Section suspended sediment concentration and flux change monitoring method based on acoustic chromatography technology

Abstract

The invention relates to the field of hydrological sediment monitoring, in particular to a section suspended sediment concentration and flux change monitoring method based on acoustic chromatography, which comprises the following steps: 1, data acquisition; 1.1), arranging equipment; 1.2) equipment debugging is carried out; 2, data acquisition; 3, data processing; 3.1) estimating a sound attenuation coefficient; 3.2) establishing the difference of the sound chromatography SNR and the concentration change (delta lt; sSCgt, SSCgt; ); 3.3) calibrating a system error e '; 3.4) calculating the concentration change of the suspended sediment; 3.5), calculating section flow; 4, outputting a monitoring result; on the basis of the principle of sound tomography sound reciprocity propagation, sound attenuation in the sound tomography sound propagation process is utilized, and through sound reciprocity propagation between two sound tomography stations, the relation between the difference of the signal-to-noise ratio (SNR) of received sound signals between the reciprocity stations and the concentration change of suspended sediment on the cross section is established; the suspended sediment concentration change of the whole section of the river can be directly observed, the monitoring range can be expanded, and the space-time effectiveness is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrological sediment monitoring, in particular to a method for monitoring changes in cross-section suspended sediment concentration and flux based on acoustic tomography technology. BACKGROUND

[0002] River suspended sediment transport is an important link of land-sea exchange. Achieving high-precision suspended sediment concentration monitoring of large cross-section is the basis of sediment transport research. At present, the monitoring of suspended sediment concentration in large river basins still mainly relies on field water sample observation or indirect observation of suspended sediment concentration at a certain point by using OBS, ADCP and other equipment. However, these methods have certain limitations, 1) field water sample observation consumes a lot of manpower and material resources; 2) OBS, ADCP and other indirect measurement methods need to be calibrated by field water samples to obtain concentration values, and the number of samples directly determines the credibility of the empirical relationship, which is difficult to be widely applied; 3) the measurement range of OBS, ADCP is limited, which is difficult to meet the needs of direct monitoring of large cross-section of large rivers; 4) conventional observation is difficult to implement in flood season due to high risk.

[0003] Therefore, it is necessary to propose a method for monitoring changes in cross-section suspended sediment concentration and flux based on acoustic tomography technology. SUMMARY

[0004] The present application aims to provide a method for monitoring changes in cross-section suspended sediment concentration and flux based on acoustic tomography technology, which can directly observe the changes in suspended sediment concentration of the entire cross-section of a river, making the observation more accurate and adaptable, and meeting the spatial and temporal effectiveness of direct cross-section monitoring to solve the technical defects and technical requirements that cannot be met.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a method for monitoring changes in cross-section suspended sediment concentration and flux based on acoustic tomography technology, comprising the following steps:

[0006] I. Preparation for monitoring

[0007] 1.1) Device arrangement

[0008] 1.2) Device debugging

[0009] II. Data acquisition

[0010] III. Data processing

[0011] 3.1) Estimating acoustic attenuation coefficient

[0012] 3.2) Establishing the difference between acoustic tomography SNR and changes in cross-section suspended sediment concentration (Δ <ssc>the relationship between the two

[0013] 3.3), calibrating system error e'

[0014] 3.4), calculating suspended sediment concentration variation

[0015] 3.5), calculating cross-section flow rate

[0016] IV. Monitoring result output

[0017] Preferably, in the step 1.1), the specific content of the device arrangement is: two acoustic tomography devices are arranged in the monitoring water area, ensuring that the two devices are located on the two banks of the river, and the line connecting the two devices forms a certain angle with the main flow direction of the river.

[0018] Preferably, in the step 1.2), the specific content of the device debugging is:

[0019] 1.2.1), setting the sound emission interval and sound load frequency of the acoustic tomography device, and the sound emission interval can be up to the minute level;

[0020] 1.2.2), the sound load frequency range is determined by the acoustic tomography device, and the specific sound frequency is set according to the on-site observation range, and the sound frequency is set such that the devices on the two banks of the river can effectively receive signals from the opposite bank, and the received signal-to-noise ratio intensity is not less than 10dB.

[0021] Preferably, in the step two), the data to be collected includes:

[0022] 2.1), collecting suspended sediment concentration water samples, monitoring the suspended sediment particle size, suspended sediment density, suspended sediment particle properties and other data of the monitoring water area, serving the estimation of the sound attenuation coefficient (ξ).

