An acoustic flow velocity measurement quality improvement method based on echo signal sliding splicing

Abstract

The application discloses an acoustic flow velocity measurement quality improving method based on echo signal sliding splicing, and relates to the technical field of acoustic Doppler velocity measurement. The method comprises the following steps: acquiring original echo signals continuously collected in an acoustic Doppler current meter measurement process, establishing a sliding window, extracting echo signals from the current measurement and adjacent measurements, and performing sliding splicing according to the measurement sequence to construct an enhanced echo signal sequence; then, performing correlation operation on the spliced echo signals by using a pulse pair algorithm, calculating a frequency difference, and obtaining a corresponding flow velocity; and continuously sliding the window to realize flow velocity output consistent with the original measurement frequency. The application improves the correlation of the echo signals, reduces the proportion of outliers in the flow velocity measurement, improves the effective rate of the flow velocity measurement, maintains the flow velocity output sampling frequency unchanged, and can better retain high-frequency turbulent information and turbulent energy spectrum structure.

Description

Technical Field

[0001] This invention relates to the field of acoustic Doppler velocimetry technology, and in particular to a method for improving the quality of acoustic flow velocity measurement based on echo signal sliding splicing. Background Technology

[0002] Acoustic Doppler current meters (ADVs) are widely used in turbulence measurement, hydrodynamic research, and monitoring of river, coastal, and marine environments. ADVs calculate fluid velocity by emitting ultrasonic pulses and receiving echo signals returned from scattering particles, based on the phase difference between consecutive pulses. In actual measurements, interference factors such as random particle motion, excessive water turbulence, and environmental noise reduce the correlation between echo signals. Low echo signal correlation can lead to increased measurement errors, specifically a higher proportion of outliers in the velocity sequence, decreased measurement efficiency, and distortion of turbulence statistics. Existing ADV devices typically employ an internal time averaging (TAP) process to average the velocity measurements from multiple consecutive measurements to improve reliability. However, this method averages outliers, increasing uncertainty in the output results, and significantly reduces the velocity sampling frequency; for example, a 5-times averaging reduces the original 100 Hz sampling frequency to 20 Hz.

[0003] For turbulence measurement, high-frequency pulsation analysis, and transient flow process research, a decrease in sampling frequency leads to the loss of important flow information. Therefore, current techniques struggle to simultaneously achieve both high measurement efficiency and high temporal resolution.

[0004] Currently, there is a lack of a flow velocity measurement method that can improve the quality of ADV measurements while maintaining a constant sampling frequency. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the quality of acoustic flow velocity measurement based on echo signal sliding splicing, aiming to solve or improve at least one of the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following solution: A method for improving the quality of acoustic velocity measurement based on echo signal sliding stitching includes: Step 1: Acquire the original continuous acoustic pulse echo signal during the ADV measurement process of the acoustic Doppler current meter; Step 2: For each measurement, the continuous acoustic pulse echo signal is extracted using a sliding window and spliced ​​to generate a spliced ​​echo signal. Step 3: Using the pulse pair algorithm, process the spliced ​​echo signal, calculate the frequency difference between the spliced ​​signals, and calculate the flow velocity based on the Doppler velocity measurement principle to obtain the calculated flow velocity; Step 4: Move the sliding window forward one measurement, repeat steps 2 and 3, and finally output the flow velocity sequence with the same sampling frequency as the original continuous acoustic pulse echo signal.

[0007] Furthermore, the width of the sliding window is set to an odd number.

[0008] Furthermore, the width of the sliding window ranges from 3 to 9.

[0009] Furthermore, a sliding window is used to extract and splice the continuous acoustic pulse echo signal to generate a spliced ​​echo signal, including: Based on the width of the sliding window Slide to extract the left and right sides of the current measurement. The frame echo signals are spliced ​​together to generate a spliced ​​echo signal.

[0010] Furthermore, the splicing is performed using an equal-weighted average method.

[0011] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention discloses a method for improving the quality of acoustic flow velocity measurement based on echo signal sliding splicing. The method increases the proportion of effective data in the flow velocity sequence without reducing the sampling frequency, thereby improving the quality of flow velocity measurement. Compared to traditional time-averaged processes, it has less impact on the turbulent energy spectrum structure and better preserves high-frequency turbulent information. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the continuous acoustic pulse echo signal acquisition process of the acoustic Doppler current meter in this embodiment; Figure 3 This is a schematic diagram of the sliding window extraction process in this embodiment; Figure 4 This is a schematic diagram illustrating how the proportion of outliers in the test data changes with the window width in this embodiment; Figure 5 This is a schematic diagram illustrating the variation trend of the time-averaged flow velocity with the window width in this embodiment; Figure 6 This is a schematic diagram illustrating the variation trend of turbulence intensity with window width in this embodiment; Figure 7 This is a schematic diagram comparing the turbulent kinetic energy spectrum of group A data at different window widths in this embodiment; Figure 8 This is a schematic diagram comparing the turbulent kinetic energy spectrum of group B data at different window widths in this embodiment; Figures 9-12 These are schematic diagrams comparing the turbulent kinetic energy spectra of group C data in this embodiment when the window width is 3, 5, 7, and 9. Figure 13 This diagram illustrates a comparison between the results of applying the method of this invention to the flow velocity sequence and the results of applying the moving average process in this embodiment. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The purpose of this invention is to provide a method for improving the quality of acoustic flow velocity measurement based on echo signal sliding splicing, aiming to solve or improve at least one of the above-mentioned technical problems.

