A non-invasive vortex center pressure measurement method and system based on cavitation dynamics

Abstract

The present invention relates to a non-invasive vortex center pressure measurement method and system based on cavitation dynamics. The non-invasive vortex center pressure measurement method based on cavitation dynamics described in the present invention comprises the following steps: filtering and degassing the fluid to be measured to reduce the free gas concentration in the fluid to be measured; generating a vortex to be measured; irradiating the fluid to be measured with a laser on the path through which the vortex to be measured flows to form cavitation bubbles; performing high-speed photography on the cavitation bubbles to record the size changes of the cavitation bubbles as they grow or collapse in the vortex core after being captured by the vortex to be measured; observing the cavitation bubbles to determine the growth or collapse of the cavitation bubbles in the vortex core, and combining the corresponding cavitation dynamics equation to calculate the vortex center pressure through inversion. The non-invasive vortex center pressure measurement method based on cavitation dynamics described in the present invention has the advantages of high precision, strong anti-interference ability, and reliable results.

Description

Technical Field

[0001] The present invention relates to the field of vortex pressure measurement, and in particular to a non-invasive vortex center pressure measurement method and system based on cavitation dynamics. Background Art

[0002] Vortex is a common phenomenon in fluid flow, and the central pressure is an important parameter to characterize the vortex strength, stability and energy distribution. By measuring the pressure at the center of the vortex, we can better understand the formation mechanism, evolution law of the vortex and its impact on the flow. From the perspective of engineering application, pressure fluctuations at the center of the vortex may cause flow instability, resulting in equipment vibration or noise. For example, in aerospace, shipbuilding and pipeline engineering, changes in the pressure at the center of the vortex may be closely related to fluid-induced vibration and noise. Therefore, in the design of fluid machinery (such as pumps, turbines, compressors, etc.), the pressure information at the center of the vortex can help engineers optimize the flow channel design, evaluate the stability of the flow, and take measures to suppress vibration, reduce energy loss and improve equipment efficiency. In the prior art, an invasive pressure sensor is usually used to approach the vortex to measure the pressure information at the center of the vortex.

[0003] However, invasive pressure measurement methods can disrupt the vortex structure, making it difficult to accurately measure the pressure at the vortex center. Even placing sensors at the vortex's periphery can disrupt the flow and alter the vortex's characteristics. The recent rise of particle image velocimetry (PIV)-based pressure field inversion offers a new approach to measuring vortex pressure. However, this technique relies on reconstructing pressure by calculating partial derivatives of the velocity field. During this process, even small measurement errors in the velocity field are multiplied, severely impacting the accuracy of the resulting pressure field data. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a non-invasive vortex center pressure measurement method and system based on cavitation dynamics, which has the advantages of high precision, strong anti-interference ability and reliable results.

[0005] The present invention provides a non-invasive vortex center pressure measurement method based on cavitation dynamics, comprising the following steps:

[0006] S1: adding a fluid to be tested into a container to be tested, filtering and degassing the fluid to be tested, so as to reduce the free gas concentration in the fluid to be tested;

[0007] S2 generates a vortex to be measured in the container to be measured; irradiates the fluid to be measured with a laser along a path through which the vortex to be measured flows, thereby forming cavitation bubbles;

[0008] S3: while generating the cavitation bubbles, simultaneously taking high-speed photographs of the cavitation bubbles to record the size changes of the cavitation bubbles as they grow or collapse at the vortex center after being captured by the vortex to be measured;

[0009] S4: Observe the cavitation bubbles, determine whether the cavitation bubbles grow or collapse in the vortex core, and calculate the vortex core pressure through inverse calculation based on the corresponding cavitation dynamics equation.

[0010] The non-invasive vortex center pressure measurement method based on cavitation dynamics of the present invention introduces cavitation bubbles, detects the size changes and change time of the cavitation bubbles growing or collapsing in the vortex center, and calculates the vortex center pressure through inversion calculation; there is no need to perform invasive detection on the vortex to be measured, which improves the anti-interference ability of the system.