[0023] 2.2), obtaining the sound propagation time between the acoustic tomography observation stations and the sound signal data received by each station, serving the cross-section suspended sediment concentration variation monitoring model.

[0024] Preferably, in the step 3.1), the sound attenuation coefficient is estimated by using the following formulas (1)-(4) in combination with the suspended sediment particle parameters obtained in the step 2.1):

[0025] ξ = ξ v + ξ s (1)

[0026]

[0027] In the above formula, ξv represents viscous absorption, ξs represents scattering loss, the combination of which forms the sound attenuation coefficient, β represents the diffusion scale of viscous effect under the action of sound wave, s reflects the relative size of particle size and viscous diffusion scale, σ represents the density effect correction term related to particle size, k represents wave velocity, ρ s represents the density of suspended sediment, ρ represents the density of water body, a s represents the size of suspended sediment particle size, v represents the viscosity coefficient of water, w represents the angular frequency of incident sound wave, γ represents the coefficient of suspended particle properties (such as sandy).

[0028] Preferably, the specific content of step 3.2) is: referring to the sonar equation, based on the principle of bidirectional observation of acoustic tomography, due to the influence of flow velocity, the sound propagation time on the reciprocal path is different in each sound emission and receiving process, then the sound attenuation caused by suspended sediment on the reciprocal path is different; considering that the sound attenuation caused by sound absorption in the propagation of sound signal in water body is mainly caused by water body and suspended sediment, and the water body attenuation is mainly determined by sound frequency, therefore the water body attenuation on the reciprocal path can be considered consistent, that is, the difference of received sound signal (SNR) at each station is mainly caused by the inconsistency of suspended sediment concentration on the path, therefore the difference of acoustic tomography SNR and the change of cross section suspended sediment concentration (Δ <ssc>The relationship between the two is:

[0029]

[0030] 1→2 and 2→1 in the above formula respectively represent the direction from station 1 to station 2 and from station 2 to station 1, and the meaning of station 1 and station 2 is the position of the two acoustic tomography devices in step 1.1), < > represents the cross-sectional average, SNR1 and SNR2 respectively represent the received signal-to-noise ratio intensity at the two stations, R represents the distance between the two stations, ξ represents the acoustic attenuation coefficient caused by suspended sediment, and e' represents the difference caused by different sound sources, environment, etc. The value generally fluctuates around a certain fixed value when the monitoring area and instrument setting are fixed.

[0031] Preferably, in step 3.3), the specific content of calibrating the system error e' is: combining the artificial water sample suspended sediment concentration data in step 2.1) and the acoustic tomography observation data in step 2.2), and using formula (5) in step 3.2) to estimate the error e'.

[0032] Preferably, in step 3.4), the specific content of calculating the suspended sediment concentration change is: bringing the error e' obtained in step 3.3) into the acoustic tomography continuous observation data, and using formula (5) in step 3.2) to calculate the suspended sediment concentration change, thereby realizing the monitoring of the suspended sediment concentration change.

[0033] Preferably, in step 3.5), the specific content of calculating the end face flow is:

[0034] 3.5.1), the result directly observed by the acoustic tomography instrument is the two-way acoustic propagation time (t 1→2 ,t 2→1 );

[0035] 3.5.2), the distance L between the two stations can be calculated after the station layout is completed, and the cross-sectional average flow rate v = 2L / (t 1→2 +t 2→1 ) is calculated accordingly;

[0036] 3.5.3), the observed cross-sectional topography is obtained, and then the area A is obtained;

[0037] 3.5.4), the cross-sectional flow rate Q = v*A is calculated.

[0038] Preferably, in step four), the monitoring result is the product of the suspended sediment concentration change in step 3.4) and the cross-sectional flow rate in step 3.5.4).

[0039] In addition, it needs to be further explained and described in this application:

[0040] Theoretical derivation of the relationship between the difference of acoustic tomography SNR and the variation of cross-section suspended sediment concentration:

[0041] According to the acoustic equation, the acoustic signal intensity (SNR) at the receiving station can be expressed as:

[0042] SNR = SL - TL - NL (G1)

[0043] Where SL represents the sound source level, TL represents the acoustic propagation loss, and NL represents the noise.

