KR20110076946A - Hull form intended for vessels provided with an air cavity - Google Patents

Abstract

The linearity of ships with large flat lower area fits the principle of air cavities and can utilize the principle of air cavities. The line reduces the wet surface of the hull and reduces motion in the sea, making the ship less bunker-consuming and power demanding, making it suitable for offshore sea navigation.

Description

HULL FORM INTENDED FOR VESSELS PROVIDED WITH AN AIR CAVITY

The present invention relates to the hull form of ships.

One of the most important parameters in all shipbuilding is the relationship between speed and power. For commercial ships, frictional resistance, ie friction between underwater hull and water, is the dominant part of the ship's overall resistance. For high speed vessels, for example, wave resistance only matters when the speed increases. Efforts have been made to influence frictional resistance with different types of air lubrication and different types of surface structures. However, the results of conventional merchant ships have been negative so far.

Another way to reduce frictional resistance is to reduce the area of the wet surface. The wet surface is the hull portion of the water, which is in contact with the surrounding water when the velocity is zero.

The wet surface can be reduced by the planar bottom face of a portion of the underwater hull, which is carried out with a cavity filled with air, hereinafter referred to as an air cavity. Air then has the same pressure as the surrounding water. Because of the ship's advancement, some of the air can escape and then the air that has escaped is compensated with freshly supplied air. Air may be supplied to the cavity through the ceiling of the vessel and the sides of the vessel. A cavity that can be compared to a box with the opening facing down so that the upside down box does not cause an increase in resistance in the form of increased vortex and bubble when water passes under the cavity It should have a shape that is adequate enough to prevent it. In today's alignments, the water of the forebody often flows from the inner side of the underside of the vessel towards the centerline of the vessel. This means that a wave crest is formed in the air cavity, which interferes with water flow. Also, the linears today only mean that the sides of the air cavity over a relatively short distance are parallel to the ship's centerline. The sides of the air cavity at the forward and stern of this portion have a fairly large angle to the centerline. The flowing water then hits each other's sides, resulting in increased resistance. When the ship enters the high seas, the ship can roll in the transverse direction, i.e. repeat the rotational or pitch motion about the longitudinal axis of the centerline of the ship, i.e. The rotational motion can be repeated about the horizontal transverse axis at the central point of or a combination thereof, and the air can flow outwards at the highest positioned side of the air cavity. Navigational performance is of great importance accordingly, in order to avoid the increase of vortices on the sides of the air cavity as well as to reduce the need for air supply by reducing the outflow of air. The interface between air and water in the cavity is aimed at a horizontal level where there is a balance between air pressure and lower hydraulic pressure. The interface should be as close to the bottom of the air cavity as possible. If the vessel is exposed to large rolling or pitch motion, the boundaries of certain parts will be well above the bottom of the air cavity. This results in a strong vortex increase along the sides of the cavity, resulting in increased resistance. As a result, the air cavity should be formed so that the result of motion is reduced as much as possible. Therefore, it has been proposed to divide the air cavity into partition walls of the air cavity not only in the longitudinal direction but also in the transverse direction to reduce the result of the motions in the sea. Four air cavities are then obtained, each of which is supplied with air separately. The risk of transverse partition walls obviously increases the vortex once again, resulting in increased resistance.

Therefore, for the principle that the frictional resistance is reduced by cavities filled with air in the lower part of the plane to actually work, the linearity of the ship must be provided in a special form and its navigational performance must be improved. A further problem is that the exhaust air must not enter the water with the propellers, because this reduces the efficiency of the propellers. In the literature, proposals have been made which attempt to deflect the water / air mixture by different devices and that this does not affect the propeller region. Such induction of forced water / air flow also creates additional resistance.

All of the above-mentioned challenges have so far been that the principle of air cavities does not lead to any practical application to conventional vessels operating in oceanic routes.

It is an object of the present invention to provide a large flat lower area and to provide a new linear fit to the principle of air cavities and to utilize the principle. The linearity thus reduces or even eliminates the above-mentioned disadvantages, thereby reducing motion in the sea, resulting in a reduction in power demand and bunker consumption, making the ship suitable for off-shore navigation.

The invention is defined in the appended claims 1. Embodiments of the invention are defined in the appended dependent claims.

