CN118130039A - Urban landscape dam under-water drainage running water noise exploration method - Google Patents
Urban landscape dam under-water drainage running water noise exploration method Download PDFInfo
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Abstract
The invention relates to the technical field of running water noise, and provides a method for exploring running water noise of water discharged from an urban landscape dam, which comprises the following steps: 1. establishing a physical model of the dam; 2. setting a detection point at the downstream of the dam physical model, and measuring noise sound pressure, underwater sound pressure, water pressure and three-dimensional flow velocity at the detection point; 3. calculating to obtain noise sound pressure level, underwater sound pressure level, water pressure time domain data, pulse pressure, root mean square of pulse pressure and turbulence energy; 4. and establishing a spectrogram and analyzing the internal relation. The invention can analyze noise source better.
Description
Technical Field
The invention relates to the technical field of running water noise, in particular to a method for exploring running water noise of water leakage under an urban landscape dam.
Background
The water flow passes through water diversion or drainage facilities in hydraulic engineering, such as overflow weirs, sluice gates, diversion tunnels, flood discharge holes and the like, and due to the complex flow channel boundaries of the water flow, the water flow is often caused to have high-speed turbulence and complex hydrodynamic characteristics, so that high decibel water flow noise is caused. The running of water conservancy facilities such as low weirs and gate dams in urban landscape water bodies can generate water flow noise to a certain extent, and some water flow noise can even exceed the noise standard of living environment, pollute the environment and are not beneficial to the physical and mental health of surrounding residents.
At present, water conservancy facilities mainly produce three kinds of water noise because of rivers effect, mainly do: turbulence noise generated by turbulence of the water flow, impact noise generated by interaction between the water flow and a building, and cavitation noise generated by vibration and rupture of bubbles in the water flow. Cavitation noise is the simultaneous generation of impulse noise when the water flow is at a low or negative pressure and the pressure drops to the saturation pressure of the water, resulting in rapid vaporization of the water flow, followed by collapse of the bubbles produced by the vaporization. At present, the research on cavitation noise is mainly focused on the aspects of propellers and the like. When the water flow speed is more than 12.7m/s, cavitation bubbles and cavitation noise are generated; when the water flow velocity is less than 12.7m/s, the generation of cavitation bubbles is not observed. Because the water velocity of the urban water conservancy landscape facility is smaller, cavitation noise can not be generated, and the water noise mainly comprises: turbulent water noise generated by the turbulence of the water flow and impact water noise generated by the interaction of the water flow and the building.
However, the state of the art is as follows:
1. the current discussion of dam water noise scientific research is few, mainly the actual research of engineering on noise reduction measures, and the research on the content of the generation mechanism of the dam water noise of the urban landscape is less;
2. The research on noise generated by the dam water drainage at home and abroad is still in the test stage, and mainly aims at the physical model test of different weir type researches on the influence of noise and no actual engineering equal proportion setting;
3. related field researches focus on analyzing factors influencing the generation of water noise of an urban landscape dam and qualitative relations between the factors, and analytical formulas for quantitatively representing the water noise are rarely seen;
4. At present, no test for directly measuring influence of turbulence on noise exists in hydraulic engineering.
Therefore, there is a need for a method of exploring the noise of the underdrain running water of an urban landscape dam to solve the above problems.
Disclosure of Invention
The invention provides a method for exploring the water drainage and running noise under an urban landscape dam, which can study and discuss the correlations between the water noise and the turbulent noise of water flow and the action noise of water flow and a building, and analyze and find a main noise source.
The invention relates to a method for exploring the noise of water flowing in the water discharged under an urban landscape dam, which comprises the following steps:
1. Establishing a physical model of the dam;
2. setting a detection point at the downstream of the dam physical model, and measuring noise sound pressure, underwater sound pressure, water pressure and three-dimensional flow velocity at the detection point;
3. Calculating to obtain noise sound pressure level, underwater sound pressure level, water pressure time domain data, pulse pressure, root mean square of pulse pressure and turbulence energy;
4. and establishing a spectrogram and analyzing the internal relation.
