Method for determining the installation position of a transom skeg

Abstract

The application provides a determination method of bilge keel installation position, which determines the installation position of the middle bilge keel, simulates the streamline distribution of the ship by using CFD technology, obtains the streamline of the installation position of the middle bilge keel, and further obtains the installation position of the bilge keel on other ship stations, which is convenient and fast, does not need to determine a separate test period, is not limited by time and space, can be carried out synchronously after the determination of the ship line scheme, provides input for the ship structure design, significantly shortens the ship design cycle, saves the design cost, and improves the ship design efficiency; does not need to use oil film or paint to coat the surface of the ship model, avoids the damage to the surface of the ship model, and avoids the influence on the results of the later test of the propeller and energy-saving device, and improves the ship design precision; the method can be applied to all steel ships, and has wide popularization and use value.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding, and in particular to a method for determining the installation position of a bilge keel. Background Technology

[0002] Excessive rolling of a ship in rough seas can have a series of adverse effects on its operational performance. Therefore, modern ships are generally equipped with roll damping devices, and the bilge keel is one of the most common passive roll damping devices. The bilge keel is a longitudinal member installed at the junction of the side and bottom of the ship. There are two types: continuous and intermittent. Its main function is to increase the damping of the ship during rolling and reduce the degree of rolling.

[0003] The installation position of the bilge keel on the hull surface is usually determined by streamline tests during ship model trials. To determine the bilge keel position using streamline tests, an oil film or paint needs to be applied to the ship model surface before the test. After being washed by water, the flow lines indicate the direction of the water flow, and the direction of the streamlines is determined based on the 45-degree angle position of the bilge midships. After the test, the oil film or paint must be thoroughly wiped off to avoid affecting the accuracy of subsequent tests on propellers, energy-saving devices, etc. Furthermore, streamline tests require a separate scheduled testing period, which inevitably impacts the design cycle and cost, causing inconvenience to the smooth progress of structural design.

[0004] In summary, this invention not only addresses the issue that streamlined testing may damage the surface of the ship model during the determination of the bilge keel installation position, thereby affecting the accuracy of subsequent ship model tests, but also considers the impact of streamlined testing on design cycle and cost. This invention provides a method for determining the bilge keel installation position. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for determining the installation position of the bilge keel, which solves the problems of long design cycle, high cost and impact on the accuracy of subsequent ship model tests caused by applying oil film or paint in the prior art.

[0006] To achieve the above and other related objectives, the present invention provides a method for determining the installation position of a bilge keel, the method comprising at least the following steps:

[0007] Establish a geometric model of the entire ship to determine the installation position of the bilge keel.

[0008] Numerical simulation was used to calculate the ship's resistance and obtain a streamline distribution diagram of the entire ship.

[0009] The streamlines obtained from the overall ship streamline distribution diagram are those passing through the midship bilge keel installation location.

[0010] Determine the installation positions of the bilge keels at each station on the vessel.

[0011] Preferably, determining the installation position of the center bilge keel specifically comprises the following steps: drawing a bottom profile line extending to the side direction and a side profile line extending to the bottom plate at the center bilge; and rotating the bottom profile line 45 degrees clockwise through the intersection of the bottom profile line and the side profile line, and the intersection of the bottom profile line and the center bilge is the installation position of the center bilge keel.

[0012] Preferably, the calculation grid of the numerical simulation comprises one or a combination of a structured grid and an unstructured grid.

[0013] Preferably, the calculation grid on the surface of the ship is a boundary layer grid, and the calculation grid needs to be locally encrypted at the junction area of the ship and the free surface.

[0014] Preferably, the numerical simulation releases the two degrees of freedom of trim and heave.

[0015] Preferably, the turbulence model of the numerical simulation adopts one of an SST k-ω model and a Realizable k-ε model.

[0016] Preferably, the time step of the numerical simulation is L / (V*200), wherein L is the length between perpendiculars, and V is the speed.