Most modern merchant ships have some form of information bulb in the bow. In order for the bulb to be in a particular position, the transverse frame at this position must have a waist, and the width of the frame must be greater than the waist as well as the top. By the bulb in the bow, it is possible to obtain a reduction in the sowing resistance to some extent. The cross section of the previous bulb of the forward perpendicular (FP) for conventional vessels is most often somewhat similar to the pointed ellipse. The bow vertical line is defined as a vertical line through the point where the Design Waterline (dWL) intersects the stem. The design waterline dWL is defined here as the waterline of the maximum summer draught that the vessel is allowed to operate in view of its power and stability.

However, the linearity of the bow portion according to the invention will be described as an ellipse which is characterized by a very wide, low and relatively thin bulb and the side of the front lying almost flat. To describe the bow in more detail, specific characteristic quantities of the bulb need to be defined.

The bulb length calculated from the foremost point of the underwater hull is the smallest of the two values below:

-The horizontal distance from the foremost point of the underwater hull to the position of the transverse frame, where the waist of the transverse frame of the bow is not visible or

2 times the horizontal distance calculated from the foremost point of the underwater hull to the foremost point of the fore profile in the waste.

The bulb volume is the volume of the hull plus the port, within the bulb length from baseline to the design repair.

The bulb area is the area projected on the horizontal plane of the bulb below the waist, plus the port, within the bulb length.

When the bulb volume is separated by the bulb area, the average thickness of the bow is obtained. When the bulb area is divided into bulb lengths, the average width of the bulb is obtained.

The bulb coefficient is now defined as the average width divided by the above-described interpolated amount or average thickness, and the following is obtained:

Known and published linears often obtain 0,5 to 1 bulb coefficients depending on the size and size of the hull. According to the alignment according to the invention, including the claims further explained below, the bulb coefficient should have a value of at least 1,5. The optimal value depends on the type and dimensional relationship of the vessel, but the value of the coefficient often approaches or exceeds the value of 3.

The bow edge of the bulb is wide, flat and relatively thin according to the above equation. The tip of the bulb should be somewhat above the baseline where the water flow is divided into a lower flow and an upper flow. The bottom flow must flow below the bulb and below the vessel, while the top flow must flow above the bulb and mainly travel along the sides of the vessel. Due to the proper distribution of each flow up and down the bulb a minimum overflow from the hull side to the bottom of the bow is obtained. The underside of the bulb in the front portion is straight or slightly curved outward from the centerline in the transverse direction. In the stern direction, the base of the bulb deforms continuously horizontally and parallel, and at the same time its width increases as it approaches the baseline. When the bottom reaches the baseline, the air cavity can start.

The following advantages can be obtained by the linear according to the invention:

넓고 편평한 벌브는 매우 넓은 공기 공동의 스타트 가능성을 발생시킨다. 상기 벌브가 넓을수록, 공기 공동의 더 넓은 스타트가 획득된다. 이것은 공기 공동의 에어리어를 증가, 즉, 습 선체 표면을 감소시키고, 결과적 마찰 저항을 감소시킨다.

Wide and flat bulbs create the possibility of starting very wide air cavities. The wider the bulb, the wider the start of the air cavity is obtained. This increases the area of the air cavity, ie reduces the wet hull surface and reduces the resulting frictional resistance.

공기 공동의 넓은 스타트는 최대 폭까지의 공기 공동의 측면들이 수중 선체의 중심선에 평행하게 있는 수직면에 대해 작은 각들을 형성함을 의미한다. 이것은 공기 공동의 측면들 위로 가로 방향으로 수류가 흐를 가능성을 감소시키는, 즉, 와류가 증가할 위험성이 감소한다.

A wide start of the air cavity means that the sides of the air cavity up to the maximum width form small angles with respect to the vertical plane parallel to the centerline of the underwater hull. This reduces the likelihood of water flow in the transverse direction over the sides of the air cavity, i.e. the risk of increased vortex is reduced.

본 발명에 따른 선형은 공기 공동 아래 선박의 중심선에 평행하고 실제로 직선의 수류를 제공하고, 이는 공동의 공기에 대한 고요한 작동 상태를 발생시킨다.

The linear according to the invention is parallel to the centerline of the ship below the air cavity and actually provides a straight stream of water, which creates a quiet operating state for the air in the cavity.

벌브 형상이 넓어짐으로써 배수량이 커지게 된다. 선수부에 배수량이 유지되는 경우, 이는 특히 dWL의 수선 폭이 감소할 수 있는 얇은(slender) 선박들을 의미한다. 이는 상기에 따라 공기 공동의 원리를 작동시키기 위해 중요했던 피치 방향-아래를 참조하라-으로의 선박의 모션 특성을 개선한다.

