A rapid prediction system and method for deep-sea abnormal waves considering the influence of fourth-order nonlinearity

Abstract

This invention relates to the field of marine engineering technology, specifically to a rapid prediction system and method for deep-sea anomalous waves considering the effects of fourth-order nonlinearity. The invention includes a general module for predicting and analyzing anomalous waves, installed on any floating marine structure, incorporating the effects of fourth-order nonlinearity, and comprising an incident wave measurement subsystem and an anomalous wave prediction subsystem. An extended module is used to quickly and accurately predict the extreme response values ​​of a floating structure when encountering anomalous waves. Before activation, the hydrodynamic parameters of the floating structure need to be initially set based on the physical properties of the object to be protected, including a structure response subsystem. This invention adds an extended module for hydrodynamic response analysis to the general module; it monitors the sea state in the operating area in real time, extracts and processes time-domain wave signals, provides advance warning of anomalous waves, determines the extreme values ​​of the motion response of marine structures when encountering them, and provides a quantitative level of warning.

Description

Technical Field

[0001] The present invention relates to the field of marine engineering technology, and in particular to a system and method for rapid prediction of deep-sea abnormal waves taking into account fourth-order nonlinear effects. Background Art

[0002] Deep-sea abnormal waves are special single waves with a peak height significantly greater than other surrounding waves. They have the characteristics of "coming without a trace and leaving without a trace" and last for a relatively short time. They appear in any sea conditions. When they act on speeding ships and slow floating marine structures, they will cause complex hydrodynamic mechanisms, induce destructive structural damage, and even pose a life threat to working personnel.

[0003] In order to effectively detect the physical characteristics of abnormal deep-sea waves, the traditional method in the industry is to pre-place various measurement equipment in the operating sea area, such as single-point measurement devices such as buoys and lidar to collect wave data, and then extrapolate the generation probability and waveform parameters of abnormal waves in the operating sea area through statistical analysis, and then evaluate the overall safety of the deployment device based on the "design wave" criterion. This method has a large dependence on the accuracy of the original sample data. The selection of the extrapolation model and the fitting of related parameters will produce a large uncertainty in the final result. At the same time, the traditional industrial method lacks timeliness, and it is difficult to predict whether abnormal waves will appear in a short time based on real-time measured data. With the advancement of technical research, Chinese patent CN117421685A discloses a deep-sea abnormal wave rapid warning method developed based on modulation instability. This method is the first to design the first generation of rapid warning system for abnormal waves, but its internal prediction module only considers third-order nonlinearity, so it can only roughly capture the height data of abnormal waves, and there is a large error in the prediction of its wave morphology. Its fidelity is further reduced under strong nonlinearity, and the evolution distance that can be accurately predicted is also further shortened. In addition, the first-generation early warning system only relies on the relationship between the trough-to-trough period of the abnormal wave and the natural period of the floating device to determine the extreme value of the hydrodynamic response of the device, and does not conduct a specific analysis of the system motion response of the device to be protected, so there will be large errors. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a system and method for rapid prediction of deep-sea abnormal waves taking into account the influence of fourth-order nonlinearity.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A deep-sea abnormal wave rapid prediction system considering the fourth-order nonlinear effect includes the following modules:

[0007] A general module for predicting and analyzing abnormal waves. It is installed on any floating marine structure and introduces the influence of fourth-order nonlinearity. It includes an incident wave measurement subsystem and an abnormal wave prediction subsystem, where:

[0008] The incident wave measurement subsystem obtains the wave surface time history curve in real time and performs basic signal processing;

[0009] Abnormal wave prediction subsystem, which introduces the influence of fourth-order nonlinearity and predicts the wave field information of the surrounding and central areas in real time;

[0010] The extended module is used to quickly and accurately predict the extreme response of floating structures when encountering abnormal waves. Before activation, the initial setting of the hydrodynamic parameters of the floating structure needs to be performed based on the physical properties of the object to be protected, including the structural response subsystem, where:

[0011] The structural response subsystem calculates in real time the extreme values ​​of motion and force response when encountering abnormal waves, gives a more accurate warning level of possible danger, and proposes corresponding response measures.

