scholarly journals Airfoil Aerodynamics in Proximity to Wavy Ground for a Wide Range of Angles of Attack

2020 ◽  
Vol 10 (19) ◽  
pp. 6773
Author(s):  
Haode Hu ◽  
Dongli Ma
Keyword(s):  
Stokes Equations ◽  
Angle Of Attack ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Aerodynamic Coefficients ◽  
Ride Height ◽  
Wide Range ◽  
The Difference ◽  
Flat Ground

Wing-in-ground craft often encounter waves when flying over the sea surface, and the ground effect is more complicated than that of flat ground. Therefore, the aerodynamic characteristics of the NACA 4412 airfoil in proximity to wavy ground for a wide range of angles of attack is studied by solving the Reynolds Averaged Navier–Stokes equations. The validation of the numerical method is carried out by comparing it with the experimental data. The results show that the aerodynamic coefficients will fluctuate periodically when the airfoil moves over wavy ground at a small ride height. Except for the angle of attack of 0°, the fluctuation trend of aerodynamic coefficients at other angles of attack is the same. The analysis of aerodynamic fluctuation amplitude found that the medium angle of attack should be selected as the design cruise angle of attack for wing-in-ground craft. The time-averaged aerodynamic coefficients in the case of wavy ground are almost the same as those of flat ground. Hence, wavy ground mainly causes a fluctuation in aerodynamic coefficients. Considering the difference between aerodynamic coefficients at the angle of attack of 0° and at other angles of attack, the flow field structure at an angle of attack of 0° and 4° is analyzed. The results reveal the aerodynamic characteristics of the airfoil moving over wavy ground, which gives a deeper understanding of the ground effect in the conditions of wavy surface/ground. This has a certain guiding significance for the design of wing-in-ground craft.

scholarly journals РОЗРАХУНОК АЕРОДИНАМІЧНИХ ХАРАКТЕРИСТИК НАДЗВУКОВИХ ОПЕРЕНИХ ОСЕСИМЕТРИЧНИХ ТІЛ ОБЕРТАННЯ

2019 ◽  
pp. 4-17
Author(s):  
Олександр Миколайович Шийко ◽  
Анатолій Михайлович Павлюченко ◽  
Андрій Вікторович Скорик ◽  
Олексій Анатолійович Обухов ◽  
Ігор Володимирович Коплик
Keyword(s):  
Numerical Solution ◽  
Stokes Equations ◽  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Aerodynamic Coefficients ◽  
Navier Stokes Equations ◽  
Friction Resistance ◽  
Ansys Cfx

The subject of research in the article is the aerodynamic forces arising from the flight of supersonic feathered rotation bodies such as unguided rockets. The aim of the work is to develop a method for calculating the aerodynamic coefficients of the resultant forces and moments of supersonic feathered bodies of revolution such as unguided missiles when flown around at an angle of attack with pre-, trans- and supersonic speeds according to drawings of their external contours. Tasks: using modern software systems and flight experiments, develop a method for calculating the distribution of normal and tangential stresses over the surface of a supersonic feathered body of rotation, their equivalent and aerodynamic coefficients at up-, trans- and supersonic flow velocities at an angle of attack. The applied methods are the numerical solution of the Navier-Stokes equations, the use of two-parameter differential models of near-wall turbulent viscosity, verification of the methodology by comparing the results of calculations with the data of flight experiments and known data on the aerodynamic resistance of the object of research. The following results were obtained. Based on the numerical solution of the Navier-Stokes equations in the ANSYS CFX software package using the γ-ReΘt SST–model of Menter’s near-wall turbulence, a method is developed for calculating the aerodynamic characteristics of supersonic axially symmetric rotation bodies of uncontrollable missiles according to drawings of the external contours in the presence of a counter-flow angle. Using the developed technique it is possible to calculate the aerodynamic coefficients of friction resistance, pressure resistance and bottom resistance at sub-, trans- and supersonic speeds. Characteristics include the coefficients of the longitudinal aerodynamic force, transverse aerodynamic force, aerodynamic stabilizing moment and the coordinate of the center of pressure of the feathered body of rotation. For the calculations, were applied the external contours of the unguided missile M–21OФ. Calculations were performed for the counter-flow Mach numbers within0,1 £ M∞ £ 2,5. The aerodynamic coefficients were calculated as functions of the Mach number M∞. In order to determine the Reynolds number of the beginning of the laminar-turbulent transition in the boundary layer for this type of aircraft the characteristics of the friction resistance were calculated and compared with the flight data for two samples of research aerophysical complexes. Conclusions. The scientific novelty of the results is as follows: a pilot test was created and involved the results of flight experiments on Reynolds numbers of the start of a laminar-turbulent transition in the boundary layers of a method for calculating the aerodynamic drag coefficients of supersonic axially rotated bodies of rotation like uncontrollable missiles according to the drawings of their external contours during turning angle of attack based on the numerical solution of the Reynolds-averaged Navier-Stokes equations in the framework of the programme product ANSYS CFX using γ-ReΘt SST–Menter turbulence model. Verification of the calculation results was carried out on the basis of their comparison with the known values of the aerodynamic characteristics of the object of research with the axisymmetric flow.

