Wave maker motion signal correction method for extreme sea wave physical experiment

Abstract

The application relates to a wave generator motion signal correction method for extreme sea wave physical experiments, which comprises the following steps: generating a theoretical wave signal y(t); extending the generated theoretical wave signal y(t) to f(t) in the time domain; constructing an initial wave signal segment y1(t); constructing a terminal wave signal segment y2(t); and combining the constructed initial wave signal segment y1(t), the generated theoretical wave signal y(t) and the constructed terminal wave signal segment y2(t) in the time domain according to the expression of f(t) in step S2 to obtain an actual wave generator motion signal f(t). The method can prevent the theoretical motion signal of the wave generator from being distorted, well maintains the integrity of the theoretical wave signal, constructs the initial wave signal segment and the terminal wave signal segment according to the actual motion condition of the wave generator, sufficiently guarantees the continuity and safety of the motion mechanism of the wave generator, effectively controls the disturbance of the wave generator to the water body before the experimental wave is generated, and improves the precision of the experimental results.

Description

Technical Field

[0001] This invention relates to the field of physical simulation technology of laboratory waves, and in particular to a method for correcting the motion signal of a wave generator for extreme ocean wave physics experiments. Background Technology

[0002] Extreme waves in the ocean are one of the main causes of marine disasters, and their causes and spatiotemporal evolution are still under scientific investigation. Based on measured results from limited observation points in the ocean, inversion can be performed in physical wave tanks (troughs) to deduce the causes and evolution of extreme ocean waves. Therefore, high-precision physical simulation of extreme waves is crucial for their experimental research.

[0003] A wave generator is the primary experimental equipment for generating extreme waves in physical water tanks (vessels). The motion signal of extreme waves is typically obtained by inversion using linear or nonlinear wave theory based on actual oceanographic measurements of extreme waves. This signal is called the theoretical wave-generating signal. An example is... Figure 1 Since wave generators must start from rest to produce waves, the theoretical wave signal obtained through inversion usually has a non-zero initial value, which does not match the actual initial state of the wave generator. If the theoretical wave signal is used directly to drive the wave generator, it will generate a large acceleration in a very short time to reach the set value of the theoretical signal, which can damage the motion mechanism of the wave generator. In addition, the rapid movement of the wave generator will cause large fluctuations in the water in the pool (trench), which will introduce significant errors to the subsequent wave generation and measurement. After wave generation ends, the wave generator should be in a static equilibrium position. However, the theoretical wave signal is mostly not zero at the termination moment, which means that the wave generator is in an unbalanced position at the end of wave generation. Under the action of gravity, the wave generator will become unstable, which can cause irreversible deformation of its drive connection mechanism, as shown in the example below. Figure 2 .

[0004] To address the mismatch between the theoretical wave-generating signal and the actual motion of the wave generator at the start and end times, researchers typically use the Ramp function method to correct the theoretical wave-generating signal. For example... Figure 3 As shown, the ramp function is typically a piecewise function, monotonically increasing from zero for an initial period (0-4s), taking a value of 1 for most of the middle period (4s-26.5s), and monotonically decreasing to zero near the end period (26.5s-28.5s). Multiplying the ramp function by the theoretical motion signal of the wave generator yields the actual wave signal (from...). Figure 1 and Figure 3 The actual wave generation signal obtained is as follows Figure 4 (As shown).

[0005] from Figure 4 The example results show that after processing the theoretical wave-generating signal using the Ramp function, the resulting actual wave-generating signal starts from zero and moves slowly, gradually decreasing to zero and stopping as the wave generation is about to end. This indeed meets the requirements of the wave generator for actual wave generation motion. However, from... Figure 4 A comparison of the theoretical signal and the actual wave-generating signal obtained after correction reveals that the actual wave-generating signal obtained after Ramp function processing deviates significantly from the theoretical wave-generating signal in both the initial time period (0-4s) and the wave-generating end time period (26.5s-28.5s). Therefore, the analysis of the results obtained using the Ramp function method shows that this method distorts the theoretical motion signal of the wave generator; that is, the waves generated in the physical pool do not conform to the theoretically expected wave results. This will affect the accuracy and reliability of the extreme transient wave experiment results. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for correcting the motion signal of a wave generator for extreme ocean wave physics experiments, thereby avoiding distortion of the theoretical motion signal of the wave generator and improving the accuracy and reliability of extreme transient wave experiments.