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] like Figure 1 As shown, this invention provides a method for improving the quality of acoustic flow velocity measurement based on echo signal sliding stitching, comprising: Step 1: Acquire the original continuous acoustic pulse echo signal during the ADV measurement process of the acoustic Doppler current meter; Step 2: For each measurement, a sliding window is used to extract the continuous acoustic pulse echo signal and splice it to generate a spliced ​​echo signal, including: Based on the width of the sliding window Slide to extract the left and right sides of the current measurement. The frame echo signals are spliced ​​together to generate a spliced ​​echo signal.

[0018] Among them, the width of the sliding window Set to an odd number; splicing is performed using an equal-weighted average method.

[0019] Step 3: Using the pulse pair algorithm, process the spliced ​​echo signal, calculate the frequency difference between the spliced ​​signals, and calculate the flow velocity based on the Doppler velocity measurement principle to obtain the calculated flow velocity; Step 4: Move the sliding window forward one measurement, repeat steps 2 and 3, and finally output the flow velocity sequence with the same sampling frequency as the original continuous acoustic pulse echo signal.

[0020] To verify the beneficial effects of the method of the present invention, the following tests were conducted.

[0021] As shown in Table 1, the acoustic echo signals corresponding to the flow velocity data with three different sampling parameter settings were obtained.

[0022] Table 1

[0023] As attached Figure 2 As shown, ADV calculates the coherent echo signal. and The frequency difference between them is used to calculate the flow velocity. To output more stable flow rate results, ADV typically internally combines multiple measurements. , , …After averaging, the output not only reduces the sampling frequency, but the averaging process may also include measurement errors.

[0024] The method proposed in this invention is based on echo signal processing. By performing a moving average stitching on the echo signals and then using it for flow velocity calculation, the sampling frequency remains unchanged while improving the quality of the flow velocity data. Specifically, the original acoustic coherent echo signal during the flow velocity measurement process is first acquired. and , subscript The superscript 1 and 2 indicate the number of pulse pairs in the measurement.

[0025] like Figure 3 As shown, taking a sliding window width B=3 as an example, for the i-th measurement, the echo signal of the adjacent measurement is extracted. , and , The extracted signals are spliced ​​together according to the measurement order and pulse pair sequence number to construct a sliding spliced ​​echo signal. + + )and( + + ), where the start and end positions of the flow velocity data are ( )and( The measurement data from each measurement are then processed according to the echo signal from the i-th measurement, and further correlation operations are performed on the spliced ​​signal. A pulse pair algorithm is then used to perform correlation operations on the spliced ​​signal to calculate the frequency difference between the spliced ​​signals. Based on the Doppler velocimetry principle, the flow velocity is calculated to obtain the flow velocity. Furthermore, the flow rate sequence is output by sliding downwards from the starting position of the echo signal with a step size of 1, and the output is consistent with the original sampling frequency.

[0026] like Figure 4 As shown, the trend of outlier proportions with window width B is presented in three sets of data, where B=1 indicates that the data has not been processed by the method of this invention. (See Appendix...) Figure 4 As can be seen, the proportion of outliers gradually decreases as the window width increases, with a significant decrease when B=3.

[0027] like Figure 5 As shown, the time-averaged velocity in the turbulence statistics changes with the window width. After processing with the method of this invention, the turbulence intensity of the velocity sequence is slightly reduced, but the overall change is not significant.

[0028] like Figure 6 As shown, the trend of turbulence intensity as a function of window width is shown in the turbulence statistics parameters. The turbulence intensity is normalized using the initial turbulence intensity (before processing by the method of this invention). It can be seen that after processing by the method of this invention, the smaller the window width, the less obvious the decrease in turbulence intensity.

[0029] like Figure 7 and Figure 8 As shown, the turbulent kinetic energy spectra of groups A and B after processing with the method of the present invention are compared with different window widths. It can be seen that the method of the present invention does not significantly change the slope of the turbulent kinetic energy spectrum, and the noise level in the high frequency band is reduced.

[0030] like Figures 9-12 As shown, the turbulent energy spectrum of group C data before and after processing by the method of the present invention is compared at different window widths. It can be clearly seen that the noise level in the high-frequency range is reduced after processing by the method of the present invention.

[0031] like Figure 13 As shown, compared to directly applying the moving average process to the velocity sequence, the method of the present invention can more effectively preserve the turbulent structure.

[0032] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0033] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for improving the quality of acoustic velocity measurement based on echo signal sliding splicing, characterized in that, include: Step 1: Acquire the original continuous acoustic pulse echo signal during the ADV measurement process of the acoustic Doppler current meter; Step 2: For each measurement, the continuous acoustic pulse echo signal is extracted using a sliding window and spliced ​​to generate a spliced ​​echo signal. Step 3: Use the pulse pair algorithm to process the spliced ​​echo signal, calculate the frequency difference between the spliced ​​signals, and calculate the flow velocity based on the Doppler velocity measurement principle to obtain the calculated flow velocity; Step 4: Move the sliding window forward one measurement, repeat steps 2 and 3, and finally output the flow velocity sequence with the same sampling frequency as the original continuous acoustic pulse echo signal.

2. The method for improving the quality of acoustic velocity measurement based on echo signal sliding splicing according to claim 1, characterized in that, The width of the sliding window is set to an odd number.

3. The method for improving the quality of acoustic velocity measurement based on echo signal sliding splicing according to claim 2, characterized in that, The width of the sliding window ranges from 3 to 9.

4. The method for improving the quality of acoustic velocity measurement based on echo signal sliding splicing according to claim 1, characterized in that, The process of extracting and splicing continuous acoustic pulse echo signals using a sliding window to generate a spliced ​​echo signal includes: Based on the width of the sliding window Extract the left and right values ​​of the current measurement. The frame echo signals are spliced ​​together to generate a spliced ​​echo signal.

5. The method for improving the quality of acoustic velocity measurement based on echo signal sliding splicing according to claim 1, characterized in that, The splicing is performed using an equal-weighted average method.

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