Parametric modeling method for ship hull with bulbous bow and bulbous stern based on grasshopper

Abstract

The application discloses a hull parametric modeling method with bulb bow and bulb stern based on Grasshopper development. The first step is to extract hull lines and other information from a ship type library. The second step is to generate curves, position, sort, project and establish constraint relationships based on non-uniform B-spline curves. The third step is to generate a skin surface according to the defined hull topology structure and the spline curve established in the region. The step-by-step generation method is used to continuously extract the edge line of the generated surface for generating the NURBS surface of the next region. The generation sequence is: bulb bow, bow, bulb stern surface, bulb stern, hull, and hull transition area. The fourth step is to assemble and trim the propeller and rudder. The method solves the problems of low precision, weak hull shape control ability and difficulty in forming a closed surface in the bulb bow and bulb stern regions during the current hull parametric modeling, and the developed hull hydrostatic force analysis method can greatly improve the design efficiency.

Description

Technical Field

[0001] This invention relates to the field of parametric modeling technology, and in particular to a parametric modeling method for ship hulls with bulbous bows and sterns based on Grasshopper. Background Technology

[0002] Ships are one of the world's mainstream modes of transportation today, and a ship with excellent hull lines can greatly reduce transportation costs and improve navigation performance. To improve hull performance, numerous hull-related structures have been developed, such as bulbous bows, bulbous sterns, and bilge keels.

[0003] With the development of computer technology, computer-aided modeling and simulation-driven hull optimization design have been widely applied to hull design. Automatic curve and surface generation technology can be used for ship hydrodynamic analysis and hull performance calculation. Furthermore, this technology is a key technology for multidisciplinary hull optimization design.

[0004] In the field of parametric hull modeling, how to obtain a hull shape that is both freely transformable and highly smooth while inheriting the excellent performance of the parent ship has always been a challenging problem. This is especially true for complex hulls with bulbous bows and sterns, where accurate parametric modeling and adjustment are particularly difficult. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a parametric modeling method for ship hulls with bulbous bows and sterns based on Grasshopper, realizing parametric modeling of the hull. After inputting a series of hull shape parameters, the hull shape and surfaces can be automatically generated. By modifying the hull shape parameters, any hull that meets the requirements can be obtained. This avoids a large amount of repetitive modeling performed by engineers during propagation design, shortens the hull modeling time, and lays the foundation for ship hydrodynamic optimization.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a parametric modeling method for ship hulls with bulbous bow and stern developed based on Grasshopper, the specific steps of which are as follows:

[0007] (1) Using any ship as the original model, draw or extract the hull section lines and feature curves from the ship type database, and import them into Grasshopper.

[0008] (2) Input a series of parameters to control the shape of the hull;

[0009] (3) Based on the re-divided topology of the hull, the hull profile lines and feature curves are grouped, sorted and projected for positioning, and constraint relationships between curves are established; among them, the profile lines used by each surface are divided into a group, and the spacing between curves is allocated by the input parameters; within each group, the curves are sorted according to the coordinates of their center points.

[0010] (4) Based on the nth-order non-uniform rational B-spline curve and NURBS surface, generate the hull surface; use the curves sorted and grouped in step two to generate the skin surface; first generate the bulbous bow of the hull, then generate the bow and stern, then generate the midsection of the hull, and finally generate the surface of the hull transition area.

[0011] (5) Extract the aforementioned hull structure edge lines, generate the stern sealing plate and hull deck, and seal the propeller area;

[0012] (6) Assemble the generated propeller and rudder with the hull.

[0013] In a preferred embodiment: the parameters input for controlling the hull shape in step 2 include: global parameters, local parameters, bulbous bow parameters, and midship parameters; the global parameters include waterline length, beam, and depth; the bulbous bow parameters include bulbous bow length, bulbous bow height, and bulbous bow centerline; the midship parameters include parallel midbody length and blending coefficient.

[0014] In a preferred embodiment: the input curve is smoothed using the Simplify Curve command to generate a smoother hull.

