Ship and positional determination method for fin installed in this ship

Abstract

To provide a ship capable of realizing the improvement of energy saving effect and to provide a positional determination method for a fin installed in this ship.SOLUTION: This method comprises: an initial data acquisition step to acquire initial data including ship type data based on the shape of a hull 2 and shape data based on the shape of a fin 4; a positional data acquisition step in which multiple positional data representing positions of the fin 4, including a distance L between a pair of fins, are prepared in advance, and one positional data is acquired from among them; a calculation step to calculate energy saving effect by calculating based on the initial data and the positional data; and a storage step to store the energy saving effect. This method comprises: a repeat step to repeat the positional data acquisition step, the calculation step, and the storage step multiple times while changing the acquired positional data; and a determination step to determine one positional data based on the energy saving effect after the repeat step.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for determining the position of a ship and fins installed on the ship, and more particularly to a method for determining the position of a ship capable of realizing an improvement in energy-saving effect and fins installed on the ship.

Background Art

[0002] Ships with fins installed in the bilge area near the bottom of the ship have been variously proposed (see, for example, Patent Document 1). The ship described in Patent Document 1 improved the propulsion efficiency by changing the direction of the bilge vortex passing above the propeller and guiding it to the propeller with the fins. The bilge vortex is a factor that increases the hull resistance, but this ship tried to improve the propulsion efficiency as much as possible by guiding the bilge vortex to the propeller.

[0003] The invention described in Patent Document 1 was targeted at full-form ships where the influence of the bilge vortex is relatively large. A full-form ship refers to a ship with a block coefficient CB of 0.75 or more. For ships other than full-form ships (block coefficient CB < 0.75), bilge vortices are less likely to occur, and there was not much of a situation where the hull resistance increased due to bilge vortices. Therefore, the application of the aforementioned fins has not been considered for ships that are thinner than full-form ships.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a method for determining the position of a ship capable of realizing an improvement in energy-saving effect and fins installed on the ship.

Means for Solving the Problems

[0006] In a ship for achieving the above object, which includes a hull, a propeller installed on the hull, and a pair of fins installed on the lower surface side of the hull, the pair of fins are installed in a range where the entire fin is below the axis of the propeller and above the bottom of the hull, and the distance between the pair of fins is less than 50% of the hull width of the hull.

[0007] A method for determining the position of fins installed on a ship for achieving the above object is a determination method for determining the position of a pair of fins installed on the lower surface side of the hull, and includes an initial data acquisition step of acquiring initial data including ship type data based on the shape of the hull and shape data based on the shape of the fins, a position data acquisition step of acquiring one from a plurality of previously prepared position data indicating the position of the fins including the distance between the pair of fins, a calculation step of calculating an energy saving effect by performing calculations based on the initial data and the position data, and a storage step of storing the energy saving effect. While changing the position data acquired in the position data acquisition step, the position data acquisition step, the calculation step, and the storage step are repeatedly performed a plurality of times, and after the repetition step, a determination step of determining one of the position data based on the energy saving effect.

Advantages of the Invention

[0008] According to the present invention, by arranging a pair of fins in a state of being relatively close in the ship width direction, vortices can be actively generated in the vicinity of the fins. When these vortices are guided to the propeller, the water flow velocity around the propeller decreases. This is advantageous for improving the energy saving effect of the ship.

Brief Description of the Drawings

[0009]

Figure 1

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, it will be described based on the embodiments in which the ship is shown in the drawings. In the drawings, the longitudinal direction of the ship is indicated by arrow y, the width direction perpendicular to the longitudinal direction is indicated by arrow x, and the vertical direction perpendicular to the longitudinal direction y and the width direction x is indicated by arrow z.

