Method, system and device for generating a two-dimensional lagrangian velocity field

Abstract

The disclosure provides a two-dimensional Lagrangian velocity field generation method, system and device, which can be applied to the technical field of fluid mechanics. The two-dimensional Lagrangian velocity field generation method comprises: acquiring a molecular marker displacement image, wherein the molecular marker displacement image comprises images of light emission lines generated by tracer molecules in a flow field collected at different times; respectively performing discrete processing on a plurality of light emission line images in the molecular marker displacement image to obtain pixel horizontal coordinates and pixel vertical coordinates of each feature point in each light emission line image; according to the pixel horizontal coordinates and the pixel vertical coordinates of a plurality of groups of feature points in any two adjacent light emission line images in the molecular marker displacement image, the instantaneous velocity at the target position corresponding to each group of feature points is calculated; and based on the instantaneous velocities at the target positions corresponding to the plurality of groups of feature points in the molecular marker displacement image, a two-dimensional Lagrangian velocity field corresponding to the tracer molecules is generated.

Description

Technical Field

[0001] This disclosure relates to the field of fluid mechanics, and in particular to a method, system and apparatus for generating a two-dimensional Lagrangian velocity field. Background Technology

[0002] Velocity, as a core parameter of flow fields, plays a crucial role in understanding the complex fluid-transport processes within them. Its quantitative measurement is of decisive significance for optimization design, fluid mechanics parameterization research, and engineering applications. In particular, with the rapid development of aerospace technology, the demand for improved performance of supersonic vehicles is becoming increasingly urgent, making the accurate velocity measurement of high-speed, supersonic flow fields a critical problem that urgently needs to be solved.

[0003] In existing technologies, molecular tagging velocimetry (MTV) techniques, represented by femtosecond laser electronic excitation tagging (FLEET) and femtosecond laser induced cyano chemiluminescence (FLICC), have further improved the accuracy of velocimetry. However, because these techniques acquire linear fluorescence signals, they cannot directly obtain two-dimensional velocity information and can only obtain a one-dimensional velocity field. Summary of the Invention

[0004] In view of the above problems, this disclosure provides a method, system and apparatus for generating a two-dimensional Lagrange velocity field.

[0005] According to a first aspect of this disclosure, a method for generating a two-dimensional Lagrange velocity field is provided, comprising:

[0006] Acquire molecular marker displacement images, wherein the molecular marker displacement images include images of the luminescent lines produced by tracer molecules in the flow field at different times;

[0007] The images of multiple luminescent lines in the above molecular marker displacement image are discretized to obtain the pixel abscissa and pixel ordinate of each representation point in each luminescent line image;

[0008] Based on the pixel abscissa and pixel ordinate of multiple sets of characterization points in any two adjacent luminescent line images in the above molecular marker displacement image, the instantaneous velocity at the target position corresponding to each set of characterization points is calculated. Here, a set of characterization points includes two characterization points in the above two adjacent luminescent line images that are located at the same proportional position in the horizontal direction.

[0009] Based on the instantaneous velocities at the target positions corresponding to multiple sets of characterization points in the aforementioned molecular marker displacement image, a two-dimensional Lagrange velocity field corresponding to the aforementioned tracer molecule is generated.

[0010] According to embodiments of this disclosure, the above-mentioned discretization processing of multiple luminescent line images in the molecular marker shift image to obtain the pixel abscissa and pixel ordinate of each representation point in each luminescent line image includes:

[0011] For each luminescent line image in the aforementioned molecular marker shift image,

[0012] Based on the first preset signal strength threshold, edge detection is performed on the above-mentioned luminous line image in the horizontal direction to determine the pixel horizontal coordinates and scale coordinates at both ends of the above-mentioned luminous line image in the horizontal direction.

[0013] The average value of two adjacent scale coordinates is calculated through multiple iterations to determine the pixel abscissa and scale coordinate of each representation point in the above luminous line image;

[0014] For the pixel abscissa of each representation point in the above-mentioned luminous line image, based on the second preset signal intensity threshold, edge detection is performed on the above-mentioned luminous line image in the vertical direction to determine the upper and lower boundaries of the above-mentioned luminous line image at the pixel abscissa of each representation point.

[0015] Based on the upper and lower boundary pixel coordinates of the above-mentioned luminous line image at each representation point, the pixel coordinates of each representation point in the above-mentioned luminous line image are determined.

[0016] According to embodiments of this disclosure, the method for generating the two-dimensional Lagrange velocity field further includes:

[0017] Based on the proportional coordinates of each characterization point in any two adjacent luminescent line images in the aforementioned molecular marker shift image, multiple sets of characterization points with the same proportional coordinates in the aforementioned two adjacent luminescent line images are determined. Among them, a set of characterization points with the same proportional coordinates indicates that the two characterization points are located at the same proportional position in the aforementioned two adjacent luminescent line images.

[0018] According to embodiments of this disclosure, edge detection is performed on the luminous line image along the horizontal axis based on a first preset signal strength threshold to determine the pixel coordinates at both ends of the luminous line image along the horizontal axis, including:

[0019] Determine the pixel coordinates of multiple points in the molecular marker displacement image whose signal intensity is greater than the first preset signal intensity;

[0020] The maximum and minimum x-coordinates among the pixel coordinates of the above multiple points are determined as the pixel x-coordinates at both ends of the above luminous line image in the horizontal direction.

[0021] According to embodiments of this disclosure, the calculation of the instantaneous velocity at the target position corresponding to each set of characterization points based on the pixel abscissa and ordinate of multiple sets of characterization points in the images of any two adjacent luminescent lines in the molecular marker displacement image includes:

[0022] For each set of representation points in the above two adjacent luminous line images,

[0023] Based on the pixel abscissas of the first and second characterization points in the two adjacent luminous line images, the displacement of the second characterization point relative to the first characterization point in the horizontal axis direction is determined, wherein the first characterization point and the second characterization point are any set of characterization points in the two adjacent luminous line images.

[0024] Based on the pixel ordinates of the first and second characterization points, the displacement of the second characterization point relative to the first characterization point in the vertical direction is determined.

[0025] Based on the displacement of the second characterization point relative to the first characterization point in the horizontal direction and the displacement in the vertical direction, as well as the acquisition time interval between the two adjacent luminous line images, the instantaneous velocity at the target position is calculated, wherein the target position represents the intermediate position between the first characterization point and the second characterization point.

[0026] According to embodiments of this disclosure, before discretizing the molecular marker displacement image, the method for generating the two-dimensional Lagrange velocity field further includes:

[0027] Remove the background signal from the molecular marker shift image and extract the image of the region where the luminescent line image is located.

