JPH037885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wave observation method, and more particularly to a wave observation method for measuring the traveling direction, speed, wavelength, etc. of waves from underwater.

[Conventional technology]

Traditionally, this type of wave observation method has been based on the PPI display radar system installed on the water surface or on the coast;
Alternatively, there was a wave height meter system, which was installed in large numbers on the bottom of the water and measured the wave height directly above.

[Problem that the invention seeks to solve]

In the former radar method, the antenna must be placed in a space above the water surface, and it is difficult to install it on a sea route or in deep water, so the type that is currently in practical use is one in which the radar is installed on land along the coast at ports, etc. Therefore, the applicable water area was restricted. One possibility is to mount a radar on a ship or aircraft to measure it, but it is difficult to stay at a fixed point and make continuous observations.

As for the latter wave height meter method, in principle, the pressure gauge type and the ultrasonic type, which measures the distance from the seabed to the sea surface, were often used, but in principle, this method measures the height of the water surface directly above. Therefore, even if it was possible to measure changes in wave height, it was difficult to measure the wave direction or the situation in a wide sea area. In order to solve this problem, a method was proposed in which a large number of wave heights installed on the seabed were distributed and measured based on the rate of change of each wave height over time, but this required a large device and the need for individual wave height meters. There were drawbacks such as the need to accurately measure the installation location.

[Means for solving problems]

The present invention solves the above-mentioned drawbacks by using a detection device installed underwater that has two orthogonal fixed detection beams, making it possible to easily observe the traveling direction, speed, and wavelength of waves over a wide range. It provides equipment.

[Effect]

According to this invention, a detection device that uses sound waves installed in the sea is used, and the directional axis of the detection beam, which is wide in the vertical plane and narrow in the horizontal plane, is directed from the sea surface immediately above to the distant sea surface in the observation target range. By receiving the return scattered waves of the transmitted pulse wave from the sea surface, the beam can be detected from almost directly above the detection device, and from each point on the linear area of the sea surface along the direction of the detection beam direction axis. Information on the strength and weakness of the received waves can be obtained.

On a flat sea surface without waves, the signal strength of the returned scattered waves that are received sequentially depends on the elapsed time after transmission,
In other words, it simply attenuates uniformly with the direct distance from the detector, but if there are waves, the return scattered waves from the point facing the detector at the crest of the wave become stronger, and the wave at the trough becomes stronger. As a result, the returned scattered waves from opposite surfaces become weaker, and the received wave intensity after transmission attenuates while showing strengths and weaknesses depending on the crests of the waves, and from the distance interval of this strength (extreme value), the detection beam You can know the apparent wavelength of the wave measured in the direction of the directional axis.

Data indicating wavelength information can be obtained by a single transmission and reception, but by repeating transmission and reception at regular intervals, the distance traveled per unit time of the extreme value portions of the received data (indicating wave peaks and troughs) can be measured. The apparent traveling speed of the wave in the direction of the detection beam's directional axis can be determined.

Therefore, by using two detection devices whose detection beam directions are perpendicular to each other in the horizontal plane, the apparent wavelength and traveling speed of waves in each direction can be determined, and the composite calculation of each component can be performed. This allows us to know the true wavelength, direction, and speed of waves.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a layout diagram of a detection device installed in the sea, and FIG. 2 is a diagram showing changes in the strength of a received signal over time.

Referring to FIG. 1, it includes acoustic wave detection devices (transducers) 1 and 2 having fan-shaped detection beams 3 and 4 that are narrow in the horizontal direction and wide in the vertical direction, and the directional axis of each beam is in the horizontal plane. They are arranged so that they are perpendicular to each other. Sonic detection device 1, 2
The transmitted pulse waves emitted from the ship propagate diagonally upward, illuminating the sea surface. The ultrasound frequency used depends on the size of the sea surface area of interest and
The wavelength is selected based on the resolution, but a wavelength range of several centimeters to several meters is a reasonable range. The characteristics of the sea surface as a reflector for such wavelengths are that it exhibits a relatively diffuse reflection surface, and a transmitted wave that is obliquely incident on the sea surface generates a return scattered wave, which is sufficiently reflected at the transmitting point. can be received.

Regarding the state of the received waves after transmission, first, reflected waves from the sea surface immediately above are received, and then returned scattered waves are received from a point along the beam direction (A in FIG. 1). The intensity of the returned scattered waves varies depending on the peaks and troughs, resulting in the results shown in FIG. 2a.

The scattered waves from the surface along the direction of the ultrasonic detectors 1 and 2 become stronger, and the scattering from the opposite surface becomes weaker.
If the wave height is high, the received wave may not be received at all because it is in the shadow of the direction of wave movement. If the waves are moving in the directions shown in Figures 1a and 6, the propagation speed of underwater sound waves is sufficiently fast compared to the normal wave speed, so the effect of the time required for transmission and reception can be ignored. .

