CN108303570B - Calibration device and method for sound wave scattering area of Doppler current meter - Google Patents
Calibration device and method for sound wave scattering area of Doppler current meter Download PDFInfo
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Abstract
The invention relates to a calibration device and a calibration method for a Doppler current meter sound wave scattering area, which comprises a standard plate (3), an upper shock absorber (4), a lower shock absorber (5), a first connecting rod (61), a second connecting rod (62) and a moving mechanism, wherein the standard plate is fixedly connected with the upper shock absorber; the standard plate (3) is formed by connecting round pipes, one end of each round pipe is provided with a long cone (34), and the other end of each round pipe is provided with a short cone (31); the moving mechanism comprises a first guide rail (71), a first linear stepping motor (72), a rotary stepping motor (73), a turntable (74), a second linear stepping motor (75) and a second guide rail (76); the first connecting rod (61) is a straight rod, the second connecting rod (62) comprises an upper vertical rod (621), a horizontal rod (622) and a lower vertical rod (623), and the axis of the lower vertical rod (623) and the axis of the rotating shaft of the rotating stepping motor (73) are on the same straight line. The method can accurately calibrate the effective acoustic scattering area of the Doppler current meter.
Description
Technical Field
The invention relates to a calibration device and a calibration method, in particular to a calibration device and a calibration method for a sound wave scattering area of a Doppler current meter, and belongs to the field of acoustic measurement.
Background
Doppler current meters use the doppler effect of sound waves in a moving medium to make flow velocity measurements. The traditional Doppler current meter adopts a transducer at the front end to transmit sound waves, the sound waves are scattered by moving media such as water flow, small particles and bubbles, the scattered sound waves are received by another transducer, and the flow velocity of water is calculated according to Doppler frequency offset generated by a moving object. In the past, the speed measurement precision of the current meter is mostly calibrated in an outfield water area, the Chinese ocean industry standard HY/T102-2007 (acoustic Doppler current profiler detection method) is used as an instructive file, and the flow velocity detection specified in the standard comprises a GPS detection method and a comparison method of current measuring instruments of the same type.
Because the error of the external field test is larger, in recent years, stable water flow is formed by utilizing circulating water tanks in laboratories, and a PIV (particle image velocimeter) or LDV (laser Doppler velocimeter) technology is adopted to calibrate the flow velocity of the water flow to form a standard flow field, so that the calibration of the Doppler current meter is completed. Within the flow velocity range of 0.01 m/s-3 m/s, the uncertainty of calibration can reach: 0.1% (flow rate value) +2mm/s (see national focus research and development plan-key measurement standard and traceability technical research, approval number: 2016YFF0200900) and the uncertainty is far higher than the speed measurement accuracy of the Doppler current meter, for example: the flow measurement accuracy of the LSH10-1A hand-held ultrasonic Doppler velocimeter is 1% (flow rate value) +1 cm/s. Therefore, it is feasible to accurately calibrate the speed measurement precision of the Doppler current meter by adopting the circulating water tank and the laser speed measurement system.
However, the biggest problem in the calibration process is how to determine the effective working area of the doppler current meter, the range where the acoustic doppler effect is generated, i.e. the area of the volume reverberation.
Conventionally, the beam angles and the sound velocities of the transmitting transducer and the receiving transducer are used for calculating an effective acoustic scattering area, which is a theoretical calculation method, and the main lobe of each transducer does not necessarily coincide with the normal line through the circle center of the transducer, so that although the precise processing is carried out on the process, the intersecting range of two sound beams after being installed on a base is difficult to guarantee.
Another commonly used method for testing the intersection range of transducers is the acoustic flow imaging method, i.e. a flat plate with squares is placed in the distance of the intersection region right in front of the two transducers, the flat plate has a certain backward inclination angle, sand grains are pasted on the plate, the two transducers are simultaneously applied with the same electric power, after several seconds, a circular sand cave driven by a flow beam appears on the inclined plate, and the calibration of the intersection region is realized by utilizing the receiving and transmitting reciprocity characteristics of the transducers. However, when the doppler current meter is used, one transducer is required to transmit sound waves, one transducer is required to receive sound waves, and the transducers generate a nonlinear effect when powered on, so that the receiving and transmitting reciprocity characteristics are not satisfied any more, and therefore, the calibration of the intersection region of the transducers by the acoustic flow imaging method has certain problems.
In addition, a method of using a needle type hydrophone to calibrate an effective acoustic scattering area of the Doppler current meter is adopted, the method is limited by the sensitivity of the hydrophone, and when the calibration is completed by using the hydrophone with higher sensitivity, the effective acoustic scattering area is larger; when the calibration is completed by adopting the hydrophone with lower sensitivity, the effective acoustic scattering area is smaller; in addition, the hydrophones have certain volume and size, and when a local structure senses the pulsating pressure of sound waves, an electric signal is output, which is one of the reasons for errors in a calibration area.
In summary, the various methods for calibrating the acoustic scattering region of doppler current meters have some drawbacks. How to calibrate the effective acoustic scattering area of the Doppler current meter becomes the primary problem of measuring the speed measurement precision of the Doppler current meter.