[0028] The second aspect of this disclosure provides a system for generating a two-dimensional Lagrange velocity field, applied to the aforementioned method for generating a two-dimensional Lagrange velocity field. The system includes:

[0029] Server, used for:

[0030] Acquire molecular marker displacement images, wherein the molecular marker displacement images include images of the luminescent lines produced by tracer molecules in the flow field at different times;

[0031] The multiple luminescent line images in the above molecular marker displacement image are discretized to obtain the pixel coordinates of each representation point in each luminescent line image;

[0032] Based on the pixel coordinates of multiple sets of characterization points in any two adjacent luminescent line images in the above molecular marker displacement image, the instantaneous velocity at the target position corresponding to each set of characterization points is calculated. Here, a set of characterization points includes two characterization points in the above two adjacent luminescent line images that are located at the same proportional position in the horizontal axis direction.

[0033] Based on the instantaneous velocities at the target positions corresponding to multiple sets of characterization points in the aforementioned molecular marker displacement image, a two-dimensional Lagrange velocity field corresponding to the aforementioned tracer molecule is generated.

[0034] According to embodiments of this disclosure, the above-described two-dimensional Lagrange velocity field generation system further includes: a femtosecond laser, a spherical mirror, and a nozzle;

[0035] The aforementioned femtosecond laser is used to emit laser light;

[0036] The aforementioned spherical mirror is used to focus the laser beam directly above the aforementioned nozzle;

[0037] The aforementioned nozzle is used to generate a flow field, and under the action of the aforementioned laser, the tracer molecules in the flow field generate luminescent lines.

[0038] According to embodiments of this disclosure, the above-described two-dimensional Lagrange velocity field generation system further includes: a signal enhancement camera and a digital signal generator;

[0039] The aforementioned digital signal generator is used to send an exposure signal to the signal enhancement camera a preset number of times at a preset time interval when receiving a pulse signal emitted by the aforementioned femtosecond laser, wherein the aforementioned femtosecond laser sends the aforementioned pulse signal to the aforementioned digital signal generator at the same time as emitting the laser.

[0040] The aforementioned signal enhancement camera is used to expose the luminescent lines generated by the tracer molecules in the aforementioned flow field each time the aforementioned exposure signal is received, and after the aforementioned preset number of exposures, to send the generated molecular marker displacement image to the aforementioned server.

[0041] A third aspect of this disclosure provides an apparatus for generating a two-dimensional Lagrange velocity field, comprising: an acquisition module, a processing module, a calculation module, and a generation module. The acquisition module acquires molecular marker displacement images, wherein the molecular marker displacement images include images of luminescent lines generated by tracer molecules in a flow field acquired at different times. The processing module discretizes multiple luminescent line images in the molecular marker displacement images to obtain the pixel abscissa and ordinate of each characterization point in each luminescent line image. The calculation module calculates the instantaneous velocity at a target position corresponding to each set of characterization points based on the pixel abscissa and ordinate of multiple sets of characterization points in any two adjacent luminescent line images in the molecular marker displacement images, wherein a set of characterization points includes two characterization points located at the same proportional position in the horizontal direction of the two adjacent luminescent line images. The generation module generates a two-dimensional Lagrange velocity field corresponding to the tracer molecules based on the instantaneous velocities at the target positions corresponding to the multiple sets of characterization points in the molecular marker displacement images.

[0042] A fourth aspect of this disclosure provides an electronic device comprising: one or more processors; and a memory for storing one or more computer programs, wherein the one or more processors execute the one or more computer programs to implement the steps of the method described above.

[0043] The fifth aspect of this disclosure also provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a processor, implement the steps of the above-described method.

[0044] A sixth aspect of this disclosure also provides a computer program product, including a computer program or instructions that, when executed by a processor, implement the steps of the above-described method.

[0045] According to the method, system, and apparatus for generating a two-dimensional Lagrangian velocity field provided in this disclosure, a molecular marker displacement image containing images of the luminescent lines generated by tracer molecules at different times is obtained by utilizing the position and length changes of the luminescent lines generated by tracer molecules at different times. Therefore, by discretizing multiple luminescent line images in the molecular marker displacement image, the pixel abscissa and ordinate of each representation point in the luminescent line image are obtained. Based on this, the two-dimensional instantaneous velocity at the target location is obtained based on the pixel abscissa and ordinate of two representation points located at the same proportional position in any two adjacent luminescent line images. This allows a two-dimensional Lagrangian velocity field to be generated based on the instantaneous velocities at all target locations in the molecular marker displacement image, overcoming the limitation of only obtaining a one-dimensional velocity field and realizing the inversion of the two-dimensional Lagrangian velocity field of the flow field. Attached Figure Description

[0046] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0047] Figure 1 The diagram illustrates an application scenario of a method for generating a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure.

[0048] Figure 2 A flowchart illustrating a method for generating a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure is shown schematically.

[0049] Figure 3 A schematic diagram of a molecular marker shift image according to an embodiment of the present disclosure is shown.

[0050] Figure 4 A flowchart illustrating the discretization process of an emitting line image according to an embodiment of the present disclosure is shown schematically.

[0051] Figure 5 A schematic diagram illustrating the scale coordinates of a characterizing point in an image of a luminescent line according to an embodiment of the present disclosure is shown.

[0052] Figure 6 A schematic diagram of a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure is shown.

[0053] Figure 7 A schematic diagram of a two-dimensional Lagrange velocity field generation system according to an embodiment of the present disclosure is shown.

[0054] Figure 8 A schematic diagram illustrating the structure of a two-dimensional Lagrange velocity field generation apparatus according to an embodiment of the present disclosure is shown; and

[0055] Figure 9 A block diagram schematically illustrates an electronic device suitable for implementing a method for generating a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure. Detailed Implementation

[0056] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0057] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0058] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0059] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0060] In the process of developing this disclosure, it was discovered that for high-speed, supersonic flow fields, traditional velocity measurement methods such as Pitot tubes and hot-wire anemometers are mature and inexpensive. However, the measurement process requires the probe to penetrate into the flow field being measured, which inevitably damages the original structure of the flow field. In addition, the high-speed airflow in the flow field also greatly increases the strength requirements of the probe material, increasing the cost and technical difficulty of the measuring instrument.

[0061] Since the invention of the laser, the emergence of optical diagnostic technology has opened the door to non-invasive velocimetry. Particle Image Velocimetry (PIV) is a typical example. Compared to traditional velocimetry techniques, PIV can perform high spatiotemporal resolution full-field flow measurement without intruding into the flow field, making it the most widely used technology in the field of velocimetry. However, PIV technology requires the addition of tracer particles to the flow field, which not only increases the complexity of the velocimetry system but also poses a challenge in selecting appropriate particle types and sizes to ensure their flow-following properties.

[0062] Molecular labeling velocimetry techniques, such as femtosecond laser electron excitation labeling and femtosecond laser-induced cyano chemiluminescence, overcome the aforementioned shortcomings of PIV and further improve the accuracy of velocimetry. However, both FLEET and FLICC essentially use the displacement of the emission line within a known time interval to measure velocity. Furthermore, since molecular labeling velocimetry obtains a linear fluorescence signal, it is impossible to directly obtain two-dimensional velocity information.

