JP2009292202A - Method for reducing frictional resistance force between ship body and water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for reducing a frictional resistance force between a ship body and water by discharging gas into the water. <P>SOLUTION: This method includes: a step a of arranging an exhaust port 40 used for discharging the gas at and below a water line WL positioned in the forward edge of the hull 30 of the ship body 20; a step b of discharging the gas from the exhaust port 40, making the gas adhered to the hull 30 and go up along an inclined wall, partially separating the contact between the hull 30 and the water, and lowering the average density of the water contacted with the hull 30; a step c of selecting a position for discharging the gas, making the discharged gas adhered to the surface of the hull 30 and floated on the surface of the water from a prescribed position along a prescribed line of flow; and a step d of making the discharged gas contact with a cushioning layer of a high pressure section and a low pressure section, lowering the pressure of the water to the hull 30 in the high pressure section, and reducing the sucking force of the water to the hull 30 in the low pressure section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for reducing the frictional resistance between the hull and water, and more particularly to a method for reducing the frictional resistance between the hull and water by discharging gas into the water.

  Typical hulls include powered ships, warships, aircraft carriers, mail ships, cargo ships, tankers, pleasure boats, water bikes, model ships, seaplanes and non-powered oil boring and barges.

  Each hull is different in functionality, so the shape design is different. In the case of warships, high speed is required, so the modeling is designed in a slender streamline, while the load and draft are small. In the case of a merchant ship, since a large loading capacity and a large draft amount are required, the modeling is designed to be wide and the speed is slow. This is because the resistance of water (including seawater and fresh water, hereinafter collectively referred to as “water”) becomes the main factor that hinders the navigation of ships.

FIG. 1 is a perspective view of a ship 900. 2 and 3 are a side view and a plan view, respectively. Such commercial ships have a length L ′ of several hundred meters (m) and a width B ′ of about 60 to 70 meters (m). The draft D 'is related to whether or not the baggage is fully loaded, and is generally 15 to 25 m. Such large commercial ships have a very large contact area with water. The formula of the frictional resistance force based on the fluid mechanics principle is as follows.
F _D = C _D A1 / 2ρU ²
C _D (drag coefficient): Resistance coefficient A: Total contact area with fluid ρ: Fluid density U: Navigation speed (m / s)

The hull 930 of the ship 900 is regarded as a flat plate in contact with seawater, and its length L ′ is 360 m, width B ′ is 70 m, draft depth D ′ is 25 m, and seawater at 10 ° C. at a speed of 13 knots. When sailing, the surface frictional resistance of the hull 930 can be calculated by the formula F _D = C _D A1 / 2ρU ² . Also, according to Non-Patent Document 1 Purdue University (Badeyu University) Robert W.FOX Prof. authored, L'described above, B', and calculates the F _D numerical by data such D'and U.

If the navigation speed is 13 knots
Navigation speed U = 13 nm / hr × 6076 ft / nm × 0.305 m / ft × hr / 3600 s = 6.69 m / s.
When navigating at 10 ° C seawater,
Kinematic viscosity ν = 1.37 × 10 ⁻⁶ m ² / s.

In addition, when C _D and ρ are calculated from the data and mathematical formulas described in the appendix of the literature,
C _D = 0.00147 ρ = 1020 kg / m ³
Moreover, when the total contact area A with seawater is calculated by the length L ′ of the hull 930 that contacts seawater and the width (W ′ = B ′ + 2D ′) of the hull 930 that contacts seawater,
A = (360 m) × (70 + 50) m = 43200 m ²

The numerical values calculated by the above formula are as follows.
F _D = C _D A1 / 2ρU ^{2
= 0.00147 × 43200m 2 × 1/} 2 × 1020kg / m 3 × (6.69) 2 m 2 / s 2 × N · s 2 / kg · m
F _D = 1.45MN

The corresponding power is as follows.
P = F _D U = 1.45 × 10 ⁶ N × 6.69 m / s × W · s / N · m
P = 9.70 MW (about 13,000 horsepower)
This data proved that the vessel 900 requires very large power to overcome the surface frictional resistance.