[0011] As illustrated in FIGS. 1 and 2, the ship 1 includes a hull 2, a propeller 3 installed on the hull 2, and a pair of fins 4 installed on the lower surface side of the hull 2. The hull 2 is configured as a so-called slender ship with a block coefficient CB≦0.6. Specifically, the ship 1 is configured as, for example, a container ship or an automobile carrier. In FIG. 2, for the sake of explanation, the range through which the propeller 3 passes by rotation is shown by a broken line as a projection plane 3a. The projection plane 3a refers to the range of a virtual circle having the same diameter and center position as the propeller 3.

[0012] As illustrated in FIG. 2, the fins 4 are entirely installed in a range S1 that is below the axis 3b of the propeller 3 and above the bottom 2a of the hull 2. The upper end of the range S1 is set at the center of the axis 3b. The upper end of the range S1 may be set at the lower end of the axis 3b. The bottom 2a refers to the lowest position of the hull 2 in the vertical direction z. The lower end of the range S1 is set, for example, on the lower surface of the keel.

[0013] The interval L between the pair of fins 4 is set in a range smaller than 50% with respect to the hull width B. That is, the interval L between the fins 4 is set in a range satisfying L<0.5B. Here, the interval L between the pair of fins 4 refers to the distance at the place where the distance between the pair of fins 4 is the smallest in the ship width direction x. The hull width B is the length of the part where the width of the hull 2 is the largest, and is sometimes referred to as the overall width (BOA). For example, the length that is 50% of the hull width B may be denoted as 0.5B.

[0014] In a so-called slender ship, hardly any bilge vortices are generated. When the fins 4 are installed on the slender ship, vortices are generated from the vicinity of the fins 4, and these vortices are guided to the propeller 3. Due to the influence of the vortices, the flow velocity of the water around the propeller 3 decreases. Since the propeller 3 pushes out the water with a decreased flow velocity backward, the propulsion efficiency of the ship 1 is improved. Along with the improvement of the propulsion efficiency, the energy-saving effect of the ship 1 can be improved.

[0015] For a ship-shaped ship 1 in which bilge vortices are less likely to occur, by installing fins 4, vortices can be actively generated and guided to the propeller 3. Although the resistance deteriorates with the installation of the fins 4 and the generation of vortices, the inventor of the present case has discovered that a propulsive gain exceeding this can be obtained.

[0016] The ship 1 is not limited to a slender ship. A pair of fins 4 can be installed for ships of any hull form. However, ships with a block coefficient CB < 0.75 are more likely to obtain a greater energy-saving effect. It is desirable that the ship 1 satisfies the condition that the block coefficient CB ≤ 0.6. According to this configuration, the energy-saving effect can be further improved.

[0017] It is desirable that the ship 1 satisfies the condition that the aft body prismatic coefficient Cpa ≤ 0.76 in the aft part of the hull 2. According to this configuration, it is easier to improve the energy-saving effect.

[0018] As illustrated in FIG. 1, in the longitudinal direction y of the ship, it is desirable that the ship 1 has a length of the stern section S3, which is on the rear side of the parallel middle body S2 and on the front side of the after perpendicular AP, of 0.35Lpp or more. According to this configuration, the energy-saving effect can be further improved. Here, Lpp (Length of ship between perpendiculars) refers to the horizontal distance from the forward perpendicular FP to the after perpendicular AP. The parallel middle body S2 refers to the range where the cross-section perpendicular to the longitudinal direction y has the same shape. 0.35Lpp refers to a length that is 35% of the length between perpendiculars Lpp. It can also be said that for this ship 1, the boundary line 5 between the parallel middle body S2 and the stern section S3 rises toward the stern from the position where it becomes the square station 4. The square station is obtained by dividing the hull 2 into ten equal parts in the longitudinal direction y and numbering them from the stern side.

[0019] When the ship does not have the fins 4, it is desirable that the ship 1 be such that the range where the flow velocity of the water flow flowing into the propeller plane with respect to the ship speed is 30% or less is 50% or less of the area of the projection plane 3a of the propeller 3. The ship 1 may be such that the range where the flow velocity is 30% or less is 30% or less of the area of the projection plane 3a. For the ship 1 that does not obtain the wake gain, the energy saving effect can be improved by installing the fins 4. By performing CFD (Computational Fluid Dynamics) calculations with the ship type data based on the shape of the hull 2 as the input value, a wake distribution diagram can be obtained. The range of the flow velocity can be grasped from this wake distribution diagram.

