Method for obtaining reflection coefficient of floating breakwater

Abstract

The present invention discloses a method for obtaining the reflection coefficient of a floating breakwater, and belongs to the field of marine engineering technology. The present invention constructs a numerical simulation water tank, adopts a mass source wave generation method to generate waves, the wave height is H, and the period is T; obtains the spatial distribution curve of the free liquid surface height of the synthetic reflection wave; and calculates the wave height H of the synthetic reflection wave according to the spatial distribution curve of the free liquid surface height of the synthetic reflection wave. 合 ; Through the formula H 反 =#imgabs0#get H 反 The value of, where a=H 合 / 2, the radian value corresponding to the phase angle A is equal to the phase difference Φ / 2, and the phase difference Φ is obtained by formula 1. Without the use of measuring instruments such as wave height meters and Doppler current meters, the reflection coefficient of the floating embankment can be obtained by vector superposition analysis using the spatial distribution data of the free liquid surface, avoiding the previous method of extracting data through measuring instruments and solving with the help of complex formulas.

Description

Technical Field

[0001] The invention relates to a method for obtaining a reflection coefficient of a floating breakwater, and belongs to the technical field of marine engineering. Background Art

[0002] The ocean contains many rich resources. As human beings' understanding of the ocean gradually deepens, the competition among countries in the world in the development of marine resources is becoming increasingly fierce. my country has a coastline of 3 million square kilometers and rich marine resources. Since the 19th National Congress of the Communist Party of China, the country has attached more and more importance to the development of the marine economy, and the government has worked hard to make the marine economy a new engine for my country's economic development. However, the complex and changeable characteristics of the marine environment have always restricted people's development and utilization of marine resources. Therefore, providing effective protection for offshore structures has become a topic of concern to scholars.

[0003] As an important type of breakwater structure in marine engineering, floating breakwaters can adapt to deeper water and larger tidal ranges compared to other traditional breakwaters. They are more economical and eco-friendly, and have broad application prospects in marine engineering, marine aquaculture and other marine-related fields. As a floating breakwater (floating embankment) with flexibility, protection and water exchange functions, it has received extensive attention in the field of marine engineering in recent years, and the research on its hydrodynamic performance such as reflection coefficient, transmission coefficient and dissipation coefficient has also become one of the hot issues.

[0004] Among them, the reflection coefficient of the floating embankment is currently obtained by directly obtaining the wave height of the reflected wave and the wave height of the incident wave, and then obtaining the reflection coefficient. Obtaining the reflection coefficient by this method is easily affected by the reflection at both ends of the water tank, resulting in errors; in addition, this method has high requirements for programming, which invisibly increases the difficulty of implementation for beginners engaged in hydrodynamic research, and is not conducive to stimulating the learning interest of a large number of researchers. Li Hongwei used Matlab to solve the trigonometric series using the curve fitting method based on the Goda two-point method to obtain the reflection coefficient. Although this method has high accuracy, it still requires programming and has the characteristics of large amount of calculation. Summary of the invention

[0005] The purpose of the present invention is to provide a new method for obtaining the reflection coefficient of a floating embankment. The present invention uses computational fluid dynamics numerical simulation technology to construct a numerical simulation water tank, uses a mass source wave generation method to generate waves, and then obtains the reflection coefficient of the floating embankment based on the free liquid surface space distribution data of the wave generation water tank.

[0006] Compared with physical model tests, wave generation using computational fluid dynamics (CFD) numerical simulation technology has the following advantages: low cost, no scale effect, and the ability to capture flow details.

[0007] Mass source wave making is a wave making method that relies solely on numerical simulation technology. It is a method of generating waves in a numerical water tank. When making waves, a mass source is placed in the numerical water tank. The mass source continuously absorbs and releases fluid, causing the free surface of the water tank to oscillate. Under the recovery of gravity, the water body generates waves and propagates to a distance. Compared with other wave making methods, such as boundary wave making and moving plate wave making, the mass source wave making method can realize that the incident wave and the reflected wave can flow out from the boundaries at both ends of the numerical water tank respectively, which can effectively eliminate the secondary reflection of the wave, and the mass source has no effect on the waves passing through it. Considering that the numerical wave water tank has no incomparable scale effect, the present invention adopts a two-dimensional vertical flat-bottom water tank. The present invention adopts the mass source method to obtain the reflection coefficient of the single-frequency linear regular wave and the weak nonlinear regular wave under the interaction of the forward vertical floating body and the floating embankment.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for obtaining a reflection coefficient of a floating breakwater, characterized by comprising the following steps:

