A method and system for evaluating the ultimate stability of a polar vessel in ice conditions

Abstract

The application discloses a polar ship icing condition limit stability evaluation method and system, and the method comprises the following steps: obtaining ship data and environmental parameters, inputting a dynamic icing calculation model, and calculating the ship icing distribution; obtaining the ship stability righting lever curve according to the real-time motion state of the ship and the ship icing distribution, processing the ship stability righting lever curve, and obtaining the dynamic stability curve; calculating the limit dynamic inclination and the maximum dynamic inclination lever under different icing conditions based on the dynamic stability curve, and solving the limit wind speed and the wind scale that can be borne by the ship under different icing conditions according to the calculation results, and comprehensively evaluating and judging the limit stability of the polar ship. The application realizes the dynamic update of the icing distribution with the change of the ship motion state by obtaining the state change parameters corresponding to the ship at each time step based on the six-degree-of-freedom motion equation of the ship, and the total amount of flying spray is calculated by combining the sea wave spray and the wind-generated flying spray, so that the ship stability analysis combines the icing and the wind wave, and the accuracy and the reliability of the stability evaluation are improved.

Description

Technical Field

[0001] This invention relates to the field of ship stability calculation, and in particular to a method and system for assessing the ultimate stability of ships in polar ice conditions. Background Technology

[0002] As global warming continues, sea ice cover in the Arctic is shrinking, making resource extraction and transportation easier and highlighting the Arctic's strategic value. Countries are increasingly vying for Arctic resources. The Arctic region is rich in oil, gas, and mineral resources, and Arctic shipping routes offer significant advantages over traditional routes, such as lower costs and shorter travel times. However, polar regions often face extreme weather conditions such as low temperatures, strong winds, and blizzards. Coupled with insufficient crew experience, inadequate infrastructure, and limited emergency response capabilities, polar vessels face greater risks and challenges, placing higher demands on ship stability.

[0003] Ship stability is a crucial indicator of ship performance, referring to a ship's ability to resist capsizing when it heels under external forces (such as wind and wave forces) and to return to its original equilibrium state after the external forces disappear. In polar environments, ships often experience icing due to extreme weather. Icing typically occurs when the bow strikes waves, generating spray that condenses into ice at low temperatures. This raises the ship's center of gravity, reduces initial stability, and asymmetrical ice distribution can cause heeling or trimming, leading to a sharp deterioration in ship stability. When encountering severe wind and sea conditions, ships are prone to significant nonlinear rolling motions. If the ship's restoring moment is insufficient, it will capsize.

[0004] Existing research typically analyzes the effects of icing or wind and wave conditions on ship stability in isolation, lacking a methodology that combines icing with wind and wave analysis. This significantly limits the assessment of ship stability under real polar navigation conditions. Most existing ship stability studies quantify the impact of waves on ship stability solely through resonance angles, neglecting the prevalent icing phenomenon in polar navigation. This makes traditional methods inaccurate in reflecting the changing patterns of ship stability under actual polar navigation conditions, especially under the combined effects of wind, waves, and icing, particularly when assessing key indicators such as limiting dynamic stability, limiting dynamic heel angle, and corresponding limiting wind speeds. Summary of the Invention

[0005] To address the shortcomings of existing technologies in combining ice accumulation and wind and waves for ship stability analysis, and inadequate analysis of the interaction between ice accumulation distribution and ship motion, this invention provides a method and system for extreme stability assessment of ships under polar ice conditions, enabling the assessment of ship stability in real polar navigation environments.

[0006] Therefore, the technical solution adopted by the present invention is as follows: A method for assessing the ultimate stability of ships under icing conditions in polar regions is provided, the method comprising: Ship data and environmental parameters are acquired and input into a dynamic icing calculation model to calculate the ship's ice distribution. Specifically, the dynamic icing calculation model discretizes the ship into a grid, obtains the ship's real-time motion state based on the ship's six-degree-of-freedom motion equations, calculates the total amount of droplets in each grid, and integrates them to obtain the total amount and distribution of ship ice. Droplets include wave droplets and wind-generated droplets. Based on the ship's real-time motion state and ice accumulation distribution, the ship's stability recovery arm curve is obtained and processed to obtain the dynamic stability curve; Based on the dynamic stability curve, the limiting dynamic tilt angle and maximum dynamic tilt arm under different icing conditions are calculated. Based on the calculation results, the limiting wind speed and corresponding wind level that the ship can withstand under different icing conditions are solved, and the limiting stability of polar ships is comprehensively evaluated and judged.