Preferably, in the second step, the detection points are provided with a hydrophone, a microphone, a pressure sensor and a three-dimensional profile flow velocity meter.
Preferably, the hydrophone is arranged as follows:
3 hydrophone detection points are arranged at the obvious downstream water spray position, the bottom of the downstream water tank and the downstream water flow slow position, wherein the distance between the detection points and the downstream water flow slow position is V 1、V2、V3,V1、V2, the distance between the detection points and the dam model is 0.3m, V 3 is positioned at the water flow slow position, and the height of the detection points is the same as that of V 1, and the detection points are the water depth h. The method comprises the steps of obtaining time domain data of sound pressure of underwater sound signals by measuring underwater sound signals at different positions under water surface, carrying out fast Fourier transform on the underwater sound time domain data to obtain frequency domain data, and further analyzing sound pressure level changes and frequency spectrum characteristics of underwater drainage water under different working conditions.
Preferably, the microphone is provided as follows:
The microphone P 1 is arranged right above the hydrophone measuring point V 1, and the distance V 1 is 0.25m; measuring noise signals in the air at the obvious position of downstream water bloom, obtaining time domain data of air noise signal sound pressure, obtaining frequency domain data by carrying out Fourier change on the air noise time domain data, and analyzing the sound pressure level change and the frequency spectrum characteristics of the water leakage running water sound under different working conditions by combining hydrophone data.
Preferably, the pressure sensor is provided as follows:
4 pressure sensors Z 1、Z2、Z3、Z4 are arranged at the bottom of the water tank, the pressure sensor Z 5,Z1 is arranged at the downstream water inflow turbulence position and is 0.3m away from the bottom of the dam, and in order to ensure that Z 4 is positioned at the downstream water flow turbulence position, the interval between the pressure sensors is 0.8m; measuring the water pressure at different points on the downstream of the gate dam by adopting a pressure sensor, performing spectrum analysis on the obtained data to obtain signal characteristics of a pressure spectrum under each working condition, and further analyzing the relation between the water flow impact acting force and water noise generated by the impact;
preferably, the three-dimensional profile flow meter is set as follows:
The three-dimensional profile flow rate meter U 1 is arranged at the downstream water flow smooth position, is positioned right below the V 3 and is positioned at a height which is 0.6 times the water depth.
Preferably, in the third step, the noise sound pressure and the underwater sound pressure are obtained by calculating the noise sound pressure level and the underwater sound pressure level; the water pressure is measured to obtain water pressure time domain data, and the root mean square of the pulsating pressure and the pulsating pressure is obtained through calculation; the three-dimensional flow velocity is calculated to obtain turbulence energy.
Preferably, in the fourth step, specifically including:
1) The noise sound pressure and water sound pressure time domain data are analyzed through 1/3 octaves to obtain a 1/3 octave spectrogram; performing Fourier transformation after the turbulence energy and the pulsating water pressure are autocorrelation to obtain an amplitude spectrum and a self-power spectrum of the pulsating water pressure;
2) By analyzing the change trend of noise and underwater sound pressure level along with dam height, downstream water depth and upstream flow, analyzing 1/3 octave spectrograms of noise and underwater sound, and finding out noise influence factors, frequency characteristics and internal relation of the noise in the air and the underwater sound;
3) By analyzing the variation trend of the acoustic sound pressure level, the root mean square of the pulse pressure and the turbulent energy along with the dam height, the downstream water depth and the upstream flow, analyzing the 1/3 octave spectrogram, the pulse pressure and the turbulent energy spectrogram, and finding out the influence factors, the frequency characteristics and the internal relation of the acoustic noise and the water pressure and the turbulent flow in the water;
4) The internal relation between the noise and the water pressure and the internal relation between the water sound and the water pressure and the internal relation between the noise and the water pressure and the internal relation between the water sound and the turbulence are analyzed.