[0010] A numerical simulation water tank was constructed, and waves were generated using the mass source wave generation method, with a wave height of H and a period of T;

[0011] Obtaining a free liquid surface height spatial distribution curve of a synthetic reflected wave; the synthetic reflected wave is synthesized by a reflected wave located on the left side of the mass source and a reflected wave located on the right side of the mass source;

[0012] According to the spatial distribution curve of the free liquid surface height of the synthetic reflected wave, the wave height H of the synthetic reflected wave is calculated. 合 ;

[0013] By formula H 反 = Find H 反 The value of, where a=H 合 / 2, the radian value of angle A is equal to 1 / 2 of the phase difference Φ, and the phase difference Φ is calculated by formula 1;

[0014] Calculate the reflection coefficient: Reflection coefficient = H 反 / H;

[0015] Formula 1 includes:

[0016] If σ<0.25λ, phase difference Φ=(0.5λ-2σ)*2π / λ;

[0017] If 0.25λ≤σ<0.5λ, phase difference Φ=(2σ-0.5λ)*2π / λ;

[0018] If 0.5λ≤σ<0.75λ, the phase difference Φ=(1.5λ-2σ)*2π / λ; and,

[0019] If 0.75λ≤σ<λ, phase difference Φ=(2σ-1.5λ)*2π / λ;

[0020] In formula 1, π is the circumference of a circle, which is 3.1415; σ is the remainder of L divided by λ; L is the distance between the mass source and the floating embankment; λ is the wavelength of the incident wave, which is obtained by using the wave dispersion equation based on the wave-making parameters.

[0021] Among them, the left-side wave is a wave synthesized by the wave vector of the incident wave on the left side of the wave-making source and the wave reflected after the incident wave hits the floating breakwater, the right-side wave is a wave synthesized by the wave vector of the incident wave on the right side of the wave-making source and the wave reflected after the incident wave hits the floating breakwater, and the reflected wave refers to the wave reflected after the incident wave hits the floating breakwater.

[0022] The free liquid surface height spatial distribution curve of the synthetic reflected wave refers to the free liquid surface height spatial distribution curve of the synthetic reflected wave at any time after the waveform is stabilized.

[0023] The free liquid surface height spatial distribution curve of the synthetic reflected wave is obtained by subtracting the free liquid surface height spatial distribution curve of the left wave from the free liquid surface height spatial distribution curve of the right wave symmetrically to the right along the mass source axis.

[0024] The incident wave is a water tank linear wave or a weak nonlinear regular wave.

[0025] The numerical simulation water tank is constructed by means of computational fluid dynamics numerical simulation technology and is a flat-bottomed water tank; the numerical simulation water tank adopts sponge layer wave absorption technology to absorb and attenuate waves at the end of the water tank to prevent waves from reflecting at the end. The sponge layer is arranged at the water outlet of the numerical simulation water tank.

[0026] The principle of obtaining the reflection coefficient of the floating breakwater in the present invention is described as follows:

[0027] Under the conditions of using a two-dimensional vertical flat-bottom water tank and mass source to generate waves, when the waveform is stable after the incident and reflected waves are synthesized, the incident wave and the reflected wave follow the pattern shown in Formula 2-4, where the direction of wave movement is positive to the right and negative to the left.

[0028] η symmetry = -η left = η incident wave + η reflected wave 1 Formula 2;

[0029] ηright =ηincident wave-ηreflected wave2 Formula 3;

[0030] In order to obtain the vector synthesis of the two reflected waves, the difference between Formula 2 and Formula 3 is obtained as Formula 4:

[0031] η symmetry -η right = -η left -η right = η reflected wave 1 + η reflected wave 2 = η Formula 4;

[0032] Among them, η symmetry refers to the free liquid surface height on the left side of the mass source after being symmetrical along the mass source axis to the free liquid surface height on the right side of the mass source;

[0033] ηleft refers to the height of the free liquid surface on the left side of the mass source;

[0034] ηright refers to the free liquid surface height on the right side of the mass source;

[0035] ηThe incident wave refers to the height of the free liquid surface when the wave propagates to the left and right from the mass source but no reflected wave is superimposed;

[0036] ηReflected wave 1 refers to the free liquid surface height of the reflected wave located on the left side of the mass source;

[0037] ηReflected wave2 refers to the free liquid surface height of the reflected wave located on the right side of the mass source;

[0038] η reflected wave 1 and η reflected wave 2 are waves reflected back after the incident wave hits the floating breakwater, and are artificially divided into two sections by the mass source;

[0039] ηtotal refers to the free liquid surface height of the synthetic reflected wave.