[0012] This technical solution introduces fourth-order nonlinear effects to predict wave field information and structural responses in real time, achieves rapid and accurate prediction and risk assessment of abnormal waves, and provides important theoretical guidance and technical support for offshore operations and navigation safety. Specifically, ocean waves are often affected by many factors during their propagation and evolution, among which nonlinear effects are an important aspect. Considering the fourth-order nonlinear effects can more accurately describe the complex behavior of waves, including changes in waveforms, increases in wave heights, and interactions between waves and structures. The incident wave measurement subsystem obtains the wave surface time history curve of the waves in real time and performs basic signal processing, and analyzes and predicts the wave field information of the surrounding and central areas in real time, including accurate simulation of wave propagation, evolution, and interactions with other factors (such as wind, current, etc.). By introducing the fourth-order nonlinear effects, these complex processes can be accurately described, thereby improving the accuracy of wave prediction. The structural response subsystem in the extension module can calculate the extreme values ​​of the motion and force response of floating structures when encountering abnormal waves in real time, accurately evaluate the safety of structures under abnormal waves, and provide an important basis for the formulation of early warning and response measures. By quantitatively analyzing the extreme values ​​of the motion response of structures when encountering abnormal waves, the risk level can be accurately evaluated, and corresponding response measures and avoidance suggestions can be given to improve the safety of offshore operations and navigation and reduce the potential risks caused by abnormal waves.

[0013] In addition, the deep-sea abnormal wave rapid prediction system considering the fourth-order nonlinear effect according to the present invention also has the following additional technical features:

[0014] According to one embodiment of the present invention, the abnormal wave prediction subsystem modifies the third-order control equation and incorporates the influence of fourth-order nonlinearity to more accurately predict the waveform evolution process of the abnormal wave, reflecting its horizontal asymmetry, while increasing the spatial distance of its effective early warning, providing a longer preparation time for responding to the threat of abnormal waves.

[0015] This technical solution can better simulate and predict the waveform evolution process of abnormal waves, especially its horizontal asymmetry, by increasing the complexity and accuracy of the equations, so as to improve the effectiveness of the early warning system and provide a longer preparation time for responding to the threat of abnormal waves. Specifically, the control equation itself is a partial differential equation that describes the evolution of quantum systems and the behavior of wave functions. In oceanography or water wave physics, although it is not directly used to describe quantum phenomena, its deformation or similar form of equations is sometimes used to simulate the evolution of water waves; by modifying the third-order control equation to include the influence of fourth-order nonlinearity, it is actually to increase the complexity of the equation to better simulate and reflect the nonlinear behavior of water waves in the real world; abnormal waves often have characteristics different from conventional waves, such as higher wave heights, more complex waveforms, and possible horizontal asymmetry; by modifying the equations, more accurately simulating these characteristics, especially the horizontal asymmetry, is crucial for predicting and solving the behavior of abnormal waves; by increasing the spatial distance of effective early warning, a longer preparation time is provided for responding to the threat of abnormal waves, which is used for marine operations and navigators to take necessary measures in advance to reduce potential risks and losses.

[0016] In addition, the present invention also provides the following technical solutions:

[0017] A method for rapid prediction of deep-sea abnormal waves considering the influence of fourth-order nonlinearity comprises the following steps:

[0018] S1. The modal control equation obtained by using the general module is as follows:

[0019] (1)

[0020] Among them, formula (1) is the third-order governing equation in the spatial domain: On the basis of the above, add three items IV, V and VI. is the carrier frequency, is the carrier wave number, x is the spatial coordinate; B * is the wave envelope function B The conjugate function of ;

[0021] Introducing potential function ϕTo characterize the uniform flow in the wave field caused by the fourth-order nonlinearity, the amplitude is numerically solved by the control equations and boundary conditions composed of formula (2), formula (3) and formula (4). This uniform flow is actually closely related to the long waves generated by the non-resonant interaction of three waves:

[0022] (2)

[0023] (3)

[0024] (4)

[0025] Among them, the variable z For vertical coordinates, the fourth-order nonlinear term is incorporated into the effect of nonlinear dispersion on the evolution of anomalous waves to characterize the nonlinear hydrodynamic mechanism of irregular waves with a wider spectrum;

[0026] S2, the general module uses the correlation expression between the liquid level and the wave packet to synthesize the free wave surface and the bound wave surface at the specified position. After superposition, the two are reconstructed to obtain the time history curve of the actual wave surface. η With wave packet B The associated expression is:

[0027] (5)

[0028] (6)

[0029] (7)

[0030] Among them, the first The second term is the wavefront generated by the free wave interaction. The wavefront generated by the bound wave action has a phase that changes synchronously with the phase of the free wave;

