A calculation method for the floating critical point of a ship

Abstract

The present invention relates to the technical field of ships, and discloses a calculation method for the floating critical point of a ship, including: constructing a force model of the ship when the longitudinal inclination angle of the ship is zero; setting a value range for the draft depth of the ship; taking multiple draft depth values of the ship within the value range; obtaining the displacement volume and the distance from the longitudinal action position of the buoyancy to the after perpendicular of the ship corresponding to each draft depth value according to the ship hydrostatic parameter table; calculating the moment of the reaction force of the support acting on the center of gravity position of the ship and the moment of the buoyancy of the ship acting on the center of gravity position of the ship according to each draft depth value, displacement volume, distance from the longitudinal action position of the buoyancy to the after perpendicular of the ship, and the force model of the ship; calculating the moment difference; and determining the occurrence time of the floating critical point of the ship according to the moment difference. The present invention can determine the occurrence time of the floating critical point of the ship, and provide support for judging whether the ship launching plan and attitude prediction are accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of ships, and particularly to a method for calculating the floating critical point of a ship. Background Art

[0002] The floating critical point of a ship refers to the moment when the ship is arranged on the supports of a dry dock, a floating dock or a semi-submersible ship, and after the hull is gradually immersed by filling water into the dry dock or floating dock or submerging the semi-submersible ship, the bow or the stern begins to separate from the support. The floating critical point of a ship is an important factor to be considered in the calculation of floating launching, and its uses mainly come from the following three situations:

[0003] First, when the target ship is launched by a dry dock, when the target ship does not float and other ships except the target ship float and launch, it is necessary to accurately calculate the floating critical point of the target ship to determine that the target ship still does not separate from the support when the water level in the dry dock is the same as the sea level;

[0004] Second, when the target ship is launched by a floating dock or a semi-submersible ship submerging, generally, the longitudinal inclination angle of the floating dock or the semi-submersible ship is made the same as that of the target ship to ensure that the bow and stern of the target ship separate from the support at the same time, and the floating critical point is an important reference basis among them. Therefore, it is necessary to accurately calculate the critical point when the bow or stern of the target ship floats or separates from the support, so as to provide a basis for the floating dock or the semi-submersible ship to adjust the submerging attitude in time and ensure the safe launching of the target ship;

[0005] Third, when the ship floats by filling water into the dry dock, it is necessary to accurately calculate the floating critical point of the ship to monitor the floating dynamics of the ship. If there is a deviation between the occurrence time of the floating critical point and the calculation, it can be judged that the final floating state of the ship must be different from the expected calculation. It is an important basis for judging whether the calculation results of the weight, center of gravity and floating state of the target ship are accurate. When the floating critical point occurs, the target ship has not fully floated, which can gain time for re-calculating the floating state and taking emergency plans to avoid major safety accidents.

[0006] However, the current floating critical point of a ship is difficult to capture. Therefore, there is an urgent need for a method capable of calculating the floating critical point of a ship. Summary of the Invention

[0007] In view of the above problems, the purpose of the present invention is to provide a method for calculating the floating critical point of a ship to solve the problems that the floating critical point of a ship is difficult to calculate and capture.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] The method for calculating the floating critical point of the ship described in the present invention includes the following steps:

[0010] Step S1, constructing a ship force model when the longitudinal inclination angle of the ship is zero;

[0011] Step S2, set the value range of the draft of the ship.

[0012] Step S3, take multiple draft values of the ship within the value range of the draft of the ship.

[0013] Step S4, obtain the displacement volume and the distance from the longitudinal action position of the buoyancy force to the after perpendicular of the ship corresponding to each draft value according to the hydrostatic parameters table of the ship.

[0014] Step S5, according to each draft value of the ship, the displacement volume, the distance from the longitudinal action position of the buoyancy force to the after perpendicular of the ship, and the ship force model, calculate the moment of the reaction force of the support acting on the ship's center of gravity position corresponding to each draft value of the ship, denoted as the first moment; and the moment of the buoyancy force of the ship acting on the ship's center of gravity position corresponding to each draft value of the ship, denoted as the second moment.

