RU2465607C2 - Method for laser-based remote rapid determination of wind speed and direction - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: atmosphere is irradiated with a horizontally scanning pulsed laser beam at time t₁ and t₂=t₁+Δt, where Δt is much greater than the time for scanning the analysed spatial region with the laser beam. When scanning, the receiver is "opened" to detect signals back-scattered from atmospheric aerosol only at defined time instants which correspond to the arrival of signals of N radial measuring bases, the number of which is selected based on the required accuracy of determining wind direction. The obtained distributions are used to measure the size of atmospheric irregularities along each measuring base. Wind direction is determined as the direction of the measuring base, for which the dimensions of atmospheric irregularities differ the least at time t₁ and t₂, and the modulus of wind speed is determined using the expression:

where ρ_m is the spatial shift of atmospheric irregularities along the wind direction.

EFFECT: invention enables to reduce the volume of signal information required to determine wind speed and direction.

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Description

Technical field

The invention relates to measuring technique and can be used, in particular, in applied meteorology for operational remote measurement of wind speed and direction.

State of the art

The physical basis of laser measurements of wind speed is the ability of atmospheric aerosol to scatter radiation in all directions, including back to the direction of the laser locator. The randomly inhomogeneous structure of the atmospheric aerosol causes fluctuations in the signal received by the laser locator (which are thus a source of information about the inhomogeneous structure of the atmospheric aerosol). The transfer of aerosol inhomogeneities by wind makes it possible to measure wind speed by correlation methods.

Known methods for measuring the velocity of a gas stream and atmospheric wind, based on the registration of random implementations of scattered laser signals and further analysis of the measured random implementations or the results of their correlation processing [1-5].

в моменты времени t₁ и t₂, вычисляют взаимно корреляционную функцию этих двумерных пространственных распределений

находят вектор пространственного сдвига

соответствующий максимуму взаимно корреляционной функции, и определяют вектор скорости ветра

согласно выражению:

Closest to the proposed method is a laser remote method for measuring wind speed and direction [4], which consists in the fact that the atmosphere is irradiated with a horizontal scanning laser pulsed laser beam at times t ₁ and t ₂ = t ₁ + Δt (Δt is much longer scanning with a laser beam of the investigated spatial region), during scanning, the receiver records backscattering signals from atmospheric aerosol in the entire studied spatial region, and two-dimensional patterns of nstvennogo distribution coefficient inverse atmospheric aerosol scattering

at time t ₁ and t ₂ , calculate the cross-correlation function of these two-dimensional spatial distributions

find the spatial shift vector

corresponding to the maximum of the cross-correlation function, and determine the vector of wind speed

according to the expression:

Examples of two-dimensional realizations of the field of the spatial distribution of the coefficient of backward aerosol scattering of the atmosphere at time t ₁ and t ₂ are shown, respectively, in FIGS. 1 and 2, where the isolines show the cross section of the spatial distribution of the backward aerosol scattering coefficient by a plane. The arrow in the lower left corner indicates the direction of the wind. The rectangle shows the area within which the spatial distribution of the coefficient of backward aerosol scattering of the atmosphere is recorded.

The disadvantage of the method [4] (based on spatial correlation analysis) is the large amount of information about the field of the spatial distribution of the coefficient of inverse aerosol scattering of the atmosphere, which must be quickly stored and used to form correlation functions. This makes it difficult (it is necessary to use a large computer complex) or impossible (if a large computer complex cannot be used for some reason) to carry out operational measurements that require updating information with a frequency of several seconds.

Disclosure of invention

In operational measurements (when the time interval Δt is units of seconds), the spatial distribution field of the coefficient of back aerosol scattering of the atmosphere is practically not distorted, but only transferred in accordance with the direction and speed of the atmospheric wind. In this case, it is possible to significantly reduce the amount of signal information recorded during sounding of the atmosphere and then used to determine the speed and direction of the wind. This can be achieved using a special measurement method.