Preferably, the time domain data of the sound pressure of the underwater sound signal is obtained by measuring the underwater sound signals at different positions under the water surface, the time domain data of the underwater sound is subjected to fast Fourier change to obtain the frequency domain data, and the sound pressure level is utilizedWherein p is a sound pressure value of a certain point, p 0 is a reference sound pressure, and the sound pressure is converted into a sound pressure level by a formula, so that the change of the sound pressure level and the frequency spectrum characteristics of the water leakage running sound under different working conditions are analyzed;
measuring noise signals in the air at the obvious position of downstream water bloom, obtaining time domain data of air noise signal sound pressure, obtaining frequency domain data by carrying out Fourier transform on the air noise time domain data, and analyzing sound pressure level change and frequency spectrum characteristics of water drainage running sound under different working conditions by combining hydrophone data;
The digital pressure sensor is adopted to measure the water pressure at different points downstream of the gate dam, so as to obtain time domain data of the water pressure, and the time domain data is calculated by a formula Time-sharing pressure/>, to obtain water pressureP i is water pressure time domain data, and N is sampling statistics;
By the formula Calculating pulsation data P' of the water pressure, namely the pulsation water pressure; performing autocorrelation on the pulsating water pressure, performing fast Fourier transform FFT on the pulsating water pressure after the autocorrelation to obtain frequency domain data of the pulsating water pressure, and drawing a spectrogram; the signal characteristics of the pressure frequency spectrum under each working condition are obtained, and then the relation between the water flow impact acting force and the water noise generated by the impact is analyzed;
the root mean square value P RMS of the pulse pressure is calculated by the formula Calculate the mean square value/>, of the water pressureThen root mean square of the pulsating pressure is obtained by root mean square
The spectrum analysis, namely the amplitude spectrum and the self-power spectrum of the water pressure can be obtained after FFT, the dominant frequency range with concentrated energy and the main frequency with most concentrated energy can be obtained through analysis, and the characteristic and the relation of the water noise spectrum can be discussed in frequency through analysis and comparison; the root mean square of the pulsating pressure represents the amplitude of the pulsating pressure, and the change trend and the relation of the pulsating pressure and the noise sound pressure level can be discussed by researching the change rule of the pulsating pressure and the noise sound pressure level;
Measuring the flow velocity of each point in the flow field by using a three-dimensional profile flow velocity meter, converting the three-dimensional flow velocity into turbulent energy by using a formula k=0.5 (u r'ur'+uθ'uθ'+uz'uz'), performing spectrum analysis by using the data of the turbulent energy, drawing a spectrogram to analyze the energy change rule generated by the turbulent fluctuation of the water flow under each working condition, and further analyzing the turbulent noise generated by the turbulent fluctuation of the water flow;
k is turbulence energy, which characterizes the energy of turbulence; u r'、uθ'、uz' represents the pulsating flow rate in the three directions of transverse, longitudinal and vertical at a certain point in the water, the pulsating flow rate is calculated to be the same as the pulsating pressure, namely the pulsating flow rate is the difference between the time domain flow rate and the time average flow rate.
The invention discusses the correlation between the water noise and the turbulent noise of the water flow and the action noise of the water flow and the building through the change conditions of the noise, the underwater sound pressure level, the pulsation pressure and the turbulent energy under each working condition. And then, carrying out spectrum analysis by using the data measured under different working conditions through a noise spectrum, a pressure spectrum and a pulsation value of the water flow speed, and analyzing the main source of noise according to the change trend of the spectrum under each working condition.
Noise reduction measures can be implemented aiming at main noise sources by analyzing the noise sources of the urban landscape dams; the method provides theoretical support and technical measures for noise reduction design of the urban water conservancy and landscape facilities, has instructive significance for noise reduction of the urban water conservancy and landscape facilities, and is specifically as follows:
1) Providing a quiet environment: providing a relatively quiet living and working environment for the residents. The urban landscape dam is beneficial to improving the urban landscape dam, can effectively reduce the transmission of noise, is the life quality of residents, and reduces the influence of the noise on physical and mental health;
2) Protecting the ecological system: noise also has adverse effects on the natural ecosystem, such as interference with birds, insects, and other wild animals. The noise reduction measures of the urban landscape dam can reduce the interference and protect the balance and diversity of an ecological system;
3) Improve community interaction: noise pollution can interfere with communications and interactions between community residents. Noise reduction can create a more friendly and harmonious community environment, and social activities and community cohesive force of residents are promoted;
4) Improving the urban image: the noise reduction measures of the urban landscape dam can improve the environment quality and living experience of the city and improve the image and the attraction of the city. This helps to attract investment, promote economic development, and increase urban travel appeal.