[0015] Step S6, calculate the moment difference between the second moment and the first moment.

[0016] Step S7, determine the occurrence time of the ship's floating critical point according to the moment difference.

[0017] Preferably, the step S7 includes:

[0018] Step S71, arrange each draft value of the ship in ascending order.

[0019] Step S72, take the draft of the ship corresponding to the first moment difference greater than zero in the arranged order as the occurrence time of the ship's floating critical point.

[0020] Preferably, after the step S71 and before the step S72, it further includes:

[0021] According to the arranged order, denote the draft of the ship corresponding to the first moment difference greater than zero as the first draft of the ship, and denote the draft of the ship corresponding to the last moment difference equal to zero as the second draft of the ship.

[0022] Take the first draft of the ship and the second draft of the ship as the interval values to reset the value range of the draft of the ship.

[0023] Repeat step S3 - step S71.

[0024] Preferably, the step S5 includes:

[0025] Step S51, according to each draft value of the ship, the displacement volume, the distance from the longitudinal action position of the buoyancy force to the after perpendicular of the ship, and the ship force model, calculate the second moment.

[0026] Step S52: Assume that the first moment is equal to the second moment, and calculate the distance from the acting position of the pier reaction force to the longitudinal center of gravity of the ship according to the first moment.

[0027] Step S53: If the distance from the acting position of the pier reaction force to the longitudinal center of gravity of the ship is less than the distance from the position of the most aft pier to the longitudinal center of gravity of the ship, then use the assumed first moment as the first moment corresponding to the ship draft value; if the distance from the acting position of the pier reaction force to the longitudinal center of gravity of the ship is equal to or greater than the distance from the position of the most aft pier to the longitudinal center of gravity of the ship, then make the distance from the acting position of the pier reaction force to the longitudinal center of gravity of the ship equal to the distance from the position of the most aft pier to the longitudinal center of gravity of the ship, repeat Step S51, and perform Step S54.

[0028] Step S54: Calculate the first moment according to the ship gravity, displacement volume, and the distance from the position of the most aft pier to the longitudinal center of gravity of the ship.

[0029] Preferably, in Step S51, the second moment is calculated according to the following formula:

[0030] M2 = ρ * g * V * L2

[0031] where M2 represents the moment of the ship's buoyancy acting on the ship's center of gravity position, ρ represents the water density, g represents the acceleration due to gravity, V represents the displacement volume, and L2 represents the distance from the longitudinal acting position of the buoyancy to the longitudinal center of gravity of the ship.

[0032] Preferably, in Step S54, the first moment is calculated according to the following formula:

[0033] M1 = (G - ρ * g * V) * L1

[0034] where M1 represents the moment of the pier reaction force acting on the ship's center of gravity position, G represents the ship gravity, ρ represents the water density, g represents the acceleration due to gravity, V represents the displacement volume, and L1 represents the distance from the acting position of the pier reaction force to the longitudinal center of gravity of the ship.

[0035] Preferably, in Step S2, the steps of setting the value range of the ship draft include:

[0036] Calculate the bow draft and stern draft of the ship in the fully floating state according to the hull structure, and set the smaller value of the value range of the ship draft to be less than the smaller value of the bow draft and stern draft; set the larger value of the value range of the ship draft to be greater than the larger value of the bow draft and stern draft.

[0037] Preferably, in the step S1, the parameters in the ship force model include the ship's gravity, buoyancy, pier reaction force, the distance from the position of the rearmost pier to the longitudinal center of gravity of the ship, the distance from the position where the pier reaction force acts to the longitudinal center of gravity of the ship, the distance from the longitudinal acting position of the buoyancy to the longitudinal center of gravity of the ship, the distance from the longitudinal acting position of the buoyancy to the after perpendicular of the ship, and the distance from the longitudinal center of gravity position of the ship to the after perpendicular of the ship.