[0063] Therefore, embodiments of this disclosure provide a method for generating a two-dimensional Lagrange velocity field, enabling the inversion of the two-dimensional Lagrange velocity field of a flow field, especially a supersonic flow field.

[0064] Figure 1 The diagram illustrates an application scenario of a method for generating a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure.

[0065] like Figure 1 As shown, application scenario 100 according to this embodiment may include camera 101 and server 102.

[0066] Camera 101 is used to acquire images of the luminescent lines produced by tracer molecules in the flow field at different times to generate molecular marker displacement images.

[0067] Server 102 is used to acquire the molecular marker displacement image generated by camera 101, and to discretize the multiple emission line images in the molecular marker displacement image to obtain the pixel abscissa and ordinate of each characterization point in each emission line image. Based on the pixel abscissa and ordinate of multiple sets of characterization points in any two adjacent emission line images in the molecular marker displacement image, the instantaneous velocity at the target position corresponding to each set of characterization points is calculated. Based on the instantaneous velocity at the target position corresponding to the multiple sets of characterization points in the molecular marker displacement image, a two-dimensional Lagrangian velocity field corresponding to the tracer molecule is generated.

[0068] It should be noted that the method for generating a two-dimensional Lagrange velocity field provided in this embodiment can generally be executed by the server 102. Accordingly, the apparatus for generating a two-dimensional Lagrange velocity field provided in this embodiment can generally be located in the server 102.

[0069] The following will be based on Figure 1 The described scene, through Figures 2-6 The method for generating a two-dimensional Lagrange velocity field according to embodiments of this disclosure will be described in detail.

[0070] Figure 2 A flowchart illustrating a method for generating a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure is shown schematically.

[0071] like Figure 2 As shown, the method 200 includes operations S210 to S240.

[0072] In operation S210, a molecular marker shift image is acquired.

[0073] Among them, the molecular marker displacement image includes images of the luminescent lines produced by tracer molecules in the flow field at different times.

[0074] According to embodiments of this disclosure, molecular marker displacement images can be stored in the server as files. Thus, when a two-dimensional Lagrangian velocity field needs to be generated, the server can first obtain the molecular marker displacement images from the files.

[0075] Figure 3 A schematic diagram of a molecular marker shift image according to an embodiment of the present disclosure is shown.

[0076] like Figure 3 As shown, a molecular marker shift image may include multiple emission line images, such as emission line image A to emission line image I.

[0077] exist Figure 3 In the image, 2mm is the scale, indicating that the length of the segment in the image corresponds to 2mm in the actual flow field; 0~35000 refers to the range of signal strength, and its unit can be any unit au (arbitrary units).

[0078] In one embodiment, since the tracer molecules in the flow field move over time, the images of the luminescent lines generated by the tracer molecules collected at different times are located at different positions in the molecular marker displacement image.

[0079] For example, in Figure 3 In the process, as the tracer molecules move in the flow field, luminescent images A to I are acquired sequentially.

[0080] According to embodiments of this disclosure, the molecular marker shift image includes at least three emission line images, and the acquisition time interval between two adjacent emission line images in the molecular marker shift image is known.

[0081] In operation S220, the multiple luminescent line images in the molecular marker displacement image are discretized to obtain the pixel abscissa and ordinate of each representation point in each luminescent line image.

[0082] According to embodiments of this disclosure, generating a two-dimensional Lagrange velocity field requires velocities along both the horizontal and vertical axes. Furthermore, corresponding points on adjacent luminous line images are related, and the two-dimensional velocity can be calculated based on this relationship.

[0083] Therefore, the multiple emission line images in the molecular marker displacement image can be discretized separately to divide the emission line images into multiple representation points, and obtain the pixel abscissa and ordinate of each representation point in each emission line image. Based on this, it is beneficial to calculate the two-dimensional velocity based on the pixel abscissa and ordinate of representation points on two adjacent emission line images.

[0084] In operation S230, the instantaneous velocity at the target position corresponding to each set of characterization points is calculated based on the pixel abscissa and ordinate of multiple sets of characterization points in the images of any two adjacent luminescent lines in the molecular marker displacement image.

[0085] One set of characterization points includes two characterization points located at the same scale position in the horizontal direction of two adjacent luminous line images.

[0086] According to embodiments of this disclosure, the number of characterization points determined on each luminescent line image in the molecular marker shift image is the same, and the characterization points on the luminescent line image are all located at the corresponding proportional positions of the luminescent line image.

[0087] For example, five characterization points were identified on the luminescence line image, located sequentially at scale positions of -1, -1 / 2, 0, 1 / 2, and 1. Similarly, the characterization points for each luminescence line in the molecular marker shift image are located sequentially at scale positions of -1, -1 / 2, 0, 1 / 2, and 1.

[0088] Based on this, two representation points located at the same scale position in the horizontal direction on any two adjacent luminous line images can be a set of representation points. For example, two representation points located at scale position 1 on two adjacent luminous line images can be a set of representation points.

[0089] According to embodiments of this disclosure, since the tracer molecule moves in the flow field over time, the position and length of the emission line images it generates at different times will change. The representation point at the same proportional position on different emission line images can represent the position of the same point on the emission line images generated by the tracer molecule at different times. That is, for a certain representation point in one emission line image, it moves over time to the position of a representation point at the same proportional position in another emission line image.

[0090] Therefore, in order to calculate the two-dimensional velocity field, it is necessary to use the pixel abscissa and pixel ordinate of each set of characterization points on the two adjacent luminous line images to calculate the instantaneous velocity at the target position corresponding to each set of characterization points, where the instantaneous velocity is the two-dimensional velocity.

[0091] In operation S240, a two-dimensional Lagrangian velocity field corresponding to the tracer molecule is generated based on the instantaneous velocity at the target position corresponding to multiple sets of characterization points in the molecular marker displacement image.

[0092] According to embodiments of this disclosure, the instantaneous velocity at a target location corresponding to a set of characterization points in two adjacent luminescent line images in a molecular marker displacement image can be calculated based on the pixel abscissa and pixel ordinate of a set of characterization points.

[0093] Based on this, the instantaneous velocity at the corresponding target location is calculated using all representation points in all adjacent emission line images within the molecular marker displacement image. Thus, a two-dimensional Lagrangian velocity field corresponding to the tracer molecule can be generated based on the instantaneous velocities at all target locations in the molecular marker displacement image.

[0094] The two-dimensional Lagrangian velocity field is used to describe the trajectory and velocity changes of tracer molecules over a period of time as they move with the flow field.

[0095] According to embodiments of this disclosure, a molecular marker displacement image is obtained by utilizing the position and length changes of the emission lines generated by tracer molecules at different times. This image contains images of the emission lines generated by tracer molecules at different times. Therefore, by discretizing multiple emission line images in the molecular marker displacement image, the pixel abscissa and ordinate of each representation point in the emission line image are obtained. Based on this, the two-dimensional instantaneous velocity at the target location is obtained based on the pixel abscissa and ordinate of two representation points located at the same proportional position in any two adjacent emission line images. This allows a two-dimensional Lagrangian velocity field to be generated based on the instantaneous velocities at all target locations in the molecular marker displacement image, overcoming the limitation of only obtaining a one-dimensional velocity field and realizing the inversion of the two-dimensional Lagrangian velocity field of the flow field.

