A model-based method for calculating a flooded trim of a ship cabin

Abstract

The application relates to a model-based ship cabin water flooding floating state calculation method, S1, calculating the total weight of a ship after water flooding and the changed center of gravity G1; S2, establishing an initial floating center B, an initial center of gravity G, the center of gravity G1 after water flooding, the intersection B' of the horizontal line through the floating center B and the vertical line through the center of gravity G1, taking a point P on BB', connecting G1P, and making the vertical plane of G1P as a waterline plane WpLp model; S3, determining the WpLp height along the G1P direction according to the △, and obtaining the floating center position Bp under the WpLp based on the model; S4, determining the two-division direction of the P point on BB' according to the change law of the floating center position with the movement of the P point, and starting the iterative calculation; S5, repeating S3 to S4 until the distance between the Bp point and the G1P straight line is less than a given precision, that is, the Bp point is considered to be collinear with the G1P, and the state is considered to be the final equilibrium floating state after the cabin is water flooded. The application takes the final steady-state equilibrium condition as the only constraint condition, has a wide application range, studies the floating center movement law, proposes a convergence criterion, and improves the efficiency and the precision.

Description

Technical Field

[0001] This invention relates to the field of ship digital design technology, specifically to a model-based method for calculating the floating state of a ship's cabin during water ingress. Background Technology

[0002] Currently, traditional methods for calculating the buoyancy of a ship after water ingress into its compartments are primarily based on the initial metastasis assumption. This assumption assumes that the amount of water entering the compartment is small, the angle of tilt after water ingress is small, and the hull rotates around the center of float, thus calculating the tilt angle using initial metastasis calculation methods. However, due to uncertainties such as hull type and water ingress volume, the initial metastasis assumption may not always hold true when a ship tilts after water ingress into its compartments. Clearly, this assumption limits the scope and accuracy of buoyancy calculations for water ingress into compartments. Therefore, developing an accurate method for calculating the buoyancy of a ship after water ingress into its compartments is a problem that urgently needs to be solved. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a model-based method for calculating the floating state of a ship's compartments after flooding, addressing the shortcomings of the existing technology. This method is based on a model and uses the final steady-state equilibrium condition, i.e., the line connecting the center of gravity and the center of buoyancy is perpendicular to the waterline, as the only constraint. It does not rely on the initial stability assumption and has a wide range of applications. At the same time, by studying the motion law of the center of buoyancy, a convergence criterion is proposed. Through bisection iterative calculation, the calculation efficiency and accuracy are greatly improved, enabling rapid prediction of the ship's floating state after the compartments are flooded.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0005] A model-based method for calculating the floating state of a ship's compartments during water ingress includes the following steps:

[0006] S1. Given the location and volume of water entering a compartment, calculate the total weight of the ship after water ingress △ and the changed position of the center of gravity G1;

[0007] S2. Load the ship model. According to the technical plan, establish the initial buoyancy center B, the initial center of gravity G, the center of gravity G1 after entering the water, and the intersection point B' of the horizontal line passing through the buoyancy center B and the vertical line passing through the center of gravity G1 in the model. Then, take any point P on BB', connect G1P, and make the vertical plane of G1P as the waterline surface WpLp model.

[0008] S3. Based on the calculated total weight of the ship after water ingress △, determine the height of the waterline WpLp along the G1P direction using the bisection method, so that the displacement below the waterline WpLp is equal to the total weight of the ship, and obtain the buoyancy center position Bp of the ship part below the waterline WpLp at point P based on the model, and measure the distance d between point Bp and the straight line G1P.

[0009] S4. Based on the changing pattern of the center of buoyancy position with the movement of point P, and according to the position of Bp, determine the direction of the bisection of point P on BB', and start the iterative calculation.

[0010] S5. Repeat steps S3 to S4 until the distance between point Bp and the straight line G1P is less than the given precision, that is, Bp and G1P are considered to be collinear. This state is the final equilibrium floating state after the compartment is flooded.

[0011] In the above scheme, in step S4, the change law of the position of the center of buoyancy with the movement of point P is as follows: when point P moves from stern to bow, the position of the center of buoyancy moves from bow to stern; when point P moves from bow to stern, the position of the center of buoyancy moves from stern to bow.

[0012] In the above scheme, in step S4, the direction of the bisection of point P on BB' is determined based on the position of Bp. Specifically, if Bp is to the right of G1P, point P is placed on BB' and moved to the right; if Bp is to the left of G1P, point P is moved to the left.

[0013] The beneficial effects of this invention are as follows:

[0014] 1. This invention proposes a novel model-based method for calculating the buoyancy state of a ship's compartments after water ingress. Using the final steady-state equilibrium condition—that the line connecting the center of gravity and the center of buoyancy is perpendicular to the waterline—as a constraint, the method achieves high-precision and high-efficiency calculations through iterative convergence. Compared to traditional methods, this invention does not rely on initial stability assumptions, has a wide range of applications, and is theoretically error-free.