[0038] Preferably, the calculation method further includes a step of verifying the occurrence time of the ship's floating critical point.

[0039] Preferably, the step of verifying the occurrence time of the ship's floating critical point includes: according to the punch points marked on the ship, recording the draft depth at the position of the punch points of the ship through a total station.

[0040] Compared with the prior art, the beneficial effect of the calculation method for the ship's floating critical point in the embodiment of the present invention is as follows:

[0041] The calculation method for the ship's floating critical point in the embodiment of the present invention, by establishing a ship force model when the ship's longitudinal inclination angle is zero, according to each ship draft depth value, displacement volume, the distance from the longitudinal acting position of the buoyancy to the after perpendicular of the ship, and the ship force model, can calculate the moment of the pier reaction force acting on the ship's center of gravity position corresponding to each ship draft depth value, and the moment of the ship's buoyancy acting on the ship's center of gravity position corresponding to each ship draft depth value. During the process of the external water level rising continuously, the buoyancy moment, pier reaction force moment, and ship attitude will change. In the initial stage, the ship is supported by the pier, and the buoyancy moment is equal to the pier reaction force moment. As the water level rises, the buoyancy moment will be greater than the pier reaction force moment, and the ship will gradually be subjected to a moment that causes the ship to overturn, and the ship will gradually break away from the pier and start to float. Therefore, the occurrence time of the ship's floating critical point can be determined according to the moment difference. By calculating the occurrence time of the ship's floating critical point, it can provide support for judging whether the ship launching plan and attitude prediction are accurate, ensure that the attitude of the ship after floating meets the established requirements, and ensure the safety of the ship. Description of the Drawings

[0042] Figure 1 is a flowchart of the calculation method for the ship's floating critical point in the embodiment of the present invention;

[0043] Figure 2 is a schematic diagram of the ship force model in the embodiment of the present invention. Detailed Embodiments

[0044] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0045] The following will further describe in detail the specific implementation manners of the present invention with reference to the drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0046] As Figure 1 shown, a method for calculating the floating critical point of a ship according to an embodiment of the present invention includes the following steps:

[0047] Step S1, construct a ship force model when the longitudinal inclination angle of the ship is zero;

[0048] Step S2, set the value range of the draft depth of the ship;

[0049] Step S3, take multiple draft depth values of the ship within the value range of the draft depth of the ship;

[0050] Step S4, obtain the displacement volume and the distance from the longitudinal action position of the buoyancy to the after perpendicular of the ship corresponding to each draft depth value according to the ship hydrostatic parameter table;

[0051] Step S5, according to each draft depth value, displacement volume, the distance from the longitudinal action position of the buoyancy to the after perpendicular of the ship, and the ship force model, calculate the moment of the reaction force of the support acting on the ship's center of gravity position corresponding to each draft depth value, denoted as the first moment; and the moment of the ship's buoyancy acting on the ship's center of gravity position corresponding to each draft depth value, denoted as the second moment;

[0052] Step S6, calculate the moment difference between the second moment and the first moment;

[0053] Step S7, determine the occurrence time of the floating critical point of the ship according to the moment difference.

[0054] During the floating process of the ship, the different longitudinal action positions of the ship's gravity and buoyancy are the fundamental reasons for the non-simultaneous floating of the bow and stern of the ship. As Figure 2As shown, taking the example of the trimmed stern of the sample ship, when the longitudinal inclination angle of the ship is zero, a model of the support reaction force of the pier, buoyancy force, gravity force, and acting moment is established. The parameters in the ship's force model include the ship's gravity G, buoyancy F2, support reaction force of the pier F1, distance L0 from the position of the most aft pier to the longitudinal center of gravity of the ship, distance L1 from the position where the support reaction force of the pier acts to the longitudinal center of gravity of the ship (the maximum value of L1 is L0), distance L2 from the longitudinal acting position of the buoyancy force to the longitudinal center of gravity of the ship, distance LCB from the longitudinal acting position of the buoyancy force to the after perpendicular AP of the ship, distance LCG from the longitudinal center of gravity position of the ship to the after perpendicular AP of the ship, and average draft T. If the sample ship has a forward trim, the acting positions indicated by the buoyancy F2 and the support reaction force of the pier F1 are opposite, that is, the acting position of the buoyancy F2 is on the left side of the gravity acting position, and the acting position of the support reaction force of the pier F1 is on the right side of the gravity acting position.