[0031] also, η 3 is the third-order expression of the free liquid surface; η 4 is the fourth-order expression of the free liquid surface, that is, the newly added component in the wave surface reconstruction process, which not only modifies the wave surface of the second-order bound wave, that is, , and at the same time, the wavefront expression of the third-order bound wave is introduced to improve the accuracy of waveform reconstruction, that is, , and considering the influence of uniform flow caused by long waves, that is ;

[0032] S3. The control equation of the extended module regarding the motion response module of the floating marine structure is:

[0033] (8)

[0034] in, jand k The value range is 1~6. and All are the six degrees of freedom motion displacements of floating marine structures; and are the first and second order derivatives of displacement with respect to time, respectively; is the mass or moment of inertia of the structure;

[0035] In addition, hydrostatic resilience Froude-Krylov force The calculation of is obtained by integrating the static pressure and dynamic pressure on the wet surface of the floating marine structure at each moment; the abnormal wave diffraction force is recorded as , the radiation force is expressed in the time domain as the additional mass corresponding to infinite frequency , radiation recovery coefficient and memory function The expression of convolution; if there are other forces acting on the structure such as mooring force and wind force, it can be expressed as ; Vertical wave force caused by waves on deck The momentum method is used for rapid calculation. The vertical wave force is related to the deck acceleration, the hydrostatic pressure above the deck, and the rate of change of water mass.

[0036] This technical solution introduces fourth-order nonlinear effects, modifies the modal control equations, and combines wave surface reconstruction and motion response analysis of floating marine structures to achieve accurate prediction and evaluation of abnormal waves, providing important theoretical guidance and technical support for marine operations and navigation safety. Specifically, by introducing the fourth-order nonlinear effect, the complex evolution process of waves, especially the generation and propagation of abnormal waves, can be simulated and predicted more accurately. In step S1, the third-order control equation is modified and the terms related to the fourth-order nonlinearity are added to more accurately describe the nonlinear characteristics of waves. The potential function is introduced to characterize the uniform flow in the wave field caused by the fourth-order nonlinearity. This uniform flow is closely related to the long waves generated by the non-resonant interaction of three waves, further improving the accuracy of wave prediction. The wavefront reconstruction process in step S2 reconstructs the time history curve of the actual wavefront by combining the information of the free wavefront and the bound wavefront, considering not only the influence of the second-order and third-order bound waves, but also the influence of the uniform flow caused by the long waves, thereby improving the accuracy of waveform reconstruction. In step S3, the motion response of the floating marine structure is analyzed in detail. By establishing the control equation of the motion response module and considering the influence of various forces (such as hydrostatic restoring force, Froude-Krylov force, abnormal wave diffraction force, radiation force, mooring force, wind force, etc.), the motion and force response of the structure under the action of abnormal waves are accurately calculated.

[0037] In addition, the method for rapid prediction of abnormal deep-sea waves considering the influence of fourth-order nonlinearity proposed in the present invention also has the following additional technical features:

[0038] According to one embodiment of the present invention, in step S2, the predicted result of wave packet splitting during the wave group evolution of the general module captures the third-order modulation instability. After introducing the effect of the fourth-order nonlinearity, the higher-order nonlinearity has a certain inhibitory effect on the approximate coupled resonance of the free wave, resulting in the Gaussian wave packet being split into only two wave groups, and the overall propagation speed of the wave packet is reduced, showing asymmetry in the horizontal space, and the predicted result is more in line with the actual evolution process of the Gaussian wave packet.

[0039] This technical solution is based on nonlinear wave theory, especially the influence of high-order nonlinear terms on wave behavior; the introduction of fourth-order nonlinearity enables the model to more accurately describe the wave packet splitting process and the asymmetry of the wave group in horizontal space.

[0040] According to one embodiment of the present invention, in step S2, when the general module is in high sea conditions with strong nonlinearity, there is a certain functional relationship between the predicted wave surface kurtosis coefficient and the warning radius length; the predicted result is closer to the actual observation value, and the predicted effective radius length is greatly increased, which greatly improves the warning time and provides sufficient preparation time for responding to abnormal wave threats; due to the improvement in prediction accuracy, there is no strict requirement for the deployment position of the incident wave measurement subsystem in the fourth-order model, but it is still recommended that the warning radius should not be too large or too small.

[0041] This technical solution is based on the statistical characteristics of waves and the actual needs of the early warning system; by analyzing and establishing this functional relationship, the prediction method can more accurately determine the early warning radius, thereby providing a longer early warning time. This optimization of the early warning radius helps to improve the efficiency and safety of responding to abnormal wave threats.