[0007] According to the above scheme, the ship data includes ship length, ship width, bow length, superstructure location and external dimensions; the environmental parameters include wind speed, ship speed, temperature, ice accumulation duration, and the angle between the heading and the wind direction.

[0008] According to the above scheme, the six degrees of freedom motion of a ship includes translational motion and rotational motion; among which, translational motion includes translation, rolling, and heaving, and rotational motion includes roll, pitch, and yaw; the equations of motion of the ship in six degrees of freedom are specifically calculated based on mass, mass moment of inertia, center of gravity position, translational velocity, and angular velocity to calculate the ship's longitudinal translation, lateral translation, vertical translation, external moment in the roll direction, external moment in the pitch direction, and external moment in the yaw direction.

[0009] According to the above scheme, the total amount of droplets is specifically calculated by adding the amount of droplets that freeze into ice, the amount of droplets that form a brine film, and the amount of droplets that evaporate. The amount of droplets that freeze into ice is specifically calculated based on droplet flux and freezing coefficient; The droplet flux includes wave droplet volume and wind-generated droplet volume; the wave droplet volume is calculated based on the height of the wave droplet above the deck, the significant wave height, and the relative speed between the ship and the wave, while the wind-generated droplet volume is calculated based on the significant wave height.

[0010] According to the above scheme, the specific position of the ship's center of gravity is calculated by integrating the positions of the vertical, horizontal, and lateral ice accumulation centers of gravity of each grid.

[0011] According to the above scheme, the freezing coefficient is specifically calculated based on the heat balance equation and the temperature at the interface between the brine film and the air, as well as the air temperature.

[0012] According to the above scheme, the ship's stability recovery arm curve is specifically calculated through the NAPA stability calculation module; The limiting dynamic tilt angle is specifically determined by taking the abscissa position corresponding to the resonance angle as the initial point A, moving a certain distance from point A along the positive direction of the abscissa to set point B, and drawing the tangent AC of the dynamic stability curve with point A as the tangent point. The abscissa corresponding to the intersection point C of the tangent line and the dynamic stability curve is the limiting dynamic tilt angle. The maximum dynamic tilt arm is determined by drawing a vertical line through point B that intersects the tangent AC at point D. The length of line segment BD is the maximum dynamic tilt arm.

[0013] According to the above scheme, the maximum wind speed and corresponding wind level that the ship can withstand are calculated based on the ship's displacement and maximum dynamic tilting arm. The maximum dynamic tilting moment is calculated based on the maximum dynamic tilting moment, the height of the ship's center of area above the waterline, and the ship's draft. The ultimate wind pressure is then calculated based on the maximum wind pressure. By referring to the Beaufort scale table based on the ultimate wind pressure, the ultimate wind level and corresponding ultimate wind speed that the ship can withstand under the corresponding calculation conditions can be obtained.

[0014] A system for assessing the ultimate stability of ships under polar ice conditions is also provided, the system comprising: The ice accumulation calculation module is used to acquire ship data and environmental parameters, input them into a dynamic ice accumulation calculation model, and calculate the ship's ice accumulation distribution. Specifically, the dynamic ice accumulation calculation model discretizes the ship into a grid, obtains the ship's real-time motion state based on the ship's six-degree-of-freedom motion equations, calculates the total amount of spray in each grid, and integrates them to obtain the total amount and distribution of ship ice accumulation. Among them, spray includes sea spray and wind-generated spray. The processing module is used to obtain the ship's stability recovery arm curve based on the ship's real-time motion state and ice accumulation distribution, and then process it to obtain the dynamic stability curve. The stability assessment module is used to calculate the limiting dynamic tilt angle and maximum dynamic tilt arm under different icing conditions based on the dynamic stability curve, and to solve the limiting wind speed and corresponding wind level that the ship can withstand under different icing conditions based on the calculation results, so as to comprehensively assess and determine the ultimate stability of polar ships.

[0015] A computer storage medium is also provided, which stores a computer program that can be executed by a processor, the computer program performing the extreme stability assessment method for polar ships under icing conditions described above.

