A quasi-ellipsoidal bulbous bow and its design method

Abstract

The present invention relates to an ellipsoid-like bulbous bow and a design method thereof. The bulbous bow extends from the #0 station toward the bow of a ship, and has a shape similar to an ellipsoid. The cross-section of the bulbous bow is elliptical, and the cross-section gradually decreases from the #0 station toward the bow of the ship; the length of the bulbous bow extending forward from the #0 station is 3% to 5% of the designed waterline length; the half-width of the bulbous bow #0 station is 12% to 18% of the half-width of the hull; and the distance between the bulbous bow #0 station and the water surface is 15% to 20% of the designed draft. The quasi-ellipsoidal bulbous bow proposed in the present invention adopts relatively simple characteristic parameters to describe the shape of the bulbous bow, and the design and construction process are relatively simple; the quasi-ellipsoidal bulbous bow can generally reduce the drag by at least 3% compared with the scheme without the bulbous bow in the cruising state, and can reduce the drag by more than 5% compared with the scheme without the bulbous bow in the design state, so it can be used to improve the navigation performance of the ship, and has important reference and reference value for the design of the bulbous bow of the ship.

Description

Technical Field

[0001] The invention belongs to the technical field of bulbous bow design of surface ships, and particularly relates to an ellipsoidal bulbous bow and a design method thereof. Background Art

[0002] The line form of the ship's bow has a great influence on the ship's resistance. The bulbous bow has an important value in ship design. If the size, shape, and position of the bulbous bow are reasonably matched with the hull line, it can greatly reduce the total resistance of the hull and help optimize the speed of the ship. Secondly, the bulbous bow of some ships can also meet the layout requirements of sonar. There are many forms of bulbous noses, and the more commonly used ones are teardrop-shaped, cylindrical, and "SV" shapes.

[0003] At present, domestic ships widely use bulbous bows such as teardrop-shaped, cylindrical and "SV"-shaped. These bulbous bows can improve the speed of ships to a certain extent, but the characteristic parameters describing the bulbous bow are relatively complex, and the design and construction process is quite complicated.

[0004] At present, the teardrop-shaped bulbous bow is widely used in domestic ships. This bulbous bow is largely to meet the needs of sonar layout. From the perspective of navigation performance, the bulbous bow increases the resistance of the ship during navigation and affects the speed of the ship to a certain extent. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a quasi-ellipsoidal bulbous bow and a design method thereof in view of the deficiencies in the above-mentioned prior art. The quasi-ellipsoidal bulbous bow adopts relatively simple characteristic parameters to describe the shape of the bulbous bow, which can better improve the speed and movement performance, and can effectively improve the navigation performance of surface ships.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is:

[0007] A quasi-ellipsoidal bulbous bow, the bulbous bow extends from station #0 toward the bow of the ship, and is shaped like an ellipsoid. The cross-section of the bulbous bow is elliptical, and the cross-section gradually decreases from station #0 toward the bow of the ship; the length of the bulbous bow extending forward from station #0 is 3% to 5% of the designed waterline length; the half-width of the bulbous bow station #0 is 12% to 18% of the half-width of the hull; the distance between the bulbous bow station #0 and the water surface is 15% to 20% of the designed draft.

[0008] In the above scheme, the shape of the longitudinal section of the bulbous bow is similar to a half ellipse; the shape of the waterline of the bulbous bow is similar to a half ellipse.

[0009] In the above solution, the bulbous bow and the bow column are transitionally connected in a rounded manner.

[0010] In the above solution, the connecting transition area between the bulbous bow and the bow column is a vertical straight line.

[0011] In the above scheme, the distance between the bulbous bow #0 station and the water surface is not less than 1m.

[0012] In the above scheme, the lines of the bulbous bow are smooth and without sudden changes, and the connection area between the bulbous bow and the main hull also has a smooth transition without sudden changes.

[0013] In the above scheme, the ellipsoidal bulbous bow is suitable for ships with a displacement of more than 10,000 tons.

[0014] In the above scheme, the applicable scope of the quasi-ellipsoidal bulbous bow is: ships with Fourier number within [0.20, 0.32] and box coefficient within [0.50, 0.68].

