Wind tunnel flow field non-contact flow velocity and manifold measuring device

Abstract

The invention discloses a non-contact flow velocity and manifold measuring device for a wind tunnel flow field. The non-contact flow velocity and manifold measuring device comprises a tracing bubble generation unit, a multi-camera image acquisition unit, an illumination unit, a synchronous trigger control unit and a data processing terminal. The tracer bubble generation unit adjusts the pressure, content and proportion of helium, air and bubble liquid through a console, a required bubble field is generated according to experimental requirements, and a bubble release pipe is arranged close to a fan and does not intervene in a flow field measurement area. The multi-camera image acquisition unit comprises at least three digital cameras arranged outside a wind tunnel, and covers a target measurement area from different positions, heights and angles. The illumination unit adopts a front illumination mode, a surface light source is arranged at the top of the wind tunnel, and a removable light absorption material layer is arranged on the wall surface of the measurement area. And the synchronous triggering control unit realizes synchronous shooting of multiple cameras in a hard triggering mode. And the data processing terminal receives the image data and executes a Lagrange particle tracking algorithm to realize non-intrusive accurate measurement of the velocity and manifold of the flow field.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel technology, and more specifically, to a non-contact flow velocity and manifold measurement device for wind tunnel flow fields. Background Technology

[0002] Wind tunnel testing is an important tool for studying the wind environment in buildings; however, existing flow field velocity measurement technologies have many limitations. Currently, the main contact measurement methods, such as anemometers and pitot tubes, require the sensing unit to directly intervene in the flow field. This causes the measuring device itself to significantly interfere with the airflow, altering the original characteristics of the flow field and failing to reflect the true flow state. Furthermore, limited by sensor size and placement density, these methods can only obtain sparse, discrete point data with low spatial resolution, making it difficult to capture complete information on complex flow structures such as building-around flow and vortex shedding. Summary of the Invention

[0003] The present invention provides a non-contact flow velocity and manifold measurement device for wind tunnel flow fields, in order to overcome at least one technical problem existing in the prior art.

[0004] This invention provides a non-contact flow velocity and manifold measurement device for wind tunnel flow fields, comprising: The tracer bubble generating unit includes a control console, a gas source, a bubble liquid supply component, and a bubble release tube. The control console is connected to the gas source and the bubble liquid supply component and is used to control the pressure, content, and ratio of helium, air, and bubble liquid to achieve the release of the required tracer bubbles. The bubble release tube is set close to the fan and located in the middle of each row of fans without interfering with the flow field. A multi-camera image acquisition unit, comprising at least three digital cameras arranged outside the wind tunnel, with each camera having a different position, height, and shooting angle, collectively covering the target measurement area inside the wind tunnel; The lighting unit includes multiple surface light sources, which are arranged at the top of the wind tunnel and above the measurement area, providing illumination to the measurement area using frontal lighting. The measurement area on the inner wall of the wind tunnel is provided with a light-absorbing material layer, which is removably fixed to the wind tunnel wall. A synchronization trigger control unit is provided, which is connected to the digital camera and the data processing terminal respectively via control lines. It adopts a hard triggering method to realize the synchronization triggering of multiple cameras. The data processing terminal is connected to the multi-camera image acquisition unit via a data cable and is used to receive and process the acquired image data. The data processing terminal is configured to execute the Lagrange particle tracking algorithm.

[0005] In some optional embodiments, the tracer bubble generating unit generates helium bubbles, the bubble release direction of the bubble release tube is consistent with the airflow direction, and the arrangement of the bubble release tube does not interfere with the flow field.

[0006] In some optional implementations, each camera of the multi-camera image acquisition unit maintains a preset distance from the wind tunnel wall, and each camera is installed at a different height to form a multi-view shooting layout, ensuring that the tracer bubble in the measurement area is within the field of view of at least two cameras.

[0007] In some alternative implementations, the surface light source of the lighting unit is an LED light source, the brightness of which is adjustable and flicker-free.

[0008] In some alternative implementations, the synchronization trigger control unit is located outside the wind tunnel and connected to each camera via control lines to ensure that all cameras start shooting synchronously, while controlling the frequency and number of shots taken by the cameras.