[0040] It can be concluded from formula 4 that the free liquid surface height spatial distribution curve of the left wave is symmetrically distributed along the mass source to the right side and the free liquid surface height spatial distribution curve of the right wave is subtracted to obtain the free liquid surface height spatial distribution curve of the synthetic reflected wave synthesized by reflected wave 1 and reflected wave 2. According to the free liquid surface height spatial distribution curve of the synthetic reflected wave, the wave height H of the synthetic reflected wave can be obtained. 合 , H 合 = The maximum value of the free liquid surface height of the synthetic reflection wave minus the minimum value of the free liquid surface height of the synthetic reflection wave. η reflection wave 1 and η reflection wave 2 come from the same reflection wave, and their amplitudes are equal. There is only a phase difference Φ between η reflection wave 1 and η reflection wave 2. According to the principle of vector synthesis of input reflection wave (such as Fig.10 As shown), the synthesis principle of two reflected wave vectors (as shown Fig.11 As shown in the figure), the radian value of angle A is 0.5Φ, and the radian value of H is 合 / 2 as the length of the right angle side corresponding to angle A, with H 反 is the length of the hypotenuse, and a right triangle can be constructed. Therefore, the height H of the reflected wave can be obtained. 反 Formula: H 反 =H reflection wave 1 =H reflection wave 2 = , where a=H 合 / 2, the radian value of ∠A is equal to 0.5Φ.

[0041] The beneficial effects of the present invention are:

[0042] There is no need to use measuring instruments such as wave height meters and Doppler current meters. The reflection coefficient of the floating embankment can be obtained by performing vector superposition analysis using the spatial distribution data of the free liquid surface, avoiding the previous method of extracting data through measuring instruments and solving it with the help of complex formulas. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a numerical simulation effect diagram of the spatial distribution of the free liquid surface height after the waveform in the water tank is stabilized in Example 1;

[0044] Figure 2 This is a numerical simulation effect diagram of the spatial distribution of the free liquid surface height after the waveform in the water tank is stabilized in Example 2;

[0045] Figure 3 This is a numerical simulation effect diagram of the spatial distribution of the free liquid surface height after the waveform in the water tank is stabilized in Example 3;

[0046] Figure 4 This is a numerical simulation effect diagram of the spatial distribution of the free liquid surface height after the waveform in the water tank is stabilized in Example 4;

[0047] Figure 5 This is a numerical simulation effect diagram of the spatial distribution of the free liquid surface height after the waveform in the water tank is stabilized in Example 5;

[0048] Figure 6 This is a schematic diagram of solving the phase difference when σ<0.25λ;

[0049] Figure 7 This is a schematic diagram of solving the phase difference when 0.25λ≤σ<0.5λ;

[0050] Figure 8 This is a schematic diagram of solving the phase difference when 0.5λ≤σ<0.75λ;

[0051] Fig. 9 This is a schematic diagram of solving the phase difference when 0.75λ≤σ<λ;

[0052] Fig.10 This is the principle diagram of the synthesis of the incident and reflected wave vectors;

[0053] Fig.11 This is the principle diagram of reflection synthesis wave vector synthesis;

[0054] Fig.12 It is the layout diagram of the mass source wave tank;

[0055] Fig.13 The free liquid surface height spatial distribution curve (synthetic wave of incident reflected wave) and the free liquid surface height spatial distribution curve of two-stage reflected synthetic wave obtained by numerical simulation on the left and right sides of the mass source in Example 1;

[0056] Fig.14It is the free liquid surface height spatial distribution curve (synthetic wave of incident reflected wave) and the free liquid surface height spatial distribution curve of two-segment reflected synthetic wave obtained by numerical simulation of the left and right sides of the mass source in Example 2.

[0057] Fig.15 It is the free liquid surface height spatial distribution curve (synthetic wave of incident reflected wave) and the free liquid surface height spatial distribution curve of two-segment reflected synthetic wave obtained by numerical simulation of the left and right sides of the mass source in Example 3.

[0058] Fig.16 It is the free liquid surface height spatial distribution curve (synthetic wave of incident reflected wave) and the free liquid surface height spatial distribution curve of two-segment reflected synthetic wave obtained by numerical simulation of the left and right sides of the mass source in Example 4.