[0011] Furthermore, the step S4 includes:

[0012] S41 If the cavitation bubble grows in the vortex center, the vortex center pressure is calculated using the following formula:

[0013]

[0014] Where R is the bubble radius, t is the time, is the rate of change of cavitation radius, p v is the saturated vapor pressure of the fluid, p c is the vortex center pressure, ρ L is the fluid density.

[0015] Furthermore, the step S4 includes:

[0016] S42 If the cavitation bubble collapses at the vortex center, the vortex center pressure is calculated using the following formula:

[0017]

[0018] Among them, t c is the time from the beginning of cavitation collapse to the minimum size, R0 is the radius of cavitation when it begins to collapse, ρ L is the fluid density, p v is the saturated vapor pressure of the fluid, p c is the vortex center pressure.

[0019] Furthermore, in step S1, the free gas concentration in the fluid to be measured is reduced until spontaneous cavitation does not occur in the vortex to be measured.

[0020] Furthermore, in step S1, the free gas concentration in the fluid to be measured is reduced by filtering the fluid to be measured and / or heating and evaporating the fluid to be measured.

[0021] Furthermore, in step S2, the size of the cavitation bubbles is adjusted by adjusting the intensity and irradiation time of the laser radiation.

[0022] A non-invasive vortex center pressure measurement system based on cavitation dynamics, used for the above-mentioned non-invasive vortex center pressure measurement method based on cavitation dynamics, includes: a container to be measured, a vortex generator for generating a vortex, a high-speed photography device and a laser generating device; the vortex generator is arranged in the container to be measured, and the vortex to be measured is formed after the fluid to be measured flows through the vortex generator; the high-speed photography device is arranged beside the container to be measured, facing the container to be measured; the laser generating device is arranged beside the container to be measured, and the laser emitted by the laser generating device is injected into the container to be measured, irradiating the fluid to be measured in the container to be measured, forming cavitation.

[0023] Furthermore, it also includes a laser adjustment device, and the laser emitted by the laser generating device passes through the laser adjustment device and is emitted into the container to be tested; the laser adjustment device is used to adjust the focusing position of the laser emitted by the laser generating device; the laser generating device can adjust the intensity and irradiation time of the laser.

[0024] Furthermore, the container to be tested is provided with at least two transparent windows; the high-speed photography device photographs the inside of the container to be tested through one of the transparent windows; and the laser emitted by the laser generating device is emitted into the container to be tested through the other transparent window.

[0025] Furthermore, it also includes a synchronization device, which is electrically connected to the high-speed photography device and the laser generating device respectively. When the synchronization device detects that the laser generating device is started, the synchronization device sends a synchronization signal to the high-speed photography device, so that the high-speed photography device is started synchronously.

[0026] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a non-invasive vortex center pressure measurement method based on cavitation dynamics according to an embodiment of the present application;

[0028] Figure 2 Schematic diagram of a non-invasive vortex center pressure measurement system based on cavitation dynamics according to an embodiment of the present application;

[0029] Figure 3 This is a schematic diagram of a vortex generated by water flowing through a hydrofoil according to an embodiment of the present application;

[0030] Figure 4 This is a schematic diagram of the change of radius R with time t during the cavitation growth process collected in Example 2 of the present application.

[0031] In the accompanying drawings, the technical features indicated by the reference numerals are as follows:

[0032] 1. Container to be tested; 2. Vortex generator; 3. High-speed photography device; 4. Laser generating device; 5. Laser adjustment device; 6. Synchronization device. DETAILED DESCRIPTION

[0033] In existing technologies, pressure measurements at the center of a vortex are typically performed using invasive pressure sensors or using particle image velocimetry (PIV) to invert the pressure field. However, these methods have low interference immunity and are prone to significant errors, seriously affecting the accuracy of the resulting pressure data.