, измеряют размер атмосферных неоднородностей вдоль каждой измерительной базы, определяют направление ветра как направление измерительной базы, для которой размеры атмосферных неоднородностей наименее отличаются в моменты времени t₁ и t₂, определяют пространственный сдвиг ρ_m атмосферных неоднородностей вдоль направления ветра и определяют модуль скорости ветра V согласно выражению:

.It is possible to reduce the amount of recorded signal information by the fact that the atmosphere is irradiated with a horizontal scanning laser pulsed laser beam at times t ₁ and t ₂ = t ₁ + Δt (in this case, Δt is much longer than the laser beam scanning time of the investigated spatial region), during scanning, the receiver “Open” for recording backscattering signals from atmospheric aerosol only at certain points in time corresponding to the arrival of signals of N measuring bases (arranged radially, as shown in FIG. 3 for a variant of twelve measuring bases), while the number of radial measuring bases is selected based on the required accuracy Δφ of determining the wind direction:

measure the size of atmospheric inhomogeneities along each measuring base, determine the direction of the wind as the direction of the measuring base, for which the dimensions of atmospheric inhomogeneities are the least different at times t ₁ and t ₂ , determine the spatial shift ρ _{m of} atmospheric inhomogeneities along the wind direction and determine the wind speed module V according to the expression:

.

Enumeration of figures.

Figure 1, 2 - examples of two-dimensional implementation of the spatial distribution field of the coefficient of back aerosol scattering of the atmosphere, respectively, at time t ₁ and t ₂ ;

Fig.3, 4 are examples of a rectangular region within which the spatial distribution of the coefficient of back aerosol scattering of the atmosphere is recorded only along the radial lines of the measuring bases, respectively, at time t ₁ and t ₂ ;

5, 6 are examples of graphs of one-dimensional spatial distributions of the coefficient of back aerosol scattering of the atmosphere along the measuring bases.

The implementation of the invention

The volume of recorded signals is reduced for two reasons (see figure 3, 4):

- not all signal information in the studied area is stored, but information only along the measuring bases (they are shown by thin radial lines and, for example, drawn through 15 °, in the figures base aa is located along the direction of the wind, and base b-b is located along an arbitrary direction);

- the size of the region within which the spatial distribution of the coefficient of backward aerosol scattering of the atmosphere is recorded (it is shown as a rectangle in Figs. 3 and 4) is chosen much smaller than with spatial correlation analysis, since the proposed method is based on measuring the size of only one heterogeneities or several heterogeneities.

A device that implements the proposed method works as follows:

The remote wind speed and direction meter contains a laser radiation source transmitting an optical system, a deflector (scanning a laser beam in a horizontal plane), a receiving optical system, a photodetector, a control unit and a processing unit.

A laser meter irradiates the atmosphere with a horizontal scanning laser beam at times t ₁ and t ₂ = t ₁ + Δt. It is believed that scanning of the studied area is carried out in a time much smaller than Δt.

The aerosol always contained in the atmosphere scatters the radiation towards the receiver of the laser meter. The spatial resolution of the laser meter is determined by the angle of divergence of the laser beam, the distance from the meter to the scattering volume of the atmosphere and the pulse duration of the radiation source.

The received radiation passes through the receiving optical system, is recorded by the photodetector and enters the processing unit to determine the direction and magnitude of the wind speed.

.During scanning, the control unit “opens” the receiver to register backscattering signals from atmospheric aerosol only at certain (in time (synchronized with the scanning of the laser beam) time points corresponding to the arrival of signals of N measuring bases spaced apart by an angle

.

The moments of "opening" of the receiver are pre-determined (calculated) depending on a given number of measuring bases and the size of the investigated spatial region and entered into the control unit.

The following operations are performed sequentially in the signal processing unit of the laser meter:

в моменты времени t₁ и t₂ вдоль N измерительных баз.1. Register one-dimensional spatial distribution of the coefficient of back aerosol scattering of the atmosphere

at times t ₁ and t ₂ along N measuring bases.

The graphs of Figures 5 and 6 show examples of one-dimensional spatial distributions of α (X) (curves 1) along the measuring bases aa (Fig. 5) and bb (Fig. 6) at time t ₁ and t ₂ (measuring bases a a and bb are shown in FIGS. 3 and 4); 2 - a certain threshold value, the intersection of which with curves 1 determines the size of the aerosol inhomogeneities (as the size of the regions above line 2); X is the spatial coordinate along the corresponding measuring base. From the graphs of figure 5 and 6 it is clearly seen that:

- for the measuring base aa (coinciding with the direction of the wind), the one-dimensional spatial distributions α (X) (curves 1) at times t ₁ and t ₂ are simply shifted relative to each other along the X axis;

- for the measuring base bb (which does not coincide with the direction of the wind), the one-dimensional spatial distributions α (X) (curves 1) at times t ₁ and t ₂ turn out to be different.