As the bulb shape becomes wider, the drainage volume increases. If drainage is maintained at the bow, this means especially slender vessels in which the dWL's waterline width can be reduced. This improves the ship's motion characteristics in the pitch direction-see below-which was important for operating the principle of the air cavity according to the above.

As the bow moves in the vertical direction, the wider bulb will attract a large amount of water with it. The wider bulb increases the so-called cavitation oscillation mass and increases the mass moment of inertia of the bow and stern polarity. At the same time, a wider bulb can mean that the repair width of the bow can be reduced just above and just below dWL. In this way, the moment aiming to return the vessel to its neutral position after vertical motion is reduced. Increasing the moment of inertia of polarity simultaneously with the reduction of the restoring moment means that the natural frequency decreases. This is beneficial because the risk is reduced, leading to sympathetic vibrations in the head sea for normal wave spectrums.

In addition, the broad bulb of the bow will increase the attenuation coefficient in the bow's vertical motion. Although the frequency is near resonance, the increased attenuation reduces the motion in the pitch direction.

The transverse moments for the monohull vessel are largely dependent on the ship's main dimensions. Since the air cavity reduces transverse stability, it may be necessary to divide the air cavity into a plurality of longitudinal chambers. These air cavities are then provided with separate air supply ducts.

By stern, the corresponding requirements of the linearity are applied so that the principle of the air cavity works optimally. Horizontal bulbs, such as the bulb of the invention of the bow, will be arranged in the lower stern portion of the rear hull. The linearity of the rear hull according to the invention is characterized by a relatively thin and low bulb with very large expandability in the transverse direction, which increases the lower face of the plane. Therefore, all transverse frames within the stern bulb length defined as follows must have a waist. To further illustrate the rear hull, a corresponding specific amount for the stern bulb is defined.

The length of the stern bulb is defined as 10% of the vertical length of the hull calculated from the stern point of the bulb below the waist in the bow direction. The vertical length is the horizontal distance between the front vertical line and the rear vertical line. The rear vertical line is a vertical line through the center of the rubber shaft or a vertical line through the point where the design waterline intersects the transom, if the vessel does not have a conventional rudder.

The bulb volume is the hull volume, with the port port added to the starboard, within the stern bulb length from baseline to design repair.

The bulb area is the area projected on the horizontal plane of the bulb below the waist, within the stern bulb length, plus the porthole.

The stern bulb factor for the rear hull is as follows:

Currently defined as

The linearity of the rear hull according to the invention has a stern bulb factor of at least 0,4 but may be significantly higher in certain cases. This depends, among other things, on whether there is a propulsion device in the rear hull, and how it is aligned if there is a propulsion device.

The linear according to the invention of the rear hull provides advantages corresponding to those described above for the bow:

넓고 편평한 벌브는 공기 공동의 매우 넓은 종결부를 가능하게 한다. 상기 벌브가 넓어질수록 상기 공기 공동의 더 넓은 종결부가 획득된다. 이것은 공기 공동의 에어리어를 증가, 즉 습 표면을 감소시켜서 결과적으로 마찰 저항을 감소시킨다.

The wide and flat bulb allows for a very wide end of the air cavity. The wider the bulb, the wider the end of the air cavity is obtained. This increases the area of the air cavity, that is, reduces the wet surface and consequently reduces the frictional resistance.

후부 선체에서의 공기 공동의 넓은 종결부는 최대 폭 선체 중앙부로부터 종결부까지 스타트하는 공기 공동의 측면들이 상기 수중 선체의 중심선에 평행한 수직면에 대해 작은 각들을 형성함을 의미한다. 이것은 공기 공동의 측면들 위에서의 가로 방향으로 수류가 흐를 가능성을 감소, 즉, 와류가 증가할 위험성을 더 적게 한다.

The wide end of the air cavity in the rear hull means that the sides of the air cavity starting from the full width hull center to the end form small angles with respect to the vertical plane parallel to the centerline of the underwater hull. This reduces the likelihood of water flow in the transverse direction on the sides of the air cavity, ie less the risk of increased vortex flow.

큰 수평 벌브는 같이 진동하는 수괴(water mass)를 증가시켜 증가된 극성의 질량 관성 모멘트를 제공한다. 동시에, 선미에 의한 벌브는 자신의 모션에 대한 식의 감쇠 계수를 지수적으로 증가하도록 한다. 모든 양들은 정확한 방향으로 변경, 즉 피치 방향에서의 수직 모션들을 감소하도록 한다.

