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Aerodynamically alleviated marine vehicle

April 12, 2024

An aerodynamically alleviated marine vehicle (AAMV) is a high speed marine vehicle configuration that uses aerodynamically generated forces (lift) to 'alleviate' its weight. The advantage is that the hydrodynamic lift required to sustain the weight of the vehicle is diminished, leading to a diminished hydrodynamic drag. The vehicle is in constant contact with the water, therefore the aerodynamic surfaces operate in ground effect. The name derives from the "Aerodynamic Alleviation Concept", presented by L.J. Doctors to illustrate the positive effect of using a wing-like superstructure on a catamaran configuration.[1]

Literature review edit

In 1976, Shipps,[2] among other air-supported waterborne vehicles, analyzed a new kind of race boats, known as 'tunnel hull' race boats. Two planing sponsons act as aerodynamic end plates of the central 'channel flow' or ram wing. These race boats immediately demonstrated to have better performances with respect to the conventional monohull race boats and a new race boat class was created. The advantages of this new configuration come from the aerodynamic lift. The additional aerodynamic lift can be equal to the 30-80% of the total weight of the marine vehicle. This means a lower hydrodynamic lift needed, therefore a lower chine and keel wetted length and a decreased hydrodynamic drag. Furthermore, the flow in the tunnel hull acts as an air cushion, damping the heave and pitch oscillation: the oscillations of the craft are smoother. Otherwise this aerodynamic lift can create safety and stability problem. Sometimes the craft, for example after a wave, can lose contact with the water. Generally the aerodynamic center is located upward with respect to the center of gravity, therefore when the vehicle jumps off the water the pitch moment is unbalanced and the vehicle performs a pitch-over. More generally, Shipps believed in the possible development of air-supported waterborne vehicle, capable of better performances, and suitable for littoral scenarios as well as for offshore scenarios.

In 1978, Ward et al.[3] published an article on the design and performance of a ram wing planing craft: the KUDU II (KUDU I was mentioned in Shipps' article). This vehicle can be considered an AAMV, since it has two planing sponsons separated by a wing section. Therefore, it is a vehicle with aerodynamic and hydrodynamic surfaces, designed to obtain aerodynamic and hydrodynamic lift. In his article Ward presented the results of some trials: the KUDU II was able to run at 78 knots (144 km/h).

In 1978, Kallio,[4] of the David W. Taylor Naval Ship Research and Development Center, performed comparative tests between the KUDU II and the KAAMA. The KAAMA is a conventional mono-hull planing craft. The data obtained during comparative trials show that the KUDU II pitch motion, in sea state 2, at about 40 to 60 knots (110 km/h), is about 30% to 60% lower than the conventional planing hull KAAMA. Unfortunately the KUDU II sustained severe damages during the trials, therefore there are little data available to compare.

In 1996, Privalov and Kirillovikh [5] presented a new vehicle concept called TAP, Transport Amphibious Platform. It can be considered an AAMV. The TAP consists in two hulls, like a catamaran, and a fuselage, a wing and an aerodynamic tail in between the hulls. It moves always in contact with the water and uses an aerodynamic cushion effect, obtained by forcing the powerplant gas jets beneath the platform between the hulls. The authors assess that the advantages of the TAP are:

  • the high speed, compared to air cushion vehicles and ships (around 250 km/h),
  • amphibious capability,
  • high cargo-carrying capacity, also due to his higher weight efficiency, obtained by a more simplified structural scheme as compared to hovercraft and WIGe vehicles.

This vehicle seems to be very promising,[according to whom?] however the authors presented only performances estimation of the TAP, without disclosing any detail on the dynamics model adopted.

In 1997, Doctors [1] proposed a new configuration called Ekranocat for which he mentioned the aerodynamic alleviation concept. The weight of the catamaran is alleviated by aerodynamic lift, thanks to a more streamlined superstructure than in traditional catamarans. The theoretical analysis and computed results show that reductions in total drag around 50% can be obtained at very high speed.

See also edit

References edit

  1. ^ a b Doctors, L. J., “ANALYSIS OF THE EFFICIENCY OF AN EKRANOCAT: A VERY HIGH SPEED CATAMARAN WITH AERODYNAMIC ALLEVIATION”, International Conference on Wing In Ground Effect Craft (WIGs '97), RINA, 1997
  2. ^ Shipps, P. R., “HYBRID RAM-WING/PLANNING CRAFT - TODAY'S RACEBOATS, TOMORROW'S OUTLOOK”, AIAA/SNAME Advanced Marine Vehicles Conference, 1976
  3. ^ Ward, T. M., Goelzer, H. F., Cook, P. M., “DESIGN AND PERFORMANCE OF THE RAM WING PLANING CRAFT - KUDU II”, AIAA/SNAME Advanced Marine Vehicles Conference, 1978
  4. ^ Kallio, J. A., “RESULTS OF FULL SCALE TRIALS ON TWO HIGH SPEED PLANING CRAFT (KUDU II AND KAAMA) ”, David W. Taylor Naval Ship Research and Development Center, 1978
  5. ^ Privalov, E. I., Kirillovikh, V. N., “TRANSPORT AMPHIBIOUS PLATFORMS: A NEW TYPE OF HIGH-SPEED CRAFT”, Workshop Proceedings of Ekranoplans & Very Fast Craft, 1996