[0020] The cross-sectional shape of the fins 4 can be, for example, a wing shape. The overall shape of the fins 4 may be a substantially rectangular parallelepiped shape. Also, the shape of the fins 4 may be a shape similar to the shape of known fins.

[0021] As illustrated in FIG. 2, the pair of fins 4 are installed at equal distances from the center line CL of the hull in the ship width direction x. It can also be said that one fin 4 and the other fin 4 are installed at the target positions with respect to the center line CL of the hull. In FIG. 2, the center line CL of the hull is shown as a dashed-dotted line for the sake of explanation. When the interval L between the pair of fins 4 is, for example, 0.3B, each fin 4 is installed at a position 0.15B from the center line CL of the hull.

[0022] The interval L between the pair of fins 4 may be set in the range of 10% or more and 30% or less with respect to the ship width B. That is, the interval L of the fins 4 is set in the range that satisfies 0.1B ≦ L ≦ 0.3B. This is more advantageous for improving the energy saving effect of the ship 1.

[0023] As illustrated in FIG. 2, when viewed in the longitudinal direction y from the stern side of the ship 1, a pair of fins 4 can be configured to be installed in a state where at least a part of the fins 4 is outside the projection plane 3a of the propeller 3. As in the embodiment illustrated in FIG. 2, it is desirable that the fins 4 be installed in a state where the entire fins 4 are outside the projection plane 3a. A part of the fins 4 may be inside the projection plane 3a. In this case, it is desirable that the range inside the projection plane 3a within the area of the fins 4 when viewed from the stern side be 10% or less.

[0024] The vortices generated by the fins 4 arranged outside the projection plane 3a of the propeller 3 grow while moving toward the propeller 3. The flow velocity of the water flow around the propeller 3 can be made smaller. This is advantageous for improving the energy-saving effect of the ship 1.

[0025] Next, a method for determining the positions of the pair of fins 4 installed on the lower surface side of the hull 2 will be described. The determination of the positions of the fins 4 is executed by various known computers. This computer has a central processing unit (CPU), a main memory unit (memory), and an auxiliary storage unit (e.g., HDD). The computer may have an input unit (keyboard, mouse) and an output unit (display, printer).

[0026] As illustrated in FIG. 3, first, the computer acquires ship type data d1 based on the shape of the hull 2 and shape data d2 based on the shape of the fins 4 (hereinafter, sometimes referred to as the initial data acquisition step S10). The ship type data d1 is composed of, for example, design data when building the ship 1. The ship type data d1 may be composed of data obtained by estimating the hull shape from, for example, a general arrangement drawing or a photograph. The ship type data d1 may be composed of data obtained by performing three-dimensional measurement on the actual ship 1. The shape data d2 is data indicating the preset shape of the fins 4. The shape data d2 is composed of, for example, design data when manufacturing the fins 4 or data obtained by three-dimensionally measuring the actual fins 4.

[0027] Next, the computer acquires one piece of position data d3 indicating the positions of the pair of fins 4 including the interval L therebetween (hereinafter sometimes referred to as the position data acquisition step S20). A plurality of pieces of position data d3 are prepared in advance as illustrated in FIG. 4. The plurality of pieces of position data d3 are composed of data corresponding to the coordinates in the ship length direction y, the vertical direction z, and the ship width direction x.

[0028] Specifically, for example, data indicating the distance from the after perpendicular AP as a percentage [%] based on the length between perpendiculars Lpp of the ship is set as the position data in the ship length direction y. The ship length direction values "15" of the positions P1 - P4 illustrated in FIG. 4 correspond to the positions that are 15% of the length between perpendiculars Lpp from the after perpendicular AP illustrated in FIG. 5. The length that is 15% of the length between perpendiculars Lpp may be denoted as 0.15Lpp.