Drawings
FIG. 1 is a flow chart of a method for exploring the noise of water flowing in the water under an urban landscape dam in an embodiment;
FIG. 2 is a schematic view of a longitudinal central axis of a water tank in a cross section in an embodiment;
FIG. 3 is a schematic diagram of a station arrangement in an embodiment.
Detailed Description
For a further understanding of the present invention, the present invention will be described in detail with reference to the drawings and examples. It is to be understood that the examples are illustrative of the present invention and are not intended to be limiting.
Examples
As shown in fig. 1, the embodiment provides a method for exploring the noise of the water flowing in the water discharged from an urban landscape dam, which comprises the following steps:
1. Establishing a physical model of the dam;
The method is realized by setting three variables of upstream water flow speed, dam height and downstream water depth, changing water flow state and then changing water flow and noise characteristics, and the specific parameters are as follows: the upstream flow takes Q 1＝15l/s、Q2＝30l/s、Q3＝45l/s、Q4 =60 l/s and Q 5 =75 l/s respectively; taking h 1＝0cm、h2＝10cm、h3＝20cm、h4＝30cm、h5 =40 cm and h 6 =50 cm from the downstream water depth respectively; the height of the weirs was H 1＝50cm、H2＝60cm、H3＝70cm、H4 =80 cm and H 5 =80 cm, respectively. To avoid noise from the interaction of the upstream water flow with the dam, three ways of fixing the dam are adopted: 1. the expansion screw is fixed; 2. the self weight is increased by using the bricks, so that the vibration of the dam model caused by overlarge upstream water flow is avoided; 3. supported by a stay bar.
The water tank of the model is 24m long, the non-ridge wide top weir model is arranged at a position 7m away from an upstream water outlet, the heights of the non-ridge wide top weir model are 50cm, 60cm, 70cm, 80cm and 90cm, the widths of the non-ridge wide top weir model are 0.5m, and gaps between the non-ridge wide top weir and the side wall of the water tank are bonded by using glass cement. The noise measuring points are arranged on the section of the longitudinal central axis of the water tank.
2. Setting a detection point at the downstream of the dam physical model, and setting a corresponding hydrophone, a microphone, a pressure sensor and a three-dimensional profile flow velocity meter at the detection point; measuring noise sound pressure, underwater sound pressure, water pressure and three-dimensional flow velocity;
Hydrophones are output instruments that measure the acoustic pressure changes of underwater acoustic signals and produce a voltage proportional to the acoustic pressure. The experiment adopts RHS-30 spherical standard hydrophone, the spherical head sensitive element is piezoelectric ceramics, also called piezoelectric hydrophone, which is a voltage output instrument for detecting underwater acoustic signal change and generating voltage proportional to sound pressure. The arrangement is as follows:
as shown in fig. 2 and 3, 3 hydrophone detection points are arranged at the obvious downstream water spray, the bottom of the downstream water tank and the downstream water level slow position, wherein the distance between V 1、V2、V3,V1、V2 and the dam model is 0.3m, V 3 is positioned at the water level slow position, and the height of the hydrophone detection points is equal to the height of V 1 and is the water depth h. The method comprises the steps of obtaining time domain data of sound pressure of underwater sound signals by measuring underwater sound signals at different positions under water surface, carrying out fast Fourier transform on the underwater sound time domain data to obtain frequency domain data, and further analyzing sound pressure level changes and frequency spectrum characteristics of underwater drainage water under different working conditions.