External links edit

  • , history of Wing-In-Ground craft

April 12, 2024
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An aerodynamically alleviated marine vehicle AAMV is a high speed marine vehicle configuration that uses aerodynamically generated forces lift to alleviate its weight The advantage is that the hydrodynamic lift required to sustain the weight of the vehicle is diminished leading to a diminished hydrodynamic drag The vehicle is in constant contact with the water therefore the aerodynamic surfaces operate in ground effect The name derives from the Aerodynamic Alleviation Concept presented by L J Doctors to illustrate the positive effect of using a wing like superstructure on a catamaran configuration 1 Contents 1 Literature review 2 See also 3 References 4 External linksLiterature review editIn 1976 Shipps 2 among other air supported waterborne vehicles analyzed a new kind of race boats known as tunnel hull race boats Two planing sponsons act as aerodynamic end plates of the central channel flow or ram wing These race boats immediately demonstrated to have better performances with respect to the conventional monohull race boats and a new race boat class was created The advantages of this new configuration come from the aerodynamic lift The additional aerodynamic lift can be equal to the 30 80 of the total weight of the marine vehicle This means a lower hydrodynamic lift needed therefore a lower chine and keel wetted length and a decreased hydrodynamic drag Furthermore the flow in the tunnel hull acts as an air cushion damping the heave and pitch oscillation the oscillations of the craft are smoother Otherwise this aerodynamic lift can create safety and stability problem Sometimes the craft for example after a wave can lose contact with the water Generally the aerodynamic center is located upward with respect to the center of gravity therefore when the vehicle jumps off the water the pitch moment is unbalanced and the vehicle performs a pitch over More generally Shipps believed in the possible development of air supported waterborne vehicle capable of better performances and suitable for littoral scenarios as well as for offshore scenarios In 1978 Ward et al 3 published an article on the design and performance of a ram wing planing craft the KUDU II KUDU I was mentioned in Shipps article This vehicle can be considered an AAMV since it has two planing sponsons separated by a wing section Therefore it is a vehicle with aerodynamic and hydrodynamic surfaces designed to obtain aerodynamic and hydrodynamic lift In his article Ward presented the results of some trials the KUDU II was able to run at 78 knots 144 km h In 1978 Kallio 4 of the David W Taylor Naval Ship Research and Development Center performed comparative tests between the KUDU II and the KAAMA The KAAMA is a conventional mono hull planing craft The data obtained during comparative trials show that the KUDU II pitch motion in sea state 2 at about 40 to 60 knots 110 km h is about 30 to 60 lower than the conventional planing hull KAAMA Unfortunately the KUDU II sustained severe damages during the trials therefore there are little data available to compare In 1996 Privalov and Kirillovikh 5 presented a new vehicle concept called TAP Transport Amphibious Platform It can be considered an AAMV The TAP consists in two hulls like a catamaran and a fuselage a wing and an aerodynamic tail in between the hulls It moves always in contact with the water and uses an aerodynamic cushion effect obtained by forcing the powerplant gas jets beneath the platform between the hulls The authors assess that the advantages of the TAP are the high speed compared to air cushion vehicles and ships around 250 km h amphibious capability high cargo carrying capacity also due to his higher weight efficiency obtained by a more simplified structural scheme as compared to hovercraft and WIGe vehicles This vehicle seems to be very promising according to whom however the authors presented only performances estimation of the TAP without disclosing any detail on the dynamics model adopted In 1997 Doctors 1 proposed a new configuration called Ekranocat for which he mentioned the aerodynamic alleviation concept The weight of the catamaran is alleviated by aerodynamic lift thanks to a more streamlined superstructure than in traditional catamarans The theoretical analysis and computed results show that reductions in total drag around 50 can be obtained at very high speed See also editWing in ground effect vehicle Surface effect shipReferences edit a b Doctors L J ANALYSIS OF THE EFFICIENCY OF AN EKRANOCAT A VERY HIGH SPEED CATAMARAN WITH AERODYNAMIC ALLEVIATION International Conference on Wing In Ground Effect Craft WIGs 97 RINA 1997 Shipps P R HYBRID RAM WING PLANNING CRAFT TODAY S RACEBOATS TOMORROW S OUTLOOK AIAA SNAME Advanced Marine Vehicles Conference 1976 Ward T M Goelzer H F Cook P M DESIGN AND PERFORMANCE OF THE RAM WING PLANING CRAFT KUDU II AIAA SNAME Advanced Marine Vehicles Conference 1978 Kallio J A RESULTS OF FULL SCALE TRIALS ON TWO HIGH SPEED PLANING CRAFT KUDU II AND KAAMA David W Taylor Naval Ship Research and Development Center 1978 Privalov E I Kirillovikh V N TRANSPORT AMPHIBIOUS PLATFORMS A NEW TYPE OF HIGH SPEED CRAFT Workshop Proceedings of Ekranoplans amp Very Fast Craft 1996External links editThe WIG Page history of Wing In Ground craft Retrieved from https en wikipedia org w index php title Aerodynamically alleviated marine vehicle amp oldid 1156824030, wikipedia, wiki, book, books, library,

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