[0029] For example, based on the length in the vertical direction z of the range S1 that is below the shaft 3b and above the ship bottom 2a, data indicating the distance from the ship bottom 2a as a percentage [%] is set as the position data in the vertical direction z. The vertical direction z value "18" of the position P1 illustrated in FIG. 4 corresponds to the position that is 18% of the range S1 from the ship bottom 2a illustrated in FIG. 6. The length that is 18% of the range S1 may be denoted as 0.18S1.

[0030] For example, data indicating the distance from the hull center line CL as a percentage [%] based on the hull width B is set as the position data in the ship width direction x. The value "5.0" of the interval L / 2 of P1 illustrated in FIG. 4 corresponds to the position that is 5% of the hull width B from the hull center line CL illustrated in FIG. 6. The length that is 5% of the hull width B may be denoted as 0.05B. This interval L / 2 is half the length of the interval L between the pair of fins 4.

[0031] In this embodiment, as illustrated in FIG. 5, when the hull 2 is viewed from the side, the front end of the fin 4 is aligned with the position corresponding to the position data d3. Also, as illustrated in FIG. 6, when viewed from the stern side toward the bow side, the lower left corner of the fin 4, which is substantially rectangular, is aligned with the position corresponding to the position data d3. The position to be aligned with the position data d3 is not limited to the above, and any point of the fin 4 set in advance may be configured to be aligned with the position data d3. In FIGS. 5 and 6, the position of the fin 4 corresponding to the position data d3 is shown by a dashed line for the sake of explanation.

[0032] The method for setting the position data d3 prepared in advance is not limited to the above. It is sufficient if the position of the fin 4 can be determined in the three-dimensional coordinates of the longitudinal direction y, the vertical direction z, and the lateral direction x of the ship. Also, the number (resolution) of the position data d3 prepared in advance can be arbitrarily determined.

[0033] A plurality of pieces of position data d3 prepared in advance can be generated based on the ship type data d1. For example, the surface of the hull 2 can be divided into a plurality of parts in a grid pattern, and the intersection points of the grids can be set as the position data d3. At this time, the position data d3 is set within the range where the fin 4 may be installed. The position data d3 is set within the range that is on the bow side of the propeller 3 in the longitudinal direction y and on the stern side of the central part (0.50Lpp) of the hull 2. The position data d3 may be set within the range of the stern part S3 in the longitudinal direction y. The position data d3 is set within the range S1 that is below the axis 3b of the propeller 3 and above the bottom 2a of the hull 2 in the vertical direction z. The position data d3 is set within the range smaller than 0.25B from the center line CL of the hull in the lateral direction x.

[0034] The method for generating a plurality of pieces of position data d3 prepared in advance is not limited to the above. The space within the range where the fin 4 may be installed may be virtually divided into a three-dimensional grid pattern, and the intersection points of the grids may be set as the position data d3.

[0035] Among the plurality of position data d3 prepared in advance, there may be locations that do not meet the installation conditions of the fin 4. For example, in the position P1 in FIG. 6, since a part of the fin 4 is below the bottom of the ship 2a, it does not meet the installation conditions of the fin 4. Also, when the space is virtually divided into a grid and the intersection points of the grid are set as the position data d3, there may be locations where the fin 4 is away from the hull 2 and cannot be fixed. When the computer acquires the position data d3, it may be configured to exclude inappropriate position data d3 as described above (hereinafter sometimes referred to as the exclusion step S21). As illustrated in FIG. 3, in the exclusion step S21, for one selected position data d3, it is determined whether it meets the installation conditions of the fin 4 and whether it can be fixed to the hull 2. Inappropriate position data d3 is excluded, and another position data d3 is acquired by the computer.