Computational Analysis of a Inverted Double-Element Airfoil in Ground Effect

2006 ◽  
Vol 128 (6) ◽  
pp. 1172-1180 ◽  
Author(s):  
Stephen Mahon ◽  
Xin Zhang
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Near Field ◽  
Turbulence Models ◽  
Ground Effect ◽  
Wake Flow ◽  
Navier Stokes ◽  
Main Element ◽  
Ride Height ◽  
Navier Stokes Equations

The flow around an inverted double-element airfoil in ground effect was studied numerically, by solving the Reynolds averaged Navier-Stokes equations. The predictive capabilities of six turbulence models with regards to the surface pressures, wake flow field, and sectional forces were quantified. The realizable k−ε model was found to offer improved predictions of the surface pressures and wake flow field. A number of ride heights were investigated, covering various force regions. The surface pressures, sectional forces, and wake flow field were all modeled accurately and offered improvements over previous numerical investigations. The sectional forces indicated that the main element generated the majority of the downforce, whereas the flap generated the majority of the drag. The near field and far field wake development was investigated and suggestions concerning reduction of the wake thickness were offered. The main element wake was found to greatly contribute to the overall wake thickness with the contribution increasing as the ride height decreased.

scholarly journals Numerical Simulation on Aerodynamics of Multi-Element Airfoil with Drooped Spoiler in Ground Effect

2019 ◽  
Vol 37 (1) ◽  
pp. 167-176
Author(s):  
Jiang Liu ◽  
Junqiang Bai ◽  
Guozhu Gao ◽  
Min Chang ◽  
Nan Liu
Keyword(s):  
Lift Coefficient ◽  
Angle Of Attack ◽  
Ground Effect ◽  
Lower Surface ◽  
Navier Stokes ◽  
High Angle ◽  
High Angle Of Attack ◽  
Ride Height ◽  
Navier Stokes Equation ◽  
Sst Turbulence Model

By using the finite volume method and k-ω SST turbulence model to solve the Reynolds Average Navier-Stokes equation and using the slipping wall to simulate the relative movement of the ground, the ground effect on the aerodynamic characteristic of multi-element airfoil with drooped spoiler is investigated numerically, and the reason why the lift coefficient decreased in ground effect is analyzed. The results indicate that, with the reduction in ride height, the lift and the drag decrease and the lift-drag ratio increases for the multi-element airfoil; the amplitude of the reduction in the lift coefficient increases with the reduction in ride height and the increase in the angle of attack, the maximum of lift coefficient can be reduced by about 22%; with the effect of ground, the losses of suction at upper surface make the lift decrease, the increases of pressure at lower surface make the lift increase, the variation of the lift coefficient for the main wing caused by the former is more than three times that of the latter. Analyzing the reason why the lift coefficient decreases showed that:on the one hand, ground effect on the lift coefficient for clean airfoil is changed with the range of angle of attack. For the low-to-moderate angle of attack, the lift coefficient increases; for the high angle of attack, the lift coefficient decreases. But multi-element airfoil works in the takeoff and landing stage for the high angle of attack, which causes the reduction of the lift coefficient in ground effect. On the other hand, the increase of the lift coefficient caused by the deflection of spoiler decreases with the reduction in ride height and the maximum reduction can be about 50%, which illustrates that ground effect makes interaction of the front and back section for the multi-element airfoil weak, resulting in further decreasing the coefficient for the multi-element airfoil.

Numerical Study of Wing Aerodynamics in Ground Proximity

2008 ◽  
Author(s):  
Alex E. Ockfen ◽  
Konstantin I. Matveev
Keyword(s):  
Iterative Process ◽  
Stokes Equations ◽  
Numerical Study ◽  
Ground Effect ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Design And Optimization ◽  
Volume Method ◽  
Experimental Design And Optimization

Experimental design and optimization of innovative ground-effect transportation means is an iterative process which requires a large amount of time and resources. To avoid the large experimental expense, numerical modeling can be used to investigate Wing-in-Ground (WIG) vehicle flight. In this paper, modeling technique is applied for a two dimensional NACA 4412 airfoil in viscous flow in and out of ground effect. The numerical method consists of a steady state, incompressible, finite volume method utilizing the Spalart-Allmaras turbulence model. Grid generation and solution of the Navier-Stokes equations are completed using FLUENT 6.3. The modeling procedures are first validated against published experimental data for unbounded flow around an airfoil. Wing section aerodynamic characteristics are then studied for varying ground heights and two separate boundary conditions: fixed ground and moving ground. Ground effect calculations are compared to several previous studies, and our results are found to correlate with published aerodynamic trends in ground effect, although all studies appear to predict different magnitudes of aerodynamic forces.