[0015] In a preferred embodiment: for the curve sorting, grouping and positioning in step (3), the curve sorting method is to extract the midpoint of the curve, analyze the coordinates of the midpoint of the curve, and sort the curves based on the X, Y, Z values ​​of the coordinates. The curve positioning method is to automatically calculate the position of the curve based on the reference position and with the help of the input parameters, and move each curve to the corresponding position. The curve grouping method is to calculate the position of each surface and the coordinates of the midpoint of the curve according to the topology of the ship, and group the curves in each region into a group.

[0016] In a preferred embodiment: for the parameterization generation of the bulbous bow in step (4), a series of section lines L2 parallel to the midship section are used to divide L2 into two groups, L 2a With L 2b L 2a For the bulbous bow protrusion area, L 2b For the region aft of its bulbous bow; first, calculate the closed section line L used for the bulbous bow. 2aThe center point P2 is obtained by fitting a NURBS curve to the bulbous bow centerline l2. Then, based on the input bulbous bow parameters, affine transformations are performed on each point on the bulbous bow centerline to obtain the new bulbous bow profile centerline P'2. Next, a vector is established between P2 and P'2, and this vector is used to move the corresponding bulbous bow profile line to obtain the deformed bulbous bow profile line L'. 2a Next, extract the first section line at the front of the bulbous bow. Calculate its intersection with the plane of symmetry of the hull. Using these two intersection points as endpoints, input the catenary length to generate the catenary. Used to control the shape of the bulbous bow tip; finally, all L' 2a With L 2b Combined into a unified group, and using NURBS surface generation technology, a skinned surface, namely surface S2, is generated; P represents a set of points, p represents a point, L represents a set of lines, l represents a curve, s represents a surface, and C represents a coefficient.

[0017] In a preferred embodiment: for the parameterization generation of the hull bow described in step (4), the edge lines of surface S2 are first extracted. It is then added to curve group L1, and a series of profile lines parallel to the waterline are used to generate the bow surface S1; surfaces S1 and S2 are then joined together using a join surface method to form the bow S1. b .

[0018] In a preferred embodiment: for the stern curved surface of the hull described in step (4), a stepwise generation method is adopted, with the generation sequence being S5, S7, S8, and S6; wherein S5 is generated using a section line parallel to the waterline; the edge line of S5 is extracted. Then, it is added to L6; S7 is generated using curves parallel to the mid-station surface; L8 contains both open and closed curves, so the closed curves need to be split and a new NURBS surface S8 needs to be generated; finally, surfaces S7 and S8 are joined using a join surface; the edges of S7 and S8 are extracted and added to the curve set L6, and a series of profile lines parallel to the waterline are used to generate the NURBS surface S6, finally obtaining the closed stern S. s .

[0019] In a preferred embodiment: the mid-hull surface S9 is parametrically generated as described in step (4); the two ships to be merged are denoted as a and b. For hull a, its surface S9 is extracted from the ship type library. 9a The section line L on 9a The profile lines are parallel to the midship section of the hull. Then, at the corresponding positions, the profile lines L of hull b are extracted. 9bFor each position, the two curves l 9a , l 9b And custom curves l 9c Apply two fusion coefficients C bc And C3, using C bc For L 9b and L 9c The fusion process yields a set of fused profile lines L. 9d Subsequently, C3 was used on L 9d and L 9a The fusion process is performed to obtain the section line L9 of the final hull surface S9. Finally, L9 is used to generate the skin surface S9.

[0020] For the parametric generation of the hull transition region surface described in step (4), the bow S is extracted. b edge line S9 edge of the midship curved surface The bow transition area skin surface S3 is generated using these two curves as boundaries, and the stern S is extracted. s edge line The midship curved surface S9 is located near the stern edge. The bow transition area skin surface S4 is generated using these two curves as boundaries.

[0021] In a preferred embodiment: for the deck surface S for closing the hull generated in step (5) 12 Stern sealing plate surface S 10 Plane S at the propeller 11 The method is as follows: after stitching all the aforementioned curved surfaces into a seamless hull surface, extract the edge lines of the curved surfaces and generate a plane at their respective positions for hull closure.

