A FPSO navigation sea condition modeling method based on Modelica

Abstract

This invention belongs to the field of electronic digital data processing and discloses a Modelica-based method for modeling FPSO navigation sea conditions. The method includes using the Modelica language to separately model a self-propulsion resistance model and a sea environment model; modeling the self-propulsion resistance model to obtain hull resistance; modeling the sea environment model to obtain total added resistance; and summing the hull resistance and total added resistance to obtain the total navigation resistance of the FPSO. This method can effectively cope with complex ocean environments and utilize Modelica's dynamic simulation tools in FPSO design. It can accurately model and analyze the resistance changes of a self-propelled FPSO under various sea conditions, taking into account multiple variables such as wind speed, wave height, temperature, and salinity, and simulating its dynamic behavior during navigation and operation.

Description

Technical Field

[0001] The invention belongs to the field of electronic digital data processing, and in particular relates to a FPSO navigation sea condition modeling method based on Modelica. Background Art

[0002] FPSOs (Floating Production Storage and Offloading) are critical equipment widely used in offshore oil and gas production. As floating platforms that integrate oil and gas processing, storage, and transportation, FPSOs operate in harsh marine environments and are significantly affected by external factors such as wind and waves. Therefore, accurately analyzing the resistance experienced by FPSOs during navigation and operation is crucial for their design, operation, and maintenance.

[0003] The Modelica language unifies various multi-domain unified modeling mechanisms in principle, directly supports block diagram-based modeling, object-oriented modeling, and component-oriented modeling. Through the generalized Kirchhoff network mechanism based on ports and connections, it can simultaneously describe mechanical, hydraulic, and control systems, providing an ideal platform for multi-domain coupled modeling of resistance and sea environment systems. Summary of the Invention

[0004] This paper provides a Modelica-based method for modeling FPSO navigation sea conditions. This method effectively addresses complex marine environments and utilizes the Modelica language's dynamic simulation tools in FPSO design. It accurately models and analyzes the resistance changes of a self-propelled FPSO under various sea conditions, taking into account multiple variables such as wind speed, wave height, temperature, and salinity, and simulating its dynamic behavior during navigation and operation.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: a method for modeling FPSO navigation sea conditions based on Modelica, characterized in that: the method comprises using the Modelica language to model a self-propulsion resistance model and a sea condition environment model respectively; after modeling the self-propulsion resistance model, the hull resistance is obtained; after modeling the sea condition environment model, the total additional resistance is obtained; the hull resistance and the total additional resistance are added to obtain the total navigation resistance of the FPSO vessel; the method comprises the following steps:

[0006] S1: Build a ship self-propulsion resistance model to obtain the hull resistance, which is calculated as follows:

[0007] (1)

[0008] Among them, R t is the hull resistance, R f is the friction resistance, k1 is the ship type coefficient, R app is the accessory resistance, Rw is the wave resistance, R b is the attached resistance, R tr is the fluid resistance, R a is additional resistance;

[0009] S2: Build a sea condition model to obtain the total additional resistance, which is calculated as follows:

[0010] (2)

[0011] in, is the total additional resistance, is wind resistance, Adding resistance to waves, is additional sea resistance;

[0012] S3: Add the hull resistance obtained in step S1 and the total additional resistance obtained in step S2 to obtain the total navigation resistance of the FPSO vessel.

[0013] Preferably, the friction resistance R in step S1 f The calculation formula is:

[0014] (3)

[0015] Where V is the ship speed, ρ is the seawater density, C f is the friction resistance coefficient, S wt is the wetted surface area of ​​the hull.

[0016] Preferably, the accessory resistance R in step S1 app The calculation formula is:

[0017] (4)

[0018] Where V is the ship speed, ρ is the seawater density, S k2 is the wetted surface area of ​​the external attachment, C f is the friction resistance coefficient, n Bt is the number of bow thrusters, d is the diameter of the thruster, C Bot is the thruster drag coefficient.

[0019] Preferably, the wave resistance R in step S1 w The calculation formula is:

[0020] (5)

[0021] Among them, c1, c2, and c5 are correction coefficients related to hull characteristics, c1 is the wave resistance coefficient, c2 is the wave direction coefficient, c5 is the ship speed coefficient, Vol is the displacement volume, ρ is the seawater density, m1 is the exponential decay part that controls the wave resistance, m2 is the fluctuation term in the wave resistance adjustment, and F n is the Froude number of the ship, g is the acceleration due to gravity, and λ is the wavelength.