[0042] According to an embodiment of the present invention, in step S3, the structural response subsystem of the expansion module replaces the simple method of only relying on analyzing the relationship between the abnormal trough-trough cycle and the structural resonance period for early warning, thereby improving the risk assessment method.

[0043] This technical solution is based on the principles of structural dynamics and marine engineering, especially the movement and force response of floating marine structures under abnormal wave action; by more accurately predicting the response of the structure, the risk level can be more accurately assessed, and reasonable response measures and avoidance suggestions can be given.

[0044] According to one embodiment of the present invention, in step S3, the expansion module calculates the relevant hydrodynamic coefficients of the floating marine structure to be protected in advance and stores them in the early warning database system, which is directly called when the movement and force response are actually evaluated, thereby greatly reducing the amount of calculation and improving the early warning efficiency.

[0045] This technical solution is based on the application of database technology and efficient algorithms. By pre-calculating and storing the hydrodynamic coefficients, they can be quickly called when needed, thereby accelerating the response speed of the early warning system and improving the real-time and accuracy of the early warning.

[0046] According to one embodiment of the present invention, in step S3, the extension module predicts the motion response law when encountering abnormal waves and compares it with the actual observation value; through the time curve of the two-degree-of-freedom motion of heave and pitch, in which the vertical dotted line position corresponds to the highest moment of the abnormal wave crest, the extension module effectively predicts the extreme value of the motion response of the hull when encountering abnormal waves, thereby more accurately quantifying its risk level, giving reasonable response measures and avoidance suggestions, and providing theoretical guidance and technical support for marine operations and navigation safety.

[0047] By analyzing the time history curves of the two degrees of freedom motion of heave and pitch, the expansion module of this technical solution can deeply understand the dynamic characteristics of the hull under the action of abnormal waves; heave refers to the up and down movement of the hull in the vertical direction, while pitch is the rotational movement of the hull around its longitudinal axis; the movement of the two degrees of freedom is crucial to evaluating the stability and safety of the hull; through the time history curve, key information such as the amplitude, frequency and phase of the hull motion can be observed, so as to further analyze the response law of the hull; the expansion module identifies the highest moment of the abnormal wave peak and corresponds it to the vertical dotted line position, so as to accurately capture the impact of abnormal waves on the hull motion. Rogue waves usually have higher wave heights and more complex waveforms, and their impact on the hull is more significant. By comparing the predicted results with the actual observed values, the extended module can evaluate the accuracy of the prediction model and accurately quantify the risk level of the hull when encountering rogue waves. Based on the risk level, reasonable response measures and avoidance suggestions are given, such as adjusting the navigation route, reducing the speed or taking other safety measures to minimize the potential threat of rogue waves to the hull. The entire prediction and comparison process not only provides an in-depth understanding of the motion response of the hull under the action of rogue waves, but also provides important theoretical guidance and technical support for marine operations and navigation safety.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention considers for the first time the correction effect of the fourth-order nonlinearity on the modulation instability induced by the free-wave resonant coupling, and incorporates a series of new control items by deriving the formula, taking into account the long-wave influence generated by the non-resonant interaction of three waves, effectively improving the accuracy of the model in predicting abnormal waves, increasing the radius length of the effective warning, and greatly advancing the warning time;

[0050] By adding an extended module that can perform hydrodynamic response analysis on specific marine structures on the basis of the general module; real-time monitoring of the sea conditions in the operating area, extracting and processing time-domain wave signals, accurately predicting the progress of its waveform evolution based on the improved control equation, and judging in advance the extreme values ​​of the motion response of the marine structure when it encounters its action, a more accurate quantitative level of early warning prompts can be given. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a simplified diagram of the overall logic flow of the present invention.

[0052] Figure 2 The present invention adopts a third-order model to predict wave group splitting and abnormal wave generation diagram.

[0053] Figure 3 The present invention adopts a fourth-order model to predict wave group splitting and abnormal wave generation diagram.

[0054] Figure 4 It is a comparison diagram of the functional relationship between the wave surface kurtosis coefficient and the warning radius length predicted by the prior art and the present invention in high sea conditions.

[0055] Figure 5 It is a time history curve diagram of the expansion module of the present invention for predicting the heave motion of the liquefied natural gas ship when encountering abnormal waves.