[0096] Figure 4 A flowchart illustrating the discretization process of a light-emitting line image according to an embodiment of the present disclosure is shown.

[0097] like Figure 4 As shown, the method 400 includes operations S410 to S440.

[0098] According to embodiments of this disclosure, operations S410 to S440 can be performed for each luminescent line image in a molecular marker shift image.

[0099] In operation S410, based on the first preset signal strength threshold, edge detection is performed on the luminous line image in the horizontal direction to determine the pixel horizontal coordinates and scale coordinates at both ends of the luminous line image in the horizontal direction.

[0100] According to embodiments of this disclosure, since it is necessary to invert the velocity field based on the molecular marker displacement image, the velocity field inversion requires the displacement increment of the luminescent line in order to invert the corresponding two-dimensional velocity.

[0101] Specifically, the position vector of the luminous line in the flow field can be expressed as the following formula (1).

[0102] (1)

[0103] in, This can be represented as the position of the tracer molecule along the X-axis. This can be represented as the position of the tracer molecule along the Y-axis. It can be represented as a unit vector in the X-axis direction. It can be represented as a unit vector symbol in the Y-axis direction; the X-axis direction is the horizontal axis direction, and the Y-axis direction is the vertical axis direction.

[0104] In time interval The displacement increment of the luminescent line produced by the tracer molecule can be expressed as the following formula (2).

[0105] (2)

[0106] in, , .

[0107] In time interval The average velocity of the light emitted by the tracer molecules can be the ratio of the displacement increment to the time interval, and the average velocity can be expressed by the following formula (3).

[0108] (3)

[0109] During the time interval At 0, the instantaneous velocity of the tracer molecule can be approximated by the average velocity, and the instantaneous velocity can be expressed by the following formula (4).

[0110] (4)

[0111] Based on the above, in order to obtain the instantaneous velocity, it is necessary to determine the displacement of the tracer molecule in the X-axis direction within a known time interval. and displacement in the Y-axis direction The displacements of the tracer molecules in the X-axis and Y-axis directions within a known time interval can be calculated based on the coordinates of the discretized images of two adjacent emission lines in the molecular marker displacement image.

[0112] Specifically, based on a first preset signal strength threshold, edge detection is first performed on the luminous line image in the horizontal direction to determine the pixel horizontal coordinates and scale coordinates at both ends of the luminous line image in the horizontal direction.

[0113] In one embodiment, the first preset signal strength threshold is a defined threshold set based on a certain percentage of the strongest signal in the luminous line image. The first preset signal strength threshold is set as needed. For example, 50% of the strongest signal in the luminous line image can be determined as the first preset signal strength threshold.

[0114] According to embodiments of this disclosure, the scale coordinates of the luminous line image at both ends in the horizontal direction can be set as needed. For example, the scale coordinates of the luminous line image at both ends in the horizontal direction can be set to -1 and 1, respectively.

[0115] In operation S420, the average value of two adjacent scale coordinates is calculated multiple times to determine the pixel abscissa and scale coordinate of each representation point in the luminous line image.

[0116] According to embodiments of this disclosure, based on the determined proportional coordinates at both ends of the luminous line image in the horizontal direction, the average value of two adjacent proportional coordinates can be calculated iteratively multiple times to determine the pixel horizontal coordinate and proportional coordinate of each representation point in the luminous line image.

[0117] The process involves iteratively calculating the average of two adjacent scale coordinates, which is equivalent to dividing the luminous line image into equal proportions. Based on this division, the scale coordinates of each representation point in the luminous line image are determined, along with the pixel abscissa of each representation point. At this point, the pixel ordinate of the representation point is still undetermined; that is, the representation points in the luminous line image remain undetermined.

[0118] Figure 5 A schematic diagram illustrating the scale coordinates of a characterizing point in a luminescent image according to an embodiment of the present disclosure is shown.

[0119] like Figure 5 As shown, with Figure 3 The luminous line image B and luminous line image C shown are examples.

[0120] Specifically, taking the luminous line image B as an example, edge detection of the luminous line image B can determine the proportional coordinates of the luminous line image at both ends of the horizontal axis, namely -1 and 1.

[0121] Based on this, the average of the scale coordinates -1 and 1 is calculated to obtain the scale coordinate 0; then the average of the scale coordinates -1 and 0, and 0 and 1 are calculated respectively to obtain the scale coordinates -1 / 2 and 1 / 2, until the preset number of iterations is executed.

[0122] According to embodiments of this disclosure, the process of calculating the scale coordinates is also the process of determining the pixel abscissa of the representation point in the luminous line image. The number of scale coordinates determined in the luminous line image is the same as the number of representation points in the luminous line image, and the pixel abscissa corresponding to the scale coordinate is the pixel abscissa of the corresponding representation point.

[0123] In one embodiment, if the number of iterations is too high, the difference between two adjacent representation points will be less than one pixel. In this case, although the number of iterations is increased, the increased iterations are meaningless, and excessive iterations will increase computational complexity and waste time and computing power. Therefore, the upper limit of the number of iterations should ensure that the difference between two adjacent representation points is greater than one pixel. If the number of iterations is too low, the calculation speed will be inaccurate, so the lower limit of the number of iterations is 3.

[0124] In operation S430, for the pixel abscissa of each representation point in the luminous line image, based on the second preset signal intensity threshold, edge detection is performed on the luminous line image in the vertical direction to determine the upper and lower boundaries of the luminous line image at the pixel abscissa of each representation point.

[0125] According to embodiments of this disclosure, the second preset signal strength threshold is also a defined threshold set based on a certain percentage of the strongest signal in the luminous line image. The second preset signal strength threshold is set as needed. The first preset signal strength threshold and the second preset signal strength threshold may be the same or different. For example, 50% of the strongest signal in the luminous line image can be determined as the second preset signal strength threshold.

[0126] exist Figure 5 In this process, by performing edge detection on the vertical axis of the luminous line image based on the pixel abscissa of the representation point corresponding to the scale coordinate -1 / 2, the upper and lower boundaries of the luminous line image B in the vertical axis direction of the scale coordinate -1 / 2 can be determined.

[0127] In operation S440, the pixel coordinates of each representation point in the luminescent line image are determined based on the pixel coordinates of the upper and lower boundaries of the pixel coordinates at each representation point.

[0128] According to embodiments of this disclosure, the ordinate of each representation point can be calculated based on the upper and lower boundaries of its pixel abscissa. It can be obtained through the following formula (5).

[0129] (5)

[0130] in, It can be represented as the pixel coordinate of the upper boundary corresponding to the pixel x-coordinate of the representation point. It can be represented as the pixel ordinate of the lower boundary corresponding to the pixel x-coordinate of the representation point.

