Wing In Ground Effect Research Articles

Computational analysis of static height stability and aerodynamics of vehicles with a fuselage, wing and tail in ground effect

Wing-in-ground (WIG) effect vehicles skim the surface of the ground or water using an air cushion between the vehicle and the surface. The lift augmentation and drag reduction are considerable compared to an airplane flying out of ground effect and significantly enhance the aerodynamic performance. However, the stability problem is still a challenge for researchers and designers of WIG effect vehicles. In a previous study, sectional shapes were optimized for the wing-in-round effect (WIG) using computational fluid dynamics (CFD) and multi-objective optimization with two objectives: the aerodynamic center of height, which is part of the static height stability, and the lift-to-drag ratio. The optimization study obtained 113 optimal solutions called Pareto optima or Pareto sets, which include various airfoil profiles such as a flat lower surface and a convex lower surface next to the trailing edge. In this study, some of the Pareto optima that show the characteristics of features in the design domain are selected, and are applied to a three-dimensional vehicle with a fuselage, lifting and control surfaces such as a horizontal tail. Three featured optima that show high stability, high performance, and relatively stable cases are carefully investigated using computational methods to analyze the aerodynamic characteristics, stability, and three-dimensional effects.

English

English

Near-wake characteristics of rigid and membrane wings in ground effect

Wind tunnel measurements are conducted at a Reynolds numbers of Re=56,000 to examine the characteristics of near-wake vortices of rigid flat-plates and membrane wings from free-flight into ground-effect conditions. Synchronised high-speed load cell measurements, digital image correlation and particle image velocimetry are performed to resolve lift, drag and pitch oscillations simultaneously with membrane deformation and flow dynamics. Flow measurements are acquired in a crossflow-plane, one chord downstream of the trailing-edge, allowing the examination of time evolution of the wake and its relationship to the forces and membrane deformation. Membrane wings are found to delay ground-effect or high angles-of-attack induced tip-vortex break-down and result in larger tip-vortex push-out (beyond the wing span) compared to rigid flat-plate wings. The leading-edge vortex appears to shed with streamwise vorticity close to the root of the wing and this frequency of this shedding is found to match with the dominant frequency observed in membrane fluctuations. In specific resonance conditions, membrane and flow fluctuations are found to correlate well to the fluctuations in loads and moments.

CFD Simulation of a Wing-In-Ground-Effect UAV

This paper reports a numerical analysis on a wing section used for a Wing-In-Ground-Effect (WIG) unmanned aerial vehicle (UAV). The wing geometry was created by SolidWorks and the incompressible Reynolds-averaged Navier-Stokes (RANS) equations were solved with the Spalart–Allmaras turbulence model using CFD software ANSYS FLUENT. In FLUENT, the Spalart-Allmaras model has been implemented to use wall functions when the mesh resolution is not sufficiently fine. This might make it the best choice for relatively crude simulations on coarse meshes where accurate turbulent flow computations are not critical. The results show that the lift coefficient and lift-drag ratio derived excellent performance enhancement by ground effect. However, the moment coefficient shows inconsistency when the wing is operating in very low altitude - this is owing to the difficulty on the stability control of WIG vehicle. A drag polar estimation based on the analysis also indicated that the Oswald (or span) efficiency of the wing was improved by ground effect.

Ground Effect on the Vortex Flow and Aerodynamics of a Slender Delta Wing

The ground effect on the aerodynamic loading and leading-edge vortex (LEV) flow generated by a slender delta wing was investigated experimentally. Both the lift and drag forces were found to increase with reducing ground distance (up to 50% of the wing chord). The lift increment was also found to be the greatest at low angles of attack α and decreased rapidly with increasing ground distance and α. The ground effect-caused earlier wing stall was also accompanied by a strengthened LEV with an increased rotational speed and size compared to the baseline wing. The smaller the ground distance, the stronger the LEV and the earlier vortex breakdown became. Meanwhile, the vortex trajectory was also found to be located further inboard and above the delta wing in ground effect compared to its baseline-wing counterpart. Finally, for wing-in-ground effect (WIG) craft with delta-wing planform the most effective in-ground-effect flight should be kept within 10% of the wing chord.