[0009] In some optional embodiments, the light-absorbing material layer is a black non-reflective velvet cloth to avoid interference from the collection of particles caused by reflections generated by the wind tunnel platform; the black non-reflective velvet cloth is adsorbed and fixed to the wind tunnel wall by magnetic connectors, which is firm and easy to install and remove.

[0010] In some optional embodiments, the gas source is a helium cylinder, which is connected to the control console via a high-pressure gas pipe. The control console is connected to an air compressor and finally to the bubble release pipe via a pipeline. The control console adjusts the bubble size and spatial distribution density by controlling the pressure of helium and air, the amount of bubble liquid, and the content and ratio of each component.

[0011] In some optional implementations, the tracer bubble generating unit, the multi-camera image acquisition unit, the illumination unit, and the synchronous trigger control unit are all independent modular components, and the position and number of each module can be adjusted according to the wind tunnel size and measurement requirements.

[0012] In some alternative implementations, the data processing terminal is placed outside the wind tunnel and connected to various measuring devices inside the wind tunnel via data cables to achieve centralized control and data processing.

[0013] In some alternative implementations, all device components are arranged outside the wind tunnel or in a location that avoids interfering with airflow, in order to achieve non-invasive measurement of the flow field.

[0014] In some alternative implementations, all device components are arranged outside the wind tunnel or in a location that avoids interfering with airflow, in order to achieve non-invasive measurement of the flow field.

[0015] One embodiment of this specification can achieve at least the following beneficial effects: 1. In the non-contact velocity and manifold measurement device for wind tunnel flow fields provided in this embodiment of the invention, the bubble release tube of the tracer bubble generating unit is close to the fan and does not intervene in the flow field. The digital camera of the multi-camera image acquisition unit is arranged outside the wind tunnel and covers the target measurement area through a multi-angle design. The surface light source of the illumination unit is specifically arranged above the measurement area. This design of independent components and precise arrangement allows the device to adapt to measurement scenarios in wind tunnels of different sizes. The installation parameters of each component can be adjusted according to the position and range of the measurement area inside the wind tunnel without making significant changes to the overall structure of the device, effectively improving the adaptability and flexibility of the device to different wind tunnel experimental needs.

[0016] 2. In the wind tunnel flow field non-contact velocity and manifold measurement device provided in the embodiments of the present invention, the synchronous trigger control unit is connected to the digital camera and the data processing terminal by means of hard triggering, which can ensure that multiple cameras start shooting synchronously and avoid deviation in the recording of tracer bubble trajectory due to shooting time difference.

[0017] 3. In the non-contact velocity and manifold measurement device for wind tunnel flow fields provided in this embodiment of the invention, the light-absorbing material layer in the measurement area of ​​the wind tunnel inner wall is fixed in a removable manner, facilitating replacement or cleaning based on wear and tear. Simultaneously, components such as the multi-camera image acquisition unit and the synchronous trigger control unit are all located outside the wind tunnel, allowing for installation, debugging, and maintenance without needing to penetrate the wind tunnel interior. This design makes daily maintenance, component replacement, and periodic inspections more convenient, reducing maintenance difficulty and time costs. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is used to illustrate the overall architecture and workflow of the velocity and manifold measurement device in the technical solution of this application; Figure 2 A schematic diagram of the overall structure of the non-contact velocity and manifold measurement device for wind tunnel flow fields provided in an embodiment of the present invention; Figure 3 This is used to illustrate two types of illumination in optical measurement: back illumination and front illumination. Figure 4 for Figure 2A cross-sectional schematic diagram of camera arrangement in a real-world scenario within the provided non-contact velocity and manifold measurement device for wind tunnel flow fields; Figure 5 This is a schematic diagram of the control console in the tracer bubble generating unit. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] Before introducing the technical solution of this application, let's first discuss... Figure 1 A brief description of the design logic of the technical solution in this application is provided, such as... Figure 1 As shown, Figure 1 The diagram illustrates the components and interaction logic of the flow velocity and manifold measurement device. Figure 1 The measurement object is a target (such as the wind tunnel flow field tracer bubble in this application). First, the optical information of the target is collected by the optical module (corresponding to the multi-camera image acquisition unit and illumination unit in this application). Then, the electromechanical control module (corresponding to the synchronous trigger control unit in this application) realizes the operation control of the equipment, thereby ensuring the synchronization of optical acquisition. Subsequently, the acquired data is transmitted to the software algorithm module (corresponding to the data processing terminal and Lagrange particle tracking algorithm in this application) for analysis and processing, and finally outputs the measurement results such as the flow field velocity distribution.

