Method for calculating offshore construction operability of engineering vessel

Abstract

Disclosed in the present invention is a method for calculating offshore construction operability of an engineering vessel, comprising: step I, collecting three-hourly multi-peak spectral wave data of offshore construction areas, including wave heights and wave periods; step II, calculating three-hourly equivalent single-peak spectral wave heights and three-hourly equivalent single-peak spectral wave periods; step III, calculating three-hourly irregular wave spectra; step IV, using hydrodynamic analysis software to calculate a motion response amplitude operator of the engineering vessel; step V, using a frequency domain calculation method to calculate a motion response energy density spectrum of the engineering vessel; step VI, using the frequency domain calculation method to calculate a motion response value of each degree of freedom of the engineering vessel; and step VII, calculating the operability of the engineering vessel. The present invention solves the problems of low calculation efficiency and poor calculation accuracy of existing methods for calculating the offshore construction operability of engineering vessels.

Description

A method for calculating the workability of engineering vessels for offshore construction Technical Field

[0001] This invention relates to a method for calculating the workability of engineering vessels for offshore construction. Background Technology

[0002] In open sea areas, where wind waves and swells coexist, the wave spectrum is described as a bimodal spectrum. The mixed waves of the bimodal spectrum have a significant impact on the construction work of engineering vessels, especially when the selected engineering vessel is a floating structure. Floating structures often have lower natural frequencies, and the peak frequencies of the swell spectrum may excite the engineering vessel to produce violent movements, making construction impossible.

[0003] The technical solution disclosed in Chinese invention patent CN113673092B is based on a time-frequency domain joint calculation method, which proposes a method for calculating the proportion of the operable window period of a piling vessel under multi-peak spectrum mixed waves. Although it greatly improves the calculation speed compared with the full time domain calculation method, if the multi-peak spectrum mixed waves can be equivalent to single-peak spectrum waves and the full frequency domain method is used for calculation, the calculation speed can be further improved. This has great value for the realization of real-time forecasting of the operability of engineering vessels in offshore construction.

[0004] Currently, the equivalent wave height and period of multi-peak spectrum waves are usually obtained using energy superposition based on Richter theory, i.e.

[0005] In the above formula: H E The equivalent wave height of the synthesized wave; T E For the equivalent wave period, the subscripts 1, 2, ..., n in H and T correspond one-to-one to represent the wave height and period of each wave before superposition.

[0006] In the above formula, the wave period equivalence method is based on the equivalence of the kinetic energy of water particles. However, the energy that excites ship motion is the energy of the waves. Taking the mixed wave data of the sea area where the Yangjiang project in Guangdong Province was located on December 25, 2021, as an example, the wave height of the wind wave in the multi-peak mixed wave was 1.3m, with an average period of 5s, and the wave height of the main swell was 1.8m, with a wave period of 9s. Using the above formula, the equivalent wave period can be obtained as 7s. Since ship motion is highly sensitive to wave period, this may cause serious distortion in the calculation of ship motion response. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for calculating the workability of engineering vessels for offshore construction, which can solve the problems of low calculation efficiency and poor accuracy of existing methods for calculating the workability of engineering vessels for offshore construction.

[0008] The objective of this invention is achieved as follows: a method for calculating the workability of engineering vessels for offshore construction, comprising the following steps:

[0009] Step 1: Collect multi-peak wave data of the construction sea area every 3 hours, including wave height and wave period;

[0010] Step 2: Calculate the equivalent single-peak spectrum height and period for each 3-hour interval using the following formula (1);

[0011] In the above formula (1), H E The equivalent wave height of the synthesized wave; T E For the equivalent wave period, the subscripts 1, 2, ..., n in H and T correspond one-to-one to represent the wave height and period before superposition;

[0012] Step 3: Calculate the irregular wave spectrum S for each 3-hour interval using the following formula (2). W (ω):

[0013] In formula (2) above, ω is the wave frequency; H E The equivalent wave height of the synthesized wave; T E The equivalent wave period;

[0014] Step 4: Use hydrodynamic analysis software to calculate the motion amplitude response operator RAO(ω) of the engineering vessel;