[0022] Preferably, the attached resistance R in step S1 b The calculation formula is:

[0023] (6)

[0024] Among them, P b is the resistance coefficient related to the appendage, F n is the Froude number of the ship, g is the acceleration of gravity, ρ is the density of seawater, A b is the wet surface area of ​​the appendage.

[0025] Preferably, the fluid resistance R in step S1 tr The calculation formula is:

[0026] (7)

[0027] Where ρ is the seawater density, V is the ship speed, and A tr is the surface area of ​​the towed object, and c6 is the drag coefficient.

[0028] Preferably, the additional resistance R in step S1 a The calculation formula is:

[0029] (8)

[0030] Where ρ is the seawater density, V is the ship speed, S w is the windward area, is the air resistance coefficient.

[0031] Preferably, the wind resistance in step S2 The calculation formula is:

[0032] (9)

[0033] (10)

[0034] (11)

[0035] (12)

[0036] (13)

[0037] (14)

[0038] Where V is the ship speed, is the wind speed, β is the relative angle of the wind, is the relative wind speed, is the relative wind direction angle, CDL is the drag coefficient, S w is the windward area, is relative to the frontal area S w The headwind drag coefficient, is the windward area of ​​the ship's side, is the air density, is the hull shape coefficient, is the crossbeam drag coefficient.

[0039] Preferably, the wave additional resistance in step S2 The calculation formula is:

[0040] (15)

[0041] Among them, ρ is the density of seawater, g is the acceleration of gravity, H is the effective wave height, b is the hull width, is the waterline length of the hull.

[0042] Preferably, the additional sea resistance in step S2 The calculation formula is:

[0043] (16)

[0044] (17)

[0045] (18)

[0046] (19)

[0047] (20)

[0048] (twenty one)

[0049] (twenty two)

[0050] in, is the total resistance based on standard seawater density and viscosity, ρ is the seawater density, is the standard seawater density, is the friction resistance term, is the standard friction coefficient, is the friction coefficient under the current sea conditions, S wt is the wet surface area of ​​the hull, V is the ship speed, is the Reynolds number under current conditions, is the Reynolds number under standard conditions, v is the kinematic viscosity of seawater, is the kinematic viscosity under standard conditions, is the waterline length of the hull.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. Modeling with the Modelica language enables unified modeling and simulation of the FPSO system's marine environment and navigation resistance in different fields. The non-causal nature of the Modelica language makes coupling between models more flexible, improving the model's reusability and reconfigurability.

[0053] 2. Through FPSO model simulation, engineers can optimize the FPSO's hull shape and structural configuration during the design phase to reduce resistance and improve energy efficiency. Furthermore, the simulation model can be used for FPSO operation management, helping to predict and analyze operational performance under extreme sea conditions, thereby ensuring the long-term safety and economic viability of the system.

[0054] 3. This invention introduces a navigation resistance model and a sea environment model to describe in detail the changes in a ship's navigation resistance under complex sea conditions. By inputting ship geometry (such as length, draft, and beam) and sea environment parameters (such as wind speed, wave height, and wave period), the model outputs real-time performance parameters such as total resistance, speed, and acceleration, thereby helping to optimize the ship's operating efficiency. DETAILED DESCRIPTION

[0055] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] The present invention provides a technical solution: a method for modeling FPSO navigation sea conditions based on Modelica, the method comprising: using the Modelica language to respectively model a self-propulsion resistance model and a sea condition environment model; after modeling the self-propulsion resistance model, a hull resistance is obtained; after modeling the sea condition environment model, a total additional resistance is obtained; and the hull resistance and the total additional resistance are added to obtain a total navigation resistance of the FPSO vessel. The method comprises the following steps:

[0057] S1: Build a ship self-propulsion resistance model to obtain the hull resistance, which is calculated as follows:

[0058] (1)

[0059] Among them, R t is the hull resistance, R f is the friction resistance, k1 is the ship type coefficient, which is related to the FPSO hull characteristics and operating sea conditions, R app is the accessory resistance, R w is the wave resistance, R b is the attached resistance, R tr is the fluid resistance, R a is additional resistance;

[0060] The ship resistance optimization model, as the core model for analyzing the navigation resistance of self-propelled FPSOs, provides resistance analysis for complex sea conditions and offers optimization recommendations for hull design and operation. By calculating friction resistance, appendage resistance, wave resistance, and other factors, combined with sea state parameters, it optimizes the FPSO's resistance under different operating conditions, ultimately improving the FPSO's navigation efficiency at sea and reducing energy consumption.

