Ships

Abstract

To provide a ship capable of reducing ship resistance.SOLUTION: A ship comprises a stern end face and a stern bottom face linked to the stern end face. The stern bottom face comprises a main bottom face widening over a sip width direction and inclined upward toward the stern side, an inclined plane provided in the central part in the ship width direction at the end part of the main bottom face and extending downward toward the stern side, and a stern lower part connected to the stern side of the inclined plane and having the rear face flush with the stern end face. The main bottom face and the stern lower part are smoothly connected without forming a connection line on the boundary between these the main bottom face and the stern lower part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This disclosure relates to ships.

Background Art

[0002] Patent Document 1 discloses a ship in which an additional member with a triangular cross-section is attached to the existing transom stern end. This additional member protrudes rearward from the stern end and is inclined slightly downward and rearward from the horizontal. Thereby, the wave-making resistance when the ship is sailing is reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in recent ships, further reduction of operation costs due to improvement of fuel efficiency has been demanded. For this reason, reduction of hull resistance during navigation is important, and it is desired to improve the above-described conventional stern shape to further reduce hull resistance.

[0005] This disclosure has been made to solve the above problems, and an object thereof is to provide a ship capable of reducing hull resistance.

Means for Solving the Problems

[0006] To solve the above problems, the vessel according to the present disclosure comprises a stern end surface and a stern bottom surface connected to the stern end surface, wherein the stern bottom surface comprises a main bottom surface that extends in the width direction of the vessel and slopes upward toward the stern, a stern lower section provided at the center of the rear end of the main bottom surface in the width direction and extending downward toward the stern, and a rear surface connected to the stern side of the sloping surface and flush with the stern end surface, wherein the main bottom surface and the stern lower section are smoothly connected without forming a connecting line at the boundary between the main bottom surface and the stern lower section. The outline of the cross-section perpendicular to the vertical direction of the inclined surface, wherein the outline at the same vertical position of the inclined surface widens in the width direction as it approaches the stern, the lower end of the inclined surface is located on the hull centerline extending in a direction perpendicular to the width direction, and the inclined surface is located higher the further it is outward in the width direction from the hull centerline. . [Effects of the Invention]

[0007] According to the vessels of this disclosure, hull resistance can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view of a vessel according to an embodiment of the present disclosure. [Figure 2] This is a downward perspective view showing the stern of a vessel according to an embodiment of the present disclosure. [Figure 3] This is a rear view of the stern of a vessel according to the embodiment of this disclosure. [Figure 4] This is a view of the stern of a vessel according to the embodiment of this disclosure, seen from below. [Figure 5] This is a side view of the stern of a vessel according to the embodiment of this disclosure. [Figure 6] This figure shows the change in the residual resistance coefficient with respect to the Froude number for a vessel according to the embodiments of this disclosure. [Modes for carrying out the invention]

[0009] Hereinafter, a vessel 1 according to the embodiment of this disclosure will be described with reference to Figures 1 to 6. In this embodiment, a lean vessel with a high cruising speed will be described as an example of a vessel 1. Examples of such a vessel 1 include ferries such as ROPAX, passenger ships, container ships, car carriers (PCTC; Pure Car and Truck Carrier), and cargo ships such as RORO ships.

[0010] (ship) As shown in Figure 1, vessel 1 is a transom stern vessel. Vessel 1 is formed in an elongated shape in the direction of travel D1. That is, the length direction of vessel 1 coincides with the direction of travel D1 of vessel 1. Hereinafter, the direction perpendicular to the direction of travel D1 of the vessel 1, and along the horizontal plane, may be referred to as the ship's width direction D2.

[0011] As shown in Figures 1 and 2, the ship 1 comprises a hull 2, a propeller 20, and a rudder 30.

[0012] (hull) The hull 2 ​​comprises the sides 3, the bottom 4, the upper deck 5, the bow 6, and the stern 10.

[0013] The sides 3 are provided in pairs, facing each other in the ship's width direction D2. Each side 3 extends in the direction of travel D1. The bottom 4 connects the lower portions of the pair of sides 3. The bottom 4 extends in the direction of travel D1, similar to the sides 3. The boundary between the bottom 4 and the sides 3 is shown by a dashed line in Figure 2, but the bottom 4 and the sides 3 are smoothly connected without forming a connecting line at this boundary between the bottom 4 and the sides 3. The upper deck 5 is provided over the top of the pair of sides 3. The upper deck 5 extends in the direction of travel D1, similar to the sides 3. Superstructures not shown, such as the bridge, are installed on the upper deck 5. The bow 6 is located on the forward side of the hull 2 ​​in the direction of travel D1. The stern 10 is located on the aft side of the hull 2 ​​in the direction of travel D1. The bow 6 and stern 10 are connected by the sides 3, the bottom 4, and the upper deck 5. These sides 3, bottom 4, upper deck 5, bow 6, and stern 10 form the hull 2 ​​in a box shape.