[0056] Figure 6 It is a time history curve diagram of the extended module of the present invention predicting the pitching motion of the liquefied natural gas ship when encountering abnormal waves. DETAILED DESCRIPTION

[0057] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] Example 1

[0059] like Figure 1 As shown, this embodiment provides a deep-sea abnormal wave rapid prediction system considering the fourth-order nonlinear effect, including the following modules:

[0060] A general module for predicting and analyzing abnormal waves. It is installed on any floating marine structure and introduces the influence of fourth-order nonlinearity. It includes an incident wave measurement subsystem and an abnormal wave prediction subsystem, where:

[0061] The incident wave measurement subsystem obtains the wave surface time history curve in real time and performs basic signal processing;

[0062] Abnormal wave prediction subsystem, which introduces the influence of fourth-order nonlinearity and predicts the wave field information of the surrounding and central areas in real time;

[0063] The extended module is used to quickly and accurately predict the extreme response of floating structures when encountering abnormal waves. Before activation, the initial setting of the hydrodynamic parameters of the floating structure needs to be performed based on the physical properties of the object to be protected, including the structural response subsystem, where:

[0064] The structural response subsystem calculates in real time the extreme values ​​of motion and force response when encountering abnormal waves, gives a more accurate warning level of possible danger, and proposes corresponding response measures.

[0065] This technical solution introduces fourth-order nonlinear effects to predict wave field information and structural responses in real time, achieves rapid and accurate prediction and risk assessment of abnormal waves, and provides important theoretical guidance and technical support for offshore operations and navigation safety. Specifically, ocean waves are often affected by many factors during their propagation and evolution, among which nonlinear effects are an important aspect. Considering the fourth-order nonlinear effects can more accurately describe the complex behavior of waves, including changes in waveforms, increases in wave heights, and interactions between waves and structures. The incident wave measurement subsystem obtains the wave surface time history curve of the waves in real time and performs basic signal processing, and analyzes and predicts the wave field information of the surrounding and central areas in real time, including accurate simulation of wave propagation, evolution, and interactions with other factors (such as wind, current, etc.). By introducing the fourth-order nonlinear effects, these complex processes can be accurately described, thereby improving the accuracy of wave prediction. The structural response subsystem in the extension module can calculate the extreme values ​​of the motion and force response of floating structures when encountering abnormal waves in real time, accurately evaluate the safety of structures under abnormal waves, and provide an important basis for the formulation of early warning and response measures. By quantitatively analyzing the extreme values ​​of the motion response of structures when encountering abnormal waves, the risk level can be accurately evaluated, and corresponding response measures and avoidance suggestions can be given to improve the safety of offshore operations and navigation and reduce the potential risks caused by abnormal waves.

[0066] In addition, the deep-sea abnormal wave rapid prediction system considering the fourth-order nonlinear effect according to the present invention also has the following additional technical features:

[0067] According to one embodiment of the present invention, the abnormal wave prediction subsystem modifies the third-order control equation and incorporates the influence of fourth-order nonlinearity to more accurately predict the waveform evolution process of the abnormal wave, reflecting its horizontal asymmetry, while increasing the spatial distance of its effective early warning, providing a longer preparation time for responding to the threat of abnormal waves.

[0068] This technical solution can better simulate and predict the waveform evolution process of abnormal waves, especially its horizontal asymmetry, by increasing the complexity and accuracy of the equations, so as to improve the effectiveness of the early warning system and provide a longer preparation time for responding to the threat of abnormal waves. Specifically, the control equation itself is a partial differential equation that describes the evolution of quantum systems and the behavior of wave functions. In oceanography or water wave physics, although it is not directly used to describe quantum phenomena, its deformation or similar form of equations is sometimes used to simulate the evolution of water waves; by modifying the third-order control equation to include the influence of fourth-order nonlinearity, it is actually to increase the complexity of the equation to better simulate and reflect the nonlinear behavior of water waves in the real world; abnormal waves often have characteristics different from conventional waves, such as higher wave heights, more complex waveforms, and possible horizontal asymmetry; by modifying the equations, more accurately simulating these characteristics, especially the horizontal asymmetry, is crucial for predicting and solving the behavior of abnormal waves; by increasing the spatial distance of effective early warning, a longer preparation time is provided for responding to the threat of abnormal waves, which is used for marine operations and navigators to take necessary measures in advance to reduce potential risks and losses.