Disclosure of Invention
Aiming at the prior art, the invention aims to provide a calibration device and a calibration method capable of accurately calibrating an effective acoustic scattering region of a Doppler current meter.
In order to solve the technical problem, the calibration device of the Doppler current meter sound wave scattering area comprises a standard plate 3, an upper shock absorber 4, a lower shock absorber 5, a first connecting rod 61, a second connecting rod 62 and a moving mechanism; the standard plate 3 is formed by mutually connecting circular tubes which are hollow inside and closed at two ends, wherein a long cone 34 is arranged at one end of each circular tube close to the Doppler current meter 2, and a short cone 31 is arranged at one end of each circular tube far away from the Doppler current meter; the moving mechanism comprises a first guide rail 71, a first linear stepping motor 72, a rotary stepping motor 73, a turntable 74, a second linear stepping motor 75 and a second guide rail 76; the first connecting rod 61 is a straight rod, the second connecting rod 62 comprises an upper vertical rod 621, a horizontal rod 622 and a lower vertical rod 623, and the axis of the lower vertical rod 623 and the axis of the rotating shaft of the rotating stepping motor 73 are on the same straight line; the upper end and the lower end of the standard plate 3 are fixedly connected with an upper shock absorber 4 and a lower shock absorber 5 through a first thin stud 32 and a second thin stud 33 respectively, and the upper shock absorber 4 is fixedly connected with two ends of a second guide rail 76 through a first connecting rod 61 and a second connecting rod 62; the first guide rail 71 fixedly crosses over the working section 1 of the circulating water tank along the water flow direction vertical to the working section 1 of the circulating water tank, and the first linear stepping motor 72 is installed on the first guide rail 71 and moves linearly along the first guide rail 71; the rotary stepping motor 73 is fixedly connected to the first stepping motor 72; the rotary disc 74 is fixedly connected with the rotating shaft of the rotating stepping motor 73; a second linear stepper motor 75 is mounted on the turntable 74 and is fixedly connected to the second guide rail 76 and drives the second guide rail 76 to move.
The invention relates to a calibration device of a Doppler current meter sound wave scattering area, which further comprises:
1. the length of the circular tube is equal to the maximum length of a longitudinal section in a sound wave beam crossing volume range at the front end of the Doppler current meter 2, the width and the length of the standard plate 3 are equal, and the crossing volume range is determined according to the using frequency of the Doppler current meter 2, an included angle between a transmitting transducer and a receiving transducer and the beam width.
2. The circular tube is made of titanium alloy.
3. The shape of the upper damper 4 and the shape of the lower damper 5 are both adapted to the shape of the circular tube constituting the standard plate 3, and the upper damper 4 and the lower damper 5 are made of lead and comprise a solid cylinder, a short cone 31 and a long cone 34.
4. The short cone 31 structure and the long cone 34 structure are solid, the ratio of the generatrix to the outer diameter of the short cone 31 structure is 2:1, and the ratio of the generatrix to the outer diameter of the long cone 34 structure is 6: 1.
5. The first connecting rod 61 and the second connecting rod 62 are both cylindrical, and the surfaces of the first connecting rod 61 and the second connecting rod 62 are both provided with sharp sawtooth structures.
The calibration method of the calibration device of the Doppler current meter sound wave scattering area based on the invention comprises the following steps:
the first step is as follows: placing Doppler current meter 2 in working section 1 of circulating water tank, selecting calibration speed V, wherein the calibration speed V satisfies the following conditions: v is 100V, wherein V is the minimum speed measurement precision of the Doppler current meter;
secondly, calculating to obtain the volume range of the crossing of the sound wave beams at the front end of the Doppler current meter 2 according to the using frequency of the Doppler current meter 2, the included angle between the transmitting transducer and the receiving transducer and the wave beam width, wherein the length of a circular tube in the standard plate 3 is equal to the maximum length of a longitudinal section in the crossing volume range, and the width and the length of the standard plate 3 are equal;
the third step: placing a standard plate 3 at the front end of a Doppler current meter 2, wherein the axis direction of the circular tube is consistent with the water flow direction;
the fourth step: controlling the first linear stepping motor 72 to move to make the standard plate 3 slowly move along the first guide rail 71 when the Doppler is detectedWhen the output of the current meter 2 is within the range of ± v, the first linear stepping motor 72 stops working; controlling the second linear stepping motor 75 to move to enable the standard plate 3 to slowly move along the direction of the countercurrent field, stopping the second linear stepping motor 75 when the output of the Doppler current meter 2 is greater than v for the first time, and recording the position coordinate L of one end, close to the Doppler current meter 2, of the standard plate 3 at the moment1；