[0036] As illustrated in FIG. 3, based on the ship type data d1, the shape data d2, and one position data d3, the computer performs CFD calculations to calculate the self-propulsion element and the resistance element, and calculates the energy-saving effect d4 from the self-propulsion element and the resistance element (hereinafter sometimes referred to as the calculation step S30). In the calculation step S30, the energy-saving effect d4 may be calculated using only the self-propulsion element. In the CFD calculation, based on the knowledge obtained through water tank experiments etc., the energy-saving effect d4 corresponding to the ship type data d1 etc. can be estimated.

[0037] The energy-saving effect d4 obtained by the CFD calculation is stored in the main memory unit or the auxiliary memory unit of the computer (hereinafter sometimes referred to as the storage step S40). In addition to the energy-saving effect d4 in the storage step S40, the self-propulsion element and the resistance element may also be stored. In the storage step S40, as illustrated in FIG. 4, the energy-saving effect d4 is stored for each position data d3. For the position data d3 excluded in the exclusion step S21, the energy-saving effect d4 may not be acquired as illustrated in FIG. 4.

[0038] While changing the position data d3 acquired in the position data acquisition step S20, the position data acquisition step S20, the calculation step S30, and the storage step S40 are repeated a plurality of times (hereinafter sometimes referred to as the repetition step S50). In FIG. 3, the range that is repeatedly executed for explanation purposes is surrounded by a dashed line. In the repetition step S50, while changing the positions in the ship length direction y, the vertical direction z, and the ship width direction x, the energy saving effects corresponding to the respective position data d3 are acquired respectively.

[0039] The energy saving effect d4 calculated in the calculation step S30 indicates the horsepower reduction efficiency [%] of a ship having appendages such as fins 4 with reference to a ship having no appendages such as fins 4 at the same ship speed. The larger the value of the energy saving effect d4, the greater the fuel consumption reduction effect by the appendages such as fins 4. Specifically, the energy saving effect d4 is composed of, for example, the total value of the horsepower reduction rate based on the viscous resistance coefficient, the thrust reduction coefficient, the wake coefficient, and the propeller behind efficiency ratio. For example, if Δη(total) = (Δη(K) + Δη(1 - t) + Δη(1 - w) + Δη(ηR)), this Δη(total) can be used as the value of the energy saving effect d4. Here, K represents viscous resistance, t represents the thrust reduction coefficient, w represents the wake coefficient, and ηR represents the propeller behind efficiency ratio. Δη [%] indicates the total improvement rate (= estimated horsepower reduction rate) of the viscous resistance K and the self-propulsion elements when the ship is equipped with fins 4 with reference to the case where the ship is not equipped with fins 4. Therefore, when the ship does not have appendages such as fins 4, Δη(total) = 0%. It can be said that the larger the value of Δη(total), the greater the energy saving effect d4 obtained. Note that the self-propulsion elements are a general term for the thrust reduction coefficient, the wake coefficient, and the propeller behind efficiency ratio.

[0040] FIG. 7 is a graph plotting the energy-saving effect d4 calculated by the arithmetic step S30. In FIG. 7, for all the places where the fins 4 can be installed along the surface of the hull 2, the energy-saving effect d4 is calculated. Here, the horizontal axis is the distance L / 2 [%] from the center line CL of the hull to the fins 4, and the vertical axis is Δη(total) [%]. The horizontal axis indicates the distance L / 2 from the center line CL of the hull to the fins 4 as a percentage [%] based on the hull width B. When the plotted points are located above the boundary line where Δη(total) = 0, an energy-saving effect can be obtained, and when they are located below, no energy-saving effect can be obtained.

[0041] From FIG. 7, in this embodiment, it can be seen that an energy-saving effect can be obtained in the range of 5% ≤ L / 2 ≤ 15%. When shown as the interval L between the pair of fins 4, it becomes 0.1B ≤ L ≤ 0.3B. That is, it can be understood that when the interval L between the pair of fins 4 is set in the range of 10% to 30% of the hull width B, the ship 1 is likely to obtain an energy-saving effect.