Forcing Boundary-Layer Transition on a Single-Element Wing in Ground Effect

The transition from a laminar to turbulent boundary layer on a wing operating at low Reynolds numbers can have a large effect on its aerodynamic performance. For a wing operating in ground effect, where very low pressures and large pressure gradients are common, the effect is even greater. A study was conducted into the effect of forcing boundary-layer transition on the suction surface of an inverted GA(W)-1 section single-element wing in ground effect, which is representative of a racing-car front wing. Transition to a turbulent boundary layer was forced at varying chordwise locations and compared to the free-transition case using experimental and computational methods. Forcing transition caused the laminar-separation bubble, which was the unforced transition mechanism, to be eliminated in all cases and trailing-edge separation to occur instead. The aerodynamic forces produced by the wing with trailing-edge separation were shown to be dependent on trip location. As the trip was moved upstream the separation point also moved upstream, this led to an increase in drag and reduction in downforce. In addition to significant changes to the pressure field around the wing, turbulent energy in the wake was considerably reduced by forcing transition. The differences between free- and forced-transition wings were shown to be significant, highlighting the importance of modeling transition for ground-effect wings. Additionally, it has been shown that while it is possible to reproduce the force coefficient of a higher Reynolds-number case by forcing the boundary layer to a turbulent state, the flow features, both on-surface and off-surface, are not recreated.

Usage of wing in ground effect to maintain lift force with reduced fuel consumption of aircraft

The main purpose of this article was to point out causes of reduced fuel consumption in aircraft jet engine when aircraft is in ground effect influence. Wing in ground effect occurs in the direct proximity of ground. The paper presents wing in ground effect description, with the numerical analysis of NACA M8 airfoil in three different conditions of flight. Numerical analysis was conduct in Ansys Fluent 17.2 software. The paper shows results of simulations which describes wing in ground effect influence on NACA M8 airfoil with two cases of jet engine exhaust gasses usage, first with exhaust gasses stream turns on upper airfoil surface, and second with exhaust gasses stream turns under lower airfoil surface. Results allow to define characteristics of NACA M8 airfoil in the influence of wing in ground effect which are lift coefficient, drag coefficient, drop of fuel consumption usage by the jet engine when lift force remains still in the wing in ground effect. The paper shows that in the wing in ground effect aircraft energy usage for flight in ground effect is smaller than for free air flight.

Analiza numeryczna wpływu efektu przypowierzchniowego na siłę nośną samolotu i siłę docisku pojazdu drogowego

The paper presents the mechanism of wing in ground effect formation, also shows the structure of wing in ground craft, and race car, which uses wing in ground effect. Results of numerical analysis are as expected, which means, the lift coefficient is higher for positive angles of attack, and lower for negative angles of attack. The paper details also characteristics of lift and drag coefficients in angle of attack function. The numerical research was conduct in Ansys Fluent 15.0 academic license. Keywords: airfoil, aircraft, wing in ground effect, numerical analysis

Induced drag of wings in ground effect

ABSTRACTThis paper provides a set of closed form solutions for the lift and drag of wings flying in ground effect both with and without end plates. The developed theories are based on observations of several independent sources of controlled model tests over ground planes and over water and on previous theories prepared by researchers from the original work by Prandtl and Wieselsberger to the present day. The theories developed cover wings of varying aspect ratio, thickness to chord ratios and angle of attack. The results for wings with end plates include the effect of ground (or surface) clearance height, end plate depth and air gap depths beneath the wings or end plates. Good agreement is found between the developed theory and test.

Computational analysis of aerodynamic characteristics for wing in ground effect craft in lateral stability

Wing in-ground effect (WIG) crafts are becoming promising transportation over the last decade. However, stability and control problems faced by the WIG in earlier development are still unresolved. This paper objectively investigates the lateral stability of wing in ground effect craft. The wing encompasses a winglet at the end of the wingtip. Lift, drag and pressure were measured with the respect of the heeling angle of 100, 150 and 200, respectively, with the h/c of 0.3. Initial results from the computational studies show that the ground effect pressure distributions provide a natural righting moment when the WIG craft heels near ground. This initial result provides an insight to understand the current state of knowledge of stability for WIG, particularly on transverse or lateral stability of WIG where it plays important roles in the safety aspect. It is crucial to understand the stability and its component in order to avoid any unforeseen accident. This paper discusses the results obtained from the numerical studies.

Investigation of longitudinal dynamics of a small WIG craft in flight over sea Waves

The flight dynamics of Wing in Ground Effect (WIG) crafts over sea waves in the layer of Strong Ground Effects (SGE) are complex phenomena. In this article, the longitudinal flight dynamics of a small WIG are investigated, thereby showing a nonlinear dynamic behaviour due to variable aerodynamic coefficients that could be affected by the vehicle flight altitude and other environmental parameters such as flying over short, moderate, and long regular sea waves. Instability regions are analysed and compared to traditional simplified equations of motion for different geometries of waves. Simulations are arranged for variations in both manoeuvre requirements and flying vehicle parameters (e.g. cruise speed and mass moment of inertia). A sensitivity analysis is carried out to evaluate the magnitude of a vehicle's lift coefficient as a function of sea wave length and amplitude in terms of some real-world uncertainty sources. The efficacy of the proposed method is demonstrated through the application of simulations. In particular, it is verified that this method is able to produce more reliable results in satisfying constraints and requirements of the underlying problem.Dynamics of a WIG craft in SGE layer.

