THE PRELIMINARY INVESTIGATIONS AND THE MAIN PRINCIPLES OF
SUPER-HIGH-SPEED VESSEL “GLIDING WING”
(Conceptual design)
Associate Professor, Roko Markovina, Ph.D.
University of Split, Faculty of Electric Engineering, Mechanical Engineering and Naval Architecture
R. Boškovića b.b. , Split
C R O A T I A
Summary:
In the paper, some thinking has been given on needs and possibilities of modern super-high-speed vessel. This idea refers to the preliminary design for "GLIDING WING" as a vessel with the speed over 100 knots, with flying and landing possibilities on the sea surface, using the screen-plane and WIG (Wing – in – Ground) effect, with the maximum speed of about 250 knots, and finally the variant “Spalato”, as the first phase in investigations, which can glide on the sea surface with the speed up to 80 knots.
This vessel is an original concept based on the optimum use of both media (air, water) using aerodynamic effects, load carrying capability and hydrodynamic lift for flying and stabilization of vessels, as well as for decreasing total resistance.
Key words: super-high speed vessel, flying-landing maneuver, soil effect, load carrying capability, profile rising, total resistance.
1. INTRODUCTION
A fast transportation of people and goods is a request which has been expressed today more than ever before. Railway, air and road transportation, which make 1/3 of the total world transport, have partly resolved this request by using modern high-speed passenger and cargo vehicles. However, the maritime traffic, which makes 2/3 in the world transportation, has not yet reached that level, although experts have worked for years on the plans of super-high-speed vessels.
A policy of the maritime traffic should give a serious consideration to this fact, both for the coastal navigation and for the overseas one, because the maritime traffic in relation to the land-air traffic is still: the safest, the most attractive and, finally, the cheapest, which will be the case for a long time.
It is known that in Europe, the Far East and the USA several teams work on secret projects in order to plan and produce the vessel of the "new generation", i.e. "super-high-speed" vessel, which would meet the requirements of the modern time with its characteristics.
For such vessels, it is necessary to resolve:
- the question of drive for high speeds (80-100 knots)
- the application of modern materials and special technologies with the purpose of decreasing the vessel's own weight (like in the aircraft industry),
- the question of "new" ways of working out of elements, under-assemblies, and assemblies (integral skins, honeycomb structures, sandwich panels, composite structures etc.)
- the application of improved classical means of connecting, and introducing the new ones (a new welding methods and metal-metal gluing),
- the question of automatisation and stabilization of the vessel for new maritime requirements,
- the question of providing maritime routes ("corridors") for the navigation of super-high-speed vessels, etc.
Throughout the development of WIG – vessels, numerous plans for configuration have been built and tested. The variations in shape include the rectangular plan form, the conventional delta, the trapezoid, the reverse delta and the forward swept plan form. In Fig.1 the typical shapes of WIG – effect are shown.
All these shapes will be in the function of:
- an ever more quality using of the ground effect,
- a speed gliding on the water surface, and
- a free air – flying.
Figure 1: Typical area shapes of the WIG – effect ( 4 )
The system of hydroplane, in the case of “Gliding wing” will be used, i.e. gliding on the sea surface, with possibility of a low altitude flight, without the classic “wing – span”. But the WIG – effect would be use in the second phase of development of “Gliding wing”
The conventional shipbuilding has not resolved this so far because it has not been forced to, because it has not had any competition and the aircraft industry has been preoccupied with its own problems. All this requires, of course, significant investments.
Today, a typical form of fast vessels for mass transportation (Monostub, catamarans - SES, SWATH, WAVE-PIERCER, etc.) as shown in Fig. 2 have the usual speeds:
- the buoyancy vessels…………..30 – 35 knots, and 300 – 500 passengers,
- the hydrofoils vessels…………40 – 45 knots, and 80 – 100 passengers and
- the air - cushion vessels………45 – 50 knots, and 100 – 150 passengers.
Of course, the conventional catamarans use buoyancy for support with small amount of dynamic lift and can achieve speeds up to 40 knots, with good efficiency, but to go faster, hydrofoils and air – cushion system vessels are needed. For the speeds of 50 knots for the hydrofoils the cavitations become a mayor problem, but the air – cushion vehicles work the best. Today’s hydrofoil and aircushion vehicles are much more expensive than catamarans paying for unusual speed. They are built mostly of Al-alloys with conventional building techniques.
However, a new sciences results, and great experience in aircraft industry can give a good platform for the design of the vessel which will overcome the previous ones regarding speed, form, applied technologies, quality and highly demanding world standards. The aircraft technologies and the modern shipbuilding experience can and must help in this respect.
This paper tries to present the conceptual design of the new super-high-speed vessel through a short preliminary explication of "GLIDING WING", and at the end, one of possibilities, the short general arrangement of “Spalato”, as a very fast trans-Adriatic vessel, the first of this “GLIDING WING” family.
The idea for this project was born even in 1990 in the Aircraft Industry "Soko" - Mostar (Bosnia and Herzegovina) by Faruk Dizdarevic, civil engineer of aircraft industry (now a refugee in the USA) and the author of this paper in a few variants, and was protected the following year.
Figure 2: Typical forms for high – speed vessels
It has not been much done so far due to the war and financial shortages. A small information was done in the papers on The XIII Croatian shipbuilding symposium “SORTA 98“ in Zadar – Croatia, and IX Congress “IMAM 2000.” in Naples – Italy, and on the Second Paneuropean Shipping Conference in Split (Croatia) in 2001.
