JPH08201218A - Wave generation apparatus - Google Patents

Abstract

PURPOSE: To generate oblique regular waves showing a peak distribution of high uniformity in a direction of a ridge of the wave without utilizing reflecting waves from a side wall, by letting a signal generation device include an amplitude correction means which corrects a wave generation command signal so that amplitudes of cyclic movement of adjacent wave generation plates are made different. CONSTITUTION: A signal generation device S feeds to a control device C a wave generation command signal of a cycle and a phase difference preliminarily set in accordance with an aimed advancing direction of regular waves. In consequence, each driving device D reciprocates each wave generation plate P with the cycle and phase difference, whereby regular wave moving in the aimed direction diagonally to the front of an arrangement of the wave generation plates are generated by ridge lines formed by envelopes of waves generated by the wave generation plates P. An amplitude correction means is costituted by installing a signal correction program into a computer S. The amplitude of the wave generation command signal is corrected so that an amplitude value of the cyclic movement of the individual wave generation plate P shown a curve distribution in conformity to the Dolph-Chebyshev distribution with respect to an arranging direction of the wave generation plates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wave-making device for generating oblique regular waves in front of a wave-making plate array by a periodic motion having a phase difference caused by a plurality of wave-making plates.

[0002]

2. Description of the Related Art For example, in the case of applying a regular wave in an arbitrary direction to a model of a structure for a hydraulic test of an offshore structure by using a test water tank and a wave-forming device, a desired wave-forming device is required. The function that can send out the regular wave of the wave front in the desired direction is required. For this purpose, a wave forming device for multidirectional random waves has been conventionally used, but the multidirectional random wave in that case is generally the bezel snake principle (F.Bies).
el; Proceeding of 1stConference on Ships and Wave
s, p.288-304, 1954).

That is, a wave forming device for a multi-directional irregular wave is composed of a plurality of wave forming plates arranged in a row, a driving device for individually driving each wave forming plate, and a wave forming plate for each wave forming plate by the driving device. A controller for controlling the periodic motion and a signal generator for imparting a predetermined wave-making command signal to the controller to give a phase difference to the periodic motions of the wave-making plates adjacent to each other are provided. Generating a regular wave diagonally forward of the wave plate array by a wave peak formed by the envelope of the waves generated from each wave plate according to Huygens' principle by operating the wave plate with a phase difference. You can

[0004]

However, in the conventional wave-making device, since the amplitude of each wave-making plate in operation is kept constant, when the oblique regular wave is generated according to the snake principle, the oblique regular wave generated is generated. The wave height of the wave changes along the ridge direction of the wave even near the wave-making plate where the influence of diffraction is small, and at a position about 5 m away from the wave-making plate, the wave height exceeds ± 20% of the target wave height. It is not uncommon for variations to be included, and it has been analyzed that these variations cannot be eliminated even if the width of each corrugated sheet is made infinite (T.Takayama; Report of PHRI, Vol.21. , No.2, p.3-48,
1982).

As described above, the wave height of the oblique regular wave is not uniform in the ridge direction. Therefore, the directional distribution characteristics of multidirectional random waves obtained by superimposing a large number of oblique regular waves may change depending on the position in the tank (T.Ta.
kayama and T. Hiraishi; Report of PHRI, Vol.28, No.
4, p.3-24, 1989). As a result, the accuracy of hydraulic experiments becomes insufficient, and it is extremely difficult to study hydraulic phenomena precisely.

In order to correct this problem, there has been proposed a wave-making method using reflected waves from the reflection plates provided at both ends of the wave-making machine. For example, the method of Darlingple by the formulation using the gentle gradient equation (RADarlymple; Journal of Hy
draulic Research, Vol.27, No.1, p.23-34, 1989), it is possible to obtain a desired oblique regular wave at any cross section parallel to the wave-making plate. It is also conceivable to make a directional irregular wave. However,
The method premised on the use of reflected waves from these completely reflecting sidewalls should be used when the reflected waves from the model are re-reflected on the sidewalls, such as in a test tank, and this re-reflection is a problem. I can't.