  From the above example, the following has been found. When traveling on land, the resistance force is generated by the friction force between the air and the tire and the road surface. When traveling on water, the resistance force is generated by the resistance force of the air and the friction resistance force between the hull and the water. . When the power is the same, the speed of traveling on land is faster than the speed of traveling on water. When the temperature is 20 degrees Celsius and the atmospheric pressure is one atmospheric pressure, the density of water is 1, which is about 800 times that of air.

Therefore, many researchers are actively studying a method for reducing the frictional resistance force F _D between the hull and water. Conventional methods reduce the frictional resistance between the hull and water by mounting a nose cone and hydrofoil. The nose cone can reduce resistance due to bow ripples and wave reflections. Hydrofoil ships can support the hull with the hydrofoil and reduce the contact area between the hull and water, but can only be applied to small ships. In the case of hovercraft, since a very large gas is required to support the hull, it can be applied only to small ships. This is because the density ρ of water cannot be reduced, and the frictional resistance force between the water and the hull, the pressure in the high pressure section and the suction force in the low pressure section are still unsolved.

  As shown in FIG. 3, the hull 930 has a thinner boundary layer (Boundary Layer) between the front end a ′ to b ′ of the bow 931, the body from the front end a ′ to b ′, and the water to the stern c ′ point. Therefore, when a frictional force is generated in the boundary layer, a resistance force is generated, and the object generates a wake 932 shown by a broken line before the point c ′ in FIG. Among them, the c ′ point is a separation point, and a trajectory is generated in the fluid particles away from the object, and a wake 933 can be generated inside the c ′ point. That is, the streamline from the point a ′ to the point b ′ is a high pressure section, the small section after the point b ′ generates a turbulent flow or a low pressure section, and the tail stream 933 after the point c ′ generates a low pressure section. The water flow in the high pressure section generates pressure on the hull 930, and the water flow in the low pressure section generates suction force on the hull 930. Either “pressure” or “suction force” causes a resistance force to prevent the hull from moving forward, and the hull efficiency cannot be improved unless it is overcome.

Another conventional technique for reducing frictional resistance is to design the hull form by computer and water engineering tests, effectively interfering with water waves, but it is not effective unless the speed is within a limited range. This is because the hull form cannot effectively interfere with water waves by varying its shape with different speeds. Therefore, the effect is limited.
As mentioned above, conventional shipbuilding techniques have the problem of having to overcome water resistance.

Purdue University Robert W.FOX and others. “INTRODUCTION TO FLUID MECHANICS (Sixth Edition)”

The main object of the present invention is to provide a method of reducing the frictional resistance between the hull and water by discharging gas into the water.
Another object of the present invention is to expand the gas volume while gradually reducing the water pressure based on the principle that the volume of compressible gas is inversely proportional to the pressure when the gas is exhausted from the ship bottom and rises. is there.

Another object of the present invention is that the gas is exhausted from the bottom of the ship, and when rising, the hull has a large curve, and the exhausted gas has a resistance to the resistance by the phenomenon that the process of rising from the bottom of the ship to the water surface becomes longer. It is to improve the efficiency of descending.
Yet another object of the present invention is to allow the gas to be wiped and cleaned with the raised gas when it is exhausted from the bottom or bow and attached to the hull and rises along the inclined wall of the hull. The function to reduce the adherence and breeding of marine organisms and extend the maintenance deadline.

(effect)
The present invention generates effective interference by discharging gas to a predetermined position below the water line at the front edge of the hull based on parameters such as the overall length of the hull, navigation speed and draft depth. This reduces the average density ρ of the water surface in contact with the hull, reduces the water pressure on the hull in the high-pressure section by the discharged gas, and reduces the water suction force on the hull in the low-pressure section. It is a method that makes it possible to achieve a heavy effect.