Microphones are transducers that convert acoustic signals into electrical signals. The nickel or the alloy diaphragm is adopted and is subjected to special stability treatment, and the method has the advantages of wide frequency range, good frequency response, wide dynamic range, good dynamic characteristics, good long-time stability and the like. In order to better combine hydrophone data to perform corresponding analysis on water noise, the following microphone settings are performed:
The microphone P 1 is arranged right above the hydrophone measuring point V 1, and the distance V 1 is 0.25m; measuring noise signals in the air at the obvious position of downstream water bloom, obtaining time domain data of air noise signal sound pressure, obtaining frequency domain data by carrying out Fourier change on the air noise time domain data, and analyzing the sound pressure level change and the frequency spectrum characteristics of the water leakage running water sound under different working conditions by combining hydrophone data.
Pressure sensors are sensors for measuring the pressure of liquids and gases. Similar to other sensors, pressure sensors operate to convert pressure into an electrical signal for output. The arrangement is as follows:
4 pressure sensors Z 1、Z2、Z3、Z4 are arranged at the bottom of the water tank, the pressure sensor Z 5,Z1 is arranged at the downstream water inflow turbulence position and is 0.3m away from the bottom of the dam, and in order to ensure that Z 4 is positioned at the downstream water flow turbulence position, the distance between the pressure sensors is 0.8m, as shown in figure 1; measuring the water pressure at different points on the downstream of the gate dam by using CY200 series intelligent digital pressure sensors, performing spectrum analysis on the obtained data to obtain signal characteristics of a pressure spectrum under each working condition, and further analyzing the relation between the water flow impact acting force and water noise generated by the impact;
The three-dimensional profile flow velocity meter is used for measuring the flow velocity of each point in the flow field. And measuring the flow velocity of each point in the flow field by using a three-dimensional profile flow velocity meter, and correcting a water noise generation analysis formula established by the physical model. In order to ensure the accuracy of the data, the following settings were made:
The three-dimensional profile flow rate meter U 1 is arranged at the downstream water flow smooth position, is positioned right below the V 3 and is positioned at a height which is 0.6 times the water depth.
The upstream water inlet can adjust the upstream water flow velocity, and the downstream water baffle can be provided with different downstream water depths. Water noise data at different upstream flow rates, downstream water depths, and different dam heights can be measured.
3. Calculating to obtain noise sound pressure level, underwater sound pressure level, water pressure time domain data, pulse pressure, root mean square of pulse pressure and turbulence energy;
the sound pressure of the noise and the sound pressure of the water are obtained through calculation; the water pressure is measured to obtain water pressure time domain data, and the root mean square of the pulsating pressure and the pulsating pressure is obtained through calculation; the three-dimensional flow velocity is calculated to obtain turbulent energy;
4. Establishing a spectrogram and analyzing an internal relation;
The method specifically comprises the following steps:
1) The noise sound pressure and water sound pressure time domain data are analyzed through 1/3 octaves to obtain a 1/3 octave spectrogram; performing Fourier transformation after the turbulence energy and the pulsating water pressure are autocorrelation to obtain an amplitude spectrum and a self-power spectrum of the pulsating water pressure;
2) By analyzing the change trend of noise and underwater sound pressure level along with dam height, downstream water depth and upstream flow, analyzing 1/3 octave spectrograms of noise and underwater sound, and finding out noise influence factors, frequency characteristics and internal relation of the noise in the air and the underwater sound;
3) By analyzing the variation trend of the acoustic sound pressure level, the root mean square of the pulse pressure and the turbulent energy along with the dam height, the downstream water depth and the upstream flow, analyzing the 1/3 octave spectrogram, the pulse pressure and the turbulent energy spectrogram, and finding out the influence factors, the frequency characteristics and the internal relation of the acoustic noise and the water pressure and the turbulent flow in the water;
4) The internal relation between the noise and the water pressure and the internal relation between the water sound and the water pressure and the internal relation between the noise and the water pressure and the internal relation between the water sound and the turbulence are analyzed.
