Numerical Study on the Section Design of a Wing in Surface Effect

Septia Hardy Sujiatanti

∗

, Wasis Dwi Aryawan

, Gita Marina Ahadyanti

, M. Solikhan Arif

and Ardi

Nugroho Yulianto

Department of Naval Architecture, Faculty of Maritime Technology, Institut Teknologi Sepuluh Nopember, Surabaya,

Keywords:

Wing in Surface Effect, Wing in Ground Effect, Lift Force, Aircraft.

Abstract:

A Wing-In-Ground (WIG) craft or also known as Wing-In-Surface Effect (WISE) craft is a marine trans-

portation system equipped with wings which enables it to remain airborne just above the water surface. A

WISE-craft harness ground proximity effects to increase aerodynamic loading and efﬁciency. It ﬁlls the tech-

nological gap between common aircraft and ships. A WISE-craft operates at much higher speeds than ships

and more efﬁciently than aircraft. Another distinct advantage of a WISE-craft is its ability to take off anywhere

from the sea surface without the need for a landing strip. Due to its terriﬁc and unique features, WISE-crafts

serve as a promising choice of fast, safe and efﬁcient platform for the next generation of marine transportation

systems. The objective of this work is to investigate the aerodynamic characteristics of the section design of

the wing, for the purpose of achieving improved WISE-craft designs.

1 INTRODUCTION

Airplane wings usually produce higher lift near the

ground at a moderate angle of attack, known as a

positive ground effect. Thus, craft wing-in-ground-

effect (WIG) is designed to ﬂy near the ground us-

ing positive ground effects (Rozhdestvensky, 2006).

Compared to ships, WIG craft has lower drag, higher

speed, and lower fuel consumption, and its cruise

speed is less affected by sea states. Compared to com-

parable size aircraft, a WIG craft has a higher lift-to-

drag ratio, lower thrust, wider ﬂight range, and greater

load. On the other hand, very curved wings produce

downforce close to the ground. In this case, closer to

the ground, the greater the downforce; this is known

as the “neglect-ground-effect”. Race car wings use

the neglect ground effect to improve the race car’s

running speed and maneuverability.

To avoid collisions with buildings and hills, WIG

crafts usually cruise on the water surface, including

lakes, rivers, and oceans. There are often waves on

the surface of the water due to the wind and other

disturbances. Aerodynamics of a WIG craft that ﬂies

over different wavy surfaces than ﬂat surfaces because

of the wavy surface change the nature of the airﬂow

around the WIG craft. However, in the literature, the

majority of soil effects aerodynamic studies focus on

two-dimensional airfoils or three-dimensional wings

that ﬂy over ﬂat ground. WIG is identical to the wing

in surface effect (WISE), and in this paper, the author

uses the term WISE because our application is also on

the surface.

For a precisely designed lifting surface, the effect

of the surface brings about augmentation of lift for

smaller surface clearances. Wing proﬁles with an al-

most ﬂat lower surface (classical example is NACA

4412) produce an optimum surface effect (SE) (Sun

and Dai, 2015). Proﬁling of the foil for preferable

longitudinal static stability usually results in lower lift

coefﬁcients which are not certainly disreputable for

cruise ﬂight. For a given wing area the lift is larger for

a larger aspect ratio wing. Flaps are not as efﬁcient in

SE as they are out-of-surface effect. The drag is ma-

jority determined by its induced vortex drag compo-

nent and it depends on the reciprocal relationship of

the chord, span and surface clearance, etc.

Experiments and theory show that for a ﬁxed pitch

angle, in some cases (chord-dominated SE) the drag

increases as the wing moves closer to the surface. In

another case (span-dominated SE) the drag decreases

with decreasing surface clearance. In all cases, for a

properly designed lifting system, the lift-to-drag ra-

tio tends to increase with the decrease of the surface

clearance. Also, in all cases for a properly designed

lifting surface, the drag decreases with decreasing sur-

face clearance for constant lift. The fact that near the

surface the lift-to-drag ratio increases both with the

Sujiatanti, S., Aryawan, W., Ahadyanti, G., Arif, M. and Yulianto, A.

Numerical Study on the Section Design of a Wing in Surface Effect.

DOI: 10.5220/0008551101530158

In Proceedings of the 3rd International Conference on Marine Technology (SENTA 2018), pages 153-158

ISBN: 978-989-758-436-7

153

increase of the aspect ratio and decrease of the sur-

face clearance provides more ﬂexibility in selecting

optimal design solutions than for the conventional air-

plane.