[0007] The technical solution adopted in this invention is a method for correcting the motion signal of a wave generator used in extreme ocean wave physics experiments, which includes the following steps:

[0008] S1. Generate theoretical wave signal y(t): Calculate the theoretical motion signal y(t) of the wave generator based on the time history curve η(x,t) of the extreme wave at the experimental location set in the physical water tank, where t∈[0 T].

[0009] S2. Time-domain extension of the theoretical wave-generating signal y(t) generated in step S1: The theoretical wave-generating signal y(t) generated in step S1 is extended in the time domain to f(t). Where y1(t) represents the initial wave generation signal segment, y2(t) represents the final wave generation signal segment, t1 represents the time length of the initial signal segment, and t2 represents the time length of the final signal segment;

[0010] S3. Construct the initial wave generation signal segment y1(t): Set the initial wave generation signal segment y1(t) = s1(t) * r1(t), where, s1(t)=c(1)*t 2 +c(2)t+c(3), and s1(t) satisfies the system of equations: The vector c = {c(1), c(2), c(3)} is obtained by calculating the system of equations, and the initial wave generation signal segment y1(t) is obtained by calculating the vector c.

[0011] S4. Construct the termination wave generation signal segment y2(t): Set y2(t) = s2(t) * r2(t), where s2(t) = y(t-t1), T+t1≤t≤T+t1+t2, and s2(t) satisfies the following conditions: r2(t) is any monotonically decreasing function that satisfies the following condition:

[0012] S5. Combine the initial wave-generating signal segment y1(t), the generated theoretical wave-generating signal y(t), and the constructed termination wave-generating signal segment y2(t) in the time domain according to the expression of f(t) in step S2 to obtain the actual motion signal f(t) of the wave generator.

[0013] The beneficial effects of this invention are as follows: The above-mentioned method for correcting the motion signal of a wave generator used in extreme ocean wave physics experiments extends the theoretical wave generator signal in the time domain, ensuring that the theoretical motion signal of the wave generator is not distorted and maintaining its integrity. Then, based on the actual motion of the wave generator, an initial wave generator signal segment and a termination wave generator signal segment are constructed, allowing the wave generator to start safely during the initial motion period and terminate safely during the termination motion period, fully guaranteeing the continuity, safety, and reliability of the wave generator's motion mechanism. Furthermore, the constructed initial wave generator signal segment can effectively control the disturbance of the water body by the wave generator before the experimental waves are generated, reducing the generation error of waves in the physical water tank and improving the accuracy of the experimental results.

[0014] Preferably, in step S1, the specific process of calculating the theoretical motion signal y(t) of the wave generator based on the time history curve η(x,t) of the extreme wave at the experimental location set in the physical water tank includes the following steps:

[0015] S1.1. Set up an experimental location in the physical water tank. Based on the time history curve η(x,t) of the extreme wave at the experimental location, the expression for η(x,t) is: Where n = 1, 2, 3, ..., N, N represents the total number of wave components, a n ω represents the amplitude of the nth wave component. n k represents the frequency of the nth wave component. n Let x represent the wave number of the nth wave component. f t represents the location where extreme waves are generated in the pool. f Indicates the time when extreme waves are generated in the pool;

[0016] S1.2. Inverse the wavefront ephemeris η(x0,t) at the wave generator location in the spatiotemporal domain. The expression for η(x0,t) is:

[0017] Where x0 represents the spatial location of the wave generator;

[0018] S1.3, Based on the transfer function F between the wavefront and the wave generator control system n F n The expression is: Where h1 is the distance from the drive point of the wave generator to its bottom, d represents the water depth of the pool, and the time-history motion signal of the wave generator is calculated, that is, the theoretical motion signal y(t) of the wave generator. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the theoretical wave generation signal of the wave generator in this invention;

[0020] Figure 2 This is a schematic diagram illustrating the instability of the wave generator caused by the theoretical wave generation signal in this invention.

[0021] Figure 3 This is a time-series graph of the Ramp function in this invention;

[0022] Figure 4 This is a schematic diagram of the actual motion signal of the wave generator obtained by the Ramp function in this invention;

[0023] Figure 5 This is a schematic diagram of a wave generator motion signal correction method for extreme ocean wave physics experiments according to the present invention.

[0024] Figure 6 This is a schematic diagram of the motion signal of the wave generator obtained by the method of this invention.

[0025] Figure 7 This is a comparison chart of the extreme wave generation results based on the method of this invention and existing methods. Detailed Implementation

[0026] The invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can implement it with reference to the description. The scope of protection of the invention is not limited to these specific embodiments.