The fifth step: center normal direction and position coordinate L of transmitting transducer 21 and receiving transducer 22 of doppler current meter 21Connecting, and calculating to obtain a section included angle α of the front ends of the transmitting and receiving beams of the Doppler current meter 2 by using a sine theorem1+α2；
Sixthly, controlling the rotary stepping motor 73 to move at the coordinate position calibrated in the fourth step, enabling the standard plate 3 to slowly rotate along the same circumferential direction, observing the output of the Doppler current meter 2, stopping the rotary stepping motor 73 when the first output is V, and recording the rotating angle β of the standard plate 31Rotating the standard plate 3 to the central normal line position, controlling the rotary stepping motor 73 to move, slowly rotating the standard plate 3 along the opposite circumferential direction, observing the output of the Doppler current meter 2, stopping the rotary stepping motor 73 when the first output is V, and recording the rotating angle β of the standard plate 3 relative to the central normal line direction in the fifth step2Obtaining β cross-sectional angle between the tail of the transmitted and received beams of Doppler current meter 21+β2；
The seventh step: controlling the rotary stepping motor 73 to move, enabling the standard plate 3 to rotate back to the central normal position, controlling the second linear stepping motor 75 to move, enabling the standard plate 3 to slowly move along the direction of the counter current field in the working section, and recording the position coordinate L of one end, close to the Doppler current meter 2, of the standard plate 3 when the Doppler current meter outputs V for the first time2；
Eighth step: obtaining an acoustic scattering region formed by the intersection of the transmit beam and the receive beam, said region having a length L2- L1The regions are of two cone-like configurations, wherein:
the diameter of the bottom surface of the cone satisfies:
(L2-L1)×sinβ1sinα1/(sinβ1+sinα1)+(L2-L1)×sinβ2sinα2/(sinβ2+sinα2)，
the height of the cone near the doppler current meter 2 satisfies:
(L2-L1)×sinβ1cosα1/(sinβ1+sinα1) And (L)2-L1)×sinβ1cosα1/(sinβ1+sinα1)＝(L2-L1)×sinβ2cosα2/(sinβ2+sinα2)，
The height of the cone away from the doppler flow meter 2 satisfies:
(L2-L1)×cosβ1sinα1/(sinβ1+sinα1) And (L)2-L1)×cosβ1sinα1/(sinβ1+sinα1)＝(L2-L1)×cosβ2sinα2/(sinβ2+sinα2)；
The ninth step: and (3) performing grid division and dispersion on the Doppler current meter 2 sound wave scattering area determined in the eighth step, measuring the flow velocity of discrete points by adopting an Ultra LDV, performing mean square processing on the measured flow velocity value, obtaining the standard flow velocity of the Doppler current meter 2, and finishing the measurement calibration of the speed measurement precision of the Doppler current meter 2.
The invention has the beneficial effects that:
1. the calibration of the sound wave scattering region of the Doppler current meter is considered from the aspect of experimental measurement, and the result is more reliable than the result of the current theoretical estimation; the Doppler current meter transmitting transducer and the receiving transducer work normally in the testing process, and the accuracy is higher than that of an acoustic flow imaging method utilizing the reciprocity characteristic of the transducers; secondly, air is arranged inside the standard plate, and the 'water-metal-air-metal-water' is a good sound insulation structure and can prevent sound beams emitted by the transmitting transducer from entering the receiving transducer;
2. the interior of the standard board is hollow and is an air backing in acoustics, and the complex reflection coefficient is calculated by the formula:
in the above formula, ρtIs the density of the titanium alloy, ctIs the sound velocity, k, of titanium alloytWave number of the titanium tube, d is the thickness of the titanium tube, rhowIs the density of water, cwIs the sound velocity of water, and j is an imaginary factor. The reflection coefficient of a titanium tube having a thickness of 1mm obtained by the formula (1) was approximately 1. Therefore, the standard plate can well reflect the sound wave emitted by the transmitting transducer in the Doppler current meter. The standard plate is formed by arranging round tubes, and can inhibit bending waves generated under acoustic excitation; in addition, the acoustic wave wavelength in the circular tube is about 2cm, which is much larger than the thickness of the circular tube, and the acoustic surface wave can not be generated on the surface of the standard plate.
3. The front short conical structure of the standard plate is similar to a sawtooth, stagnation pressure can be reduced, a small 'flow channel' can be formed at the joint of the circular tube and the circular tube, the two structures can break the front flow into small vortexes, the small vortexes flow along the 'flow channel', the separation of the flow on the surface of the standard plate can be well inhibited, and even if the standard plate is rotated by the moving mechanism, the circular tube in the standard plate and incoming flow form a certain angle, cavitation bubbles or cavitation phenomena can not be formed.
