JP5562206B2 - Ship bow structure - Google Patents

Description

  The present invention relates to a bow structure of a ship, and more particularly to a bow structure that suppresses pitching motion of a hull during sailing in waves.

  As the ship's bow structure, set the front upper deck set above the full flooding line, project forward from the upper upper deck, slightly higher than the navigational dredging line position, and set below the front upper deck The thing of the two-stage front part deck structure which has the made front lower deck is known (for example, patent document 1).

  In this two-stage front deck structure ship, when the ship encounters a heading wave during navigation, the bow part enters the wave, and the buoyancy of the volume above the inundation line during navigation is newly added to the bow part. The bow tends to rise due to an increase in buoyancy, but the front lower deck is immersed in the waves, so that the increase in buoyancy at the bow is suppressed compared to when the front deck is not immersed in the waves. Moreover, when the front lower deck is immersed in the wave, the wave pressure (water pressure) acts downward on the flat upper surface of the front lower deck, and the movement of the bow to rise is suppressed. By these things, the lift of the bow at the time of wave navigation is suppressed, and the pitching motion of the hull can be suppressed.

JP-A-3-224889

  In a ship with a two-stage front deck structure, there may be a flow of seawater (water) across the front lower deck from one side of the hull to the other side, and this flow induces a rolling motion of the hull. Even if the pitching performance is improved, the rolling performance may be deteriorated. Further, since the front lower deck portion is submerged, it is difficult to effectively use the front lower deck portion, and the deck area that becomes a dead space is large. Further, since the rear shape of the front lower deck is inappropriate, splash occurs in the rear portion, resulting in an increase in hull resistance (navigation resistance).

  The problem to be solved by the present invention is that the rolling performance of the hull does not deteriorate, the resistance of the hull does not increase, the deck area that becomes a dead space is not created, and the pitching motion of the hull during sailing in waves is suppressed. That is.

  The bow structure of a ship according to the present invention has recesses recessed from the outer surface of the hull on both the left and right sides of the bow part, the recesses being an upward surface located above the floodline and a downward facing the upward surface from above. A surface and a lateral surface extending between the upward surface and the downward surface.

  According to this configuration, when the upward surface of the concave portion exposed on the sea surface (water surface) is submerged in the sea (underwater) due to navigating in the waves, seawater (water) flows into the concave portion, and the seawater that flows into the concave portion Causes a vortex by colliding with the lateral surface of the recess. This vortex generation consumes the kinetic energy of the bow up and down movement, and the bow up and down is reduced. The concave portion also serves to reduce an increase in the buoyancy of the bow due to the bow entering the wave, and the lift of the bow due to the increase in buoyancy is suppressed. As a result, the pitching motion of the hull during sailing in the waves is suppressed.

  The recesses exist independently on the left and right sides of the bow, and the left and right recesses do not communicate with each other, so there is no flow of seawater from one side of the hull to the other side, and the hull rolling performance is reduced. There is no deterioration. Further, since the recess is a recess having a downward surface on the upper side, the deck does not form a deck area that becomes a dead space.

  In the bow structure of a ship according to the present invention, preferably, the lateral surface is constituted by a surface that continues smoothly over the entire bow stern direction, and is smoothly connected to the outer surface of the hull on the stern side.

  According to this configuration, the laterally facing surface is configured by a surface that is smoothly continuous over the entire bow and stern direction, and is smoothly connected to the outer surface of the hull on the stern side, thereby flowing in the recess. The streamline of seawater at the bow and stern direction becomes smoother than the streamline in the ideal hull form. Thereby, the concave portion for reducing the pitching motion does not cause the generation of the spray wave and the splash, and does not increase the hull resistance (navigation resistance).

  In the bow structure of a ship according to the present invention, preferably, the upward surface and the lateral surface are smoothly connected by an arc surface.

  According to this configuration, the seawater that has flowed into the concave portion flows along the circular arc surface, so that vortices are generated in the concave portion, and the energy consumption of the bow vertical motion increases accordingly.

  In the bow structure of a ship according to the present invention, preferably, the downward surface and the lateral surface are smoothly connected by an arc surface, and more preferably, the curvature of the arc surface connecting the downward surface and the lateral surface. Is larger than the curvature of the arc surface connecting the upward surface and the lateral surface.