[0042] Note that even when L / 2 = 5% as illustrated in FIG. 7, there may be cases where a sufficient energy-saving effect cannot be obtained depending on the installation position of the fins 4. When the shape of the hull 2 or the shape of the fins 4 changes, the graph shown in FIG. 7 also changes. Depending on the shape of the hull 2, for example, even when L / 2 = 20%, an energy-saving effect may be obtained.

[0043] When the calculation of the energy-saving effect d4 is completed for a plurality of pre-prepared position data d3 by repeating the arithmetic step S30 and the like, the repetition step S50 ends and proceeds to the next step. After the repetition step S50, one position data d3 is determined based on the energy-saving effect d4 (hereinafter sometimes referred to as the determination step S60).

[0044] In the determination step S60, for example, the one with the largest value among the plurality of energy-saving effects d4 is selected, and the position data d3 corresponding to this energy-saving effect d4 is extracted. For example, as illustrated in FIG. 7, when the value of the energy-saving effect d4 corresponding to the position P35, i.e., "+1.0%", is the highest, the position data d3 corresponding to this position P35 is determined in the determination step S60.

[0045] The position data d3 determined in the determination step S60 is not limited to the position data d3 corresponding to the energy-saving effect d4 with the highest value. The installation position of the fin 4 may be determined by comparing with other conditions such as the efficiency of the installation work of the fin 4. In the determination step S60, the configuration may be such that the computer determines one position data d3 from among the plurality of position data d3. In the determination step S60, the configuration may be such that the operator determines one position data d3 with reference to the graph of FIG. 7 output from the computer.

[0046] There are a method of calculating the energy-saving effect d4 from the resistance element and the self-propulsion element and a method of calculating it only from the self-propulsion element. In the embodiment illustrated in FIG. 7, the installation position of the fin 4 is determined based on the energy-saving effect d4 calculated from the resistance element and the self-propulsion element. The energy-saving effect d4 may be evaluated based only on the self-propulsion element, and the position data d3 that gives a high energy-saving effect d4 may be determined as the installation position of the fin 4 in the determination step S60.

[0047] Based on the position data d3 determined in the determination step S60, a pair of fins 4 is installed at the corresponding position Pn (hereinafter sometimes referred to as the installation step). By installing the fins 4 at appropriate positions on new-built ships as well as existing ships, the energy-saving effect of the ship 1 can be improved.

[0048] The exclusion step S21 illustrated in FIG. 3 is not an essential constituent element of the present invention. When preparing a plurality of position data d3 in advance, the position data d3 in a range where the fin 4 cannot be installed and in a range not satisfying the conditions of the installation position of the fin 4 may not be included. When the calculation step S30 is executed in a state where inappropriate position data d3 is not included, the calculation efficiency can be improved. Since the calculation is not performed in a range where the fin 4 cannot be installed or where no energy saving effect can be expected, a plurality of calculation steps S30 can be completed in a relatively short time.

[0049] As illustrated in FIG. 8, the position data d3 may include an attachment angle θ1 which is the inclination of the fin 4 with respect to the ship width direction x when viewed in the ship length direction y. The attachment angle θ1 is defined, for example, as the angle formed by the ship width direction x and the upper surface 4a of the fin 4. This attachment angle θ1 indicates the inclination of the fin 4 with the ship length direction y as the central axis. When the upper surface 4a of the fin 4 is not a flat surface but a curved surface, or when the inclination of the upper surface 4a changes along the ship length direction y, a reference plane may be set in advance for the fin 4, and the angle formed by this plane and the ship width direction x may be defined as the attachment angle θ1. When the fin 4 is installed horizontally, the attachment angle θ1 = 0°, and when the end of the fin 4 in the ship width direction x inclines downward, the attachment angle θ1 increases such as 15° or 30°.

