Method for quickly forecasting air gap of ocean engineering platform

Abstract

An ocean engineering platform air gap rapid forecasting method comprises the following steps: firstly, determining a relative wave surface motion correction factor of a development platform parameter relative to a parent platform parameter difference, and then obtaining each instance point of a parent platform relative wave surface motion extreme value and a relative wave surface motion extreme value of each instance point; sea condition combinations which need to be contained in the self-stored sea conditions of the development platform are listed according to specification requirements, the air gap extreme value of each point of the development platform under each independent sea condition is obtained, and the final air gap extreme value of each point is the minimum value of the air gap extreme values under each independent sea condition. The semi-submersible platform air gap forecasting method which is suitable for a semi-submersible platform scheme design stage but is not limited to the scheme design stage and is efficient, rapid, accurate and reliable is obtained by combining mother platform data and utilizing a mathematical statistics method. The invention discloses a platform stand column height design and a sea condition screening method suitable for platform operation and survival.

Description

Technical Field

[0001] This invention belongs to the field of marine ship construction and design, and specifically relates to a method for rapid prediction of air gaps in marine engineering platforms. Background Technology

[0002] The general process for predicting air gap extreme values ​​for semi-submersible platforms currently used in the industry is as follows: summarizing the platform's own characteristic information, collecting sea state parameters applicable to the proposed design, predicting the relative motion between the platform and the sea surface, and statistically analyzing air gap extreme values. Summarizing the target semi-submersible platform's own characteristic information includes its geometric shape, platform weight, center of gravity position, and characteristic parameters reflecting the platform's weight distribution. Collecting sea state parameters applicable to the proposed design includes parameters of the target platform's operating and operating marine environment. Predicting the relative motion between the platform and the sea surface is generally done by selecting a hydrodynamic numerical simulation method to predict the changes in the relative distance between various points on the platform surface and the sea surface; this is typically done using a hydrodynamic numerical simulation method based on potential flow theory. Statistically analyzing air gap extreme values ​​involves obtaining the air gap extreme values ​​at various points on the semi-submersible platform's deck surface at the probability level specified in the design specifications or requirements using probabilistic statistical methods.

[0003] This method, as a verification method, can accurately obtain the platform air gap extreme value. However, it has significant shortcomings in the semi-submersible platform design phase, particularly in predicting the platform air gap extreme value, optimizing the selection of the support column height, and rapidly predicting the air gap extreme value under any specified sea state. Specifically: 1) Predicting the extreme values ​​of the air gap is difficult during the platform design phase. This is because the platform's geometric shape, weight, and other fundamental parameters cannot be accurately determined in one step, and there are numerous combinations of these parameters. Predicting each combination separately would be time-consuming and labor-intensive.

[0004] 2) The inability to provide timely feedback on whether the column height design is reasonable affects the final design quality. Since the column height directly affects the size of the platform air gap extreme value, as mentioned in (1), it is impossible to obtain a relatively reliable and reasonable air gap extreme value prediction result during the platform design stage, and therefore it is impossible to reasonably guide the column height design.

[0005] 3) Selecting suitable sea conditions for semi-submersible platforms to operate or survive is time-consuming. Since sea state parameters vary across different sea areas globally, numerical modeling and forecasting based on different sea state parameters would be labor-intensive and time-consuming.

[0006] During the design phase of semi-submersible platforms, the literature (Research on Still Water Air Gap Estimation Method for Deep-Water Semi-Submersible Platforms, Wang Mengying) discloses a rough air gap estimation method. This method assumes that the ratio of the semi-submersible platform's heave amplitude with wave amplitude reaches a maximum of 10%, and uses probabilistic statistical methods to obtain the maximum wave amplitude in the design sea state. The air gap is then calculated as the still air gap minus 90% of the maximum wave amplitude. However, validation with several mature products reveals that while this method is simple to predict, its accuracy is significantly lacking, resulting in poor engineering applicability. Summary of the Invention

[0007] To address the above problems, this invention provides a method for rapid prediction of air gaps in marine engineering platforms, the technical solution of which is as follows: A method for rapid prediction of air gaps in marine engineering platforms, the specific process of which is as follows: S1: First, list the basic parameter comparison table between the parent platform and the development platform. Mother platform Development Platform Total length (meters) Total width (meters) Longitudinal spacing of columns (meters) Horizontal spacing of columns (meters) Self-storing operating condition draft (meters) Height of the top of the column (meters) .

[0008] The influence factors of the horizontal and vertical spacing parameters of the columns on the relative wave surface motion of each point were obtained by simple linear regression using mathematical statistics. The relative wavefront motion correction factor Cpara, representing the parameter differences between each point on the development platform and the parent platform, is obtained: .