Apparent wavelength λ ₁ in the direction of the pointing axis of detectors 1 and 2,
λ ₂ is determined as the interval Δγ ₁ , Δγ ₂ (FIG. 1a) between the peaks (or troughs) of the detected and received signal. The true wave wavelength λ (Δγ) is indicated by the interval between crests along the wave traveling direction 6, and is obtained using the following equation, as understood from FIG. 1a.

After the received wave shown in Figure 2 a is obtained, a certain period of time △T
When the next transmission is made later, the wave is already in Figure 1 6.
Since the received wave is traveling in the direction shown in FIG. 2b, the strength corresponding to the peaks and troughs of the received wave are shifted, and the received wave is received as shown in FIG. 2b.
By repeating transmission and reception at regular intervals ΔT, received waves as shown in FIG. 2 c and d are obtained.

From the reception time difference (△T = t ₂ - _{t 1} ) from the same wave point (for example, wave peak S) and the underwater speed of the sound wave from the received wave shown in Fig. 2, the waves related to the emission directions of the two detection beams that are perpendicular to each other can be determined. moving distance △R ₁
and △R ₂ can be found. Therefore, the wave velocities V ₁ and V ₂ in each detection beam direction are determined as V ₁ =△R ₁ /△T V ₂ =△R ₂ /△T (2).

Incidentally, the time Δt required for the wave to move by one wavelength can be easily determined from the rate of change of the reflection point.
As is clear from FIG. 1a, Δt does not depend on the orientation axis direction. The values obtained by dividing the wavelengths λ ₁ (measured value Δγ ₁ ) and λ ₂ (measured value Δγ ₂ ) by Δt can be defined as the apparent wave propagation speeds V ₁ and V ₂ in the directional axis direction.

V ₁ = △γ ₁ / △t V ₂ = △γ ₂ / △t On the other hand, the true wave speed V is the true wavelength λ.
It is obtained by the following formula divided by t.

In actual arithmetic processing, V ₁ and V ₂ can be determined according to the above-mentioned equation (2).

The angle θ of the direction of movement 6 of the waves is determined by the following equation with reference to the direction of the detector orientation axis shown in FIG. 2a.

[Effect] As explained above, the present invention receives reflected waves from the sea surface using a detection device (transducer) having two detection beams fixedly installed in the sea, and converts this reflected wave signal into ( By processing signals according to equations 1), (3), or (4), the traveling direction, traveling speed, and wavelength of the waves can be easily determined. According to the present invention, since the detection device is installed under the sea, it does not interfere with the passage of ships on the ocean, and has a wavelength that allows easy anchoring even in the deep sea. The detection device also has the advantage of not requiring any mechanical moving parts and having a simple structure.

[Brief explanation of the drawing]

Figures 1a and 1b are plan views and vertical cross-sectional views showing the arrangement of an apparatus according to an embodiment of the present invention, and Figures 2a to d are time courses of received signals obtained in the embodiment shown in Figure 1. FIG. 1, 2...detection device, 3, 4...detection device 1,
2. Detection beam, 5... Wave crest, 6... Wave direction.

Claims (1)

[Claims] 1. Two detection beams whose directional axes are orthogonal in the horizontal plane, wide in the vertical plane and narrow in the horizontal plane, are simultaneously set for a predetermined period of time to cover from the sea surface immediately above to the water surface far away in the observation target range. The signal is emitted at intervals, and the level extreme value (maximum or minimum) signal of the reflected signal in response to the detection beam is taken as a water surface reflection signal, and the waves in the direction of each detection beam are determined from the time difference between the extreme values and the underwater velocity of the sound wave. Distance between crest or wave bottom △γ ₁ and △
γ ₂ and observe the true wavelength λ of the wave as λ=△γ ₁・△γ ₂ /√△ ₁ ² +△ ₂ ² , and in response to the two detection beams emitted in the same direction. The moving distance △R ₁ , △R ₂ of the wave in each detection beam emission direction, which is determined from the reception time difference of reflected signals from the same wave point and the underwater speed of the sound wave, and the interval between the two detection beams in the same direction. Wave velocity components in the two detection beam directions from △T
Observing V ₁ , V ₂ and the true traveling speed V as V ₁ = △R ₁ / △T V ₂ = △R ₂ / △T V = V ₁ · V ₂ /√ ₁ ² + ₂ ² , The traveling direction (angle) θ of the waves is the ΔR ₁ ,
A wave observation method characterized by observing at least one of observation using a trigonometric function formula using ΔR ₂ or V ₁ and V ₂ .