CN113358312A - Vortex-induced vibration synchronous measurement method based on high-speed cavitation water tunnel - Google Patents
Vortex-induced vibration synchronous measurement method based on high-speed cavitation water tunnel Download PDFInfo
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- G01M7/00—Vibration-testing of structures; Shock-testing of structures
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- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
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- G01M7/00—Vibration-testing of structures; Shock-testing of structures
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Abstract
The invention relates to a vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel, and belongs to the technical field of hydraulic and hydroelectric engineering and ocean ship engineering. The implementation method of the invention comprises the following steps: the control software is communicated with a circulating pump rotating speed control device through a serial port, and the rotating speed of the circulating pump is controlled to adjust the incoming flow speed of the cavitation water tunnel to be continuously changed; the synchronous measurement of the structural vibration speed is realized through an NI acquisition card while the control software adjusts the rotating speed; in the process of adjusting the rotating speed by using control software, the rotating speeds of the pressure pump and the vacuum pump are controlled by the NI acquisition card, and the pressure is controlled in real time by controlling the rotating speeds of the pressure pump and the vacuum pump, so that the stability of the inlet pressure of the test section is realized. The invention can realize flow field pressure control in the synchronous measurement process, realize stable and controllable inlet cavitation number, accurately measure the frequency locking interval range and the vortex-induced vibration strength and frequency change during frequency locking, and solve the technical problems related to vortex-induced vibration in the fields of hydraulic and hydroelectric engineering and ocean ship engineering.
Description
Technical Field
The invention relates to a vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel, in particular to a method capable of realizing continuous change of flow field velocity and synchronous measurement of structural vibration velocity and flow velocity, and belongs to the technical field of hydraulic and hydroelectric engineering and ocean ship engineering.
Background
Frequency locking is an important phenomenon in the excitation of bluff body vortex, and is characterized by large structural vibration amplitude, and the vibration can cause structural fatigue and possibly cause catastrophic failure of the structure. The experimental method is an important means for researching frequency locking. Scholars at home and abroad provide flow field environments by adopting circulating water tunnels and the like, and systematically research vortex-induced vibration characteristics of different structures by combining methods of a vibration measurement system, a high-speed camera system and the like.
At present, for experimental research on hydrofoil vortex-induced vibration, the vibration speed and frequency of a structure are usually measured at a fixed incoming flow speed to obtain the frequency locking characteristic and the corresponding vibration strength of the structure, and the method can be used for obtaining the measurement result at a selected speed. However, the vortex-induced vibration characteristics obtained based on the method are limited by the acquired speed points because the speed is in discrete distribution, and the vortex-induced vibration intensity and frequency variation in the frequency-locked interval cannot be clearly described. Therefore, the establishment of the vortex excitation vibration measurement method which can realize the continuous change of the flow field flow velocity and the synchronous measurement of the structural vibration has important significance.
Disclosure of Invention
The invention discloses a vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel, which aims to solve the technical problems that: vortex-induced vibration synchronous measurement is realized based on the high-speed cavitation water tunnel, continuous change of incoming flow speed and synchronous measurement of structural vibration speed are realized based on software control (Labview), and real-time control of pressure can be realized.
The purpose of the invention is realized by the following technical scheme:
the invention discloses a vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel, which comprises the following steps:
the method comprises the following steps: the control software is communicated with the circulating pump rotating speed control device through a serial port, and then the incoming flow speed of the cavitation water tunnel is adjusted by controlling the rotating speed of the circulating pump, so that the continuous change of the incoming flow speed is realized.
Starting a control software, setting an initial rotating speed n1, a high rotating speed n2, a high rotating speed duration time delta t and rotating speed change speeds k1 and k2, sending signals to a rotating speed controller through a PC (personal computer) end and a serial port by control software, controlling a circulating pump motor to reach the initial rotating speed n1 and the rotating speed increase speed k1 by the rotating speed controller to reach the high rotating speed n2, and starting to reach the rotating speed n1 from the high rotating speed n2 at the rotating speed reduction speed of k2 when the high rotating speed n2 is kept constant delta t.
Step two: and the synchronous measurement of the structural vibration speed is realized through an NI acquisition card while the control software adjusts the rotating speed.
The control software sends a signal to the rotating speed controller, and simultaneously, the control software controls the PC end to synchronously send another signal, the signal controls the NI acquisition card to send a rising edge signal, after the laser vibration meter receives the rising edge signal, the laser vibration meter starts to automatically acquire the vibration speed of the object to be detected, and the acquisition result is transmitted to the PC end through the NI acquisition card.