[0014] Hereinafter, the front side in the traveling direction D1 of the ship 1 will be referred to as the "bow side", and the rear side in the traveling direction D1 of the ship 1 will be referred to as the "stern side" for explanation.

[0015] (Stern) The stern 10 includes a stern end face 11 and a stern bottom face 12.

[0016] (Stern end face) The stern end face 11 is formed in a planar shape extending in the vertical up-and-down direction. In this embodiment, the stern end face 11 is orthogonal to the traveling direction D1 (the length direction of the ship). The stern end face 11 is formed symmetrically about the hull center line C extending in the traveling direction D1 of the hull 2. The dimension of the stern end face 11 in the ship width direction D2 gradually decreases downward. The lower edge of the stern end face 11 is formed in a dome shape that curves and projects downward when viewed from the stern side.

[0017] (Stern bottom face) The stern bottom face 12 is continuous with the stern end face 11. Also, the stern bottom face 12 is continuous with the side shell 3 and the ship bottom 4. Details of the shape of the stern bottom face 12 will be described later.

[0018] (Propeller) The propeller 20 is provided below the stern bottom face 12. The propeller 20 of this embodiment is a propeller 21.

[0019] The stern 10 of this embodiment is a so-called single-shaft stern. The propeller 21 is arranged in one unit on the hull center line C when viewed from below. The propeller 21 is connected to the ship bottom 4 via a propeller shaft 22. The propeller shaft 22 extends in the traveling direction D1. The propeller shaft 22 penetrates the ship bottom 4. The front end portion of the propeller shaft 22 is connected to a prime mover (not shown) provided in the ship bottom 4. The driving force of the prime mover in the ship bottom 4 is transmitted to the propeller 21 via the propeller shaft 22. The propeller 21 rotates by the driving force of the prime mover. The rotation of the propeller 21 generates a propulsive force for the ship 1. <In addition, the vessel 1 may have a center skeg and two propellers 21 or two azimuth thrusters instead of a single shaft stern and one propeller 21.

[0020] (rudder) The rudder 30 is located aft of the propeller 21. The rudder 30 is positioned along the hull centerline C when viewed from below. The rudder 30 is attached to the stern bottom surface 12 via a rudder post 31. The rudder post 31 protrudes downward from the stern bottom surface 12. The front part of the upper end of the rudder 30 is connected to the lower end of the rudder post 31. The rudder 30 is positioned so that its angle can be changed around the rudder post 31.

[0021] Hereinafter, the perpendicular line extending vertically through the intersection of the full load waterline WL and the bow 6 will be referred to as the forward perpendicular FP, and the perpendicular line extending vertically through the central axis of the rudder post 31 will be referred to as the aft perpendicular AP. The distance D1 in the direction of travel between the forward perpendicular FP and the aft perpendicular AP will be referred to as the perpendicular length Lpp. The perpendicular line extending vertically through the center of the propeller 21 will be referred to as the propeller center perpendicular PC. The aft end of the stern bottom surface 12 will be referred to as the stern end AE.

[0022] (Details of the shape of the stern bottom) The shape of the stern bottom surface 12 will be described in detail below with reference to Figures 2 and 3 through 5. As shown in Figure 2, the stern bottom surface 12 comprises a main bottom surface 13 and a lower stern section 14.

[0023] (Main bottom) The main bottom surface 13 is smoothly connected to the hull bottom 4. The main bottom surface 13 extends from the aft end of the hull bottom 4 toward the stern end surface 11 in the direction of travel D1. Hereinafter, the perpendicular line passing through the front end of the main bottom surface 13 is defined as line AA. Line AA is located between the propeller center perpendicular PC and the aft perpendicular AP in the direction of travel D1.