Highly accurate analysis of hydraulic experiment data is indispensable for the rational design of coastal and offshore structures. Therefore, the problem to be solved by the present invention lies in the problems in the above-mentioned prior art. In view of this, even when using the equipment of the existing multi-directional wave generator for irregular waves, the uniformity in the ridge direction of the wave is achieved without using the reflected wave from the side wall that has been conventionally performed. It is an object of the present invention to provide a wave making device capable of generating an oblique regular wave having a high wave height distribution.

[0008]

SUMMARY OF THE INVENTION A wave-making device according to the present invention comprises a plurality of wave-making plates arranged in a row, a drive device for individually driving each wave-making plate, and a drive device for each wave-making plate. A multi-directional irregularity comprising a control device for controlling the periodic motion and a signal generator for providing the control device with a predetermined wave-making command signal so as to give a phase difference to the periodic motions of the wave-making plates adjacent to each other. A wave forming device for waves, in particular, in order to generate an oblique regular wave having a highly uniform wave height distribution obliquely forward of the wave plate array, the amplitudes of the periodic motions of adjacent wave plates are mutually It is characterized in that the signal generator includes an amplitude correcting means for correcting the wave forming command signal so as to make them different from each other.

[0009]

In the wave making device for multi-directional irregular waves, the wave peaks formed by the envelope of the waves generated from each wave making plate according to Huygens' principle by operating the adjacent wave making plates with a phase difference. It is well known that a line can generate a regular wave diagonally forward of the wave making plate array. In this case, the plurality of wave-making plates arranged in a row at a uniform pitch along one side of the water tank are individually reciprocating cyclically moved by the driving device, and the periodical motion of each wave-making plate by the driving device is controlled by the control device. To be done. The signal generator gives a predetermined wave-making command signal to the control device so as to give a phase difference to the periodic motion of the wave-making plates adjacent to each other, whereby the drive device makes each wave-making plate based on the snake principle. Is periodically moved with a predetermined phase difference, and an oblique regular wave traveling in a predetermined direction defined by the phase difference is obliquely forward of the wave plate array by a wave crest line formed by the envelope of waves generated from each wave plate. Generate.

In the present invention, the amplitude of each wave-making plate is corrected by analogy with the analogy from the synthesis theory of the directivity of the array antenna that radiates electromagnetic waves into the space, and the wave-shaping is performed by the corrected motion of the wave-making plate. The height distribution of regular waves has uniformity. To this end, the signal generator of the wave-making device according to the present invention includes amplitude correction means for correcting the wave-making command signal so as to make the amplitudes of the adjacent wave-making plates different from each other.

In this case, the amplitude of the periodic motion of each wave-making plate is such that the value of the relative amplitude with respect to the amplitude of the wave-making plate at the center of the array has a predetermined curve distribution with respect to the array direction. This curve distribution is preferably the Dolph-Chebyshev distribution. The Dolph-Chebyshev distribution is well known in the directional synthesis theory of array antennas (for example, CLDolph; "A Current Distributi
on for Broadside Arrays which Optimizes the Relati
onship between Beam Width and Side-Lobe Level "Pro
ceeding of IRE, 34, No.6, p.335-348, 1946, or
JDKraus; "Antennas" McGraw-Hill, p.162-175, 198
8), in the present invention, the electromagnetic wave radiated from the array antenna and the oblique wave wave-formed by the multidirectional wave machine are
Since they are described by Helmholtz differential equations when they are treated as stationary problems, the directivity synthesis theory is newly applied to the theory of wave generation of oblique regular waves, paying attention to the similarity of phenomena between these. is there.

In the present invention, it is premised that the reflected wave from the side wall of the water tank is not used to generate the oblique regular wave.
Therefore, it is preferable that the side wall of the water tank used has a wave-dissipating structure.

[0013]

EXAMPLE FIG. 1 schematically shows the construction of a wave-making device according to an example of the present invention. In the figure, a plurality of wave-making plates P are arranged in a row along one side of a water tank (not shown) at a uniform pitch, and each wave-making plate P is associated with a corresponding drive device D (for example, reciprocating drive of a fluid pressure piston cylinder device or the like). Each device is reciprocally moved cyclically. Each drive device D is supported by a fixed mount F, and the periodic movement of each wave-making plate P by each drive device D is comprehensively controlled by a control device C which is, for example, a fluid pressure control unit.

