Method for measuring acoustic characteristics of physical model during movement

Abstract

FIELD: hydroacoustics.SUBSTANCE: method for measuring the acoustic characteristics of a marine object with a propeller consists of the movement of the test object near measuring devices and the accumulation of experimental data, the accumulation of experimental data of the primary and secondary acoustic fields, the determination of the frequency dependencies of the levels and direction of acoustic radiation, for which purpose the measuring trajectories are repeatedly repeated by a self-propelled model on a testing ground near or around the measuring devices installed in a line, the formation of a model of the acoustic field and acoustic characteristics of the marine object using the created digital acoustic twin and a physical scale model of the object, the validation of the digital acoustic twin on the physical scale model during the testing ground acoustic measurements, the separation of the object's field from noise by the method of coordinated energy processing of measurement data with a model pass-through characteristic and incoherent summation of signals from all measuring devices during the formation of a model of the pass-through characteristic based on the calculated data of the digital acoustic twin of the object.EFFECT: expansion of the capabilities for analysing acoustic characteristics and designing marine facilities with specified acoustic characteristics.5 cl, 2 dwg

Description

[0001] The invention relates to the field of hydroacoustics and can be used to obtain experimental data on the characteristics of the primary and secondary acoustic fields of low-noise marine objects with a reduced signal-to-noise ratio in shallow waters with strong reverberation interference, as well as to validate the calculated vibroacoustic characteristics of a digital twin of a marine object based on the results of testing a large-scale physical model of the object.

[0002] A known method for determining the vibroacoustic characteristics of offshore objects is aimed at determining the contribution of variable forces acting on the hull structures to the external acoustic field. For this purpose, the object is placed in the environment at a selected distance from the pulsed sound source. A pulse source with a known volumetric acceleration, for example a small explosive charge, is installed in such a way that the difference in the arrival time of acoustic pulses reflected from the boundaries of the environment to the object, compared to the direct one, would be maximal. Then, a sound pulse is emitted and the vibration response (vibration acceleration) on the hull of the object is recorded. After appropriate processing, the values ​​​​of the hydroacoustic field excited to the hull structures of the object are obtained, without the influence of the boundaries (in an infinite space) (patent RU 2659891 "Method for determining the structure of the hydroacoustic field of man-made underwater objects from hull vibrations", IPC G01V1 / 00, published 04.07.2018). The disadvantages of this method include the need to use powerful pulsed radiation sources, the inability to obtain high-resolution frequency characteristics, and the inability to study the contribution of hydrodynamic noise sources, such as flow noise around the hull.

[0003] A known method for measuring the acoustic field of offshore objects using energy-matched processing (EMP) is based on the application of an algorithm for calculating the correlation function, where two functions of different origin are compared - the measured pass-through characteristic and the calculated function corresponding to a specific model of the object's hull radiation ("New Approaches and Modern Methods in Measuring Hydroacoustic Offshore Objects" by V.I. Teverovsky, S.G. Tsygankov, Almanac of Modern Metrology, 2014). A disadvantage of this method is its low noise immunity under conditions of pulsed and uncorrelated interference, as well as non-stationary interference within the time of recording the passage of a offshore object. The dynamic range of analysis by the EMP method depends on the properties of the random non-stationarity of the interference, the amplitude and width of the fluctuation "bursts" of the interference.To increase the dynamic range of measurements, it is recommended to process the characteristic using the ESO method by averaging over several passes of the object. A fundamental drawback is the need to use a computational field model, which requires preliminary validation for a specific object.

[0004] A known method for increasing noise immunity is the accumulation of a trajectory-based pass-through characteristic—energy-consistent trajectory processing (ECTP) ("Statistical Measurements and Signal Detection," Novikov A.K., St. Petersburg: Krylov Central Research Institute, 2006, pp. 151-154). The ETP method assumes that measurements are taken using N receivers arranged in a line parallel to the direction of motion of the measured object. For each receiver, pass-through characteristics are formed, which differ in time shift by a certain amount. The variance of the ETP measurement result is N times smaller than the variance obtained using a single receiving hydrophone. However, the fundamental drawback of the method—the need to use a calculation model, which is selected based on indirect considerations—remains.An unresolved problem in creating a calculation model for the ESO and ESTO methods is that the currently used models are based on the radiation characteristics of hull structures and do not take into account the contribution of hydrodynamic sources, which leads to an underestimation of the processing results.