  The principle of the present invention is that gas is discharged from the bottom of the ship by the property of rising vertically when the gas is discharged from the bottom of the water, and the gas is attached to the hull to rise along the inclined wall of the hull. Partially isolates the hull-water contact, lowers the average density of water in contact with the hull, and rises vertically when the gas is discharged from the bottom and the gas compressible The gas is discharged in the high-pressure section and the low-pressure section of the water to the hull, a buffer layer is formed, and the pressure of the water on the hull is lowered in the high-pressure section by the discharged gas, and the water on the hull is reduced in the low-pressure section. It is to reduce the suction force. As a result, it is possible to achieve a method of reducing double resistance forces such as the pressure and the suction force during navigation.

In addition, the present invention does not require a change in the shape of the hull, the exhaust port used for gas discharge is arranged at a predetermined position on the bow, and the discharge position is selected in accordance with parameters such as navigation speed and depth of draft In this way, the discharged gas adheres to the surface of the hull and rises from the predetermined position along the predetermined flow line to the surface of the water, so the efficiency of reducing the surface resistance of the hull is the best. Can be achieved.
Furthermore, the present invention (when air bubbles are discharged from 30m depth and expands four times when they rise to the surface of the water), when discharging gas to large ships with deep drafts, the discharged gas has a multiple of friction resistance. It is possible to obtain the effect of lowering.

To achieve the above object, the method for reducing the frictional resistance between the hull and water according to the present invention includes the following steps.
In step a, the draft line located at the front edge of the hull of the hull and an exhaust port used for gas discharge are arranged at a certain lower position near the waterline.
Step b discharges the gas from the bottom of the water based on the natural phenomenon that the gas rises vertically when the gas is discharged from the bottom, and attaches the gas to the hull and raises it along the inclined wall. Partially isolates contact with water and lowers the average density of water in contact with the hull.

Step c attaches the exhausted gas to the surface of the hull by selecting the gas discharge position according to parameters such as the shape of the hull, navigation speed, draft depth and water temperature. Along the surface of the water.
Step d applies the gas discharged by the compressibility of the gas to the buffer layer in the high-pressure section and the low-pressure section, reduces the water pressure on the hull in the high-pressure section, and reduces the water suction force on the hull in the low-pressure section. Decrease.
As a result, double resistance forces such as pressure and suction force generated during navigation are simultaneously lowered. And the exhausted gas has the characteristics described in step b. Therefore, it is possible to increase the navigation speed with the same power, reduce the fuel cost by a large amount, and achieve the reduction of carbon dioxide.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(One embodiment)
The method for reducing the frictional resistance between the hull and water according to an embodiment of the present invention includes, as step a, a water line (Water Level, WL) located at the front edge of the hull hull 30 as shown in FIG. ) And an exhaust port 40 used for gas discharge is disposed below in the vicinity thereof. In this embodiment, the hull is the ship 20, but is not limited to this, and is a hull or a loadable object of any shape such as military, commercial, leisure or sports. The length of the hull 30 is indicated by L, the width is indicated by B, the depth of the draft is indicated by D, and the navigation speed is indicated by U.
In the present embodiment, as shown in FIGS. 5A and 5B, exhaust ports 40 used for gas discharge are disposed on both side surfaces of the central ridgeline 301 that are adjacent to and correspond to each other on the center ridgeline 301 that extends backward from the bow 31 of the hull 30.

FIG. 8 shows a cross-sectional view of the present embodiment in which the exhaust ports 40 are arranged on both sides near the central ridge line of the hull 30. Hereinafter, the exhaust port 40 will be described based on this embodiment.
In the present embodiment, the exhaust port 40 is constituted by a tubular body fixed to the surface of the hull 30. The tube has a number of pores, which exhibit a circular or elongated shape. The advantage of the exhaust port 40 composed of a tube provided outside the hull 30 is that it is not necessary to change the hull 30 and the exhaust port 40 can be mounted after shipment. In addition, many exhaust ports 40 can be arranged on the surface of the hull 30 before shipment.