[0017] Preferably, obtaining the streamline through the installation position of the center bilge keel specifically comprises the following steps: 1) establishing a threshold component in the derived component, selecting the ship as the component, selecting the air volume fraction as the scalar field, selecting [0.5, 0.5] as the range, and selecting less than the minimum value as the mode; 2) establishing a plane cross-section component in the derived component, selecting [X0, 0, 0] as the origin, wherein X0 is the X-direction coordinate value of the installation position of the center bilge keel, selecting [1, 0, 0] as the normal, and selecting the threshold component in 1) as the component; 3) establishing an isosurface component in the derived component, selecting the plane cross-section component in 2) as the component, and selecting the position [Z0] as the scalar field, wherein Z0 is the Z-direction coordinate value of the installation position of the center bilge keel; 4) establishing a constrained streamline component in the derived component, selecting the ship as the component, selecting the grid relative rate as the vector field, selecting the second-order RK algorithm as the integral solver, selecting the isosurface component in 3) as the source seed, and selecting one of the front side, the back side, or both as the integral direction of the second-order integrator to obtain the streamline through the installation position of the center bilge keel.

[0018] Preferably, the method for determining the bilge keel installation position comprises the following steps: 1) establishing a new plane section part in the derived part, the origin is selected as [0, 0, 0], the normal is selected as [1, 0, 0], the part is selected as the ship body, the section mode is selected as multi-section, the section number is selected as M, the section range is set according to the integral direction of the second-order integrator, and M station positions and station transverse lines of the ship body are obtained; 2) establishing a new scalar scene in the scene, and creating a geometric display and a flow line display, wherein the part of the geometric display is selected as the ship body and the station position derived part in the step 1, and the part of the flow line display is selected as the flow line derived part of the bilge keel installation position point; and 3) measuring the intersection Z coordinate value of the flow line of the bilge keel installation position point and the station transverse line, and obtaining the installation height of the bilge keel at the station position.

[0019] Preferably, when the integral direction of the second-order integrator is selected as both, the section range is from X=0 to L, L is the length between perpendiculars; when the integral direction of the second-order integrator is selected as the back side, the section range is from X=0 to X0; and when the integral direction of the second-order integrator is selected as the front side, the section range is from X=X0 to L.

[0020] As described above, the method for determining the bilge keel installation position has the following beneficial effects: the bilge keel installation position is determined first, the flow line distribution of the ship body is simulated by using the CFD technology, the flow line of the bilge keel installation position point is obtained, and the installation position of the bilge keel at other station positions of the ship body is further obtained, which is convenient and fast, does not need to reserve a separate test period, is not limited by time and space, can be carried out synchronously after the ship line scheme is determined, provides input for the ship structure design, significantly shortens the ship design cycle, saves the design cost, and improves the ship design efficiency; the surface of the ship model does not need to be coated with oil film or paint, which avoids the damage to the surface of the ship model and the influence on the results of the later test of the propeller and energy-saving device, and improves the ship design precision; the method can be applied to all steel ships, and has wide popularization and application value. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A flow chart of the method for determining the bilge keel installation position is shown.

[0022] Figure 2 A transverse cross-sectional view of the bilge keel installation position in the embodiment of the present application is shown.

[0023] Figure 3 A full-ship flow line distribution diagram of the CFD numerical simulation in the embodiment of the present application is shown.

[0024] Figure 4 A structural schematic view of the bilge keel installation position in the embodiment of the present application is shown.

[0025] Component designation explanation

[0026] 110 bottom plate

[0027] 111 Bottom section line

[0028] 120 Side

[0029] 121 Side Section

[0030] 130 Midships bilge

[0031] 200. Installation position of the midship bilge keel.

[0032] Streamline of the 300-degree hull line at the bilge keel installation point.

[0033] 400-station cross section Detailed Implementation

[0034] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] In the detailed description of embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0036] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the accompanying drawings for devices in use or operation.