[0024] This application provides a non-contact flow velocity and manifold measurement device for wind tunnel flow fields. The structure of the device is described below with reference to the accompanying drawings. Figure 2 As shown, Figure 2 This is a schematic diagram of the overall structure of a non-contact flow velocity and manifold measurement device for wind tunnel flow fields provided in an embodiment of the present invention. The device may include: The tracer bubble generating unit includes a control console, a gas source, a bubble liquid supply component, and a bubble release pipe. The control console is connected to the gas source and the bubble liquid supply component and is used to control the pressure, content, and ratio of helium, air, and bubble liquid to achieve the release of the required tracer bubbles. The bubble release pipe is set close to the fan and located in the middle of each row of fans without interfering with the flow field. A multi-camera image acquisition unit, comprising at least three digital cameras arranged outside the wind tunnel, with each camera having a different position, height, and shooting angle, collectively covering the target measurement area inside the wind tunnel; The lighting unit includes multiple surface light sources, which are arranged at the top of the wind tunnel and above the measurement area, providing illumination to the measurement area using a frontal lighting method. A synchronous trigger control unit is connected to the digital camera and the data processing terminal respectively via control lines, and uses a hard triggering method to realize the synchronous triggering of multiple cameras; A data processing terminal is connected to the multi-camera image acquisition unit via a data cable to receive and process the acquired image data. The data processing terminal is configured to execute the Lagrange particle tracking algorithm. The measurement area on the inner wall of the wind tunnel is provided with a light-absorbing material layer, which is removably fixed to the wind tunnel wall.

[0025] The following is combined with Figure 3 Please explain the meaning of the term "front lighting" mentioned above, such as... Figure 3 As shown, Figure 3 Two illumination methods used to illustrate optical measurement are backlighting and front lighting. Illumination method represents the relative relationship between the camera, light source, and object. They are categorized into front lighting and back lighting based on whether the light source and camera are on the same side. In back lighting, the light source and camera are on opposite sides of the target. In front lighting, the light source and camera are on the same side relative to the target. For example... Figure 4As shown. The main advantage of backlit imaging is lower background noise and clearer image quality. However, its use is significantly limited, primarily requiring no obstructions between the light source, the target, and the camera in the imaging optical path. During imaging, because the target blocks the light, the image of the target is darker than the background. In other words, the background is brighter and the target is darker.

[0026] Since the technical solution of this application requires measuring the performance of airflow in a wind tunnel or around a building, a building model must be placed on the imaging optical path on the bottom surface. At the same time, various road surface environments must be simulated. It is impossible to use completely smooth and transparent materials. Therefore, backlighting is not suitable for the technical solution of this application. Thus, this application adopts front lighting. Since the target reflects the light source into the camera, the grayscale of the target image is brighter than the background, that is, the background is dark and the target is bright.

[0027] It should be noted that, in each experiment, the technical solution of this application can generate a tracer bubble field with a specific particle size range and a predetermined spatial distribution density in real time by accurately controlling the supply pressure, mixing ratio, flow rate, and composition of the helium and air, according to specific measurement requirements. The bubble particle size can be stably controlled through gas-liquid mixing and shearing processes to ensure suitable optical characteristics and flow tracking performance. The spatial distribution density refers to the number of tracer bubbles per unit flow field volume. This density can be flexibly adjusted according to the wind tunnel velocity, the volume of the measurement area, and the required data resolution. This provides sufficient, uniform, and spatiotemporally complete tracer particles for subsequent Lagrange particle tracking algorithms based on multi-view image sequences, while avoiding particle overlap and tracking loss.

[0028] The following describes the working steps of the optical measurement device. First, experimental preparation is carried out by placing a layer of black non-reflective velvet as a light-absorbing material on the wall of the wind tunnel measurement area to form a dark background. At least three digital cameras are placed outside the wind tunnel, ensuring that their positions, heights, and shooting angles are different, so as to cover the target measurement area together. At the same time, an LED surface light source is installed above the measurement area at the top of the wind tunnel, using a front illumination method.