[0059] Fig.17 The free liquid surface height spatial distribution curve (the synthetic wave of the incident reflected wave) and the free liquid surface height spatial distribution curve of the two-stage reflected synthetic wave obtained by numerical simulation of the left and right sides of the mass source in Example 5;

[0060] in,

[0061] Figure 10-11 Middle, H 入 is the incident wave height, H 反1 It refers to the wave height of the reflected wave located on the left side of the mass source, H 反2 is the wave height of the reflected wave to the right of the mass source, H 反 It refers to the wave height of the reflected wave, H 合 It refers to the wave height of the synthetic reflected wave;

[0062] Figure 13-17 The free liquid surface height is the relative free liquid surface height, which refers to the value obtained by subtracting the water depth of the tank from the actual free liquid surface height. DETAILED DESCRIPTION

[0063] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0064] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical contents disclosed by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical contents. Example 1

[0065] In this example, a two-dimensional vertical numerical simulation water tank (hereinafter referred to as the water tank) is used. A sponge layer with a length of twice the wavelength is set at the outlet of the water tank. The thickness of the sponge layer (the thickness refers to the length of the sponge layer along the direction of wave motion, the same below) is set to twice the wavelength; mass source wave generation is adopted; the floating breakwater is semi-submerged near the fixed water surface; Fig.12 As shown. The water depth of the water tank is 1.2m, the dimensions of the floating breakwater are: 0.4m high, 0.5m wide, 0.2m draft, and the distance L between the mass source and the floating breakwater is 9.33m. The mass source is used to create weak nonlinear regular waves with a wave height of 0.06m and a period of 1.2 seconds. The wavelength λ is obtained by using the wave dispersion equation to be 2.2407m and the wave speed is 1.86725m / s. Figure 1 From the relevant data and wave speed, we can see that after 15 seconds, the waveform in the entire water tank begins to stabilize. The free liquid surface height spatial distribution curve in the water tank at 19 seconds is extracted, as shown in Figure 1 As shown. Get the remainder σ of L divided by λ: L / λ=9.33 / 2.2407=4 remainder 0.16388λ; that is, σ=0.16388λ; 0<σ<0.25λ, select from formula 1 , we can see that the phase difference Φ=1.082 rad, 0.5Φ=0.541 rad.

[0066] Formula 1 includes: if σ<0.25λ, phase difference Φ=(0.5λ-2σ)*2π / λ; if 0.25λ≤σ<0.5λ, phase difference Φ=(2σ-0.5λ)*2π / λ; if 0.5λ≤σ<0.75λ, phase difference Φ=(1.5λ-2σ)*2π / λ; and if 0.75λ≤σ<λ, phase difference Φ=(2σ-1.5λ)*2π / λ. In formula 1, the schematic diagram of the solution principle of phase difference Φ=(0.5λ-2σ)*2π / λ is as follows Figure 6 As shown; the schematic diagram of the solution principle of phase difference Φ=(2σ-0.5λ)*2π / λ is as follows Figure 7 As shown; the schematic diagram of the solution principle of Φ=(1.5λ-2σ)*2π / λ is as follows Figure 8 As shown; the schematic diagram of the solution principle of Φ=(2σ-1.5λ)*2π / λ is as follows Fig. 9 shown.

[0067] Obtain the spatial distribution curve of the incident wave free liquid surface height on the left side of the wave source in the water tank at 21 seconds and the spatial distribution curve of the free liquid surface height on the right side of the wave source; the spatial distribution curve of the free liquid surface height on the left side is symmetrical along the x-axis (mass source), and then subtracted from the spatial distribution curve of the free liquid surface height on the right side to obtain the spatial distribution curve of the free liquid surface height of the synthetic reflected wave. Obtain the wave height H of the synthetic reflected wave from the spatial distribution curve of the free liquid surface height of the synthetic reflected wave合 , H 合 =η 合最大 -η 合最小 ; said n 合最大 is the maximum free liquid surface height of the synthetic reflected wave, and the η 合最小 is the minimum free liquid surface height of the synthetic reflected wave. 合 In the process of obtaining 合最大 and η 合最小 It is OK to use the actual value or the relative value, the result is the same; relative value = actual value - water depth of the tank; the same below. Fig.13 As shown, H 合 =0.0312-(-0.0272)=0.0584m. According to the formula H 反 = Obtain the reflected wave height H 反 The value of, where a=H 合 / 2=0.0292m, the radian value of angle A is equal to 0.5Φ=0.541rad, that is, ∠A=0.541*180° / π=31°; H 反= = =0.0567. Further through the formula H 反 / H, the reflection coefficient is 0.0567 / 0.06=0.9449. Li Hongwei's method obtains the reflection coefficient of this example as 0.9152, with an error of 3.2%.