[0044] Combining the principle of acoustic tomography bidirectional observation, assuming that there are two existing stations, formula (G1) can be further detailed as:

[0045] SNR1 = SL2 - 20 log R - α 2→1 R - L 2→1 - NL 2→1 + Gp (G2)

[0046] SNR2 = SL1 - 20 log R - α 1→2 R - L 1→2 - NL 1→2 + Gp (G3)

[0047] In the above formulas, 1→2 and 2→1 represent the direction from station 1 to station 2 and from station 2 to station 1, respectively, SNR1 and SNR2 represent the signal-to-noise ratio intensity received at the two stations, SL1 and SL2 represent the sound source intensity of the two stations, Gp represents the acoustic gain due to the use of M sequence in acoustic tomography, R represents the distance between the two stations (km), α represents the acoustic absorption coefficient; αR represents the total absorption loss caused by the water body and suspended sediment, and L is the other loss caused during the propagation process.

[0048] The propagation of acoustic signals in water is mainly caused by the water body and suspended sediment, where the absorption caused by the water body (α w ) is mainly determined by the acoustic frequency (f) and can be expressed as a function related to the frequency:

[0049] α w = fun(f) (G4)

[0050] The absorption caused by suspended sediment (α s ) can be expressed as:

[0051]

[0052] In the above formula, r represents the distance from the sound source, SSC(r) represents the suspended sediment concentration at a certain distance from the sound source, and ξ represents the acoustic attenuation coefficient caused by suspended sediment.

[0053] Since the acoustic tomography observes the average result of the cross section, the above formula (G4) is cross-section averaged, which can be further expressed as:

[0054] <α S > = ξ <ssc>(G6)

[0055] The < > in the above formulae indicates the cross-section average value.

[0056] In each emission and reception process, the sound propagation time on the reciprocity path is not the same due to the influence of flow velocity, and the sound attenuation caused by suspended sediment on the reciprocity path is also not the same, so formulae (G2) and (G3) are further evolved as:

[0057]

[0058] In the formula, e represents the change due to the difference of SL, L, NL, etc.

[0059] By combining formulae (G2)-(G6), formula (G7) can be further evolved as:

[0060]

[0061] Therefore, the cross-section suspended sediment concentration difference (Δ <ssc>) can be expressed as:

[0062]

[0063] e' represents the change due to SL, L, NL, etc.

[0064] The spatial coverage of the traditional method is limited, and the on-site monitoring is time-consuming and labor-intensive, especially during the flood season, the data acquisition rate is low, and the danger is also extremely high. The present application aims to break through the spatial limitation of the traditional method and provide a new technical means for suspended sediment monitoring in large river basins.

[0065] Sound waves can be transmitted over long distances in water bodies. During transmission, the characteristics of the sound signal will be affected by the water body. The basic principle of acoustic tomography technology is to use the characteristics of the received sound signal to invert the environmental factors of the water body. The transmission of sound signals in water bodies is easily affected by suspended sediment and attenuated. Reasonable use of sound signal attenuation can invert the average suspended sediment concentration changes between acoustic stations, and realize large-scale suspended sediment change monitoring.

[0066] Compared with the prior art, the present application has the following advantages:

[0067] 1. Based on the acoustic tomography acoustic reciprocity propagation principle, the present application uses the acoustic attenuation in the acoustic tomography acoustic propagation process, and establishes the relationship between the difference of the received sound signal signal-to-noise ratio (SNR) between the reciprocal stations and the change of the suspended sediment concentration of the section through the acoustic reciprocity propagation between two acoustic tomography stations. The suspended sediment concentration change of the whole section of the river can be directly observed, the monitoring range can be expanded, and the time and space effectiveness can be ensured.

[0068] 2. Based on the acoustic propagation principle, the sound signal can complete the transmission of the whole river section within seconds, and then realize the section observation. The present application can realize continuous high-frequency observation of a certain section, and has the ability of synchronous acquisition of section data.

[0069] 3. The present application can simultaneously realize the monitoring of the change of suspended sediment concentration and flux. On the one hand, the change of the suspended sediment concentration is obtained based on the difference of the sound signal-to-noise ratio, and on the other hand, the flow velocity of the section is obtained by means of the acoustic travel time principle, and the flow rate of the section is obtained by combining the flow velocity area method. The product of the flow rate and the concentration can realize the monitoring of the change of the suspended sediment flux.