[0050] As illustrated in FIG. 9, the position data d3 may include an attachment angle θ2 which is the inclination of the fin 4 with respect to the ship width direction x when viewed in the vertical direction z. In this embodiment, the shape of the fin 4 is formed in a trapezoidal shape when viewed in the vertical direction z. This fin 4 is formed in a trapezoidal shape in which the side located on the front side in the ship length direction y and the side located on the rear side are substantially parallel. The attachment angle θ2 is defined, for example, as the angle formed between the ship width direction x and the front surface 4b of the fin 4. This attachment angle θ1 indicates the inclination of the fin 4 with the vertical direction z as the central axis. When the front surface 4b of the fin 4 is not a flat surface but a curved surface, or when the inclination of the front surface 4b changes along the ship width direction x, a reference plane may be set in advance for the fin 4, and the angle formed between this plane and the ship width direction x may be defined as the attachment angle θ2. When the fin 4 is installed at a right angle to the ship length direction y, the attachment angle θ2 = 0°, and when the end of the fin 4 in the ship width direction x inclines toward the rear side, the attachment angle θ2 increases, such as 10° or 20°. The attachment angles θ1 and θ2 can improve the energy-saving effect more when set to 15° or 60° than when set to 0°.

[0051] As illustrated in FIG. 10, the shape of the fin 4 may have a configuration in which the joint portion between the fin 4 and the hull 2 is a smooth arc when viewed in the vertical direction z.

[0052] In this specification, the case of the attachment angle which is the inclination of the fin 4 with respect to the ship width direction x includes the case of the attachment angle θ1 which represents the inclination of the fin 4 with the ship length direction y as the central axis, the case of the attachment angle θ2 which represents the inclination of the fin 4 with the vertical direction z as the central axis, and the case including both the attachment angles θ1 and θ2.

[0053] When the determination method for determining the position of the fin 4 includes the exclusion step S21, the feasibility of exclusion is determined in consideration of the mounting angle θ1. When the mounting angle θ1 is 0° at the position P1 in FIG. 6, the fin 4 does not protrude below the bottom of the ship 2a. Since this position P1 (θ1 = 0°) is an appropriate position, it is not excluded in the exclusion step S21. When the mounting angle θ1 is 45° at the position P1, the fin 4 protrudes below the bottom of the ship 2a. Since this position P1 (θ1 = 45°) is an inappropriate position, it is excluded in the exclusion step S21.

[0054] When the position data d3 includes at least one of the mounting angle θ1 or the mounting angle θ2, the calculation step S30 may be repeatedly performed while changing the mounting angles θ1 and θ2. In this case, in the repetition step S50, the calculation is repeated while the mounting angles θ1 and θ2 are changed together with the position Pn of the fin 4.

[0055] After the position Pn of the fin 4 is determined in the determination step S60, repeated calculations may be performed while changing the mounting angles θ1 and θ2. In this case, after the completion of the repetition step S50, with the position Pn of the fin 4 fixed, the calculation is repeated while only the mounting angles θ1 and θ2 are changed. Determining the mounting angles θ1 and θ2 after the position Pn of the fin 4 is determined can suppress the amount of calculation.

[0056] In the installation step, a pair of fins 4 are installed on the hull 2 according to the determined position of the fin 4 and the mounting angles θ1 and θ2.

[0057] The shape of the fin 4 is not limited to the foregoing configuration. When viewed in the vertical direction z, the fin 4 may be formed in a shape composed of only a continuous curve, a shape composed of a combination of a line segment and a continuous curve, or a shape formed by a plurality of line segments (polygon). Specifically, for example, as illustrated in FIG. 11, the shape of the fin 4 may be formed in an arc shape protruding outward in the ship width direction x when viewed in the vertical direction z. In this embodiment, the fin 4 is formed in a shape that is approximately half of an ellipse. The fin 4 may be formed in a shape that is approximately half of a circle when viewed in the vertical direction z. Also, as illustrated in FIG. 12, the shape of the fin 4 may be formed in a shape that is approximately 1 / 4 of a circle. This fin 4 is formed in a fan shape with a central angle of approximately 90° surrounded by a radius substantially parallel to the ship length direction y and a radius substantially parallel to the ship width direction x. This fin 4 is installed on the hull 2 in a direction in which the arc is located on the front side of the ship 1 and on the outer side in the ship width direction x.