[0068] Example 2

[0069] This example uses a two-dimensional vertical numerical simulation water tank with a water depth of 0.74 meters (hereinafter referred to as the water tank). A sponge layer is set at the outlet of the water tank. The sponge layer is set at both ends of the water tank. The thickness of the sponge layer at each end is set to twice the wavelength. A mass source is used to create a linear wave with a wave height of 0.07 meters and a period of 1.6 seconds. The floating breakwater is fixed and half-submerged at the water surface. The dimensions of the floating breakwater are: 0.48 meters high, 0.535 meters wide, and 0.34 meters draft. The distance L between the mass source and the floating breakwater is 11.92 meters. The specific situation is as follows Figure 2 As shown. Using the wave dispersion equation, the wavelength λ is 3.478 meters and the wave speed is 2.17375 meters per second. Figure 2 From the relevant data and wave speed, we can see that after 16.5 seconds, the waveform in the entire water tank begins to stabilize. The spatial distribution curve of the free liquid surface height in the water tank at 27.5 seconds is extracted, as shown in Figure 2 As shown. Get the remainder σ of L divided by λ: L / λ=11.92 / 3.478=3 remainder 0.42725λ; that is, σ=0.42725λ; 0.25λ<σ<0.5λ, choose from formula 1 , we can see that the phase difference Φ=2.2273rad, 0.5Φ=1.11365rad.

[0070] Formula 1 includes: if σ<0.25λ, phase difference Φ=(0.5λ-2σ)*2π / λ; if 0.25λ≤σ<0.5λ, phase difference Φ=(2σ-0.5λ)*2π / λ; if 0.5λ≤σ<0.7,λ, phase difference Φ=(1.5λ-2σ)*2π / λ; and if 0.75λ≤σ,λ, phase difference Φ=(2σ-1.5λ)*2π / λ. In formula 1, the schematic diagram of the solution principle of phase difference Φ=(0.5λ-2σ)*2π / λ is as follows Figure 6 As shown; the schematic diagram of the solution principle of phase difference Φ=(2σ-0.5λ)*2π / λ is as follows Figure 7 As shown; the schematic diagram of the solution principle of Φ=(1.5λ-2σ)*2π / λ is as follows Figure 8 As shown; the schematic diagram of the solution principle of Φ=(2σ-1.5λ)*2π / λ is as follows Fig. 9 shown.

[0071] Obtain the free liquid surface height spatial distribution curve on the left side of the wave source in the water tank at 27.5 seconds and the free liquid surface height spatial distribution curve on the right side of the wave source; the free liquid surface height spatial distribution curve on the left side is symmetrical along the x-axis (mass source) and then superimposed and subtracted with the free liquid surface height spatial distribution curve on the right side to obtain the free liquid surface height spatial distribution curve of the synthetic reflected wave. Obtain the wave height H of the synthetic reflected wave from the free liquid surface height spatial distribution curve of the synthetic reflected wave 合 , H 合 =η 合最大 -η 合最小 ; said n 合最大 is the maximum free liquid surface height of the synthetic reflected wave, and the η 合最小 is the minimum free liquid surface height of the synthetic reflected wave. Fig.14 As shown, H 合 =0.052-(-0.048)=0.1m. According to the formula H 反 = Obtain the reflected wave height H 反 The value of, where a=H 合 / 2=0.05, the radian value of angle A is equal to 0.5Φ=1.11365rad, and the angle value of angle A is 1.11365*180° / π=63.81°. That is, H 反 = = =0.0557m. Further through the formula H 反 / H, the reflection coefficient is 0.0557 / 0.07=0.7966. Li Hongwei's method obtains the reflection coefficient of this example as 0.824, with an error of 3.3%.