Next, as step b, the gas is discharged below the draft line WL of the hull 30 using the exhaust port 40.
FIG. 6 shows a state when the exhaust port 40 in the present embodiment is used. The gas pressurization supply chamber 50 installed inside the hull 30 sends the exhaust gas generated in the air or the engine chamber by the pipe line 51 to the exhaust port 40. In the present embodiment, the exhaust port 40 is formed in many sections, and one of the exhaust ports 40 in the many sections is selected by the pipe line 51 of the gas pressurizing supply chamber 50 to discharge the gas.

  As shown in FIG. 7, the power supply chamber 60 installed inside the hull 30 outputs power by a wire 61 to the heating device 41 around the exhaust port 40 to change the water into a gas and discharge it. The gas formed by the vaporization of water generates bubbles, adheres to the surface of the hull 30 and rises along the streamline. In the present embodiment, the exhaust port 40 is formed in many sections, and the power supply chamber 60 controls opening / closing (ON / OFF) of many sections.

Next, as step c, the exhaust port 40 is selected according to demand and the gas is discharged.
As shown in FIG. 8, when the hull 30 moves forward, as described above, the bow 31 is a high pressure section from the point a to the point b in contact with water. In order to generate a low-pressure section, when the hull 30 travels at a certain speed, a very large surface friction resistance is generated at point b. At this time, this embodiment selects the exhaust port 40 close to the position of the waterline WL and discharges a large amount of gas 70.
Next, as step d, the discharged gas is applied to the buffer layer in the high pressure section and the low pressure section. Since the exhausted gas 70 floats on the water line WL and is located at the point b, not only the pressure of the water generated in the high pressure section but also the suction force of the water generated in the low pressure section is reduced, and at the same time, the two types of resistance force are eliminated. can do.

In this embodiment, the state of the exhaust port 40 used for the gas discharge described above is shown in FIGS.
When the hull 30 is stationary and the navigation speed U is 0, the gas 70 discharged from the exhaust port 40 adheres to the surface of the hull 30 as shown in FIG. To rise.

  FIG. 10 shows a state where the length of the hull 30 is 300 m, the draft is 15 m, and the navigation speed is 5 knots. Since the speed of the gas rising from the water is 18 m / min (when the gas is discharged from a depth of 15 m, the gas travels along the arc line of the hull is 18 m). When the gas is discharged, the raised gas 70 floats on the water surface around w, which is 150 m away from the bow on the streamline shown in FIG.

  FIG. 11 shows a state where the length of the hull 30 is 300 m, the draft is 15 m, and the navigation speed is 10 knots (300 m / min). Since the speed of the gas rising from the water is 18 m / min (when the gas is discharged from a depth of 15 m, the gas travels along the arc line of the hull is 18 m), and therefore, 15 m from the draft line WL below the bow. When the gas is discharged from below, the gas 70 rises to the water surface around the stern c.

  FIG. 12 shows a state when the length of the hull 30 is 300 m, the draft is 10 m, and the navigation speed is 15 knots (460 m / min). Since the present embodiment has a navigation speed of 15 knots and is faster than the above-described embodiment, if the gas is discharged from about 10 m below the draft line below the bow, the gas 70 will rise to the water surface around the stern c.

  In the above four states, when discharging the gas, in order to discharge the appropriate amount of gas to the optimal gas discharge position, attach and raise the gas streamline on the surface of the outer shell, and to optimize the working area, He explained that not only parameters such as the length of the hull L, the draft depth D, and the navigation speed U, but also the water temperature at that time must be taken into account. That is, by reducing the water pressure on the hull 30 in the high pressure section and lowering the water suction force on the hull 30 in the low pressure section, the two kinds of resistance forces such as the navigation pressure and the suction force are simultaneously decreased. , Can improve the efficiency.

(Other embodiments)
Further, as shown in FIGS. 13A and 13B, the exhaust port 45 can be disposed on the center bottom surface of the protruding edge 302 extending backward from the bow 36 of the hull 35. Thereby, the exhaust port 45 can be positioned in the middle, and the gas 70 can be discharged from both sides.

  In addition, in the case of a special hull 37, for example, a flat bottom ship shown in FIGS. An exhaust port 47 can be arranged. Thereby, the gas 70 is discharged | emitted later, a buffer layer is produced | generated in the contact surface of the whole flat bottom face 302 and water, and resistance can be dropped.