WISE crafts typically cruise at small to moderate

angles of attack over the water surface, but they occa-

sionally ﬂy at large angles of attack when they need

to climb to avoid an emergency obstacle or are af-

fected by random gusts and water waves. Therefore,

for safe ﬂight operation of a WISE craft, it is impor-

tant to study the aerodynamic performance of WISE

crafts. There are several major situations that need to

be considered for the case of a WISE vehicle operat-

ing in a sea environment:

• ﬂoating and drifting in waves,

• take off in waves,

• landing in waves, cruise ﬂight over waves, the oc-

casional impact of the waves and, in an excep-

tional case, of rogue waves upon the vehicle and

its elements.

In the current research, a numerical study was car-

ried out to investigate the aerodynamic characteristics

of the wing in surface effect on the section design of

the wing. The study will hopefully be achieving im-

proved WISE-craft designs. In this study, ﬁnite ele-

ment software is used to simulate the ﬂow around the

wing of WISE. The various design of wing sections

are investigated and the ﬂow around the wing is ana-

lyzed.

2 LITERATURE REVIEW

2.1 History of WISE

Wing-In-Surface Effect (WISE) craft is a marine craft

equipped with wings which enables it to remain air-

borne just above the water surface. WISE trans-

portation vehicles have attracted considerable atten-

tion in view of their potential civil and military appli-

cations. Some of the beneﬁts of WISE-craft include a

high-speed operation (compared to traditional marine

craft), improved payload and aerodynamic efﬁciency

(Fuwa and Hirata, 1993).

One of the earliest WISE craft which contributed

signiﬁcantly to WISE-craft technology was the Rus-

sian Ekranoplan. A series of Ekranoplan, namely the

SM and KM series, has been successfully constructed

by Russian engineers. They all share some common

characteristics, such as an aircraft-like conﬁguration

(wing, fuselage, and tail), a rectangular wing with low

aspect ratio, together with a large and high tail for

longitudinal ﬂight stability. One obvious feature of

the Ekranoplan is the use of Power Augmented Ram

(PAR) to assist takeoff by directing the exhaust air

from the engine over the main wing. Another type

of WIG-craft, which is characterized by a Reversed

Delta wing and a high tail conﬁguration, has been de-

signed by Lippisch, a German aerodynamicist. The

Lippisch type of WISE-craft is the only one that has

proven to be inherently stable in surface effect (SE)

(Barber and Hall, 2006).

The WISE vehicle is a promising means of trans-

portation since it utilizes the favorable ground ef-

fect (Rozhdestvensky, 2000). It lies between a sea-

going ship and an aircraft in terms of its characteris-

tics. It is generally faster than the ship and has much

lower fuel consumption than an airplane. The WIG

craft would have application wherever there are: (a)

signiﬁcant spans of overwater operations; (b) inade-

quate aircraft operational bases to support airline op-

erations; (c) beaches or simple port unloading facili-

ties for roll on-roll off operations. WISE craft char-

acteristics exceed those of ship and aircraft because

of it can carry greater than aircraft payloads over sig-

niﬁcant distances at general aviation aircraft speeds

(Yang et al., 2015). By now, a number of WISE

crafts have been developed and manufactured, and

even some have been in commercial operation (Kubo

and Rozhdestvensky, 1997).

2.2 WISE as an Overseas

Transportation

Only two available modes of overseas transportation

are currently available: aircraft and ships. However,

the speed of conventional ships is less than 50km/h

(large container ships), while that of air-freighters is

over 800km/h. Meanwhile, the freight cost of an air-

plane is ten to twenty times higher than that of a con-

tainer ship on the basis of weight. There are large

gaps in speed and fare in which these two forms of

transportation are subject to operational inefﬁciency.

Consequently, cargo and passengers whose demand

for speed and price coincide with this gap are forced

to choose a mode from these two extremes of air- and

sea-transportations. This leads to the non-optimal and

non-efﬁcient use of transportation resources. Mean-

while, the economical service speed of WISES, aided

by surface effect, is from 200km/h to 500km/h, which

is suitable for meeting potential transport demand

around this gap (AKIMOTO et al., 2010).

The construction cost of a WISES is expected

to be less than that of an airplane of the same size.

WISES design requirements and regulations are mod-

erate in comparison to those governing airplanes be-

SENTA 2018 - The 3rd International Conference on Marine Technology

154

cause WISES is categorized as a ship. The low as-

pect ratio and thick wing of WISES are easy to con-

struct. Furthermore, a pressurized cabin is unnec-

essary, thus reducing fatigue strength requirements.