4. The flow velocity of the working section of the circulating water tank is 100 times of the measurement accuracy of the Doppler current meter, so that the signal-to-noise ratio is high, therefore, when the Doppler current meter outputs a flow velocity value close to the speed measurement accuracy, the receiving transducer can be considered not to receive a volume reverberation signal of a sound wave scattering area, the reliability of a test result is improved, and the flow velocity is far larger than the sound flow velocity generated by the Doppler current meter transmitting transducer due to the applied voltage (when the transducer is powered on to work, water flow moves from the normal direction of the radiation surface of the transducer due to the nonlinear effect of a medium to form jet flow, also called sound flow), therefore, the flow velocity of 100 times of the speed measurement accuracy is adopted, and the sound flow influence of the transmitting transducer due to the applied voltage can be ignored;
5. the flow velocity value agreed by the calibration method is 100 times of the velocity measurement precision of the Doppler current meter (for example, the velocity measurement precision is 1cm/s, and the flow velocity value is 1m/s), but the flow velocity still belongs to a small flow velocity range, and the thickness of the boundary layer on the surface of the standard plate is extremely thin, so that the layered change of the flow field velocity in the working section of the circulating water tank caused by the boundary layer can be ignored, and the standard plate can be used as a zero flow velocity reference in the calibration process of the Doppler current meter;
6. because the input electric power of the Doppler current meter is only in the order of magnitude of a few watts, the intensity of sound waves generated underwater is limited, so that the sound induced vibration effect of the standard plate can be ignored; the upper vibration absorber and the lower vibration absorber are adopted to inhibit the vibration effect of the standard plate caused by the sound wave beam emitted by the Doppler current meter transducer, and the received sound signal in the Doppler current meter is zero after the emitted sound wave is shielded by the standard plate as much as possible;
7. by carrying out grid division on the sound wave scattering region of the calibrated Doppler current meter and calibrating the flow velocity of the region by adopting an LDV or PIV technology, the measurement work of the velocity measurement precision of the Doppler current meter can be completed in a circulating water tank of a laboratory, and compared with the conventional GPS calibration and other flow velocity devices, the precision of the method is much higher, and the engineering feasibility is stronger.
Drawings
Fig. 1 is an overall block diagram of a calibration apparatus for a sound wave scattering region of a doppler current meter;
FIG. 2 is a schematic illustration of a two-dimensional motion and a rotational motion of a standard plate;
FIG. 3 is a schematic diagram of standard plate length calculation;
FIG. 4 is a schematic diagram of Doppler current meter acoustic scattering region calculation;
FIG. 5 is a flow chart of a method for calibrating a sound wave scattering region of a Doppler current meter;
Detailed Description
The following will further describe a device and a method for calibrating a sound wave scattering area of a doppler current meter according to the present invention with reference to fig. 1 to 5.
As shown in fig. 1 and 2, 1 is a working section of the circulation water tank, 2 is a doppler current meter, 21 is a transmitting transducer, 22 is a receiving transducer, 3 is a standard plate, 31 is a short cone, 32 is a first thin stud, 33 is a second thin stud, 34 is a long cone, 4 is an upper damper, 5 is a lower damper, 61 is a first connecting rod, 62 is a second connecting rod, 621 is an upper vertical rod, 622 is a horizontal rod, 623 is a lower vertical rod, 71 is a first guide rail, 72 is a first linear stepping motor, 73 is a rotary stepping motor, 74 is a rotary table, 75 is a second linear stepping motor, 76 is a second guide rail, and an arrow represents a water flow direction in the working section of the circulation water tank.
A calibration device and method for a Doppler current meter sound wave scattering area comprise a working section 1 of a circulating water tank, a Doppler current meter 2, a standard plate 3, an upper shock absorber 4, a lower shock absorber 5, a first connecting rod 61, a second connecting rod 62 and a moving mechanism;
the working section 1 of the circulating water tank is made of organic glass, the length is 1.6m, the width is 0.4m, the height is 0.4m, water flow with the flow speed range of 0.3 m/s-3 m/s can flow uniformly under the drive of a motor and a propeller, and an Ultra LDV (super laser Doppler velocimeter) is arranged on the side surface of the working section 1 of the circulating water tank, so that the flow speed of the water flow in the water tank can be accurately measured;
doppler current meter 2 is a hand-held ultrasonic Doppler velocimeter LSH10-1A, the velocity measurement range: 0.02-7.00 m/s, accuracy: 1.0% ± 1cm/s, flow rate output when used in still water: . + -. 1cm/s, at which time no flow can be considered;
the main body of the standard plate 3 is a round tube made of titanium alloy, the interior of the round tube is hollow, two ends of the round tube are closed, the front end and the tail end of the round tube are respectively provided with a solid short cone 31 and a solid long cone 34, the ratio of the generatrix of the short cone 31 to the outer diameter is 2:1, the ratio of the generatrix of the long cone 34 to the outer diameter is 6:1, and the standard plate 3 can be fixed between the upper shock absorber 4 and the lower shock absorber 5 by utilizing a first thin stud 32 and a second thin stud 33;
the upper shock absorber 4 is in the same shape as the standard plate 3 and made of lead, the upper shock absorber 4 and the standard plate 3 are fixed together by utilizing the first thin stud 32 and the second thin stud 33, and the upper shock absorber 4 is connected with the moving mechanism through the first connecting rod 61 and the second connecting rod 62;
the lower shock absorber 5 is in the same shape as the standard plate 3 and made of lead, and the lower shock absorber 5 and the standard plate 3 are fixed together by utilizing a first thin stud 32 and a second thin stud 33;
the first connecting rod 61 and the second connecting rod 62 are both cylindrical, threads are tapped at two ends of the first connecting rod 61 and the second connecting rod 62 to fix the upper shock absorber 4, and the surfaces of the first connecting rod 61 and the second connecting rod 62 are provided with sharp sawtooth structures to reduce the flutter effect of the first connecting rod 61 and the second connecting rod 62 caused by the Karman vortex street;