[0015] 2. This invention studies the ship's balance conditions, the range and pattern of changes in the center of buoyancy position after the compartment is flooded, and proposes a convergence calculation method to achieve rapid convergence and result calculation.

[0016] 3. This method fully leverages digital capabilities, significantly improving efficiency and accuracy through model-based calculations. It can be used for rapid response and forecasting of ship buoyancy in the event of water ingress into the compartments. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0018] Figure 1 It is the change in the center of buoyancy and center of gravity after the compartment is flooded;

[0019] Figure 2 It refers to the range of changes in the center of buoyancy after the compartment is flooded;

[0020] Figure 3 This describes the pattern of the position of the center of buoyancy changing with the movement of point P.

[0021] Figure 4 It is a calculation model for the floating state of the compartment during water ingress;

[0022] Figure 5 It refers to the positional relationship between Bp and G1P during the iteration process;

[0023] Figure 6 It is the result of iterative convergence. Detailed Implementation

[0024] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0025] This invention proposes a method for calculating the floating state of a ship's compartments after water ingress based on a model. The method uses the final steady-state equilibrium condition, i.e., the line connecting the center of gravity and the center of buoyancy is perpendicular to the waterline, as a constraint condition. Through iterative convergence, the method achieves high-precision and high-efficiency calculation of the results.

[0026] The following analysis uses the longitudinal tilt direction after the compartment is flooded as an example (the same applies to the transverse tilt) to explain the specific principle of the method of this invention:

[0027] When water enters a ship's compartments, it's equivalent to adding weight, causing an increase in the overall weight of the ship and a shift in its center of gravity. Figure 1 For example, in the initial state, the ship's center of gravity is G and the center of buoyancy is B. Assuming that the bow compartment takes on water, the center of gravity moves from G to G1. Due to the forward shift of the center of gravity, the ship's bow heels, and the waterline rotates from the initial state W0L0 to the equilibrium state W1L1. The center of buoyancy in the final equilibrium state is B1.

[0028] (1) Final equilibrium conditions of the ship after flooding of the compartments

[0029] Clearly, when the ship finally reaches equilibrium, the direction of gravity should be collinear with the direction of buoyancy. That is, the line connecting the center of gravity and the center of buoyancy, G1B1, must be perpendicular to the tilted waterline W1L1, i.e., G1B1⊥W1L1. From this, the tilt angle of the waterline at equilibrium can be determined. Furthermore, given the tilt angle of the waterline and the ship's total weight (considering the increased water intake), the draft can be quickly determined based on the model using the bisection method.

[0030] (2) Range of change in the position of the center of buoyancy after the compartment is flooded

[0031] Depend on Figure 1 It can be seen that when the bow compartment takes on water, the center of gravity of the entire ship shifts forward, causing the bow to take on water and the stern to emerge from the water. The center of buoyancy will move towards the bow. That is, when in equilibrium, the center of buoyancy B1 must be on the bow side of the initial center of buoyancy B (right side in the figure).

[0032] like Figure 2 As shown, after the compartment floods, the center of gravity G1 is drawn perpendicular to the initial waterline W0L0, intersecting the horizontal line passing through the initial center of buoyancy B at B'. Assume that after flooding, the center of buoyancy moves longitudinally beyond B', denoted as... Figure 2If we consider the final equilibrium condition of the ship after the water enters the compartment (1), then the waterline W2L2 will be perpendicular to G1B". As shown in the figure, the ship will list at the stern, which contradicts the initial assumption of listing at the bow. Therefore, the range of change of the center of buoyancy after water enters the compartment must be within the angle between G1B and G1B'. Let's take a point P between the line segments BB'. When P moves between BB', there must exist a point P0 such that G1P0 is collinear with G1B1 in the final equilibrium state.

[0033] (3) The variation of the position of the center of buoyancy with the movement of point P after the compartment is flooded

[0034] like Figure 3 As shown, when point P moves from B to B', points P1 and P2 are taken respectively. According to the final equilibrium condition of the ship after the cabin is flooded (1), the waterline W corresponding to G1P1 and G1P2 is drawn respectively. P1 L P1 W P2 L P2 The two water lines intersect at point O. Therefore, when point P moves from P1 to P2, the corresponding water line changes direction from W... P1 L P1 Rotate to W P2 L P2 Based on the water inflow and outflow volumes shown by the shaded area in the diagram, it can be deduced that when point P moves from P1 to P2, the center of buoyancy below the waterline will move towards the stern. That is, when point P moves from the stern to the bow, the center of buoyancy moves from the bow to the stern.

[0035] Based on conclusion (2), it can be concluded that when P traverses from B to B', a point P0 can be found such that the waterline W corresponding to G1P0 is... P0 L P0 The lower hull's center of buoyancy, Bp, lies exactly on the straight line G1P0, which is the final state of equilibrium.