The method for reducing the frictional resistance between the hull and the water according to the invention requires that the arrangement of the outlets can be selected by the shape of the hull and that the position is only below the waterline.
As described above, the present invention exhausts gas from the bottom of the ship through the exhaust port described above, and lowers the frictional resistance between the hull and water, so it is possible to increase the navigation speed when sailing with the same horsepower. is there. In other words, the present invention achieves the same predetermined speed without requiring a relatively large horsepower or propulsive force, thus reducing the fuel cost and the amount of carbon dioxide emissions by a large amount, economic efficiency and environmental protection in an era of energy shortage, etc. Can be fulfilled actively.

The perspective view of the conventional ship. The side view of the conventional ship. The top view of the conventional ship. The side view of the hull in one embodiment of the present invention. The schematic diagram explaining one Embodiment of this invention. The schematic diagram explaining one Embodiment of this invention. The schematic diagram explaining one Embodiment of this invention. The schematic diagram explaining one Embodiment of this invention. The schematic diagram which shows the state which discharges | emits gas in one Embodiment of this invention. Explanatory drawing which shows a state when a hull is stationary in one Embodiment of this invention. In one Embodiment of this invention, explanatory drawing which shows a state when the navigation speed of a hull is 5 knots. In one Embodiment of this invention, explanatory drawing which shows a state when the navigation speed of a hull is 10 knots. In one Embodiment of this invention, explanatory drawing which shows a state when the navigation speed of a hull is 15 knots. The schematic diagram which shows the state by which the exhaust port was arrange | positioned in the center of the protrusion edge part of a hull in other embodiment of this invention. The schematic diagram which shows the state by which the exhaust port was arrange | positioned in the center of the protrusion edge part of a hull in other embodiment of this invention. The schematic diagram which shows the state by which the exhaust port was arrange | positioned in the flat bottom ship in other embodiment of this invention. The schematic diagram which shows the state by which the exhaust port was arrange | positioned in the flat bottom ship in other embodiment of this invention.

Explanation of symbols

  20: ship, 30: hull, 31: bow, 301: center ridgeline, 302: protruding edge, 303: flat bottom surface, 40: exhaust port, 41: heating device, 50: gas pressurization supply chamber, 51: pipeline , 60: power supply room, 61: electric wire, 70: gas

Claims (6)

A step a in which a water line located at the front edge of the hull of the hull and an exhaust port used for gas discharge are disposed below the water line;
Exhaust the gas from the exhaust port, attach the gas to the hull and raise it along the inclined wall, partially isolate the contact between the hull and the water, and lower the average density of water in contact with the hull Step b;
Selecting a position for discharging the gas, attaching the discharged gas to the surface of the hull, and floating on the surface of the water from a predetermined position along a predetermined streamline; and
Applying the discharged gas to a buffer layer in a high-pressure section and a low-pressure section, reducing the water pressure on the hull in the high-pressure section, and reducing the water suction force on the hull in the low-pressure section;
A method for reducing frictional resistance between a hull and water characterized by comprising:   The method of reducing frictional resistance between a hull and water according to claim 1, wherein the gas is any one of air, engine exhaust gas, or vaporized gas.   The frictional resistance between the hull and water according to claim 2, wherein the gas and the exhaust gas of the engine are transported to an exhaust port by a pipeline from a pressurized gas supply chamber mounted inside the hull. How to reduce.   4. The method of reducing frictional resistance between a hull and water according to claim 3, wherein the exhaust port is formed of a number of sections, and the opening and closing of each section is controlled by a gas pressurizing supply chamber. .   Vaporized gas includes gas formed by the power supply chamber installed inside the hull outputting power to the heating device around the exhaust port by means of electric wires and vaporizing water, and opening and closing each section 3. The method of reducing frictional resistance between a hull and water according to claim 2, wherein the power is controlled by a power supply chamber.   The method according to claim 1, wherein the hull is any one of military, commercial, leisure, and sports.

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