[0029] Next, the measurement system is activated, namely, the tracer bubble generation unit is turned on, and helium bubbles are released as tracer bubbles into the air inlet side of the wind tunnel measurement section through a bubble release pipe that is close to the fan and does not interfere with the flow field; at the same time, the fan is started to generate the required flow field. The data processing terminal issues a command through the synchronous trigger control unit (trigger box) to synchronously trigger all cameras to start continuous shooting in a hard triggering mode, capturing the motion image of the illuminated tracer bubble against a dark background.

[0030] Finally, data processing is performed. The image data captured by the camera is transmitted to the data processing terminal via a data cable. The terminal executes the Lagrange particle tracking algorithm to perform bubble recognition, 3D trajectory reconstruction, and velocity field calculation on the multi-view images, and finally obtains the airflow trajectory and wind speed distribution.

[0031] In the non-contact velocity and manifold measurement device for wind tunnel flow fields provided in this embodiment of the invention, the bubble release tube of the tracer bubble generating unit is close to the fan and does not intervene in the flow field. The digital camera of the multi-camera image acquisition unit is arranged outside the wind tunnel and covers the target measurement area through a multi-angle design. The surface light source of the illumination unit is specifically arranged above the measurement area. This independent component and precise arrangement design allows the device to adapt to measurement scenarios in wind tunnels of different sizes. The installation parameters of each component can be adjusted according to the position and range of the measurement area inside the wind tunnel without making significant modifications to the overall structure of the device, effectively improving the adaptability and flexibility of the device to different wind tunnel experimental requirements. Furthermore, in the non-contact velocity and manifold measurement device for wind tunnel flow fields provided in this embodiment of the invention, the synchronous trigger control unit uses a hard trigger method to connect the digital camera and the data processing terminal, ensuring that multiple cameras start shooting synchronously and avoiding deviations in tracer bubble trajectory recording caused by shooting time differences. Simultaneously, the bubble release tube of the tracer bubble generating unit does not intervene in the flow field, thus avoiding interference from the components to the wind field. In the non-contact velocity and manifold measurement device for wind tunnel flow fields provided in this invention, the light-absorbing material layer in the measurement area of ​​the wind tunnel inner wall is fixed in a removable manner, facilitating replacement or cleaning based on wear and tear. Meanwhile, components such as the multi-camera image acquisition unit and the synchronous trigger control unit are all located outside the wind tunnel, allowing for installation, debugging, and maintenance without needing to penetrate the wind tunnel interior. This design makes routine maintenance, component replacement, and periodic inspections more convenient, reducing maintenance difficulty and time costs.

[0032] Based on the technical solutions described above, this specification also provides some specific implementation schemes, which are described below.

[0033] In an optional embodiment, the tracer bubble generated by the tracer bubble generating unit can be a helium bubble, the bubble release direction of the bubble release tube is consistent with the airflow direction, and the arrangement of the bubble release tube does not interfere with the flow field.

[0034] In this embodiment, the tracer bubble generating unit produces helium bubbles, specifically using a helium cylinder as the gas source. A high-pressure gas pipe connects the helium to the bubble release pipe, which is equipped with a pressure regulating valve to adjust the helium output pressure. The bubble release pipe is positioned close to the fan, in the middle of each fan row, and does not interfere with the flow field. Its bubble release direction is completely aligned with the airflow direction, allowing the generated helium bubbles to flow naturally with the airflow and preventing particle accumulation or deviation from the measurement area due to the inconsistent release direction with the airflow.

[0035] Helium bubbles, with diameters ranging from 1 to 3 mm, exhibit neutral buoyancy and an average lifespan of 2 minutes. The tracer bubble generating unit can adjust particle density and diameter by controlling the helium pressure and the amount of foaming solution to suit different experimental needs. For example, when measuring high-velocity flow fields, the helium pressure can be increased and the foaming solution concentration adjusted to enhance particle density, ensuring sufficient tracer bubbles for camera capture. Conversely, at lower flow velocities, the helium pressure and foaming solution concentration can be appropriately reduced to prevent excessive particle density from affecting recognition accuracy.