Large horizontal bulbs increase the water mass oscillating together, providing an increased moment of inertia of polarity. At the same time, the bulb by the stern allows for an exponential increase in the attenuation coefficient of the equation for its motion. All the quantities are allowed to change in the correct direction, i.e. reduce the vertical motions in the pitch direction.

The termination of the bulb should be carried out taking into account the propulsion device and the possible exhaust of air. The following are just examples of termination:

1-propeller ships may suitably terminate the bulb on the baseline at a distance in front of the propeller plane. This then gives the possibility that possible air emissions pass under or outside the propellers.

So-called twin-skeg type two-propeller ships may have corresponding terminations for one propeller ship for each propeller. Thereafter, the width and the termination of the bulb inside each propeller must be adapted so that the propeller obtains sufficient water flow.

An interesting application of the invention arises for two hull vessels, the so-called catamaran vessels, wherein the propulsion devices are arranged at the centerline of the vessel. The hull arrangement is then based on the fact that a local body is formed between the ship's centerline, i.e. catamaran hulls, under a strength deck that joins the two hulls. The local body is on either side of the bow or stern and extends down towards the design repair. In stack water, the lower edge of the body is at or directly above the design waterline. The propulsion device is applied to the bottom of each body at each of the bow and stern. The rear hull of two catamaran hulls can now be formed into large and wider bulbs without the considerations required to be provided to the propulsion device. The planar bottom and the air cavities can be terminated in a sufficiently optimal way.

In order not to make unnecessary contributions to the wet surface, the stern side of the bulb according to the above-described catamaran arrangement can end and end with a somewhat rounded tip near the posterior vertical line somewhat above the baseline. At the rear, the bottom of the bulb is straight or slightly bent in the horizontal direction in the transverse direction and bowed continuously to be a flat horizontal bottom, which increases in width as the bottom is closer to the baseline. When the bottom reaches the baseline, the width is significant and thus satisfactory termination of the air cavity.

For all applications, a certain amount of air can be taken out by water or passed out of the rear hull under the hull. In order to reduce the risk of further resistance as water passes the rear side of the air cavity, it is provided with a deflection plane extending downward from the ceiling of the air cavity towards the interface between air / water. Then, the smaller the angle of the deflection plane when water and possibly less air leaves the air cavity, the smaller the risk of increased vortex. The deflection plane must of course have the same width as the air cavity.

In order to be able to maintain the interface between the air / water along the entire air cavity almost close to the lower edge of the hull, it is essential to keep the bottom of the hull horizontal, i.e., the vessel should have no so-called trim even keel) However, due to hydraulic influence, the ship will change its trim as the speed changes. Therefore, a manual or automatic system must be installed and aims to maintain the vessel without trim by water ballest pumping at the fore and rear hulls.

The water pressure at the lower edge of the hull will vary longitudinally with the blue valley and crest point. Therefore, there is no set value of the air pressure provided in advance. Instead, an automatic control system has to be installed, where level meters control the fans, which feed the air cavities and thereby the pressure. Thereafter, the level meter or level meters representing the lowest level of the interface between water / air will be compared to the desired level of the interface and select the control signal to the fans.

The height of the cavity, ie the distance from the bottom of the hull to the ceiling of the air cavity, must be adjusted to the maximum digging and the internal arrangement of the vessel, which will be able to reduce the resistance of the vessel in an effective manner.

Longitudinal stability becomes much smaller than conventional vessels due to the presence of a large free liquid surface in the air cavity. It is sensitive to additional trim while the ship is loading or unloading during berth. The shift in weight in the longitudinal direction results in a much larger change in trim than a corresponding vessel without air cavities. To reduce this additional trim increase, the cavity will need to divide the bow and stern into multiple compartments when the vessel is at anchor. This may be caused by the fact that one or more transverse walls are lowered or lowered in the air cavity. Each compartment of the air cavity will then be provided with an air supply of the compartment itself. When the ship is below speed the transverse walls will be pulled up or raised.