Step three: in the process of adjusting the rotating speed by using control software, the rotating speeds of the pressure pump and the vacuum pump are controlled by the NI acquisition card, the pressure is controlled in real time by controlling the rotating speeds of the pressure pump and the vacuum pump, and further the stability of the inlet pressure of the test section is realized, wherein the inlet pressure value p is set in the control software.
The pressure value p is set in the control software, the control software controls the PC end to send out a current signal, the current signal controls the rotating speed of the pressure pump and the vacuum pump through the NI acquisition card, the rotating speed of the pressure pump controls the increasing speed of the pressure value, the rotating speed of the vacuum pump controls the decreasing speed of the pressure value, and the control pressure value is increased/decreased to enable the inlet pressure value to be stabilized near p.
The method also comprises the following four steps: in the process of synchronously measuring the incoming flow speed and the structural vibration speed, the continuous change of the incoming flow speed and the synchronous measurement of the structural vibration speed are realized on the basis of the steps from the first step to the third step, the vortex-induced vibration characteristic is obtained, the frequency locking interval range and the vortex-induced vibration strength and frequency change during frequency locking are accurately measured, and then the technical problems related to the vortex-induced vibration in the fields of water conservancy and hydropower engineering and ocean ship engineering are solved.
Preferably, the control software is selected from Labview, and the Labview is communicated with the circulating pump rotating speed control device through an RS232 serial port.
Has the advantages that:
1. the invention discloses a vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel, which can realize continuous change of incoming flow speed and synchronous measurement of structural vibration speed in the synchronous measurement process of the incoming flow speed and the structural vibration speed to obtain vortex-induced vibration characteristics.
2. The vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel disclosed by the invention realizes the vortex-induced vibration synchronous measurement based on the high-speed cavitation water tunnel, can realize the flow field pressure control in the synchronous measurement process, weakens the influence of pressure fluctuation on experimental conditions, realizes the stability and controllability of inlet cavitation number, and improves the effectiveness and accuracy of experimental results.
3. The invention discloses a synchronous measurement method of vortex-induced vibration based on a high-speed cavitation water tunnel, which is characterized in that control software is communicated with a circulating pump rotating speed control device through a serial port, and further the incoming flow speed of the cavitation water tunnel is adjusted by controlling the rotating speed of a circulating pump, so that the continuous change of the incoming flow speed is realized; the synchronous measurement of the structural vibration speed is realized through an NI acquisition card while the control software adjusts the rotating speed; in the process of adjusting the rotating speed by using control software, the rotating speeds of the pressure pump and the vacuum pump are controlled by the NI acquisition card, and the pressure is controlled in real time by controlling the rotating speeds of the pressure pump and the vacuum pump, so that the stability of the inlet pressure of the test section is further realized.
Drawings
FIG. 1 is a schematic view of a vortex-induced vibration synchronous measurement control system;
FIG. 2 is a schematic diagram of an implementation of the synchronous measurement technique of the present invention;
FIG. 3 is a flow chart of implementing the synchronous measurement technique according to the present invention;
FIG. 4 is a synchronized measurement of incoming flow velocity;
FIG. 5 simultaneous measurement of the vibration velocity of a structure;
fig. 6 is a result of a short-time fourier transform of structural vibrations.
Detailed Description
For a better understanding of the objects and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
Example 1:
this embodiment is disclosed in conjunction with the accompanying drawings, which take a rectangular hydrofoil of NACA 0009 as an example, and the specific embodiment of the present invention is shown in fig. 1-5.
As shown in fig. 1 and fig. 2, the method for synchronously measuring vortex-induced vibration based on high-speed cavitation water tunnel disclosed in this embodiment includes the following specific steps:
the method comprises the following steps: and the control software (Labview) is communicated with the circulating pump rotating speed control device through an RS232 serial port, and further the incoming flow speed of the cavitation water tunnel is adjusted by controlling the rotating speed of the circulating pump, so that the continuous change of the incoming flow speed is realized. The specific embodiment is as follows: starting control software, setting initial rotation speed of 90rpm, high rotation speed of 300rpm, high rotation speed duration of 10s, and rotation speed change speed of 1.67rpm/s and-1.67 rpm/s, sending a signal to a rotation speed controller through a PC (personal computer) end by the control software, controlling a circulating pump motor to increase the speed of 1.67rpm/s at the initial rotation speed of 90rpm and the speed of 1.67rpm/s to reach the high rotation speed of 300rpm, and starting to decrease the speed of the circulating pump from the high rotation speed of 300rpm to the rotation speed of 30rpm at the speed of-1.67 rpm/s for 10 s. The actual measured speed variation process is shown in fig. 4.