Obtaining time domain data of sound pressure of underwater sound signals by measuring the underwater sound signals at different positions under the water surface, performing fast Fourier change on the underwater sound time domain data to obtain frequency domain data, and utilizing sound pressure levelWherein p is a sound pressure value of a certain point, p 0 is a reference sound pressure, and the sound pressure is converted into a sound pressure level by a formula, so that the change of the sound pressure level and the frequency spectrum characteristics of the water leakage running sound under different working conditions are analyzed;
measuring noise signals in the air at the obvious position of downstream water bloom, obtaining time domain data of air noise signal sound pressure, obtaining frequency domain data by carrying out Fourier transform on the air noise time domain data, and analyzing sound pressure level change and frequency spectrum characteristics of water drainage running sound under different working conditions by combining hydrophone data;
The digital pressure sensor is adopted to measure the water pressure at different points downstream of the gate dam, so as to obtain time domain data (instantaneous data) of the water pressure, and the time domain data (instantaneous data) of the water pressure is calculated by the formula Time-sharing pressure/>, to obtain water pressureP i is water pressure time domain data, and N is sampling statistics number (namely, the sampling number corresponding to the sampling frequency). Because the water pressure time domain data can be interpreted as a superposition of time-averaged data and pulsatile data, the water pressure time domain data can be calculated by the formula/>The pulsating data (P') of the water pressure, i.e., the pulsating water pressure, is calculated. And then carrying out autocorrelation on the pulsating water pressure, carrying out Fast Fourier Transform (FFT) on the pulsating water pressure after the autocorrelation to obtain frequency domain data of the pulsating water pressure, and drawing a spectrogram (spectrum analysis). And obtaining signal characteristics of the pressure frequency spectrum under each working condition, and further analyzing the relation between the water flow impact acting force and the water noise generated by the impact. The root mean square value (P RMS) of the pulsating pressure is calculated by the formula/>Calculate the mean square value/>, of the water pressureRoot mean square of the pulsating pressure is obtained by root mean square (i.e./>)). The spectrum analysis, namely the amplitude spectrum and the self-power spectrum of the water pressure can be obtained after FFT, the dominant frequency range with more concentrated energy and the main frequency with most concentrated energy can be obtained by analysis, and the characteristic and the relation of the two in frequency can be discussed by analyzing and comparing the water noise spectrum. The root mean square of the pulsating pressure represents the amplitude of the pulsating pressure, and the change trend and the connection of the pulsating pressure and the noise sound pressure level can be discussed by researching the change rule of the pulsating pressure and the noise sound pressure level.
The flow velocity of each point in the flow field is measured by a three-dimensional profile flow velocity meter, the three-dimensional flow velocity is converted into turbulent energy by using a formula k=0.5 (u r'ur'+uθ'uθ'+uz'uz'), the data of the turbulent energy is used for spectral analysis, the energy change rule generated by the turbulent fluctuation of the water flow under each working condition is drawn by the spectral analysis, and then the turbulent noise generated by the turbulent fluctuation of the water flow is analyzed.
K is turbulence energy, which characterizes the energy of turbulence; u r'、uθ'、uz' represents the pulsating flow rate in the three directions of transverse, longitudinal and vertical at a certain point in the water, the pulsating flow rate is calculated to be the same as the pulsating pressure, namely the pulsating flow rate is the difference between the time domain flow rate and the time average flow rate.
The correlation between the water noise and the turbulent noise of the water flow and the action noise of the water flow and the building is discussed through the change conditions of the noise, the underwater sound pressure level, the pulsation pressure and the turbulent energy under each working condition. And then, carrying out spectrum analysis by using the data measured under different working conditions through a noise spectrum, a pressure spectrum and a pulsation value of the water flow speed, and analyzing the main source of noise according to the change trend of the spectrum under each working condition.
The invention and its embodiments have been described above by way of illustration and not limitation, and the invention is illustrated in the accompanying drawings and described in the drawings in which the actual structure is not limited thereto. Therefore, if one of ordinary skill in the art is informed by this disclosure, the structural mode and the embodiments similar to the technical scheme are not creatively designed without departing from the gist of the present invention.