[0131] According to embodiments of this disclosure, the pixel abscissa of a characterization point is determined by iteratively calculating the proportional coordinates, and then the pixel ordinate of the characterization point is determined. Since different pixel abscissas and pixel ordinates of characterization points at the same proportional coordinates can characterize the positions to which the luminescent lines generated by the tracer molecules have moved at different times, the displacement of the tracer molecules in the X-axis direction and the Y-axis direction within a known time interval can be determined based on the pixel abscissas and pixel ordinates of characterization points at the same proportional coordinates.

[0132] According to embodiments of this disclosure, the above-mentioned method for generating a two-dimensional Lagrange velocity field further includes: determining multiple sets of representation points with the same scale coordinates in two adjacent luminescent line images based on the scale coordinates of each representation point in any two adjacent luminescent line images in a molecular marker displacement image, wherein a set of representation points with the same scale coordinates indicates that the two representation points are located at the same scale position in the two adjacent luminescent line images.

[0133] According to embodiments of this disclosure, after obtaining the pixel abscissa and pixel ordinate of each representation point in each luminous line image, in order to calculate the instantaneous velocity, it is necessary to first determine multiple sets of representation points on two adjacent luminous line images, so as to calculate the instantaneous velocity based on the pixel abscissa and pixel ordinate of the multiple sets of representation points.

[0134] In one embodiment, since the position and length of the luminescent lines generated by the tracer molecules change at different times, the pixel abscissa and pixel ordinate of the representation point at the same scale coordinate in different luminescent line images may not be the same.

[0135] exist Figure 5 In the image, luminescent line image B and luminescent line image C are two adjacent luminescent line images. The representation points at the same scale coordinates in luminescent line image B and luminescent line image C can be identified as a set of representation points. For example, the representation point at scale coordinate -1 in luminescent line image B and the representation point at scale coordinate -1 in luminescent line image C can be identified as a set of representation points.

[0136] According to embodiments of this disclosure, the scale coordinates of the luminous line image are equivalent to dividing the luminous line image into equal proportions, so the representation points at the same scale coordinates on different luminous line images are located at the same scale position on different luminous line images.

[0137] In one embodiment, points at the same scale coordinates in multiple luminescent lines within a molecular marker displacement image can be used as a set of characterization points. Based on any two adjacent points in this set of characterization points, the instantaneous velocity at the target location is calculated.

[0138] According to embodiments of this disclosure, based on determining the pixel abscissa and pixel ordinate of each representation point in the luminescent line image, multiple sets of representation points between two adjacent luminescent line images are first determined, so that the instantaneous velocity can be calculated directly based on the multiple sets of representation points between the two adjacent luminescent line images, thereby realizing the reconstruction of the two-dimensional velocity field.

[0139] According to an embodiment of this disclosure, edge detection is performed on the luminescent line image in the horizontal direction based on a first preset signal strength threshold to determine the pixel horizontal coordinates at both ends of the luminescent line image in the horizontal direction, including: determining the pixel coordinates of multiple points in the molecular marker displacement image where the signal strength is greater than the first preset signal strength; and determining the maximum and minimum horizontal coordinates among the pixel coordinates of the multiple points as the pixel horizontal coordinates at both ends of the luminescent line image in the horizontal direction.

[0140] According to embodiments of this disclosure, the signal intensity of each point in the molecular marker displacement image is directly used to determine the two ends of the luminescent line image in the horizontal direction.

[0141] Since the signal intensity of the luminescent line image in the molecular marker displacement image gradually decreases from the image center to the edge along the horizontal axis, and the first preset signal intensity threshold is a delimitation threshold set based on a certain percentage of the strongest signal in the luminescent line image, multiple points in the molecular marker displacement image with signal intensity greater than the first preset signal intensity threshold are first identified. These multiple points are points within the region from the center to the edge of the luminescent line image along the horizontal axis.

[0142] To determine the endpoints of the luminous line image along the horizontal axis, specifically the points at the edges of the luminous line image along the horizontal axis, the maximum and minimum horizontal coordinates in the pixel coordinate system can be used as the pixel horizontal coordinates at the endpoints of the luminous line image along the horizontal axis.

[0143] Similarly, during edge detection in the vertical direction of the luminescent line image, the signal intensity of each point in the molecular marker displacement image can be directly used to determine the two ends of the luminescent line image in the vertical direction.

[0144] Since the signal intensity of the luminescent line image in the molecular marker displacement image gradually decreases from the image center to the edge along the vertical axis, and the second preset signal intensity threshold is a delimitation threshold set based on a certain percentage of the strongest signal in the luminescent line image, multiple points in the molecular marker displacement image with signal intensity greater than the second preset signal intensity threshold are first determined. These determined points are located within the region from the center to the edge of the luminescent line image along the vertical axis.

[0145] To determine the endpoints of the luminous line image along the vertical axis, we need to identify the points at the edges of the luminous line image along the vertical axis. Based on this, the maximum and minimum ordinates in the pixel coordinate system can be defined as the pixel ordinates at the endpoints of the luminous line image along the vertical axis. Specifically, the maximum ordinate is the pixel ordinate of the upper boundary of the luminous line image along the vertical axis, and the minimum ordinate is the pixel ordinate of the lower boundary of the luminous line image along the vertical axis.

[0146] According to embodiments of this disclosure, by performing edge detection on the luminescent line image in both the horizontal and vertical directions, the coordinates of the characterization points can be located more accurately. Simultaneously, the impact of noise in different directions on the measurement results can be effectively reduced, thereby improving the accuracy of velocity measurement and the reliability of image analysis. Furthermore, directly determining the pixel coordinates at both ends of the luminescent line image in the horizontal and vertical directions based on the signal intensity of points in the molecular marker displacement image accelerates the computation speed.

[0147] According to embodiments of this disclosure, the instantaneous velocity at the target location corresponding to each set of characterization points is calculated based on the pixel abscissa and ordinate of multiple sets of characterization points in any two adjacent luminescent line images in a molecular marker displacement image. This includes: for each set of characterization points in two adjacent luminescent line images, determining the displacement of the second characterization point relative to the first characterization point in the horizontal direction based on the pixel abscissas of the first and second characterization points in the two adjacent luminescent line images; determining the displacement of the second characterization point relative to the first characterization point in the vertical direction based on the pixel ordinates of the first and second characterization points; and calculating the instantaneous velocity at the target location based on the displacement of the second characterization point relative to the first characterization point in the horizontal direction and the displacement in the vertical direction, as well as the acquisition time interval between the two adjacent luminescent line images.

[0148] The first and second characterization points are any set of characterization points in two adjacent luminous line images, and the target position represents the midpoint between the first and second characterization points.

[0149] In one embodiment, the second characterization point is located in the later-acquired luminous line image among two adjacent luminous line images, and the first characterization point is located in the earlier-acquired luminous line image among two adjacent luminous line images.

