CN105785067A - Seawater flow velocity measurement method based on sonic propagation time difference - Google Patents

Abstract

The invention discloses a seawater flow velocity measurement method based on a sonic propagation time difference. The method is characterized in that a transducer A and a transducer B that are based on flow velocity measurement devices are used; a measurement acoustic axis is defined between the transducer A and the transducer B; and an acoustic path length is expressed by L, a flow velocity is expressed by v, a liquid acoustic speed is expressed by co, alpha expresses an included angel between a V and the acoustic axis direction, and the V expresses a flow velocity. The flow velocity measurement calculation is as follows: (1), the transducer A and the transducer B that serve as ultrasonic transmitters send acoustic pulses out simultaneously and then serve as ultrasonic receivers to receive acoustic pulses; (2), downstream propagation time tdown of an acoustic signal from the A to the B and upstream propagation time tup of the acoustic signal from the B to the A are measured, wherein the tdown and the tup meet a formula I; and a computational formula of a component of the flow velocity along the acoustic axis direction is deduced. According to the invention, the method has advantages of high precision, good cosine response, and wide application range; reflector containing by water is not required; and the flow velocity of the seawater including the reflector as well as the clean water flow velocity can be measured, so that the flow velocity measurement precision and response characteristics are enhanced substantially. Therefore, the application occasion of the flow velocity measurement technology is extended.

Description

Based on the method that ultrasonic transmission time difference surveys seawater velocity

Technical field

The present invention relates to a kind of method surveying seawater velocity based on ultrasonic transmission time difference.

Background technology

Traditional measures the predominantly organic tool method of method of seawater velocity, electromagnetic method, acoustic Doppler method.Wherein, Mechanical Method precision is low, low-response, can only survey two dimension flow velocity；Electromagnetic method certainty of measurement is relatively low, low-response, and energy consumption is high；Although acoustic Doppler method certainty of measurement is high, but requires to have in water reflector owing to testing the speed, therefore cannot measure clear water flow velocity.

Sea water also exists substantial amounts of scattering object, these scattering objects are with marine stream, namely their speed represent the speed of ocean current, the ultrasound wave of certain frequency launched by the ultrasonic transmitter (sound source) of doppler current meter in sea water, owing to there is " relative motion " between emitter and scattering object, according to Doppler effect, launch and exist for a frequency displacement between sound wave and scatter echo frequency, just can calculate seawater velocity by measuring frequency displacement.Acoustic Doppler velocity measurement technology is applied in ocean current measurement equipment, as: single-point type doppler current meter and ADCP, all adopt the transducer of several transceivers, first in sea water, launch the ping of certain frequency, then the echo that the scattering object in receiving sea water reflects, by calculating the frequency displacement launched between sound wave and scatter echo, so that it may record the flow velocity of sea water.But above method measurement data is inaccurate, calculate trouble, complex operation.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of method surveying seawater velocity based on ultrasonic transmission time difference.

In order to solve above-mentioned technical problem, the technical solution used in the present invention is: the method surveying seawater velocity based on ultrasonic transmission time difference.The method is based on two transducers of A, B of flow-speed measurement instrument, defines one and measure acoustic axis between two transducers of A, B, and sound travel path length is L, and rate of flow of fluid is ν, and liquid acoustic velocity is c_o, α is V and the axial angle of sound, and V is rate of flow of fluid；

Flow relocity calculation is as follows: (1) transducer A and transducer B is simultaneously emitted by ping as ultrasound transmitter device, then all receives ping as ultrasonic receiver；(2) acoustical signal downstream propagation times t from A to B is measured_down, adverse current propagation time t from B to A_up, then

$\left\{\begin{array}{c}{t}_{down}=\frac{L}{c_o+vcos\mathrm{\α}}\\ t_{up}=\frac{L}{c_o-vcos\mathrm{\α}}\end{array}\right\}$

Release the flow velocity computing formula along acoustic axis durection component

$vcos\mathrm{\α}=\frac{\mathrm{\Δ}t*{c_o}^2}{2*L}.$

Further, the present invention uses three non-coplanar acoustic axis of measuring can record the rate of flow of fluid v velocity component along three non-coplanar directions respectively, through Vector modulation, it is possible to record the size of rate of flow of fluid v and relative to the direction of flow-speed measurement instrument local Coordinate System.

Further, the present invention adopts three-dimensional electronic compass measurement flow rate to measure magnetic declination and the course angle of instrument, it is determined that the attitude of flow-speed measurement instrument, will change into the flow rate and direction relative to earth coordinates relative to the flow rate and direction of instrument local Coordinate System.

Precision of the present invention is high, and ultrasonic transmission time difference method can measure the three-dimensional flow of sea water, can accurately be measured the time difference of ultrasound wave adverse current and twice acoustic propagation of following current by time measuring circuit, and principle is simple, measures parameter accurate, can reach significantly high certainty of measurement.

Cosine response of the present invention is good, and the measurement chip of ultrasonic transmission time difference method employing is per second can measure million times, it is possible to measure fast-changing stream.

Applied range of the present invention, ultrasonic transmission time difference method tests the speed and does not require in water containing reflector, can not only measure the seawater velocity containing reflector, additionally it is possible to measure the flow velocity of clear water.