the moving mechanism is composed of a first guide rail 71 vertical to the flowing direction, a first linear stepping motor 72 in linear motion, a rotary stepping motor 73 in rotary motion, a rotary disc 74, a second linear stepping motor 75 in linear motion and a second guide rail 76 parallel to the flowing direction; wherein, the first guide rails 71 in the vertical flow direction are placed at two sides of the working section 1 of the circulating water tank, and the first linear stepper motor 72 in the linear motion can drive the rotary stepper motor 73 in the rotary motion, the rotary table 74, the second linear stepper motor 75 in the linear motion and the second guide rails 76 in the parallel flow direction to move along the vertical flow direction; the rotary stepping motor 73 in rotary motion can drive the rotary disc 74, the second linear stepping motor 75 in linear motion and the guide rail 76 parallel to the flow direction to perform rotary motion; the turntable 74 is installed between the rotary stepping motor 73 which rotates and the second linear stepping motor 75 which linearly moves; a second linear stepper motor 75 moving linearly is installed on the turntable 74, and can drive a second guide rail 76 moving in a direction parallel to the flow direction to move in the direction parallel to the flow direction;
as shown in fig. 5, a device and a method for calibrating a sound wave scattering area of a doppler current meter further include a calibration method, which includes the following steps:
firstly, a Doppler current meter is placed in a working section of a circulating water tank, 100 times of flow field speed of the Doppler current meter is selected as a calibration speed according to precision requirements specified by a use specification of the Doppler current meter, the minimum speed measurement precision of a Doppler current meter 2 in the embodiment is 1cm/s, and therefore the flow speed of the working section in the circulating water tank is 1 m/s;
secondly, estimating and obtaining the volume range crossed by the sound wave beams at the front end of the Doppler current meter 2 by referring to the using frequency of the Doppler current meter 2, the included angle between the transmitting transducer and the receiving transducer and the wave beam width, wherein the length of a circular tube in the standard plate 3 is equal to the maximum length of a longitudinal section in the crossed volume range, namely the length of A, B points in fig. 3, and the width and the length of the standard plate 3 are equal;
thirdly, a standard plate 3 is placed at the front end of the Doppler current meter 2, the axis direction of a circular tube in the standard plate 3 is parallel to the flow and is positioned in the middle of the volume range crossed by the sound wave beams, and if the design of an energy converter and an electronic circuit of the Doppler current meter 2 is reasonable, the output of the Doppler current meter 2 jumps up and down near the minimum speed measurement precision, namely +/-1 cm/s;
fourthly, if the output of the Doppler current meter 2 is larger than 1cm/s, the standard plate 3 is not located at the middle position of the acoustic wave beam crossing volume range of the Doppler current meter 2 at the moment, the standard plate is slowly adjusted along the direction perpendicular to the flow field by using a moving mechanism, and when the output of the Doppler current meter 2 is within the range of +/-1 cm/s, the position of the standard plate 3 is the middle position of the acoustic wave beam crossing of the Doppler current meter 2 at the moment; the standard plate 3 is slowly moved along the direction of the countercurrent field by using a moving mechanism, and when the output of the Doppler current meter 2 is more than 1cm/s for the first time, the position coordinate L at the moment is recorded1；
Fifthly, the normal directions of the centers of the transmitting transducer 21 and the receiving transducer 22 of the Doppler current meter 2 and the position coordinate L at the moment are taken as1Connecting, and calculating to obtain α section angle of front end of Doppler current meter 2 transmitting and receiving wave beam by using sine theorem1+α2；
Sixthly, according to the coordinate position calibrated in the fourth step, taking the joint of the round pipe of the standard plate 3 and the short cone 31 as an axis, slowly rotating the standard plate 3 along the same circumferential direction by using a moving mechanism, observing the output of the Doppler current meter 2, and recording the rotating angle β of the standard plate 3 when the maximum output is 1m/s1(ii) a Returning the standard plate 3 to the original position, slowly rotating the standard plate 3 along the opposite circumferential direction by using a moving mechanism, observing the output of the Doppler current meter 2, and recording when the maximum output is 1m/sRecording the angle β of rotation of the standard plate 3 at that time2The included angle between the cross-sections of the tail ends of the transmitted and received beams of Doppler current meter 2 is β1+β2；
Seventhly, returning the standard plate 3 to the original position, driving the standard plate 3 to slowly move along the direction of a countercurrent field in the working section by using a moving mechanism, observing the output of the Doppler current meter 2, and recording a position coordinate L when the maximum output of the Doppler current meter is 1m/s2；
Eighth step, the length of the sound wave scattering area of the Doppler current meter is obtained as L2-L1Simultaneous equations, solving equation sets, the acoustic scattering area formed by the intersection of the transmitting beam and the receiving beam is in two cone-like structures,
diameter of the bottom surface of the cone: (L)2-L1)×sinβ1sinα1/(sinβ1+sinα1)+(L2-L1)×sinβ2sinα2/(sinβ2+sinα2)，
Height of the front cone: (L)2-L1)×sinβ1cosα1/(sinβ1+sinα1) And (L)2-L1)×sinβ1cosα1/(sinβ1+sinα1)＝(L2-L1)×sinβ2cosα2/(sinβ2+sinα2)，
Height of the back cone: (L)2-L1)×cosβ1sinα1/(sinβ1+sinα1) And (L)2-L1)×cosβ1sinα1/(sinβ1+sinα1)＝(L2-L1)×cosβ2sinα2/(sinβ2+sinα2)；
And ninthly, performing grid division and dispersion on the Doppler current meter 2 sound wave scattering area determined in the eighth step according to a certain length, measuring the flow velocity of discrete points by adopting an Ultra LDV, performing mean square processing on the flow velocity values to serve as the standard flow velocity of the Doppler current meter 2, and further finishing the measurement calibration of the speed measurement precision of the Doppler current meter 2.