[0070] 4. The acoustic attenuation coefficient is sensitive to the change of the particle size of the suspended sediment. In the present application, the change curve of the acoustic attenuation coefficient is introduced, the particle size change range of the monitoring area is obtained combined with the water sample data, the change curve of the acoustic attenuation coefficient of the suspended sediment particles in the monitoring area under a specific acoustic frequency is obtained, the time and space representativeness of the data is improved, and the present application can be applied to the monitoring in multiple water and sediment dynamic environments. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1 The overall logic diagram of the present application;

[0072] Figure 2 The distribution diagram of the acoustic tomography station of the present application on both banks of a river;

[0073] Figure 3 The actual distribution diagram of the acoustic tomography station in the embodiment of the present application;

[0074] Figure 4 The particle size distribution diagram of the three times suspended sediment and the variation curve of the viscous absorption (ξv), the scattering loss (ξs) and the total acoustic attenuation coefficient (ξ) under the frequency of 9kHZ in the embodiment of the present application.

[0075] Figure 5 The time sequence variation curve of the difference between the variation of the artificial sampling SSC and the cross-section suspended sediment concentration calculated by the acoustic tomography in the embodiment of the present application.

[0076] In the figure: the first acoustic tomography station site C1, the second acoustic tomography station site C2, the river flow direction →, the included angle θ between the river direction and the connecting line of the two acoustic tomography station sites. DETAILED DESCRIPTION

[0077] The technical solutions in the embodiments of the present application will be further described below with reference to the accompanying drawings. Figures 1-5 It should be apparent that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present application.

[0078] In the description of the present application, it should be understood that the terms "first", "second" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include one or more of the features.

[0079] Please refer to Figures 1-5 The embodiments of the present application:

[0080] Embodiments:

[0081] In the present embodiment, the method of the present application is further described in detail with the example of the field observation in the Nanjing section of the Yangtze River.

[0082] As Figures 1-3 shown: a cross-section suspended sediment concentration and flux variation monitoring method based on the acoustic tomography technology, comprising the following steps:

[0083] I. Monitoring preparation (selecting the monitoring area, laying the acoustic tomography station site)

[0084] 1.1), Device arrangement: Configure two acoustic tomography devices to monitor the water area, ensure that the two devices are located on both sides of the river, and the line connecting the two devices forms a certain angle with the main flow direction of the river.

[0085] 1.2), Device debugging;

[0086] 1.2.1), Set the sound emission interval and sound load frequency of the acoustic tomography device. The sound emission interval can be up to minutes;

[0087] 1.2.2), The sound load frequency range is determined by the acoustic tomography device. The specific sound frequency is set according to the observation range on site, and the sound frequency is set so that the devices on both sides of the river can effectively receive signals from the opposite shore, and the received signal-to-noise ratio intensity is not less than 10dB.

[0088] In this example, this step is mainly to select the monitoring area and layout the acoustic tomography station. The specific selection is in the Nanjing section of the Yangtze River, as shown in Figure 3 The cross-section length is 2994m, the observation interval is 3min, and the acoustic tomography frequency is 9kHz.

[0089] II. Data collection

[0090] 2.1), Collect suspended sediment concentration water samples, monitor the suspended sediment particle size, suspended sediment density, and suspended sediment particle properties of the water area;

[0091] In this example, the content of this step is mainly to collect the position data of the acoustic tomography installation, the cross-section length, and the manual sediment sampling water sample data (including concentration and sediment particle size).

[0092] 2.2), Obtain the sound propagation time between the acoustic tomography observation stations and the sound signal data received by each station;

[0093] In this example, the content of this step is mainly to process the acoustic tomography data and obtain the signal-to-noise ratio (SNR) and sound propagation time of the acoustic tomography stations.

[0094] III. Data processing

[0095] 3.1), Estimate the sound attenuation coefficient;

[0096] Use the following formulas (1)-(4) to estimate the sound attenuation coefficient combined with the suspended sediment particle parameters obtained in step 2.1):

[0097] ξ = ξ v + ξ s (1)

[0098]