[0022] In a preferred embodiment: For the parametric adjustment of the propeller and hull coordination described in step (6), the generated propeller and rudder are imported into Grasshopper, and then the two are first positioned; for the propeller: using the center of the propeller hub and plane S 11 Center alignment, then adjust the propeller and S 11 The spacing adjustment determines the coordination between the two; for the rudder, after inputting the relative position of the rudder blade and the hull, the stern S-shaped adjustment is required. s Reconstruction and repair of the rudder blades to avoid surface intersections; calculation of the rudder and stern curvature S. s The intersection line is used to cut S. s Then, the propeller and rudder are joined together to achieve the desired coordination.

[0023] Compared with existing technologies, this invention has the following advantages: This invention achieves corresponding hull shapes by modifying hull parameters, especially realizing high-quality and accurate modeling of complex hull areas (bulbulb and stern). In parametric hull modeling, this method outperforms existing commercial modeling software such as SolidWorks and CAESES. This parametric modeling method combines fully parametric and semi-parametric hull modeling methods, resulting in a hull that inherits the excellent performance of the parent ship while possessing greater optimization space than traditional semi-parametric modeling methods. This invention adjusts the shape and range of the bulbous bow centerline, thereby adjusting the shape and position of the bulbous bow to obtain a wide variety of bulbous bow shapes. This invention further expands the optimization space of the bulbous bow by controlling the catenary length and adjusting the tip shape of the bulbous bow. This invention can quickly and automatically generate and obtain a complete planing surface with good smoothness by inputting the hull's external parameters. This invention utilizes a hull fusion method to generate smooth curved surfaces in the midsection of the hull, thus inheriting the superior performance of the parent ship. The invention employs a step-by-step generation approach, extracting the edges of previously generated surfaces to create the next surface, ensuring continuity between surface patches and thus guaranteeing the hull's airtightness. This invention uses vector control to manage the assembly positions of the propeller, rudder, and hull, and cuts overlapping and intersecting surfaces, significantly improving modeling efficiency when studying propeller-rudder coordination. It automatically generates planing surface curves, avoiding repetitive modeling for engineers during ship design and laying the foundation for optimized hydrodynamic design of ships. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the overall workflow of a preferred embodiment of the present invention;

[0025] Figure 2 The topology of the hull in a preferred embodiment of the present invention is shown in (a) for the overall topology, (b) for the stern topology, (c) for the bow topology, and (d) for the stern surface.

[0026] Figure 3 This is a cross-sectional view of the bow portion of a preferred embodiment of the present invention.

[0027] Figure 4 This is a centerline view of the bulbous bow of a preferred embodiment of the present invention;

[0028] Figure 5 This is a program diagram of the bulbous bow control module according to a preferred embodiment of the present invention;

[0029] Figure 6 The hull midsection lines diagram (parent hull lines, automatically generated lines, final lines) is a preferred embodiment of the present invention.

[0030] Figure 7 The preferred embodiment of the present invention uses a cross-sectional line as an example to demonstrate the transition effect of the curve;

[0031] Figure 8 This is a program diagram of the ship type fusion module according to a preferred embodiment of the present invention;

[0032] Figure 9 The following are cross-sectional views of various regions of the stern of the ship according to a preferred embodiment of the present invention, wherein (a) is a side view of the stern cross-section and (b) is a two-point perspective view of the stern cross-section.

[0033] Figure 10 This is a stern surface diagram generated according to a preferred embodiment of the present invention;

[0034] Figure 11 The above is a lofted surface view of the entire hull of a preferred embodiment of the present invention, wherein (a) is a hull engineering drawing and (b) is a lofted surface view of the hull;

[0035] Figure 12 The lofted surface diagrams of the stern and rudder before and after cutting are shown in a preferred embodiment of the present invention.

[0036] Figure 13 Here are the lofted surface diagrams of the rudder before and after cutting, according to a preferred embodiment of the present invention:

[0037] Figure 14 This is an assembly effect diagram of the hull, propeller, and rudder of a preferred embodiment of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] A parametric hull modeling method based on Grasshopper, featuring bulbous bow and stern, referenced. Figures 1 to 14 The specific steps are as follows:

[0042] (1) Using any ship as the original model, draw or extract the hull section lines and feature curves from the ship type database, and import them into Grasshopper.

