Wall pressure measurement device and method

Abstract

This invention relates to a wall pressure measuring device and method. The device includes a circular metal substrate with a piezoelectric chip sealed inside. The piezoelectric chip is connected to an external signal acquisition system. The metal substrate has an integrated stepped structure, including a lower half-step and an upper half-step. Multiple pressure-guiding holes are formed on the surface of the upper half-step to transmit the pressure from the surface of the upper half-step to the internal piezoelectric chip. Multiple bolt grooves are formed along the circumference of the lower half-step for mounting bolts, so that the metal substrate is fixedly mounted on an auxiliary plate matching the wall surface to be measured at the required measurement angle. Compared with the prior art, this invention can achieve a smaller measurement point spacing, a closer arrangement of sensors, ensure that the measurement plane is flush with the wall surface to be measured, and obtain pressure data from more spatial locations by rotating and adjusting the measurement angle, thereby improving the accuracy and reliability of the measurement results.

Description

Technical Field

[0001] This invention relates to the field of wall pressure measurement technology, and in particular to a wall pressure measurement device and method. Background Technology

[0002] Wall-induced pressure fluctuations in the turbulent boundary layer play a crucial role in flow-induced noise. On the one hand, they directly radiate noise outwards, and on the other hand, they excite vibrations in the solid wall structure, thus forming secondary sound sources. Therefore, placing pressure sensors on the wall to directly acquire high-fidelity fluctuating pressure data is an essential experimental method for conducting research on flow-induced noise and flow-induced vibration.

[0003] The wall pressure of a turbulent boundary layer on a flat plate is a function of space and time, and can be decomposed into mean pressure and fluctuating pressure: in, x These are coordinates along the flow direction. z It is the spanwise coordinate. t It is time. It is time-averaged pressure. Pressure pulsation is defined as the difference between the instantaneous wall pressure and its time-averaged value. The wall pressure of a turbulent boundary layer is closely related to turbulent characteristics, and its statistical features are often characterized using a wavenumber-frequency spectrum, where spectrum refers to the signal's power spectral density. For a three-dimensional random signal in the space-space-time domain, the cross-correlation function between two points is first calculated, and then a three-dimensional Fourier transform is performed to map the correlation function from the space-time domain to the wavenumber-frequency domain, yielding the power spectral density function. The formula for calculating the cross-correlation function is: in, ξ The distance between two points is the flow direction distance. ζ The spanwise distance between the two points. For common array vectors, The flow direction is a unit vector. It is a unit vector in the span direction. τ For time intervals, The wavenumber-frequency spectrum can be obtained by performing a Fourier transform on the cross-correlation function to represent the ensemble average. in, k x For the flow wave number, k z For spanwise wavenumber, ω Angular velocity, relative to frequency f The relationship is ω=2πf , It is the imaginary unit.

[0004] In experimental research, a pressure sensor is needed to sample the pressure signal. According to the Nyquist-Shannon sampling theorem, for the highest frequency component... The signal sampling frequency must reach at least 1000 MHz. Only in this way can the spectrum of the sampled discrete signal avoid aliasing, thus ensuring that the signal can be completely determined by the sampled values. The same principle applies to the spatial domain; if the maximum wavenumber is... Then the distance between adjacent measuring points Must meet Otherwise, the high-frequency components in space will fold, resulting in wavenumber-frequency spectrum distortion.

[0005] For measuring fluctuating pressure on the wall of a turbulent boundary layer in the laboratory, it is often necessary to simultaneously measure pressure from pressure sensors at different locations to obtain the corresponding discrete pressure signal (i.e., including average pressure and fluctuating pressure). Currently, a common method for measuring fluctuating pressure on the wall of a turbulent boundary layer in the laboratory is to use independent miniature pressure sensors and assemble multiple pressure sensors on the wall of the water tunnel measurement section to form a pressure sensor array. The calculation of the wavenumber-frequency spectrum places certain requirements on the time sampling frequency and spatial sampling interval of the pressure sensor array. Existing pressure sensors can achieve sampling frequencies of hundreds of kilohertz or several megahertz (Hz), thus meeting the requirements in terms of time sampling frequency. However, existing measurement schemes have the following drawbacks in terms of spatial sampling interval: 1. Insufficient spatial resolution: Most mature pressure sensors are cylindrical, with the diameter of the sensing part at the front end generally being 5 mm, and very few products are less than 4 mm. Due to the size limitation of the sensor, the spacing between the measuring points is directly limited, which cannot meet the requirements of high spatial resolution.

