CN113358312B - A Synchronous Measurement Method of Vortex-Induced Vibration Based on High-speed Cavitation Water Tunnel - Google Patents

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

A Synchronous Measurement Method of Vortex-Induced Vibration Based on High-speed Cavitation Water Tunnel

technical field

The invention relates to a method for synchronous measurement of vortex-induced vibration based on a high-speed cavitation water tunnel, in particular to a method capable of realizing continuous change of flow field flow velocity and synchronous measurement of structural vibration velocity and flow velocity, belonging to water conservancy and hydropower engineering, ocean ship engineering technology field.

Background technique

Frequency locking is an important phenomenon in vortex-induced vibration of blunt bodies, which is characterized by large structural vibration amplitudes, which can cause structural fatigue and possibly catastrophic failure of the structure. For a long time, experimental methods have been an important means to study frequency locking. Scholars at home and abroad have used circulating water tunnels to provide flow field environments, combined with vibration measurement systems, high-speed camera systems, etc., to systematically study the characteristics of vortex-induced vibration of different structures.

At present, for the experimental research of hydrofoil vortex-induced vibration, the structural vibration velocity and frequency are usually measured at a fixed incoming flow velocity to obtain the structural frequency-locking characteristics and corresponding vibration intensity. Using this method, the measurement results at a selected velocity can be obtained . However, based on the vortex-induced vibration characteristics obtained by this method, since the velocity is a discrete distribution, limited by the selected velocity points, it is impossible to clearly describe the vortex-induced vibration intensity and frequency changes in the frequency-locked interval. Therefore, it is of great significance to establish a vortex-induced vibration measurement method that can continuously change the flow field velocity and realize the synchronous measurement of structural vibration.

Contents of the invention

The technical problem to be solved by the vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel disclosed by the present invention is: to realize the vortex-induced vibration synchronous measurement based on the high-speed cavitation water tunnel, and to realize the flow velocity based on software control (Labview) Continuous change and synchronous measurement of structural vibration velocity, and real-time control of pressure can be realized.

The purpose of the present invention is achieved through the following technical solutions:

A vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel disclosed by the present invention comprises the following steps:

Step 1: The control software communicates with the circulation pump speed control device through the serial port, and then adjusts the incoming flow speed of the cavitation water tunnel by controlling the circulating pump speed to realize continuous change of the incoming flow speed.

Start the control software, set the initial speed n1, high speed n2, high speed duration Δt, speed change speed k1, k2, and then the control software sends signals to the speed controller through the PC terminal and serial port, and the speed controller controls the cycle The pump motor starts at the initial speed n1, the speed increases at the speed k1, and reaches the high speed n2. After maintaining the high speed n2 at a constant Δt time, the circulating pump begins to decrease the speed at the speed of k2 from the high speed n2 to the speed n1.

Step 2: While the control software is adjusting the speed, the synchronous measurement of the structural vibration speed is realized through the NI acquisition card.

While the control software sends a signal to the speed controller, the control software controls the PC to send another signal synchronously. This signal controls the NI acquisition card to send a rising edge signal. After the laser vibrometer receives the rising edge signal, the laser measurement The vibrator starts to automatically collect the vibration velocity of the object to be measured, and transmits the collection results to the PC through the NI collection card.

Step 3: In the process of using the control software to adjust the speed, control the speed of the pressure pump and the vacuum pump through the NI acquisition card, and realize the real-time control of the pressure by controlling the speed of the pressure pump and the vacuum pump, and then realize the stability of the inlet pressure of the test section. The pressure value p is set in the control software.

Set the pressure value p in the control software, and the control software controls the PC to send a current signal. The current signal controls the speed of the pressure pump and the vacuum pump through the NI acquisition card. The speed of the pressure pump controls the speed of the increase of the pressure value, and the speed of the vacuum pump Control the decrease speed of the pressure value, and control the increase/decrease of the pressure value to stabilize the inlet pressure value near p.

It also includes step 4: in the process of synchronous measurement of incoming flow velocity and structural vibration velocity, based on steps 1 to 3, the continuous change of incoming flow velocity and the synchronous measurement of structural vibration velocity are obtained to obtain the characteristics of vortex-induced vibration and accurately measure the frequency-locked interval Range and frequency-locked vortex-induced vibration intensity and frequency changes, and then solve technical problems related to vortex-induced vibration in the fields of water conservancy and hydropower engineering and marine ship engineering.

Preferably, the control software is optional Labview, and the control software Labview communicates with the circulation pump speed control device through the RS232 serial port.

Beneficial effect:

1. A vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel disclosed by the present invention can realize the continuous change of the incoming flow velocity and the synchronization of the structural vibration velocity in the process of synchronous measurement of the incoming flow velocity and the structural vibration velocity Measure and obtain the characteristics of vortex-induced vibration. Compared with the traditional single-point measurement method, it can accurately measure the range of frequency-locked interval and the intensity and frequency change of vortex-induced vibration during frequency-locking, and then solve the problem of vortex-induced vibration in the fields of water conservancy and hydropower engineering and marine ship engineering. Vibration related technical issues.

2. A vortex-induced vibration synchronous measurement method based on a high-speed cavitation water tunnel disclosed in the present invention realizes vortex-induced vibration synchronous measurement based on a high-speed cavitation water tunnel, and can realize flow field pressure control during the synchronous measurement process and weaken pressure fluctuations The influence on the experimental conditions can realize the stable and controllable inlet cavitation number, and improve the validity and accuracy of the experimental results.