[0055] In this embodiment, in the step S2, the steps of setting the value range of the ship's draft include: calculating the bow draft and stern draft of the ship in the fully floating state according to the hull structure, and setting the smaller value of the value range of the ship's draft to be less than the smaller value of the bow draft and stern draft; setting the larger value of the value range of the ship's draft to be greater than the larger value of the bow draft and stern draft. When the ship's hull structure is determined, the fully floating state of the ship is determined, and thus the bow draft and stern draft of the ship in the floating state can be calculated in advance. The set value range can cover the bow draft and stern draft of the ship in the fully floating state, so as to ensure that the occurrence time of the ship's floating critical point is within the value range.

[0056] In this embodiment, the step S5 includes:

[0057] Step S51, according to each ship draft value, displacement volume, distance from the longitudinal acting position of the buoyancy force to the after perpendicular of the ship, and the ship's force model, calculate the second moment corresponding to each ship draft value;

[0058] Step S52, assuming that the first moment is equal to the second moment, calculate the distance from the position where the support reaction force of the pier acts to the longitudinal center of gravity of the ship according to the first moment;

[0059] Step S53, if the distance from the position where the support reaction force of the pier acts to the longitudinal center of gravity of the ship is less than the distance from the position of the most aft pier to the longitudinal center of gravity of the ship, then use the assumed first moment as the first moment corresponding to the ship draft value; if the distance from the position where the support reaction force of the pier acts to the longitudinal center of gravity of the ship is equal to or greater than the distance from the position of the most aft pier to the longitudinal center of gravity of the ship, then set the distance from the position where the support reaction force of the pier acts to the longitudinal center of gravity of the ship to be equal to the distance from the position of the most aft pier to the longitudinal center of gravity of the ship, repeat step S51, and perform step S54;

[0060] Step S54: Calculate the first moment according to the ship's gravity, displacement volume, and the distance from the position of the rearmost pier to the longitudinal center of gravity of the ship.

[0061] When the ship has not started to float, the ship is supported by the reaction force of the pier, and the buoyancy of the ship is small. At this time, the second moment of the ship is equal to the first moment. As the draft depth value of the ship gradually increases, the buoyancy gradually increases, the reaction force of the pier gradually decreases, and the distance from the position of the reaction force of the pier to the longitudinal center of gravity of the ship gradually increases. However, since the ship has not started to float, the acting moments of the buoyancy and the reaction force of the pier can still maintain balance. At this time, the first moment can be set equal to the calculated second moment, that is, the assumed first moment is used as the first moment corresponding to the draft depth value of the ship. As the draft depth value of the ship increases, when the distance from the position of the reaction force of the pier to the longitudinal center of gravity of the ship increases to be equal to the distance from the position of the rearmost pier to the longitudinal center of gravity of the ship and no longer increases, the balance between the first moment and the second moment will be broken. At this time, the distance from the position of the reaction force of the pier to the longitudinal center of gravity of the ship can be used as a known quantity to calculate the first moment.

[0062] In the said step S51, the second moment is calculated according to the following formula:

[0063] M2 = ρ * g * V * L2

[0064] where, M2 represents the moment of the ship's buoyancy acting on the center of gravity position of the ship, ρ represents the water density, with a value of 1 Ton / m 3 , g represents the acceleration due to gravity, with a value of 9.8 m / s 2 , V represents the displacement volume, and L2 represents the distance from the longitudinal acting position of the buoyancy to the longitudinal center of gravity of the ship.