[0061] In the resistance calculation process, the Holtrop method effectively describes the hull resistance components, which include linearized resistance components such as friction resistance and appendage resistance. Wave resistance is also introduced into the resistance model to obtain the resistance model of the self-propelled FPSO.

[0062] S2: Build a sea condition model to obtain the total additional resistance, which is calculated as follows:

[0063] (2)

[0064] in, is the total additional resistance, is wind resistance, Adding resistance to waves, is additional sea resistance;

[0065] By accurately modeling factors such as wind, waves and sea conditions, and dynamically calculating the total additional resistance to the hull under different sea conditions, combined with the geometric structure of the FPSO hull and sea condition parameters, optimal control of the ship's resistance under different operating conditions is achieved, ensuring that the FPSO has optimal navigation efficiency and stability in a changing marine environment.

[0066] The sea condition model uses parameters such as ship speed, wind speed, wave height, and wave period as inputs. By selecting an appropriate calculation model, it estimates the forces acting on the FPSO in real time under varying sea conditions. The model's input data not only considers the physical characteristics of the hull (such as beam, draft, and wetted surface area), but also incorporates external environmental factors such as air and seawater density, wind speed and direction, and wave characteristics. Based on these inputs, the model simulates the resistance trends of the FPSO under various sea conditions, providing critical insights for the self-propulsion system.

[0067] S3: Add the hull resistance obtained in step S1 and the total additional resistance obtained in step S2 to obtain the total navigation resistance of the FPSO vessel.

[0068] In step S1, the friction resistance R f The calculation formula is:

[0069] (3)

[0070] Where V is the ship speed, ρ is the seawater density, C f is the friction resistance coefficient, S wt is the wet surface area of ​​the hull. Frictional resistance is the main resistance component generated by the relative motion between the hull surface and seawater.

[0071] The accessory resistance R in step S1 app The calculation formula is:

[0072] (4)

[0073] Where V is the ship speed, ρ is the seawater density, S k2 is the wetted surface area of ​​the external attachment, C f is the friction resistance coefficient, n Bt is the number of bow thrusters, d is the diameter of the thruster, C Bot is the thruster drag coefficient. The accessory resistance takes into account the effects of various exposed structures on the ship, such as the thruster, propeller shaft bracket, etc.

[0074] The wave resistance R in step S1 w The calculation formula is:

[0075] (5)

[0076] Among them, c1, c2, and c5 are correction coefficients related to hull characteristics, c1 is the wave resistance coefficient, c2 is the wave direction coefficient, c5 is the ship speed coefficient, Vol is the displacement volume, ρ is the seawater density, m1 is the exponential decay part that controls the wave resistance, m2 is the fluctuation term in the wave resistance adjustment, and F n is the Froude number of the ship, g is the acceleration due to gravity, and λ is the wavelength. Wave drag is the hydrodynamic reaction force caused by the motion of the ship in the waves.

[0077] The attached resistance R in step S1 b The calculation formula is:

[0078] (6)

[0079] Among them, P b is the resistance coefficient related to the appendage, F n is the Froude number of the ship, g is the acceleration of gravity, ρ is the density of seawater, A b is the wet surface area of ​​the appendage. Appendage resistance is mainly caused by the non-smooth parts of the hull (such as ballast tanks, keels, rudders and other appendage structures). This part of the resistance is usually estimated using the above empirical formula.

[0080] In step S1, the fluid resistance R tr The calculation formula is:

[0081] (7)

[0082] Where ρ is the seawater density, V is the ship speed, and A tr is the surface area of ​​the towed object, and c6 is the drag coefficient. Fluid drag refers to the resistance between the hull and the water due to hydrodynamic effects, particularly the effects of factors such as the hull's geometry, fluid viscosity, and flow separation.

[0083] Additional resistance R in step S1 a The calculation formula is:

[0084] (8)

[0085] Where ρ is the seawater density, V is the ship speed, S w is the windward area, is the air resistance coefficient. Additional drag is the extra resistance caused by special fluid conditions (such as variations in seawater temperature and salinity), which is particularly significant in extreme sea conditions. In some embodiments, additional drag also includes corrections for temperature, salinity, and density variations.