[0150] According to embodiments of this disclosure, for each set of characterization points in two adjacent emission line images, the displacement of the second characterization point relative to the first characterization point in the horizontal direction can be determined based on the respective pixel abscissas of the first and second characterization points in the two adjacent emission line images. Specifically, the pixel abscissas of the second characterization point and the pixel abscissas of the first characterization point are subtracted, and the result of the subtraction is converted into the actual distance in the flow field based on a preset ratio. Thus, the displacement of the second characterization point relative to the first characterization point in the horizontal direction can be determined, that is, the displacement of the tracer molecule in the X-axis direction within the flow field within a known time interval.

[0151] The preset ratio is determined based on the actual distance in the flow field represented by the pixels in the molecular marker displacement image.

[0152] According to embodiments of this disclosure, the displacement of the second characterization point relative to the first characterization point in the vertical direction is determined based on the respective pixel ordinates of the first and second characterization points. Specifically, the pixel ordinates of the second and first characterization points are subtracted, and the result is converted into the actual distance in the flow field based on a preset ratio. Thus, the displacement of the second characterization point relative to the first characterization point in the vertical direction can be determined, i.e., the displacement of the tracer molecule in the Y-axis direction within the flow field over a known time period.

[0153] Based on this, by substituting the displacement of the second characterization point relative to the first characterization point in the horizontal direction and the displacement in the vertical direction, as well as the acquisition time interval between two adjacent luminous line images, into the above formula (4), the instantaneous velocity at the target position can be calculated.

[0154] According to embodiments of this disclosure, based on multiple sets of characterization points in two adjacent luminous line images, the displacement in the horizontal and vertical directions is calculated for each set of characterization points, and the instantaneous velocity at the target location is calculated based on the acquisition time interval between two adjacent luminous line images, thereby enabling the inversion of a two-dimensional Lagrange velocity field.

[0155] Figure 6 A schematic diagram of a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure is shown.

[0156] like Figure 6 As shown, the horizontal and vertical axes can represent the spatial position in the flow field. The horizontal axis, Radial position, represents the radial position, and the vertical axis, Axial position, represents the axial position.

[0157] exist Figure 6 Each arrow in the image can represent the velocity vector at various locations in the flow field, and each arrow can be determined based on a set of characterization points in two adjacent luminous line images. Figure 6The direction of the arrow in the image indicates the direction of the instantaneous velocity, while the length and color of the arrow indicate the magnitude of the instantaneous velocity.

[0158] According to embodiments of this disclosure, before discretizing the molecular marker displacement image, the above-mentioned method for generating a two-dimensional Lagrange velocity field further includes: removing the background signal from the molecular marker displacement image and extracting the image of the region where the luminescent line image is located.

[0159] According to embodiments of this disclosure, the molecular marker shift image can be preprocessed before discretization. The preprocessing specifically includes removing background signals from the molecular marker shift image and extracting the image of the region containing the luminescent line image.

[0160] According to embodiments of this disclosure, preprocessing the molecular marker displacement image before discretizing it helps improve the accuracy of the molecular marker displacement image discretization process, reduces the influence of background signals, and thus improves the accuracy of velocity field generation.

[0161] Based on the above, common methods for measuring linear emission velocity, such as FLEET and FLICC, can only provide the axial velocity at any position on the emission line, i.e., obtain the 1D-1C (1 Dimension - 1 Component) velocity. Even with improvements, a 1D-2C (1 Dimension - 2 Components) velocity field can be obtained on the emission line, but it has not been verified whether this can be achieved in a supersonic flow field, let alone the ability to infer two-dimensional velocity field information.

[0162] This disclosure utilizes the changes in the position and length of luminescent lines in the flow field at different times to invert a two-dimensional Lagrangian velocity field using a molecular marker displacement image containing multiple luminescent line images. Furthermore, this algorithm can obtain the velocity magnitudes of the two X-axis and Y-axis components at the target position between any two adjacent luminescent line images (excluding edges) in the molecular marker displacement image, thus obtaining the two-dimensional velocity field. Therefore, the scheme of this disclosure overcomes the limitation of luminescent line velocimetry techniques such as FLEET and FLICC, which can only obtain a one-dimensional velocity field, and can invert the two-dimensional Lagrangian velocity field information of supersonic flow fields.

[0163] Furthermore, the scheme disclosed herein theoretically has no upper limit on the velocity range in the flow field that can be measured, and the measurement dimension and accuracy are significantly improved compared with traditional methods, enabling the measurement of jet velocities from 1 m / s to 10,000 m / s.

[0164] According to embodiments of this disclosure, a two-dimensional Lagrange velocity field generation system can be used to execute a two-dimensional Lagrange velocity field generation method, that is, the two-dimensional Lagrange velocity field generation system can be used to execute the above-described operations S210 to S240.

[0165] Specifically, the system for generating a two-dimensional Lagrangian velocity field may include a server. This server can be used to acquire molecular marker displacement images; discretize multiple emission line images in the molecular marker displacement images to obtain the pixel coordinates of each representation point in each emission line image; calculate the instantaneous velocity at the target position corresponding to each set of representation points based on the pixel coordinates of multiple sets of representation points in any two adjacent emission line images in the molecular marker displacement images; and generate a two-dimensional Lagrangian velocity field corresponding to the tracer molecule based on the instantaneous velocities at the target positions corresponding to the multiple sets of representation points in the molecular marker displacement images.

[0166] The molecular marker displacement image may include images of the luminescent lines produced by tracer molecules in the flow field acquired at different times; a set of characterization points may include two characterization points located at the same proportion in the horizontal direction of two adjacent luminescent line images.

[0167] Therefore, the server in the two-dimensional Lagrange velocity field generation system can be used to perform the above operations S210 to S240 to generate a two-dimensional Lagrange velocity field corresponding to the tracer molecule.

[0168] According to embodiments of this disclosure, a molecular marker displacement image is obtained by utilizing the position and length changes of the emission lines generated by tracer molecules at different times. This image contains images of the emission lines generated by tracer molecules at different times. Therefore, by discretizing multiple emission line images in the molecular marker displacement image, the pixel abscissa and ordinate of each representation point in the emission line image are obtained. Based on this, the two-dimensional instantaneous velocity at the target location is obtained based on the pixel abscissa and ordinate of two representation points located at the same proportional position in any two adjacent emission line images. This allows a two-dimensional Lagrangian velocity field to be generated based on the instantaneous velocities at all target locations in the molecular marker displacement image, overcoming the limitation of only obtaining a one-dimensional velocity field and realizing the inversion of the two-dimensional Lagrangian velocity field of the flow field.

[0169] According to embodiments of this disclosure, the above-described two-dimensional Lagrange velocity field generation system further includes: a femtosecond laser, a spherical mirror, and a nozzle.

[0170] According to embodiments of this disclosure, a femtosecond laser can be used to emit laser light; a spherical mirror can be used to focus the laser light directly above the nozzle; the nozzle can be used to generate a flow field, and under the action of the laser, the tracer molecules in the flow field generate luminous lines.