[0024] The boundary between the main bottom surface 13 and the side surface 3 is shown by a dashed line in Figure 2, but the main bottom surface 13 and the side surface 3 are smoothly connected without forming a connecting line at the boundary between them. Similarly, the boundary between the main bottom surface 13 and the bottom of the hull 4 is shown by a dashed line in Figure 2, but the main bottom surface 13 and the bottom of the hull 4 are smoothly connected without forming a connecting line at the boundary between them.

[0025] Figure 3 discloses the outlines of the stern end face 11 and the cross-section of the stern 10 as viewed from the stern side. The cross-section of the stern 10 disclosed in Figure 3 is a cross-section perpendicular to the direction of travel D1. As representative examples, Figure 3 shows the outline of the cross-section along line AA (dotted line), the outline of the cross-section along the aft perpendicular AP (dotted line), and the outline of the stern end face 11 along the stern end AE (solid line).

[0026] Figure 4 discloses the outline of the cross-section of the stern 10 as viewed from below. The cross-section of the stern 10 disclosed in Figure 4 is a cross-section perpendicular to the vertical direction. Figure 4 discloses multiple outlines of the cross-section of the stern 10 at different heights (z) from the baseline BL of the bottom 4. Denoting the heights (z) from the baseline BL of the bottom 4 as z=a, b, c, d in ascending order, Figure 4 shows the outlines of four cross-sections at heights z=a, b, c, and d. z=a is the height near the lower end of the stern end AE, and z=d is the height of the upper end of the stern bottom surface 12. The dimensional differences ba, cb, and dc are all equal. Furthermore, in addition to the outlines of the four cross-sections at heights z=a, b, c, and d, Figure 4 also shows the outlines of cross-sections at the heights between z=a and b, between z=b and c, and between z=c and d.

[0027] Furthermore, in Figure 4, an example of a knuckle line NL is shown as a dashed line at a cross-section with height z=a, as a comparative example. The knuckle line NL shown in Figure 4 is merely a comparative example and does not exist in this embodiment.

[0028] Figure 5 discloses the outline of the cross-section of the stern 10 as viewed from the ship's width direction D2. The cross-section of the stern 10 disclosed in Figure 5 is a cross-section perpendicular to the ship's width direction D2. Figure 5 discloses the outline of a cross-section along the ship's centerline C, and the outlines of multiple cross-sections located outside the ship's width direction D2 from the ship's centerline C. The lower end of the outline of each cross-section shown in Figure 5 is located higher the further it is located outside the ship's width direction D2 from the ship's centerline C. In Figures 3 to 5, only the shape of the hull 2 ​​is shown, and the propellers 20 and rudder 30 are omitted.

[0029] As shown in Figures 3 to 5, the main bottom surface 13 extends along the width direction D2 of the ship and is connected to the side surfaces 3. The main bottom surface 13 slopes upward towards the stern. Furthermore, the main bottom surface 13 is formed as a smooth curved surface without any ridges.

[0030] (Lower part of the stern) As shown in Figure 2, the stern lower section 14 is located at the center of the main bottom surface 13 at the rear end, in the width direction D2. The stern lower section 14 is smoothly connected to the main bottom surface 13 without forming a connecting line at its boundary. In this embodiment, the stern lower section 14 is integrally formed with the main bottom surface 13. That is, the stern lower section 14 is not an appendage to the hull 2, but is the outer surface shape of the hull 2 ​​itself. The stern lower section 14 has an inclined surface 15 and a rear surface 16.

[0031] The boundary between the inclined surface 15 and the main bottom surface 13 is shown by a dashed line in Figure 2, but the inclined surface 15 and the main bottom surface 13 are smoothly connected without forming a connecting line at the boundary between the inclined surface 15 and the main bottom surface 13. The inclined surface 15 extends downward as it approaches the stern (see Figure 5 in particular). In the fourth outer contour line from the bottom of the cross-sectional outline shown in Figure 5, the shape of the inclined surface 15 is revealed on the stern side of the aft perpendicular AP. The front end of the inclined surface 15 is located between line AA and the aft perpendicular AP. In this embodiment, the front end of the inclined surface 15 is located on the aft perpendicular AP. That is, in this embodiment, the central part of the stern bottom surface 12 in the ship width direction D2 is inclined upward as it approaches the stern from line AA to the aft perpendicular AP, and inclined downward as it approaches the stern from the aft perpendicular AP to the stern end AE.

[0032] The inclined surface 15 is located aft of the propeller 20. The lower edge of the aft end of the inclined surface 15 is located below the lower edge of the stern end surface 11. The lower edge of the inclined surface 15 is formed in a curved, dome shape that protrudes downward when viewed from the stern.