[0086] These responsive ship resistances are embedded into the resistance optimization model through text modeling to simulate the FPSO's resistance changes under complex sea conditions. By simulating the self-propelled FPSO resistance optimization model, the FPSO's resistance minimization requirements under various operating conditions are met, achieving optimal energy efficiency allocation and global control.

[0087] Step S2 Stroke Resistance The calculation takes into account the influence of hull shape and wind direction on wind resistance. The calculation formula is:

[0088] (9)

[0089] (10)

[0090] (11)

[0091] (12)

[0092] (13)

[0093] (14)

[0094] Where V is the ship speed, is the wind speed, β is the relative angle of the wind, is the relative wind speed, is the relative wind direction angle, CDL is the drag coefficient, S w is the windward area, is relative to the frontal area S w The headwind drag coefficient, is the windward area of ​​the ship's side, is the air density, is the hull shape coefficient, The wind resistance is mainly affected by the relative angle and wind speed, which is affected by the ship speed V and wind speed. And the relative angle β of the wind, calculate the two relative velocity components V1 and V 2。

[0095] Wave additional resistance in step S2 The calculation formula is:

[0096] (15)

[0097] Among them, ρ is the density of seawater, g is the acceleration of gravity, H is the effective wave height, b is the hull width, is the waterline length of the hull. The modeling formula for wave additional resistance adopts the STAwave method, where The term represents the effect of the hull shape ratio on the wave added resistance. The square term of the effective wave height H shows that the wave height has a significant effect on the resistance. The higher the wave, the greater the resistance.

[0098] Additional sea resistance in step S2 The calculation formula is:

[0099] (16)

[0100] (17)

[0101] (18)

[0102] (19)

[0103] (20)

[0104] (twenty one)

[0105] (twenty two)

[0106] in, is the total resistance based on standard seawater density and viscosity, ρ is the seawater density, is the standard seawater density, is the friction resistance term, is the standard friction coefficient, is the friction coefficient under the current sea conditions, S wt is the wet surface area of ​​the hull, V is the ship speed, is the Reynolds number under current conditions, is the Reynolds number under standard conditions, v is the kinematic viscosity of seawater, is the kinematic viscosity under standard conditions, is the waterline length of the hull. The modeling method of the additional sea state resistance mainly considers the impact of changes in density and friction coefficient caused by temperature and salinity on the hull resistance.

[0107] The above modeling of sea conditions further accurately estimates the additional sea resistance by calculating the effects of seawater density and viscosity on frictional resistance. These parameters are typically affected by sea temperature and salinity. By inputting wind speed, wave height, and hull parameters into the model, the output calculates the resistance under variable sea conditions.

[0108] The Holtrop method is used in the modeling of the ship's self-propulsion resistance model. It is more suitable for the ship design stage and is used to evaluate the resistance characteristics of different hull geometry design schemes. The Holtrop method takes into account more hull design factors and is suitable for use in design optimization and performance evaluation. The sea condition environment model is suitable for navigation analysis under specific sea conditions, especially under conditions of strong winds and waves, and significant changes in temperature and salinity. It is used to evaluate the impact of environmental factors on ship performance and is suitable for dynamically adjusting speed and route during the operation phase to ensure safety and economy. In practical applications, the sea condition model and the Holtrop method can be used complementary. The sea condition model provides a real-time assessment of the impact on the environment during ship operation, while the Holtrop law helps optimize the hull shape and reduce the total resistance during the design phase, thereby improving ship performance.

[0109] Example: A simulation simulates a ship sailing long distances in open waters, encountering strong winds and waves. The design goal is to analyze the ship's sailing resistance through simulation, evaluate its sailing performance under different speeds and sea conditions, and optimize its performance based on the simulation results.