For WISES navigates only in very low altitude, its

governing regulations are those of ships. Therefore,

requirements of safety, structural strength and pilot

trailing of WISES are lighter than in aviation laws.

It differentiates WISES from seaplanes those tend to

be high-cost airplanes.

Although a WISE appears similar to an airplane,

it has different properties from the standpoint of com-

mercialization. The ship experiences hydrodynamic

loads while taking off from and alighting on water.

Although there is no explicit limitation to the length

of water runways, the speed at take-off and alight has

a great inﬂuence on the ship’s economy. As accel-

eration before take-off occurs on water, the required

power of the vehicle is nearly proportional to the cube

of take-off speed. In addition, the maximum hydrody-

namic load of the ship is proportional to the square of

the speed. Therefore, a decrease in take-off speed al-

lows for a smaller engine and lighter structural weight

of the vehicle. Slow take-off and alighting (STOA)

capability is important for reducing both the construc-

tion and operational cost of the ship (KAWAKAMI

and AKIMOTO, 2006).

2.3 Experimental and Numerical Study

on WISE

The aerodynamic characteristics of 2D airfoils and 3D

WISE have been investigated both experimentally and

numerically by other researchers (Fuwa and Hirata,

1993). The general conclusion is that there is a re-

duction in induced drag and an increase in lift as the

ground is approached. As a result, both aerodynamic

efﬁciency and aerodynamic loading are increased due

to ground proximity effects. Pioneer researchers such

as Kumar (1972), Irodov (1974), and Staufenbiel and

Schlichting (1988) have analyzed various aspects of

WISE craft longitudinal stability.

Ho et al. (2008) also investigated the effects of

end plate (numerically) on a highly cambered aero-

foil. Aerofoil shape optimization underground effect

had been carried out by Moore et al. (2002). Studies

have shown that the ground has a signiﬁcant inﬂuence

on the pressure distributions along the wing surface.

As a WIG vehicle moves forward, the speed of the on-

coming air gradually decreases under the lower wing

surface, and dynamic pressure changes to static pres-

sure. This increased pressure is called an air cushion

or a ram effect, and it necessitates a longer runway for

landing.

Technical feasibility of WISE vehicles (possibil-

ity to develop lifting systems taking advantage of SE

and able to perform stable ﬂight in proximity to an un-

derlying surface) has been proven both through model

experiments and full-size trials of prototypes.

Different aerodynamic conﬁgurations have been

developed and examined, each of them showing ad-

vantages and disadvantages from the viewpoint of

speciﬁc applications. A tendency is observed for con-

ﬁgurations to evolve into all-wing (ﬂying wing) or

composite wing schemes, the latter being particularly

advantageous from the viewpoint of efﬁcient take-

off, aerodynamic (economic) viability in cruise and

a wider range of pitch stability.

Extensive wind tunnel tests were carried out in

the closed-type wind tunnel at Pusan National Uni-

versity. Lift and drag forces and the pitch moment

of NACA6409 was measured as several aerodynamic

parameters such as the aspect ratio (AR), the angle of

attack (α), ground clearance (h/c) and endplate shape

were varied. In addition, the smoke trace technique

was employed to visualize the ﬂow pattern around

the wing during the ground effect. This experimen-

tal study presents how the aerodynamic performance

of NACA6409 during the ground effect is inﬂuenced

by various design parameters (Jung et al., 2008).

In 2006, Al-Atabi (2006) ﬁtted three small lifting

surfaces to the tip of a NACA0012 wing similar to that

of the wing tip feathers, the tests show that tip-sails

could decrease the induced drag, increase the longi-

tudinal static stability and break the tip vortices. In

1977, Withers and Timko (1977) recorded motion pic-

ture of black skimmers ﬂapping and skimming over a

water surface by the camera. The ﬂight velocities and

the wing-beat frequency were achieved by analyzing

the ﬁlms. The conclusion is that ground clearance

has a great effect upon the foraging energetics and

daily energy balance of skimmers. The experimen-

tal results of Ground Effect of a wing mounted with

tip sails are introduced by Sun and Dai (2015). The

study has evaluated the ﬂow control efﬁciency of pri-

mary feathers to the wing of a pelican skimming over

the water surface. Compared with a NACA4412 pro-

totype wing, the experimental results show that, for

the same ground clearance, the lift coefﬁcient of the

tip-sails wing increases signiﬁcantly and the stalling

angle of attack decreases, the drag coefﬁcient keeps

nearly unchanged at a small angle of attack (AOA)

and decreases obviously at higher AOA.

