains its good aerodynamic performance and the heat flux at the stagnation point can be managed. Three factors of the introduced wing are argued, the fixed angle, aspect ratio and wing area. Results show that influence on the aerodynamic coefficient is slight and the vehicle retains its high lift-to-drag ratio. The main influences of the modification are the control ability and trim efficiency, which is the motivation of this work and can be adapted when designing a practical waverider.

Download Full-text

Multi-objective aerodynamic optimization design of variable camber leading and trailing edge of airfoil

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211056012 ◽

2021 ◽

pp. 095440622110560

Author(s):

Nvzi Bao ◽

Yehui Peng ◽

Heying Feng ◽

Chenghao Yang

Keyword(s):

Neural Network ◽

Deep Neural Network ◽

Rotation Angle ◽

Angle Of Attack ◽

Leading Edge ◽

Aerodynamic Performance ◽

Trailing Edge ◽

Drag Ratio ◽

Lift To Drag Ratio ◽

2D Airfoil

Variable camber is an effective method for improving the flight efficiency of large aircraft, and has attracted the attention of researchers. This work focused on the optimization of a variable camber airfoil. First, the influences of the variable camber of the leading and trailing edges on the airfoil aerodynamic performance were investigated using a computational fluid dynamics numerical simulation. An initial database was established for a deep neural network. Second, an iterative algorithm was constructed to optimize the variable camber airfoil in terms of the rotation angle of the leading edge, deflection position of the leading edge, rotation angle of the trailing edge, and deflection position of the trailing edge. A genetic algorithm was used in each iteration to maximize the lift coefficient and lift-to-drag ratio, as predicted using a deep neural network (DNN). The optimal results were validated using Fluent. If the DNN result approximated the Fluent results, the iterative process was stopped. Otherwise, the Fluent results were inserted into the database to update the DNN prediction model. The optimization results showed that the lift-to-drag ratio of the 2D airfoil could be increased by more than 14 when the angle of attack was less than 8° relative to the original airfoil. Furthermore, to validate the 2D optimal results, the optimized 2D airfoil was stretched into 3D, and it was discovered that the aerodynamic performance trend of the 3D airfoil with respect to the angle of attack was basically the same as that of the 2D airfoil. In addition, the corresponding 3D airfoil improved the aerodynamic performance and reduced the noise at a high frequency (by approximately 16 dB). In contrast, the noise in the low and medium frequencies remained unchanged. Therefore, the optimization method and results can provide a reference for the aerodynamic design and acoustic design of large civil aircraft wings.

Download Full-text

Effects of Bending of Fluidic Oscillators on Aerodynamic Performance of an Airfoil with a Flap

Processes ◽

10.3390/pr9081429 ◽

2021 ◽

Vol 9 (8) ◽

pp. 1429

Author(s):

Nam-Hun Kim ◽

Kwang-Yong Kim

Keyword(s):

Pitch Angle ◽

Stokes Equations ◽

Peak Velocity ◽

Velocity Ratio ◽

Lift Coefficient ◽

Aerodynamic Performance ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Drag Ratio ◽

Lift To Drag Ratio

The present work investigated the effects of bending the outlet nozzles of fluidic oscillators installed on the NACA0015 airfoil with a flap on the flow control performance and, thus, the aerodynamic performance of the airfoil. The effects of bending on fluidic oscillators have not been reported so far in previous works. The aerodynamic analysis was performed numerically using unsteady Reynolds-averaged Navier-Stokes equations. Three different cases were considered: Case 1 changes only the bending angle with a fixed pitch angle, Case 2 changes only the pitch angle without bending, and Case 3 changes both the bending and pitch angles. Although the bending of the oscillators was introduced inevitably due to a geometrical limitation in the installation, the results indicated that the bending rather improved the lift coefficient and lift-to-drag ratio of the airfoil by improving the characteristics of the fluidic oscillators, such as the jetting angle and peak velocity ratio.