[0110] The specific parameter calculation and modeling process are as follows:

[0111] Hull waterline length =100 m, hull width b = 20 m, draft d = 8 m, hull wet surface area S wt =1500 square meters, displacement mass=50000 tons;

[0112] wind speed =15 meters / second, wave height H=3 meters, wave period =7 seconds, seawater density ρ = 1025 kg / m3, temperature T = 15 degrees Celsius, salinity S = 35 g / L;

[0113] Speed ​​V = 12 m / s;

[0114] 1. Model the ship's self-propulsion resistance and use the Holtrop method to calculate the ship's hull resistance at different speeds. The hull resistance includes friction resistance, attachment resistance, wave resistance, appendage resistance, fluid resistance, and air resistance:

[0115] (1) Friction resistance R f Calculation:

[0116] ;

[0117] Use wet surface area S wt =1500, speed V=12, friction coefficient C f =0.002 for calculation,

[0118] ;

[0119] (2) Accessory resistance R app Calculation:

[0120] ;

[0121] Wetted surface area S of external accessories k2 =5 m², number of bow thrusters n Bt =4, thruster diameter d=0.3 m, thruster drag coefficient C Bto =0.8,

[0122] ;

[0123] ;

[0124] ;

[0125] ;

[0126] (3) Wave resistance R w Calculation:

[0127] The wave resistance is calculated using the aforementioned model,

[0128] ;

[0129] (4) Attachment resistance R b Calculation:

[0130] ;

[0131] Cross-sectional area of ​​the appendage A b =20 square meters, gravitational acceleration g=9.81m / s², the resistance coefficient related to the appendage P b =0.6,

[0132] ;

[0133] ;

[0134] ;

[0135] ;

[0136] ;

[0137] (5) Fluid resistance R tr Calculation:

[0138] ;

[0139] The surface area of ​​the towed object Atr = 40 square meters, the drag coefficient c6 = 0.8,

[0140] ;

[0141] (6) Additional resistance R a Calculation:

[0142] ;

[0143] Frontal area S w =300, air resistance coefficient =0.8,

[0144] ;

[0145] Substitute all resistance terms into the hull resistance formula:

[0146] ;

[0147] ;

[0148] 2. Model the sea environment to obtain the total additional resistance , calculate wind resistance by inputting sea condition parameters , additional wave resistance , additional sea resistance :

[0149] (1) Wind resistance Calculation:

[0150] ;

[0151] Relative wind speed =15m / s, relative wind direction angle =45°, drag coefficient CDL=0.8, frontal area S w =300m 2 , the ship's side windward area =300m 2 , air density =1.225kg / m 3 , hull shape coefficient =0.1, beam drag coefficient =1.0, drag coefficient CDL=0.8,

[0152] ;

[0153] (2) Additional wave resistance Calculation:

[0154] ;

[0155] ρ=1025, H=3, b=20, =100

[0156] ;

[0157] (3) Additional sea resistance Calculation:

[0158] ;

[0159] =8000N, =5000N, varies according to temperature and salinity,

[0160] ;

[0161] Substitute all resistance terms into the total additional resistance formula of the hull sea state environment model:

[0162] ;

[0163] ;

[0164] ;

[0165] In this embodiment, the resistances calculated based on the sea environment model and the Holtrop method are:

[0166] Total additional resistance of sea state environment model: 39166.87 N

[0167] Holtrop hull resistance: 736693.85 N

[0168] Therefore, the total navigation resistance of the FPSO ship is 39166.87N+736693.85N=775860.72N

[0169] Analysis of the sources of resistance differences:

[0170] The sea-state environmental model primarily focuses on the external effects of environmental factors on the ship (such as wind, waves, temperature, and salinity), specifically calculating the resistance caused by wind speed, waves, and temperature-salinity effects. The contribution of these external factors to hull resistance is particularly significant in adverse sea conditions, but it does not consider the internal geometry of the hull or specific design factors. Therefore, the total resistance value of the sea-state environmental model is relatively small.

[0171] The Holtrop method is a more comprehensive resistance calculation method. It not only considers external environmental resistance (such as air resistance), but also includes multiple factors such as hull friction resistance, appendage resistance, wave resistance, and drag resistance. The Holtrop method considers factors such as the hull's geometric design, additional equipment, and appendages, making the resistance calculation more comprehensive. As a result, the hull resistance calculated by the Holtrop method is significantly higher than the total added resistance of the sea condition model.

[0172] The sea condition environment model provides the direct impact of the environment on the ship's navigation. It is suitable for real-time evaluation of the additional resistance brought by the external environment during navigation, which helps to control the navigation and ensure the safety of the ship.

[0173] The Holtrop method is more suitable for use in the design phase. It helps optimize the hull structure and appendage arrangement through comprehensive resistance assessment, provides a reliable hull resistance benchmark, and optimizes the overall performance of the ship.