Depending on the dimensions of the ship and the associated speed / length, different types of waves are generated along the hull. These waves will also extend into the air cavity as the case may be. At certain velocities, these crest points will occur below the stern deflection plane. These waves are static for the ship and can be used. If such crest points are to be used, the trailing confinement of the surface of the air cavity, as well as the adjacent bottom of the stern bulb of the air cavity, should contact or encounter the trough of the wave. Thus the lower part of the rear side of the air cavity is closed by the crest point and there is no hull portion of the same rear. Then the rear side of the deflection plane will meet the floor of this wave. This means that in order for the rear side of the deflection plane to be connected to the corresponding height of the wave, the deflection plane must be adapted or adapted to be switched or lowered / rised. In this way, air is included to the maximum that can be realized. Since this creates additional resistance, there is no hull portion below or the stern of the lower portion of the deflection plane. The higher the wave, the higher the end of the deflection plane. In this way, the resistance decreases and the ship gains increased power / speed bow. If drift during mooring is essential, the deflection plane must be able to be lowered / downward during mooring, so that its lower edge is coplanar with the lower edge of the hull. At this time, the air cavity can be utilized to the maximum, and the ship's drift is reduced.

As mentioned above, the present invention provides a new linear that provides a large planar lower area to fit the principle of the air cavity and to utilize the principle. This reduces the motion at sea and consequently reduces the demand for power and bunker consumption, making the ship suitable for oceangoing operations.

Embodiments of the hull arrangement and the linear according to the invention are described next, with reference to the accompanying drawings,
1 shows a profile of a blank having an embedded definition of bulb length;
FIG. 2 shows an example of a body plan of a bow portion having an air cavity; FIG.
3 shows an example of a body plan of a rear hull with an air cavity;
4 shows an example of a body plan of the rear hull of a catamaran; And
5 shows the profile of the rear hull with waves at the end of the air cavity.

1 shows a profile of a blank having an embedded definition. Baseline BL is a line parallel to the design water line (dWL) through the lowest point of the vessel. The waste waist W is the trailing point of the finish at a point above the finish edge of the bulb. In the figure, the length of the bulb is also defined. This definition applies on the assumption that all transverse frames have a waste within the bulb length. If this is not the case, the length decreases from the edge of the bow of the bulb to the horizontal frame, which is the last frame of the bow with a waste.

2 shows an example of a body plan of the bow portion of the bow section up to dWL. The frames shown correspond to positions of 85, 90, 95, 100 and 101, 25% of the vertical length. 50% corresponds to the center of the hull and 100% corresponds to the frame of the bow vertical line FP. 101,25% of the vertical lengths in this example correspond to the frame in the middle between the bow vertical line FP and the bow edge of the bulb. In the figure, it is shown how the bottom 1 of the bulb continuously deforms to the horizontal bottom 2 when the bottom 1 of the bulb approaches the baseline BL 3. In the example shown, the bottom of the bulb reaches the bottom of the plane just before the frame position 90%, where the bottom of the plane has been replaced by the starting of the air cavity, which is shown by dashed line 5. At 85% of the frame, the width of the air cavity has further increased and is shown by dashed line 6. In frame 101,25%, the ellipse 4 is shown as a comparison. Although a trough is provided here where the upper edge of the ellipse meets the connection with the bow, the large horizontal expansion of the bulb and the similarity with the horizontally lying ellipse can be clearly seen.

3 shows an example of a body plan of a 1-propeller rear hull according to the invention. The frames shown correspond to 0, 5, 10, 15 and 20% positions of the vertical length. 0% of the ship's length corresponds to the stern vertical line AP. In this case it is clearly confirmed how the bottom of the bulb coincides with the plane through the baseline BL and how it entails a significant increase in the width of the air cavity. The air cavity has a full height 7 at 20% of the frame. The height of the air cavity is continuously reduced by the stern by the deflection plane and exactly reaches the baseline BL later of 15% of the frame. This means that the end of the air cavity in this example has a width 8 of about 55% of the maximum width of the center of the air cavity hull. The lower part of the frame 2,5% is shown therein to indicate the end of the bulb, which ends just before the propeller plane P. This means that most of the air floating in the water flowing below the air cavity will pass under and outside the current propeller area.

4 shows an example of a body plan according to the invention of the rear hull for catamarans, wherein the rear hull of each frame is free of propulsion devices. Thus, the rear hull is here only formed taking into account the maximum utilization and resistance of the air cavity principle. The frames shown correspond to 0, 5, 10, 15 and 20% positions of the vertical length. In this example, the bulb with rounded tip 8 terminates at a suitable height in terms of resistance point just after the stern of the AP. Here, the bottom surface 9 of the bulb is shown in straight lines in the transverse direction. The width of the athlete increases rapidly and approaches the baseline at exactly 10% of the frame. Here, the terminating portion 10 of the air chamber may be arranged. In this example, the width of the end of the air cavity is almost 80% of the maximum width of the air cavity. In this example, the deflection plane extends from frame 10% to frame 15%, where the maximum height of the air chamber is possible (11).

