Turbulent water flow velocity detection method based on Doppler effect

Abstract

The invention relates to a turbulent water body detection method, in particular to a turbulent water body flow velocity detection method based on a Doppler effect, and solves the defect that no deep sea turbulent water body profile flow velocity detection means exists in the prior art. According to the detection method provided by the invention, laser detection is adopted, a laser signal is divided into a measuring beam and a reference beam, backward scattering echo beams generated by the measuring beam in different sections of a to-be-detected water body and the reference beam are subjected to beat frequency interference, and a generated beat frequency interference signal is converted into an electric signal for operation; the turbulent water body profile flow velocity is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of turbulent water body detection methods, and in particular to a turbulent water body flow velocity detection method based on the Doppler effect. Background Art

[0002] Turbulence is an important physical ocean phenomenon that reflects the material circulation and energy transfer process of the ocean and is of great significance to ocean research. Due to the high nonlinearity and extreme asymmetry of turbulence, it is impossible to simulate the complete and accurate turbulent motion process numerically, so the study of turbulence is mainly based on a large amount of field observation data.

[0003] The violent mixing and diffusion process of deep-sea turbulence plays an important regulatory role in the global ocean material circulation and energy balance, global weather and climate change, and profoundly affects the ocean's ability to absorb excess heat and carbon dioxide in the atmosphere under the background of global warming. Therefore, the study of deep-sea turbulent activities has always been a hot topic in global ocean research.

[0004] At present, the turbulent kinetic energy-turbulent dissipation rate model (k-ε model) based on the Reynolds average method is often used to approximate turbulence and its mixing and diffusion processes. The turbulent kinetic energy and turbulent dissipation rate that characterize the turbulent process are both determined by the turbulent flow velocity, so flow velocity observation data is crucial to turbulence research.

[0005] Traditional turbulence observation instruments include turbulence profilers, point acoustic Doppler current meters, and acoustic Doppler profile current meters. Turbulence profilers can obtain the dissipation rate of turbulence by measuring velocity shear, but cannot calculate turbulent kinetic energy; point acoustic Doppler current meters can obtain the dissipation rate of turbulence by repeatedly detecting a single point at high frequency, but can only measure the velocity at a single point, and cannot obtain the three-dimensional flow field information of turbulence, so the data validity is low.

[0006] The acoustic Doppler profile current meter can obtain the turbulent dissipation rate and turbulent kinetic energy by detecting the three-dimensional velocity of turbulence. It can not only observe the intensity of turbulent activity, but also explain to a certain extent the reasons for the strength of turbulent activity. The acoustic Doppler profile current meter detects the profile velocity by receiving the acoustic scattering echoes caused by plankton, suspended particles and bubbles. However, in deep sea areas, the content of scatterers such as plankton and suspended particles is extremely low, and the intensity of acoustic scattering echoes cannot meet the minimum signal-to-noise ratio requirements of high-frequency acoustic Doppler profile current meters. Therefore, the acoustic Doppler profile current meter cannot be used in the deep sea, which limits its research on deep-sea turbulence.

[0007] In view of the insufficient observation capabilities of the above-mentioned instruments, it is necessary to propose a detection method that can effectively realize the observation of deep-sea turbulent activities. Summary of the invention

[0008] The purpose of the present invention is to solve the technical problem that there is no means for detecting the flow velocity of deep-sea turbulent water profile in the prior art, and to provide a method for detecting the flow velocity of turbulent water profile based on the laser Doppler effect.

[0009] The present invention provides a turbulent water body flow velocity detection method based on the Doppler effect, comprising the following steps:

[0010] Step 1, divide the continuous laser signal emitted by the laser into two beams, one beam is recorded as a measurement beam, and the other is recorded as a reference beam;

[0011] Step 2, modulating the measuring light beam into a pulse light beam, and irradiating the pulse light beam to the water body to be measured (8);

[0012] Step 3, the pulse light beam generates backscattered echo light beams at different sections in the water body to be measured, and the backscattered echo light beams are received to cause beat frequency interference with the reference light beam to generate beat frequency interference signals;

[0013] Step 4: convert the beat frequency interference signal into an analog electrical signal, and transmit the analog electrical signal to a signal processing system;

[0014] Step 5: Use the signal processing system to extract the Doppler frequency shift of the analog electrical signal, and calculate the flow velocity of each section of the water body to be measured by the following formula:

[0015]

[0016] Among them, v is the flow velocity of each section;

[0017] f is the Doppler frequency shift of each profile;

[0018] λ is the wavelength of the continuous laser signal emitted by the laser.