[0072] Example 3

[0073] This example uses a two-dimensional vertical numerical simulation water tank with a water depth of 0.74 meters (hereinafter referred to as the water tank). A sponge layer is set at the outlet of the water tank. The sponge layer is set at both ends of the water tank. The thickness of the sponge layer at each end is set to twice the wavelength. A mass source is used to create a linear wave with a wave height of 0.07 meters and a period of 1.6 seconds. The floating breakwater adopts a fixed bottom-standing type, extending vertically from the bottom of the water tank to 0.84 meters. The dimensions of the floating breakwater are: 0.84 meters high, 0.535 meters wide, and 0.74 meters draft. It can achieve total wave reflection. The distance L between the mass source and the floating breakwater is 11.92 meters. The specific situation is as follows Figure 3 As shown. Using the wave dispersion equation, the wavelength λ is 3.478 meters and the wave speed is 2.17375 meters per second. Figure 3 From the relevant data and wave speed, we can see that after 16.5 seconds, the waveform in the entire water tank begins to stabilize. The spatial distribution curve of the free liquid surface height in the water tank at 27.5 seconds is extracted, as shown in Figure 3 As shown. Get the remainder σ of L divided by λ: L / λ=11.92 / 3.478=3 remainder 0.478λ, that is, σ=0.478λ; 0.25λ<σ<0.5λ, choose from formula 1 , we can see that the phase difference Φ=2.2273rad, 0.5Φ=1.11365rad.

[0074] Formula 1 includes: if σ<0.25λ, phase difference Φ=(0.5λ-2σ)*2π / λ; if 0.25λ≤σ<0.5λ, phase difference Φ=(2σ-0.5λ)*2π / λ; if 0.5λ≤σ<0.75λ, phase difference Φ=(1.5λ-2σ)*2π / λ; and if 0.75λ≤σ<λ, phase difference Φ=(2σ-1.5λ)*2π / λ. In formula 1, the schematic diagram of the solution principle of phase difference Φ=(0.5λ-2σ)*2π / λ is as follows Figure 6 As shown; the schematic diagram of the solution principle of phase difference Φ=(2σ-0.5λ)*2π / λ is as follows Figure 7 As shown; the schematic diagram of the solution principle of Φ=(1.5λ-2σ)*2π / λ is as follows Figure 8 As shown; the schematic diagram of the solution principle of Φ=(2σ-1.5λ)*2π / λ is as follows Fig. 9 shown.

[0075] Obtain the spatial distribution curve of the incident wave free liquid surface height on the left side of the wave source in the water tank at 27.5 seconds and the spatial distribution curve of the free liquid surface height on the right side of the wave source; the spatial distribution curve of the free liquid surface height on the left side is aligned along the x-axis (mass source), and then the spatial distribution curve of the free liquid surface height on the right side is subtracted to obtain the spatial distribution curve of the free liquid surface height of the synthetic reflected wave. The wave height H of the synthetic reflected wave is obtained from the spatial distribution curve of the free liquid surface height of the synthetic reflected wave. 合 , H 合 =η 合最大 -η 合最小 ; said n 合最大 is the maximum free liquid surface height of the synthetic reflected wave, and the η 合最小 is the minimum free liquid surface height of the synthetic reflected wave. Fig.15 As shown, H 合 =0.068-(-0.055)=0.123m. According to the formula H 反 = Obtain the reflected wave height H 反 The value of, where a=H 合 / 2, the radian value of angle A is equal to 0.5Φ-1.11365rad, and the angle value of angle A is 1.11365*180° / π=63.81°; that is, H 反 = =0.0685m. Further through the formula H 反 / H, the reflection coefficient is 0.0685 / 0.07=0.9798. Li Hongwei's method obtains the reflection coefficient of this example as 0.997, with an error of 1.7%.

[0076] Example 4

[0077] This example uses a two-dimensional vertical numerical simulation water tank (hereinafter referred to as the water tank) with a water depth of 1.2 meters. A sponge layer with twice the wavelength is set at the outlet of the water tank, and a mass source is used to create weak nonlinear regular waves with a wave height of 0.06 meters and a period of 1.2 seconds. The floating breakwater adopts a fixed semi-submersible floating breakwater. The dimensions of the floating breakwater are: 0.4 meters high, 0.8 meters wide, and 0.2 meters in draft. The distance L between the mass source and the floating breakwater is 10.44 meters. The wavelength λ is obtained by using the wave dispersion equation to be 2.2407 meters, and the wave speed is 1.86725 meters / second. From Figure 4 From the relevant data and wave speed, we can see that after 16.8 seconds, the waveform in the entire water tank begins to stabilize. The spatial distribution curve of the free liquid surface height in the water tank at 23 seconds is extracted, as shown in Figure 4 As shown. Get the remainder σ of L divided by λ: L / λ=10.44 / 2.2407=4 remainder 0.65925λ, that is, σ=0.65925λ; 0.5λ<σ<0.75λ, choose from formula 1 , we can see that the phase difference Φ=1.13982rad, 0.5Φ=0.56991rad.