[0043] (2) Input a series of parameters to control the shape of the hull;

[0044] (3) Based on the re-divided topology of the hull, the hull profile lines and feature curves are grouped, sorted and projected for positioning, and constraint relationships between curves are established; among them, the profile lines used by each surface are divided into a group, and the spacing between curves is allocated by the input parameters; within each group, the curves are sorted according to the coordinates of their center points.

[0045] (4) Based on the nth-order non-uniform rational B-spline curve and NURBS surface, generate the hull surface; use the curves sorted and grouped in step two to generate the skin surface; first generate the bulbous bow of the hull, then generate the bow and stern, then generate the midsection of the hull, and finally generate the surface of the hull transition area.

[0046] (5) Extract the aforementioned hull structure edge lines, generate the stern sealing plate and hull deck, and seal the propeller area;

[0047] (6) Assemble the generated propeller and rudder with the hull.

[0048] The parameters input in step 2 for controlling the hull shape include: global parameters, local parameters, bulbous bow parameters, and midships parameters. The global parameters include waterline length, beam, and depth. The bulbous bow parameters include bulbous bow length, bulbous bow height, and bulbous bow centerline. The midships parameters include parallel midbody length and blending coefficient. Specifically, the parameters include:

[0049]

[0050]

[0051] The input curve is smoothed using the Simplify Curve command to generate a smoother hull.

[0052] For the curve sorting, grouping and positioning in step (3), the curve sorting method is to extract the midpoint of the curve, analyze the coordinates of the midpoint of the curve, and sort the curves based on the X, Y and Z values ​​of the coordinates. The curve positioning method is to automatically calculate the position of the curve based on the reference position and with the help of the input parameters, and move each curve to the corresponding position. The curve grouping method is to calculate the position of each surface and the coordinates of the midpoint of the curve according to the topology of the ship, and group the curves in each region into a group.

[0053] For the parameterization generation of the bulbous bow described in step (4), a series of section lines L2 parallel to the midship section are used to divide L2 into two groups, L 2a With L 2b L 2a For the bulbous bow protrusion area, L 2b For the region aft of its bulbous bow; first, calculate the closed section line L used for the bulbous bow. 2a The center point P2 is obtained by fitting a NURBS curve to the bulbous bow centerline l2. Then, based on the input bulbous bow parameters, affine transformations are performed on each point on the bulbous bow centerline to obtain the new bulbous bow profile centerline P'2. Next, a vector is established between P2 and P'2, and this vector is used to move the corresponding bulbous bow profile line to obtain the deformed bulbous bow profile line L'. 2a Next, extract the first section line at the front of the bulbous bow. Calculate its intersection with the plane of symmetry of the hull. Using these two intersection points as endpoints, input the catenary length to generate the catenary. Used to control the shape of the bulbous bow tip; finally, all L' 2a With L 2b Combined into a unified group, and using NURBS surface generation technology, a skinned surface, namely surface S2, is generated; P represents a set of points, p represents a point, L represents a set of lines, l represents a curve, s represents a surface, and C represents a coefficient.

[0054] For the parameterization generation of the hull and bow described in step (4), the edge lines of surface S2 are first extracted. It is then added to curve group L1, and a series of profile lines parallel to the waterline are used to generate the bow surface S1; surfaces S1 and S2 are then joined together using a join surface method to form the bow S1. b .

[0055] For the stern curved surface of the hull described in step (4), a step-by-step generation method is adopted, with the generation sequence being S5, S7, S8, and S6; where S5 is generated using a section line parallel to the waterline; the edge line of S5 is extracted. Then, it is added to L6; S7 is generated using curves parallel to the mid-station surface; L8 contains both open and closed curves, so the closed curves need to be split and a new NURBS surface S8 needs to be generated; finally, surfaces S7 and S8 are joined using a join surface; the edges of S7 and S8 are extracted and added to the curve set L6, and a series of profile lines parallel to the waterline are used to generate the NURBS surface S6, finally obtaining the closed stern S. s .