Step two: and the synchronous measurement of the structural vibration speed is realized through an NI acquisition card while the control software adjusts the rotating speed. The specific embodiment is as follows: the control software sends a signal to the rotating speed controller, and simultaneously, the control software controls the PC end to synchronously send another signal, the signal controls the NI acquisition card to send a rising edge signal, after the laser vibration meter receives the rising edge signal, the laser vibration meter starts to acquire the vibration speed, and the acquisition result is transmitted to the PC end through the NI acquisition card. The structural vibration response obtained by the simultaneous measurement is shown in fig. 5.
Step three: in the process of adjusting the rotating speed by using control software, the rotating speeds of the pressure pump and the vacuum pump are controlled by the NI acquisition card, so that the stability of the inlet pressure of the test section is realized. The specific embodiment is as follows: setting control pressure to be 3bar in control software, controlling a PC end to send out a current signal by the control software, controlling the rotating speed of a pressure pump and a vacuum pump by the current signal through an NI acquisition card, and controlling the vacuum pump to run up and reduce the pressure when the inlet pressure is more than 3 bar; and when the inlet pressure is less than 3bar, controlling the pressure pump to run in an accelerating way, increasing the pressure and finally realizing that the inlet pressure is stabilized at about 3 bar.
Step four: in the process of synchronously measuring the incoming flow speed and the structural vibration speed, the continuous change of the incoming flow speed and the synchronous measurement of the structural vibration speed are realized on the basis of the steps from the first step to the third step, the vortex-induced vibration characteristic is obtained, the vortex-induced vibration strength and the frequency change in the frequency locking interval are clearly predicted, and then the technical problems related to the vortex-induced vibration in the field of marine ship engineering are solved.
The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (6)
1. A vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
the method comprises the following steps: the control software is communicated with a circulating pump rotating speed control device through a serial port, and then the incoming flow speed of the cavitation water tunnel is adjusted by controlling the rotating speed of the circulating pump, so that the continuous change of the incoming flow speed is realized;
step two: the synchronous measurement of the structural vibration speed is realized through an NI acquisition card while the control software adjusts the rotating speed;
step three: in the process of adjusting the rotating speed by using control software, the rotating speeds of the pressure pump and the vacuum pump are controlled by the NI acquisition card, the pressure is controlled in real time by controlling the rotating speeds of the pressure pump and the vacuum pump, and further the stability of the inlet pressure of the test section is realized, wherein the inlet pressure value p is set in the control software.
2. The vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel as claimed in claim 1, characterized in that: and step four, in the process of synchronously measuring the incoming flow speed and the structural vibration speed, the continuous change of the incoming flow speed and the synchronous measurement of the structural vibration speed are realized based on the step one to the step three, the vortex-induced vibration characteristic is obtained, the frequency locking interval range and the vortex-induced vibration strength and frequency change during frequency locking are accurately measured, and then the technical problems related to the vortex-induced vibration in the fields of water conservancy and hydropower engineering and ocean ship engineering are solved.
3. The vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel as claimed in claim 1 or 2, characterized in that: the first implementation method comprises the following steps of,
starting a control software, setting an initial rotating speed n1, a high rotating speed n2, a high rotating speed duration time delta t and rotating speed change speeds k1 and k2, sending signals to a rotating speed controller through a PC (personal computer) end and a serial port by control software, controlling a circulating pump motor to reach the initial rotating speed n1 and the rotating speed increase speed k1 by the rotating speed controller to reach the high rotating speed n2, and starting to reach the rotating speed n1 from the high rotating speed n2 at the rotating speed reduction speed of k2 when the high rotating speed n2 is kept constant delta t.
4. The vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel as claimed in claim 3, characterized in that: the second step is realized by the method that,
the control software sends a signal to the rotating speed controller, and simultaneously, the control software controls the PC end to synchronously send another signal, the signal controls the NI acquisition card to send a rising edge signal, after the laser vibration meter receives the rising edge signal, the laser vibration meter starts to automatically acquire the vibration speed of the object to be detected, and the acquisition result is transmitted to the PC end through the NI acquisition card.
5. The vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel as claimed in claim 4, characterized in that: the third step is to realize the method as follows,
the pressure value p is set in the control software, the control software controls the PC end to send out a current signal, the current signal controls the rotating speed of the pressure pump and the vacuum pump through the NI acquisition card, the rotating speed of the pressure pump controls the increasing speed of the pressure value, the rotating speed of the vacuum pump controls the decreasing speed of the pressure value, and the control pressure value is increased/decreased to enable the inlet pressure value to be stabilized near p.
6. The vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel as claimed in claim 5, characterized in that: and the control software selects Labview, and the control software Labview is communicated with the circulating pump rotating speed control device through an RS232 serial port.
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