The wave forming command signal to the control device C is given from the signal generating device S composed of a personal computer in this embodiment. The signal generator S generates a wave formation command signal having a predetermined period and phase difference according to the target traveling direction of the regular wave so that a phase difference occurs in the periodic motion of the adjacent wave forming plates according to the snake principle. To each control device C, whereby each drive device D reciprocates each wave-making plate P based on the snake principle with the above-mentioned cycle and phase difference, and is formed by the envelope of the wave generated from each wave-making plate P. A regular wave is generated by the wave peak line in a target direction diagonally ahead of the array of wave-making plates.

The signal generator S includes an amplitude correction means for correcting the wave forming command signal so that the amplitudes of the adjacent wave forming plates P are made different from each other. Compensation program is computer S
The amplitude value of the periodic motion of each wave-making plate P (for example, the value of the relative amplitude with respect to the amplitude of the center wave-making plate of the array) is used to arrange the wave-making plates. With respect to the direction, the amplitude of the wave-forming command signal is corrected so that it has a curved distribution according to the Dolph-Chebyshev distribution as described later.

The signal processing of the amplitude correction by the signal generator S corresponds to the current distribution of the omnidirectional antenna obtained by the Dolph-Chebyshev distribution known in the directivity synthesis theory of the array antenna, as will be described in detail below. The amplitude distribution is fitted to the amplitude distribution of each wave-making plate P of the multidirectional random wave-making device by a signal correction program (signal correction means) installed in the signal generator S.

The method of determining the optimal distribution using the Chebyshev polynomial in accordance with the concept of the Dolph-Chebyshev distribution in the directivity synthesis theory of the array antenna will be described below in the case of the electromagnetic field radiated from the array antenna.

That is, it can be considered that the individual wave-making plates in the multi-direction irregular wave making device are equivalent to the individual antenna elements of the linear array antenna. First, as shown in FIG. 2A, consider a linear array in which a number n _e (even number) of isotropic point wave sources are arranged at a constant interval d, and all point wave sources are excited in the same phase. Assuming that the target radiation direction θ is θ = 0, the direction is perpendicular to the array. Let the excitation amplitude of each point source be A ₀ , A ₁ , A ₂ ,.
The distribution shall be symmetrical about the center of the array. The radiation electromagnetic field in the distance in the θ direction in this case is expressed by the following mathematical expression 1.

[0019]

[Equation 1] En _e = 2A ₀ cos (ψ / 2) + 2A ₁ cos (3ψ / 2) + ・ ・ ・ ・ + 2A _k cos {(ne-1) ψ / 2}

Here, ψ is expressed by the following equation 2 by the distance d and the wavelength λ.

[0021]

[Formula 2] ψ = (2πd / λ) sin θ = d _r sin θ

Each term on the right side of Expression 1 corresponds to a radiation electromagnetic field generated by a pair of point wave sources that are symmetrically arranged with respect to the center of the array. Where 2 (k + 1) = n _e (where k = 0, 1,
2, 3, ...), the formula 1 can be rewritten as the following formula 3 with N = n _e / 2.

[0023]

(Equation 3)

Next, as shown in FIG. 2B, consider a linear array in which an odd number no of isotropic point wave sources are similarly arranged at regular intervals d. In this case, the excitation amplitude of the point source in the center of the array is 2A ₀ and its distribution is symmetrical with respect to the center of the array. The radiation electromagnetic field in the distance in the θ direction in this case is expressed by the following mathematical expression 4.

[0025]

[Equation 4] En _o = 2A ₀ + 2A ₁ cos ψ + 2A ₂ cos 2ψ + ・ ・ ・ + 2A _k cos {(n _0-1 ) ψ / 2}

Here, 2k + 1 = n _o (where k = 0, 1,
2, 3, placing the _{···), N = (n o} -1) / 2 as the number 4 can be rewritten as the following Equation 5.

[0027]

(Equation 5)

Equations 3 and 5 are as described below.
It is a polynomial of degree n _e -1, n _o -1, respectively. That is, according to De Moabre's theorem, the following equation 6 is established.

[0029]

(Equation 6)

Here, m is an order, and when the real part of the equation 6 is taken, the following equation 7 is obtained.

[0031]

(Equation 7)

The right side of the equation 7 is expanded into a binomial series to obtain the following equation 8.