[0056] For the parameterized generation of the mid-hull surface S9 described in step (4); the two ships to be merged are denoted as a and b. For hull a, its surface S9 is extracted from the ship type library. 9a The section line L on 9a The profile lines are parallel to the midship section of the hull. Then, at the corresponding positions, the profile lines L of hull b are extracted. 9b For each position, the two curves l 9a , l 9b And custom curves l 9c Apply two fusion coefficients C bc And C3, using C bc For L 9b and L 9c The fusion process yields a set of fused profile lines L. 9d Subsequently, C3 was used on L 9d and L 9a The fusion process is performed to obtain the section line L9 of the final hull surface S9. Finally, L9 is used to generate the skin surface S9.

[0057] For the parametric generation of the hull transition region surface described in step (4), the bow S is extracted. b edge line S9 edge of the midship curved surface The bow transition area skin surface S3 is generated using these two curves as boundaries, and the stern S is extracted. s edge line The midship curved surface S9 is located near the stern edge. The bow transition area skin surface S4 is generated using these two curves as boundaries.

[0058] For the deck surface S generated in step (5) for closing the hull 12 Stern sealing plate surface S 10 Plane S at the propeller 11 The method is as follows: after merging all the aforementioned curved surfaces into a seamless hull surface, extract the edge lines of the curved surfaces and generate a plane at their respective positions for hull closure.

[0059] Regarding the parametric adjustment of the propeller and hull coordination described in step (6), this paper imports the generated propeller and rudder into Grasshopper and first positions them; for the propeller: using the center of the propeller hub and plane S 11 Center alignment, then adjust the propeller and S 11 The spacing adjustment determines the relationship between the two; for the rudder, after inputting the relative position of the rudder blade and the hull, the stern S-shaped adjustment is required. s Reconstruction and repair of the rudder blades to avoid surface intersections; calculation of the rudder and stern surface S. s The intersection line is used to cut S.s Then, the propeller and rudder are joined together to achieve the desired coordination.

[0060] Furthermore, the hull profile lines and characteristic curves refer to a series of planes arranged along the length or depth of the ship and the intersection lines with the hull surface, as well as the hull deck edge lines, keel lines, and waterlines.

[0061] Furthermore, the hull profile lines are generated based on non-uniform rational B-spline curves. These curves are generated using B-spline basis functions. A p-th degree NURBS curve is defined as a piecewise rational parametric curve of the following form:

[0062]

[0063] Among them, {P i} represents the sequence of control points (forming a control polygon), {ω i} represents the corresponding weight sequence, {N i,p (u)} is a vector defined at non-periodic, non-uniform nodes. p-th order B-spline basis functions

[0064] The i-th p-th B-spline basis function N i,p (u) is defined as follows:

[0065]

[0066] U = {u0, u1, ..., u} m} is a non-decreasing sequence of real numbers, i.e., u i ≤u i+1 ,i=0,1,…m-1, called u i Let U be a node, and U be the node vector.

[0067] Furthermore, the entire bulbous bow is generated using both section lines and the bulbous bow tip contour line. The bulbous bow tip contour line is generated using a catenary. The two endpoints of the first section line of the bulbous bow are extracted as the catenary endpoints, and the catenary length l is used as a parameter to control its shape. c1 and c2 are parameters related to the starting point. After calculating a, substitute them into the following formula to generate the catenary:

[0068]

[0069] Furthermore, the center points of each profile line are calculated, and an affine transformation is performed to form the new bulbous bow centerline. The transformation functions for the X, Y, and Z directions are as follows:

[0070]

[0071] Where k1, k2, b, and f(x) are all freely variable parameters. f(x) is a Bessel function, controlled by four parameters: the starting point, the ending point, and the slopes of the starting and ending points. After obtaining the new bulbous bow centerline, each bulbous bow profile line is moved to its corresponding position, and the transformed bulbous bow skin surface is generated.

[0072] The determination of n+1 nodes yields the following n-order Bézier curve:

[0073]

[0074] An nth-order Bézier curve generated from n+1 points can be derived from an (n-1)th-order Bézier curve generated from the first n points. n-1 (t|p0,…,p n-1 The (n-1)th order Bézier curve generated by the last n points and the following n points. n-1 (t|p1,…,p n ) We get B n (t|p0,…,p n )=(1-t)B n-1 (t|p0,….p n-1 )+tB n-1 (t|p1,…,p n )

[0075] Furthermore, the midsection of the hull is generated using a hull fusion method, as shown below:

[0076] In the formula, ω is the fusion coefficient and x is the vertex coordinate.