[0037] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] like Figure 1 As shown, the present invention provides a method for determining the installation position of a bilge keel, the method comprising at least:

[0039] establish a whole ship geometric model to determine the installation position 200 of the center bilge keel;

[0040] numerical simulation method is adopted to carry out the resistance calculation of the ship, and a full ship streamline distribution map is obtained;

[0041] obtain the streamline 300 passing through the installation position of the center bilge keel in the full ship streamline distribution map;

[0042] determine the installation position of the bilge keel at each station of the ship.

[0043] Specifically, in order to facilitate description, the coordinate system of the present application is defined as follows: the origin is the intersection point of the stern vertical line and the reference line, the longitudinal X direction is the ship length direction and is positive towards the bow direction, the transverse Y direction is the ship width direction and is positive towards the port side direction of the ship, and the vertical Z direction is positive towards the deck direction. A whole ship geometric model is established, such as Figure 2 , at the center bilge portion 130 corresponding to the ship longitudinal centerline, a ship bottom profile line 111 extending towards the side 120 is drawn, and a side profile line 121 extending towards the ship bottom plate 110 is drawn; the ship bottom profile line 111 is rotated clockwise by 45° through the intersection point of the ship bottom profile line 111 and the side profile line 121, and the intersection position of the rotated ship bottom profile line 111 and the center bilge portion 130 is the installation position 200 of the center bilge keel, and the coordinate values [X0, Y0, Z0] of the point are measured.

[0044] The whole ship geometric model is imported into CFD software, numerical simulation method is adopted to carry out the resistance calculation of the ship, and the calculation condition is selected as the design draft and the design speed. The whole ship geometric model can adopt a scale-down or a full scale, but should include the ship appendages or openings affecting the flow field characteristics, and does not include the bilge keel. The calculation region should be large enough to eliminate the influence of the boundary on the calculation results, such as extending at least 2.0L from the stern, and extending at least 1L from both sides, wherein L is the vertical length of the ship, and the specific calculation domain is set according to the actual demand, which is not limited here. The calculation grid can adopt structured grid or unstructured grid, and in the case of large speed, the overlap grid of structured grid and unstructured grid is needed. The boundary layer grid is needed on the ship surface, and the grid needs to be locally encrypted near the ship and free surface junction in the areas where the flow field changes greatly. In order to keep consistent with the actual operating state, the two degrees of freedom of trim and heave need to be released during numerical simulation calculation. The turbulence model can adopt two equation models such as SST k-ω and Realizable k-ε. The calculation time step can be taken as L / (V*200), wherein L is the vertical length of the ship, and V is the speed, and the calculation time is not less than 100s. In order to ensure the reliability of the calculation results, the convergence criterion needs to be defined and checked, such as the fluctuation rate of resistance, residual error, etc. After the calculation is completed, the full ship streamline distribution map such as Figure 3 is obtained.

[0045] According to the full-ship streamline distribution map, the following steps are applied by using CFD numerical simulation software StarCCM+ to obtain the streamline of the passing ship center bilge keel installation position point:

[0046] 1) A threshold part is established in the derived parts, the attribute is that the part is selected as the ship body, the scalar field is selected as the volume fraction of air, the range is selected as [0.5, 0.5], which represents the ship water interface, and the mode is selected as less than the minimum value;

[0047] 2) A plane cross-section part is established in the derived parts, the attribute is that the coordinates [X0, 0, 0] of the origin are input, wherein the X0 coordinate is the X-direction coordinate value of the ship center bilge keel installation position 200, the normal is selected as [1, 0, 0], which represents the transverse section, and the part is selected as the threshold part in step 1);

[0048] 3) An isosurface part is established in the derived parts, the part is selected as the plane cross-section part of 2), the scalar field is selected as Position[Z0], wherein Z0 is the Z-direction coordinate value of the ship center bilge keel installation position 200;

[0049] 4) A constrained streamline part is established in the derived parts, the part is selected as the ship body, the seed type is selected as the part, the vector field is selected as the cell relative velocity, the integral solver is selected as the second-order RK algorithm, the source seed is selected as the isosurface part of step 3), the grid point is selected as [N, 1], the second-order integrator integration direction is selected as one of the front side, the back side or both, the initial integration step is selected as 0.5, the maximum transmission is selected as 1000, and the maximum step number is selected as 2000, so that the streamline 300 of the passing ship center bilge keel installation position point is obtained.