Claims (9)
1. A method for exploring the noise of the water leakage and running under an urban landscape dam is characterized in that: the method comprises the following steps:
1. Establishing a physical model of the dam;
2. setting a detection point at the downstream of the dam physical model, and measuring noise sound pressure, underwater sound pressure, water pressure and three-dimensional flow velocity at the detection point;
3. Calculating to obtain noise sound pressure level, underwater sound pressure level, water pressure time domain data, pulse pressure, root mean square of pulse pressure and turbulence energy;
4. and establishing a spectrogram and analyzing the internal relation.
2. The method for exploring the noise of the underdrain running water of the urban landscape dam according to claim 1, which is characterized by comprising the following steps: in the second step, the detection points are provided with a hydrophone, a microphone, a pressure sensor and a three-dimensional profile flow velocity meter.
3. The method for exploring the noise of the underdrain running water of the urban landscape dam according to claim 2, which is characterized in that: the hydrophone is arranged as follows:
3 hydrophone detection points are arranged at the obvious downstream water spray position, the bottom of the downstream water tank and the downstream water flow slow position, wherein the distance between the detection points and the downstream water flow slow position is V 1、V2、V3,V1、V2, the distance between the detection points and the dam model is 0.3m, V 3 is positioned at the water flow slow position, and the height of the detection points is the same as that of V 1, and the detection points are the water depth h. The method comprises the steps of obtaining time domain data of sound pressure of underwater sound signals by measuring underwater sound signals at different positions under water surface, carrying out fast Fourier transform on the underwater sound time domain data to obtain frequency domain data, and further analyzing sound pressure level changes and frequency spectrum characteristics of underwater drainage water under different working conditions.
4. The method for exploring the noise of the underdrain running water of the urban landscape dam according to claim 3, wherein the method comprises the following steps: the microphone is set as follows:
The microphone P 1 is arranged right above the hydrophone measuring point V 1, and the distance V 1 is 0.25m; measuring noise signals in the air at the obvious position of downstream water bloom, obtaining time domain data of air noise signal sound pressure, obtaining frequency domain data by carrying out Fourier change on the air noise time domain data, and analyzing the sound pressure level change and the frequency spectrum characteristics of the water leakage running water sound under different working conditions by combining hydrophone data.
5. The method for exploring the noise of the underdrain running water of the urban landscape dam according to claim 4, wherein the method comprises the following steps: the pressure sensor is set as follows:
4 pressure sensors Z 1、Z2、Z3、Z4 are arranged at the bottom of the water tank, the pressure sensor Z 5,Z1 is arranged at the downstream water inflow turbulence position and is 0.3m away from the bottom of the dam, and in order to ensure that Z 4 is positioned at the downstream water flow turbulence position, the interval between the pressure sensors is 0.8m; the pressure sensor is used for measuring the water pressure at different points on the downstream of the gate dam, the obtained data are subjected to spectrum analysis, the signal characteristics of the pressure spectrum under each working condition are obtained, and then the relation between the water flow impact acting force and the water noise generated by the impact is analyzed.
6. The method for exploring the noise of the underdrain running water of the urban landscape dam according to claim 5, wherein the method comprises the following steps: the three-dimensional profile flow rate meter is set as follows:
The three-dimensional profile flow rate meter U 1 is arranged at the downstream water flow smooth position, is positioned right below the V 3 and is positioned at a height which is 0.6 times the water depth.
7. The method for exploring the noise of the underdrain running water of the urban landscape dam according to claim 6, wherein the method comprises the following steps: step three, obtaining a noise sound pressure level and a water sound pressure level through calculation of the noise sound pressure and the water sound pressure; the water pressure is measured to obtain water pressure time domain data, and the root mean square of the pulsating pressure and the pulsating pressure is obtained through calculation; the three-dimensional flow velocity is calculated to obtain turbulence energy.