[0019] The present invention provides a method for detecting flow velocity of turbulent water bodies based on the Doppler effect, wherein in step 1, the wavelength of the continuous laser signal emitted by the laser is 460nm-550nm.

[0020] The present invention provides a turbulent water body velocity detection method based on the Doppler effect, which further comprises:

[0021] Step 6: The flow velocity v of each section of the water body to be measured calculated by the signal processing system is transmitted to the data storage system for storage.

[0022] The difference between the turbulent water body flow velocity detection method based on the Doppler effect of the present invention and the prior art is that the turbulent water body flow velocity detection method based on the Doppler effect of the present invention can detect small-scale turbulent flow velocity: the laser has good collimation, the detection beam width will be effectively compressed and there is no side wave interference, and a higher horizontal resolution can be achieved, thereby realizing effective observation of turbulence.

[0023] The turbulent water velocity detection method based on the Doppler effect of the present invention can be applied to deep-sea environments: the wavelength of the laser is shorter, and its echo signal includes not only the Mie scattering echo caused by suspended particles, but also the Rayleigh scattering echo caused by water molecules. Even when the concentration of suspended particles in the deep sea is extremely low, the scattered echo signal can be received, thereby enabling effective detection of the profile velocity of deep-sea turbulent water bodies. DETAILED DESCRIPTION

[0024] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0025] A method for detecting flow velocity of a turbulent water body based on the Doppler effect comprises the following steps:

[0026] Step 1, the laser emits a continuous laser signal with a wavelength of 460nm-550nm, which is divided into two beams by the first laser beam splitter, the beam passing through the laser modulator is recorded as the measurement beam, and the other beam is recorded as the reference beam;

[0027] Step 2: The laser modulator modulates the measuring beam into a pulse beam, and the pulse beam is split by the second laser beam splitter and then emitted by the laser transceiver system to irradiate the water body to be measured;

[0028] Step 3: The pulsed light beam generates backscattered echo light beams at different sections in the water body to be measured, which are received by the laser transceiver system and transmitted to the third laser beam splitter via the second laser beam splitter, where they generate beat frequency interference with the reference light beam passing through the third laser beam splitter to generate a beat frequency interference signal;

[0029] Step 4: The photodetector receives the beat frequency interference signal, converts it into an analog electrical signal, and transmits it to the signal processing system;

[0030] Step 5: Use the signal processing system to extract the Doppler frequency shift of the analog electrical signal, and calculate the flow velocity of each section of the water body to be measured by the following formula:

[0031]

[0032] Among them, v is the flow velocity of each section;

[0033] f is the Doppler frequency shift of each profile;

[0034] λ is the wavelength of the continuous laser signal emitted by the laser;

[0035] Step 6: After the signal processing system calculates the flow velocity v of each section of the water body to be measured, the flow velocity detection data is transmitted to the data storage system for storage.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for detecting the flow velocity of a turbulent water body based on the Doppler effect, characterized in that: The following steps are involved: Step 1, divide the continuous laser signal emitted by the laser into two beams, one beam is recorded as a measurement beam, and the other is recorded as a reference beam; Step 2, modulating the measuring beam into a pulse beam, and irradiating the pulse beam to the water body to be measured; Step 3, the pulse light beam generates backscattered echo light beams at different sections in the water body to be measured, and the backscattered echo light beams are received to cause beat frequency interference with the reference light beam to generate beat frequency interference signals; Step 4: convert the beat frequency interference signal into an analog electrical signal, and transmit the analog electrical signal to a signal processing system; Step 5: Use the signal processing system to extract the Doppler frequency shift of the analog electrical signal, and calculate the flow velocity of each section of the water body to be measured by the following formula: Where, v is the flow velocity of each section; f is the Doppler frequency shift of each profile; λ is the wavelength of the continuous laser signal emitted by the laser.

2. The method for detecting turbulent water velocity based on the Doppler effect according to claim 1, characterized in that: In step 1, the wavelength of the continuous laser signal emitted by the laser is 460nm-550nm.

3. The method for detecting turbulent water velocity based on the Doppler effect according to claim 1 or 2, characterized in that: Also includes: Step 6: The flow velocity v of each section of the water body to be measured calculated by the signal processing system is transmitted to the data storage system for storage.

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