[0171] In one embodiment, the tracer molecules of this disclosure characterize the molecules that form the flow field, and are not additional particles.

[0172] Specifically, in one embodiment, the laser emitted by the femtosecond laser is focused by a spherical mirror, with the laser focal point located directly above the nozzle. The focused laser then forms a filament above the nozzle and interacts with tracer molecules in the flow field generated by the nozzle to produce luminescent lines.

[0173] In one embodiment, the flow field generated by the nozzle can be a supersonic flow field.

[0174] In one embodiment, the nozzle may be a Laval nozzle.

[0175] According to embodiments of this disclosure, the femtosecond laser, spherical mirror, and nozzle in the two-dimensional Lagrange velocity field generation system are used together to generate luminous lines from tracer molecules in the flow field, so that the two-dimensional velocity field can be inverted by collecting the luminous lines at different times.

[0176] According to embodiments of this disclosure, the above-described two-dimensional Lagrange velocity field generation system further includes: a signal enhancement camera and a digital signal generator.

[0177] Figure 7 A schematic diagram of a two-dimensional Lagrange velocity field generation system according to an embodiment of the present disclosure is shown.

[0178] like Figure 7 As shown, the femtosecond laser 710 can be used as the laser source of the system to generate laser light, and the generated laser light will pass through the spherical mirror 720. The spherical mirror 720 can focus the laser light and place the laser focal point directly above the nozzle 730, so that the nozzle 730 can cause the tracer molecules in the flow field to emit light lines under the action of the laser light.

[0179] exist Figure 7 In the middle, the digital signal generator 740 is connected to the femtosecond laser 710 and the signal enhancement camera 750, respectively, and the signal enhancement camera 750 is connected to the server 760.

[0180] Specifically, the digital signal generator 740 can be used to send a preset number of exposure signals to the signal enhancement camera 750 at preset time intervals when receiving a pulse signal emitted by the femtosecond laser 710, wherein the femtosecond laser 710 sends a pulse signal to the digital signal generator 740 at the same time as emitting the laser.

[0181] The signal enhancement camera 750 can be used to expose the luminous lines generated by tracer molecules in the flow field each time an exposure signal is received, and after a preset number of exposures, send the generated molecular marker displacement image to the server 760.

[0182] Among them, the signal enhancement camera 750 is used to capture the displacement and length changes of the luminescent lines produced by the tracer molecules in the flow field after each exposure.

[0183] The preset time interval and preset number of times are set as needed.

[0184] In one embodiment, with an acquisition time interval of 4 microseconds and a preset number of acquisitions of 9, the femtosecond laser 710 can send a pulse signal to the digital signal generator 740 at a frequency of 1000Hz. After receiving a pulse signal from the femtosecond laser 710, the digital signal generator 740 will generate 9 exposure signals at preset time intervals according to the settings, and send the exposure signals to the signal enhancement camera 750 at preset time intervals.

[0185] In one embodiment, based on the frequency of the femtosecond laser, the above process can be repeated up to 1000 times per second. However, limited by the camera's output frequency, the camera can actually acquire a maximum of approximately 23 molecular marker displacement images per second. Therefore, the femtosecond laser sends 1000 pulse signals per second to the digital signal generator. After receiving each pulse signal from the femtosecond laser, the digital signal generator generates a preset number of exposure signals. The number of times the digital signal generator generates these preset number of exposure signals is the limit of the camera's exposure triggering. Based on this, the image acquisition limit of this two-dimensional Lagrange velocity field generation system is approximately 23 molecular marker displacement images per second.

[0186] Upon receiving a single exposure signal, the signal enhancement camera 750 performs an exposure to capture the emission lines produced by tracer molecules in the current flow field. The signal enhancement camera 750 sets a gate width, which is the duration of each exposure, for example, 1 microsecond. The signal enhancement camera 750 also sets the number of exposures required to output an image. This requires setting the On-CCD (On-Chip Calibration Data) camera parameter. For example, setting the On-CCD to 9 matches the preset number of exposures generated by the digital signal generator; that is, the camera outputs a molecular marker shift image after 9 exposures.

[0187] The acquisition time interval is the set time interval between two consecutive exposures by the signal enhancement camera.

[0188] In one embodiment, for ease of operation, a preset time interval can be set only for the digital signal generator, meaning that the signal enhancement camera will immediately perform exposure after receiving the exposure signal.

[0189] For example, the acquisition time interval can be set for the digital signal generator 740, meaning the digital signal generator 740 sends an exposure signal to the signal enhancement camera 750 every 4 microseconds, and the signal enhancement camera 750 performs exposure upon receiving the exposure signal. The preset time interval is 4 microseconds, and the delay time of the signal enhancement camera is 0.

[0190] In one embodiment, a preset time interval can be set for the digital signal generator, and a delay time can also be set for the signal enhancement camera, that is, the signal enhancement camera will delay the exposure for a corresponding amount of time after receiving the exposure signal.

[0191] For example, the acquisition time interval can be set for the digital signal generator 740 and the signal enhancement camera 750. Specifically, the digital signal generator 740 sends an exposure signal to the signal enhancement camera 750 every 2 microseconds, and the signal enhancement camera 750, after receiving the exposure signal, delays for 2 microseconds before performing the exposure. The preset time interval is 2 microseconds, and the delay time of the signal enhancement camera is 2 microseconds. In one embodiment, the digital signal generator can be a DG645, and the signal enhancement camera can be an ICCD camera (Intensified Charge-Coupled Device).

[0192] According to embodiments of this disclosure, by using a digital signal generator for coordination between a femtosecond laser and a signal enhancement camera, the signal enhancement camera can perform multiple exposures continuously after the femtosecond laser is excited once, thereby obtaining a molecular marker displacement image containing multiple emission line images, so as to reconstruct the two-dimensional Lagrangian velocity field of the flow field by analyzing the molecules in the molecular marker displacement image.

[0193] Based on the above-described method for generating a two-dimensional Lagrange velocity field, this disclosure also provides an apparatus for generating a two-dimensional Lagrange velocity field. The following will be combined with... Figure 8 The device is described in detail.

[0194] Figure 8 A schematic block diagram of a device for generating a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure is shown.

[0195] like Figure 8 As shown, the two-dimensional Lagrange velocity field generation device 800 of this embodiment includes an acquisition module 810, a processing module 820, a calculation module 830 and a generation module 840.

[0196] The acquisition module 810 is used to acquire molecular marker displacement images, wherein the molecular marker displacement images include images of the emission lines generated by tracer molecules in the flow field at different times. In one embodiment, the acquisition module 810 can be used to perform the operation S210 described above, which will not be repeated here.

[0197] The processing module 820 is used to discretize the multiple luminescence line images in the molecular marker shift image to obtain the pixel abscissa and ordinate of each representation point in each luminescence line image. In one embodiment, the processing module 820 can be used to perform the operation S220 described above, which will not be repeated here.