Mathematical model for takeoff simulation of a wing in proximity to the ground

Aircraft flying close to the ground benefit from enhanced efficiency owing to decreased induced drag and increased lift. In this study, a mathematical model is developed to simulate the takeoff of a wing near the ground using an Iterative Boundary Element Method (IBEM) and the finite difference scheme. Two stand-alone sub-codes and a mother code, which enables communication between the sub-codes, are developed to solve for the self-excitation of the Wing-In-Ground (WIG) effect. The aerodynamic force exerted on the wing is calculated by the first sub-code using the IBEM, and the vertical displacement of the wing is calculated by the second sub-code using the finite difference scheme. The mother code commands the two sub-codes and can solve for the aerodynamics of the wing and operating height within seconds. The developed code system is used to solve for the force, velocity, and displacement of an NACA6409 wing at a 4° Angle of Attack (AoA) which has various numerical and experimental studies in the literature. The effects of thickness and AoA are then investigated and conclusions were drawn with respect to generated results. The proposed model provides a practical method for understanding the flight dynamics and it is specifically beneficial at the pre-design stages of a WIG effect craft.

Numerical study on aerodynamics of banked wing in ground effect

Unlike conventional airplane, a WIG craft experiences righting moment and adverse yaw moment in banked turning in ground effect. Numerical simulations are carried out to study the aerodynamics of banked wing in ground effect. Configurations of rectangular wing and delta wing are considered, and performance of endplates and ailerons during banking are also studied. The study shows that righting moment increase nonlinearly with heeling angle, and endplates enhance the righting. The asymmetric aerodynamic distribution along span of wing with heeling angle introduces adverse yaw moment. Heeling in ground effect with small ground clearance increases the vertical aerodynamic force and makes WIG craft climb. Deflections of ailerons introduce lift decrease and a light pitching motion. Delta wing shows advantage in banked turning for smaller righting moment and adverse yaw moment during banking.

Numerical study of aerodynamic forces and flow physics of a delta wing in dynamic ground effect

During takeoff and landing processes, the aerodynamic characteristics of a delta wing configuration aircraft are influenced by the dynamic ground effect (DGE). In this paper, the DGE during the landing process of a 65° sweep delta wing (VFE-2) with sharp leading edge is numerically studied at AOA = 23°. The unsteady compressible Reynolds-Averaged Navier–Stokes equations and Spalart–Allmaras turbulence model are discretized using the finite volume method. With the ride height decreasing, the lift, drag and nose-down pitching moment increase nonlinearly, and the increments become larger with the sink velocity increasing. The DGE can be divided into three regions based on the aerodynamics and flow physics. In the large ride height region, the aerodynamic forces in DGE remain unchanged with the ride height decreasing, and they are equal to those in static ground effect (SGE) as long as the angles of attack (AOAs) are equal; the ground effect (GE) can be neglected. In the medium ride height region, the aerodynamic forces in DGE increase slowly with the ride height decreasing, and they are still equal to those in SGE as long as the AOAs are equal; SGE governs the flow. In the small ride height region, the aerodynamic forces in DGE increase significantly with the ride height decreasing, and they are much larger than those in SGE although the AOAs are equal; SGE and compression work effect govern the flow together. Among them, SGE stagnates the airflow under the delta wing, increasing the pressure on the windward surface; simultaneously, it enhances the primary vortex strength, promotes its breakdown and drives it outward along the span. The compression work effect further increases the pressure on the windward surface; however, it has little influence on the airflow over the delta wing.

A practical method for aerodynamic investigation of WIG

Purpose – The purpose of this paper is to present a fast, economical and practical method for mathematical modeling of aerodynamic characteristics of rectangular wing in ground (WIG) effect. Design/methodology/approach – Reynolds averaged Navier–Stokes (RANS) equations were converted to Bernoulli equation by reasonable assumptions. Also, Helmbold’s equation has been developed for calculation of the slope of wing lift coefficient in ground effect by defining equivalent aspect ratio (ARe). Comparison of present work results against the experimental results has shown good agreement. Findings – A practical mathematical modeling with lower computational time and higher accuracy was presented for calculating aerodynamic characteristics of rectangular WIG effect. The relative error between the present work results and the experimental results was less than 8 per cent. Also, the accuracy of the proposed method was checked by comparing with the numerical methods. The comparison showed fairly good accuracy. Researc...