[0034] In order to solve the above problems, the inventors have discovered through research that by irradiating a vortex flow field with a laser, cavitation will be introduced into the vortex flow field. The internal pressure of the cavitation is the saturated vapor pressure of the fluid. After that, the cavitation is captured by the vortex under the action of the vortex pressure field and enters the center of the vortex. According to the relationship between the pressure at the center of the vortex and the saturated vapor pressure of the fluid, when the pressure at the center of the vortex is less than the saturated vapor pressure of the fluid, the cavitation grows and increases in volume under the action of the internal and external pressure difference; when the pressure at the center of the vortex is greater than the saturated vapor pressure of the fluid, the cavitation is compressed and collapses, and the volume decreases. Regardless of whether the cavitation grows or collapses, its size change obeys the basic laws of cavitation dynamics, and the cavitation itself will not have a significant impact on the vortex.

[0035] Based on the above principles, the present invention proposes a non-invasive vortex center pressure measurement method based on cavitation dynamics, which has high anti-interference ability.

[0036] Example 1

[0037] See also Figure 1 , an embodiment of the present application provides a non-invasive vortex center pressure measurement method based on cavitation dynamics.

[0038] The specific steps include:

[0039] S1: Add the fluid to be tested into the container to be tested, and fully filter and degas the fluid to be tested to reduce the free gas concentration in the fluid to be tested;

[0040] S2: generating a vortex to be measured in the container to be measured; irradiating the path through which the vortex to be measured flows with a laser to form cavitation bubbles;

[0041] S3: While generating cavitation bubbles, high-speed photography is simultaneously performed on the cavitation bubbles to record the size change and change time of the cavitation bubbles growing or collapsing in the vortex core after being captured by the vortex to be measured;

[0042] S4: Observe the cavitation bubbles and determine whether they grow or collapse in the vortex core. Based on whether the cavitation bubbles grow or collapse, the vortex core pressure is calculated by inverse calculation in combination with the cavitation dynamics equation.

[0043] Furthermore, step S4 specifically includes the following steps:

[0044] S41: If the cavitation bubble grows in the vortex center, the vortex center pressure is calculated using the following formula;

[0045]

[0046] Where R is the bubble radius, t is the time, is the rate of change of cavitation radius, p v is the saturated vapor pressure of the fluid, p c is the vortex center pressure, ρ L is the fluid density; in the formula, the fluid saturated vapor pressure p v and fluid density ρ L is a known value; the rate of change of cavitation radius is the detection value, which is substituted into the above formula and then the vortex core pressure p is obtained by reverse calculation. c .

[0047] S42: If the cavitation bubble collapses at the vortex center, the vortex center pressure is calculated using the following formula:

[0048]

[0049] Where, t c is the time from the beginning of cavitation collapse to the minimum size, R0 is the radius of cavitation when it begins to collapse, ρ L is the fluid density, p v is the saturated vapor pressure of the fluid, p c is the vortex center pressure; in the formula, the fluid saturated vapor pressure p v and fluid density ρ L are known values; the radius R0 when the cavitation begins to collapse and the time t from the beginning of cavitation collapse to the minimum size c is the detection value, which is substituted into the above formula and then the vortex core pressure p is obtained by reverse calculation. c .

[0050] Furthermore, in step S1, the fluid under test is filtered and heated and evaporated to reduce the free gas concentration in the fluid under test until spontaneous cavitation no longer occurs within the vortex. To reduce the interference caused by cavitation due to the low pressure at the center of the vortex, the fluid under test needs to be fully filtered during the experiment, and the concentration of dissolved gases needs to be reduced by heating and evaporation.

[0051] Furthermore, step S2 also includes: adjusting the size of the cavitation bubbles by adjusting the intensity and irradiation time of the laser radiation.