[0078] Formula 1 includes: if σ<0.25λ, phase difference Φ=(0.5λ-2σ)*2π / λ; if 0.25λ≤σ<0.5λ, phase difference Φ=(2σ-0.5λ)*2π / λ; if 0.5λ≤σ<0.7,λ, phase difference Φ=(1.5λ-2σ)*2π / λ; and if 0.75λ≤σ,λ, phase difference Φ=(2σ-1.5λ)*2π / λ. In formula 1, the schematic diagram of the solution principle of phase difference Φ=(0.5λ-2σ)*2π / λ is as follows Figure 6 As shown; the schematic diagram of the solution principle of phase difference Φ=(2σ-0.5λ)*2π / λ is as follows Figure 7 As shown; the schematic diagram of the solution principle of Φ=(1.5λ-2σ)*2π / λ is as follows Figure 8 As shown; the schematic diagram of the solution principle of Φ=(2σ-1.5λ)*2π / λ is as follows Fig. 9 shown.

[0079] Obtain the spatial distribution curve of the incident wave free liquid surface height on the left side of the wave source in the water tank at 23 seconds and the spatial distribution curve of the free liquid surface height on the right side of the wave source; the spatial distribution curve of the free liquid surface height on the left side is along the x-axis (mass source), and then subtracted from the spatial distribution curve of the free liquid surface height on the right side to obtain the spatial distribution curve of the free liquid surface height of the synthetic reflected wave. The wave height H of the synthetic reflected wave is obtained from the spatial distribution curve of the free liquid surface height of the synthetic reflected wave 合 , H 合 =η 合最大 -η 合最小 ; said n 合最大 is the maximum free liquid surface height of the synthetic reflected wave, and the η 合最小 is the minimum free liquid surface height of the synthetic reflected wave. Fig.16 As shown, H 合 =0.0285-(-0.0287)=0.0572m. According to the formula H 反 = Obtain the reflected wave height H 反 The value of, where a=H 合 / 2=0.0286, the radian value of angle A is equal to 0.5Φ=0.56991, and the angle value of angle A is 0.56991*180° / π=32.6544°; H 反 = =0.05279. Further through the formula H 反 / H, the reflection coefficient is 0.05279 / 0.06=0.87995. Li Hongwei's method obtains the reflection coefficient of this example as 0.81467, with an error of 8.0%.

[0080] Example 5

[0081] This example uses a two-dimensional vertical numerical simulation water tank (hereinafter referred to as the water tank) with a water depth of 1.2 meters. A sponge layer with twice the wavelength is set at the outlet of the water tank, and a mass source is used to create weak nonlinear regular waves with a wave height of 0.06 meters and a period of 1.2 seconds. The floating breakwater adopts a fixed semi-submersible floating breakwater. The dimensions of the floating breakwater are: 0.4 meters high, 0.8 meters wide, and 0.2 meters in draft. The distance L between the mass source and the floating breakwater is 10.89 meters. The wavelength λ is obtained by using the wave dispersion equation to be 2.2407 meters, and the wave speed is 1.86725 meters / second. From Figure 5 From the relevant data and wave speed, we can see that after 17.5 seconds, the waveform in the entire water tank begins to stabilize. The spatial distribution curve of the free liquid surface height in the water tank at 21 seconds is extracted, as shown in Figure 5 As shown. Get the remainder σ of L divided by λ: L / λ=10.89 / 2.2407=4 remainder 0.86λ, that is, σ=0.86λ; 0.75λ<σ<λ, choose from formula 1 , we can see that the phase difference Φ=1.382rad, 0.5Φ=0.691 rad.

[0082] Formula 1 includes: if σ<0.25λ, phase difference Φ=(0.5λ-2σ)*2π / λ; if 0.25λ≤σ<0.5λ, phase difference Φ=(2σ-0.5λ)*2π / λ; if 0.5λ≤σ<0.75λ, phase difference Φ=(1.5λ-2σ)*2π / λ; and if 0.75λ≤σ<λ, phase difference Φ=(2σ-1.5λ)*2π / λ. In formula 1, the schematic diagram of the solution principle of phase difference Φ=(0.5λ-2σ)*2π / λ is as follows Figure 6 As shown; the schematic diagram of the solution principle of phase difference Φ=(2σ-0.5λ)*2π / λ is as follows Figure 7 As shown; the schematic diagram of the solution principle of Φ=(1.5λ-2σ)*2π / λ is as follows Figure 8 As shown; the schematic diagram of the solution principle of Φ=(2σ-1.5λ)*2π / λ is as follows Fig. 9 shown.

