Nonlinear elastic damping unit-based low-vibration floating platform mooring design method and ocean energy platform mooring

Abstract

This invention provides a low-vibration floating platform mooring design method based on nonlinear elastic damping units. Nonlinear elastic damping units are arranged in series in the mooring chain between the floating platform and the anchor point. Each nonlinear elastic damping unit consists of a multi-stage progressive stiffness spring and a velocity-sensitive hydraulic damping system. The stiffness function of the multi-stage progressive stiffness spring is k(x), satisfying the requirement of exhibiting flexible characteristics at small tensile displacements and gradually increasing stiffness at large tensile displacements to achieve a nonlinear elastic response. The velocity-sensitive hydraulic damping system incorporates a variable throttling channel, and its damping function is c. p The damping force increases with increasing velocity, achieving velocity-sensitive damping characteristics. The overall mechanical response of the nonlinear elastic damping unit is described by the function F(x). This invention can effectively suppress large-amplitude vibrations of floating platforms, reduce mooring fatigue loads on marine energy platforms, and improve the platform's steady-state performance and safety.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering equipment technology, and particularly relates to a low-vibration floating platform mooring design method based on nonlinear elastic damping units and marine energy platform mooring. Background Technology

[0002] In recent years, the application of floating platforms in marine energy development and offshore engineering has been increasing, making platform stability and the safety of mooring systems critical issues. Traditional mooring chain designs have limited effectiveness in suppressing platform vibration and coping with large wave disturbances, easily leading to excessive platform displacement or mooring chain fatigue failure. Therefore, it is necessary to develop a new mooring design method to better suppress platform vibration and ensure its safety and stability under complex sea conditions. Summary of the Invention

[0003] The purpose of this invention is to provide a low-vibration floating platform mooring design method based on nonlinear elastic damping units, so as to improve platform stability, reduce mooring chain fatigue, and the resulting marine energy platform mooring can effectively suppress vibration, remain compliant under small-amplitude wave action, and provide strong restoring force and energy dissipation function under large-amplitude impact.

[0004] This invention provides a low-vibration floating platform mooring design method based on nonlinear elastic damping units, wherein nonlinear elastic damping units are arranged in series in the mooring chain between the floating platform and the anchor point.

[0005] The nonlinear elastic damping unit consists of a multi-stage progressive stiffness spring and a velocity-sensitive hydraulic damping system. The stiffness function of the multi-stage progressive stiffness spring is k(x), which exhibits flexible characteristics at small tensile displacements and gradually increases stiffness at large tensile displacements, achieving a nonlinear elastic response. The velocity-sensitive hydraulic damping system has a variable throttling channel, and the damping function is c. p ( The damping force increases with increasing velocity, achieving velocity-sensitive damping characteristics. The overall mechanical response of the nonlinear elastic damping unit is described by the function F(x), with the specific expression as follows:

[0006] ;

[0007] In the formula, x represents the stretch of the mooring chain; This indicates the platform's movement speed.

[0008] Furthermore, the specific expression for the stiffness function k(x) of the multi-stage progressive stiffness spring is as follows:

[0009] ;

[0010] Where x represents the elongation of the mooring chain, x1 represents the starting displacement of the progressive stiffness, x2 represents the saturation displacement of the progressive stiffness, and x1 < x2. k0 represents the initial stiffness of the mooring chain, and k max represents the maximum stiffness of the mooring chain.

[0011] Furthermore, the damping function C of the velocity-sensitive hydraulic damping system p ( ) has the following specific expression:

[0012] ;

[0013] Where c min is the minimum damping coefficient at low speed, c max represents the maximum damping coefficient at high speed, represents the movement speed of the platform, v0 represents the speed threshold at which the damping coefficient starts to increase rapidly, and a represents the steepness of the transition near the control threshold, which determines the smoothness of the increase in the damping coefficient.

[0014] The present invention also provides a mooring for a marine energy platform, including a mooring chain, which is obtained according to the mooring design method for a low-vibration floating platform based on a non-linear elastic damping unit as described above.

[0015] With the above solution, through the mooring design method for a low-vibration floating platform based on a non-linear elastic damping unit, a progressive response in which the stiffness gradually increases as the displacement increases is achieved through a multi-stage progressive stiffness spring structure, and damping adjustment varying with the movement speed is achieved through a velocity-sensitive hydraulic damping system, so as to remain compliant under the action of small-amplitude waves and provide strong restoring force and energy dissipation under large-amplitude impacts. The design takes the non-linear mechanical function F(x) as the core to achieve the combined control of stiffness and damping, enabling the mooring of the marine energy platform to have the characteristics of adaptive variable stiffness and variable damping. The mooring of the marine energy platform obtained by this design method can effectively suppress the large-amplitude vibration of the floating platform, reduce the fatigue load of the mooring of the marine energy platform, and improve the steady-state performance and safety of the platform.

[0016] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following takes the preferred embodiments of the present invention and combines with the attached drawings to describe in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the application of a mooring chain obtained according to the mooring design method for a low-vibration floating platform based on a non-linear elastic damping unit in an embodiment of the present invention on a mooring of a marine energy platform;

[0018] Figure 2Schematic diagram of the stiffness function k(x) of a multi-stage progressive stiffness spring according to an embodiment of the present invention;

[0019] Figure 3 Schematic diagram of the damping function Cp( ) of a velocity-sensitive hydraulic damping system according to an embodiment of the present invention.