It is worth noting that: the included angle of the wave beam at the front end of the calibrated Doppler current meter is 1-2 degrees larger than the included angle of the transmitting wave beam of the transmitting transducer (for example, the included angle of the transmitting wave beam and the receiving wave beam of the Doppler current meter is 2-4 degrees), and because the included angle is small, for example, the arc value corresponding to 1 degree is only 0.017 radian, the area of the fan surface corresponding to the included angle is smaller, and the included angle can be ignored in the test process.
A calibration device and method for a Doppler current meter sound wave scattering area comprises a standard plate, an upper shock absorber, a lower shock absorber, a connecting rod and a moving mechanism, wherein the upper end of the standard plate is provided with the upper shock absorber, the upper shock absorber is arranged at the lower end of the connecting rod, the lower shock absorber is arranged at the lower end of the standard plate, the upper end of the connecting rod is connected with the moving mechanism, and the moving mechanism has a two-dimensional scanning function and a rotating function;
the standard plate is formed by arranging round tubes, the front part of each round tube is connected with a short cone, the tail part of each round tube is connected with a long cone, and the standard plate is made of titanium alloy;
the upper shock absorber is similar to a standard plate in structure, the inner part of the upper shock absorber is of a solid structure, and the upper shock absorber is made of lead;
the lower shock absorber is similar to the standard plate in structure, the inner part of the lower shock absorber is of a solid structure, and the lower shock absorber is made of lead;
the upper damper, the standard plate and the lower damper are fastened together by thin screw columns;
a calibration device for a Doppler current meter sound wave scattering area further comprises a calibration method, and the calibration method comprises the following steps:
the method comprises the following steps that firstly, a Doppler current meter is placed in a working section of a circulating water tank, the speed measurement precision specified by a Doppler current meter use specification is referred, 100 times of the flow field speed is selected as a calibration speed, for example, the minimum speed measurement precision of the Doppler current meter is 1cm/s, and the flow speed of the working section of the circulating water tank is 1 m/s;
secondly, calculating to obtain the crossed volume range of the sound wave beams according to the using frequency of the Doppler current meter, the included angle between the transmitting transducer and the receiving transducer and the working wave beam width of the transducer, and determining the length of a circular tube in the standard plate, wherein the length of the circular tube in the standard plate is equal to the maximum length of a longitudinal section of the crossed volume range, and the width and the length of the standard plate are equal;
thirdly, placing a standard plate at the front end of the Doppler current meter, wherein the axis of a circular tube of the standard plate is parallel to the flowing direction and is positioned in the middle position of a volume range formed by crossing sound wave beams, and if the design of a transducer and an electronic circuit of the Doppler current meter is reasonable, the output of the Doppler current meter can vertically jump around the minimum speed measurement precision, namely +/-1 cm/s;
fourthly, if the output of the Doppler current meter is larger than 1cm/s, the standard plate is not located at the middle position of the cross volume range of the sound wave beams of the Doppler current meter, the standard plate is slowly adjusted along the direction perpendicular to the water flow by using a moving mechanism, and when the output of the Doppler current meter is in the range of +/-1 cm/s, the position of the standard plate is the middle position of the cross volume range of the acoustic wave beams of the Doppler current meter; slowly adjusting the standard plate along the direction of the countercurrent field by using a moving mechanism, and recording the position coordinate L when the output of the Doppler current meter is greater than 1cm/s for the first time1；
Fifthly, the normal directions of the centers of the transmitting transducer and the receiving transducer of the Doppler current meter and the position coordinate L at the moment are used1Connecting, calculating to obtain α section angle of front end of Doppler current meter transmitting and receiving wave beam by sine theorem1+α2；
Sixthly, taking the joint of the circular tube and the short cone of the standard plate as an axis, slowly rotating the standard plate in one direction by using a moving mechanism, observing the output of the Doppler current meter, and recording the rotating angle β of the standard plate when outputting 1m/s for the first time1The output of the Doppler current meter is observed by slowly rotating the standard plate in the opposite direction by the moving mechanism, and when the output is 1m/s for the first time, the rotating angle β of the standard plate is recorded2The included angle between the cross-sections of the tail ends of the transmitting and receiving beams of the Doppler current meter is β1+β2；