[0099] In the above formula, ξv represents viscous absorption, ξs represents scattering loss, and the two are combined into the sound attenuation coefficient, β represents the diffusion scale of viscous effect under the action of sound waves, s reflects the relative size of particle size and viscous diffusion scale, σ represents the density effect correction term related to particle size, k (k = 2π / (1500 / f)) represents the wave speed, ρ s represents the density of suspended sediment, and is taken as 1225 kg / m 3 , ρ represents the density of the water body, taken as 1000 kg / m3, a s (range 0.1-10 5 microns) represents the particle size of suspended sediment, v represents the viscosity coefficient of water, w (w = 2πf) represents the angular frequency of the incident sound wave, γ represents the coefficient of suspended particle properties (such as sandy), taken as 0.18, and the sound attenuation coefficient curve under f = 9 kHz in the present example is calculated, and the specific results are shown in Figure 4 , where (a) is a three-suspended sediment particle size distribution diagram, (b) is a curve of viscous absorption (ξv), scattering loss (ξs), and the sum of the two sound attenuation coefficients (ξ) under 9 kHz frequency, the sound attenuation coefficient change range in this area can be obtained according to the particle size change range, and the change range is not large in the present example, and the average value can be used in the subsequent suspended sediment model.

[0100] In the present embodiment, this step is mainly to calculate the sound attenuation coefficient curve under a specific sound frequency according to the above formulas (1)-(4), and to obtain the sound attenuation coefficient value or range corresponding to the particles in the current monitoring area in combination with the particle size results of the known water sample data.

[0101] 3.2), the difference of the sound tomography SNR and the change (Δ <ssc>the relationship between the two;

[0102] Based on the principle of acoustic tomography bidirectional observation, the difference of acoustic tomography SNR is established as a function of the change of cross-section suspended sediment concentration (Δ <ssc>The relationship between the two is:

[0103]

[0104] In the above formula, 1→2 and 2→1 represent the direction from station 1 to station 2 and from station 2 to station 1, respectively, and station 1 and station 2 represent the positions of the two acoustic tomography devices in step 1.1). The <> represents the cross-sectional average, SNR1 and SNR2 represent the received signal-to-noise ratio intensities at the two stations, R represents the distance between the two stations, ξ represents the acoustic attenuation coefficient caused by suspended sediment, and e' represents the difference caused by different sound sources, environments, etc.

[0105] In this embodiment, the result directly observed by the acoustic tomography instrument is the two-way acoustic propagation time (t 1→2 ,t 2→1 ); The specific calculation of the SNR value is: the peak value of the acoustic signal received by the acoustic tomography divided by the average value of the signal in that segment, i.e. SNR is defined. The SNR is a relative variable concept. Similar to the acoustic propagation time, the two-way SNR value (SNR 1→2 ,SNR 2→1 ) can also be obtained.

[0106] 3.3), rate the system error e';

[0107] Combined with the artificial water sample suspended sediment concentration data in step 2.1), the acoustic tomography observation data in step 2.2), and using formula (5) in step 3.2), the error e' is estimated.

[0108] 3.4), calculate the suspended sediment concentration change;

[0109] The error e' obtained in step 3.3) is brought into the acoustic tomography continuous observation data, and the suspended sediment concentration change is calculated using formula (5) in step 3.2), and then the suspended sediment concentration change monitoring is realized.

[0110] In this embodiment, specifically, combined with the SNR value in step 3.2), the acoustic attenuation coefficient (ξ) value in step 3.1), and the cross-sectional length in step 1), (SNR 2→1 -SNR 1→2 ) / (ξR) can be calculated. There is a system error between this term and the final suspended sediment concentration change value. The difference between the time series SSC data of the artificial water sample and its mean value is considered as the suspended sediment concentration change value. The difference between the acoustic tomography result (SNR 2→1 -SNR 1→2 ) / (ξR) is the error e'.

[0111] The specific results are as follows:

[0112] Table 1: Results of System Error Calibration Based on Manual Sampling Data

[0113]

[0114]

[0115] As shown in the fourth column of Table 1, the error variation is very small, with a mean of 0.0016. Figure 5 As shown, the trends of suspended sediment concentration observed by the two methods are almost identical, which also proves the reliability of the suspended sediment concentration changes calculated by acoustic tomography.

[0116] 3.5) Calculate the cross-sectional flow rate;

[0117] 3.5.1) The result directly observed by the acoustic tomography instrument is the two-way sound propagation time (t). 1→2 ,t 2→1 );

[0118] 3.5.2) After the station locations are set up, the distance L between two stations can be calculated, and the average flow velocity of the cross-section v = 2L / (t) can be calculated accordingly. 1→2 +t 2→1 );

[0119] 3.5.3) Obtain the topography of the observation section, and then calculate the area A;

[0120] 3.5.4) Calculate the cross-sectional flow rate Q = v * A.