[0083] Obtain the spatial distribution curve of the incident wave free liquid surface height on the left side of the wave source in the water tank at 21 seconds and the spatial distribution curve of the free liquid surface height on the right side of the wave source; the spatial distribution curve of the free liquid surface height on the left side is symmetrical along the x-axis (mass source), and then subtracted from the spatial distribution curve of the free liquid surface height on the right side to obtain the spatial distribution curve of the free liquid surface height of the synthetic reflected wave. Obtain the wave height H of the synthetic reflected wave from the spatial distribution curve of the free liquid surface height of the synthetic reflected wave 合 , H 合 =η 合最大 -η 合最小 ; said n 合最大is the maximum free liquid surface height of the synthetic reflected wave, and the η 合最小 is the minimum free liquid surface height of the synthetic reflected wave. Fig.17 As shown, H 合 =0.035-(-0.034)=0.069m. According to the formula H 反 = Obtain the reflected wave height H 反 The value of, where a=H 合 / 2=0.0345, the radian value of angle A is equal to 0.5Φ=0.691, and the angle value of angle A is 0.691*180 / π=39.5925°; that is, H 反 = =0.0541. The reflection coefficient is further calculated as 0.0541 / 0.06=0.9015. The reflection coefficient of this example calculated by Li Hongwei's method is 0.9247, with an error of 2.5%.

[0084] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present invention, various modifications or variations made by technical personnel in this field without the need for creative work are still within the scope of protection of the present invention.

Claims

1. A method for obtaining a reflection coefficient of a floating breakwater, characterized in that: The following steps are involved: A numerical simulation water tank was constructed, and waves were generated using the mass source wave generation method, with a wave height of H and a period of T; Obtaining a free liquid surface height spatial distribution curve of a synthetic reflected wave; the synthetic reflected wave is synthesized by a reflected wave located on the left side of the mass source and a reflected wave located on the right side of the mass source; According to the spatial distribution curve of the free liquid surface height of the synthetic reflected wave, the wave height H of the synthetic reflected wave is calculated. 合 ; Obtain the wave height H of the synthetic reflected wave from the spatial distribution curve of the free liquid surface height of the synthetic reflected wave 合 , H 合 =η 合最大 -η 合最小 ; said n 合最大 is the maximum free liquid surface height of the synthetic reflected wave, and the η 合最小 is the minimum free liquid surface height of the synthetic reflected wave; through the formula H 反 = Find H 反 The value of, where a=H 合 / 2, the radian value of angle A is equal to Φ / 2, and Φ is obtained by formula 1; Get the reflection coefficient: reflection coefficient = H 反 / H; Formula 1 includes: If σ<0.25λ, Φ=(0.5λ-2σ)*2π / λ; If 0.25λ≤σ<0.5λ, Φ=(2σ-0.5λ)*2π / λ; If 0.5λ≤σ<0.75, Φ=(1.5λ-2σ)*2π / λ; and, If 0.75λ≤σ<λ, Φ=(2σ-1.5λ)*2π / λ; In formula 1, σ is the remainder of L divided by λ, L is the distance between the mass source and the floating embankment, λ is the wavelength of the incident wave, and λ is obtained using the wave dispersion equation based on the wave making parameters.

2. The method according to claim 1, characterized in that The free liquid surface height spatial distribution curve of the synthetic reflected wave is formed by subtracting the free liquid surface height spatial distribution curve of the left wave symmetrically to the right along the mass source and the free liquid surface height spatial distribution curve of the right wave.

3. The method according to claim 1, characterized in that The free liquid surface height spatial distribution curve of the synthetic reflected wave refers to the free liquid surface height spatial distribution curve of the synthetic reflected wave at any time after the waveform is stabilized.

4. The method according to claim 1, characterized in that The incident wave is a water tank linear wave or a weak nonlinear regular wave.

5. The method according to claim 1, characterized in that: The numerical simulation water tank is constructed by means of computational fluid dynamics numerical simulation technology.

6. The method according to claim 1, characterized in that The water tank is a flat bottom water tank.

7. The method according to claim 1, characterized in that The sponge layer wave absorbing technology is used in the numerical simulation water tank to eliminate the wave energy at both ends of the water tank.

8. The method according to claim 7, characterized in that The sponge layer is arranged at the water outlet of the numerical simulation water tank.

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