[0015] Accordingly, the present invention also proposes a design method for the above-mentioned ellipsoidal bulbous bow, comprising the following steps:

[0016] Step 1: Analyze the applicability of the ellipsoidal bulbous bow

[0017] The applicable scope is ships with Fourier number within [0.20, 0.32] and box coefficient within [0.50, 0.68];

[0018] Step 2: Determine the maximum and minimum dimensions of the ellipsoidal bulbous bow

[0019] The maximum size is determined according to the area affected by the anchoring process to avoid interference between the bulbous bow and the anchor; the minimum size is determined according to the internal structure size of the bulbous bow to ensure that the layout requirements of the internal structure are met;

[0020] Step 3: Determine the main parameters of the ellipsoidal bulbous bow

[0021] The main parameters include the length l of the bulbous bow extending forward from the #0 station, the half width b of the bulbous bow #0 station, and the distance d from the bulbous bow #0 station to the water surface; wherein l is 3% to 5% of the design waterline length; b is 12% to 18% of the half width of the hull; and d is 15% to 20% of the design draft;

[0022] Step 4: Design the lines of the ellipsoidal bulbous bow

[0023] Step 4.1: Consider the collision problem between the bulbous bow and the anchor. The design optimization of the bulbous bow should be carried out under the constraint of not changing the shape above the waterline as much as possible to avoid interference between the bulbous bow and the anchor.

[0024] Step 4.2, the bulbous bow line form is: the cross section line is an ellipse, and the cross section gradually decreases from station #0 to the bow; the shape of the longitudinal section line is similar to a half ellipse; the waterline shape of the bulbous bow is similar to a half ellipse;

[0025] Step 4.3: Make the bulbous bow line smooth.

[0026] In the above scheme, the smoothness of the lines in step 4.3 meets the following requirements: the change trend of the bulbous bow line in the waterline sectioned along the direction of equal height should be uniform, and there should be no mutation; the change trend of the bulbous bow line in the transverse section sectioned along the direction of equal length should be uniform, and there should be no mutation; the change trend of the bulbous bow line in the longitudinal section sectioned along the width direction should be uniform, and there should be no mutation; the connection area between the bulbous bow line and the main hull should have a smooth transition, and there should be no mutation; the bulbous bow cross-sectional area curve should be smooth, and there should be no mutation.

[0027] The beneficial effects of the present invention are:

[0028] The quasi-ellipsoidal bulbous bow proposed in the present invention adopts relatively simple characteristic parameters to describe the shape of the bulbous bow, and the design and construction process are relatively simple; the quasi-ellipsoidal bulbous bow can generally reduce the drag by at least 3% compared with the scheme without the bulbous bow in the cruising state, and can reduce the drag by more than 5% compared with the scheme without the bulbous bow in the design state, so it can be used to improve the navigation performance of the ship, and has important reference and reference value for the design of the bulbous bow of the ship. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0030] Figure 1 It is a schematic diagram of the forward extension length of the ellipsoidal bulbous bow of the present invention and the distance from the water surface;

[0031] Figure 2 Schematic diagram of the half-width of the ellipsoidal bulbous bow of the present invention;

[0032] Figure 3 It is a cross-sectional view of the line scheme of the ellipsoidal bulbous bow of the present invention;

[0033] Figure 4 It is a longitudinal section diagram of the line scheme of the ellipsoidal bulbous bow of the present invention;

[0034] Figure 5 It is a waterline diagram of the line scheme of the ellipsoidal bulbous bow of the present invention;

[0035] Figure 6 It is a schematic diagram of the three-dimensional shape of the ellipsoidal bulbous bow of the present invention;

[0036] Figure 7 It is a schematic diagram of the cross-sectional area curve of the ellipsoidal bulbous bow of the present invention. DETAILED DESCRIPTION

[0037] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0038] The present invention proposes a quasi-ellipsoidal bulbous bow, which extends from the #0 station toward the bow direction, and is shaped like an ellipsoid. The main design parameters of the quasi-ellipsoidal bulbous bow include the length l of the bulbous bow extending forward from the #0 station, the half width b of the bulbous bow #0 station, and the distance d from the bulbous bow #0 station to the water surface, which can be seen in Figure 1-2 Since the cross-section of the ellipsoidal bulbous bow generally decreases gradually from station #0 forward, the specific shape of the bulbous bow can generally be determined based on the above parameters.