2. IN GENERAL
Taking into consideration that a vessel which would meet the requests of modern times with the aim of multi-purpose and super-fast connecting islands and littoral has not yet been designed, it is a time to offer the preliminary solution of the vessel which would have to meet the following requirements:
- to arrive at its destination in as short time as possible,
- to stay in ports as shortly as possible,
- to enable a safe and comfortable navigation at all sea and almost all weather conditions,
- to enable the multi-purpose use, i.e. to earn money even when it is not in the function of transporting passengers and/or goods,
- to have all necessary facilities for a pleasant stay of passengers during the navigation and outside of it,
- to have enough fuel, grease, drinkable and other water and supplies for the longest range,
- to enable the crew a safe and comfortable work,
- to be built in accordance to the good shipbuilding tradition, meeting the requirements of the classification societies, IMO-resolutions SOLAS-conventions and other regulations for the building of means of communication,
- to meet the standards of the environmental protection ("green vessel").
It is well known that the greatest need for a quick maritime transport lies in connecting numerous Mediterranean islands, especially in the Adriatic Sea, Aegean Sea and the others, knowing well that the islands are a special entity in every respect, considered demographic, cultural, economical, historical, climatic points of views, and also, because they are surrounded by the sea, and need a good transportation. Talking into consideration that islands are the part of state territory, some countries (USA, Norway) consider the connecting of islands as a part of the road traffic; for shorter distance (up to 10 Nm) they use ferry-boats with a speed about 12 knots, and for greater distances they use the speed-vessels up to 40 knots. If the ferry - traffic is considered as a road-traffic, the classic and high-speed passenger - transport is considered as a bus-traffic, so the super high-speed passenger and goods transport has to be considered as an aircraft-traffic. It is evident that a speed of passenger’s ships at various distances depends, in the first place, on the economical strength of a country, but also on the length of the line, structure and needs of population and, finally, on the state and regional policy towards islands. The vessel's speed up to 40 knots today are considered “middle”, and passengers, who have money to pay for a high-speed transport and which have no time to spend a days for slow transport, merit to use a super-high speed vessels, either for business traffics or holliday-turist transportations.
The modern shipbuilding industry must ensure these needs by building super-high speed vessels of a new generation.
This means that the vessel must be conceived in accordance with the requirements of a passenger ship but that it can also serve, with small modifications, for the transport of cars, buses, heavy vehicles, containers and other packed load, at all sea conditions. It must have a minimal own weight, without a robust and heavy propulsion arrangement, and it must meet the requirements of speed above the so far one, i.e. it must have speed up to100 knots. This vessel have to be built of Al-alloys and other modern materials, a various kinds of "sandwich" and honey-comb structures, while meeting the requirements of strength and applying modern technologies wherever possible.
Estimating that sixth generation of catamarans must have a completely new form and conception might meet these requirements, the “GLIDING WING”, as the preliminary solution, is capable to give the answers to several previous questions.
3. THE MAIN PRINCIPLES AND «PHILOSOPHY»
The main principles of the new generation vessels are to use, except for the classic shipbuilding particularities, the airfoil advantage in hull form of the vessel. As it is known, an airfoil generates lift by changing the velocity of the air passing over and under the hull body. The airfoil angle of attack and/or camber cause the air over the top of the wing to travel faster than the air beneath the wing. The same phenomenon can be used in the case that the hull body has the airfoil form, using the Bernoulli's equation for non-compressed air, which shows that higher velocities produce lower pressures, so the upper surface of the airfoil tends to be pulled upward by lower- than-ambient pressures, and the lower surface of the airfoil tends to be pushed upward by higher-than-ambient pressures.
………………………………………….(1)
where are:
,
When h1=h2 and ξ=0, the equation is:
…………………………………………………..(2)
For than reason the integrated differences in pressure between the top and the bottom of the airfoil hull form generate the net lifting force.
As Fig.3a illustrates, we can see the key geometric parameters of an airfoil. A leading -edge radius defines the front, which is tangent to the upper and lower surfaces. The cord of the airfoil is the straight line from the leading edge to the trailing edge. But, as it is very difficult to build a sharp trailing edge, most airfoils have a blunt trailing edge with some small finite thickness. The «mean camber line» is the line equidistant from the upper and lower surfaces, and «total airfoil camber» is defined as the maximum distance of the mean camber from the chord line, expressed as a percent of the cord.
Figure 3a: The airfoil geometry
The thickness distribution of the airfoil is the distance from the upper surface to the lower surface, measured perpendicularly to the mean camber line, and is a function of the distance from the leading edge.
«The airfoil thickness ratio»(t/c) refers to the maximum thickness of the airfoil divided by its chord.
Figure 3b: Typical airfoil distribution
Fig. 3b present a typical pressure distribution for the upper and lower surfaces of a lifting airfoil at subsonic speed, and it shows that the upper surface of the wing form contributes about two-thirds of total lift.
Figure 3c: Airfoil flow field and circulation
Fig. 3c illustrates the flow field around a typical airfoil as a number of airflow velocity vectors. It can be seen that the effect of airfoil is to introduce a change in airflow, which seems to circulate around the airfoil in clockwise fashion, if the airfoil nose is to the left. The circulation is the theoretical basis for the classical calculation of lift and drag-due-to lift. Practically, the greater circulation gives the greater lift, and is usually represented by Γ and is shown as a circular flow in Fig.3c.
If an airfoil profile is used, as the hull form of vessel, we have to define its aerodynamical characteristics, firstly:
- lift force on a section by:
,…………………………………………………………….(3)
and circulation by:
………………………………………………………………………………(4)
The task is to find out the additional velocity and real attack angle in each section of airfoil hull of vessel, as the low of circulation distribution Γ (y) along the wing.
The additional velocity Vz in point y1 is:
,……………………………………………………………………(5)