[0027] This invention relates to a method for correcting the motion signal of a wave generator used in extreme ocean wave physics experiments, such as... Figure 5 As shown, the method includes the following steps:

[0028] S1. Generating the theoretical wave-generating signal y(t): The theoretical motion signal y(t) of the wave generator is calculated based on the time history curve η(x,t) of the extreme wave at the experimental location set in the physical water tank (vessel), where t∈[0 T]. The specific process is as follows:

[0029] S1.1. Set up an experimental location in the physical water tank. Based on the time history curve η(x,t) of the extreme wave at the experimental location, the expression for η(x,t) is: Where n = 1, 2, 3, ..., N, N represents the total number of wave components, a n ω represents the amplitude of the nth wave component. n k represents the frequency of the nth wave component. n Let x represent the wave number of the nth wave component. f t represents the location where extreme waves are generated in the pool. f Indicates the time when extreme waves are generated in the pool;

[0030] S1.2. Inverse the wavefront ephemeris η(x0,t) at the wave generator location in the spatiotemporal domain. The expression for η(x0,t) is:

[0031] Where x0 represents the spatial location of the wave generator;

[0032] S1.3, Based on the transfer function F between the wavefront and the wave generator control system n F n The expression is: Where h1 is the distance from the drive point of the wave generator to its bottom, d represents the water depth of the pool, and the time-history motion signal of the wave generator is calculated, that is, the theoretical motion signal y(t) of the wave generator.

[0033] S2. Time-domain extension of the theoretical wave-generating signal y(t) generated in step S1: The theoretical wave-generating signal y(t) generated in step S1 is extended in the time domain to f(t). Where y1(t) represents the initial wave generation signal segment, y2(t) represents the final wave generation signal segment, t1 represents the time length of the initial signal segment, and t2 represents the time length of the final signal segment;

[0034] S3. Constructing the initial wave-generating signal segment y1(t): This initial wave-generating signal segment y1(t) must meet the initial motion conditions of the wave generator, i.e., starting wave generation from the static equilibrium position; in addition, the signal needs to be gradually increased to the initial value of the theoretical wave-generating signal y(t) to minimize disturbance to the water body and interference with subsequent wave measurement results. Therefore, the initial wave-generating signal segment y1(t) is set as: y1(t) = s1(t) * r1(t), where, s1(t)=c(1)*t 2 +c(2)t+c(3), and s1(t) satisfies the system of equations: The vectors c = c(1), c(2), c(3)} are obtained by calculating the system of equations. The initial wave-generating signal segment y1(t) is then calculated based on the vector c. The time length t1 of the initial signal segment affects the monotonicity of the s(t) function and the surface disturbance. For different wave conditions, it is necessary to continuously try to determine the appropriate time length, which usually does not exceed twice the characteristic period. For the function s1(t), it is not limited to the expression s1(t) = c(1) * t. 2 +c(2)t+c(3), as long as the range of all analytic or discrete functions satisfying the system of equations is applicable to this invention; for the function r1(t), it is not limited to the above expression, but satisfies the following conditions: All functions are applicable to this invention;

[0035] S4. Constructing the termination wave-generating signal segment y2(t): After the theoretical wave-generating signal y(t) is executed by the wave generator, the wave generator is continuously and slowly brought to a standstill at its initial equilibrium position by terminating the wave-generating signal segment y2(t). The defined termination wave-generating signal segment y2(t) is: y2(t) = s2(t) * r2(t). To facilitate the construction of s2(t), this invention extends y(t) to s2(t), i.e.: s2(t) = y(t-t1), T+t1≤t≤T+t1+t2, and s2(t) satisfies the following conditions: r2(t) is any monotonically decreasing function that satisfies the following condition:

[0036] S5. Combine the initial wave-generating signal segment y1(t), the generated theoretical wave-generating signal y(t), and the constructed termination wave-generating signal segment y2(t) in the time domain according to the expression of f(t) in step S2 to obtain the actual motion signal f(t) of the wave generator. The actual motion signal f(t) of the wave generator must ensure that the wave generator moves smoothly and continuously, and avoid abrupt changes in motion at the connection of different signal segments.

[0037] The above-mentioned method for correcting the motion signal of a wave generator used in extreme ocean wave physics experiments involves time-domain extension of the theoretical wave generator signal, ensuring that the theoretical motion signal of the wave generator is not distorted and maintaining its integrity. Then, based on the actual motion of the wave generator, an initial wave generator signal segment and a termination wave generator signal segment are constructed, allowing the wave generator to start safely during the initial motion period and terminate safely during the termination motion period, thus fully guaranteeing the continuity and safety of the wave generator's motion mechanism. Furthermore, the constructed initial wave generator signal segment can effectively control the disturbance of the water body by the wave generator before the experimental waves are generated, reducing the generation error of waves in the physical water tank and improving the accuracy of the experimental results.