[0039] The center of the quasi-ellipsoidal bulbous bow is approximately halfway along the centerline of the ellipsoid in the height direction. The length l of the bulbous bow extending forward from the #0 station should be determined by comprehensively considering factors such as the bow impact and the total length limit of the ship. The ideal recommended range is 3% to 5% of the design waterline length. At this time, the quasi-ellipsoidal bulbous bow can generally achieve a better drag reduction effect. The half-width b of the bulbous bow #0 station is 12% to 18% of the half-width of the hull. At this time, the quasi-ellipsoidal bulbous bow can generally achieve a better drag reduction effect. When the ratio of the half-width of the bulbous bow to the half-width of the hull is 15%, the drag reduction effect of the quasi-ellipsoidal bulbous bow is better. The distance d between the bulbous bow station #0 and the water surface determines the drag reduction effect of the bulbous bow to a certain extent. The changes in the bulbous bow draft, the influence of factors such as trim, etc. need to be considered in the design. When the distance between the bulbous bow and the water surface is too small, the drag reduction effect of the bulbous bow will become worse. The distance d between the bulbous bow station #0 and the water surface is recommended to be 15% to 20% of the design draft, and the minimum value shall not be less than 1m.

[0040] The following main factors need to be considered in the design of the ellipsoidal bulbous bow profile:

[0041] (1) Maximum and minimum dimensions of a quasi-ellipsoidal bulbous bow

[0042] Since the length and width of the ellipsoidal bulbous bow are large, the anchor at the bow may hit the bulbous bow when dropping anchor. Therefore, the maximum size of the bulbous bow is determined according to the affected area during the dropping anchor process, and the interference between the bulbous bow and the anchor should be avoided. The minimum size of the bulbous bow is determined according to the internal structure size of the bulbous bow to ensure that the layout requirements of the internal structure are met.

[0043] (2) Ellipsoidal bulbous bow line form

[0044] The ellipsoidal bulbous bow line form can be referred to Figure 3 , Figure 4 , Figure 5 The transverse section line can be designed as an ellipse, the shape of the No. 0 middle longitudinal section line of the bulbous bow is similar to a half ellipse, and the waterline shape of the bulbous bow is similar to a half ellipse. At this time, the drag reduction effect of the bulbous bow is better.

[0045] In order to ensure the connection effect between the bulbous bow and the stem, the bulbous bow and the stem are connected by a guide circle. The size of the guide circle should be determined according to the structural requirements and should not be too small. The connection transition area between the bulbous bow and the stem is a vertical straight line to minimize the inflow angle in the direction of the stem.

[0046] (3) Ellipsoidal bulbous bow line is smooth

[0047] The smoothness of the bulbous bow line mainly considers the smoothness of the bulbous bow line itself and the smoothness of the connection area between the bulbous bow and the main hull. Generally speaking, the change trend of the bulbous bow line along the waterline of the equal height direction should be relatively uniform, and there should be no sudden changes; the change trend of the bulbous bow line along the transverse section of the equal length direction should be relatively uniform, and there should be no sudden changes; the change trend of the bulbous bow line along the longitudinal section of the width direction should be relatively uniform, and there should be no sudden changes. The connection area between the bulbous bow line and the main hull should also meet the above requirements.

[0048] In addition, the smoothing effect of the bow cross-sectional area is to be checked. Generally speaking, the cross-sectional area curve should be relatively smooth at the bow and should not have abrupt changes. Figure 7 .

[0049] It should be noted that the quasi-ellipsoidal bulbous bow proposed in the present invention is mainly suitable for ships with a displacement of more than 10,000 tons. According to design experience and model test results, the quasi-ellipsoidal bulbous bow scheme can be adopted when the Fourier number is within [0.20, 0.32] and the square coefficient is within [0.50, 0.68]. In general, the quasi-ellipsoidal bulbous bow scheme can reduce the bare hull resistance by more than 3% in the range of Fourier number Fr of 0.2 to 0.32 under the design state compared with the main hull scheme without bulbous bow.