[0050] Wherein the initial integral step length is selected as 0.5, the maximum transmission is selected as 1000, and the maximum step number is selected as 2000, which is an empirical value for controlling the smoothness of the streamline and can be adjusted and modified according to actual requirements. In an embodiment, N is 20, and the integral direction of the second-order integrator is selected as both, that is, the streamline 300 passing through the keel installation position 200 is obtained by connecting 10 grid points towards the bow and 10 grid points towards the stern. Of course, according to actual ship requirements, the grid point N can be selected as other values, and the integral direction of the second-order integrator can be selected as one of the front side or the rear side, that is, only the streamline 300 passing through the keel installation position 200 on one side of the keel installation position 200 is solved, which is not limited here.

[0051] Continue to apply the CFD numerical simulation software StarCCM+ to operate the following steps to obtain the keel installation positions at each station of the ship:

[0052] 1) A new plane section part (Plane) is established in the derived part (Derived Parts), the origin is selected as [0, 0, 0], the normal is selected as [1, 0, 0], the part is selected as the ship body, the section mode is selected as multi-section, the section number is selected as M, and the section range is set according to the integral direction of the second-order integrator, so that M station positions and station transverse lines 400 of the ship body surface are obtained. Wherein, when the integral direction of the second-order integrator is both, the section range is from X=0 to L, L is the length of the ship body perpendicular to the line; when the integral direction of the second-order integrator is the rear side, the section range is from X=0 to X0, X0 is also the X coordinate value of the keel installation position 200; when the integral direction of the second-order integrator is the front side, the section range is from X=X0 to L;

[0053] Specifically, in an embodiment, M is 21, the integral direction of the second-order integrator is both, and the section range is from X=0 to L, so that the 0-20 station transverse sections of the keel and the keels on both sides thereof are obtained, and the intersection lines of the station transverse sections and the ship body surface are the 20 station transverse lines 400 of the positions to be determined. The above example is a non-limiting example, and M can also be set as other values according to requirements, which is not limited here.

[0054] 2) A new scene of a scalar is established in the scene, and a geometric display and a streamline display are respectively created, wherein the part of the geometric display is selected as the ship body and the station derived part in step 1), and the part of the streamline display is selected as the streamline 300 passing through the keel installation position derived part which has been obtained;

[0055] 3) the intersection point Z of the streamline 300 of the midship bilge keel installation position and the station transverse line 400 is measured to obtain the installation height of the bilge keel at each station, thus obtaining the installation position of the bilge keel, as shown in FIG. 3. Figure 4 After obtaining the installation position of the bilge keel at each station, the installation of the bilge keel at some or all of the selected stations can be performed according to requirements.

[0056] In summary, the present application provides a method for determining the installation position of a bilge keel. The installation position of the midship bilge keel is first determined, the streamline distribution of the ship is simulated by using CFD technology, the streamline of the midship bilge keel installation position is obtained, and the installation position of the bilge keel at other stations of the ship is further obtained. The method is convenient and fast, does not require a separate test period, is not limited by time and space, can be carried out simultaneously after the determination of the ship's line plan, provides input for ship structure design, significantly shortens the ship design cycle, saves design cost, and improves ship design efficiency. The method does not require the use of oil film or paint to coat the surface of the ship model, avoids the destruction of the surface of the ship model, and avoids affecting the results of later tests of propellers and energy-saving devices, thereby improving the accuracy of ship design. The method can be applied to all steel ships and has wide application and use value.

[0057] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the present application should be covered by the claims of the present application.