[0036] (4) Iterative calculation method

[0037] The variation of the center of buoyancy position with the movement of point P, derived above, can be used to rapidly converge point P between points B and B' using the bisection method, thus calculating the final equilibrium position after the compartment floods. Specific steps include:

[0038] 1) Choose any point P in BB', then the perpendicular line WpLp of G1P is the corresponding waterline angle;

[0039] 2) Based on the total weight of the ship after water ingress, along the G1P direction, use the bisection method to make the displacement below the waterline WpLp equal to the total weight of the ship. The convergence result is the height of the waterline WpLp.

[0040] 3) Output the buoyancy center position Bp of the ship section below the waterline WpLp using the 3D model;

[0041] 4) If Bp is to the right of G1P, then place point P on BB' and move it to the right by two parts; similarly, if it is to the left, move point P to the left by two parts.

[0042] 5) Repeat steps 2) to 4) until the distance between point Bp and the straight line G1P is less than the given precision, that is, Bp and G1P are considered to be collinear. This state is the final equilibrium floating state after the compartment is flooded.

[0043] Based on the above principles, this invention proposes a model-based method for calculating the floating state of a ship's compartments during water ingress, comprising the following steps:

[0044] S1. Given the location and volume of water entering a compartment, calculate the total weight of the ship after water ingress △ and the changed position of the center of gravity G1;

[0045] S2. Load the ship model. According to the technical plan, establish the initial center of buoyancy B, the initial center of gravity G, the center of gravity G1 after water ingress, and the intersection point B' of the horizontal line passing through the center of buoyancy B and the vertical line passing through the center of gravity G1 in the model. Take any point P on BB', connect G1P, and construct the vertical plane of G1P as the waterline surface WpLp model. Figure 4 As shown;

[0046] S3. Based on the calculated total weight Δ of the ship after flooding, determine the height of the waterline WpLp along the G1P direction using the bisection method, ensuring that the displacement below the waterline WpLp equals the total weight of the ship. Then, based on the model, obtain the position Bp of the center of buoyancy of the ship below the waterline WpLp at point P. Measure the distance d between point Bp and the straight line G1P. Figure 5 As shown;

[0047] S4. Based on the changing pattern of the center of buoyancy position with the movement of point P, and according to the position of Bp, determine the direction of the bisection of point P on BB', and start the iterative calculation.

[0048] S5. Repeat steps S3 to S4 until the distance between point Bp and the straight line G1P is less than the given precision, that is, Bp and G1P are considered to be collinear. This state is the final equilibrium floating state after the compartment is flooded.

[0049] In this embodiment, as Figure 6 As shown, when d = 0.013 mm, which is less than the given accuracy, it is assumed that the center of buoyancy Bp corresponding to the current point P position is on the straight line G1P, that is, the buoyancy and gravity are collinear. At this time, the position of Bp is the final position of the center of buoyancy, thus determining the final floating state after the compartment is flooded.

[0050] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0051] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A model-based method for calculating the floating state of a ship's compartment during water ingress, characterized in that, Includes the following steps: S1. Given the location and volume of water entering a compartment, calculate the total weight of the ship after water ingress △ and the changed position of the center of gravity G1; S2. Load the ship model. According to the technical plan, establish the initial buoyancy center B, the initial center of gravity G, the center of gravity G1 after entering the water, and the intersection point B' of the horizontal line passing through the buoyancy center B and the vertical line passing through the center of gravity G1 in the model. Then, take any point P on BB', connect G1P, and make the vertical plane of G1P as the waterline surface WpLp model. S3. Based on the calculated total weight of the ship after water ingress △, determine the height of the waterline WpLp along the G1P direction using the bisection method, so that the displacement below the waterline WpLp is equal to the total weight of the ship, and obtain the buoyancy center position Bp of the ship part below the waterline WpLp at point P based on the model, and measure the distance d between point Bp and the straight line G1P. S4. Based on the changing pattern of the center of buoyancy position with the movement of point P, and according to the position of Bp, determine the direction of the bisection of point P on BB', and start the iterative calculation. S5. Repeat steps S3 to S4 until the distance between point Bp and the straight line G1P is less than the given precision, that is, Bp and G1P are considered to be collinear. This state is the final equilibrium floating state after the compartment is flooded.

2. The model-based method for calculating the floating state of a ship's compartment during flooding, as described in claim 1, is characterized in that... In step S4, the position of the center of buoyancy changes with the movement of point P as follows: when point P moves from stern to bow, the position of the center of buoyancy moves from bow to stern; when point P moves from bow to stern, the position of the center of buoyancy moves from stern to bow.

3. The model-based method for calculating the floating state of a ship's compartment during flooding, as described in claim 2, is characterized in that... In step S4, based on the position of Bp, determine the direction of the bisection of point P on BB'. Specifically: if Bp is to the right of G1P, then move point P to the right on BB'; if Bp is to the left of G1P, then move point P to the left.

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