[0050] Accordingly, the present invention also proposes a design method for the above-mentioned ellipsoidal bulbous bow, comprising the following steps:

[0051] Step 1: Determine the maximum and minimum dimensions of the ellipsoidal bulbous bow

[0052] The maximum size is determined according to the area affected by the anchoring process to avoid interference between the bulbous bow and the anchor; the minimum size is determined according to the internal structure size of the bulbous bow to ensure that the layout requirements of the internal structure are met;

[0053] Step 2: Analyze the applicability of the ellipsoidal bulbous bow

[0054] The applicable scope is ships with Fourier number within [0.20, 0.32] and box coefficient within [0.50, 0.68];

[0055] Step 3: Determine the main parameters of the ellipsoidal bulbous bow

[0056] The main parameters include the length l of the bulbous bow extending forward from the #0 station, the half-width b of the bulbous bow, and the distance d from the #0 station of the bulbous bow to the water surface; among them, l is 3% to 5% of the design waterline length; b is 12% to 18% of the half-width of the hull; d is 15% to 20% of the design draft;

[0057] Step 4: Design the lines of the ellipsoidal bulbous bow

[0058] Step 4.1: Consider the collision problem between the bulbous bow and the anchor. The design optimization of the bulbous bow should be carried out under the constraint of not changing the shape above the waterline as much as possible to avoid interference between the bulbous bow and the anchor.

[0059] Step 4.2: The bulbous bow line is in the form of: the transverse section line is an ellipse, and the cross section gradually decreases from station #0 to the bow; the longitudinal section line is similar to a half ellipse;

[0060] Step 4.3: Make the bulbous bow line smooth.

[0061] The following takes a certain type of surface ship as a specific research object to illustrate the ellipsoidal bulbous bow and design method thereof proposed by the present invention.

[0062] (1) Determination of the minimum and maximum dimensions of the bulbous bow

[0063] It is known that equipment needs to be installed inside the bulbous bow, and the minimum size of the equipment is 2m. Combined with structural factors, the minimum half-width of the bulbous bow should be greater than 1.25m; considering the anchoring factor, the maximum half-width should not be greater than 3m.

[0064] (2) Analysis of applicability of bulbous bow

[0065] According to the existing design, the draft of the ship is 10m, and the distance between the bulbous bow and the water surface is relatively large, so the bulbous bow will not easily come out of the water. The square coefficient is 0.61, and the design Fourier number is 0.28, both of which are within the design parameter range allowed by the quasi-ellipsoidal bulbous bow scheme. This shows that the quasi-ellipsoidal bulbous bow scheme is suitable for this type of ship.

[0066] (3) Determination of main parameters of bulbous bow

[0067] According to the minimum and maximum sizes of the bulbous bow, a rough cross-section of the bulbous bow is drawn. Combined with the width of the main hull of 38m, it is determined that the optimal half-width of the bulbous bow with drag reduction effect is about 2.85mm, the distance between the top of the bulbous bow and the water surface is 1.5m, and the forward extension length of the bulbous bow is about 12m. At this time, all parameters are within the recommended range of the ellipsoidal bulbous bow.

[0068] (4) Bulbous bow line design

[0069] (I) Collision between bulbous bow and anchor

[0070] Since the position where the anchor is placed on the bow line of the main hull is close to the midship, it is necessary to avoid interference between the bulbous bow and the anchor as much as possible. The design optimization of the bulbous bow should be carried out under the constraint of not changing the shape above the waterline as much as possible.

[0071] (II) Bulbous bow line form

[0072] The cross section of the ellipsoidal bulbous bow is an ellipse, and the longitudinal section of the bulbous bow is an ellipse. For the specific three-dimensional shape, see Figure 6 .

[0073] (III) Smoothness of bulbous bow line

[0074] Carry out the smoothing of the bulbous bow line, and the smoothing effect is achieved Figure 3 , Figure 4 , Figure 5 The level in.