[0009] .

[0010] C Para =C 横向间距 ×C 纵向间距 .

[0011] S2: By predicting each instance point Pn(X) of the parent platform opi ,Y opi Z opi Extreme values ​​of relative wave surface motion under short-term sea states with unit meaningful wave height and different mean zero-periods. .

[0012] Then, the coordinates of each instance point relative to the extreme values ​​of wavefront motion are transformed, and the coordinate transformation relationship is used to map each instance point on the lower surface of the parent platform to Pn(X) on the development platform. i Y i Z i The extreme values ​​of relative wave surface motion at each instance point of the development platform under short-term sea states with unit meaningful wave height and different mean zero-periods were obtained. .

[0013] The specific conversion formula is as follows: X i =Xopi ×L f / L t .

[0014] Y i =Y opi ×B f / B t .

[0015] Z i =DH.

[0016] .

[0017] Where f is any point on the development platform, t is any point on the parent platform, and DH represents the height of the top of the development platform column.

[0018] S3: List the sea state combinations that the development platform's self-stored sea state (Hs, Tz) needs to include, and obtain the air gap extreme values ​​of each instance point of the development platform under each individual sea state combination using formulas (1) and (2). (1).

[0019] (2).

[0020] The minimum air gap extreme value under each individual sea state combination is the final air gap extreme value at each instance point.

[0021] Furthermore, in step S1 of the aforementioned method for rapid prediction of air gaps in marine engineering platforms, .

[0022] Furthermore, in step S3 of the above-mentioned method for rapid prediction of air gaps in marine engineering platforms, the sea state of the platform itself is set to Hs=10m and Tz=10.9s.

[0023] Furthermore, the aforementioned method for rapid prediction of air gaps in marine engineering platforms further obtains the influence factor Cpara of relative wave surface motion at each instance point using a simple linear regression method.

[0024] Furthermore, the aforementioned method for rapid prediction of air gaps in marine engineering platforms, when the design sea state is specified as parameters (Hs, Tz), can be used to obtain the static air gap extreme value Ag at each point under the design sea state using the following formula. static : .

[0025] Ag static =DH-T.

[0026] When the specified air gap extreme value limit is min Ag When considering the design sea state parameters (Hs, Tz), the minimum design value of the static air gap (min) can be obtained using the following formula.Agstatic : .

[0027] Wherein, DH represents the height of the top of the development platform column, and T is the draft of the development platform corresponding to the air gap prediction loading condition.

[0028] By combining data from the parent platform and employing mathematical statistics, we propose an efficient, fast, accurate, and reliable method for predicting air gaps in semi-submersible platforms, as well as a method for designing platform column height and selecting sea conditions suitable for platform operation and survival. Attached Figure Description

[0029] Figure 1 , Figure 2 It is a schematic diagram of the basic dimensions and geometric parameters of a ship.

[0030] Figure 3 This is a comparison chart of the results of the present invention with those of traditional numerical methods and methods disclosed in literature. Detailed Implementation

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

[0032] like Figure 1 , 2 As shown, taking the lateral spacing of the columns as an example, this paper first introduces how to obtain the influence factor of a certain platform parameter on the extreme values ​​of the relative wave surface motion of a point on the platform surface under any short-term sea state using the simple linear regression method in mathematical statistics. The coordinates of the points in the predicted parent platform model (X...) are... opi ,Y opi Z opi The extreme value of relative wave surface motion RZ under short-term sea state with a significant wave height Hs of 1 meter and a mean zero-period Tz of 7 seconds. opi Specifically, the horizontal spacing between the columns of the parent platform prediction model was increased from 50.7 meters to 60.7 meters, and the coordinates of the prediction points (X) were recalculated. i ,Y i Z i The extreme value of relative wave surface motion RZ under short-term sea state with a significant wave height Hs of 1 meter and a mean zero-period Tz of 7 seconds. i .in: X i =X opi .

[0033] Y i =Y opi ×(B t +10) / B t =Y opi ×(50.7+10) / 50.7.

[0034] Therefore, under short-term sea states with a significant wave height Hs of 1 meter and an average zero-period Tz of 7 seconds, the influence factor of the lateral spacing of the platform pillars on the extreme values ​​of the platform's relative wave surface motion can be expressed by the simple linear regression method in mathematical statistics, based on the assumption of linear correlation of a single variable, through the following formula: .