Claims

1. A method of determining a position of a bilge keel installation, characterized in that, The determination method comprises at least the following steps: establishing a whole-ship geometric model to determine the installation position of the center keel; determining the installation position of the center keel comprises the following steps: at the center bilge, drawing a bottom profile line extending to the side direction and a side profile line extending to the bottom plate direction; after rotating the bottom profile line 45 degrees clockwise through the intersection point of the bottom profile line and the side profile line, the intersection position of the bottom profile line and the center bilge is the installation position of the center keel; using a numerical simulation method to carry out ship resistance calculation to obtain a whole-ship streamline distribution map; obtaining a streamline through the installation position of the center keel in the whole-ship streamline distribution map; determining the installation position of the center keel at each station of the ship.

2. The method of determining the mounting position of a skeg according to claim 1, characterized in that: The numerical simulation calculation grid comprises one or a combination of a structured grid and an unstructured grid.

3. The method of determining the mounting position of a skeg according to claim 2, characterized in that: The calculation grid on the surface of the ship is a boundary layer grid, and the calculation grid needs to be locally encrypted at the joint area between the ship and the free surface.

4. The method of determining the mounting position of a skeg according to claim 1, characterized in that: The numerical simulation releases two degrees of freedom of trim and heave.

5. The method of determining the mounting position of a skeg according to claim 1, characterized in that: The numerical simulation adopts one of SST k-ω and Realizable k-ε models as a turbulence model.

6. The method of determining the mounting position of a skeg according to claim 1, characterized in that: The time step of the numerical simulation is L / (V*200), wherein L is the length between perpendiculars, and V is the speed.

7. The method of determining the mounting position of a skeg according to claim 1, wherein The steps of obtaining the streamline through the installation position of the center keel comprise the following steps: 1) establishing a threshold component in the derived component, selecting the ship body as the component, selecting the air volume fraction as the scalar field, selecting the range as [0.5, 0.5], and selecting the mode as less than the minimum value; 2) establishing a plane cross-section component in the derived component, selecting [X0, 0, 0] as the origin, wherein X0 is the X-direction coordinate value of the installation position of the center keel, selecting [1, 0, 0] as the normal, and selecting the threshold component in 1) as the component; 3) establishing an isosurface component in the derived component, selecting the plane cross-section component in 2) as the component, selecting the position [Z0] as the scalar field, wherein Z0 is the Z-direction coordinate value of the installation position of the center keel; 4) establishing a constraint streamline component in the derived component, selecting the ship body as the component, selecting the grid relative rate as the vector field, selecting the second-order RK algorithm as the integral solver, selecting the isosurface component in 3) as the source seed, and selecting one of the front side, the back side, or both as the integral direction of the second-order integrator to obtain the streamline through the installation position of the center keel.

8. The method of determining the mounting position of a skeg according to claim 7, wherein The steps of determining the installation position of the center keel at each station of the ship comprise the following steps: 1) establishing a new plane cross-section component in the derived component, selecting [0, 0, 0] as the origin, selecting [1, 0, 0] as the normal, selecting the ship body as the component, selecting the multi-section as the cross-section mode, selecting M as the cross-section number, and setting the cross-section range corresponding to the integral direction of the second-order integrator to obtain M stations and station transverse lines on the surface of the ship. 2) a new scene of a scalar is established in the scene, and a geometric display and a streamline display are created respectively, wherein the zero parts of the geometric display select the hull and the station derived zero parts in 1), and the zero parts of the streamline display select the streamline derived zero parts of the passing ship's centerboard installation position points; 3) the intersection Z coordinate value of the streamline of the passing ship's centerboard installation position points and the station transverse line is measured to obtain the installation height of the centerboard on the station.

9. The method of determining the mounting position of a skeg according to claim 8, characterized in that: When the integration direction of the second-order integrator is selected as both, the section range is from X=0 to L, L being the length between perpendiculars; when the integration direction of the second-order integrator is selected as the back side, the section range is from X=0 to X0; when the integration direction of the second-order integrator is selected as the front side, the section range is from X=X0 to L.

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