[0016] The beneficial effects of this invention are as follows: This invention establishes a dynamic ice accumulation calculation model, obtains the state change parameters of the ship at each time step based on the ship's six-degree-of-freedom motion equations, and calculates the total amount of spray and ice accumulation based on this real-time motion state. This realizes the dynamic updating of ice accumulation distribution as the ship's motion state changes. Furthermore, it combines wave spray and wind-generated spray to calculate the total amount of spray, and then calculates the total amount of ice accumulation. It also solves for the ship's maximum tolerable wind speed and corresponding wind level, thus combining ship stability analysis with ice accumulation and wind waves, improving the accuracy and reliability of stability assessment. This provides a more reliable calculation method and technical support for the safety prediction and optimization of ships sailing in polar regions, and has significant engineering application value. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of the method for evaluating the ultimate stability of ships under icing conditions in polar regions, according to an embodiment of the present invention. Figure 2 This is a flowchart of the calculation process of the dynamic icing calculation model according to an embodiment of the present invention; Figure 3 This is a flowchart illustrating the dynamic icing calculation model according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a six-degree-of-freedom motion model of a ship according to an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the definition and division of ship compartments according to an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the definition of a ship model according to an embodiment of the present invention; Figure 7 This is a schematic diagram of ice accumulation distribution in an embodiment of the present invention without considering the six degrees of freedom motion of a ship; Figure 8 This is a schematic diagram of ice accumulation distribution considering the six degrees of freedom motion of a ship according to an embodiment of the present invention; Figure 9 This is a schematic diagram of droplet icing according to an embodiment of the present invention; Figure 10 This is a graph showing the icing coefficient as a function of temperature according to an embodiment of the present invention. Figure 11 This is a schematic diagram of the recovery lever arm curve according to an embodiment of the present invention; Figure 12 This is a schematic diagram illustrating the calculation of the limiting dynamic tilt angle according to an embodiment of the present invention; Figure 13 This is a schematic diagram of the output of ship stability and buoyancy data results according to an embodiment of the present invention; Figure 14 This is a schematic diagram of the system structure of the extreme stability assessment system for polar ships under ice accumulation conditions, according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] To address the shortcomings of existing technologies in combining ice accumulation and wind / wave analysis of ship stability, and inadequate analysis of the interaction between ice distribution and ship motion, this invention provides a method for assessing the ultimate stability of ships under icing conditions in polar regions. Figure 1 As shown, the method includes: S1. Obtain ship data and environmental parameters, input them into the dynamic icing calculation model, and calculate the ship's ice distribution; the dynamic icing calculation model specifically discretizes the ship into a grid, obtains the ship's real-time motion state based on the ship's six-degree-of-freedom motion equation, calculates the total amount of droplets in each grid, and integrates them to obtain the total amount and distribution of ship ice; among which, droplets include sea wave droplets and wind-generated droplets.

[0020] S2. Based on the real-time motion state of the ship and the distribution of ice accumulation on the ship, the ship's stability recovery arm curve is obtained and processed to obtain the dynamic stability curve.

[0021] S3. Calculate the limiting dynamic tilt angle and maximum dynamic tilt arm under different icing conditions based on the dynamic stability curve, and solve the limiting wind speed and corresponding wind level that the ship can withstand under different icing conditions based on the calculation results, so as to comprehensively evaluate and judge the limiting stability of polar ships.

[0022] Specifically, the calculation process of the dynamic icing calculation model is as follows: Figure 2 As shown in the flowchart, Figure 3 As shown, the model takes target ship data and environmental parameters as input and discretizes the ship's hull shape into a mesh; based on this, by establishing... Figure 4 The illustrated six-degree-of-freedom (6-DOF) motion model of the ship calculates motion state parameters such as roll, pitch, bow angles, and heave displacement at each time step under wind and wave conditions, and updates each grid cell on the hull surface based on these motion states. Furthermore, the probability of seawater droplet arrival and droplet flux at the corresponding grid cells are corrected based on the updated hull state. Under the liquid film assumption, and considering the generation, propagation, and freezing processes of droplets, the ice mass increment of each grid cell at the current time step is calculated, and this ice mass increment is accumulated with the ice accumulation result from the previous time step, thereby achieving a dynamically updated grid ice distribution that changes with the ship's motion state. Finally, the model outputs the total ice accumulation, spatial distribution of ice accumulation, and ice thickness distribution in different regions of the hull surface, reflecting the actual evolution of ice accumulation as the ship's motion state changes.