[0038] Based on the wave generator motion signal correction method proposed in this invention for extreme ocean wave physics experiments, using a certain extreme wave (A f =0.1m,t f =36s, x f Taking (e.g., 50m, N=32) as an example, this extreme wave is generated in a water tank. The motion signal of the wave generator obtained using the method of this invention is as follows: Figure 6 As shown, the results of extreme wave generation in the pool are as follows: Figure 7 As shown.

[0039] from Figure 6 As can be seen, after correcting the theoretical wave-generating signal y(t) using the method proposed in this invention, the wave generator starts from rest and slowly moves to the initial value y(0) of the theoretical wave-generating signal according to the y1(t) signal constructed by this method. Then, it generates waves according to the specified theoretical signal. When the theoretical wave-generating signal ends, the wave generator slowly terminates at its initial equilibrium position according to the constructed signal y2(t). From the entire motion wave-generating process, it can be seen that this method retains the complete theoretical wave-generating signal and meets the actual wave-generating motion requirements of the wave generator.

[0040] from Figure 7 The results of extreme wave generation shown demonstrate that, compared to existing methods, the method proposed in this invention produces extreme waves that are closer to the set target. Therefore, the method proposed in this invention is superior to existing methods in terms of both the safety of the wave generator operation and the final generation result of the extreme waves.

Claims

1. A method for correcting the motion signal of a wave generator used in extreme ocean wave physics experiments, characterized in that: The method includes the following steps: S1. Generate theoretical wave signal y(t): Calculate the theoretical motion signal y(t) of the wave generator based on the time history curve η(x,t) of the extreme wave at the experimental location set in the physical water tank, where t∈[0 T]. S2. Time-domain extension of the theoretical wave-generating signal y(t) generated in step S1: The theoretical wave-generating signal y(t) generated in step S1 is extended in the time domain to f(t). Where y1(t) represents the initial wave generation signal segment, y2(t) represents the final wave generation signal segment, t1 represents the time length of the initial signal segment, and t2 represents the time length of the final signal segment; S3. Construct the initial wave generation signal segment y1(t): Set the initial wave generation signal segment y1(t) = s1(t) * r1(t), where r1(t) = s1(t)=c(1)*t 2 +c(2)t+c(3), and s1(t) satisfies the system of equations: The vector c = {c(1), c(2), c(3)} is obtained by calculating the system of equations, and the initial wave generation signal segment y1(t) is obtained by calculating the vector c. S4. Construct the termination wave generation signal segment y2(t): Set y2(t) = s2(t) * r2(t), where s2(t) = y(t-t1), T+t1≤t≤T+t1+t2, and s2(t) satisfies the following conditions: r2(t) is any monotonically decreasing function that satisfies the following condition: S5. Combine the initial wave-generating signal segment y1(t), the generated theoretical wave-generating signal y(t), and the constructed termination wave-generating signal segment y2(t) in the time domain according to the expression of f(t) in step S2 to obtain the actual motion signal f(t) of the wave generator.

2. The method for correcting the motion signal of a wave generator for extreme ocean wave physics experiments according to claim 1, characterized in that: In step S1, the specific process of calculating the theoretical motion signal y(t) of the wave generator based on the time history curve η(x,t) of the extreme wave at the experimental location set in the physical water tank includes the following steps: S1.

1. Set up an experimental location in the physical water tank. Based on the time history curve η(x,t) of the extreme wave at the experimental location, the expression for η(x,t) is: Where n = 1, 2, 3, ..., N, N represents the total number of wave components, a n ω represents the amplitude of the nth wave component. n k represents the frequency of the nth wave component. n Let x represent the wave number of the nth wave component. f t represents the location where extreme waves are generated in the pool. f Indicates the time when extreme waves are generated in the pool; S1.

2. Inverse the wavefront ephemeris η(x0,t) at the wave generator in the spatiotemporal domain. The expression for η(x0,t) is: Where x0 represents the spatial location of the wave generator; S1.3, Based on the transfer function F between the wavefront and the wave generator control system n F n The expression is: Where h1 represents the distance from the drive point of the wave generator to its bottom, and d represents the water depth of the physical pool. The time-history motion signal of the wave generator is calculated, that is, the theoretical motion signal y(t) of the wave generator.

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