[0033] Furthermore, the aft end of the stern bottom surface 12, including the inclined surface 15, changes from a downward slope to an upward slope as it moves outward in the ship's width direction D2. This point will be explained in more detail with reference to Figure 3.

[0034] For example, as shown in Figure 3, the outline of the stern end face 11 at the stern end AE (solid line) and the outline of the cross section at the aft perpendicular AP (dotted line) intersect between the ship's centerline C in the ship's width direction D2 and the outermost end of the ship's width direction D2 (the end on the side 3 side). In Figure 3, the position in the ship's width direction D2 where the outline of the stern end face 11 at the stern end AE and the outline of the cross section at the aft perpendicular AP intersect is shown by line BB. Inside the ship's width direction D2 from line BB, the outline of the stern end face 11 at the stern end AE is located below the outline of the cross section at the aft perpendicular AP, and as it moves outward in the ship's width direction D2, it approaches the outline of the cross section at the aft perpendicular AP upward. Furthermore, outside the BB line in the ship width direction D2, the outline of the stern end face 11 at the stern end AE is located above the outline of the cross-section at the aft perpendicular AP, and as it moves outward in the ship width direction D2, it moves upward and away from the outline of the cross-section at the aft perpendicular AP. Moreover, as it approaches the side 3, the outline of the stern end face 11 at the stern end AE begins to approach the outline of the cross-section at the aft perpendicular AP again, and almost overlaps at the outermost end in the ship width direction D2.

[0035] Thus, the aft end of the stern bottom surface 12, including the inclined surface 15, inclins downward toward the stern when it is inside the BB line in the ship width direction D2, and inclins upward toward the stern when it is outside the BB line in the ship width direction D2. In other words, the boundary between the inclined surface 15 and the main bottom surface 13 in the ship width direction D2 is located at the BB line.

[0036] Furthermore, as shown in Figure 4, at the aft end of the stern bottom surface 12 including the inclined surface 15, the outline of the same vertical position expands in the width direction D2 as it moves toward the stern.

[0037] Furthermore, at the aft end of the stern bottom surface 12 including the inclined surface 15, the outline of the same vertical position changes to be perpendicular to the ship width direction D2 as it moves upward. More specifically, at the aft end of the stern bottom surface 12 including the inclined surface 15, the outline of the same vertical position becomes less concave toward the ship's centerline C as the height from the bottom 4 increases, and approaches the side 3, becoming a convex shape that slightly protrudes toward the opposite side of the ship's centerline C near the side 3. Also, at the same height as the side 3, the outline of the same vertical position at the aft end of the stern bottom surface 12 including the inclined surface 15 becomes a shape that extends along the side 3.

[0038] Furthermore, as shown in Figures 3 and 4, the entire stern bottom surface 12, including the inclined surface 15, is formed in a smooth curved shape.

[0039] As shown in Figure 3, the rear surface 16 is connected to the stern side of the inclined surface 15 and is flush with the stern end surface 11. The boundary between the rear surface 16 and the stern end surface 11 is shown by a dashed line in Figures 2 and 3, but the rear surface 16 and the stern end surface 11 are smoothly connected without forming a connecting line at this boundary. The rear surface 16 is formed in a U-shape that opens upward when viewed from the stern side.

[0040] (Dimensions of a ship) Next, the planned speed and dimensions of the vessel 1 according to this embodiment will be described. In the vessel 1 of this embodiment, the Froude number Fn of the planned speed is set to 0.20 or more and 0.50 or less. Furthermore, the perpendicular length Lpp of the vessel 1 is 50m or more and 400m or less. The height H1 from the baseline BL of the bottom 4 to the lower end of the stern lower part 14 at the stern end AE is set to 70% or more and 130%, more preferably 80% or more and 120%, of the height H2 from the baseline BL of the bottom 4 to the full load waterline WL. The distance W1 in the width direction between the position D2 in the ship width direction where the outline of the stern end face 11 at the stern end AE, indicated by line BB in Figure 3, intersects with the outline of the cross section at the aft perpendicular AP, and the ship centerline C, is set to 10% or more and 80%, more preferably 20% or more and 60%, of the distance W2 in the width direction between the outermost end D2 of the ship 2 and the ship centerline C. Note that the distance W2 is half the dimension D2 in the ship width direction of the ship 2 (the width of the ship 2).