[0058] As illustrated in FIG. 13, the shape of the fin 4 may be formed in a trapezoidal shape when viewed in the vertical direction z. This fin 4 is formed in a trapezoidal shape in which the inner side and the outer side in the ship width direction x are substantially parallel. As illustrated in FIG. 14, the fin 4 may be formed in a trapezoidal shape in which the front side and the rear side in the ship length direction y are substantially parallel.

[0059] As illustrated in FIG. 15, the shape of the fin 4 may be formed in a polygon when viewed in the vertical direction z. This fin 4 is composed of a hexagon. The shape of the fin 4 is not limited to this, and it may be formed in a polygon including a triangle.

[0060] As illustrated in FIG. 16, the cross-sectional shape of the fin 4 can be a wing shape. FIG. 16 shows the A-A cross-section of the fin 4 in FIG. 15. The cross-sectional shape of the fin 4 is not limited to the above, and it may be formed in a rectangle, a polygon, an ellipse, or a semi-circle as illustrated in FIG. 16.

Explanation of Signs

[0061] 1 Ship 2 Hull 2a Bottom of the ship 3 Propeller 3a Projection plane 3b (Axis of the propeller) 4 Fin 4a Upper surface (of the fin) 4b Front surface (of the fin) 5 Boundary line x Ship width direction y Ship length direction z Vertical direction S1 Range (in the vertical direction) S2 Range (of the parallel part) S3 Range (of the stern part) B Ship hull width L Spacing (between fins) FP Forward perpendicular AP Aft perpendicular Lpp Length between perpendiculars of the ship CL Center line of the hull d1 Ship form data d2 Shape data d3 Position data d4 Energy saving effect S10 Initial data acquisition step S20 Position data acquisition step S21 Exclusion step S30 Calculation step S40 Storage step S50 Repetition step S60 Decision step Pn Position (of the fin) θ1 Mounting angle θ2 Mounting angle

Claims

1. A vessel including a hull, a propeller installed on the hull, and a pair of fins installed on the underside of the hull, A ship characterized in that a pair of fins are installed in a position such that the entire fins are below the axis of the propeller and above the bottom of the hull, and the distance between the pair of fins is in a range that is less than 50% of the hull width of the hull.

2. 2. The vessel according to claim 1, wherein the pair of fins are installed so that at least a portion of the fins is outside the projection plane of the propeller when viewed from the stern side of the vessel in the longitudinal direction.

3. 3. The ship according to claim 1, wherein the distance between the pair of fins is set in the range of 10% to 30% of the width of the hull.

4. 3. A ship according to claim 1 or 2, wherein the squareness factor is 0.6 or less.

5. 3. The ship according to claim 1 or 2, wherein the range in which the water flow velocity is 30% or less of the ship speed when the fin is not provided is 50% or less of the area of ​​the projected surface of the propeller.

6. A method for determining the positions of a pair of fins to be installed on the underside of a hull, comprising the steps of: an initial data acquisition step of acquiring initial data including hull form data based on the shape of the hull and shape data based on the shape of the fin; a position data acquisition step in which a plurality of pieces of position data indicating the positions of the fins, including a distance between the pair of fins, are prepared in advance, and one piece of the plurality of pieces of position data is acquired; a calculation step of calculating an energy saving effect by performing calculation based on the initial data and the position data; A storage step of storing the energy saving effect, a repeating step of performing the position data acquiring step, the calculation step, and the storage step a plurality of times while changing the position data acquired in the position data acquiring step; The method further comprises, after the repeating step, a determining step of determining one of the position data based on the energy saving effect.

7. 7. The method of claim 6, wherein the position data acquired in the position data acquisition step is in a range where the entire fin is below the axis of a propeller installed on the hull and above the bottom of the hull, and the spacing between a pair of the fins is in a range that is less than 50% of the hull width of the hull.

8. The determination method according to claim 6 or 7, wherein the position data includes a mounting angle that is an inclination of the fin with respect to a ship width direction.

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