[0023] The ship data includes ship length, ship width, bow length, superstructure location and external dimensions, and environmental parameters include wind speed, ship speed, temperature, ice accumulation duration, and the angle between the heading and the wind direction.

[0024] Specifically, such as Figure 5 and Figure 6 As shown, the ship's hull shape is discretized into a mesh. Given the geometric complexity of the hull surface, a segmented simplification process is used in the calculation and analysis. Furthermore, considering that most ice accumulation is concentrated on the deck, the calculation of ice accumulation focuses on the structure above the deck. Only the shape of the ship's deck lines needs to be processed, simplifying the shape of the deck's forefront into an elliptical curve for easier calculation. The calculation formula is shown below:

[0025] In the formula: ; a is the length of the bow of the ship's deck; B is the ship's beam.

[0026] When calculating the ship's floating state under icing conditions, it is necessary to determine the impact of icing on the ship's center of gravity. This embodiment employs a numerical simulation method, using an icing calculation program to calculate the amount of ice accumulated on each discretized grid on the hull surface. The ice amounts in all discretized grids are then summed to obtain the total mass of ice accumulated on the entire ship's deck surface. The grid cell coordinates are then determined as follows: The mass of the accumulated ice is .

[0027] Specifically, the six degrees of freedom motion of a ship includes translational motion and rotational motion; among which translational motion includes translational movement. ,swing and drooping Rotational motion includes rolling. , up and down and yaw The reference point for motion is usually chosen as the ship's center of gravity. The six-degree-of-freedom equations of motion for a ship are specifically calculated based on mass, moment of inertia, center of gravity position, translational velocity, and angular velocity, determining the ship's longitudinal translation, lateral translation, vertical translation, external moments in the roll, pitch, and yaw directions. These equations can be expressed as:

[0028] In the formula: The total mass of the object; This represents the position of the center of gravity in the fixed coordinate system of the body. The polar ship motion vector, its components (where k=1, 2, 3, 4, 5, 6) represent the external moments in the longitudinal translation, lateral translation, vertical translation, roll, pitch, and yaw directions of the ship, respectively. , , This represents the translational velocity component; , , This represents the angular velocity component. The moment of inertia represents the mass, and the subscript indicates the axis of calculation.

[0029] In the formula: and Let represent the i-th mass component and its position in the fixed coordinate system of the body, respectively. This represents the total number of mass components.

[0030] In this embodiment, based on the ship's six-degree-of-freedom motion equations, the state change parameters of the ship at each time step can be calculated to characterize the ship's instantaneous motion state. These motion state parameters serve as input conditions for the subsequent dynamic update of ice accumulation distribution, thereby achieving dynamic updating of ice accumulation distribution as the ship's motion state changes. Specifically, in the actual verification experiment, conditions such as wind speed of 20.9 m / s, ship speed of 12.9 m / s, seawater density of 34‰, and the angle between the heading and the wind / waves of 0° were selected. The resulting ice accumulation distributions without considering the ship's six-degree-of-freedom motion and those considering the ship's six-degree-of-freedom motion based on the method of this embodiment are as follows: Figure 7 and Figure 8 As shown.

[0031] Specifically, the ship's center of gravity position is calculated by integrating the vertical, horizontal, and lateral horizontal ice accumulation center of gravity positions of each grid. This results in the ship's center of gravity coordinates under icing conditions. It can be represented as:

[0032] Vertical ice accumulation is mainly concentrated on open decks and superstructures, and its center of gravity can be represented as follows:

[0033] Among them, the horizontal ice accumulation is mainly concentrated in the beginning and end areas of the upper structure, and its center of gravity can be represented as:

[0034] Lateral horizontal ice accumulation is mainly concentrated on both sides of the hull and the sides of the superstructure, caused by lateral wave action. Its center of gravity can be represented as:

[0035] In addition, the total amount of droplets is specifically calculated by adding the amount of droplets that freeze into ice, the amount of droplets that form a brine film, and the amount of droplets that evaporate; it can be expressed as:

[0036] In the formula: Total droplet count; The amount of droplets that freeze into ice; The amount of droplets that form a saline film; This refers to the amount of droplets that evaporated.