[0069] Example 2

[0070] like Figure 1 As shown, this embodiment provides a method for rapid prediction of deep-sea abnormal waves considering the influence of fourth-order nonlinearity, comprising the following steps:

[0071] S1. The modal control equation obtained by using the general module is as follows:

[0072] (1)

[0073] Among them, formula (1) is the third-order governing equation in the spatial domain: On the basis of the above, add three items IV, V and VI. is the carrier frequency, is the carrier wave number, x is the spatial coordinate; B * is the wave envelope function B The conjugate function of ;

[0074] Introducing potential function ϕTo characterize the uniform flow in the wave field caused by the fourth-order nonlinearity, the amplitude is numerically solved by the control equations and boundary conditions composed of formula (2), formula (3) and formula (4). This uniform flow is actually closely related to the long waves generated by the non-resonant interaction of three waves:

[0075] (2)

[0076] (3)

[0077] (4)

[0078] Among them, the variable z For vertical coordinates, the fourth-order nonlinear term is incorporated into the effect of nonlinear dispersion on the evolution of anomalous waves to characterize the nonlinear hydrodynamic mechanism of irregular waves with a wider spectrum;

[0079] S2, the general module uses the correlation expression between the liquid level and the wave packet to synthesize the free wave surface and the bound wave surface at the specified position. After superposition, the two are reconstructed to obtain the time history curve of the actual wave surface. η With wave packet B The associated expression is:

[0080] (5)

[0081] (6)

[0082] (7)

[0083] Among them, the first The second term is the wavefront generated by the free wave interaction. The wavefront generated by the bound wave action has a phase that changes synchronously with the phase of the free wave;

[0084] also, η 3 is the third-order expression of the free liquid surface; η 4 is the fourth-order expression of the free liquid surface, that is, the newly added component in the wave surface reconstruction process, which not only modifies the wave surface of the second-order bound wave, that is, , and at the same time, the wavefront expression of the third-order bound wave is introduced to improve the accuracy of waveform reconstruction, that is, , and considering the influence of uniform flow caused by long waves, that is ;

[0085] S3. The control equation of the extended module regarding the motion response module of the floating marine structure is:

[0086] (8)

[0087] in, jand k The value range is 1~6. and All are the six degrees of freedom motion displacements of floating marine structures; and are the first and second order derivatives of displacement with respect to time, respectively; is the mass or moment of inertia of the structure;

[0088] In addition, hydrostatic resilience Froude-Krylov force The calculation of is obtained by integrating the static pressure and dynamic pressure on the wet surface of the floating marine structure at each moment; the abnormal wave diffraction force is recorded as , the radiation force is expressed in the time domain as the additional mass corresponding to infinite frequency , radiation recovery coefficient and memory function The expression of convolution; if there are other forces acting on the structure such as mooring force and wind force, it can be expressed as ; Vertical wave force caused by waves on deck The momentum method is used for rapid calculation. The vertical wave force is related to the deck acceleration, the hydrostatic pressure above the deck, and the rate of change of water mass.

[0089] This technical solution introduces fourth-order nonlinear effects, modifies the modal control equations, and combines wave surface reconstruction and motion response analysis of floating marine structures to achieve accurate prediction and evaluation of abnormal waves, providing important theoretical guidance and technical support for marine operations and navigation safety. Specifically, by introducing the fourth-order nonlinear effect, the complex evolution process of waves, especially the generation and propagation of abnormal waves, can be simulated and predicted more accurately. In step S1, the third-order control equation is modified and the terms related to the fourth-order nonlinearity are added to more accurately describe the nonlinear characteristics of waves. The potential function is introduced to characterize the uniform flow in the wave field caused by the fourth-order nonlinearity. This uniform flow is closely related to the long waves generated by the non-resonant interaction of three waves, further improving the accuracy of wave prediction. The wavefront reconstruction process in step S2 reconstructs the time history curve of the actual wavefront by combining the information of the free wavefront and the bound wavefront, considering not only the influence of the second-order and third-order bound waves, but also the influence of the uniform flow caused by the long waves, thereby improving the accuracy of waveform reconstruction. In step S3, the motion response of the floating marine structure is analyzed in detail. By establishing the control equation of the motion response module and considering the influence of various forces (such as hydrostatic restoring force, Froude-Krylov force, abnormal wave diffraction force, radiation force, mooring force, wind force, etc.), the motion and force response of the structure under the action of abnormal waves are accurately calculated.