Download Full-text

Numerical study on aerodynamic performance of waverider with a new bluntness method

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410020968419 ◽

2020 ◽

pp. 095441002096841

Author(s):

Zhipeng Qu ◽

Houdi Xiao ◽

Mingyun Lv ◽

Guangli Li ◽

Cui Kai

Keyword(s):

Numerical Study ◽

Leading Edge ◽

Aerodynamic Characteristics ◽

Aerodynamic Performance ◽

The Novel ◽

High Lift ◽

Wide Range ◽

Drag Ratio ◽

Lift To Drag Ratio ◽

Sharp Leading Edge

Abastrct The waverider is deemed the most promising configuration for hypersonic vehicle with its high lift-to-drag ratio at design conditions. However, considering the serious aero-heating protection, the sharp leading edge must be blunted. The existing traditional bluntness methods including the following two types: “reducing material method” and “adding material method”. Compared to the initial waverider, the volume will be smaller or larger using the traditional methods. With the fixed blunted radius, the volume and aerodynamic performance is determined. In this paper, a new bluntness method which is named “mixing material method” is developed. In this new method, a new parameter is introduced based on the traditional two bluntness methods. Under fixed blunted radius, the volume and aerodynamic performance can be changed within a wide range by adjusting the parameter. When the parameter is 0 and 1, the novel blunted method degenerated into the “reducing material method” and “adding material method” respectively. The influence of new parameter on the aerodynamic characteristics and volume are studied by numerical simulation. Results show that the volume, lift and lift-to-drag ratio increases with the increase of the parameter under the fixed blunt radius, but simultaneously, the drag will also increase. Therefore, considering the different requirements of the air-breathing hypersonic aircrafts for the balance of thrust and drag, lift and weight, a suitable bluntness parameter can be selected to achieve a balance. This research can provide reference for hypersonic waverider vehicle design.

Download Full-text

Aerodynamic Analysis of an Airfoil With Leading Edge Pitting Erosion

Journal of Solar Energy Engineering ◽

10.1115/1.4037380 ◽

2017 ◽

Vol 139 (6) ◽

Cited By ~ 2

Author(s):

Yan Wang ◽

Ruifeng Hu ◽

Xiaojing Zheng

Keyword(s):

Wind Turbine ◽

Indirect Effects ◽

Leading Edge ◽

Aerodynamic Performance ◽

Navier Stokes ◽

Distribution Area ◽

Navier Stokes Equation ◽

Turbine Performance ◽

Wind Turbine Airfoil ◽

Cfd Method

Leading edge erosion is a considerable threat to wind turbine performance and blade maintenance, and it is very imperative to accurately predict the influence of various degrees of erosion on wind turbine performance. In the present study, an attempt to investigate the effects of leading edge erosion on the aerodynamics of wind turbine airfoil is undertaken by using computational fluid dynamics (CFD) method. A new pitting erosion model is proposed and semicircle cavities were used to represent the erosion pits in the simulation. Two-dimensional incompressible Reynolds-averaged Navier–Stokes equation and shear stress transport (SST) k–ω turbulence model are adopted to compute the aerodynamics of a S809 airfoil with leading edge pitting erosions, where the influences of pits depth, densities, distribution area, and locations are considered. The results indicate that pitting erosion has remarkably undesirable influences on the aerodynamic performance of the airfoil, and the critical pits depth, density, and distribution area degrade the airfoil aerodynamic performance mostly were obtained. In addition, the dominant parameters are determined by the correlation coefficient path analysis method, results showed that all parameters have non-negligible effects on the aerodynamics of S809 airfoil, and the Reynolds number is of the most important, followed by pits density, pits depth, and pits distribution area. Meanwhile, the direct and indirect effects of these factors are analyzed, and it is found that the indirect effects are very small and the parameters can be considered to be independent with each other.

Download Full-text

The aerodynamic optimisation of a low-Reynolds paper plane with adjoint method

The Aeronautical Journal ◽

10.1017/aer.2020.78 ◽

2020 ◽

pp. 1-15

Author(s):

Y. Zhang ◽

X. Zhang ◽

G. Chen

Keyword(s):

Adjoint Method ◽

Low Cost ◽

Aerodynamic Performance ◽

Discrete Adjoint ◽

Design Variables ◽

Limited Variation ◽

Aerial Vehicle ◽

Paper Plane ◽

Drag Ratio ◽

Lift To Drag Ratio

ABSTRACT The aerodynamic performance of a deployable and low-cost unmanned aerial vehicle (UAV) is investigated and improved in present work. The parameters of configuration, such as airfoil and winglet, are determined via an optimising process based on a discrete adjoint method. The optimised target is locked on an increasing lift-to-drag ratio with a limited variation of pitching moments. The separation that will lead to a stall is delayed after optimisation. Up to 128 design variables are used by the optimised solver to give enough flexibility of the geometrical transformation. As much as 20% enhancement of lift-to-drag ratio is gained at the cruise angle-of-attack, that is, a significant improvement in the lift-to-drag ratio adhering to the preferred configuration is obtained with increasing lift and decreasing drag coefficients, essentially entailing an improved aerodynamic performance.