[0033]

## EQU8 ## cos m (ψ / 2) = cos ^m (ψ / 2)-{m (m-1) / 2!} Cos ^m-2 (ψ / 2) sin ² (ψ / 2) + {m (m-1) (m-2) (m-3) / 4!} cos ^m-4 (ψ / 2) sin ⁴ (ψ / 2)-・ ・ ・

In Equation 8, sin ² (ψ / 2) = 1-cos ² (ψ
Putting / 2), for example, up to the order m = 4, it becomes the following Expression 9.

[0035]

M = 0, cos m (ψ / 2) = 1 m = 1, cos m (ψ / 2) = cos (ψ / 2) m = 2, cos m (ψ / 2) = 2cos ² ( ψ / 2)-1 m = 3, cos m (ψ / 2) = 4cos ³ (ψ / 2)-3 cos (ψ / 2) m = 4, cos m (ψ / 2) = 8cos ⁴ (ψ / 2)-8cos ² (ψ / 2) + 1

Here, if x = cos (ψ / 2) is set, the equation 9 becomes the following equation 10.

[0037]

Equation 10] m = 0, cos m (ψ / 2) = 1 m = 1, cos m (ψ / 2) = xm = 2, cos m (ψ / 2) = 2x 2 - 1 m = 3, cos m (ψ / 2) = 4x 3 - 3x m = 4, cos m (ψ / 2) = 8x 4 - 8x 2 + 1

The expression 10 is called a Chebyshev polynomial, and is expressed as the following expression 11 as a general expression.

[0039]

[Equation 11] Tm (x) = cos m (ψ / 2)

The Chebyshev polynomials up to the 7th degree are as shown in the following Expression 12.

[0041]

Equation 12] _{T 0 (x) = 1 T} 1 (x) = x T 2 (x) = 2x 2 - 1 T 3 (x) = 4x 3 - 3x T 4 (x) = 8x 4 - 8x 2 + _{1 T 5 (x) = 16x} 5 - 20x 3 + 5x T 6 (x) = 32x 6 - 48x 4 + 18x 2 - 1 T 7 (x) = 64x 7 - 112x 5 + 56x 3 - 7x

The degree of these polynomials is m, and the root x of the polynomial is cos m (ψ / 2) = 0 or m (ψ / 2) = (2k −
1) Given by π / 2. Therefore, if we write the root x as x ',
x ′ is represented as the following Expression 13.

[0043]

X '= cos {(2k-1) π / 2m}

It has been shown above that cos m (ψ / 2) is a polynomial of degree m. Since equations 3 and 5 are sums of polynomials of the form cos m (ψ / 2), they can be expressed by polynomials of degree 2k + 1 and 2k, and 2k + 1 = n for even arrays. _e -1, 2k for odd arrays
= _no- . Therefore, the equations 3 and 5 representing the distribution of the radiated electromagnetic field are polynomials of the (number of point wave sources-1) order. Number 3
And Eq. 5 are equalized with Chebyshev polynomials of equal order (that is, m = n−1), and the amplitude distribution of the array antenna obtained by comparing the coefficients is the Dolph-Chebyshev distribution. Further, the distribution of the radiated electromagnetic field at this time is represented by the Chebyshev polynomial of order n-1.

Chebyshev polynomial Tm (x) (m
= 0, 1, 2, 3, 4, 5) is shown in Fig. 3. From this figure, it can be seen that the Chebyshev polynomial has the following characteristics. 1. Go through point (1,1). 2. The value of Tm (x) falls within the range of ± 1 for x in the range of -1≤x≤ + 1. All roots are in this range.

The method for obtaining the optimum distribution from the Chebyshev polynomial is as follows. That is, assuming six point wave sources, the distribution of the radiated electromagnetic field in this case is expressed by a polynomial of degree 5. An optimal distribution can be obtained by equating this polynomial with a Chebyshev polynomial of degree 5 (T _{5 in} FIG. 3). Here, the ratio between the maximum value of the main lobe and the side lobe level is represented by R = (maximum value of main lobe / side lobe level). In this case, assuming that the maximum value of the side lobe is 1, the point (x ₀ , R) on T ₅ (x) corresponds to the maximum value of the main lobe. The root of the polynomial corresponds to the null point of the radiated electromagnetic field. An important property of the Chebyshev polynomial is that, given R, the beamwidth to the first null point (x = x ' ₁ ) is minimized.