[0090] Figure 2 and Figure 3Compare the prediction results of the first and second generation early warning systems of the present invention for the wave packet splitting process of the same wave group evolution. Although both models can capture the third-order modulation instability, due to the introduction of the fourth-order nonlinearity in the second generation model, the high-order nonlinearity has a certain inhibitory effect on the approximate coupled resonance of the free wave, resulting in the Gaussian wave packet being split into only two wave groups (see Figure 3 ), and the overall propagation speed of the wave packet is reduced, showing asymmetry in the horizontal space. The predicted results are more consistent with the actual evolution process of the Gaussian wave packet.

[0091] This technical solution is based on nonlinear wave theory, especially the influence of high-order nonlinear terms on wave behavior; the introduction of fourth-order nonlinearity enables the model to more accurately describe the wave packet splitting process and the asymmetry of the wave group in horizontal space.

[0092] For irregular waves that are more in line with the real ocean environment, Figure 4 The comparison shows the functional relationship between the wave surface kurtosis coefficient predicted by the first and second generation warning systems and the warning radius length in high sea conditions with strong nonlinearity. It is found that the results predicted by the improved warning system are closer to the actual observation values, and the effective radius length predicted by it is greatly increased. Therefore, the warning time is greatly improved in actual engineering, providing sufficient preparation time for responding to abnormal wave threats. In addition, due to the improvement of prediction accuracy, there is no strict requirement for the placement of the incident wave measurement buoy in the fourth-order model, and there is greater flexibility in actual engineering applications, but it is still recommended that the selection of the warning radius should not be too large or too small.

[0093] This technical solution is based on the statistical characteristics of waves and the actual needs of the early warning system; by analyzing and establishing this functional relationship, the prediction method can more accurately determine the early warning radius, thereby providing a longer early warning time. This optimization of the early warning radius helps to improve the efficiency and safety of responding to abnormal wave threats.

[0094] According to an embodiment of the present invention, in step S3, the structural response subsystem of the expansion module replaces the simple method of only relying on analyzing the relationship between the abnormal trough-trough cycle and the structural resonance period for early warning, thereby improving the risk assessment method.

[0095] This technical solution is based on the principles of structural dynamics and marine engineering, especially the movement and force response of floating marine structures under abnormal wave action; by more accurately predicting the response of the structure, the risk level can be more accurately assessed, and reasonable response measures and avoidance suggestions can be given.

[0096] According to one embodiment of the present invention, in step S3, the expansion module calculates the relevant hydrodynamic coefficients of the floating marine structure to be protected in advance and stores them in the early warning database system, which is directly called when the movement and force response are actually evaluated, thereby greatly reducing the amount of calculation and improving the early warning efficiency.

[0097] This technical solution is based on the application of database technology and efficient algorithms. By pre-calculating and storing the hydrodynamic coefficients, they can be quickly called when needed, thereby accelerating the response speed of the early warning system and improving the real-time and accuracy of the early warning.

[0098] The embodiment of the present invention takes a liquefied natural gas ship with no speed as the research object, adopts the newly added extension module of the second-generation early warning system to predict the motion response law of the ship when encountering abnormal waves, and compares it with the actual observation value. Figure 5 and Figure 6 The time history curves of the two degrees of freedom motion of heave and pitch are shown respectively, where the vertical dotted line position corresponds to the highest moment of the abnormal wave crest. Obviously, the new module effectively predicts the extreme value of the motion response of the hull when encountering abnormal waves, thus more accurately quantifying its risk level, giving reasonable response measures and avoidance suggestions, and providing theoretical guidance and technical support for marine operations and navigation safety.