[0035] This invention provides a rapid air gap prediction method based on parent platform data and mathematical statistics. First, hydrodynamic analysis is used to obtain the extreme values ​​of the relative wave surface motion of various points on the parent platform under short-term sea states with unit meaningful wave height and different mean zero-periods. Furthermore, by adjusting the values ​​of various basic parameters, different forecast results from comparative models were obtained. Through mathematical statistics, the influence factor Cpara of different basic parameters on the relative wave surface motion of each point under various unit meaningful wave heights and different mean zero-period short-term sea states was obtained. The extreme values ​​of the relative wave surface motion of each point of a semi-submersible platform under various unit meaningful wave heights and different mean zero-period short-term sea states can be obtained from the extreme values ​​of the relative wave surface motion of each point of a reference parent platform under various unit meaningful wave heights and different mean zero-period short-term sea states. The extreme value of the air gap at any point on the development platform is obtained through conversion. This can be expressed by the following formula: .

[0036] Ag static =DH-T.

[0037] . Example 1

[0038] A method for rapid prediction of air gaps in marine engineering platforms is proposed. Using a 3000-meter operating water depth semi-submersible support platform with complete design data as the prototype, this method is applied to predict the air gap of a well workover and completion platform operating at a water depth of 2400 meters with self-defined sea states (Hs=10m, Tz=10.9s) during the design phase. Figure 1 , 2 As shown.

[0039] First, a comparison table of basic parameters between the parent platform and the development platform is provided in Table 1: Table 1 Mother platform Development Platform Total length (meters) 97.5 100.1 Total width (meters) 65 67.6 Longitudinal spacing of columns (meters) 37.7 40.3 Horizontal spacing of columns (meters) 36.4 39 Self-storing operating condition draft (meters) 13.2 14.5 Height of the top of the column (meters) 26 26 .

[0040] The development platform's air gap extreme value prediction method is as follows: S1: First, determine the relative wavefront motion correction factor Cpara, which represents the difference between the development platform parameters and the parent platform parameters. Then, using a simple linear regression method based on mathematical statistics, obtain the influence factors of the column's lateral and longitudinal spacing parameters on the relative wavefront motion of each point. : .

[0041] The influence factors of the horizontal and vertical spacing parameters of the platform columns on the relative wave surface motion of each point are determined as follows: .

[0042] .

[0043] The relative wavefront motion correction factor for the parameter differences of each point on the development platform relative to the parent platform is obtained as follows: .

[0044] S2: As described in the literature (Prediction of Air Gap Response of Semi-Submersible Platform in Waves, Tao Jingjing and Wang Yanying) and the literature (Prediction of Air Gap Response of Semi-Submersible Platform, Zeng Zhi), the hydrodynamic analysis method is used to predict the extreme values ​​of relative wave surface motion of each point of the parent platform under different mean zero-period and unit meaningful wave height sea states. To illustrate the feasibility of this invention, only the following points regarding coordinate transformation and air gap extreme value data determination are listed. The coordinate transformations are shown in formulas (1), (2), and (3), and the transformation results are shown in Table 2, which lists the extreme values ​​of relative wave surface motion at various points on the parent platform under different average zero-cycle periods and unit meaningful wave height sea states. As shown in Table 3: X i =X opi ×L f / L t (1).

[0045] Y i =Y opi ×B f / B t (2).

[0046] Z i =DH (3).

[0047] Table 2 Examples of extreme values ​​of the parent platform's motion relative to the wave surface .

[0048] Table 3. Extreme values ​​of relative wavefront motion at various instance points of the parent platform .

[0049] S3: According to the specifications, the sea state combinations that the development platform needs to include for its self-stored sea state (Hs=10m, Tz=10.9s) are shown in Table 4: Table 4 Sea State Combinations Stored by the Development Platform .

[0050] The extreme values ​​of the air gap at each point of the development platform under each individual sea state can be obtained according to the following formula. The final extreme value of the air gap at each point is the minimum extreme value of the air gap under each individual sea state. The results of the extreme values ​​of the air gap at each instance point are shown in Table 5.

[0051] .

[0052] .

[0053] Table 5. Air gap extreme value results for each instance point on the development platform. .

[0054] The above steps demonstrate that the present invention can obtain the air gap extreme values ​​at various points on the development platform. For example... Figure 3 As shown, after the basic design of the platform was completed, the extreme values ​​of the air gap at each point were obtained according to traditional hydrodynamic analysis methods and literature estimation methods. The results obtained by comparing the method of this invention are shown in Table 6 below: Table 6 Comparison of the results of the method of the present invention with those of traditional numerical methods and methods published in literature. .

[0055] The method of this invention has multiple applications, including determining the static air gap value Ag. static Furthermore, when the air gap extreme value finally obtained in step S3 does not meet the minimum air gap extreme value requirement specified by the development platform, the sea state parameter combination that meets the minimum air gap extreme value can be derived in reverse.