[0065] When the sample ship has a stern trim, as Figure 2 shown, L2 = LCB - LCG, where, LCB represents the distance from the longitudinal acting position of the buoyancy to the after perpendicular of the ship, and LCG represents the distance from the longitudinal center of gravity position of the ship to the after perpendicular of the ship.

[0066] In the said step S54, the first moment is calculated according to the following formula:

[0067] M1 = (G - ρ * g * V) * L1

[0068] where, M1 represents the moment of the reaction force of the pier acting on the center of gravity position of the ship, G represents the ship's gravity, ρ represents the water density, with a value of 1 Ton / m 3 , g represents the acceleration due to gravity, with a value of 9.8 m / s 2 , V represents the displacement volume, and L1 represents the distance from the position of the reaction force of the pier to the longitudinal center of gravity of the ship.

[0069] Specifically, during the calculation, first calculate the buoyancy F2 according to the displacement volume corresponding to the ship draft depth value, where F2 = ρ * g * V. Calculate the pier reaction force F1 based on the buoyancy F2 and the ship gravity G, where F1 = G - F2. Calculate the first moment M1 based on the pier reaction force F1 and the distance L1 from the position where the pier reaction force acts to the longitudinal center of gravity of the ship.

[0070] Among them, the ship gravity and the distance from the longitudinal center of gravity of the ship to the after perpendicular of the ship are determined according to the inherent properties of the ship's hull structure.

[0071] In this embodiment, the step S7 includes:

[0072] Step S71, arrange each ship draft depth value in ascending order;

[0073] Step S72, according to the arrangement order, take the ship draft depth corresponding to the first moment difference greater than zero as the moment when the ship floating critical point occurs. The ship draft depth value can intuitively represent the moment when the ship starts to float.

[0074] Furthermore, after the step S71 and before the step S72, it also includes:

[0075] According to the arrangement order, record the ship draft depth corresponding to the first moment difference greater than zero as the first ship draft depth, and record the ship draft depth corresponding to the last moment difference equal to zero as the second ship draft depth;

[0076] Use the first ship draft depth and the second ship draft depth as interval values to re-set the value range of the ship draft depth;

[0077] Repeat step S3 - step S71.

[0078] By re-selecting the value range of the ship draft depth twice, the calculation accuracy of the ship floating critical point can be improved.

[0079] In the present invention, when taking multiple ship draft depth values within the value range of the ship draft depth, the interval between each ship draft depth value can be determined according to the specific interval range, and the present invention does not make specific limitations.

[0080] Taking the value range of the ship draft depth as 2.85m - 3.1m as an example, illustrate the process of the ship floating with the change of the draft depth.

[0081] First, take multiple ship draft depth values within the value range of the ship draft depth, and calculate each parameter of the ship force model according to the ship hydrostatic parameter table and the ship force model as shown in Table 1 below.

[0082] Table 1

[0083]

[0084] As Figure 2 shown in the figure and Table 1, during the process of the continuous rise of the external water level of the ship, the buoyancy moment, the reaction force moment of the pier, and the ship attitude will change in the following several stages.

[0085] First stage: When the draft depth value of the ship is zero, the resultant force of the reaction force of the pier is the same as the ship's gravity, and the ship is not affected by buoyancy, that is, F1 = G, L1 = 0, F2 = 0;

[0086] Second stage: When the draft depth value of the ship gradually rises in the range of 0 - 2.97m, the buoyancy F2 received by the ship gradually increases, and the reaction force F1 of the pier gradually decreases. Taking the gravity center of the ship's own weight as the reference point, due to the trimming characteristics of the sample ship 2, the acting distance L1 of the reaction force of the pier to the ship's gravity center gradually shifts and increases towards the tail, but the moments of the reaction force F1 of the pier and the buoyancy F2 on the ship's gravity center still maintain balance, that is, M1 = M2. There is no moment that causes the ship to overturn in this stage, and the sample ship 2 remains stationary on the pier 1;