Numerical Study on the Section Design of a Wing in Surface Effect

155

Figure 1: WISE (Trimaran) Craft Model

Table 1: Foil Shapes Modiﬁcation on WISE’s Wings

No. Foil Shape

1. NACA 0006

2. NACA 4412

3. NACA 6409

3 COMPUTATIONAL FLUID

DYNAMIC

3.1 Geometry and Modelling

Prior to the CFD analysis carried out for prediction

of the lift force, 3D hull form of the trimaran vessels

was generated with CAD software. The trimaran ves-

sels are designed to have ailerons on her starboard and

port to help her maneuvers. In addition, in the tail sec-

tion of the vessel is given a pitching stabilizer which

is useful to help the vessel in the process of taking

off and landing. The vessel’s propeller is located on

the top of the vessel and is supported by a rudder on

the back of the vessel. The WISE craft 3D model is

shown in Figure 1.

In this paper, the 3D hull forms were developed

with 3 (three) modiﬁcations of foil shapes on her main

wings, as in Table 1. The modiﬁcations on her wings

are expected to minimize the craft’s resistance, thus

increasing the lift forces. At the end of the research,

the most optimum wing shape will be selected to be

made a prototype.

3.2 Mesh Generation

The next stage after the 3D model is created is to di-

vide the model geometry into small elements (trian-

gles, tetra/mixed, hexa-dominant) called a cell. These

cells form a unity called mesh or grid due to their

conﬁguration which looks like mesh, thus this process

stage is commonly called as meshing. Mesh is of con-

siderate importance for computational purposes. The

mesh size of the vessel can be seen on Figure 2 below.

3.3 Boundary Condition

The model that has been meshed then will be set up

appropriate boundary conditions to run simulation of

free ﬂight. The boundaries that were created namely:

Figure 2: Mesh Size of the Trimaran Vessel

Table 2: Boundary Condition

Boundary Type Conditions

Inﬂow Inlet Normal speed 16.2 knots

Outﬂow Outlet Static Pressure 0 Pa

Wall Wall Free slip wall

Ground Wall No slip wall, smooth wall

WISE Wall No slip wall, smooth wall

inﬂow, outﬂow, wall, top, and bottom. After the

boundaries have been made, each boundary will be

deﬁned as can be seen on the Table 2 below.

4 COMPUTATIONAL RESULTS

AND ANALYSIS

4.1 Lift Force

The lift forces of the three WISE crafts are presented

in Table 3 with respect to varying the foil shape of her

main wings at her service speed, i.e 16.2 knots. As

it can be seen on the table, the highest lift force was

generated by NACA 4412, followed by NACA 6409,

and lastly, NACA 0006 placed at the bottom.

Table 3: Boundary Condition

Boundary Type Conditions

Inﬂow Inlet Normal speed 16.2 knots

Outﬂow Outlet Static Pressure 0 Pa

Wall Wall Free slip wall

Ground Wall No slip wall, smooth wall

WISE Wall No slip wall, smooth wall

4.2 Surface Pressure

Figure 3 up to Figure 5 provided an overview of

the total pressure distributions around the three crafts

with the same speed and height in cruise. WISE with

NACA 4412 wing foil shape indicated that higher

negative pressures were recorded along the vessel’s

SENTA 2018 - The 3rd International Conference on Marine Technology

156

wing surface. Higher negative static pressure, cor-

responding to the reference static pressure from the

inﬂow, was found near the leading edge of the wing.

This results in an increase of lift forces on the wings

of the vessel.

Figure 3: Surface Pressure Distribution on WISE [NACA

0006]

Figure 4: Surface Pressure Distribution on WISE [NACA

4412]

Figure 5: Surface Pressure Distribution on WISE [NACA

6409]

4.3 Flow Visualization

Figure 6 up to Figure 8 show the ﬂow pattern around

the three WISE crafts at the speed of 16.2 knots which

represents service speed.

Figure 6: Flow Patter around WISE [NACA 0006]

Figure 7: Flow Patter around WISE [NACA 4412]

Figure 8: Flow Patter around WISE [NACA 6409]

5 CONCLUSIONS

A detailed numerical investigation of the aerody-

namic characteristics of a WISE craft for various de-

sign of wing section using NACA series, it can be

summarized that NACA 0006 gives the lowest lift

forces and the design of NACA 6409 generate the

highest lift forces. Therefore, it can be concluded,

design of wing section using NACA 6409 more rec-

ommended for the WISE craft in speed 16.2 knots.

Numerical Study on the Section Design of a Wing in Surface Effect

157

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