[0036] Because the helium bubbles are released in the same direction as the airflow and possess neutral buoyancy, they can uniformly enter the wind tunnel measurement area (such as the area surrounding a simulated building) with the airflow. This provides the multi-camera image acquisition unit with clear and continuous tracer bubble trajectories, ensuring the accuracy of subsequent data processing such as flow field velocity calculations. Furthermore, the arrangement of the bubble release pipes without intervening in the flow field avoids interference with the original flow field of the wind tunnel.

[0037] In an optional embodiment, each camera of the multi-camera image acquisition unit maintains a preset distance from the wind tunnel wall, and each camera is installed at a different height to form a multi-view shooting layout, ensuring that the tracer bubble in the measurement area is within the field of view of at least two cameras.

[0038] In this embodiment, the multi-camera image acquisition unit includes at least three digital cameras, each arranged outside the wind tunnel. In specific implementation, one camera can be set on the outside of the left side of the wind tunnel, maintaining a preset distance from the wind tunnel wall, and installed at a low height. The other two cameras can be set on the outside of the right side of the wind tunnel, maintaining a preset distance from the wind tunnel wall, and installed at different heights, with one camera installed at a relatively low height and the other at a relatively high height.

[0039] like Figure 4 As shown, Figure 4 for Figure 2 A schematic cross-sectional view of a camera arrangement in a real-world scenario within a provided non-contact wind tunnel flow field velocity and manifold measurement device. Figure 4As can be seen from the shooting angles, the left camera is at a 25° angle to the bottom plane of the wind tunnel, while one of the two cameras on the right is at a 25° angle and the other at a 40° angle. This arrangement creates a multi-view shooting layout, with the fields of view of each camera overlapping within the measurement area inside the wind tunnel, assuming the area surrounding a simulated building. When tracer bubbles are present within the measurement area, each tracer bubble will be within the field of view of at least two cameras simultaneously. For example, a tracer bubble near a simulated building will be captured simultaneously by the camera on the left at a 25° angle and the camera on the right at either a 25° or 40° angle. This provides spatially correlated image data support for subsequent data processing steps such as tracer bubble trajectory tracking and flow velocity calculation based on multi-view images, ensuring the accuracy and reliability of the measurement results. Simultaneously, the light source at the top of the wind tunnel illuminates the fields of view of each camera, ensuring the accuracy of tracer bubble recognition in the images.

[0040] In an optional embodiment, the surface light source of the lighting unit can be an LED light source, and the brightness of the LED light source is adjustable and flicker-free.

[0041] In this embodiment, the surface light source of the illumination unit uses an adjustable-brightness, flicker-free LED light source, which meets the requirement of flexible control of illumination intensity in this application, adapting to different particle densities and camera shooting parameters, thereby ensuring optimal contrast and clarity in the tracer bubble image. Meanwhile, considering the periodic brightness fluctuations of traditional AC-driven light sources, which can cause asynchrony with the short exposure of high-speed cameras, resulting in brightness jitter, stripe noise, or even trajectory breaks in the acquired particle image sequence, this introduces errors into the Lagrange particle tracking algorithm that relies on continuous images for recognition and matching. The flicker-free LED light source used in this embodiment provides highly stable illumination output over time, with its luminous intensity remaining constant at each microsecond-level camera exposure. This works in conjunction with the time reference provided by the aforementioned synchronous trigger control unit, thereby eliminating image quality problems caused by unstable illumination. If a digital camera is used, stripes, flickering, and uneven brightness will occur during shooting, affecting image quality and interfering with particle acquisition and calculation.

[0042] In an optional embodiment, the synchronous trigger control unit is located outside the wind tunnel and is connected to each camera via control lines to ensure that all cameras start shooting synchronously, while controlling the frequency and number of shots taken by the cameras.

[0043] In this embodiment, the synchronous trigger control unit can be a trigger box, which is located outside the wind tunnel. For example, it can be installed near the test control console next to the wind tunnel, so that operators can connect and debug it nearby. It is also far away from the area affected by the wind tunnel airflow, thereby avoiding interference from the ambient airflow on the signal transmission of the control unit.

[0044] In terms of connectivity, the trigger box is connected to each digital camera in the multi-camera image acquisition unit via multiple control lines. One end of each control line is connected to the trigger interface of the camera, and the other end is connected to the signal output port of the trigger box, forming a one-to-one signal transmission path, thus ensuring that each camera can independently receive the trigger signal. Simultaneously, the trigger box can also be connected to the signal interface of the data processing terminal via a single control line. This connection method enables bidirectional signal interaction between the trigger box and the data processing terminal, allowing it to both receive control commands from the data processing terminal and send trigger status information back to the data processing terminal.