[0087] Third stage: As the external water level of the hull continues to rise and reaches and exceeds 2.97m, the values of F2, L1, and L2 continuously increase, and the reaction force F1 of the pier continuously decreases. When L1 increases to be the same as L0, it means that the reaction force F1 is borne by the pier closest to the tail, and the ship enters the single-point force-bearing stage. As the water level rises again, since F1 gradually decreases and L1 = L0 remains unchanged, while the buoyancy F2 and L2 still continue to increase, the balance between M1 and M2 will necessarily be gradually broken, making M2 > M1. After the moment M2 generated by the buoyancy takes the upper hand, the ship will gradually be subjected to the moment that causes the ship to overturn. When the draft depth value of the ship is close to 3m, the bow of the ship breaks away from the pier and begins to float, and this is the occurrence moment of the ship floating critical point.

[0088] Fourth stage: As the water level continues to rise, the buoyancy F2 continuously increases, the reaction force of the pier continuously decreases, and the acting distance L2 of the buoyancy F2 on the gravity center G point of the sample ship will gradually approach the gravity center G point position, and the trimming trend of the sample ship gradually increases. When the buoyancy F2 reaches the same as the ship's own weight G, the acting positions will also coincide, and the ship will be in a completely free floating state.

[0089] The calculation method further includes the step of verifying the occurrence moment of the ship floating critical point. Further, the step of verifying the occurrence moment of the ship floating critical point includes: According to the punch points marked on the ship, the total station is used to record the draft depth at the punch point position of the ship. By combining the total station with the punch points, it can be judged whether a certain section of the ship begins to float, so as to verify whether the draft depth value corresponding to the calculated occurrence moment of the ship floating critical point is consistent with the draft depth value recorded by the total station.

[0090] The present invention provides a calculation method for the critical point of ship floating, which can calculate the occurrence time of the critical point of ship floating. By calculating the critical point of ship floating, it can be used as the basis for whether the ship launching plan and attitude prediction are accurate. If there is a deviation between the occurrence time of the critical point of ship floating and the calculation, it can be proved that there must be a deviation between the attitude of the ship after floating and the calculation. Then, necessary load adjustment can be carried out on the ship before it floats to ensure that the attitude after floating meets the established requirements and ensure the safety of the ship. Moreover, the present invention provides important technical support for ships using the floating launching method, improves the accuracy of launching calculation, reduces the occurrence of outer plate deformation, skid blocks, equipment damage or casualties, and solves the problem that low-tonnage ships are sensitive to transverse and longitudinal moments and are prone to safety accidents.

[0091] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present invention, several improvements and replacements can be made, and these improvements and replacements should also be regarded as the protection scope of the present invention.