[0006] 2. Installation structure limitations: When the sensor is installed on the flat plate, it also requires the use of threads, sealing rings, nuts and other structures after the front end of the cylinder for fitment. The diameter of these structures is larger than the diameter of the sensing part, which further limits the close arrangement of the sensors.

[0007] 3. Installation accuracy issues: During sensor installation, the threads are usually tightened manually, making it difficult to ensure that the sensor's measuring plane is perfectly flush with the flat surface. Such convexities or depressions in the measuring plane can affect the actual flow field, thus impacting the accuracy of the measurement results.

[0008] 4. Sealing Performance Challenges: In water tunnel experiments, sealing performance must also be considered to prevent water ingress into the sensor devices. Existing sensor installation methods struggle to achieve both tight arrangement and precise installation of sensors while ensuring sealing performance.

[0009] In summary, existing sensor designs have significant shortcomings in terms of spatial resolution, installation coplanar accuracy, and sealing performance, making it difficult to meet the high-precision, high-fidelity measurement requirements for pressure pulsation on the wall of a flat plate turbulent boundary layer under limited space conditions. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art by providing a wall pressure measuring device and method that can achieve smaller measuring point spacing, close sensor arrangement, and ensure that the measuring plane is flush with the wall surface to be measured, thereby improving the accuracy and reliability of the measurement results.

[0011] The objective of this invention can be achieved through the following technical solution: a wall pressure measuring device, comprising a circular metal substrate, wherein a piezoelectric chip and a matching measuring circuit are sealed and installed inside the metal substrate, the measuring circuit is connected to a signal amplifier outside the metal substrate, the signal amplifier is connected to a signal acquisition system, the metal substrate is an integrated stepped structure, comprising a lower half-step and an upper half-step, the surface of the upper half-step is provided with multiple pressure-guiding holes for transmitting the pressure on the surface of the upper half-step to the internal piezoelectric chip, and the lower half-step is provided with multiple bolt grooves along the circumferential direction for installing bolts, so as to fix the metal substrate to an auxiliary plate matching the wall surface to be measured according to the required measuring angle.

[0012] Furthermore, the plurality of pressure-guiding holes are arranged at equal intervals along any diameter direction of the upper half-step surface, and the angle between the straight line formed by the arrangement of the plurality of pressure-guiding holes and the incoming flow is the measurement angle.

[0013] Furthermore, the lower surface edge of the lower half-step is provided with an angle line along the circumferential direction for positioning and measuring angles.

[0014] Furthermore, the diameter of the pressure-guiding hole is 0.8 mm, the hole center-to-center distance is greater than or equal to 3 mm, and the hole depth is 2 mm.

[0015] Furthermore, a sealing groove is provided on the lower half-step for embedding and installing a sealing ring.

[0016] Furthermore, the metal substrate is internally sealed with a power supply circuit and a compensation circuit that are respectively connected to the piezoelectric chip. The compensation circuit includes a temperature compensation unit, a sensitivity compensation unit, and a zero-point compensation unit.

[0017] Furthermore, an integrated connector is provided on the metal substrate, one end of which is connected to the measurement circuit and the other end is connected to an external signal amplifier.

[0018] Furthermore, the metal substrate is made of stainless steel 17-4PH or 316L.

[0019] A method for measuring wall pressure includes the following steps: S1. Determine the measurement angle by rotating the metal base, then fix the metal base to the auxiliary plate, and then install the auxiliary plate onto the wall surface to be measured. S2. First, the piezoelectric chip inside the metal substrate is zero-point calibrated. After calibration, the voltage signal of the piezoelectric chip is read through an external signal acquisition system and converted to obtain the corresponding pressure data, thus completing the pressure measurement at the current measurement angle. Afterwards, the measurement angle was readjusted and pressure measurements were performed to obtain pressure time history data at multiple spatial locations.

[0020] Compared with the prior art, the present invention has the following advantages: This invention designs a circular metal substrate into which a piezoelectric chip is sealed and installed. The metal substrate adopts an integrated stepped structure, including a lower half-step and an upper half-step. Multiple pressure-indicating holes are formed on the surface of the upper half-step, and multiple bolt grooves are formed along the circumference of the lower half-step for mounting bolts. This allows the metal substrate to be fixedly mounted to an auxiliary plate that matches the surface to be measured, according to the required measurement angle. By rotating the metal substrate, the measurement angle can be easily adjusted. The pressure on the surface of the upper half-step is transmitted to the internal piezoelectric chip through the pressure-indicating holes, and the pressure measurement data is obtained through the piezoelectric chip. This allows for obtaining pressure data from more measurement points even in limited space, while ensuring the measurement plane is flush with the surface to be measured, reducing disturbance to the flow field, and thus improving the accuracy and reliability of the measurement results.