[0005] A known method for recording the pass-through characteristic of a marine object is adopted as a prototype (patent RU 2774731 "Method for recording the pass-through characteristic of a marine object", IPC G01S15 / 04, published on June 22, 2022). The essence of the method consists of first recording a "reference" amplitude-frequency response (AFR) of the water space noise field in receiving devices. This is then filtered, subjected to analog-to-digital conversion and median filtering in the primary signal processing unit, and then used to determine the pair of receiving devices in the cross-correlation function calculation and decision-making unit of the secondary signal processing unit. The "reference" AFR is then fed to the corresponding inputs of the adaptive filter of the secondary signal processing unit, where a "normalized" AFR of the noise field of the protected water space is generated.When a marine object appears in the protected water area, a "working" frequency response of the water area is generated in the area of ​​the receiving devices, which is fed through the previously selected first receiving channel to the first input of the cross-correlation function calculation and decision-making unit and the first input of the adaptive filter of the secondary signal processing unit. When the amplitude of the "working" frequency response of the water area exceeds the generated threshold of the "normalized" frequency response, the frequency response of the marine object is recorded. The method for recording the pass-through characteristic of a marine object eliminates the disadvantages of the ESW and ESTO methods, namely, low noise immunity when used under conditions of non-stationary interference within the time of registration of the passage of the marine object. In addition, the method eliminates the disadvantages of the method used in the "Method for registering a low-noise marine object using median filtering" (patent RU 2572052, IPC G01S15 / 04, published on 14.04.2017.), since the use of median filtering allows the elimination of impulse interference, but does not allow the filtering of the incoherent component of the interference.

[0006] The disadvantage of the method for recording the pass-through characteristic of a marine object is that the parameters of the object's movement trajectory are not determined to enable focusing and phasing of the antenna on the object under study in order to increase the signal-to-noise ratio, and the acoustic characteristics of the object are not taken into account to isolate the contribution of the hydrodynamic noise sources of interest to the overall noise field of the object.

[0007] The problem to be solved by the present invention is to develop a measurement method that allows for expanding the possibilities of analyzing acoustic characteristics and designing marine objects with given acoustic characteristics.

[0008] The technical result is achieved due to the fact that the developed method for measuring the acoustic characteristics of a physical model during movement, as well as the prototype method, consists of the movement of the test object near the measuring devices and the accumulation of experimental data.What is new is that they accumulate experimental data on the primary and secondary acoustic fields, determine the frequency dependencies of the levels and direction of acoustic radiation, for which purpose they repeatedly repeat the measurement trajectories of a self-propelled model on a testing ground near or around the measuring devices installed in a line, form a model of the acoustic field and acoustic characteristics of the offshore object using the created digital acoustic twin and a physical scale model of the object, perform validation of the digital acoustic twin on a physical scale model during the testing ground acoustic measurements, isolate the object's field from noise using the method of coordinated energy processing of measurement data with a model pass-through characteristic and incoherent summation of signals from all measuring devices during the formation of a model of the pass-through characteristic based on the calculated data of the digital acoustic twin of the object.

[0009] In a particular case of implementation, a self-propelled physical scale model of a marine object is equipped with a high-precision software and hardware navigation system that ensures stable repeatability of the trajectory of the physical scale model of the object.

[0010] In another particular case, a self-propelled physical scale model of an object is programmed to move along a closed circular trajectory near or around vertically installed measuring devices, which are a hydroacoustic measuring antenna with coherent signal processing.

[0011] In the third particular case, the current bearing of a self-propelled physical scale model is estimated by processing the signal from a vertical hydroacoustic measuring antenna using the MUSIC method to effectively isolate the useful signal from reverberation and interference noise.

[0012] In the fourth particular case, in the closed-circuit trajectory mode, additional control of the distance from the hydroacoustic measuring antenna to the self-propelled physical scale model and course correction are carried out using an underwater sound communication system.

[0013] The developed method accumulates data to increase the signal-to-noise ratio by moving the object along a closed circular trajectory (circulation) around measuring devices installed in a line (a hydroacoustic vertical antenna). This type of data accumulation allows for obtaining time-domain realizations of the acoustic signal under stationary conditions, eliminating the Doppler effect when high-resolution spectral analysis is required, and selecting the required accumulation time (number of circulations) depending on the signal-to-noise ratio in a given water area. To generate a computational model of the acoustic field and acoustic characteristics of the offshore object, a digital twin and a physical scale model of the object are created. Validation of the digital twin is performed on the physical scale model during field acoustic measurements in accordance with the proposed measurement method.

[0014] The invention is explained by the following figures.

[0015] Figure 1 shows the module variants, the physical carrier model, and the physical model with the module installed.

[0016] Fig. 2 shows a diagram of the running measurements of the acoustic field of the physical model.

[0017] Accelerometers are installed on a physical scale model with a navigation and motion control system. These accelerometers are needed to identify the relationship between structural resonances and the characteristics of the recorded underwater noise generated by turbulent flow around the moving physical model and the operation of its propulsion system. Based on the obtained information, the contribution of the propulsion system to the overall acoustic field is determined, which serves as the basis for comparison with calculated data from the digital twin. The software and hardware navigation system of the physical scale model of the object ensures the stability and repeatability of the trajectories of the motion measurements.

[0018] The proposed measurement method can be implemented for any offshore facility, provided the relevant amendments are made to the Noise Monitoring and Standardization Guidelines. The advantage of the repeated object circulation measurement method is that external acoustic field measurements are made in the offshore facility's far zone, which meets the requirements for determining the facility's acoustic signature.