[0041] (Effects and Benefits) The vessel 1 of this embodiment provides the following effects and advantages. In this embodiment, the stern bottom surface 12 comprises a main bottom surface 13 and a stern lower section 14. The main bottom surface 13 extends across the width direction D2 of the vessel and slopes upward toward the stern. The stern lower section 14 is located at the rear end of the main bottom surface 13, in the center of the width direction D2. The stern lower section 14 has an inclined surface 15 that extends downward toward the stern and a rear surface 16 that is connected to the stern side of the inclined surface 15 and is flush with the stern end surface 11. The main bottom surface 13 and the stern lower section 14 are smoothly connected without forming a connecting line at the boundary between the main bottom surface 13 and the stern lower section 14.

[0042] As the vessel 1 sails, the water flow along the stern 10 is deflected downward by the inclined surface 15 of the lower stern 14. This pushes the stern 10 upward, reducing the amount of sinking of the stern 10. Therefore, the hull resistance caused by the sinking of the stern 10 can be significantly reduced. A significant reduction in hull resistance improves fuel efficiency and lowers operating costs. Incidentally, as shown in the comparative example in Figure 4, if there is a section of abrupt curvature on the stern bottom surface 12 where the curvature changes abruptly, such as a knuckle line NL, the water flow changes abruptly near this section of abrupt curvature. As a result, the hull surface pressure changes abruptly, and the hull resistance increases. In contrast, in this embodiment, since the main bottom surface 13 and the lower stern section 14 are smoothly connected, the water flow and hull surface pressure change gradually. As a result, the hull resistance is further reduced.

[0043] In this embodiment, the aft end of the stern bottom surface 12, including the inclined surface 15, changes from a downward slope to an upward slope as it moves outward in the ship width direction D2.

[0044] This makes it possible to provide an inclined surface 15 only in the submerged portion of the stern bottom surface 12. Therefore, the shape of the conventional ship 1 can be maintained as much as possible. Consequently, the application of the stern 10 of this embodiment becomes easier.

[0045] At the rear end of the stern bottom surface 12 including the inclined surface 15 in this embodiment, the outline of the same vertical position expands in the width direction D2 as it moves toward the stern.

[0046] According to this embodiment, the proportion of the submerged area of ​​the stern 10 occupied by the inclined surface 15 increases. As a result, the lift force pushing up the inclined surface 15 when the vessel 1 is sailing increases. Therefore, the amount of sinking of the stern 10 is further suppressed. Consequently, the hull resistance can be reduced even further.

[0047] At the rear end of the stern bottom surface 12, which includes the inclined surface 15 in this embodiment, the outline of the same vertical position changes so as it moves upward that it becomes perpendicular to the ship width direction D2.

[0048] This allows the shape of the conventional vessel 1 to be maintained as much as possible. Therefore, it becomes easy to apply the stern 10 of this embodiment.

[0049] The entire stern bottom surface 12, including the inclined surface 15 in this embodiment, is formed in a smooth curved shape.

[0050] According to this embodiment, the water flow and hull surface pressure change more gradually near the stern bottom surface 12. As a result, hull resistance is further reduced.

[0051] In this embodiment, the vessel 1 is further equipped with a propeller 20 below the stern bottom surface 12. The inclined surface 15 is located further stern than the propeller 20.

[0052] According to this embodiment, it becomes easier to maintain the clearance between the propeller 20 and the stern bottom surface 12 at a specified interval necessary to maintain vibration characteristics.

[0053] In this embodiment, the lower part of the stern 14 is integrally formed with the main bottom surface 13.

[0054] This makes it easier to avoid forming a connecting line at the boundary between the main bottom surface 13 and the lower stern 14 when forming the lower stern 14. Therefore, it is possible to more reliably slow down the changes in water flow and hull surface pressure near the stern bottom surface 12 and reduce hull resistance.

[0055] In this embodiment, the height H1 from the baseline BL of the bottom of the hull 4 to the lower end of the stern lower section 14 at the stern end AE is set to be 70% to 130%, more preferably 80% to 120%, of the height H2 from the baseline BL of the bottom of the hull 4 to the full load waterline WL. Furthermore, the distance W1 in the width direction between the position D2 in the ship width direction where the outline of the stern end surface 11 at the stern end AE, indicated by line BB in Figure 3, intersects with the outline of the cross section at the aft perpendicular AP, and the ship's centerline C, is set to be 10% to 80%, more preferably 20% to 60%, of the distance W2 in the width direction between the outermost edge D2 of the ship's hull 2 ​​and the ship's centerline C.