[0021] This invention designs multiple pressure-sensing holes arranged at equal intervals along any diameter direction on the surface of the upper half-step. The angle between the straight line formed by the arrangement of the multiple pressure-sensing holes and the incoming flow is the measurement angle. In addition, an angle line is provided along the circumferential direction on the lower surface edge of the lower half-step, which can facilitate the user to position and adjust the measurement angle, thereby improving the flexibility and comprehensiveness of the measurement.

[0022] The present invention features a pressure tapping hole diameter of only 0.8 mm, resulting in a smaller actual pressure measurement area and more accurate measurement results. This small-diameter pressure tapping hole design effectively reduces the spatial averaging effect and can more accurately reflect local changes in wall pressure. In addition, the hole center spacing between the pressure tapping holes is designed to be greater than or equal to 3 mm, which reduces the spacing between pressure measuring points to only 3 mm. This improvement enhances spatial resolution, allowing more measuring points to be arranged in the same area to obtain more detailed pressure distribution information.

[0023] This invention seals the piezoelectric chip, its power supply circuit, and compensation circuit inside a metal substrate. The signal output by the piezoelectric chip is transmitted to an external signal amplifier and then to a signal acquisition system via an integrated connector. This ensures both sealing performance and the detectability and accuracy of the piezoelectric chip's output signal. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the device structure of the present invention; Figure 2 This is a schematic diagram of the bottom of the device of the present invention; Figure 3 This is a cross-sectional schematic diagram of the device in the embodiment; Figure 4 This is a partial enlarged view of the pressure tapping hole in the cross-section of the device in the embodiment; Figure 5 This is a circuit diagram of the signal amplifier in the embodiment; Figure 6 This is a schematic diagram of the power supply circuit in the embodiment; Figure 7 This is a schematic diagram of the compensation circuit in the embodiment; Figure 8 This is a schematic diagram of the method flow of the present invention; The markings in the diagram are as follows: 11. Lower half step, 12. Upper half step, 13. Sealing groove, 14. Pressure hole, 15. Bolt groove. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0026] Example like Figure 1 As shown, a wall pressure measuring device includes a circular metal substrate with an integrated stepped structure comprising a lower step 11 and an upper step 12. The surface of the upper step 12 has multiple pressure-guiding holes 14 for transmitting pressure from the surface of the upper step 12 to a piezoelectric chip inside the metal substrate (the piezoelectric chip is sealed inside the metal substrate and connected to an external signal amplifier). The lower step 11 has multiple bolt grooves 15 along its circumference for mounting bolts to fix the metal substrate to an auxiliary plate matching the wall surface to be measured at the desired measurement angle. The lower step 11 also has a sealing groove 13 for embedding a sealing ring. Furthermore, the multiple pressure-guiding holes 14 are arranged at equal intervals along any diameter direction of the surface of the upper step 12, and the angle between the straight line formed by the arrangement of the multiple pressure-guiding holes 14 and the incoming flow is the measurement angle.

[0027] To facilitate users in intuitively and accurately adjusting the required measurement angle, such as Figure 2As shown, an angle line is provided along the circumferential direction on the lower surface edge of the lower half-step 11 to locate the measurement angle, so as to obtain pressure data at different spatial positions. Adjusting the measurement angle by rotating the metal base is beneficial for obtaining wall pressure data at multiple locations. It can obtain pressure data from more measuring points even with limited space, increase the number of common array vectors, improve the quality of wavenumber-frequency spectrum, and greatly increase the flexibility and comprehensiveness of the measurement, providing richer data support for studying the pressure characteristics of turbulent boundary layers.