[0037] The amount of droplets that freeze into ice is specifically calculated based on droplet flux and freezing coefficient; specifically, such as Figure 9 As shown, when a ship is sailing in the polar regions, the low temperatures cause some of the droplets landing on the ship's deck to freeze rapidly into ice, while the rest form a brine film. To describe this process, this embodiment introduces an icing coefficient n, which ranges from 0 to 1, representing the proportion of the frozen portion. The relationship between its value and temperature change is as follows: Figure 10 As shown, its calculation formula can be expressed as:

[0038] In the formula: The density of the ice is [value missing]. The derivative of ice thickness with respect to time can be expressed as the rate of increase in ice thickness. , .

[0039] The droplet flux includes wave droplet volume and wind-generated droplet volume; the wave droplet volume is calculated based on the height of the wave droplet above the deck, the significant wave height, and the relative speed between the ship and the wave, while the wind-generated droplet volume is calculated based on the significant wave height.

[0040] Specifically, sea spray volume represents the distribution of spray generated by the collision of waves with the hull during ship navigation, and its calculation formula is as follows:

[0041] In the formula: The height of sea spray above the deck; For the sake of righteousness, the waves rise high; The relative speed between the ship and the waves.

[0042] Meanwhile, to predict the landing point of sea spray on the deck, it is necessary to solve its equations of motion to obtain its trajectory. The equations of motion for sea spray are as follows:

[0043] In the formula: The speed at which the droplets reach the surface of the ship; This is the drag coefficient; Diameter of droplets; air density; The density of the salt water; The wind speed is at a height of 10 meters.

[0044] Specifically, the formula for calculating the amount of wind-generated droplets is as follows:

[0045] In the formula: and This is an empirical constant.

[0046] Specifically, the ice formation process obeys both the laws of conservation of mass and energy, and the energy balance needs to consider four main heat exchange fluxes: sensible heat flux, etc. Evaporative heat flux The heat released when droplets reach equilibrium temperature and radiative heat flux In this embodiment, the freezing coefficient is specifically calculated based on the heat balance equation and the temperature at the interface between the brine film and the air, as well as the air temperature. The heat balance equation is expressed as follows:

[0047]

[0048]

[0049] but:

[0050] In the formula: For conduction heat flux; Latent heat flux; The latent heat of ice melting; The interface distribution coefficient; The heat transfer coefficient; Temperature at the interface between the salt water film and air; Air temperature; Atmospheric pressure; It is the saturated vapor pressure; Relative humidity of the air; The specific heat capacity of seawater; The temperature of the droplet; It is the Stefan-Boltzmann constant; This is the linearization constant.

[0051] Specifically, in step S2, the ship's stability recovery arm curve is calculated using the NAPA stability calculation module. The recovery arm curve output by NAPA is processed and converted into the corresponding dynamic stability curve as the basic data for dynamic stability assessment; such as Figure 11 The figure shown is a schematic diagram of the recovery lever arm curve according to an embodiment of the present invention.

[0052] Specifically, in step S3, the dynamic stability of the ship is calculated and analyzed using the limiting dynamic tilt angle evaluation method. Preferably, as follows: Figure 12 As shown, the initial point A is the abscissa position corresponding to the resonance angle; point B is set by moving 57.3° from point A along the positive direction of the abscissa, and the tangent AC of the dynamic stability curve is drawn with point A as the tangent point. The abscissa corresponding to the intersection point C of the tangent and the curve is the limiting dynamic tilt angle; then, a vertical line is drawn through point B and intersects the tangent AC at point D. The length of line segment BD is the maximum dynamic tilt arm that the ship can withstand under this working condition.

[0053] Specifically, the maximum dynamic tilting moment that a ship can withstand is calculated based on its displacement and maximum dynamic tilting arm, using the following formula:

[0054] In the formula: The maximum dynamic tilting moment that the ship can withstand; This refers to the ship's displacement under the corresponding operating conditions; The maximum dynamic tilting arm that the ship can withstand.

[0055] In addition, the formula for calculating the maximum gust pressure that a ship can withstand is as follows:

[0056] In the formula: The gust pressure that a ship can withstand; The height of the ship's area center above the waterline; For the ship's draft.