[0056] When the Froude number Fn of the planned speed is set to 0.20 or more and 0.50 or less, and the length Lpp between perpendiculars of the ship 1 is 50m or more and 400m or less, the hull resistance reduction effect of the lower stern section 14 of this embodiment is most effectively realized when the lower end height H1 and distance W1 are set as described above.

[0057] Next, the results of verifying the effect of the shape of the stern 10 of this embodiment, as described above, by CFD (Computational Fluid Dynamics) calculations will be explained with reference to Figure 6. In this CFD calculation, the lower end height H1 is set to 80% to 120% of the height H2, and the distance W1 is set to 20% to 60% of the distance W2. The horizontal axis of Figure 6 shows the Froude number Fn, and the vertical axis shows the residual resistance coefficient Cr. Here, the residual resistance coefficient Cr is a coefficient that indicates the magnitude of residual resistance, and residual resistance includes viscous pressure resistance and wave resistance.

[0058] The triangulation points in the figure represent the CFD calculation results of a comparative example (ship 1 without the stern 10 of this embodiment), and the diamond-shaped points represent the CFD calculation results of ship 1 with the stern 10 according to this embodiment. The CFD calculation results of ship 1 with the stern 10 according to this embodiment are connected by straight lines and shown as a so-called broken line graph.

[0059] Figure 6 illustrates the change in the residual resistance coefficient Cr with respect to the Froude number Fn in the range of 0.23 to 0.26. In each calculation result shown in Figure 6, the residual resistance coefficient Cr changes in the range of 0.003 to 0.009. The residual resistance coefficient Cr of the ship 1 equipped with the stern 10 of this embodiment increases as the Froude number Fn increases.

[0060] As shown in Figure 6, the Froude number Fn is around 0.245, and the residual resistance coefficient Cr is reduced by approximately 7% compared to the comparative example. This result indicates that the ship 1 of this embodiment has the effect of reducing hull resistance.

[0061] (Other embodiments) Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure. In the above embodiment, line AA is assumed to be located between the propeller center perpendicular PC and the rear perpendicular AP in the direction of travel D1, but this is not the only possible configuration. For example, line AA may coincide with the propeller center perpendicular PC in the direction of travel D1.

[0062] In the above embodiment, the lower stern section 14 was assumed to be integrally formed with the main bottom surface 13, but this is not the only possible configuration. For example, the lower stern section 14 may be added to the main bottom surface 13 as an aftermarket addition.

[0063] <Note> The vessel 1 described in each embodiment can be understood, for example, as follows:

[0064] (1) The vessel 1 according to the first embodiment comprises a stern end surface 11 and a stern bottom surface 12 connected to the stern end surface 11, wherein the stern bottom surface 12 comprises a main bottom surface 13 that extends over the width direction D2 and slopes upward toward the stern, and a stern lower part 14 provided at the center of the rear end of the main bottom surface 13 in the width direction D2 and extending downward toward the stern, and a rear surface 16 connected to the stern side of the sloping surface 15 and flush with the stern end surface 11, wherein the main bottom surface 13 and the stern lower part 14 are smoothly connected without forming a connecting line at the boundary between the main bottom surface 13 and the stern lower part 14.

[0065] As the vessel 1 sails, the water flow along the stern 10 is deflected downward by the inclined surface 15 of the lower stern 14. This pushes the stern 10 upward, reducing the amount of sinking of the stern 10. Therefore, the hull resistance caused by the sinking of the stern 10 can be significantly reduced. Incidentally, if there is a section of abrupt curvature, such as a knuckle line, on the stern bottom surface 12, the water flow changes abruptly near this section of abrupt curvature. This causes a rapid change in the hull surface pressure, increasing hull resistance. In contrast, in this embodiment, since the main bottom surface 13 and the lower stern section 14 are smoothly connected, the water flow and hull surface pressure change gradually. As a result, hull resistance is further reduced.

[0066] (2) The vessel 1 of the second embodiment is the vessel 1 of (1), wherein the aft end of the stern bottom surface 12 including the inclined surface 15 may change from a downward slope to an upward slope as it moves outward in the width direction D2.

[0067] This makes it possible to provide a sloping surface 15 only in the submerged portion of the stern bottom surface 12. Therefore, the shape of the conventional ship 1 can be maintained as much as possible.