[0174] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A FPSO navigation sea condition modeling method based on Modelica, characterized by: The modeling method comprises using the Modelica language to respectively model a self-propulsion resistance model and a sea environment model; after modeling the self-propulsion resistance model, a hull resistance is obtained; after modeling the sea environment model, a total additional resistance is obtained; and the hull resistance and the total additional resistance are added to obtain a total navigation resistance of the FPSO vessel. The modeling method comprises the following steps: S1: Build a ship self-propulsion resistance model to obtain the hull resistance, which is calculated as follows: （1） Among them, R t is the hull resistance, R f is the friction resistance, k1 is the ship type coefficient, R app is the accessory resistance, R w is the wave resistance, R b is the attached resistance, R tr is the fluid resistance, R a is additional resistance; S2: Build a sea condition model to obtain the total additional resistance, which is calculated as follows: （2） in, is the total additional resistance, is wind resistance, Adding resistance to waves, is additional sea resistance; S3: Add the hull resistance obtained in step S1 and the total additional resistance obtained in step S2 to obtain the total navigation resistance of the FPSO ship; In step S1, the attached resistance R b The calculation formula is: （6） Among them, P b is the resistance coefficient related to the appendage, F n is the Froude number of the ship, g is the acceleration of gravity, ρ is the density of seawater, A b is the wet surface area of ​​the appendage; The additional resistance R in step S1 a The calculation formula is: （8） Where ρ is the seawater density, V is the ship speed, S w is the windward area, is the air resistance coefficient; The additional sea resistance in step S2 The calculation formula is: （16） （17） （18） （19） （20） （21） （22） in, is the total resistance based on standard seawater density and viscosity, ρ is the seawater density, is the standard seawater density, is the friction resistance term, is the standard friction coefficient, is the friction coefficient under the current sea conditions, S wt is the wet surface area of ​​the hull, V is the ship speed, is the Reynolds number under current conditions, is the Reynolds number under standard conditions, v is the kinematic viscosity of seawater, is the kinematic viscosity under standard conditions, is the hull waterline length; The wave resistance R in step S1 w The calculation formula is: （5） Among them, c1, c2, and c5 are correction coefficients related to hull characteristics, c1 is the wave resistance coefficient, c2 is the wave direction coefficient, c5 is the ship speed coefficient, Vol is the displacement volume, ρ is the seawater density, m1 is the exponential decay part that controls the wave resistance, m2 is the fluctuation term in the wave resistance adjustment, and F n is the Froude number of the ship, g is the acceleration due to gravity, and λ is the wavelength; The wave additional resistance in step S2 The calculation formula is: （15） Among them, ρ is the density of seawater, g is the acceleration of gravity, H is the effective wave height, b is the hull width, is the waterline length of the hull.

2. The FPSO navigation sea condition modeling method based on Modelica according to claim 1, characterized in that: In step S1, the friction resistance R f The calculation formula is: （3） Where V is the ship speed, ρ is the seawater density, C f is the friction resistance coefficient, S wt is the wetted surface area of ​​the hull.

3. The FPSO navigation sea condition modeling method based on Modelica according to claim 1, characterized in that: In step S1, the accessory resistance R app The calculation formula is: （4） Where V is the ship speed, ρ is the seawater density, S k2 is the wetted surface area of ​​the external attachment, C f is the friction resistance coefficient, n Bt is the number of bow thrusters, d is the diameter of the thruster, C Bot is the thruster drag coefficient.

4. The FPSO navigation sea condition modeling method based on Modelica according to claim 1, characterized in that: In step S1, the fluid resistance R tr The calculation formula is: （7） Where ρ is the seawater density, V is the ship speed, and A tr is the surface area of ​​the towed object, and c6 is the drag coefficient.

5. The FPSO navigation sea condition modeling method based on Modelica according to claim 1, characterized in that: The stroke resistance in step S2 The calculation formula is: （9） （10） （11） （12） （13） （14） Where V is the ship speed, is the wind speed, β is the relative angle of the wind, is the relative wind speed, is the relative wind direction angle, CDL is the drag coefficient, S w is the windward area, is relative to the frontal area S w The headwind drag coefficient, is the windward area of ​​the ship's side, is the air density, is the hull shape coefficient, is the crossbeam drag coefficient.

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