Seventhly, returning the standard plate to the original position, and driving the standard plate to slowly advance along the direction of the countercurrent field in the working section by using a moving mechanismMoving, observing output of Doppler current meter, and recording position coordinate L when Doppler current meter outputs 1m/s for the first time2；
Step eight, the length of the acoustic scattering area of the Doppler current meter is L2-L1Simultaneous equations and a solution equation set are adopted, and an acoustic scattering area formed by intersecting a transmitting beam and a receiving beam is of two cone-like structures;
diameter of the bottom surface of the cone: (L)2-L1)×sinβ1sinα1/(sinβ1+sinα1)+(L2-L1)×sinβ2sinα2/(sinβ2+sinα2)，
Height of the front cone: (L)2-L1)×sinβ1cosα1/(sinβ1+sinα1) And (L)2-L1)×sinβ1cosα1/(sinβ1+sinα1)＝(L2-L1)×sinβ2cosα2/(sinβ2+sinα2)，
Height of the back cone: (L)2-L1)×cosβ1sinα1/(sinβ1+sinα1) And (L)2-L1)×cosβ1sinα1/(sinβ1+sinα1)＝ (L2-L1)×cosβ2sinα2/(sinβ2+sinα2)。
Claims (7)
1. A calibration device for a sound wave scattering area of a Doppler current meter is characterized in that: the device comprises a standard plate (3), an upper shock absorber (4), a lower shock absorber (5), a first connecting rod (61), a second connecting rod (62) and a moving mechanism; the standard plate (3) is formed by mutually connecting round pipes which are hollow inside and closed at two ends, a long cone (34) is arranged at one end of each round pipe close to the Doppler current meter (2), and a short cone (31) is arranged at one end far away from the Doppler current meter; the moving mechanism comprises a first guide rail (71), a first linear stepping motor (72), a rotary stepping motor (73), a turntable (74), a second linear stepping motor (75) and a second guide rail (76); the first connecting rod (61) is a straight rod, the second connecting rod (62) comprises an upper vertical rod (621), a horizontal rod (622) and a lower vertical rod (623), and the axis of the lower vertical rod (623) and the axis of the rotating shaft of the rotating stepping motor (73) are on the same straight line; the upper end and the lower end of the standard plate (3) are fixedly connected with an upper shock absorber (4) and a lower shock absorber (5) through a first thin stud (32) and a second thin stud (33) respectively, and the upper shock absorber (4) is fixedly connected with two ends of a second guide rail (76) through a first connecting rod (61) and a second connecting rod (62); the first guide rail (71) fixedly crosses over the working section (1) of the circulating water tank along the water flow direction vertical to the working section (1) of the circulating water tank, and the first linear stepping motor (72) is installed on the first guide rail (71) and moves linearly along the first guide rail (71); the rotary stepping motor (73) is fixedly connected to the first linear stepping motor (72); the rotary disc (74) is fixedly connected with a rotating shaft of the rotary stepping motor (73); the second linear stepping motor (75) is arranged on the turntable (74), is fixedly connected with the second guide rail (76) and drives the second guide rail (76) to move.
2. The device for calibrating the acoustic scattering area of a doppler current meter according to claim 1, wherein: the length of the circular tube is equal to the maximum length of a longitudinal section in a sound wave beam crossing volume range at the front end of the Doppler current meter (2), the width and the length of the standard plate (3) are equal, and the crossing volume range is determined according to the using frequency of the Doppler current meter (2), an included angle between a transmitting transducer and a receiving transducer and the beam width.
3. The device for calibrating the acoustic scattering area of a doppler current meter according to claim 1, wherein: the round tube is made of titanium alloy.
4. The device for calibrating the acoustic scattering area of a doppler current meter according to claim 1, wherein: the shape of the upper shock absorber (4) and the shape of the lower shock absorber (5) are both adapted to the shape of a circular tube forming the standard plate (3) and comprise a solid cylinder, a short cone (31) and a long cone (34), and the upper shock absorber (4) and the lower shock absorber (5) are made of lead.
5. The device for calibrating the acoustic scattering area of a doppler current meter according to claim 1, wherein: the short cone (31) structure and the long cone (34) structure are solid, the ratio of the generatrix to the outer diameter of the short cone (31) structure is 2:1, and the ratio of the generatrix to the outer diameter of the long cone (34) structure is 6: 1.
6. The device for calibrating the acoustic scattering area of a doppler current meter according to claim 1, wherein: the first connecting rod (61) and the second connecting rod (62) are both cylindrical, and the surfaces of the first connecting rod (61) and the second connecting rod (62) are both provided with sharp sawtooth structures.