  According to this configuration, the seawater that collides with the lateral surface of the recess by a large wave and jumps up and reaches the downward surface is guided by the arc surface and discharged out of the recess with a smooth streamline. Seawater does not collide violently. As a result, no tapping sound or vibration is generated due to the violent collision of seawater with the downward surface of the recess. In particular, since the curvature of the arc surface connecting the downward surface and the lateral surface is larger than the curvature of the arc surface connecting the upward surface and the lateral surface, the effect becomes remarkable.

  In the bow structure of a ship according to the present invention, preferably, the upward surface includes a flat surface extending horizontally in the bow / stern direction.

  The upward surface of the recess includes a flat surface that extends horizontally in the bow stern direction, so that the pressure of the wave that entered the recess (water pressure) acts downward, and this also causes the bow to move up. Is suppressed.

  The bow structure of a ship according to the present invention is preferably a multi-hull ship having a main hull and a demi-hull, and the recess is provided in at least one of the main hull and the demi-hull.

  The recess for reducing the pitching motion is also effective for a double hull having a main hull and a demi-hull in addition to a single hull. In the case of a double hull, the recess may be provided in at least one of the main hull and the demi hull. .

  According to the bow structure of the ship according to the present invention, when the upward surface of the concave portion is submerged in the sea (underwater) due to sailing in the waves, seawater (water) flows into the concave portion, and the seawater that has flowed into the concave portion is directed to the lateral surface of the concave portion. The vortex is generated by the collision, and the kinetic energy of the bow motion is consumed by the generation of the vortex. As a result, a damping effect is obtained, and the vertical swing of the bow is reduced. The concave portion also serves to reduce the increase in buoyancy due to the bow entering the wave, and the bow lift due to the increase in buoyancy is suppressed. As a result, the pitching motion of the hull during sailing in the waves is suppressed, the ride comfort in the waves is improved, and sea sickness is less likely to occur.

  The recesses exist independently on the left and right sides of the bow, and the left and right recesses do not communicate with each other, so there is no flow of seawater (water) crossing from one side of the hull to the other side of the hull. Rolling performance is not deteriorated. In particular, the rolling performance of the hull is improved by providing a recess in the demi-hull. Further, since the recess is a recess having a downward surface on the upper side, the deck does not form a deck area that becomes a dead space.

The side view which shows one Example of the ship which took in the bow structure by this invention. The perspective view of the ship which adopted the bow structure by a present Example. The front view of the ship which adopted the bow structure by a present Example. FIG. 4 is a plan sectional view taken along line IV-IV in FIG. 1. FIG. 5 is a longitudinal sectional view taken along line VV in FIG. 1. The perspective view which shows the other Example of the ship which took in the bow structure by this invention. Another embodiment of the bow structure. The graph which shows the encounter frequency-bow acceleration characteristic of the ship which took in the bow structure by this invention, and the conventional type ship. The figure which shows the dimension specification of the trimaran ship used for the bow acceleration characteristic test.

  Below, one Example of the bow structure of the ship by this invention is described with reference to FIGS.

  The ship according to this embodiment is a trimaran ship (trimaran ship) having a main hull (center hull) 10 and demi-hulls (side hulls) 12 on both left and right sides of the main hull 10.

  The foremost tip 11 that connects the left and right hull outer surfaces 10L, 10R to each other at the bow of the main hull (hull) 10 has a straight shape in which the bottom 14 side is inclined in the stern direction from the deck 16 side.

  On the left and right sides of the bow portion of the main hull 10, recessed portions 20 recessed from the hull outer side surfaces 10L and 10R are respectively formed on the left and right sides of the hull outer plate. The recess 20 is formed between a substantially horizontal upward surface 22 positioned slightly above the drowning water line W, a substantially horizontal downward surface 24 facing the upward surface 22 from above, and the upward surface 22 and the downward surface 24. It is demarcated by three walls formed by a laterally extending surface 26 that extends substantially vertically, and has a horizontally long shape that extends in the stern direction from the vicinity of the bow leading edge 11.

  In other words, the upward surface 22 and the downward surface 24 of the recess 20 extend substantially horizontally in the bow stern direction (the hull longitudinal direction), and are flat surfaces 22A and 24A extending horizontally in the same direction (see FIG. 5).

  The distance D in the vertical direction between the drowning line W and the upward surface 22 during navigation is that the waves are gentle and the entire upward hull 22 is exposed to the sea (water) during steady navigation when the main hull 10 does not perform a large pitching motion. When the bow of the main hull 10 is subjected to waves during wave navigation, at least part of the upward surface 22 is a distance (height) that sinks into the sea (underwater), and this distance D is the distance of the main hull 10 itself. What is necessary is just to set to an appropriate value according to pitching performance or the concept of a ship.