[0075] (5) Bulbous bow model test

[0076] Model tests were conducted based on the finalized bulbous bow profile, and the results were compared with those of the model test without a bulbous bow to determine the drag reduction effect of the ellipsoidal bulbous bow scheme. The model test results show that under normal circumstances, the drag reduction should be at least 3% compared with the scheme without a bulbous bow in cruising conditions, and the drag reduction should be more than 5% compared with the scheme without a bulbous bow in design conditions.

[0077] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A quasi-ellipsoidal bulbous bow, characterized in that: The bulbous bow extends from the #0 station toward the bow, and its shape is similar to an ellipsoid. The cross-section of the bulbous bow is an ellipse, and the cross-section gradually decreases from the #0 station toward the bow; the length of the bulbous bow extending forward from the #0 station is 3% to 5% of the designed waterline length; the half-width of the bulbous bow #0 station is 12% to 18% of the half-width of the hull; the distance between the bulbous bow #0 station and the water surface is 15% to 20% of the designed draft; the shape of the longitudinal section of the bulbous bow is similar to half an ellipse; the waterline shape of the bulbous bow is similar to half an ellipse; the distance between the bulbous bow #0 station and the water surface is not less than 1m; the quasi-ellipsoidal bulbous bow is suitable for ships with a displacement of more than 10,000 tons; the applicable scope of the quasi-ellipsoidal bulbous bow is: ships with Fourier numbers within [0.20, 0.32] and square coefficients within [0.50, 0.68].

2. The ellipsoidal bulbous bow according to claim 1, characterized in that: The bulbous bow and the bow column are transitionally connected in a rounding manner.

3. The ellipsoidal bulbous bow according to claim 2, characterized in that: The connecting transition area between the bulbous bow and the bow column is a vertical straight line.

4. The ellipsoidal bulbous bow according to claim 1, characterized in that: The lines of the bulbous bow are smooth without sudden changes, and the connection area between the bulbous bow and the main hull also has a smooth transition without sudden changes.

5. The design method of the ellipsoidal bulbous bow according to claim 1, characterized in that: The following steps are involved: Step 1: Analyze the applicability of the ellipsoidal bulbous bow The applicable scope is ships with Fourier number within [0.20, 0.32] and box coefficient within [0.50, 0.68]; Step 2: Determine the maximum and minimum dimensions of the ellipsoidal bulbous bow The maximum size is determined according to the area affected by the anchoring process to avoid interference between the bulbous bow and the anchor; the minimum size is determined according to the internal structure size of the bulbous bow to ensure that the layout requirements of the internal structure are met; Step 3: Determine the main parameters of the ellipsoidal bulbous bow The main parameters include the length of the bulbous bow extending forward from station #0 l 、Half width of bulbous bow #0 station b 、Bullish bow #0 station distance from water surface d ; in, l 3%~5% of the designed waterline length; b 12%~18% of the half width of the hull; d 15%~20% of the design draft; Step 4: Design the lines of the ellipsoidal bulbous bow Step 4.1: Consider the collision problem between the bulbous bow and the anchor. The design optimization of the bulbous bow should be carried out under the constraint of not changing the shape above the waterline as much as possible to avoid interference between the bulbous bow and the anchor. Step 4.2, the bulbous bow line form is: the cross section line is an ellipse, and the cross section gradually decreases from station #0 to the bow; the shape of the longitudinal section line is similar to a half ellipse; the waterline shape of the bulbous bow is similar to a half ellipse; Step 4.3: Make the bulbous bow line smooth.

6. The design method of the ellipsoidal bulbous bow according to claim 5 is characterized in that: The smoothness of the lines in step 4.3 shall meet the following requirements: the change trend of the bulbous bow line in the waterline along the direction of equal height shall be uniform, without any sudden change; the change trend of the bulbous bow line in the transverse section along the direction of equal length shall be uniform, without any sudden change; the change trend of the bulbous bow line in the longitudinal section along the width direction shall be uniform, without any sudden change; the connection area between the bulbous bow line and the main hull shall have a smooth transition, without any sudden change; the cross-sectional area curve of the bulbous bow shall be smooth, without any sudden change.

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