The procedure for obtaining the Dolph-Chebyshev distribution is composed of the following three steps. It should be noted that, as is clear from the above Expressions 3 and 5 showing the distribution of the radiated electromagnetic field, these are functions of ψ / 2.

The first step is to choose Chebyshev polynomials of equal order for the target array. That is, a Chebyshev polynomial T _n-1 (x) of degree n-1 is selected for an array of n point sources. The relationship between the order m and the number n of point wave sources is m = n-1.

The second step is to determine R, Tm (x ₀ ) = R
To solve for x ₀ . In this case, when determining R, for example, the side lobe level is set to 26 with respect to the main lobe.
If it is reduced to dB, R = 20 because 26 dB = 20 log ₁₀ R. The value of x ₀ is obtained by trial and error or by the following Expression 14.

[0050]

Equation 14] _{x 0 = [{R + (} R 2 - 1) 1/2} 1 / m + {R - (R 2 - 1) 1/2} 1 / m] / 2

The 5th-order Chebyshev polynomial T ₅ (x) assumed here is extracted and shown in FIG. 4. As can be seen from FIG. 4, x ₀ also becomes larger than 1 when R> 1.
However, the condition of x = cos (ψ / 2) is given first, and according to this condition, the range of x must be −1 ≦ x ≦ + 1. Therefore, a new abscissa w is introduced as shown in FIG. 4 by performing scaling as shown in the following Expression 15.

[0052]

(15) w = x / x ₀

As a result, if w = cos (ψ / 2) is set, the range of w is -1≤w≤ + 1, and the above condition is satisfied. In this way, the equations 3 and 5 are converted into the abscissa w.
Expressed as a polynomial in.

In the final third step, the selected Chebyshev polynomial T _n-1 (x) is equalized with the polynomials (Equation 3 and Equation 5) representing the radiated electromagnetic field, and w = cos (ψ / 2) is obtained. It is to substitute. This is expressed as the following Expression 16.

[0055]

[Expression 16] T _n-1 (x) = En

The excitation amplitude of each point source is obtained from the equation 16,
It is clear from the above-mentioned two characteristics of the Chebyshev polynomial that their amplitudes follow the Dolph-Chebyshev distribution which is the optimum distribution when the sidelobe level is given.

In order to correct the amplitude of the wave-making plate according to the above antenna directivity synthesis theory, the Chebyshev polynomial shown in the above equation 12 is generalized and shown as the following equation 17 (when the order m is an even number). ) And Equation 18 (when the order m is an odd number).

[0058]

[Expression 17] Tm (x) = C _m x ^m + C _m-2 x ^m-2 + ・ ・ ・ + C ₀

[0059]

(Equation 18) Tm (x) = C _m x ^m + C _m-2 x ^m-2 + ・ ・ + C ₁ x

Here, the order m is m with respect to the number N of wave-making plates.
Needless to say, it is defined as = N-1. C is degree m
Table 1 shows the values of the coefficient C up to m = 23.

[0061]

[Table 1]

In the signal generator S, the number n of wave-making plates is n.
Accordingly, the equations En (x) as shown in the equation (19) when n is even and the equation (20) when n is odd are created.

[0063]

[Equation 19] En (x) = (B _n-1 / x ₀ ^n-1 ) x ^n-1 + (B _n-3 / x ₀ ^n-3 ) x ^n-3 + ・ ・ ・ + (B ₁ / x ₀ ) x

[0064]

[Equation 20] En (x) = (B _n-1 / x ₀ ^n-1 ) x ^n-1 + (B _n-3 / x ₀ ^n-3 ) x ^n-3 + ... + B ₀

Here, the coefficient Bi (i = 0, 1, 2, ..., N-1)
Takes the form of the following equation 21.

[0066]

[Equation 21] B = P ₀ A ₀ + P ₁ A ₁ + ・ ・ ・ + P _M A _M

Here, M is (n-2) / 2 when n is an even number.
And (n-1) / 2 when n is an odd number. Also, the coefficient
Pi (i = 0, 1, 2, ..., m) is determined for each number of wave-making plates, and Tables 2 and 3 show that the number of wave-making plates is 8 and 24, respectively. The value of the coefficient Pi according to the order of W = x / x _{0 in} the equation 15 is shown.

[0068]

[Table 2]

[0069]

[Table 3]

Now, considering the case where the number of wave-making plates is an even number, it is necessary for the equations 18 and 19 to have the same relationship as shown in the following equation 22.