[0028] This embodiment measures the pressure on the walls of a water tunnel. The specific dimensions of the metal base are as follows: Figure 3 and Figure 4 As shown, the metal substrate is made of stainless steel 17-4PH or 316L, possessing high strength and good corrosion resistance, and is circular in shape. Multiple circular pressure-inducing holes 14 are evenly distributed along a straight line on the surface of the upper half-step 12. During measurement, these pressure-inducing holes 14 are filled with the liquid to be measured, thereby transmitting the pressure on the surface of the upper half-step 12 to the internal piezoelectric chip. The piezoelectric chip converts the pressure signal into an electrical signal, thus realizing the measurement of the wall pressure. In this embodiment, the diameter of the pressure-inducing holes 14 is 0.8 mm, the center-to-center spacing is 3 mm, and the depth of the holes is 2 mm. During processing, the hole openings are required to be free of chamfers and burrs to ensure smooth fluid flow and reduce interference with the flow field. The pressure tapping orifice 14 has a diameter of only 0.8 mm, resulting in a smaller actual pressure measurement area and more accurate measurement results. This small-diameter pressure tapping orifice design effectively reduces the spatial averaging effect and can more accurately reflect the local changes in wall pressure. It is of great significance for measuring small pressure fluctuations in the turbulent boundary layer. Furthermore, the pressure measurement point spacing is reduced to only 3 mm, which helps to improve spatial resolution, allowing more measurement points to be arranged in the same area to obtain more detailed pressure distribution information and wavenumber-frequency characteristics over a larger wavenumber range.

[0029] A sealing groove 13 is provided on the lower half step 11. The depth and width of the sealing groove 13 are designed according to the actual size of the sealing ring. After assembly, the sealing ring is compressed in a controlled manner, and the deformation is within the design range, forming a continuous and reliable elastic sealing interface, which effectively prevents liquid in the water tunnel from seeping into the interior of the measuring device and ensures the normal operation of the measuring device in the water tunnel experiment.

[0030] The metal substrate is also provided with multiple bolt slots 15, which are used to securely install the metal substrate in the designated position. The engagement of the bolts with the bolt slots ensures that the metal substrate does not shift during the experiment.

[0031] The dimensions of the metal substrate, such as the diameter of the lower half-step 11, the diameter of the upper half-step 12, and the dimensions of the sealing groove 13 and bolt groove 15, can all be customized according to the specific requirements of the water tunnel test section. However, the diameter, center-to-center spacing, and depth of the pressure-inducing holes 14 are fixed values ​​to ensure measurement accuracy and consistency. The surface of the metal substrate is precision-machined to meet the requirements of flatness and smoothness, reducing interference with the flow field and thus improving the accuracy of the measurement results.

[0032] In addition, signal amplifiers (such as Figure 5 (As shown) is used to amplify the weak electrical signal output by the piezoelectric chip, so that it reaches an amplitude suitable for subsequent processing, thereby improving the detectability and accuracy of the signal.

[0033] The metal substrate contains sealed power supply circuits (such as those connected to the piezoelectric chip) that are respectively mounted inside. Figure 6 (as shown) and compensation circuit (such as) Figure 7 As shown in the diagram, in this embodiment, the power supply circuit uses a constant current source to provide a stable power supply for the entire circuit, ensuring the normal operation of the measuring device. The compensation circuit includes a temperature compensation unit, a sensitivity compensation unit, and a zero-point compensation unit. Considering that changes in ambient temperature may affect the measurement results, the temperature compensation unit can compensate for temperature changes, thereby improving the accuracy and stability of the measurement.

[0034] An integrated connector is provided on the metal substrate. One end of the integrated connector is connected to the piezoelectric chip and the other end is connected to the signal amplifier. The signal line plugged into the integrated connector is used to connect to the external signal amplifier and then to the signal acquisition system to realize the transmission of electrical signals.

[0035] The above circuit design improves signal stability and accuracy, further enhancing the overall performance of the measuring device.

[0036] Based on the above measuring device, a method for measuring wall pressure is implemented, such as... Figure 8 As shown, it includes the following steps: S1. Determine the measurement angle by rotating the metal base, then fix the metal base to the auxiliary plate, and then install the auxiliary plate onto the wall surface to be measured. S2. First, the piezoelectric chip inside the metal substrate is zero-point calibrated. After calibration, the voltage signal of the piezoelectric chip is read through an external signal acquisition system and converted to obtain the corresponding pressure data, thus completing the pressure measurement at the current measurement angle. Afterwards, the measurement angle was readjusted and pressure measurements were performed to obtain pressure time history data at multiple spatial locations.