Claims

1. A calculation method for the floating critical point of a ship, characterized in that It includes the following steps: Step S1, constructing a ship force model when the longitudinal inclination angle of the ship is zero; Step S2, setting the value range of the ship draft; Step S3, taking multiple ship draft values within the value range of the ship draft; Step S4, obtaining the displacement volume and the distance from the longitudinal action position of the buoyancy to the ship's after perpendicular corresponding to each ship draft value according to the ship hydrostatic parameter table; Step S5, calculating the moment of the pier reaction force acting on the ship's center of gravity position corresponding to each ship draft value according to each ship draft value, displacement volume, the distance from the longitudinal action position of the buoyancy to the ship's after perpendicular, and the ship force model, denoted as the first moment; And the moment of the ship buoyancy acting on the ship's center of gravity position corresponding to each ship draft value, denoted as the second moment; Step S6, calculating the moment difference between the second moment and the first moment; Step S7, determining the occurrence time of the ship floating critical point according to the moment difference; 2. The calculation method of the ship floating critical point according to claim 1, wherein The said Step S7 includes: Step S71, arranging each ship draft value in ascending order; Step S72, taking the ship draft corresponding to the first moment difference greater than zero in the arranged order as the occurrence time of the ship floating critical point; 3. The calculation method of the ship floating critical point according to claim 2, characterized in that, After the said Step S71 and before the said Step S72, it further includes: In the arranged order, denoting the ship draft corresponding to the first moment difference greater than zero as the first ship draft, and denoting the ship draft corresponding to the last moment difference equal to zero as the second ship draft; Taking the first ship draft and the second ship draft as the interval values to reset the value range of the ship draft; Repeating Step S3 - Step S71; 4. The calculation method of the ship floating critical point according to claim 1, wherein The said Step S5 includes: Step S51, calculating the second moment according to each ship draft value, displacement volume, the distance from the longitudinal action position of the buoyancy to the ship's after perpendicular, and the ship force model; Step S52, assuming that the first moment is equal to the second moment, and calculating the distance from the pier reaction force action position to the ship's longitudinal center of gravity according to the first moment; Step S53, if the distance from the pier reaction force action position to the ship's longitudinal center of gravity is less than the distance from the position of the most aft pier to the ship's longitudinal center of gravity, then taking the assumed first moment as the first moment corresponding to the ship draft value; if the distance from the pier reaction force action position to the ship's longitudinal center of gravity is equal to or greater than the distance from the position of the most aft pier to the ship's longitudinal center of gravity, then taking the distance from the pier reaction force action position to the ship's longitudinal center of gravity equal to the distance from the position of the most aft pier to the ship's longitudinal center of gravity, repeating Step S51, and performing Step S54; Step S54, calculating the first moment according to the ship gravity, displacement volume, and the distance from the position of the most aft pier to the ship's longitudinal center of gravity; 5. The calculation method of the ship floating critical point according to claim 4, characterized in that, In the said Step S51, calculating the second moment according to the following formula M2 = ρ * g * V * L2 where, M2 represents the moment of the ship buoyancy acting on the ship's center of gravity position, ρ represents the water density, g represents the acceleration due to gravity, V represents the displacement volume, and L2 represents the distance from the longitudinal action position of the buoyancy to the ship's longitudinal center of gravity; 6. The calculation method of the ship floating critical point according to claim 4, characterized in that In the said Step S54, calculating the first moment according to the following formula M1 = (G - ρ * g * V)L1 Wherein, M1 represents the moment of the pier reaction force acting on the center of gravity position of the ship; G represents the gravity of the ship; ρ represents the water density; g represents the acceleration of gravity; V represents the displacement volume; and L1 represents the distance from the acting position of the pier reaction force to the longitudinal center of gravity of the ship.

7. The calculation method of the ship floating critical point according to claim 1, characterized in that, In the step S2, the steps of setting the value range of the ship draft include: Calculating the bow draft and the stern draft of the ship in the fully floating state according to the hull structure, and setting the smaller value of the value range of the ship draft to be less than the smaller value of the bow draft and the stern draft; setting the larger value of the value range of the ship draft to be greater than the larger value of the bow draft and the stern draft.

8. The calculation method of the ship floating critical point according to claim 1, characterized in that In the step S1, the parameters in the ship force model include the gravity of the ship, the buoyancy force, the pier reaction force, the distance from the position of the rearmost pier to the longitudinal center of gravity of the ship, the distance from the acting position of the pier reaction force to the longitudinal center of gravity of the ship, the distance from the longitudinal acting position of the buoyancy force to the longitudinal center of gravity of the ship, the distance from the longitudinal acting position of the buoyancy force to the after perpendicular of the ship, and the distance from the longitudinal center of gravity position of the ship to the after perpendicular of the ship.

9. The calculation method of the ship floating critical point according to claim 1, characterized in that The calculation method further includes a step of verifying the occurrence time of the ship floating critical point.

10. The calculation method of the ship floating critical point according to claim 9, characterized in that, The step of verifying the occurrence time of the ship floating critical point includes: according to the punch points marked on the ship, recording the draft at the punch point positions of the ship by using a total station.

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