[0121] In this embodiment, specifically, the flow rate of the acoustic tomography section is estimated based on the velocity-area method, and the flux change is obtained by combining the changes in suspended sediment concentration at the section. The results are shown in Table 2 below:

[0122] Table 2: Results of acoustic tomography cross-section monitoring

[0123]

[0124] Table 2 shows the monitoring of suspended sediment concentration and flux changes at cross sections using acoustic tomography based on this invention. It should be noted that the Nanjing cross section in this example is a tidal section; therefore, the positive and negative values ​​of the acoustic tomography results also indicate direction: positive values ​​indicate positive sediment transport due to runoff influence, while negative values ​​indicate sediment transport influenced by tidal forces.

[0125] In this embodiment, the overall logic in step 3) can be understood as follows: First, establish a monitoring model for changes in suspended sediment concentration using acoustic tomography, that is, first calculate the bidirectional received acoustic signal-to-noise ratio difference according to the above formula (5), and then calculate the result in step 2.2. The system error is calibrated again combined with the concentration result of the artificial sampling water sample. There is a difference between the result of each artificial sampling and the acoustic tomography result. When the water sample is enough, the change curve of the system error (e') can be given, and the average value is generally obtained. Finally, the system error (e') is substituted into the model, and the change of the cross-section suspended sediment concentration can be obtained through continuous observation. The cross-section flow rate is estimated, the acoustic propagation time of the acoustic tomography is obtained, and the cross-section average flow rate is calculated. The cross-section flow rate is calculated by using the flow rate area method.

[0126] IV. Output of the monitoring result.

[0127] The monitoring result is the product of the change of the suspended sediment concentration in step 3.4) and the cross-section flow rate in step 3.5.4).

[0128] In the embodiment, the output content of the monitoring result is specifically the data content in the last column of Table 2, that is, the change of the cross-section suspended sediment flux (kg / s) of the acoustic tomography.

[0129] In the embodiment, the logic of step IV can be understood as follows: according to the above steps, the signal-to-noise ratio value of the acoustic signal obtained by the acoustic tomography is substituted into the model to obtain the continuous change of the suspended sediment concentration of the large cross-section, and the product of the change of the suspended sediment concentration and the flow rate is calculated by combining the flow rate result monitored by the acoustic tomography, so that the change of the suspended sediment transport of the large cross-section of the river can be obtained.

[0130] The embodiment is based on the acoustic reciprocity propagation principle of the acoustic tomography. The change of the suspended sediment concentration of the whole cross-section of the river can be directly observed by using the acoustic attenuation in the acoustic propagation process of the acoustic tomography, establishing the relationship between the difference of the received acoustic signal signal-to-noise ratio (SNR) between the reciprocal stations and the change of the cross-section suspended sediment concentration, and through the acoustic reciprocity propagation between the two acoustic tomography stations. The conventional observation technology can only realize point observation. If the cross-section change is to be captured, the walk-by observation needs to be used. The maximum observation range of the horizontal ADCP is only 300 m, and the time and space effectiveness is difficult to guarantee. The time and space effectiveness of the conventional suspended sediment observation technology cannot meet the direct monitoring of the cross-section.

[0131] The basic principles and main features of the present application and the advantages of the present application are shown and described above. It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0132] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature described. The specification can include implicit combinations of explicitly mentioned features and / or explicit combinations of implicitely mentioned features. Each embodiment depends on the explicit combinations of features and / or the implicit combinations of features made in that embodiment, and each such embodiment can be combined with every other such embodiment to create further embodiments.< / ssc> < / ssc> < / ssc> < / ssc> < / ssc> < / ssc>

Claims

1. A method for monitoring changes in suspended sediment concentration and flux across a cross section based on acoustic tomography, characterized by comprising the following steps: I. Monitoring Preparation 1.1) Equipment layout; 1.2) Equipment debugging; II. Data Collection III. Data Processing 3.1) Estimate the sound attenuation coefficient; 3.2) Establish the relationship between the difference in acoustic tomography SNR and the change in suspended sediment concentration at the cross section (Δ). <ssc> The connection between );< / ssc> 3.3) Calibration systematic error e'; 3.4) Calculate the changes in suspended sediment concentration; 3.5) Calculate the cross-sectional flow rate; IV. Output of monitoring results.