[0037] This embodiment applies the above solution, and the main processes are as follows: I. Equipment Installation: To mount the pressure measuring device onto the water tunnel wall, an auxiliary plate matching the water tunnel is used. Screw holes and threads matching the dimensions of the metal base are pre-machined into the auxiliary plate. During the experiment, bolts are used to secure the pressure measuring device to the auxiliary plate through bolt slots 15. In this embodiment, eight bolts are used during installation, and the bolt tightening force is kept as even as possible to ensure the pressure measuring device is flush with the surface of the auxiliary plate. Then, the pressure measuring device and auxiliary plate are mounted as a single unit onto the water tunnel wall, completing the installation process.

[0038] II. Connect the dots: Connect the leads of the pressure measuring device to the signal acquisition system to form a suitable circuit.

[0039] III. Signal Measurement During the water tunnel experiment, the piezoelectric chip was zero-point calibrated according to standard measurement procedures to eliminate systematic errors. After calibration, pressure measurements were performed to obtain voltage signals. Then, the measured voltage signals were converted into pressure values ​​using a pre-calibrated relationship, thereby obtaining pressure-time history data for a specific spatial location.

[0040] IV. Rotate and adjust the measuring angle After completing the current angle measurement task, loosen or remove the bolts, rotate the disc pressure measuring device so that the straight line where the pressure inlet is located forms different angles with the water flow from the tunnel (positioned by the scale lines), and then tighten the bolts. Repeat the measurement process to obtain pressure-time history data for more spatial locations, providing more comprehensive information for the study of turbulent boundary layer wall pressure.

[0041] In summary, this scheme can achieve a smaller measurement point spacing, thereby obtaining a larger measurement point spatial resolution; In situations where space is limited, the number of co-array vectors can be increased to improve the accuracy of wavenumber frequency spectrum calculation and increase data integrity. It can ensure that the measuring plane is flush with the wall surface to be measured, reduce disturbance to the flow field, and ensure the accuracy and reliability of the measurement results.

Claims

1. A wall pressure measuring device, characterized in that, The device includes a circular metal substrate, inside which a piezoelectric chip and a matching measurement circuit are sealed and installed. The measurement circuit is connected to a signal amplifier outside the metal substrate, and the signal amplifier is connected to a signal acquisition system. The metal substrate is an integrated stepped structure, including a lower half step (11) and an upper half step (12). The surface of the upper half step (12) is provided with multiple pressure-guiding holes (14) for transmitting the pressure on the surface of the upper half step (12) to the internal piezoelectric chip. The lower half step (11) is provided with multiple bolt grooves (15) along the circumferential direction for installing bolts to fix the metal substrate to an auxiliary plate that matches the wall surface to be measured according to the required measurement angle. The plurality of pressure-guiding holes (14) are arranged along any diameter direction of the surface of the upper half-step (12), and the angle between the straight line formed by the arrangement of the plurality of pressure-guiding holes (14) and the incoming flow is the measurement angle; The lower surface edge of the lower half step (11) is provided with an angle line along the circumferential direction for positioning and measuring angles; The diameter of the pressure-guiding hole (14) is 0.8 mm, the hole center spacing is greater than or equal to 3 mm, and the hole depth is 2 mm.

2. The wall pressure measuring device according to claim 1, characterized in that, The lower half step (11) is provided with a sealing groove (13) for embedding and installing a sealing ring.

3. The wall pressure measuring device according to claim 1, characterized in that, The metal substrate is internally sealed with a power supply circuit and a compensation circuit that are respectively connected to the piezoelectric chip. The compensation circuit includes a temperature compensation unit, a sensitivity compensation unit, and a zero-point compensation unit.

4. The wall pressure measuring device according to claim 1, characterized in that, An integrated connector is provided on the metal substrate, one end of which is connected to the measurement circuit and the other end is connected to an external signal amplifier.

5. The wall pressure measuring device according to claim 1, characterized in that, The metal substrate is made of stainless steel 17-4PH or 316L.

6. A method for measuring wall pressure, implemented using the wall pressure measuring device as described in claim 1, characterized in that, Includes the following steps: S1. Determine the measurement angle by rotating the metal base, then fix the metal base to the auxiliary plate, and then install the auxiliary plate onto the wall surface to be measured. S2. First, the piezoelectric chip inside the metal substrate is zero-point calibrated. After calibration, the voltage signal of the piezoelectric chip is read through an external signal acquisition system and converted to obtain the corresponding pressure data, thus completing the pressure measurement at the current measurement angle. Afterwards, the measurement angle was readjusted and pressure measurements were performed to obtain pressure time history data at multiple spatial locations.

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