7. The method for calibrating the device for calibrating the acoustic scattering region of the doppler current meter according to any one of claims 1 to 6, wherein: the method comprises the following steps:
the first step is as follows: placing a Doppler current meter (2) in a working section (1) of a circulating water tank, and selecting a calibration speed V which meets the following requirements: v is 100V, wherein V is the minimum speed measurement precision of the Doppler current meter;
secondly, calculating to obtain the volume range of the sound wave beam crossing of the front end of the Doppler current meter (2) according to the using frequency of the Doppler current meter (2), the included angle between the transmitting transducer and the receiving transducer and the beam width, wherein the length of a circular tube in the standard plate (3) is equal to the maximum length of a longitudinal section in the crossing volume range, and the width and the length of the standard plate (3) are equal;
the third step: placing a standard plate (3) at the front end of a Doppler current meter (2), wherein the axis direction of the circular tube is consistent with the water flow direction;
the fourth step: controlling the first linear stepping motor (72) to move, enabling the standard plate (3) to slowly move along the first guide rail (71), and stopping the first linear stepping motor (72) when the output of the Doppler current meter (2) is in a +/-v range; controlling the second linear stepping motor (75) to move to make the standard plate (3) slowly move along the direction of the countercurrent field, stopping the second linear stepping motor (75) when the output of the Doppler current meter (2) is greater than v for the first time, and recording the resultThe position coordinate L of one end of the time standard plate (3) close to the Doppler current meter (2)1；
The fifth step: the center normal direction and the position coordinate L of a transmitting transducer (21) and a receiving transducer (22) of a Doppler current meter (2)1Connecting, and calculating to obtain a section included angle α of the front ends of the transmitting and receiving beams of the Doppler current meter (2) by using a sine theorem1+α2；
Sixthly, controlling the rotary stepping motor (73) to move at the coordinate position calibrated in the fourth step, enabling the standard plate (3) to slowly rotate along the same circumferential direction, observing the output of the Doppler current meter (2), stopping the rotary stepping motor (73) when the first output is V, and recording the rotating angle β of the standard plate (3)1Rotating the standard plate (3) to the central normal position, controlling the rotating stepping motor (73) to move, enabling the standard plate (3) to slowly rotate along the opposite circumferential direction, observing the output of the Doppler current meter (2), stopping the rotating stepping motor (73) when the first output is V, and recording the rotating angle β of the standard plate (3) relative to the central normal direction in the fifth step2Obtaining β cross-sectional angle between the tail end of the transmitted and received wave beam of Doppler current meter (2)1+β2；
The seventh step: controlling a rotary stepping motor (73) to move, enabling a standard plate (3) to rotate back to the normal position of the center, controlling a second linear stepping motor (75) to move, enabling the standard plate (3) to slowly move along the direction of a countercurrent field in a working section, and recording a position coordinate L of one end, close to a Doppler current meter (2), of the standard plate (3) when the Doppler current meter outputs V for the first time2；
Eighth step: obtaining an acoustic scattering region formed by the intersection of the transmit beam and the receive beam, said region having a length L2-L1The regions are of two cone-like configurations, wherein:
the diameter of the bottom surface of the cone satisfies:
(L2-L1)×sinβ1sinα1/(sinβ1+sinα1)+(L2-L1)×sinβ2sinα2/(sinβ2+sinα2)，
the height of the cone near the doppler current meter (2) satisfies:
(L2-L1)×sinβ1cosα1/(sinβ1+sinα1) And (L)2-L1)×sinβ1cosα1/(sinβ1+sinα1)＝(L2-L1)×sinβ2cosα2/(sinβ2+sinα2)，
The height of the cone away from the Doppler flowmeter (2) satisfies:
(L2-L1)×cosβ1sinα1/(sinβ1+sinα1) And (L)2-L1)×cosβ1sinα1/(sinβ1+sinα1)＝(L2-L1)×cosβ2sinα2/(sinβ2+sinα2)；
The ninth step: and (3) performing grid division and dispersion on the sound wave scattering area of the Doppler current meter (2) determined in the eighth step, measuring the flow velocity of a discrete point by adopting an Ultra LDV, performing mean square processing on the measured flow velocity value, obtaining the standard flow velocity of the Doppler current meter (2), and finishing the measurement calibration of the speed measurement precision of the Doppler current meter (2).
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| CN111650403B (en) * | 2019-08-02 | 2022-02-25 | 水利部交通运输部国家能源局南京水利科学研究院 | Doppler current profiler calibration device and calibration method thereof |
| CN110702941A (en) * | 2019-10-30 | 2020-01-17 | 天津大学 | Measuring device and method for sensing characteristics of flow velocity sensor |
| CN111220818B (en) * | 2019-12-10 | 2021-10-19 | 哈尔滨工程大学 | Device for calibrating speed measurement precision of Doppler current meter |
| CN112485466A (en) * | 2020-11-13 | 2021-03-12 | 长江水利委员会长江科学院 | Calibration system and method of three-dimensional pulsating flow velocity measuring device |
| CN113533780A (en) * | 2021-07-02 | 2021-10-22 | 唐山现代工控技术有限公司 | Integrated navigation type Doppler profile flow measurement method |
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