  As shown in FIG. 4, the laterally facing surface 26 of the concave portion 20 is smoothly connected to the bow leading end portion 11 without including a bending member or a step on the bow side, and extends over the section A when viewed in the bow stern direction. A flat surface 26A that extends in a straight line and a concave surface with a radius Rb that smoothly continues without including a bending member or a step on the stern side of the flat surface 26A on the bow side. The front arc surface 26B extending over the stern side of the front arc surface 26B on the bow side smoothly without any bending member or step, and connected to the hull outer surface 10L (10R) on the stern side. A convex surface with a radius Rc, and a rear arc surface 26C extending over the section C when viewed in the bow / stern direction, is constituted by a streamlined surface that is smoothly continuous over the entire surface.

  The upward surface 22 and the lateral surface 26 of the recess 20 are smoothly connected by an arc surface (R surface) 28 (see FIG. 5). Further, the downward surface 24 and the lateral surface 26 of the recess 20 are also smoothly connected by an arc surface (R surface) 30 (see FIG. 5). The curvature of the arcuate surface 30 that connects the downward surface 24 and the lateral surface 26 is set to a value larger than the curvature of the arcuate surface 28 that connects the upward surface 22 and the lateral surface 26.

  According to the above-described configuration, during steady sailing in which the waves are gentle and the main hull 10 does not perform a large pitching motion, as shown in FIG. Is exposed to the sea (water).

  As shown in FIG. 5 (B), when the ship's bow enters the peak of the wave and the upward surfaces 22 of the left and right recesses 20 exposed on the sea surface are submerged in the sea during the wave navigation. The seawater flows into the recess 20. Seawater that flows into the recess 20 collides with the laterally facing surface 26 of the recess 20, thereby generating a vortex V. The generation of the vortex V consumes the kinetic energy of the bow vertical movement, and the vertical swing of the bow is reduced.

  Since the upward surface 22 and the lateral surface 26 of the recess 20 are smoothly connected by the arc surface 28, the seawater flowing into the recess 20 flows along the arc surface 28, and the vortex V in the recess 20. The generation of is improved. In this way, the energy consumption of the bow vertical motion increases with the generation of the vortex V, and the effect of suppressing the vertical swing of the bow becomes significant.

  The concave portion 20 also serves to reduce an increase in buoyancy at the bow portion due to the bow portion entering the wave, and also serves to suppress lift of the bow due to an increase in buoyancy.

  Since the upward surface 22 of the recess 20 includes a flat surface 22A extending horizontally in the bow / stern direction, the pressure (water pressure) of the wave that has entered acts downward on the flat surface 22A. The movement to rise is suppressed.

  When the bow enters the wave trough, as shown in FIG. 5C, the entire upward surface 22 of the left and right recesses 20 is exposed to the sea, and the seawater that has flowed into the recesses 20 is recessed. This operation is repeated according to the encounter frequency of the wave while the hull is navigating in the opposite wave.

  The wave encounter frequency is defined by the following equation.

    Fec = V + C / λ

  Where Fec: encounter frequency, V: wave velocity, λ: wavelength

  As a result, the pitching motion of the hull during sailing in the waves is suppressed, the ride comfort in the waves is improved, and sea sickness is less likely to occur.

Recess 20 is present independently of the right and left sides of the bow, because the left and right recesses 20 are not in communication, there is no possibility arising seawater flow which crosses from one side in the lateral direction of the hull. As a result, the rolling performance of the hull does not deteriorate. Moreover, since the recessed part 20 is a hollow which has the downward surface 24 on the upper side, the recessed part 20 does not make the deck area used as a dead space.

  The laterally facing surfaces 26 of the left and right recesses 20 are constituted by surfaces that continue smoothly over the entire bow stern direction, and are smoothly connected to the hull outer surfaces 10L and 10R on the stern side, thereby flowing in the recesses 20. The streamline of seawater at the bow and stern direction becomes smoother than the streamline in the ideal hull form. Thereby, the recessed part 20 for pitching movement reduction does not become a cause which a spray wave or a splash produces | generates, and hull resistance (navigation resistance) does not increase.

  In particular, since the rear arc surface 26C that exists on the stern side of the lateral surface 26 and connects the lateral surface 26 and the hull outer surfaces 10L, 10R is a convex and circular arc surface, the ocean current on the stern side of the lateral surface 26 The occurrence of spray waves can be effectively suppressed due to a small amount of peeling.