[0045] In actual experimental operation, the synchronous triggering process is as follows: First, the operator sets the trigger parameters on the data processing terminal using dedicated control software. Adjustable parameters include the camera's shooting frequency and the number of shooting pulses. The shooting frequency refers to the number of times the camera takes pictures per unit time, used to adapt to the measurement needs of different flow velocities. For example, in a high-velocity flow field, the shooting frequency needs to be increased to capture the rapid trajectory of particles. The number of shooting pulses refers to the number of images continuously captured after a single triggering of the camera. The specific value can be determined according to the required flow field observation duration for the experiment. After the parameters are set, the operator issues a "start triggering" command through the software. This command is transmitted to the trigger box via the control line. Upon receiving the command, the trigger box immediately generates a synchronous trigger signal and sends this signal to all cameras simultaneously via the control lines connecting each camera. Each camera starts shooting synchronously the instant it receives the trigger signal, thus ensuring that all cameras start acquiring images at the same time without any time difference.

[0046] The synchronous triggering method in this embodiment ensures that each set of images acquired by multiple cameras corresponds strictly in time. That is, images captured by different cameras at the same time record the same motion state of the tracer bubble within the measurement area. This provides a time-consistent image data foundation for subsequent data processing stages such as multi-view image matching, particle trajectory tracking, and flow field velocity calculation. Specifically, multi-view image matching refers to locating the spatial coordinates of the same tracer bubble using images from different cameras at the same time; particle trajectory tracking reconstructs the particle motion path based on continuous synchronous images; and flow field velocity calculation derives the flow velocity based on particle displacement and time intervals. The technical solution in this embodiment effectively avoids particle position matching deviations caused by asynchronous camera startup, thereby ensuring the accuracy of the flow field measurement results.

[0047] In an optional embodiment, the light-absorbing material layer can be a black non-reflective velvet cloth to avoid interference from the collection of particles caused by reflections generated by the wind tunnel platform; the black non-reflective velvet cloth is adsorbed and fixed to the wind tunnel wall by magnetic connectors, which is firm and easy to install and disassemble.

[0048] In this embodiment, the light-absorbing material layer preferably uses black non-reflective velvet to avoid interference from reflections from the wind tunnel walls. This velvet can be fixed using magnetic connectors. During setup, the black non-reflective velvet is placed over the wall of the model placement area (i.e., the target measurement area). Its black, non-reflective properties maximize the absorption of light emitted by the illumination unit, preventing reflections from the wind tunnel walls and creating a clean, dark background in the image. Against this background, the illuminated tracer bubble (helium bubble) stands out prominently, creating a very high contrast with the background.

[0049] In this embodiment, the method of fixing the fabric with black magnets facilitates the convenient arrangement and removal of the felt cloth, allowing researchers to quickly adjust the background area or perform maintenance and replacement according to different experimental needs. Specifically, the black non-reflective felt cloth primarily covers the target measurement area in the middle section of the wind tunnel, while the original observation section remains at the front. This ensures both the high-contrast dark background required for optical measurements and maintains the overall visibility of the wind tunnel, facilitating direct observation of the flow field or other types of image recording by researchers. This modular background arrangement improves the utilization efficiency of the wind tunnel. When conducting flow field display experiments that do not rely on a dark background, such as the smoke line method, the felt cloth can be removed at any time, allowing for rapid switching of experimental configurations without any modifications to the wind tunnel itself, thus effectively supporting the continuous execution of multiple types of experiments.

[0050] In an optional embodiment, the gas source can be a helium cylinder, which can be connected to a control console via a high-pressure gas pipe. The control console is also connected to an air compressor and finally connected to a bubble release pipe via a pipeline. The control console adjusts the bubble size and spatial distribution density by controlling the pressure of helium and air, the amount of bubble liquid, and the content ratio of each component.