3. A vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel disclosed by the present invention, the control software communicates with the circulating pump speed control device through the serial port, and then adjusts the incoming flow speed of the cavitation water tunnel by controlling the circulating pump speed , to realize the continuous change of incoming flow velocity; while the control software adjusts the rotational speed, the synchronous measurement of the structural vibration velocity is realized through the NI acquisition card; in the process of using the control software to adjust the rotational speed, the rotational speed of the pressure pump and the vacuum pump is controlled through the NI acquisition card, Real-time control of the pressure is realized by controlling the speed of the pressure pump and the vacuum pump, and then the stability of the inlet pressure of the test section is realized.

Description of drawings

Figure 1 is a schematic diagram of a vortex-induced vibration synchronous measurement and control system;

Fig. 2 is the synchronous measurement technique implementation schematic diagram of the present invention;

Fig. 3 is the implementation process of the synchronous measurement technology described in the present invention;

Fig. 4 is the synchronous measurement result of incoming flow velocity;

Fig. 5 Synchronous measurement results of structural vibration velocity;

Figure 6 is the short-time Fourier transform result of structural vibration.

detailed description

In order to better illustrate the purpose and advantages of the present invention, the content of the invention will be further described below in conjunction with the accompanying drawings and examples.

Example 1:

This embodiment discloses with reference to the accompanying drawings, taking the NACA 0009 rectangular hydrofoil as an example, the specific implementation of the present invention is shown in Figures 1-5.

As shown in Figure 1 and Figure 2, a vortex-induced vibration synchronous measurement method based on high-speed cavitation water tunnel disclosed in this embodiment, the specific implementation steps are as follows:

Step 1: The control software (Labview) communicates with the circulating pump speed control device through the RS232 serial port, and then adjusts the incoming flow speed of the cavitation water tunnel by controlling the circulating pump speed to realize continuous change of the incoming flow speed. The specific implementation plan is as follows: start the control software, set the initial speed of 90rpm, the high speed of 300rpm, the duration of high speed of 10s, the speed of speed change of 1.67rpm/s, -1.67rpm/s, and then the control software is connected to the speed controller through the PC Send a signal, and the speed controller controls the circulation pump motor to start at an initial speed of 90rpm, and the speed increases at a speed of 1.67rpm/s, reaching a high speed of 300rpm. After maintaining the high speed of 300rpm for 10s, the circulation pump starts to decelerate at a speed of -1.67rpm/s. The small speed goes from high speed 300rpm to high speed 30rpm. The actual measured speed change process is shown in Figure 4.

Step 2: While the control software is adjusting the speed, the synchronous measurement of the structural vibration speed is realized through the NI acquisition card. The specific implementation plan is as follows: while the control software sends a signal to the speed controller, the control software controls the PC to send another signal synchronously. This signal controls the NI acquisition card to send a rising edge signal, and the laser vibrometer receives the rising edge signal. After receiving the signal, the laser vibrometer starts to collect the vibration velocity, and transmits the collection results to the PC through the NI collection card. The structural vibration response obtained by synchronous measurement is shown in Fig. 5.

Step 3: In the process of using the control software to adjust the speed, control the speed of the pressure pump and vacuum pump through the NI acquisition card to stabilize the inlet pressure of the test section. The specific implementation plan is as follows: set the control pressure to 3bar in the control software, and the control software controls the PC to send a current signal, which controls the speed of the pressure pump and vacuum pump through the NI acquisition card. When the inlet pressure is greater than 3bar, the vacuum pump is controlled to speed up. , reduce the pressure; when the inlet pressure is less than 3bar, control the pressure pump to accelerate the operation, increase the pressure, and finally realize the inlet pressure is stable at about 3bar.

Step 4: In the process of synchronous measurement of the incoming flow velocity and the structural vibration velocity, based on steps 1 to 3, the continuous change of the incoming flow velocity and the synchronous measurement of the structural vibration velocity are obtained to obtain the characteristics of the vortex-induced vibration and clearly predict the vibration in the frequency-locked interval. The intensity and frequency of vortex-induced vibration change, and then solve the technical problems related to vortex-induced vibration in the field of marine ship engineering.

The specific description above further elaborates the purpose, technical solution and beneficial effect of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not used to limit the protection of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (3)

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;

starting control software, setting initial rotating speed n1, high rotating speed n2, high rotating speed duration time delta t and rotating speed change rates k1 and k2, sending signals to a rotating speed controller through a PC (personal computer) end and a serial port by the control software, controlling the circulating pump motor to increase from the initial rotating speed n1 to the high rotating speed n2 at the rotating speed change rate k1 by the rotating speed controller, and reducing the rotating speed of the circulating pump motor from the high rotating speed n2 to the initial rotating speed n1 at the rotating speed change rate k2 after keeping the high rotating speed n2 constant delta t time;

step two: 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 a pressure pump and a vacuum pump are controlled by an NI acquisition card, the real-time control of the pressure is realized by controlling the rotating speeds of the pressure pump and the vacuum pump, and further the stability of the inlet pressure of a test section is realized, wherein an inlet pressure value p is set in the control software;

the inlet 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.

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 on the basis of the step one to the step three, the vortex-induced vibration characteristic is obtained, and the vortex-induced vibration strength and the frequency change in the frequency locking interval range and the frequency locking process are accurately measured.

3. The vortex-induced vibration synchronous measurement method based on the high-speed cavitation water tunnel as claimed in claim 1, characterized in that: labview is selected as the control software, and the control software Labview is communicated with the circulating pump rotating speed control device through an RS232 serial port.

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