[0015] Step 5: Using frequency domain calculation methods, calculate the energy density spectrum S of the engineering vessel's motion response based on the RAO(ω) operator. x (ω), that is, calculated using the following formula (3): S x (ω)=RAO 2 (ω)·S W (ω) (3)

[0016] Step six: Using frequency domain calculation methods, calculate the motion response value X of each degree of freedom of the engineering vessel. iα That is, the following formula (4) is used for calculation:

[0017] In the above formula (4), α is the wave height exceedance probability; m0 is the S X (ω) is the zeroth order moment in the frequency domain, m0=∫S X (ω)dω;

[0018] Step 7: Calculate the workability of the engineering vessel. When the calculated motion response value X... iα The operational motion criterion X for engineering vessels is smaller than that for engineering vessels. crAt that time, it is considered that the engineering vessel can operate under the current sea conditions; at the same time, the workability RE of the engineering vessel is calculated according to the following formula (5):

[0019] In the above formula (5), N working The number of sea states that allow engineering vessels to operate for 3 hours; N total This represents the total number of sea conditions over 3 hours.

[0020] The above-mentioned method for calculating the workability of engineering vessels for offshore construction, wherein, in step four, the hydrodynamic analysis software is a marine engineering hydrodynamic analysis software based on the principle of circumferential radiation.

[0021] The method for calculating the workability of engineering vessels for offshore construction in this invention has the following characteristics:

[0022] (1) This invention proposes a method for calculating the equivalent wave period by weighted quadratic method. Compared with the equivalent wave period calculated by energy superposition based on Rice theory in the prior art, the calculation accuracy is higher when used for the calculation of the workability of marine construction of engineering vessels in the full frequency domain.

[0023] (2) The method for calculating the workability of engineering vessels at sea proposed in this invention can effectively reduce the calculation time while ensuring the calculation accuracy, compared with the existing time-frequency domain joint calculation method. Attached Figure Description

[0024] Figure 1 is a flowchart of the calculation method for the workability of engineering vessels for offshore construction according to the present invention;

[0025] Figure 2 shows the wave height data collected during step one of the present invention. Figures 2(a), 2(b), 2(c), 2(d), 2(e), and 2(f) correspond one-to-one with the wave height data of Moray East Wind Farm, Seagreen Wind Farm, DoggerBank Wind Farm, CGN Huizhou Port II Wind Farm, Qingzhou Phase 5, 6, and 7 Wind Farm, and CGN Yangjiang Fanshi Wind Farm.

[0026] Figure 3 is a wave period data diagram collected during step one of the present invention. Figures 3(a), 3(b), 3(c), 3(d), 3(e), and 3(f) correspond one-to-one with the wave period data diagrams of Moray East Wind Farm, Seagreen Wind Farm, DoggerBank Wind Farm, CGN Huizhou Port II Wind Farm, Qingzhou Phase V, VI, and VII Wind Farm, and CGN Yangjiang Fanshi Wind Farm.

[0027] Figure 4 shows the irregular wave spectrum obtained in step three of the present invention. Figures 4(a), 4(b), 4(c), 4(d), 4(e), and 4(f) correspond one-to-one with the irregular wave spectra of Moray East Wind Farm, Seagreen Wind Farm, DoggerBank Wind Farm, CGN Huizhou Port II Wind Farm, Qingzhou Phase 5, 6, and 7 Wind Farm, and CGN Yangjiang Fanshi Wind Farm.

[0028] Figure 5(a) shows the functional relationship between the roll amplitude response operator and the wave frequency obtained in step four of the present invention;

[0029] Figure 5(b) shows the functional relationship between the pitch amplitude response operator and the wave frequency obtained in step four of the present invention.

[0030] Figure 6 shows the data on the workability of engineering vessels calculated using three methods. Detailed Implementation

[0031] The invention will now be further described with reference to the accompanying drawings.