[0051] In this embodiment, the gas source subunit of the tracer bubble generating unit consists of a helium tank and an air compressor, both connected to the core control console via pipelines. The helium tank provides the main gas for generating tracer bubbles, while the compressed air provided by the air compressor serves as an auxiliary gas source. The control console acts as a central control unit, coordinating and controlling the pressure of the helium, the pressure of the compressed air, the supply of the bubble liquid, and the proportions of each component to accurately adjust the particle size and spatial distribution density of the final released helium bubbles.

[0052] In this embodiment, compressed air drives the bubble liquid during bubble generation, using air pressure to push the bubble film solution to a region where it is fully mixed with helium. Without this force, the bubble liquid would not form effectively and might splash. Secondly, as the compressed air flows through a special filter inside the control console, it forms a high-speed rotating cyclone. This cyclone strongly shears and disturbs the mixed gas-liquid two-phase flow, separating the bubbles and preventing them from agglomerating. Then, the kinetic energy carried by the cyclone directly pushes the initially formed and separated individual bubbles out of the generator and releases them into the flow field, completing the final release action. Finally, the air pressure directly determines the bubble size. Higher pressure results in a higher frequency of cutting the bubble liquid, producing smaller and denser bubbles; conversely, lower pressure produces larger bubbles.

[0053] Ultimately, this embodiment's technical solution, through the coordinated control of helium pressure, air pressure, and the amount of bubble solution, can stably control the diameter of the generated helium bubbles within a specific range of 1-3 mm, maintaining good neutral buoyancy characteristics and an average lifespan of approximately 2 minutes. This composite gas source and control system allows the device to flexibly adapt to different wind tunnel test scenarios from low to high flow rates, ensuring sufficient and clear tracer bubbles in the flow field for capture while maximizing the preservation of the original wind tunnel flow field from measurement interference.

[0054] The following is combined with Figure 5 The console mentioned above will be explained, such as... Figure 5 As shown, Figure 5This is a schematic diagram of the control console in the tracer bubble generation unit. Its surface is marked with "He," "AIR," and "BFS," corresponding to the input interfaces for helium, air, and bubble solution, respectively. It also includes a pressure and content adjustment module for accurately controlling the input helium pressure, air pressure, and bubble solution content. A helium tank is connected to the left side of the control console, which is sealed to the console's helium input interface via a pipeline. This provides neutral buoyancy gas to the tracer bubbles (helium bubbles), ensuring they can flow naturally with the wind tunnel flow. The control console is also connected to an air compressor. Air is input to the control console via the corresponding AIR interface. A vortex filter is connected above the control console. This filter uses the input air to create a high-speed rotating vortex, which can separate adhering bubble clusters and smoothly push the processed individual bubbles to subsequent components. The other end of the vortex filter is connected to a bubble release pipe for stably releasing the processed tracer bubbles into the wind tunnel flow field.

[0055] In the optional embodiment, the tracer bubble generating unit, the multi-camera image acquisition unit, the illumination unit, and the synchronous trigger control unit are all independent modular components, and the position and quantity of each module can be adjusted according to the wind tunnel size and measurement requirements.

[0056] In this embodiment, the tracer bubble generating unit, the multi-camera image acquisition unit, the illumination unit, and the synchronous trigger control unit are all independent modular components. The core functional components of each component are integrated into one unit and have independent installation and disassembly capabilities.

[0057] In an optional embodiment, the data processing terminal is placed outside the wind tunnel and connected to various measuring devices inside the wind tunnel via data cables to achieve centralized control and data processing.

[0058] In this embodiment, the data processing terminal is placed on a control panel outside the wind tunnel. This terminal can establish a communication connection with the multi-camera image acquisition unit inside the wind tunnel via a data cable, specifically a USB 3.0 data interface, to receive and process the acquired image data. The terminal runs dedicated software integrating image acquisition, bubble recognition, trajectory tracking, and velocity calculation functions. It processes the received synchronous image sequence by executing a Lagrange particle tracking algorithm. The specific process may include particle recognition and matching, three-dimensional coordinate calculation, thereby ultimately obtaining the three-dimensional coordinate flow trajectory of the particle motion, measuring the particle velocity, and thus achieving centralized control and automation of the entire measurement process.

[0059] In the optional embodiments, all device components are arranged outside the wind tunnel or in a location that avoids interfering with airflow.