[0071]

(B _n-1 / x ₀ ^n-1 ) x ^n-1 + (B _n-3 / x ₀ ^n-3 ) x ^n-3 + ・ ・ ・ + (B ₁ / x ₀ ) x = C _m x _m + C _m-2 x ^m-2 + ・ ・ ・ + C ₁ x

In order for Equation 22 to always hold, x on both sides
Since the coefficients of the terms must be equal for each order of,
M simultaneous linear equations shown in the following Expression 23 are established.

[0073]

[Equation 23] B _n-1 = C _n-1 · x ₀ ^n-1 B _n-3 = C _n-3 · x ₀ ^n-3 B ₁ = C ₁ · x ₀

[0074] unknowns of this system of linear equations A _0, A ₁ is included in the left-hand side of the Bi, is ··· A _M. Since the number of the number of equations unknowns is equal M, the simultaneous equations can be solved easily, the amplitude A _0, A _1, can be determined · · · A _M.

Amplitudes A ₀ , A ₁ , ... A obtained at this stage
_{Although M} still includes the parameter x ₀ , for example, by using the amplitude distribution obtained by appropriately changing x ₀ by trial and error as described above, for example, Isaxon's prediction calculation method (M. Isaa
cson; "Prediction of Directional Waves due to a Se
gmebted Wave Generator ", Proceeding of 23rd IAHRCo
ngress, Vol. C, p.442-453, 1989), and the amplitude distribution when the optimum wave height distribution is obtained is adopted as the final amplitude distribution in the storage unit of the signal generator S. Store it.

For example, the calculation example is as follows when the number of corrugated plates is eight. That is, using the values of the coefficients P ₀ , P ₁ , P ₂ , P ₃ in the case of n = 8 and the equation 21 shown in Table 2, Bi on the left side of the equation 23 is as shown in the following equation 24. .

[0077]

Equation 24] _{B 7 = 64A 3 B 5 =} 16A 2 - 112A 3 B 3 = 4A 1 - 20A 2 + 56A 3 B 1 = A 0 - 3A 1 + 5A 2 - 7A 3

Table 1 showing the coefficient C of the Chebyshev polynomial
From the value when the degree in 7 is 7, each coefficient is
It is as follows.

[0079]

[Equation 25] C ₇ = 64 C ₅ = -112 C ₃ = 56 C ₁ = -7

Therefore, the simultaneous linear equations in this case are as shown in the following Expression 26.

[0081]

Equation 26] ^{_{64A 3 = 64x 0 7 16A 2}} - 112A 3 = -112x 0 5 4A 1 - 20A 2 + 56A 3 = 56x 0 3 A 0 - 3A 1 + 5A 2 - 7A 3 = -7x 0

The simultaneous linear equations of Eq. 26 are converted into amplitudes A ₀ , A ₁ and A
Solving for ₂ and A ₃ , the following equation 27 is obtained with the parameter x ₀ left.

[0083]

Equation 27] ^{_{A 3 = x 0 7 A 2}} = 7 (x 0 7 - x 0 5) A 1 = 7 (3x 0 7 - 5x 0 5 + 2x 0 3) A 0 = 7 (5x 0 7 - 10x ₀ ⁵ + 6x ₀ ³ -x ₀ )

Here, for example, x ₀ = 1 obtained from the above-mentioned equation 14 as R = 20 and m = 7 corresponding to the case where the side lobe level is reduced to 26 dB with respect to the main lobe.
By substituting 15 into each equation of Equation 27, the respective amplitudes are calculated as shown in Equation 28 below.

[0085]

(Equation 28) A ₃ = 2.66 A ₂ = 4.54 A ₁ = 6.76 A ₀ = 8.13

In an actual wave making device, the signal generator S obtains the number 27 in advance in accordance with the number of wave making plates, and x ₀ is adjusted appropriately to store an optimum amplitude distribution, and this amplitude distribution is stored. Accordingly, the amplitude of the wave forming command signal to each wave forming plate is corrected.
As a result, the individual wave-making plates driven by the wave-making command signal periodically move with an optimal amplitude distribution along with the phase difference corresponding to the target direction according to the Snake principle, and the obtained wave height distribution of the diagonal regular waves is uniform. Will be realized.