  Further, since the downward surface 24 and the lateral surface 26 of the left and right recesses 20 are smoothly connected by the circular arc surface 30, the large wave collides with the lateral surface 26 of the recess 20 and jumps up to reach the downward surface 24. Since the seawater is guided to the arc surface 30 and discharged out of the recess 20 with a smooth streamline, the seawater does not collide violently with the downward surface 24 of the recess 20.

  Thereby, it is avoided that the tapping sound and the vibration are generated due to the seawater violently colliding with the downward surface 24 of the recess 20. In particular, since the curvature of the arcuate surface 30 connecting the downward surface 24 and the lateral surface 26 is larger than the curvature of the arcuate surface 28 connecting the upward surface 22 and the lateral surface 26, the effect becomes remarkable.

  In addition, it is advantageous for the efficient production | generation of the vortex V that the curvature of the circular arc surface 28 which connects the upward surface 22 and the horizontal surface 26 is comparatively small.

  The downward surfaces 24 of the left and right recesses 20 and the hull outer surfaces 10L, 10 are smoothly connected by an arc surface 32 connected to the arc surface 30 with an inflection point, as shown in FIGS. It may be. In this case, seawater flowing out of the recess 20 along the downward surface 24 of the recess 20 does not create a spray wave.

  FIG. 8 is a graph showing encounter frequency-bow acceleration characteristics with a conventional trimaran ship when the bow structure according to the above-described embodiment is incorporated. This graph is a test result of a 20 kt equivalent Trimaran ship having a recess 20 (Example) and not having a recess 20 (conventional example) under the same conditions with a wave height of 60 mm. 20 shows the bow acceleration characteristic of the one having the example (example), and the bow acceleration characteristic of the one having the dash-dot line having no recess 20 (conventional example).

  The dimensions of the trimaran ship used in the test are shown in FIG. The dimensions of the recess 20 were 950 mm above the ship bottom, 1000 mm in height, 4500 mm in the longitudinal length (section A + B + C), section B radius Rb = 3000 mm, and section C radius Rc = 2000 mm.

  As is clear from this graph, it is understood that the trimaran ship having the recess 20 has a lower bow acceleration than the trimaran ship not having the recess 20 and the pitching motion of the hull is suppressed.

  In the embodiment described above, the recesses 20 are provided on both the left and right sides of the main hull 10, but the recesses 20 are formed on the bow portion of the demi-hull 12 in addition to the main hull 10 as indicated by phantom lines in FIG. 1. It may be provided on both the left and right sides, or may be provided only on the left and right sides of the bow portion of the demihull 12. In particular, the rolling performance of the hull is improved by providing a recess in the demi-hull. Moreover, the recessed part 20 is not restricted to a trimaran ship, It is applicable also to a catamaran (two hulls) and a monohull (single hull).

DESCRIPTION OF SYMBOLS 10 Main hull 10L, 10R Hull outer surface 11 Bow most advanced part 12 Demihal 14 Bottom of ship 16 Deck 20 Recessed part 22 Upward surface 24 Downward surface 24A Flat surface 26 Lateral surface 26A Flat surface 28, 30, 32 Arc surface

Claims (7)

Has recesses recessed from the outer side of the hull on the left and right sides of the bow part,
The concave portion is located above the inundation line , and when navigating in the waves, when the bow enters the peak of the wave, it sinks into the sea, and when the bow enters the valley of the wave, the upward surface is exposed to the sea, and the upward surface A ship bow structure defined by a downward surface facing from above and a lateral surface extending between the upward surface and the downward surface.   2. The bow of a ship according to claim 1, wherein the laterally facing surface is configured by a surface that is smoothly continuous over the entire bow stern direction, and is smoothly connected to the outer surface of the hull on both the bow side and the stern side. Construction. The bow structure of a ship according to claim 1 or 2, wherein the upward surface and the lateral surface are smoothly connected by an arc surface.   The bow structure of a ship according to any one of claims 1 to 3, wherein the downward surface and the lateral surface are smoothly connected by an arc surface.   The bow structure of a ship according to claim 4, wherein a curvature of an arc surface connecting the downward surface and the lateral surface is larger than a curvature of an arc surface connecting the upward surface and the lateral surface. The ship's bow structure according to any one of claims 1 to 5, wherein the upward surface includes a flat surface extending horizontally in a bow / stern direction. The ship's bow structure according to any one of claims 1 to 6, wherein the ship is a multiple hull having a main hull and a demi-hull, and the recess is provided in at least one of the main hull and the demi-hull.

Images