[0060] In this embodiment, all components of the non-contact velocity and manifold measurement device for wind tunnel flow fields are arranged to ensure that they do not interfere with the airflow within the wind tunnel, thereby achieving non-invasive measurement.

[0061] Specifically, the tracer bubble generating unit, multi-camera image acquisition unit, illumination unit, synchronous trigger control unit, and data processing terminal are all located outside the wind tunnel platform. Each digital camera in the multi-camera image acquisition unit is positioned outside the wind tunnel, with its lens adjusted to point towards the measurement area inside the wind tunnel, eliminating the need for the camera to enter the wind tunnel flow field. The LED surface light source of the illumination unit is also installed on the outer top of the wind tunnel, using frontal illumination to project light onto the measurement area from the outside. The synchronous trigger control unit and data processing terminal, serving as the control and processing core, are also located outside the wind tunnel and connected to the internal components via cables.

[0062] By externalizing all measurement device components, the entire measurement process in this application can be completed without introducing any foreign object interference, thus reflecting the true state of the original flow field inside the wind tunnel.

[0063] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A non-contact flow velocity and manifold measurement device for wind tunnel flow fields, characterized in that, include: The tracer bubble generating unit includes a control console, a gas source, a bubble liquid supply component, and a bubble release tube. The control console is connected to the gas source and the bubble liquid supply component and is used to control the pressure, content, and ratio of helium, air, and bubble liquid to achieve the release of the required tracer bubbles. The bubble release tube is set close to the fan and located in the middle of each row of fans without interfering with the flow field. A multi-camera image acquisition unit, comprising at least three digital cameras arranged outside the wind tunnel, with each camera having a different position, height, and shooting angle, collectively covering the target measurement area inside the wind tunnel; The lighting unit includes multiple surface light sources, which are arranged at the top of the wind tunnel and above the measurement area, providing illumination to the measurement area using frontal lighting. The measurement area on the inner wall of the wind tunnel is provided with a light-absorbing material layer, which is removably fixed to the wind tunnel wall. A synchronization trigger control unit is provided, which is connected to the digital camera and the data processing terminal respectively via control lines. It adopts a hard triggering method to realize the synchronization triggering of multiple cameras. The data processing terminal is connected to the multi-camera image acquisition unit via a data cable and is used to receive and process the acquired image data. The data processing terminal is configured to execute the Lagrange particle tracking algorithm.

2. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, The tracer bubble generated by the tracer bubble generating unit is a helium bubble. The bubble release direction of the bubble release tube is consistent with the airflow direction, and the arrangement of the bubble release tube does not interfere with the flow field.

3. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, Each camera in the multi-camera image acquisition unit maintains a preset distance from the wind tunnel wall, and each camera is installed at a different height, forming a multi-view shooting layout to ensure that the tracer bubble in the measurement area is within the field of view of at least two cameras.

4. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, The surface light source of the lighting unit is an LED light source, and the brightness of the LED light source is adjustable and flicker-free.

5. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, The synchronous trigger control unit is located outside the wind tunnel and is connected to each camera via control lines to ensure that all cameras start shooting synchronously, while controlling the frequency and number of shots taken by the cameras.

6. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, The light-absorbing material layer is a black non-reflective velvet cloth, which avoids the interference of reflections generated by the wind tunnel platform with particle collection; the black non-reflective velvet cloth is adsorbed and fixed to the wind tunnel wall by magnetic connectors, which is firm and easy to install and remove.

7. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, The gas source is a helium cylinder, which is connected to the control console via a high-pressure gas pipe. The control console is connected to an air compressor and finally to the bubble release pipe via a pipeline. The control console adjusts the bubble size and spatial distribution density by controlling the pressure of helium and air, the amount of bubble liquid, and the content and ratio of each component.

8. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, The tracer bubble generating unit, multi-camera image acquisition unit, illumination unit, and synchronous trigger control unit are all independent modular components, and the position and number of each module can be adjusted according to the wind tunnel size and measurement requirements.

9. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, The data processing terminal is placed outside the wind tunnel and connected to various measuring devices inside the wind tunnel via data cables to achieve centralized control and data processing.

10. The non-contact velocity and manifold measurement device for wind tunnel flow fields according to claim 1, characterized in that, All equipment components are located outside the wind tunnel or in a location that avoids interfering with airflow, enabling non-invasive measurement of the flow field.

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