[0099] Although the present invention is described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for rapid prediction of deep-sea abnormal waves considering the influence of fourth-order nonlinearity, based on a rapid prediction system for deep-sea abnormal waves considering the influence of fourth-order nonlinearity, the rapid prediction system for deep-sea abnormal waves considering the influence of fourth-order nonlinearity includes the following modules: a general module for predicting and analyzing abnormal waves, installed on any floating marine structure, introducing the influence of fourth-order nonlinearity, including an incident wave measurement subsystem and an abnormal wave prediction subsystem, wherein: The incident wave measurement subsystem obtains the wave surface time history curve of the ocean waves in real time and performs basic signal processing; the abnormal wave prediction subsystem introduces the influence of fourth-order nonlinearity and predicts the wave field information of the surrounding and central areas in real time; the extension module is used to quickly and accurately predict the extreme response of floating structures when encountering abnormal waves. Before activation, the initial setting of the hydrodynamic parameters of floating structures needs to be performed based on the physical properties of the objects to be protected, including the structural response subsystem, in which: the structural response subsystem calculates the extreme motion and force response when encountering abnormal waves in real time, gives the warning level of danger, and proposes corresponding countermeasures; The abnormal wave prediction subsystem modifies the third-order control equation and incorporates the influence of fourth-order nonlinearity, and is characterized by comprising the following steps: Step S1, using the general module to obtain the modal control equation as follows: (1) Among them, formula (1) is the third-order governing equation in the spatial domain: On the basis of the above, add three items: IV, V, and VI; is the carrier frequency, is the carrier wave number, x is the spatial coordinate; is the wave envelope function B The conjugate function of ; Introducing potential function To characterize the uniform flow in the wave field caused by the fourth-order nonlinearity, the amplitude is numerically solved by the control equations and boundary conditions composed of formula (2), formula (3) and formula (4). This uniform flow is actually closely related to the long waves generated by the non-resonant interaction of three waves: (2) (3) (4) Among them, the variable z For vertical coordinates, the fourth-order nonlinear term is incorporated into the effect of nonlinear dispersion on the evolution of anomalous waves to characterize the nonlinear hydrodynamic mechanism of irregular waves with a wider spectrum; Step S2: The general module uses the correlation expression between the liquid level and the wave packet to synthesize the free wave surface and the bound wave surface at the specified position, and reconstructs the time history curve of the actual wave surface after superposition. η With wave packet B The associated expression is: (5) (6) (7) Among them, the first The second term is the wavefront generated by the free wave interaction. The wavefront generated by the bound wave action has a phase that changes synchronously with the phase of the free wave; also, is the third-order expression of the free surface; is the fourth-order expression of the free liquid surface, that is, the newly added component in the wave surface reconstruction process, which not only modifies the wave surface of the second-order bound wave, that is, , and at the same time, the wavefront expression of the third-order bound wave is introduced to improve the accuracy of waveform reconstruction, that is, , and considering the influence of uniform flow caused by long waves, that is, ; In the step S2, the predicted result of wave packet splitting during the wave group evolution of the general module captures the third-order modulation instability. After the fourth-order nonlinearity is introduced, the high-order nonlinearity has a certain inhibitory effect on the approximate coupled resonance of the free wave, resulting in the Gaussian wave packet being split into only two wave groups; Step S3: The control equation of the extended module regarding the motion response module of the floating marine structure is: (8) in, j and k The value range is 1~6. and All are the six degrees of freedom motion displacements of floating marine structures; and are the first and second order derivatives of displacement with respect to time, respectively; is the mass or moment of inertia of the structure; In addition, hydrostatic resilience Froude-Krylov force The calculation of is obtained by integrating the static pressure and dynamic pressure on the wet surface of the floating marine structure at each moment; the abnormal wave diffraction force is recorded as , the radiation force is expressed in the time domain as the additional mass corresponding to infinite frequency , radiation recovery coefficient and memory function The expression of convolution; other forces acting on the structure are expressed as ; Vertical wave force caused by waves on deck The momentum method is used for rapid calculation. The vertical wave force is related to the deck acceleration, the hydrostatic pressure above the deck, and the rate of change of water mass.

2. The method for rapid prediction of abnormal deep-sea waves considering the influence of fourth-order nonlinearity as claimed in claim 1, characterized in that: In step S2, when the general module is in high sea conditions with strong nonlinearity, there is a certain functional relationship between the predicted wave surface kurtosis coefficient and the warning radius length.

3. The method for rapid prediction of abnormal deep-sea waves considering the fourth-order nonlinear effect as claimed in claim 1, characterized in that: In step S3, the expansion module calculates the relevant hydrodynamic coefficients of the floating marine structure to be protected in advance and stores them in the early warning database system, which is directly called when the movement and force response are actually evaluated.

4. The method for rapid prediction of abnormal deep-sea waves considering the fourth-order nonlinear effect as claimed in claim 3 is characterized in that: In step S3, the extension module predicts the motion response law when encountering abnormal waves and compares it with the actual observation value; through the time curves of the two-degree-of-freedom motion of heave and pitch, in which the vertical dotted line position corresponds to the highest moment of the abnormal wave crest, the extension module effectively predicts the extreme value of the motion response of the hull when encountering abnormal waves, quantifies its risk level, and gives reasonable response measures and avoidance suggestions.

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