[0057] Finally, the corresponding wind pressure calculation table was consulted to obtain the relevant information. The value is taken, and the limiting wind pressure is calculated accordingly. This is then used to further calculate the limiting wind level and limiting wind speed. The formula for calculating the limiting wind pressure is shown below:

[0058] By consulting the Beaufort scale based on the ultimate wind pressure, the ultimate wind level and corresponding ultimate wind speed that the ship can withstand under the corresponding calculation conditions can be obtained, thus enabling a comprehensive assessment and determination of the ultimate stability of polar vessels. In this embodiment, the schematic diagram of the output of the obtained ship stability and buoyancy data is shown below. Figure 13 As shown.

[0059] Furthermore, this embodiment of the invention also provides a system for assessing the ultimate stability of ships under icing conditions in polar regions, used to implement the method for assessing the ultimate stability of ships under icing conditions in polar regions described in this embodiment, such as... Figure 14 As shown, the system includes: The ice accumulation calculation module is used to acquire ship data and environmental parameters, input them into a dynamic ice accumulation calculation model, and calculate the ship's ice accumulation distribution. Specifically, the dynamic ice accumulation calculation model discretizes the ship into a grid, obtains the ship's real-time motion state based on the ship's six-degree-of-freedom motion equations, calculates the total amount of spray in each grid, and integrates them to obtain the total amount and distribution of ship ice accumulation. Among them, spray includes sea spray and wind-generated spray. The processing module is used to obtain the ship's stability recovery arm curve based on the ship's real-time motion state and ice accumulation distribution, and then process it to obtain the dynamic stability curve. The stability assessment module is used to calculate the limiting dynamic tilt angle and maximum dynamic tilt arm under different icing conditions based on the dynamic stability curve, and to solve the limiting wind speed and corresponding wind level that the ship can withstand under different icing conditions based on the calculation results, so as to comprehensively assess and determine the ultimate stability of polar ships.

[0060] The various modules or mechanisms of the system are mainly used to implement the various steps of the above method embodiments, and will not be described in detail here.

[0061] Finally, this embodiment also provides a computer storage medium storing a computer program that can be executed by a processor, the computer program executing the extreme stability assessment method for polar ships under icing conditions described above.

[0062] This invention establishes a dynamic icing calculation model. By obtaining the ship's state change parameters at each time step based on the ship's six-degree-of-freedom motion equations, and calculating the total amount of spray and ice based on this real-time motion state, it realizes the dynamic updating of ice distribution as the ship's motion state changes. Furthermore, it combines wave spray and wind-generated spray to calculate the total amount of spray, and then calculates the total amount of ice. It also solves for the ship's maximum tolerable wind speed and corresponding wind level, thus combining ship stability analysis with ice accumulation and wind waves, improving the accuracy and reliability of stability assessment. This provides a more reliable calculation method and technical support for the safety prediction and optimization of ships sailing in polar regions, and has significant engineering application value.

[0063] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0064] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0065] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for assessing the ultimate stability of ships under polar ice conditions, characterized in that, The method includes: Ship data and environmental parameters are acquired and input into a dynamic icing calculation model to calculate the ship's ice distribution. Specifically, the dynamic icing calculation model discretizes the ship into a grid, obtains the ship's real-time motion state based on the ship's six-degree-of-freedom motion equations, calculates the total amount of droplets in each grid, and integrates them to obtain the total amount and distribution of ship ice. Droplets include wave droplets and wind-generated droplets. Based on the ship's real-time motion state and ice accumulation distribution, the ship's stability recovery arm curve is obtained and processed to obtain the dynamic stability curve; Based on the dynamic stability curve, the limiting dynamic tilt angle and maximum dynamic tilt arm under different icing conditions are calculated. Based on the calculation results, the limiting wind speed and corresponding wind level that the ship can withstand under different icing conditions are solved, and the limiting stability of polar ships is comprehensively evaluated and judged.

2. The method for assessing the ultimate stability of polar ships under ice accumulation conditions according to claim 1, characterized in that, The ship data includes ship length, ship width, bow length, superstructure location and external dimensions; the environmental parameters include wind speed, ship speed, temperature, ice accumulation duration, and the angle between the heading and the wind direction.