2. The method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography as described in claim 1, characterized in that, In step 1.1), the specific content of the equipment arrangement is as follows: two acoustic tomography devices are configured to monitor the water area, ensuring that the two devices are located on both banks of the river, and the line connecting the two devices forms a certain angle with the main flow direction of the river.

3. The method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography according to claim 2, characterized in that, In step 1.2), the specific content of equipment debugging is as follows: 1.2.1) Set the sound emission interval and sound load frequency of the acoustic tomography equipment; the sound emission interval can be down to the minute level. 1.2.2) The frequency range of the acoustic load is determined by the acoustic tomography equipment. The specific acoustic frequency is set according to the field observation range, and the acoustic frequency is such that the equipment on both sides of the river can effectively receive the signal from the opposite bank, and the received signal-to-noise ratio is not less than 10dB.

4. A method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography, as described in claim 1, 2, or 3, characterized in that... In step two), the data to be collected includes: 2.1) Collect water samples of suspended sediment concentration, monitor the particle size, density, and properties of suspended sediment particles in the water area; 2.2) Obtain the sound propagation time between stations and the sound signal data received at each station in the acoustic tomography observation.

5. The method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography according to claim 4, characterized in that, In step 3.1), the sound attenuation coefficient is estimated using the following formulas (1)-(4) in combination with the parameters such as suspended sediment particles obtained in step 2.1): ξ=ξ v +ξ s (1) In the above formula, ξv represents viscous absorption, ξs represents scattering loss, and the two combine to form the sound attenuation coefficient. β represents the diffusion scale of the viscous effect under the action of sound waves, s reflects the relative magnitude of particle size and viscous diffusion scale, σ represents the density effect correction term related to particle size, k represents the wave velocity, and ρ... s ρ represents the density of suspended sediment, ρ represents the density of water, and a represents the density of suspended sediment. s γ represents the size of suspended sediment particles, v represents the viscosity coefficient of water, w represents the angular frequency of the incident sound wave, and γ represents the coefficient of suspended particle properties.

6. The method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography according to claim 5, characterized in that, The specific content of step 3.2) is as follows: Referring to the sonar equation and based on the principle of two-way acoustic tomography, establish the relationship between the difference in acoustic tomography SNR and the change in suspended sediment concentration at the cross section (Δ). <ssc> The connection between them:< / ssc> In the above formula, 1→2 and 2→1 represent the directions from station 1 to station 2 and from station 2 to station 1, respectively. Station 1 and station 2 refer to the positions of the two acoustic tomography devices in step 1.1). <> represents the cross-sectional average. SNR1 and SNR2 represent the signal-to-noise ratio received at the two stations, respectively. R represents the distance between the two stations. ξ represents the sound attenuation coefficient caused by suspended sediment. e' represents the difference caused by different sound sources, environment, etc.

7. The method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography according to claim 6, characterized in that, In step 3.3), the specific content of calibrating the system error e' is as follows: combining the artificial water sample suspended sediment concentration data in step 2.1) and the acoustic tomography observation data in step 2.2), the error e' is estimated using formula (5) in step 3.2).

8. The method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography according to claim 7, characterized in that, In step 3.4), the specific content of calculating the change in suspended sediment concentration is as follows: the error e' obtained in step 3.3) is substituted into the continuous observation data of acoustic tomography, and the change in suspended sediment concentration is calculated using formula (5) in step 3.2), thereby realizing the monitoring of the change in suspended sediment concentration.

9. The method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography as described in claim 8, characterized in that, In step 3.5), the specific content of calculating the end face flow rate is as follows: 3.5.1) The result directly observed by the acoustic tomography instrument is the two-way sound propagation time (t). 1→2 ,t 2→1 ); 3.5.2) After the station locations are set up, the distance L between two stations can be calculated, and the average flow velocity of the cross-section v = 2L / (t) can be calculated accordingly. 1→2 +t 2→1 ); 3.5.3) Obtain the topography of the observation section, and then calculate the area A; 3.5.4) Calculate the cross-sectional flow rate Q = v * A.

10. The method for monitoring cross-sectional suspended sediment concentration and flux changes based on acoustic tomography according to claim 9, characterized in that, In step four), the monitoring result is the product of the change in suspended sediment concentration in step 3.4) and the flow rate at the cross-section in step 3.5.4).

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