[0052] See also Figure 2 The present application also provides a non-invasive vortex center pressure measurement system based on cavitation dynamics for use in the aforementioned measurement method. The pressure measurement system of the present application includes a container to be tested 1, a vortex generator 2 for generating a vortex, a high-speed photography device 3, a laser generating device 4, a laser adjustment device 5, and a synchronization device 6. The vortex generator 2 is disposed in the container to be tested 1, and the fluid to be tested forms a vortex after flowing through the vortex generator 2. The high-speed photography device 3 is disposed beside the container to be tested 1, facing the container to be tested 1, and is used to photograph cavitation bubbles in the container to be tested 1. The laser generating device 4 and the laser adjusting device 5 are arranged beside the container to be tested 1. The laser emitted by the laser generating device 4 passes through the laser adjusting device 5 and is emitted into the container to be tested 1, irradiating the fluid to be tested in the container to be tested 1 to form cavitation; the laser adjusting device 5 is used to adjust the focal position of the laser emitted by the laser generating device 4; the laser generating device 4 can adjust the intensity and irradiation time of the laser, thereby changing the size of the cavitation; the synchronization device 6 is electrically connected to the high-speed photography device 3 and the laser generating device 4 respectively. When the synchronization device 6 detects that the laser generating device 4 is started, the synchronization device 6 sends a synchronization signal to the high-speed photography device 3, so that the high-speed photography device 3 is started synchronously.

[0053] Furthermore, at least two transparent windows are provided on the container to be tested; the high-speed photography device photographs the inside of the container to be tested through one of the transparent windows; and the laser emitted by the laser generating device is emitted into the container to be tested through the other transparent window.

[0054] See also Figure 3 In some embodiments, the vortex generator 2 is a hydrofoil having a curved leading edge at one end and a sharp, tapering trailing edge at the other end. The hydrofoil has a spiral or curved wing-shaped cross-section. The hydrofoil promotes flow separation, causing the fluid flowing through the hydrofoil to form a vortex.

[0055] Example 2

[0056] See also Figure 4 The present application provides a specific embodiment of a non-invasive vortex center pressure measurement method based on cavitation dynamics, which specifically includes the following steps:

[0057] S1: Water is selected as the fluid to be tested. The experimental temperature is stabilized at 20°C. The vortex center pressure measurement system in Example 1 is used as the measurement device. Water is added to the test container 1 and fully filtered and degassed to reduce the free gas concentration in the water to below 1.5 ppm.

[0058] S2: generating a vortex to be measured in the container 1 to be measured; irradiating the path through which the vortex to be measured flows with a laser to form cavitation bubbles;

[0059] S3: While generating cavitation bubbles, simultaneously taking high-speed photographs of the cavitation bubbles, recording the size changes and change time of the cavitation bubbles growing or collapsing at the vortex core after being captured by the vortex to be measured; in this embodiment, different experimental parameters were used for the same measurement device to generate vortices of different intensities, and the size changes of the cavitation bubbles as they grew in them were recorded, obtaining Experimental Data 1 and Experimental Data 2;

[0060] S4: The cavitation bubble was observed to grow at the vortex center after being captured by the vortex to be measured, and the radius change rate of experimental data 1 and experimental data 2 was measured. are 0.92 and 0.65 m / s respectively; under the experimental temperature of 20°C, the density of water is ρ L =1000kg / m 3 , saturated vapor pressure p v =2338Pa; Substitute the above data into the following formula;

[0061]

[0062] Obtain the vortex center pressure p of two different vortices to be measured c They are 1068Pa and 1704Pa respectively.

[0063] The non-invasive vortex center pressure measurement method and system based on cavitation dynamics in this application calculates the vortex center pressure by measuring the size changes of cavitation bubbles. Compared with existing technologies, this method reduces the intrusiveness of the measured vortex, improves the overall system's anti-interference ability, and thus improves the accuracy of the test results.

[0064] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, and the present invention is intended to encompass such modifications and variations.