[0077] Furthermore, the hull surface is generated incrementally. The edges of already generated surfaces are extracted and used to generate adjacent surfaces. NURBS surfaces:

[0078] Furthermore, when assembling the ship and propeller, the position of the propeller hub center point is calculated. Using the center point of the propeller hub and the center point of the propeller mounting position at the stern, a displacement vector K is constructed. The propeller is moved using vector K, and by adjusting vector K, the assembly of the ship and propeller is achieved.

[0079] Furthermore, when assembling the ship and rudder, a vector K2 is constructed using the center point of the rudder and the center point of the stern plate. By adjusting K2, the ship and rudder are assembled. After assembly, the intersection line of the ship and rudder is calculated. This intersection line is used to divide the rudder and the window surface, and curves of overlapping surfaces are removed, ultimately achieving the proper coordination between the ship and rudder.

[0080] Furthermore, the non-uniform B-spline surface is generated by structure lines in both the UV and U directions. The p-order NURBS surfaces in the u direction and the q-order NURBS surfaces in the v direction are defined by the following two-parameter piecewise rational functions:

[0081]

[0082] Where {P i,j} forms a bidirectional control grid, {ω i,j} represents the corresponding weight, {N i,p (u)} and {N j,q (v)} are defined on the node vectors respectively. and B-spline basis functions on.

Claims

1. A parametric modeling method for ship hulls with bulbous bows and sterns developed based on Grasshopper, characterized in that, The specific steps are as follows: Step (1) Using any ship as the original model, draw or extract the hull profile lines and feature curves from the ship type database, and import them into Grasshopper; Step (2) Input a series of parameters to control the shape of the hull; Step (3) Based on the re-divided topology of the hull, the hull profile lines and feature curves are grouped, sorted, and projected for positioning, and constraint relationships between the curves are established; among them, the profile lines used for each surface are divided into a group, and the spacing between the curves is allocated by the input parameters; within each group, the curves are sorted according to the coordinates of their center points. Step (4) Generate the hull surface based on the nth order non-uniform rational B-spline curve and NURBS surface; use the curves sorted and grouped in step three to generate the skin surface; first generate the bulbous bow of the hull, then generate the bow and stern, then generate the midsection of the hull, and finally generate the surface of the hull transition area. Step (5) Extract the aforementioned hull structure edge lines, generate the stern sealing plate and hull deck, and seal the propeller area; Step (6) Assemble the generated propeller and rudder to the hull; For the parameterization generation of the bulbous bow of the hull described in step (4), a series of section lines parallel to the midship section of the hull are used. ,Will Divided into two groups, and , This refers to the protruding area of ​​the bulbous bow. For the region aft of the bulbous bow; first calculate the center point of the closed section line used for the bulbous bow. The centerline of the bulbous bow was obtained by fitting the NURBS curve. Then, combining the input bulbous bow parameters, an affine transformation is performed on each point on the centerline of the bulbous bow to obtain the center point of the new bulbous bow profile. Next, establish and The vector between them is used to move the corresponding bulbous bow section line, thus obtaining the deformed bulbous bow section line. Next, extract the first section line at the front of the bulbous bow. Calculate the intersection point of its plane of symmetry with the hull. , Using these two intersection points as endpoints, and inputting the catenary length, generate the catenary. Used to control the shape of the bulbous bow tip; finally, all and Grouping them into a unified group, and using NURBS surface generation technology, skin surfaces are generated, specifically the skin surface of the bulbous bow of the hull. ; Representative point set, Representative point, Representative line set, Representative curve, Represents curved surfaces. Representative coefficient; For the stern surface of the hull in step (4), a step-by-step generation method is adopted, and the generation order is as follows: , , , The curved surface; where Generate using profile lines parallel to the waterline; extract edge line After that, join middle; Generate using a curve parallel to the center station surface; The surface contains both open and closed curves. The closed curves need to be segmented and a new NURBS surface regenerated. Finally, the surface is joined using a joint surface. , Assemble; extract , The edge line is added to the curve set. In this process, a series of profile lines parallel to the waterline are used to generate NURBS surfaces. Finally, a closed stern is obtained. .