By the improvement of above three aspects, greatly add precision and the response characteristic of flow-speed measurement, expand the application scenario of flow-speed measurement technology.

Accompanying drawing explanation

Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.

Fig. 1 is the schematic diagram that the present invention surveys the method for seawater velocity based on ultrasonic transmission time difference.

Detailed description of the invention

Based on the method that ultrasonic transmission time difference surveys seawater velocity, the method is based on two transducers of A, B of flow-speed measurement instrument, as it is shown in figure 1, define one between two transducers of A, B to measure acoustic axis, sound travel path length is L, and rate of flow of fluid is ν, and liquid acoustic velocity is c_o, α is V and the axial angle of sound, has Fig. 1 to learn, α is 45 °, and V is rate of flow of fluid；

Measuring method: (1) transducer A and transducer B is simultaneously emitted by ping as ultrasound transmitter device, then all receives ping as ultrasonic receiver；(2) acoustical signal downstream propagation times t from A to B is measured_down, adverse current propagation time t from B to A_up, then

$\left\{\begin{array}{c}{t}_{down}=\frac{L}{c_o+vcos\mathrm{\α}}\\ t_{up}=\frac{L}{c_o-vcos\mathrm{\α}}\end{array}\right\}\→\left\{\begin{array}{c}{t}_{down}=\frac{L}{c_o+v\sqrt{2}/2}\\ t_{up}=\frac{L}{c_o-v\sqrt{2}/2}\end{array}\right\}$

Release the flow velocity computing formula along acoustic axis durection component

$vcos\mathrm{\α}=\frac{\mathrm{\Δ}t*{c_o}^2}{2*L}\→v\sqrt{2}/2=\frac{\mathrm{\Δ}t*{c_o}^2}{2*L}.$

Above ν can use three non-coplanar acoustic axis L that measure can record the rate of flow of fluid v velocity component along three non-coplanar directions respectively, through Vector modulation, it is possible to records the size of flow velocity v and relative to the direction of flow-speed measurement instrument local Coordinate System.

The present invention adopts three-dimensional electronic compass measurement flow rate to measure magnetic declination and the course angle of instrument, it is determined that the attitude of flow-speed measurement instrument, will change into the flow rate and direction relative to earth coordinates relative to the flow rate and direction of instrument local Coordinate System.

Precision of the present invention is high, and ultrasonic transmission time difference method can measure the three-dimensional flow of sea water, can accurately be measured the time difference of ultrasound wave adverse current and twice acoustic propagation of following current by time measuring circuit, and principle is simple, measures parameter accurate, can reach significantly high certainty of measurement.

Cosine response of the present invention is good, and the measurement chip of ultrasonic transmission time difference method employing is per second can measure million times, it is possible to measure fast-changing stream.

Applied range of the present invention, ultrasonic transmission time difference method tests the speed and does not require in water containing reflector, can not only measure the seawater velocity containing reflector, additionally it is possible to measure the flow velocity of clear water.

By the improvement of above three aspects, greatly add precision and the response characteristic of flow-speed measurement, expand the application scenario of flow-speed measurement technology.

The above; it is only embodiments of the invention; not the present invention is done any pro forma restriction; any those of ordinary skill in the art; without departing under technical solution of the present invention ambit; technical solution of the present invention is made many possible variations and modification by the method content utilizing the disclosure above, belongs to the scope of claims protection.

Claims (3)

1. the method surveying seawater velocity based on ultrasonic transmission time difference, it is characterized in that: the method is based on two transducers of A, B of flow-speed measurement instrument, defining one between two transducers of A, B and measure acoustic axis, sound travel path length is L, rate of flow of fluid is ν, and liquid acoustic velocity is c_o, α is V and the axial angle of sound, and V is rate of flow of fluid；

Flow relocity calculation is as follows: (1) transducer A and transducer B is simultaneously emitted by ping as ultrasound transmitter device, then all receives ping as ultrasonic receiver；(2) acoustical signal downstream propagation times t from A to B is measured_down, adverse current propagation time t from B to A_up,

Then

$\left\{\begin{array}{c}{t}_{down}=\frac{L}{c_o+\mathrm{\ν}cos\mathrm{\α}}\\ t_{up}=\frac{L}{c_o-\mathrm{\ν}cos\mathrm{\α}}\end{array}\right\}$

Release the flow velocity computing formula along acoustic axis durection component:

$\mathrm{\ν}cos\mathrm{\α}=\frac{\mathrm{\Δ}t*{c_o}^2}{2*L}.$

2. the method surveying seawater velocity based on ultrasonic transmission time difference according to claim 1, it is characterized in that: use three non-coplanar measurement acoustic axis can record the rate of flow of fluid ν velocity component along three non-coplanar directions respectively, through Vector modulation, it is possible to record the size of rate of flow of fluid ν and relative to the direction of flow-speed measurement instrument local Coordinate System.

3. the method surveying seawater velocity based on ultrasonic transmission time difference according to claim 1 and 2, it is characterized in that: adopt three-dimensional electronic compass measurement flow rate to measure magnetic declination and the course angle of instrument, determine the attitude of flow-speed measurement instrument, the flow rate and direction relative to earth coordinates will be changed into relative to the flow rate and direction of instrument local Coordinate System..