2. The sizes of atmospheric inhomogeneities di (j, t ₁ ) and di (j, t ₂ ) are determined (by the intersection of the one-dimensional spatial distributions α (X) with a certain threshold value - see Figs. 5, 6) at times t ₁ and t ₂ along each measuring base (i is the aerosol inhomogeneity number, which is entirely located on the measuring base; j is the numerical or letter designation of the measuring base).

3. The direction of the wind is determined as the direction of the measuring base, for which the dimensions of atmospheric inhomogeneities (entirely located on the measuring base and at time t ₁ and at time t ₂ ) are the least different at time t ₁ and t ₂ . If there are no such inhomogeneities on any measuring base (which can be due to the high wind speed, when the inhomogeneities recorded at time t ₁ leave the investigated spatial region at time t ₂ ), then reduce the time interval t ₂ -t ₁ . If the situation does not change when the time interval t ₂ -t _{1 is} shortened, then the measurement is rejected and the wind speed is not measured.

From the graphs of figure 5 and 6 it is clearly seen that:

- for the measurement base aa, the dimensions of atmospheric inhomogeneities (located entirely on the measurement base at both time t ₁ and time t ₂ )

coincide (the coincidence is due to the fact that the wind direction for Fig. 5 exactly coincides with the direction of the measuring base aa; in the general case, when there is no such exact coincidence, the dimensions of atmospheric inhomogeneities moments of time t ₁ and t ₂ will be the least different for the measuring base closest to wind direction);

- for the measuring base bb, the dimensions of atmospheric inhomogeneities at time t ₁ and t _{2 are} very different.

4. Determine the spatial shift ρ _m (for example, by moving under the action of the wind the leading edge of one of the atmospheric inhomogeneities - for example, first in order, as shown in Fig. 5) along the wind direction and determine the wind speed module V according to the expression:

The described method allows to significantly reduce the amount of signaling information (about the spatial distribution field of the coefficient of inverse aerosol scattering of the atmosphere), which during operational measurements must be recorded and used to determine wind speed and direction.

The measuring device for implementing the method can be assembled from components and assemblies manufactured in the Russian Federation, and meets the criterion of "industrial applicability".

Information sources

1. PCT Application WO 2005/047908. Optical device and method for sensing multiphase flow. International Publication Date 05/26/2005. International Patent Classification G01P 5/22.

2. PCT Application WO 2006/063463. Optical transit time velocimeter. International Publication Date 06/22/2006. International Patent Classification G01P 5/20, G01P 5/26.

3. The use of correlation methods in atmospheric optics / V. M. Orlov, G. G. Matvienko, I. V. Samokhvalov, etc. - Novosibirsk: Nauka, 1983. - 160 p.

4. Correlation methods of laser-location measurements of wind speed / G. G. Matvienko, G. O. Zade, E. S. Ferdinandov et al. - Novosibirsk: Nauka, 1985. - P.163-179.

5. Matvienko GG, Samokhvalov IV, B.C. Rybalko et al. Operational determination of wind speed components using a lidar // Atmospheric and Ocean Optics. - 1988. - T.1. - N2. - S.68-72.

Claims (1)

The method of laser remote operational determination of wind speed and direction, which consists in the fact that the atmosphere is irradiated with a horizontal scanning laser pulsed laser beam at times t ₁ and t ₂ = t ₁ + Δt, while Δt is much longer than the laser scanning time of the spatial region under study , during scanning, the receiver is “opened” to register backscattering signals from atmospheric aerosol only at certain points in time corresponding to the arrival of signals of N measuring bases, located radially, while the number of radial measuring bases is selected based on the required accuracy Δφ of determining the direction of the wind:

measure the size of atmospheric inhomogeneities along each measuring base, determine the direction of the wind as the direction of the measuring base, for which the dimensions of atmospheric inhomogeneities are the least different at times t ₁ and t ₂ , determine the spatial shift ρ _{m of} atmospheric inhomogeneities along the wind direction and determine the wind speed module V according to the expression:

.

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