GS0516 地面効果内における翼のヨーイング特性

GS0516 地面効果内における翼のヨーイング特性

Downstream evolution of wingtip vortices produced from an inverted wing

AbstractCounter-rotating vortices form from the opposite edges of lifting surfaces, and gradually move laterally and dissipate as they travel downstream (as seen in a wing-fixed reference frame). Under ground effect conditions, the vortex from a lifting wing – such as that used in an aircraft application – moves laterally outboard from the wingtip as it progresses downstream; for a downforce wing in ground effect – such as that used in an automotive application – the vortex moves laterally inboard. An interesting case is the situation where the inboard moving vortices become in close proximity to each other. The objective of the present study was to investigate counter-rotating vortices produced from a low aspect ratio downforce wing operating in ground effect. The pair of vortices move towards each other and mutually induce an upwards directed motion which in turn reduces the inboard movement driven by the ground effect. Experimental data gained from three-dimensional Laser Doppler Anemometry in a moving ground wind-tunnel was used to validate a Large Eddy Simulation computational result.

DDES study of the aerodynamic forces and flow physics of a delta wing in static ground effect

During takeoff and landing phases, the performance of an aircraft with delta wing configuration is significantly influenced by the ground effect (GE). In this paper, the static ground effect (SGE) of a 65° sweep delta wing (VFE-2) with sharp leading edge at α=20° is investigated by the Delayed Detached Eddy Simulation (DDES) grounded on Spalart–Allmaras (S–A) turbulence model. With the ride height decreasing, the lift, drag and nose-down pitching moment of the delta wing increase nonlinearly, and the majority of aerodynamic force increments in SGE are from the windward side of the delta wing. With the ride height decreasing, under the windward side, the flow is severely blocked resulting in the augmentation of static pressure, and the increasing span wise flow near the leading edge strengthens the shear layer and the leading edge vortex over the leeward side. The strengthened leading edge vortex induces lower pressure over the leeward side, and moves outside along the span wise direction. With the ride height decreasing, the jet-like flow in the primary vortex core is accelerated before the vortex breakdown, and the wake-like flow in the primary vortex core is decelerated after the vortex breakdown.

WIG (wing-in-ground) effect dual-foil turbine for high renewable energy performance

Traditional HATs (horizontal axis turbines) are predominantly used for wind and tidal energy generation. HATs have higher power production than VATs (vertical axis turbines) for which also requires a rotational motion of their rotors. Existing HAT installations and operations are widely seen as wind turbines on land and hydrokinetic turbines underwater. However, the operation of both HAT and VAT requires large rotor diameter for large energy production. These introduce some disadvantages: requirement of large profile height on land and water depth underwater; high rotor tip speed and hence impact on surrounding ecology; and requirement of large kick-in speed and hence a low wind/tidal resource utilization or inapplicability in slow inflow energy sites. A dual-foil dynamic WIG (Wing-In-Ground) effect turbine, WIGT (Wing-in-ground effect turbine) for short, was developed and its renewable energy performance and characteristics were investigated. A performance comparison between traditional HATT (horizontal axis tidal turbine) and a WIGTT (wing-in-ground effect tidal turbine) was made, based on the tidal flow probability distribution of the Minas Passage, the Bay of Fundy, Canada. With about the same swept area, the WIGTT produces 1.73 times annual energy as an HATT. WIGT uses an active pitch control but the required power to pitch the foils was found to be about 10% generated power at the maximum. The use of trapezoidal pitch control produces 1.44 times as much power as either single-foil or dual-foil turbines. With a minimum gap of 16% chord between the foils, dynamic WIG effect produces 1.42 times as much energy. WIGT could generate 5 times power as much as a single foil with sinusoidal pitch and heave. WIGTs also have some outstanding advantages such as large power capacity under confined profile height on land or in shallow waters, power generation capability for low speed inflow, environmental friendly operation and better flow characteristics.

21013 プロペラ付き地面効果翼の空力特性

WIG(Wing In Ground effect)can be improve their coefficient of lift by PAR(Power Augmented Ram), that blow air into lower side of a blade in order to increase a pressure in that space. To make their relation clear, we have evaluated such aerodynamic characteristics making some experiments and simulating by computation fluid dynamics. The wind tunnel we have used in the experiments is 600mm in width, and 600mm in height. It is capable of moving air at speeds up to about 20m/s. We cut a lower part of NACA6409 in order to raise a rate of increase in a coefficient of lift compared to it without modification. Aerodynamics characteristics of a WIG is effected by ground when h/c is 0.1 or less.