Claims

1. A non-invasive vortex center pressure measurement method based on cavitation dynamics, characterized in that: The following steps are involved: S1: adding a fluid to be tested into a container to be tested, filtering and degassing the fluid to be tested, so as to reduce the free gas concentration in the fluid to be tested; S2 generates a vortex to be measured in the container to be measured; irradiates the fluid to be measured with a laser along a path through which the vortex to be measured flows, thereby forming cavitation bubbles; S3: while generating the cavitation bubbles, simultaneously taking high-speed photographs of the cavitation bubbles to record the size changes of the cavitation bubbles as they grow or collapse at the vortex center after being captured by the vortex to be measured; S4: observing the cavitation bubbles, determining whether the cavitation bubbles grow or collapse in the vortex core, and calculating the vortex core pressure by inverse calculation based on the corresponding cavitation dynamics equation; The step S4 comprises: S41 If the cavitation bubble grows in the vortex center, the vortex center pressure is calculated using the following formula: Where R is the bubble radius, t is the time, is the rate of change of cavitation radius, p v is the saturated vapor pressure of the fluid, p c is the vortex center pressure, ρ L is the fluid density; S42 If the cavitation bubble collapses at the vortex center, the vortex center pressure is calculated using the following formula: Among them, t c is the time from the beginning of cavitation collapse to the minimum size, R0 is the radius of cavitation when it begins to collapse, ρ L is the fluid density, p v is the saturated vapor pressure of the fluid, p c is the vortex center pressure.

2. The non-invasive vortex center pressure measurement method based on cavitation dynamics according to claim 1, characterized in that: In step S1 , the free gas concentration in the fluid to be measured is reduced until spontaneous cavitation does not occur in the vortex to be measured.

3. The non-invasive vortex center pressure measurement method based on cavitation dynamics according to claim 2, characterized in that: In step S1 , the free gas concentration in the fluid to be measured is reduced by filtering the fluid to be measured and / or heating and evaporating the fluid.

4. The non-invasive vortex center pressure measurement method based on cavitation dynamics according to any one of claims 1 to 3, characterized in that: In the step S2, the size of the cavitation bubbles is adjusted by adjusting the intensity and irradiation time of the laser radiation.

5. A non-invasive vortex center pressure measurement system based on cavitation dynamics, used to implement the non-invasive vortex center pressure measurement method based on cavitation dynamics according to any one of claims 1 to 4, characterized in that: include: A container to be tested, a vortex generator for generating a vortex, a high-speed photography device, and a laser generating device; The vortex generator is arranged in the container to be tested, and the fluid to be tested forms a vortex to be tested after flowing through the vortex generator; the high-speed photography device is arranged beside the container to be tested, facing the container to be tested; the laser generating device is arranged beside the container to be tested, and the laser emitted by the laser generating device is injected into the container to be tested, irradiating the fluid to be tested in the container to be tested, forming cavitation.

6. The non-invasive vortex center pressure measurement system based on cavitation dynamics according to claim 5, characterized in that: It also includes a laser adjustment device, and the laser emitted by the laser generating device passes through the laser adjustment device and is emitted into the container to be tested; the laser adjustment device is used to adjust the focus position of the laser emitted by the laser generating device; the laser generating device can adjust the intensity and irradiation time of the laser.

7. The non-invasive vortex center pressure measurement system based on cavitation dynamics according to claim 6, characterized in that: The container to be tested is provided with at least two transparent windows; the high-speed photography device photographs the inside of the container to be tested through one of the transparent windows; the laser emitted by the laser generating device is emitted into the container to be tested through the other transparent window.

8. The non-invasive vortex center pressure measurement system based on cavitation dynamics according to claim 7, characterized in that: It also includes a synchronization device, which is electrically connected to the high-speed photography device and the laser generating device respectively. When the synchronization device detects that the laser generating device is started, the synchronization device sends a synchronization signal to the high-speed photography device, so that the high-speed photography device is started synchronously.

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