[0068] (3) The third embodiment of the vessel 1 is the vessel 1 of (1) or (2), wherein at the aft end of the stern bottom surface 12 including the inclined surface 15, the outline lines at the same vertical position may widen in the width direction D2 as they move toward the stern.

[0069] According to this embodiment, the proportion of the submerged area of ​​the stern 10 occupied by the inclined surface 15 increases. As a result, the lift force pushing up the inclined surface 15 when the vessel 1 is sailing increases. Therefore, the amount of sinking of the stern 10 is further suppressed.

[0070] (4) The fourth embodiment of the vessel 1 is the vessel 1 of (3), wherein at the aft end of the stern bottom surface 12 including the inclined surface 15, the outline of the same vertical position changes so as it goes upward that it is perpendicular to the width direction D2.

[0071] This allows the shape of the conventional ship 1 to be maintained as much as possible.

[0072] (5) The fifth embodiment of the vessel 1 is any of the vessels 1 described in (1) to (4), wherein the entire stern bottom surface 12 including the inclined surface 15 may be formed in a smooth curved shape.

[0073] According to this embodiment, the water flow and hull surface pressure change more gradually near the stern bottom surface 12.

[0074] (6) The sixth embodiment of the vessel 1 is any of the vessels 1 described in (1) to (5), further comprising a propeller 20 below the stern bottom surface 12, wherein the inclined surface 15 is located sternward from the propeller 20.

[0075] According to this embodiment, it becomes easier to maintain the clearance between the propeller 20 and the stern bottom surface 12 at a specified interval necessary to maintain vibration characteristics.

[0076] (7) The vessel 1 of the seventh embodiment is any of the vessels 1 of (1) to (6), wherein the lower stern 14 may be integrally formed with the main bottom surface 13.

[0077] This makes it easier to avoid forming a connecting line at the boundary between the main bottom surface 13 and the lower stern 14 when forming the lower stern 14. [Explanation of Symbols]

[0078] 1...Ship 2...Hull 3...Side 4...Bottom 5...Upper deck 6...Bow 10...Stern 11...Stern end face 12...Stern bottom face 13...Main bottom face 14...Lower part of stern 15...Inclined surface 16...Rear face 20...Propeller 21...Propeller 22...Propeller shaft 30...Rudder 31...Rudder post C...Hull centerline D1...Direction of travel D2...Width direction WL...Full load waterline BL...Baseline FP...Forward perpendicular AP...Aft perpendicular Lpp...Length between perpendiculars AE...Stern end PC...Propeller centerline H1...Lower end height H2...Height W1...Distance W2...Distance NL...Knuckle line (comparative example)

Claims

1. The stern end face and, The stern bottom surface connected to the aforementioned stern end surface, Equipped with, The aforementioned stern bottom surface is The main bottom surface extends in the width direction of the ship and slopes upward towards the stern, The lower stern has a sloping surface provided in the center of the width direction of the main bottom surface at the rear end, which extends downward toward the stern, and a rear surface connected to the stern side of the sloping surface and flush with the stern end surface, Equipped with, The main bottom surface and the lower stern are smoothly connected without forming a connecting line at the boundary between the main bottom surface and the lower stern. The outline of the cross-section perpendicular to the vertical direction of the inclined surface, wherein the outline at the same vertical position on the inclined surface widens in the width direction of the ship as it approaches the stern, The lower end of the aforementioned inclined surface is located on the hull centerline extending in a direction perpendicular to the ship's width direction. The aforementioned inclined surface is located on a vessel where it is positioned higher the further outward it is from the centerline of the hull in the direction of the ship's width.

2. The vessel according to claim 1, wherein the aft end of the stern bottom surface, including the inclined surface, changes from a downward slope to an upward slope as it is directed outward in the width direction of the vessel.

3. The vessel according to claim 1, wherein at the aft end of the stern bottom surface including the inclined surface, the outline of the vessel changes so that it is perpendicular to the width direction as it moves upward, at the same vertical position.

4. The vessel according to claim 1 or 2, wherein the entire stern bottom surface, including the inclined surface, is formed in a smooth curved shape.

5. Further, a propulsion system is provided below the bottom surface of the stern, The vessel according to claim 1 or 2, wherein the inclined surface is located aft of the propeller.

6. The vessel according to claim 1 or 2, wherein the lower part of the stern is integrally formed with the main bottom surface.

Images