[0056] Application 1: The specific process for determining the extreme value of the static air gap is as follows: First, based on the design drawings, the differences in basic parameters between the development platform and the parent platform are compared to determine the influence factors of each parameter difference on the extreme values ​​of relative wave surface motion at various points on the platform under unit wave height and different sea states with different periods. Taking the lateral spacing parameter of the columns as an example: .

[0057] Secondly, by predicting each point (X) on the lower surface of the parent platform opi ,Y opi Z opi Extreme values ​​of relative wave surface motion under short-term sea states with unit meaningful wave height and different mean zero-periods. .

[0058] Next, the coordinate transformation relationship is used to map each point on the lower surface of the parent platform to the development platform (X). i ,Y i Z iThe extreme values ​​of relative wave surface motion at various points on the development platform under short-term sea states with unit meaningful wave height and different mean zero-periods were obtained. The specific formula is as follows: X i =X opi ×L f / L t .

[0059] Y i =Y opi ×B f / B t .

[0060] Z i =DH.

[0061] .

[0062] Then, when the design sea state is specified as parameters (Hs, Tz), the extreme values ​​of the air gap at each point under the design sea state can be obtained by the following formula: .

[0063] Ag static =DH-T.

[0064] Wherein, DH represents the height of the top of the development platform column, and T is the draft of the development platform corresponding to the air gap prediction loading condition.

[0065] When the minimum limit of the air gap extreme value under the specified design sea state parameters is min Ag When considering the design sea state parameters (Hs, Tz), the minimum design value of the static air gap (min) can be obtained using the following formula. Agstatic : .

[0066] Application 2: When the specified air gap extreme value limit is min Ag and static air gap Ag static The combination of the worst sea state parameters Hs and Tz that the development platform can adapt to can be obtained by the following formula: .

[0067] Obtaining the worst sea state parameter combination can help crew members make predictions in advance and take timely and effective measures.

Claims

1. A method for rapid prediction of air gap in marine engineering platforms, characterized in that, S1: First, list the basic parameter comparison table between the parent platform and the development platform. The influence factors of the horizontal and vertical spacing parameters of the columns on the relative wave surface motion of each point were obtained by simple linear regression using mathematical statistics. , The relative wavefront motion correction factor Cpara is obtained as the difference in parameters between each point of the development platform and the parent platform. ; ; C Para =C 横向间距 ×C 纵向间距 ; S2: By predicting each instance point Pn(X) of the parent platform opi ,Y opi Z opi Extreme values ​​of relative wave surface motion under short-term sea states with unit meaningful wave height and different mean zero-periods. ; Then, the coordinates of each instance point relative to the extreme values ​​of wavefront motion are transformed, and the coordinate transformation relationship is used to map each instance point on the lower surface of the parent platform to Pn(X) on the development platform. i Y i Z i The extreme values ​​of relative wave surface motion at each instance point of the development platform under short-term sea states with unit meaningful wave height and different mean zero-periods were obtained. ; The specific conversion formula is as follows: X i =X opi ×L f / L t ; AND i =Y opi ×B f / B t ; Z i =DH; ; Where f represents any point on the development platform, t represents any point on the parent platform, and DH represents the height of the top of the column on the development platform; S3: List the sea state combinations that the development platform's self-stored sea state (Hs, Tz) needs to include, and obtain the air gap extreme values ​​of each instance point of the development platform under each individual sea state combination using formulas (1) and (2). (1)； (2)； The minimum air gap extreme value under each individual sea state combination is the final air gap extreme value at each instance point.

2. The method for rapid prediction of air gap in marine engineering platforms according to claim 1, characterized in that, In step S1, .

3. The method for rapid prediction of air gap in marine engineering platforms according to claim 1, characterized in that, In step S3, the sea state of the development platform is set to Hs=10m and Tz=10.9s.

4. The method for rapid prediction of air gap in marine engineering platforms according to claim 1, characterized in that, The influence factor Cpara of relative wavefront motion at each instance point was obtained using a simple linear regression method.

5. The method for rapid prediction of air gap in marine engineering platforms according to claim 1, characterized in that, When the design sea state is specified as a parameter (H S T Z When ), the extreme static air gap value Ag at each point under the design sea state can be obtained by the following formula. static : ; ; When the specified air gap extreme value limit is min Ag and design sea state parameters (H S T Z When the static air gap is at its minimum design value (min), the minimum design value (min) can be obtained using the following formula. Agstatic : ; Wherein, DH represents the height of the top of the development platform column, and T is the draft of the development platform corresponding to the air gap prediction loading condition.

6. The method for rapid prediction of air gap in marine engineering platforms according to claim 1, characterized in that, The basic parameter comparison table between the parent platform and the development platform is as follows: 。

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