[0032] Please refer to Figure 1. The method for calculating the workability of engineering vessels for offshore construction according to the present invention includes the following steps:

[0033] Step 1: Collect multi-peak wave data of the construction sea area every 3 hours, including wave height and wave period;

[0034] Step 2: The equivalent wave period is calculated using the second-weighted method, i.e., the equivalent single-peak spectrum height and wave period are calculated hourly using the following formula (1):

[0035] In the above formula (1), H E The equivalent wave height of the synthesized wave; T E For the equivalent wave period, the subscripts 1, 2, ..., n in H and T correspond one-to-one to represent the wave height and period before superposition;

[0036] Step 3: Calculate the irregular wave spectrum S for each 3-hour interval using the following formula (2). W (ω):

[0037] In formula (2) above, ω is the wave frequency; H E The equivalent wave height of the synthesized wave; T E The equivalent wave period;

[0038] Step 4: Calculate the motion amplitude response operator RAO(ω) of the engineering vessel using hydrodynamic analysis software; the hydrodynamic analysis software is a marine engineering hydrodynamic analysis software based on the principle of circumradiation, such as ANSYS AQWA.

[0039] Step 5: Using frequency domain calculation methods, calculate the energy density spectrum S of the engineering vessel's motion response based on the RAO(ω) operator. x (ω), that is, calculated using the following formula (3): S x (ω)=RAO 2 (ω)·S W (ω) (3)

[0040] Step six: Using frequency domain calculation methods, calculate the motion response value X of each degree of freedom of the engineering vessel. iα That is, the following formula (4) is used for calculation:

[0041] In the above formula (4), α is the wave height exceedance probability; m0 is the S X (ω) is the zeroth order moment in the frequency domain, m0=∫S X (ω)dω;

[0042] Step 7: Calculate the workability of the engineering vessel. When the calculated motion response value X... iα Less than the operational motion criterion X for engineering vessels cr At that time, it is considered that the engineering vessel can operate under the current sea conditions; at the same time, the workability RE of the engineering vessel is calculated according to the following formula (5):

[0043] In the above formula (5), N working The number of sea conditions required for the engineering vessel to complete construction within 3 hours; N total This represents the total number of sea conditions over 3 hours.

[0044] The present invention will now be specifically described using a crane vessel commonly used in offshore wind power construction in my country. The crane vessel is 180m long, 48m wide, 17m deep, and has a draft of 11m. It is assumed that the crane vessel will be operating in 2021 at the following wind farms in Europe: Moray East Wind Farm, Seagreen Wind Farm, DoggerBank Wind Farm, CGN Huizhou Port II Wind Farm, Qingzhou Phase 5, 6, and 7 Wind Farms, and CGN Yangjiang Fanshi Offshore Wind Farm.

[0045] Please refer to Figures 2 to 6. The method for calculating the workability of engineering vessels for offshore construction according to the present invention includes the following steps:

[0046] Step 1: Collect wave data for 2021 from the following wind farms: Moray East in Europe, Seagreen, DoggerBank, CGN Huizhou Port II Wind Farm, Qingzhou Phase 5, 6 and 7 Wind Farms, and CGN Yangjiang Fanshi Offshore Wind Farm. The results are shown in Figures 2 and 3.

[0047] Step 2: The equivalent single-peak spectrum height and period for each 3-hour interval are calculated using the following formula (1):

[0048] The calculation results are shown in Table 1 below:

[0049] Table 1

[0050] Step 3: The irregular wave spectrum S for each 3-hour interval is calculated using the following formula (2). W (ω);

[0051] In the above formula (2), ω is the wave frequency, H E For the equivalent wave height of the synthesized wave, T E The equivalent wave period;

[0052] The calculation results are shown in Figure 4;

[0053] Step 4: Use hydrodynamic analysis software to calculate the motion amplitude response operator RAO(ω) of the crane vessel;

[0054] In linear wave theory, the response frequency of a floating structure is the same as the excitation frequency of the wave. When excited at a certain frequency, the amplitude of motion of the floating body is in a fixed ratio to the amplitude of the wave, which is called the amplitude response operator RAO. For large floating structures, the amplitude response operator RAO is calculated using commercial hydrodynamic analysis software AQWA or WAMIT based on the boundary element method. Therefore, a model of the crane ship is first established in the hydrodynamic analysis software AQWA, and then the amplitude response operator RAO(ω) of the crane ship is calculated. The calculation results are shown in Figure 5.