Fig. 5 shows the profile of the rear hull with the body plan according to Fig. 4. Here it was chosen to take advantage of the pressure from standing waves generated by the ship at a position around frame 10%. The pressure is greater than the pressure in the air chamber so that the air chamber can be terminated to a higher level. This is indicated by the dotted line 12. The deflection plane is shown by line 13, where there is no hull below the end of the deflection plane and behind the straight horizontal line. Schematically, the wave 14 is shown to fill the area from the end of the deflection plane to the baseline. The pressure in the air chamber then provides additional propulsion in front of the vessel.

3: BL: Baseline dWL: Design Repair
2: bottom

Claims (8)

In the hull form and arrangement of ships,

The forebody has a wide and horizontal bulb, which separates the water flowr into a lower flow and an upper flow passing below the vessel, the upper flow mainly moving along the sides of the vessel. and;

The bulb coefficient defined by the following formula has a minimum value of 1,5

The bulb length calculated from the foremost point of the underwater hull is given by the following two values:
A horizontal distance from the foremost point of the underwater hull to the position of the transverse frame, in which the wasit of the transverse frame of the bow is not visible, or
The smallest of two times the horizontal distance calculated from the foremost point of the underwater hull to the foremost point of the stem profile at the waist,
The bulb volume here is the hull volume plus port to the starboard, within the bulb length from baseline to design repair,
The bulb area is the area projected on the horizontal plane of the bulb, plus the porthole, of the bulb below the waist within the bulb length,

The underside of the bulb in the front part of the bulb length is straight or slightly curved outwardly from the centerline and outward in the transverse direction, after which it is continuously deformed in the transverse direction so that the whole is horizontal in the aft direction, and the underside is said When arriving at the baseline or just after the same location, a larger portion of the horizontal plane lower area is replaced by a cavity, the cavity opening downwards and either on the surface of the top of the cavity or on one of the sides of the cavity. Or linear and arrangement of a vessel filled with air having a pressure corresponding to the pressure of the surrounding water by inlet pipes disposed in part. The method of claim 1,
Wherein said bulb coefficient has a minimum of 2,0. The method of claim 1,
Wherein said bulb coefficient has a minimum of 2,5. The method according to any one of claims 1 to 3,

The transverse frame at the lower rear of the rear body within at least one stern bulb length defined as follows has a waist,

The same part has a wide horizontal bulb which increases the horizontal part of the lower face,

The stern bulb coefficient, defined as follows, has the lowest value of 0,4,

Where the stern bulb length is defined as 10% of the vertical length of the hull calculated from the aft point of the bulb below the waist in the bow direction, and the bulb volume is the stern bulb from the baseline to the design repair. It is the hull volume that added port side to starboard in the length,
The bulb area is an area projected on a horizontal plane in which the port of the stern bulb under the waist in the stern bulb length is added to the port,

The stern bulb at the rear edge of the hull is terminated to have a rounded tip when viewed from the side, on the baseline or above the baseline, and within the rear of the bulb length in the transverse direction. When the underside of the stern bulb is straight outwardly or slightly bent from the centerline and continuously deformed in the bow direction so that the whole is horizontal in the transverse direction, when the underside reaches the baseline or just ahead of this position And a flat horizontal lower area is replaced by said air cavity. The method according to any one of claims 1 to 4,
And the lower edge of the rear end of the air cavity is above the baseline and from below this level down to the baseline, the air cavity approaching a stationary wave generated by the vessel. The method of claim 5, wherein
And the lower edge of the rear end of the air cavity can be raised or lowered respectively to meet different heights of the standing wave at different speeds. The method according to claim 5 or 6,
And the lower edge of the rear end of the air cavity lowers to the bottom of the air cavity when the vessel is at anchor or at low speed. The method according to any one of claims 1 to 7,
When the vessel is berthing, one or more transverse partition walls are temporarily lowered to divide the bow and stern of the air cavity into a plurality of air chambers, and the vessel utilizes power to speed up and reduce the principle of the air cavity. When said partition walls rise.

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