[0019] To evaluate the trajectory characteristics of a model or real-life marine object, the MUSIC method—a high-resolution sound source search algorithm for high-noise environments—is used. This method enables effective beam separation in shallow waters with high interference and reverberation noise. To maximize signal isolation, a vertical receiving antenna and tracking focusing are used, or antenna element phasing is used for objects located in the far zone.

[0020] To measure the secondary field characteristics, a sound source is installed at some distance from the center of circulation to locate a marine object. The reflected signal is isolated either using pulsed location or by using the Doppler shift with continuous illumination of the object.

[0021] Thus, the proposed measurement method has the following features:

[0022] - multiple repetition of measuring trajectories by a self-propelled model in the form of circulations on a testing ground around (near) the measuring antenna;

[0023] - using the results of measurements on a large-scale physical self-propelled model to validate the calculated acoustic characteristics of the digital twin.

[0024] The results of calculations on the digital twin are subsequently used to form a signal model and implement standard methods for monitoring and standardizing the noise of offshore facilities using the ESO method, or are directly used for the acoustic design of offshore facilities.

[0025] The procedure for implementing the proposed method, for example, for the acoustic design of offshore facilities, is as follows. A geometrically similar scale physical model of the offshore facility (physical model) and the vibroactive component being studied, such as a propulsion system, are created. The physical model is equipped with software control systems: course maintenance in surface and submerged positions, maintaining a set depth, and trim and roll control. An inertial navigation system (INS) is used to control the acceleration of the model and its angular velocity. For comparative measurements, the physical model allows for the installation of modules of different designs: with a classic propeller, with a waterjet propulsor (Fig. 1), or with various propeller variants. A digital twin of the physical model is simultaneously created.As a result of the digital twin study, an array of accelerometer attachment points is generated. These are necessary for identifying the relationships between the structural resonances of the test object and the characteristics of the recorded underwater noise generated by turbulent flow around the hull and during operation of its propulsion system. Flow noise around hull irregularities is calculated. The next step involves running measurements of the model's acoustic field, including in circulation mode and using a vertically positioned hydroacoustic antenna (Fig. 2). The antenna is used to generate a directivity pattern and subsequently focus or phase it on the object to improve the signal-to-noise ratio, allowing for tracking the object's movement within the measurement range. The current bearing to the physical model is estimated using the MUSIC method.During the physical model's circulation, the inertial navigation system's readings are adjusted using a underwater sound communication system (USCS), which is capable of calculating the distance from the measuring antenna to the physical model and exchanging data between the physical model and external measuring equipment. At the measurement site for distance calculation, the USCS transceiver and its computing system are installed in close proximity to the hydroacoustic antenna axis, while the corresponding part of the USCS transceiver is installed onboard the physical model. During circulation, the USCS system calculates the distance from the antenna to the physical model (circulation radius) and subsequently makes adjustments to the data in the physical model's software control system. After completing all stages of this method, the obtained data is processed and interpreted to validate the digital twin.The use of a digital twin for acoustic design of advanced offshore projects goes beyond the measurement method.

[0026] Thus, the method allows for measurements to be carried out with high accuracy, and the data accumulation time within one measurement is limited solely by the capacity of the batteries of the physical model and the disk space of the recording equipment.

Claims

1. A method for measuring the acoustic characteristics of a marine object with a propeller, which consists of moving the test object near measuring devices and accumulating experimental data, characterized in that the experimental data of the primary and secondary acoustic fields are accumulated, the frequency dependences of the levels and direction of acoustic radiation are determined, for which purpose the measuring trajectories are repeatedly repeated by a self-propelled model on a testing ground near or around measuring devices installed in a line, a model of the acoustic field and acoustic characteristics of the marine object is formed using the created digital acoustic twin and a physical scale model of the object, validation of the digital acoustic twin is performed on the physical scale model during the testing ground acoustic measurements,the object's field is isolated from noise using the method of coordinated energy processing of measurement data with a model pass-through characteristic and incoherent summation of signals from all measuring devices when forming a model of the pass-through characteristic based on the calculated data of the digital acoustic twin of the object.

2. The method according to paragraph 1, characterized in that the self-propelled physical scale model of the offshore object is equipped with a high-precision software and hardware navigation complex that ensures stable repeatability of the trajectory of movement of the physical scale model of the object.

3. The method according to paragraph 1 or 2, characterized in that the self-propelled physical scale model of the object is programmed to move along a closed circular trajectory near or around vertically installed measuring devices, which are a hydroacoustic measuring antenna with coherent signal processing.

4. The method according to paragraph 1, or 2, or 3, characterized in that the current bearing of the self-propelled physical scale model is estimated, for this purpose the signal from the vertical hydroacoustic measuring antenna is processed, using the MUSIC method for the effective extraction of the useful signal from reverberation and interference noise.

5. The method according to paragraph 1, or 2, or 3, characterized in that in the mode of movement along a closed circular trajectory, additional control of the distance from the hydroacoustic measuring antenna to the self-propelled physical scale model and course correction are carried out using an underwater sound communication system.

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