8. The method for exploring the noise of the underdrain running water of the urban landscape dam according to claim 7, wherein the method comprises the following steps: in the fourth step, specifically include:
1) The noise sound pressure and water sound pressure time domain data are analyzed through 1/3 octaves to obtain a 1/3 octave spectrogram; performing Fourier transformation after the turbulence energy and the pulsating water pressure are autocorrelation to obtain an amplitude spectrum and a self-power spectrum of the pulsating water pressure;
2) By analyzing the change trend of noise and underwater sound pressure level along with dam height, downstream water depth and upstream flow, analyzing 1/3 octave spectrograms of noise and underwater sound, and finding out noise influence factors, frequency characteristics and internal relation of the noise in the air and the underwater sound;
3) By analyzing the variation trend of the acoustic sound pressure level, the root mean square of the pulse pressure and the turbulent energy along with the dam height, the downstream water depth and the upstream flow, analyzing the 1/3 octave spectrogram, the pulse pressure and the turbulent energy spectrogram, and finding out the influence factors, the frequency characteristics and the internal relation of the acoustic noise and the water pressure and the turbulent flow in the water;
4) The internal relation between the noise and the water pressure and the internal relation between the water sound and the water pressure and the internal relation between the noise and the water pressure and the internal relation between the water sound and the turbulence are analyzed.
9. The method for exploring the noise of the underdrain running water of the urban landscape dam according to claim 8, wherein the method comprises the following steps: obtaining time domain data of sound pressure of underwater sound signals by measuring the underwater sound signals at different positions under the water surface, performing fast Fourier change on the underwater sound time domain data to obtain frequency domain data, and utilizing sound pressure levelWherein p is a sound pressure value of a certain point, p 0 is a reference sound pressure, and the sound pressure is converted into a sound pressure level by a formula, so that the change of the sound pressure level and the frequency spectrum characteristics of the water leakage running sound under different working conditions are analyzed;
measuring noise signals in the air at the obvious position of downstream water bloom, obtaining time domain data of air noise signal sound pressure, obtaining frequency domain data by carrying out Fourier transform on the air noise time domain data, and analyzing sound pressure level change and frequency spectrum characteristics of water drainage running sound under different working conditions by combining hydrophone data;
The digital pressure sensor is adopted to measure the water pressure at different points downstream of the gate dam, so as to obtain time domain data of the water pressure, and the time domain data is calculated by a formula Time-sharing pressure/>, to obtain water pressureP i is water pressure time domain data, and N is sampling statistics;
By the formula Calculating pulsation data P' of the water pressure, namely the pulsation water pressure; performing autocorrelation on the pulsating water pressure, performing fast Fourier transform FFT on the pulsating water pressure after the autocorrelation to obtain frequency domain data of the pulsating water pressure, and drawing a spectrogram; the signal characteristics of the pressure frequency spectrum under each working condition are obtained, and then the relation between the water flow impact acting force and the water noise generated by the impact is analyzed;
the root mean square value P RMS of the pulse pressure is calculated by the formula Calculate the mean square value/>, of the water pressureThen root mean square of the pulsating pressure is obtained by root mean square, namely/>
The spectrum analysis, namely the amplitude spectrum and the self-power spectrum of the water pressure can be obtained after FFT, the dominant frequency range with concentrated energy and the main frequency with most concentrated energy can be obtained through analysis, and the characteristic and the relation of the water noise spectrum can be discussed in frequency through analysis and comparison; the root mean square of the pulsating pressure represents the amplitude of the pulsating pressure, and the change trend and the relation of the pulsating pressure and the noise sound pressure level can be discussed by researching the change rule of the pulsating pressure and the noise sound pressure level;
Measuring the flow velocity of each point in the flow field by using a three-dimensional profile flow velocity meter, converting the three-dimensional flow velocity into turbulent energy by using a formula k=0.5 (u r'ur'+uθ'uθ'+uz'uz'), performing spectrum analysis by using the data of the turbulent energy, drawing a spectrogram to analyze the energy change rule generated by the turbulent fluctuation of the water flow under each working condition, and further analyzing the turbulent noise generated by the turbulent fluctuation of the water flow;
k is turbulence energy, which characterizes the energy of turbulence; u r'、uθ'、uz' represents the pulsating flow rate in the three directions of transverse, longitudinal and vertical at a certain point in the water, the pulsating flow rate is calculated to be the same as the pulsating pressure, namely the pulsating flow rate is the difference between the time domain flow rate and the time average flow rate.
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