[0055] Step 5: Using frequency domain calculation methods, calculate the motion response energy density spectrum S of the crane ship based on the motion amplitude response operator. x (ω), that is, calculated using the following formula (3): S x (ω)=RAO 2 (ω)·S W (ω) (3)

[0056] Step 6: Calculate the motion response values ​​of each degree of freedom of the crane vessel using the frequency domain calculation method, i.e., using formula (4):

[0057] In the above formula (4), α is the wave height exceedance probability; m0 is the S X (ω) is the zeroth order moment in the frequency domain, m0=∫S X (ω)dω;

[0058] Step 7: Calculate the workability of the crane vessel. If the calculated motion response value is less than the workability motion criterion X of the crane vessel... cr At that time, it was assumed that the current sea conditions were suitable for operation; at the same time, the workability RE of the crane vessel was calculated according to formula (5):

[0059] In the above formula (5), N working The number of sea states required for the crane vessel to complete construction within 3 hours; N total This represents the total number of sea states over 3 hours.

[0060] The calculation results are shown in Figure 6. Figure 6 shows the construction feasibility of the crane vessel calculated using three different methods for Moray East Wind Farm, Seagreen Wind Farm, DoggerBank Wind Farm, CGN Huizhou Port II Wind Farm, Qingzhou Phase 5, 6, and 7 Wind Farm, and CGN Yangjiang Fanshi Wind Farm. The first method is based on a time-frequency domain joint calculation method. The second method first uses the Rice energy equivalent method to calculate the equivalent wave period, and then uses a full-frequency domain calculation method to obtain the construction feasibility of the crane vessel. The third method is proposed in this invention, which first uses a quadratic weighted equivalent method to calculate the equivalent wave period, and then uses a full-frequency domain calculation method to obtain the construction feasibility of the crane vessel. Based on on-site construction judgment, the first method yields the most accurate results, while the results of the third method proposed in this invention are closer to those of the first method than the results of the second method in the prior art. Therefore, the calculation accuracy of the third method proposed in this invention is higher than that of the second method in the prior art. At the same time, the calculation time of the third method proposed in this invention is less than that of the first method in the prior art, which can effectively reduce the calculation time.

[0061] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions should also fall within the scope of the invention and should be defined by the claims.

Claims

1. A method for calculating the workability of engineering vessels for offshore construction, characterized in that, The calculation method includes the following steps: Step 1: Collect multi-peak wave data of the construction sea area every 3 hours, including wave height and wave period; Step 2: Calculate the equivalent single-peak spectrum height and period for each 3-hour interval using the following formula (1); In the above formula (1), H E The equivalent wave height of the synthesized wave; T E For the equivalent wave period, the subscripts 1, 2, ..., n in H and T correspond one-to-one to represent the wave height and period before superposition; Step 3: Calculate the irregular wave spectrum S for each 3-hour interval using the following formula (2). W (ω): In formula (2) above, ω is the wave frequency; H E The equivalent wave height of the synthesized wave; T E The equivalent wave period; Step 4: Use hydrodynamic analysis software to calculate the motion amplitude response operator RAO(ω) of the engineering vessel; Step 5: Using frequency domain calculation methods, calculate the energy density spectrum S of the engineering vessel's motion response based on the RAO(ω) operator. x (ω), that is, it is calculated using the following formula (3): S x (ω)=RAO 2 (ω)·S W (oh) (3) Step six: Using frequency domain calculation methods, calculate the motion response value X of each degree of freedom of the engineering vessel. iα That is, the following formula (4) is used for calculation: In the above formula (4), α is the wave height exceedance probability; m0 is the S X (ω) is the zeroth order moment in the frequency domain, m0=∫S X (ω)dω; Step 7: Calculate the workability of the engineering vessel. When the calculated motion response value Xiα is less than the workability motion criterion X of the engineering vessel... cr At that time, it is considered that the engineering vessel can operate under the current sea conditions; at the same time, the workability RE of the engineering vessel is calculated according to the following formula (5): In the above formula (5), N working The number of sea states that allow engineering vessels to operate for 3 hours; N total This represents the total number of sea conditions over 3 hours.

2. The method for calculating the workability of engineering vessels for offshore construction according to claim 1, characterized in that, When performing step four, the hydrodynamic analysis software is a marine engineering hydrodynamic analysis software based on the principle of circumferential radiation.

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