FIG. 5 shows the amplitude distribution of the wave-making plates in the case of 24 wave-making plates in terms of relative amplitude. Further, FIG. 6 schematically shows an example of the movement of the wave making plate in the case of the conventional wave making device, and FIG. 7 schematically shows an example of the movement of the wave making plate in the case of the wave making device according to the present invention. In FIGS. 6 and 7, the water tank used has an area of 18 m × 12 m, and 24 wave-making plates with a width of 0.5 m are arranged in an extension of 12 m along the long side of the water tank. The movement of each wave-making plate is shown every 0.1 second in the case where the water wave is 1.5 m, the cycle is 1.0 second, and the wave direction θ is 30 degrees.

Further, the side wall of the water tank has a wave-dissipating structure, the phase of the wave-making plate complies with the snake principle, and the boundary element is 4 per wave-making plate so as to satisfy the element length / wavelength <0.2.
Arranged individually and calculated.

FIG. 8 shows the calculation result of the wave height distribution obtained in the conventional case in which the amplitudes of the respective wave-making plates are the same, and FIG. 9 shows the wave height distribution of the present invention in which the amplitude distribution is changed as shown in FIG. The calculation result is shown. In these figures, the hatched region has a ratio with the target wave height of 20% or less (wave height ratio of 0.8 to
The stable wave height region when 1.2) is set as an allowable value is shown. Further, FIG. 10 is a diagram comparing the calculation results on the measurement line AA ′.

It can be seen from FIG. 8 that the wave height distribution of the oblique wave generated by the conventional wave making device is locally varied, and the wave height ratio is less than 0.8 or exceeds 1.2 in islands. I understand. On the other hand, in the case of FIG. 9 according to the present invention, a portion where the wave height ratio is less than 0.8 or exceeds 1.2 only slightly appears near the wave-making plate and near the outer edge of the wave height stable region, and the main test target range No such portion appears in the vicinity of the wave direction line (BB ′ in the figure) from the center of the wave making machine.

[0091]

As described above, according to the present invention,
The uniformity of the wave height is improved in the formation of the diagonal regular wave, which has the effect of enabling a highly accurate hydraulic test to be performed. Such an effect of improving the wave height uniformity is shown in, for example, FIG. It is also clear from the diagram comparing the results on the measurement line. Further, in the present invention, since an oblique regular wave can be generated without using the reflected wave from the side wall of the aquarium, the side wall can absorb the reflected wave from the model as a wave-dissipating structure, and the reflected wave from the side wall It is also possible to prevent deterioration of test accuracy due to returning to the water tank.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a wave forming device according to an embodiment of the present invention.

FIG. 2 is an even array (a) forming an evenly spaced symmetrical array.
(Fig.) And an odd array (Fig. B).

FIG. 3 is a diagram showing Chebyshev polynomials up to the fifth order.

FIG. 4 is a diagram showing an extracted curve of a Chebyshev polynomial of degree 5.

FIG. 5 is a diagram showing an example of an amplitude distribution of a wave-making plate in the example of the present invention.

FIG. 6 is an explanatory diagram showing the movement of a wave-making plate in a conventional wave-making device.

FIG. 7 is an explanatory view showing the movement of the wave making plate in the wave making apparatus according to the embodiment of the present invention.

FIG. 8 is a diagram showing a calculation result of a wave height distribution obtained by a conventional wave making device.

FIG. 9 is a diagram showing the calculation result of the wave height distribution obtained by the apparatus according to the embodiment of the present invention.

FIG. 10 is a diagram comparing the wave height calculation results on the measurement line AA ′ of FIGS. 8 and 9;

[Explanation of symbols]

P: corrugated plate, D: drive device, F: mount, C: control device,
S: Signal generator.

Claims (1)

[Claims] 1. A plurality of wave-making plates arranged in a row, a drive device for individually driving each wave-making plate, and a control device for controlling the periodic movement of each wave-making plate by the drive device are adjacent to each other. A wave generator for generating a diagonal regular wave in front of the wave plate array, and a signal generator for giving a predetermined wave command signal to the control device so as to give a phase difference to the periodic motion of the wave plate. In the device, the signal generating device includes an amplitude correcting unit that corrects the wave forming command signal so that the amplitudes of the periodic motions of the adjacent wave forming plates are different from each other.