[0020] Reference numerals:

[0021] 1 - floating platform; 2 - anchoring point; 3 - mooring chain; 4 - non-linear elastic damping unit; 5 - multi-stage progressive stiffness spring; 6 - velocity-sensitive hydraulic damping system. Detailed implementation manners

[0022] The following will further describe in detail the specific implementation manners of the present invention in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0023] Refer Figures 1 to 3 As shown, this embodiment provides a mooring design method for a low-vibration floating platform based on a non-linear elastic damping unit and a mooring for a marine energy platform.

[0024] The mooring of a marine energy platform applying a non-linear elastic damping unit includes a floating platform 1, an anchoring point 2, and a mooring chain 3 connecting the floating platform 1 and the anchoring point 2. A non-linear elastic damping unit 4 is connected in series in the mooring chain 3. The non-linear elastic damping unit includes a multi-stage progressive stiffness spring 5 and a velocity-sensitive hydraulic damping system 6.

[0025] The stiffness function of the multi-stage progressive stiffness spring 5 is k(x), which satisfies the characteristics of being flexible at small tensile displacements and gradually increasing stiffness at large tensile displacements to achieve non-linear elastic response. A variable throttle channel is provided in the velocity-sensitive hydraulic damping system 6, and the damping function is c p ( ), which satisfies that the damping force increases with the increase of the moving speed to achieve velocity-sensitive damping characteristics. The overall mechanical response of the non-linear elastic damping unit 4 is described by the function F(x), and the specific expression is as follows:

[0026] .

[0027] In some embodiments, the specific expression of the stiffness function k(x) of the multi-stage progressive stiffness spring is as follows:

[0028] ;

[0029] In the formula, x represents the tensile amount of the mooring chain, x1 represents the starting displacement of the progressive stiffness, x2 represents the saturation displacement of the progressive stiffness, and x1 < x2. k0 represents the initial stiffness of the mooring chain, k maxThis represents the maximum stiffness of the mooring chain. The initial and final displacement ranges of the spring stiffness change can be controlled by adjusting x1 and x2, thereby adjusting the sensitivity range of the nonlinear response; the initial stiffness during the small displacement stage can be controlled by adjusting k0, thus adjusting the system's compliance; and k... max By controlling the maximum stiffness during the large displacement stage, the load-bearing capacity and vibration resistance of the system under large deformation can be adjusted.

[0030] In some embodiments, the damping function C of a speed-sensitive hydraulic damping system p ( The specific expression is as follows:

[0031] .

[0032] In the formula, c min c is the minimum damping coefficient at low speed. max This represents the maximum damping coefficient at high speeds. This represents the platform's motion speed; v0 represents the speed threshold at which the damping coefficient begins to increase rapidly; and 'a' represents the steepness of the transition near the control threshold, determining the smoothness of the damping coefficient increase. This can be achieved by adjusting c. min c max By controlling the minimum and maximum values ​​of the damping coefficient, the range of damping force is determined; by adjusting v0, the inflection point of damping change with speed is set, thereby adjusting the speed sensitivity characteristics; by adjusting a, the degree of nonlinearity of damping force growth with speed is controlled, thereby adjusting the system's energy dissipation capacity and response smoothness.

[0033] This invention proposes a low-vibration floating platform mooring design method and marine energy platform mooring based on nonlinear elastic damping units. This method achieves the following when the platform is subjected to environmental loads: during small displacement stages, flexible springs provide compliance, while during large displacement stages, the stiffness gradually increases to prevent excessive stretching. Simultaneously, the damping units provide low damping during low-speed motion and automatically increase damping force during high-speed motion. Through the synergistic effect of this nonlinear elasticity and velocity-sensitive damping, adaptive vibration reduction of the mooring chain is achieved, significantly reducing the platform's vibration response.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-vibration floating platform mooring design method based on nonlinear elastic damping units, characterized in that, Nonlinear elastic damping elements are arranged in series in the mooring chain between the floating platform and the anchor point; The nonlinear elastic damping unit consists of a multi-stage progressive stiffness spring and a velocity-sensitive hydraulic damping system. The stiffness function of the multi-stage progressive stiffness spring is k(x), which exhibits flexible characteristics at small tensile displacements and gradually increases stiffness at large tensile displacements, achieving a nonlinear elastic response. The velocity-sensitive hydraulic damping system has a variable throttling channel, and the damping function is c. p ( The damping force increases with increasing velocity, achieving velocity-sensitive damping characteristics. The overall mechanical response of the nonlinear elastic damping unit is described by the function F(x), with the specific expression as follows: ； In the formula, x represents the amount of stretching of the mooring chain; This indicates the platform's movement speed.

2. The low-vibration floating platform mooring design method based on nonlinear elastic damping units according to claim 1, characterized in that, The specific expression for the stiffness function k(x) of the multi-stage progressive stiffness spring is as follows: ； Where x represents the elongation of the mooring chain, x1 represents the starting displacement of the progressive stiffness, x2 represents the saturation displacement of the progressive stiffness, and x1 < x2. k0 represents the initial stiffness of the mooring chain, and k max represents the maximum stiffness of the mooring chain.

3. The low-vibration floating platform mooring design method based on nonlinear elastic damping units according to claim 1, characterized in that, The damping function C of the velocity-sensitive hydraulic damping system p ( The specific expression for ) is as follows: ； In the formula, c min c is the minimum damping coefficient at low speed. max This represents the maximum damping coefficient at high speeds. v0 represents the speed at which the damping coefficient begins to increase rapidly, and a represents the steepness of the transition near the control threshold, which determines the smoothness of the increase in the damping coefficient.

4. A mooring system for an ocean energy platform, characterized in that, The mooring chain is obtained by the low-vibration floating platform mooring design method based on nonlinear elastic damping unit according to any one of claims 1-3.

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