Download Full-text

The effect of leading-edge droop on the performance of cavitating hydrofoil in an oscillating environment

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/09544062jmes1142 ◽

2009 ◽

Vol 223 (10) ◽

pp. 2331-2339

Author(s):

K Park ◽

H Sun ◽

S Lee

Keyword(s):

Leading Edge ◽

Hydrodynamic Performance ◽

Control Surface ◽

Navier Stokes ◽

Two Phase ◽

Sheet Cavitation ◽

Maximum Angle ◽

Oscillating Motion ◽

Drag Ratio ◽

Cavitating Hydrofoil

The hydrodynamics of cavitating hydrofoil in oscillating motion are important in the aspect of the performance and hydro-elasticity of the control surface of the ship. The effect of leading-edge droop is numerically studied in the oscillating hydrofoil with cavitation. A two-phase incompressible Navier—Stokes solver is used to compute the cavitation flow. The hydrodynamic performance of the baseline hydrofoil is compared with that of the fixed droop and the variable droop hydrofoil. The droop models delay the separation behind the sheet cavitation near the maximum angle of attack. When the pitch goes down, the drooped models suppress the collapse of the sheet cavitation. Therefore, they result in the improved hydrodynamic performance against the baseline model through the oscillation cycle. Among the three hydrofoils, the variable droop showed the smallest change of the lift-to-drag ratio.

Download Full-text

Roughness Sensitivity Considerations for Thick Rotor Blade Airfoils

Journal of Solar Energy Engineering ◽

10.1115/1.1624614 ◽

2003 ◽

Vol 125 (4) ◽

pp. 468-478 ◽

Cited By ~ 93

Author(s):

R. P. J. O. M. van Rooij ◽

W. A. Timmer

Keyword(s):

Turbine Blades ◽

Leading Edge ◽

Lower Surface ◽

Vortex Generators ◽

Wind Turbine Blades ◽

High Lift ◽

Edge Roughness ◽

Proper Design ◽

Drag Ratio ◽

Lift To Drag Ratio

In modern wind turbine blades, airfoils of more than 25% thickness can be found at mid-span and inboard locations. At mid-span, aerodynamic requirements dominate, demanding a high lift-to-drag ratio, moderate to high lift and low roughness sensitivity. Towards the root, structural requirements become more important. In this paper, the performance for the airfoil series DU FFA, S8xx, AH, Risø and NACA are reviewed. For the 25% and 30% thick airfoils, the best performing airfoils can be recognized by a restricted upper-surface thickness and an S-shaped lower surface for aft-loading. Differences in performance of the DU 91-W2-250 (25%), S814 (24%) and Risø-A1-24 (24%) airfoils are small. For a 30% thickness, the DU 97-W-300 meets the requirements best. Reduction of roughness sensitivity can be achieved both by proper design and by application of vortex generators on the upper surface of the airfoil. Maximum lift and lift-to-drag ratio are, in general, enhanced for the rough configuration when vortex generators are used. At inboard locations, 2-D wind tunnel tests do not represent the performance characteristics well because the influence of rotation is not included. The RFOIL code is believed to be capable of approximating the rotational effect. Results from this code indicate that rotational effects dramatically reduce roughness sensitivity effects at inboard locations. In particular, the change in lift characteristics in the case of leading edge roughness for the 35% and 40% thick DU airfoils, DU 00-W-350 and DU 00-W-401, respectively, is remarkable. As a result of the strong reduction of roughness sensitivity, the design for inboard airfoils can primarily focus on high lift and structural demands.

Download Full-text

Effects of leading-edge bevel angle on the aerodynamic forces of a non-slender 50° delta wing

The Aeronautical Journal ◽

10.1017/s0001924000000828 ◽

2005 ◽

Vol 109 (1098) ◽

pp. 403-407 ◽

Cited By ~ 7

Author(s):

J. J. Wang ◽

S. F. Lu

Keyword(s):

Delta Wing ◽

Lift Coefficient ◽

Leading Edge ◽

Relative Thickness ◽

Aerodynamic Performances ◽

Stall Angle ◽

Drag Ratio ◽

Low Speed Wind Tunnel ◽

Lift To Drag Ratio ◽

Blunt Leading Edge

Abstract The aerodynamic performances of a non-slender 50° delta wing with various leading-edge bevels were measured in a low speed wind tunnel. It is found that the delta wing with leading-edge bevelled leeward can improve the maximum lift coefficient and maximum lift to drag ratio, and the stall angle of the wing is also delayed. In comparison with the blunt leading-edge wing, the increment of maximum lift to drag ratio is 200%, 98% and 100% for the wings with relative thickness t/c = 2%, t/c = 6.7% and t/c = 10%, respectively.

Download Full-text