2. The parametric modeling method for a ship hull with a bulbous bow and stern based on Grasshopper, as described in claim 1, is characterized in that: The parameters used to control the hull shape input in step (2) include: global parameters, local parameters, bulbous bow parameters, and midship parameters; the global parameters include waterline length, beam, and depth; the bulbous bow parameters include bulbous bow length, bulbous bow height, and bulbous bow centerline; and the midship parameters include parallel midbody length and blending coefficient.

3. The parametric modeling method for a ship hull with a bulbous bow and stern based on Grasshopper, as described in claim 1, is characterized in that: The input curve is smoothed using the Simplify Curve command to generate a smoother hull.

4. The parametric modeling method for a ship hull with a bulbous bow and stern based on Grasshopper, as described in claim 1, is characterized in that: For the curve sorting, grouping and positioning in step (3), the curve sorting method is to extract the midpoint of the curve, analyze the coordinates of the midpoint of the curve, and sort the curves based on the X, Y and Z values ​​of the coordinates. The curve positioning method is to automatically calculate the position of the curve based on the reference position and with the help of the input parameters, and move each curve to the corresponding position. The curve grouping method is to calculate the position of each surface and the coordinates of the midpoint of the curve according to the topology of the ship, and group the curves in each region into a group.

5. The parametric modeling method for a ship hull with a bulbous bow and stern based on Grasshopper, as described in claim 1, is characterized in that: For the parameterization generation of the bow of the hull in step (4), the skin surface of the bulbous bow of the hull is first extracted. the edge line And add curve grouping In the process, a series of cross-sectional lines parallel to the waterline are used to generate the bow surface. ; Using the join surface to connect the bow surface hull bulbous bow skin curved surface Together, they form the bow. .

6. The parametric modeling method for a ship hull with a bulbous bow and stern based on Grasshopper, as described in claim 1, is characterized in that: For the mid-hull curved surface in step (4) Parametric generation; the two ships to be merged are denoted as... and Regarding the hull Extract its surface from the ship type library. The cross-section line on The section line is parallel to the midship section of the hull. Then, at the corresponding position, the hull... Extract its profile lines. For each position, there are two curves. , And custom curves Apply 2 fusion coefficients and ,use right and The fusion process yields a set of fused profile lines. Then, using right and The fusion process yields the final mid-hull curved surface. cross-section Finally, using Generate the mid-hull surface ; For the parametric generation of the hull transition region surface in step (4), the bow is extracted. edge line The curved surface of the middle section of the hull edge line The skin surface of the bow transition area is generated using these two curves as boundaries. Extract the stern edge line The curved surface of the middle section of the hull near the tailline The skin surface of the bow transition area is generated using these two curves as boundaries. .

7. The parametric modeling method for a ship hull with a bulbous bow and stern based on Grasshopper, as described in claim 1, is characterized in that: For the deck surface generated in step (5) for closing the hull Stern sealing plate The plane at the propeller The method is as follows: after stitching all the aforementioned curved surfaces into a seamless hull surface, extract the edge lines of the curved surfaces and generate a plane at their respective positions for hull closure.

8. The parametric modeling method for a ship hull with a bulbous bow and stern based on Grasshopper, as described in claim 1, is characterized in that: For the parametric adjustment of the propeller and hull coordination described in step (6), after importing the generated propeller and rudder into Grasshopper, the two are first positioned; for the propeller: using the center of the propeller hub and the plane Center alignment, then by adjusting the propeller and The spacing needs to be adjusted to ensure proper coordination between the two components; for the rudder, after inputting the relative position of the rudder blade and the hull, the stern needs to be adjusted. Reconstruction and repair of the rudder blades to avoid intersection of curved surfaces; Calculate the rudder and stern surface The intersection line is cut using the intersection line. Then, the propeller and rudder are joined together to achieve the desired coordination.

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