3. The method for assessing the ultimate stability of polar ships under ice accumulation conditions according to claim 1, characterized in that, The six degrees of freedom motion of a ship includes translational motion and rotational motion; translational motion includes translation, rolling, and heaving, while rotational motion includes roll, pitch, and yaw. The equations of motion for the six degrees of freedom of a ship are specifically calculated based on mass, moment of inertia, center of gravity position, translational velocity, and angular velocity to determine the ship's longitudinal translation, lateral translation, vertical translation, external moment in the roll direction, external moment in the pitch direction, and external moment in the yaw direction.

4. The method for assessing the ultimate stability of polar ships under icing conditions according to claim 1, characterized in that, The total amount of droplets is calculated by adding the amount of droplets that freeze into ice, the amount of droplets that form a brine film, and the amount of droplets that evaporate. The amount of droplets that freeze into ice is specifically calculated based on droplet flux and freezing coefficient; The droplet flux includes wave droplet volume and wind-generated droplet volume; the wave droplet volume is calculated based on the height of the wave droplet above the deck, the significant wave height, and the relative speed between the ship and the wave, while the wind-generated droplet volume is calculated based on the significant wave height.

5. The method for assessing the ultimate stability of polar ships under icing conditions according to claim 3, characterized in that, The ship's center of gravity position is calculated by integrating the vertical, horizontal, and lateral ice accumulation center of gravity positions of each grid.

6. The method for assessing the ultimate stability of polar ships under ice accumulation conditions according to claim 4, characterized in that, The freezing coefficient is specifically calculated based on the heat balance equation and the temperature at the interface between the brine film and the air, as well as the air temperature.

7. The method for assessing the ultimate stability of polar ships under icing conditions according to claim 1, characterized in that, The ship's stability recovery arm curve is specifically calculated using the NAPA stability calculation module; The limiting dynamic tilt angle is specifically determined by taking the abscissa position corresponding to the resonance angle as the initial point A, moving a certain distance from point A along the positive direction of the abscissa to set point B, and drawing the tangent AC of the dynamic stability curve with point A as the tangent point. The abscissa corresponding to the intersection point C of the tangent line and the dynamic stability curve is the limiting dynamic tilt angle. The maximum dynamic tilt arm is determined by drawing a vertical line through point B that intersects the tangent AC at point D. The length of line segment BD is the maximum dynamic tilt arm.

8. The method for assessing the ultimate stability of polar ships under icing conditions according to claim 1, characterized in that, The maximum wind speed and corresponding wind class that a ship can withstand are calculated based on the ship's displacement and maximum dynamic tilting arm. The maximum dynamic tilting moment is calculated based on the maximum dynamic tilting moment, the height of the ship's center of area above the waterline, and the ship's draft. The ultimate wind pressure is then calculated based on the maximum wind pressure. By referring to the Beaufort scale table based on the ultimate wind pressure, the ultimate wind class and corresponding ultimate wind speed that the ship can withstand under the corresponding calculation conditions can be obtained.

9. A system for assessing the ultimate stability of ships under polar ice conditions, characterized in that, The system includes: The ice accumulation calculation module is used to acquire ship data and environmental parameters, input them into a dynamic ice accumulation calculation model, and calculate the ship's ice accumulation distribution. Specifically, the dynamic ice accumulation calculation model discretizes the ship into a grid, obtains the ship's real-time motion state based on the ship's six-degree-of-freedom motion equations, calculates the total amount of spray in each grid, and integrates them to obtain the total amount and distribution of ship ice accumulation. Among them, spray includes sea spray and wind-generated spray. The processing module is used to obtain the ship's stability recovery arm curve based on the ship's real-time motion state and ice accumulation distribution, and then process it to obtain the dynamic stability curve. The stability assessment module is used to calculate the limiting dynamic tilt angle and maximum dynamic tilt arm under different icing conditions based on the dynamic stability curve, and to solve the limiting wind speed and corresponding wind level that the ship can withstand under different icing conditions based on the calculation results, so as to comprehensively assess and determine the ultimate stability of polar ships.

10. A computer storage medium, characterized in that, It contains a computer program that can be executed by a processor, which performs the method for assessing the ultimate stability of polar ships under icing conditions as described in any one of claims 1-8.

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