scholarly journals Numerical determination of aerodynamic characteristics of an airfoil in a ground effect

2021 ◽  
pp. 44-50
Author(s):  
М.А. Ливеринова ◽  
Н.В. Тряскин
Keyword(s):  
Pressure Coefficient ◽  
Independent Solution ◽  
Ground Effect ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Method Of Images ◽  
Reverse Motion ◽  
Continuity Equations ◽  
The Difference

В работе изучается движение профиля над экраном на различных относительных высотах. Рассмотрены следующие методы его моделирования: условие неподвижного экрана и метод зеркального отображения для моделирования обращённого движения и условие экрана, движущегося со скоростью профиля, что моделирует прямое движение. Целью работы является выбор метода моделирования экрана, при котором обтекание профиля соответствует действительности и оценка разницы между рассмотренными методами. Задача решена в открытом пакете OpenFOAM методом контрольного объёма, где совместно решены уравнения Навье-Стокса и неразрывности, осреднённые по Рейнольдсу. Произведена верификация и валидация математической модели и найдено сеточно-независимое решение. Выбраны два профиля в плане: сегментный и симметричный. Рассмотрены несколько относительных высот. В работе построены эпюры скоростей под профилем, представлены картины обтекания профилей, исследованы их основные эксплуатационные характеристики: коэффициент подъёмной силы и коэффициент сопротивления в зависимости от относительной высоты. Построено распределение коэффициента давления по поверхности рассматриваемых профилей в зависимости от граничных условий и относительных высот. В результате анализа показано различие происходящих физических процессов при обтекании профилей в прямом и обращённом движении. Данная работа позволяет сделать вывод о том, каким образом проводить физический эксперимент для различных профилей, показывает преимущество использования метода зеркальных отображений или подвижного экрана при проведении эксперимента. In this article the movement of the profile above the screen at different relative heights is reviewed. The following methods of its modeling are considered: the condition of a stationary screen and the method of images for simulating reverse motion and the condition of a screen moving with the profile speed that simulate forward motion are considered. The aim of the work is to select a screen simulation method for a physical experiment. An open-source packet OpenFOAM based on finite-volume method is used to solve the Navier-Stokes and continuity equations averaged by Reynolds method. The mathematical model is verified and validated, and a grid-independent solution is found. Two profiles are selected: segmental and symmetrical. Several relative heights are considered. The velocitiy profiles under the airfoil are constructed, the patterns of the flow around the airfoils are presented. The dependences of coefficients on the studied parameters and the distribution of the pressure coefficient over the profile are studied and analyzed. As a result of the analysis, the difference between the physical processes when flowing around the airfoils is in forward and reverse motion is shown. This work allows us to make a conclusion about how to conduct a model experiment for various profiles, shows the advantage of using the method of images or a movable screen in the experiment.

Aerodynamics of a two-dimensional flapping wing hovering in proximity of ground

2019 ◽  
Vol 233 (12) ◽  
pp. 4316-4332 ◽  
Author(s):  
Yunlong Zheng ◽  
Qiulin Qu ◽  
Peiqing Liu ◽  
Yunpeng Qin ◽  
Ramesh K Agarwal
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Aerodynamic Force ◽  
Ground Effect ◽  
Flapping Wing ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Lift Mechanism ◽  
The Difference

The difference in aerodynamic forces of a two-dimensional flapping wing hovering in unbounded flow field and ground effect is studied. The unsteady laminar Navier–Stokes equations are solved by the finite volume method to simulate the flow field around the wing. In the unbounded flow field, the correspondence between the aerodynamic force, pressure distribution on wing, and typical vortex structures is established, and then the high-lift mechanism of the flapping wing is further explained. In the ground effect, based on the lift variation, the dimensionless height H/ C ( H is the height of the wing above ground and C is the chord length of the wing) can be divided into transition and ground effect regimes. In the transition regime ( H/ C > 2.5), the lift decreases with the decreasing height, and the ground indirectly impacts the vortices near wing by changing the shed vortices in space. In the ground effect regime ( H/ C < 2.5), the lift increases with the decreasing height, and the ground directly impacts the vortices near the wing.

