The present invention is a method of determining an induction factor of the wind for a wind turbine (1) equipped with a LiDAR sensor (2). For this method, wind speed measurements are performed in measurement planes (PM) by use of LiDAR sensor (2), then induction factors between measurement planes (PM) are determined by use of the measurements and of a first linear Kalman filter, and the induction factor between a measurement plane (PM) and the rotor plane (PR) of wind turbine (1) is determined by a second linear Kalman filter.

First to N-th (N is an integer of three or more) sensor elements each including a light source unit and a light reception unit are arranged around a tube that allows a fluid containing scatterers to flow at equiangular intervals, and coherent light which is emitted from the light source unit of any one sensor element of the first to N-th sensor elements and is transmitted through the fluid flowing through the tube is received by the light reception unit of another predetermined sensor element of the first to N-th sensor elements. At this time, when a distance between the light source unit and the light reception unit of any one sensor element is d and an outer radius of the tube is r, a distance between any one sensor element and another predetermined sensor element is set to πd/2 or more and √3r or less.

First to N-th (N is an integer of three or more) sensor elements each including a light source unit and a light reception unit are arranged around a tube that allows a fluid containing scatterers to flow at equiangular intervals, and coherent light which is emitted from the light source unit of any one sensor element of the first to N-th sensor elements and is transmitted through the fluid flowing through the tube is received by the light reception unit of another predetermined sensor element of the first to N-th sensor elements. At this time, when a distance between the light source unit and the light reception unit of any one sensor element is d and an outer radius of the tube is r, a distance between any one sensor element and another predetermined sensor element is set to πd/2 or more and √3r or less.

An apparatus for measuring fluid speed by using the refraction of light is disclosed. The apparatus includes: a channel in which a passage is formed to allow the flow of a fluid; a first and a second light source that are located in any one region of an upper part and a lower part of the channel; a sensor installed in an opposite region of the region where the first and second light sources are located with respect to the channel, to receive the light emitted from the first and second light sources; a speed calculation unit configured to calculate a speed of the fluid by using the intensity of the light received at the sensor.

An apparatus for measuring fluid speed by using the refraction of light is disclosed. The apparatus includes: a channel in which a passage is formed to allow the flow of a fluid; a first and a second light source that are located in any one region of an upper part and a lower part of the channel; a sensor installed in an opposite region of the region where the first and second light sources are located with respect to the channel, to receive the light emitted from the first and second light sources; a speed calculation unit configured to calculate a speed of the fluid by using the intensity of the light received at the sensor.

A laser radar device includes a multi-wavelength light oscillator to generate a plurality of light beams with different wavelengths, a plurality of modulation units to modulate each of the plurality of light beams with a modulation frequency altered according to a corresponding line of sight of emission, a transmitting/receiving optical system to emit each of the light beams modulated by the modulation units in a corresponding line of sight, and receive reflected light beams, an optical receiver to perform heterodyne detection by using the generated light beams and the received light beams corresponding to the generated light beams, and detect beat signals in the respective lines of sight, and a signal analyzing unit to calculate a value of Doppler wind speed in the respective lines of sight from the respective beat signals, and calculate a value of three-dimensional wind speed using the values of Doppler wind speed.

A laser radar device includes a multi-wavelength light oscillator to generate a plurality of light beams with different wavelengths, a plurality of modulation units to modulate each of the plurality of light beams with a modulation frequency altered according to a corresponding line of sight of emission, a transmitting/receiving optical system to emit each of the light beams modulated by the modulation units in a corresponding line of sight, and receive reflected light beams, an optical receiver to perform heterodyne detection by using the generated light beams and the received light beams corresponding to the generated light beams, and detect beat signals in the respective lines of sight, and a signal analyzing unit to calculate a value of Doppler wind speed in the respective lines of sight from the respective beat signals, and calculate a value of three-dimensional wind speed using the values of Doppler wind speed.

An apparatus for measuring fluid speed by using the refraction of light is disclosed. The apparatus includes: a channel in which a passage is formed to allow the flow of a fluid; a first and a second light source that are located in any one region of an upper part and a lower part of the channel; a sensor installed in an opposite region of the region where the first and second light sources are located with respect to the channel, to receive the light emitted from the first and second light sources; a speed calculation unit that calculates the speed of the fluid by using a time point at which the intensity of the light received at the sensor changes; and an adjustment unit that is connected to the channel and configured to adjust the flow speed of the fluid based on the calculated speed of the fluid.

An apparatus for measuring fluid speed by using the refraction of light is disclosed. The apparatus includes: a channel in which a passage is formed to allow the flow of a fluid; a first and a second light source that are located in any one region of an upper part and a lower part of the channel; a sensor installed in an opposite region of the region where the first and second light sources are located with respect to the channel, to receive the light emitted from the first and second light sources; a speed calculation unit that calculates the speed of the fluid by using a time point at which the intensity of the light received at the sensor changes; and an adjustment unit that is connected to the channel and configured to adjust the flow speed of the fluid based on the calculated speed of the fluid.

The general field of the invention is that of Doppler lidars intended to measure the speed of a target. The lidar according to the invention comprises: First means for modulating the optical frequency of the transmission signal, said frequency being the sum of a constant frequency and of a variable frequency of determined amplitude modulated by a periodic temporal function; Second means for computing the spectrum of the measured heterodyne signal and for creating two measurement spectra obtained by shifting the spectrum of the heterodyne signal by a positive and negative frequency value, said realignment frequency equal to the difference between the instantaneous frequency of the transmission signal and the frequency of a signal transmitted at a time shifted by the round-trip travel time between the lidar and the target; Third means for comparing the two measurement spectra, the difference in amplitude between the two spectra at the Doppler frequency determining the direction of the speed of the target.