A Computational Analysis of Flow Field in Twin-Track Subway Tunnel to Improve Air Quality

2013 ◽  
Vol 319 ◽  
pp. 599-604
Author(s):  
Makhsuda Juraeva ◽  
Kyung Jin Ryu ◽  
Sang Hyun Jeong ◽  
Dong Joo Song
Keyword(s):  
Air Quality ◽  
Computational Model ◽  
Stokes Equations ◽  
Ventilation System ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Subway Tunnel ◽  
Air Supply ◽  
And Performance

A computational model of existing Seoul subway tunnelwas analyzed in this research. The computational model was comprised of one natural ventilationshaft, two mechanical ventilationshafts, one mechanical airsupply, a twin-track tunnel, and a train. Understanding the flow pattern of the train-induced airflow in the tunnel was necessary to improve ventilation performance. The research objective wasto improve the air quality in the tunnel by investigating train-induced airflow in the twin-track subway tunnel numerically. The numerical analysis characterized the aerodynamic behavior and performance of the ventilation system by solving three-dimensional turbulent Reynolds-averaged Navier-Stokes equations. ANSYS CFX software was used for the computations. The ventilation and aerodynamic characteristics in the tunnel were investigated by analyzing the mass flowrateat the exits of the ventilation mechanicalshafts. As the train passed the mechanical ventilation shafts, the amount of discharged-air in the ventilationshafts decreased rapidly. The air at the exits of the ventilation shafts was gradually recovered with time, after the train passed the ventilation shafts. The developed mechanical air-supply for discharging dusty air and supplying clean airwas investigated.The computational results showed that the developed mechanical air-supplycould improve the air quality in the tunnel.

Aerodynamic ground effects on DLRF6 vehicle

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mojtaba Tahani ◽  
Mehran Masdari ◽  
Ali Bargestan
Keyword(s):  
Stokes Equations ◽  
Ground Effect ◽  
Longitudinal Direction ◽  
Propulsion System ◽  
Navier Stokes ◽  
Noticeable Effect ◽  
Navier Stokes Equations ◽  
Vehicle Performance ◽  
Content Type ◽  
Logical Connection

Purpose The overall performance of an aerial vehicle strongly depends on the specifics of the propulsion system and its position relative to the other components. The purpose of paper is this factor can be characterized by changing several contributing parameters, such as distance from the ground, fuselage and wing as well as the nacelle outlet velocity and analyzing the aerodynamic performance. Design/methodology/approach Navier–Stokes equations are discretized in space using finite volume method. A KW-SST model is implemented to model the turbulence. The flow is assumed steady, single-phase, viscous, Newtonian and compressible. Accordingly, after validation and verification against experimental and numerical results of DLRF6 configuration, the location of the propulsion system relative to configuration body is examined. Findings At the nacelle outlet velocity of V/Vinf = 4, the optimal location identified in this study delivers 16% larger lift to drag ratio compared to the baseline configuration. Practical implications Altering the position of the propulsion system along the longitudinal direction does not have a noticeable effect on the vehicle performance. Originality/value Aerial vehicles including wing-in-ground effect vehicles require thrust to fly. Generating this necessary thrust for motion and acceleration is thoroughly affected by the vehicle aerodynamics. There is a lack of rigorous understanding of such topics owing to the immaturity of science in this area. Complexity and diversity of performance variables for a numerical solution and finding a logical connection between these parameters are among the related challenges.

Effects of Buoyancy on Laminar Flow in Curved Elliptic Ducts

1992 ◽  
Vol 114 (4) ◽  
pp. 936-943 ◽  
Author(s):  
Z. F. Dong ◽  
M. A. Ebadian
Keyword(s):  
Laminar Flow ◽  
Stokes Equations ◽  
Control Volume ◽  
Boussinesq Approximation ◽  
Navier Stokes ◽  
Uniform Heat Flux ◽  
Published Data ◽  
Circular Duct ◽  
Uniform Wall Temperature ◽  
Wide Range

This paper numerically investigates the effects of buoyancy on fully developed laminar flow in a curved duct with an elliptic cross section. The flow of Newtonian fluids is assumed steady in terms of Boussinesq approximation. The curved elliptic duct is subjected to thermal boundary conditions of axially uniform heat flux and peripherally uniform wall temperature. The numerically generated boundary-fitted coordinate system is applied to discretize the solution domain of the elliptic duct, and the Navier-Stokes equations and the energy equation, including the curvature ratio, are solved by use of the control volume-based finite difference method. The solution covers a wide range of curvature ratios, and Dean and Grashof numbers. The results presented are displayed graphically and in tabular form to illustrate the buoyancy effect. It is further shown that buoyancy acts to increase both the Nusselt number and the friction factor and changes the distribution of the velocity and the temperature. The results for the curved circular duct with and without buoyancy are compared with the data available in the open literature for all cases. Also compared with the published data are the results of laminar flow in a curved elliptic duct, and very good agreement is obtained.

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