[0198] The calculation module 830 is used to calculate the instantaneous velocity at the target position corresponding to each set of characterization points based on the pixel abscissa and ordinate of multiple sets of characterization points in any two adjacent luminescent line images in the molecular marker displacement image. A set of characterization points includes two characterization points located at the same proportional position in the horizontal direction of two adjacent luminescent line images. In one embodiment, the calculation module 830 can be used to perform the operation S230 described above, which will not be repeated here.

[0199] The generation module 840 is used to generate a two-dimensional Lagrangian velocity field corresponding to the tracer molecule based on the instantaneous velocity at the target position corresponding to multiple sets of characterization points in the molecular marker displacement image. In one embodiment, the generation module 840 can be used to perform the operation S240 described above, which will not be repeated here.

[0200] According to embodiments of this disclosure, the processing module 820 includes a first detection unit, a first determination unit, a second detection unit, and a second determination unit.

[0201] The first detection unit is used to perform edge detection on each luminescent line image in the molecular marker displacement image in the horizontal direction based on a first preset signal intensity threshold, and to determine the pixel horizontal coordinates and scale coordinates at both ends of the luminescent line image in the horizontal direction.

[0202] The first determining unit is used to iteratively calculate the average value of two adjacent scale coordinates to determine the pixel abscissa and scale coordinate of each representation point in the luminous line image.

[0203] The second detection unit is used to perform edge detection on the vertical axis of the luminous line image based on the second preset signal intensity threshold for the pixel horizontal coordinate of each representation point in the luminous line image, and to determine the upper and lower boundaries of the luminous line image at the pixel horizontal coordinate of each representation point.

[0204] The second determining unit is used to determine the pixel coordinates of each representation point in the luminescent line image based on the pixel coordinates of the upper and lower boundaries of the pixel coordinates of the luminescent line image at each representation point.

[0205] According to embodiments of this disclosure, the two-dimensional Lagrange velocity field generation apparatus 800 further includes a determination module.

[0206] The determination module is used to determine multiple sets of characterization points with the same scale coordinates in two adjacent luminescence line images based on the scale coordinates of each characterization point in any two adjacent luminescence line images in the molecular marker shift image. The fact that a set of characterization points has the same scale coordinates indicates that the two characterization points are located at the same scale position in the two adjacent luminescence line images.

[0207] According to embodiments of this disclosure, the first detection unit includes a first determination subunit and a second determination subunit.

[0208] The first determining subunit is used to determine the pixel coordinates of multiple points in the molecular marker displacement image whose signal intensity is greater than a first preset signal intensity.

[0209] The second determining subunit is used to determine the maximum and minimum abscissas among the pixel coordinates of multiple points as the pixel abscissas at both ends of the luminous line image in the horizontal direction.

[0210] According to embodiments of this disclosure, the calculation module 830 includes a third determining unit, a fourth determining unit, and a calculation unit.

[0211] The third determining unit is used to determine the displacement of the second characterizing point relative to the first characterizing point in the horizontal direction based on the pixel abscissas of the first and second characterizing points in the two adjacent luminous line images for each set of characterizing points, wherein the first characterizing point and the second characterizing point are any set of characterizing points in the two adjacent luminous line images.

[0212] The fourth determining unit is used to determine the displacement of the second representation point relative to the first representation point in the vertical direction based on the pixel ordinates of the first and second representation points.

[0213] The calculation unit is used to calculate the instantaneous velocity at the target position based on the displacement of the second characterization point relative to the first characterization point in the horizontal axis direction and the displacement in the vertical axis direction, as well as the acquisition time interval between two adjacent luminous line images, wherein the target position represents the intermediate position between the first characterization point and the second characterization point.

[0214] According to embodiments of this disclosure, the two-dimensional Lagrange velocity field generation apparatus 800 further includes a preprocessing unit.

[0215] The preprocessing unit is used to remove background signals from the molecular marker shift image and extract the image of the region where the luminescent line image is located before discretizing the molecular marker shift image.

[0216] According to embodiments of this disclosure, any plurality of modules among the acquisition module 810, processing module 820, calculation module 830, and generation module 840 can be combined into one module, or any one of these modules can be split into multiple modules. Alternatively, at least part of the functionality of one or more of these modules can be combined with at least part of the functionality of other modules and implemented in one module. According to embodiments of this disclosure, at least one of the acquisition module 810, processing module 820, calculation module 830, and generation module 840 can be at least partially implemented as hardware circuitry, such as a field-programmable gate array (FPGA), a programmable logic array (PLA), a system-on-a-chip, a system-on-a-substrate, a system-on-package, an application-specific integrated circuit (ASIC), or implemented in hardware or firmware by any other reasonable means of integrating or packaging circuitry, or implemented in software, hardware, or firmware, or in any suitable combination of any of these three implementation methods. Alternatively, at least one of the acquisition module 810, processing module 820, calculation module 830, and generation module 840 can be at least partially implemented as a computer program module, which, when run, can perform corresponding functions.

[0217] Figure 9 A block diagram schematically illustrates an electronic device suitable for implementing a method for generating a two-dimensional Lagrange velocity field according to an embodiment of the present disclosure.

[0218] like Figure 9 As shown, an electronic device 900 according to an embodiment of the present disclosure includes a processor 901, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 902 or a program loaded from a storage portion 908 into a random access memory (RAM) 903. The processor 901 may include, for example, a general-purpose microprocessor (e.g., a CPU), an instruction set processor and / or an associated chipset and / or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor 901 may also include onboard memory for caching purposes. The processor 901 may include a single processing unit or multiple processing units for performing different actions of the method flow according to an embodiment of the present disclosure.

[0219] RAM 903 stores various programs and data required for the operation of electronic device 900. Processor 901, ROM 902, and RAM 903 are interconnected via bus 904. Processor 901 performs various operations of the method flow according to embodiments of the present disclosure by executing programs in ROM 902 and / or RAM 903. It should be noted that the programs may also be stored in one or more memories other than ROM 902 and RAM 903. Processor 901 may also perform various operations of the method flow according to embodiments of the present disclosure by executing programs stored in said one or more memories.

[0220] According to embodiments of this disclosure, the electronic device 900 may further include an input / output (I / O) interface 905, which is also connected to a bus 904. The electronic device 900 may also include one or more of the following components connected to the input / output (I / O) interface 905: an input section 906 including a keyboard, mouse, etc.; an output section 907 including a cathode ray tube (CRT), liquid crystal display (LCD), etc., and a speaker, etc.; a storage section 908 including a hard disk, etc.; and a communication section 909 including a network interface card such as a LAN card, modem, etc. The communication section 909 performs communication processing via a network such as the Internet. A drive 910 is also connected to the input / output (I / O) interface 905 as needed. A removable medium 911, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed on the drive 910 as needed so that computer programs read from it can be installed into the storage section 908 as needed.

[0221] This disclosure also provides a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiments; or it may exist independently and not assembled into the device / apparatus / system. The computer-readable storage medium carries one or more programs that, when executed, implement the method according to the embodiments of this disclosure.

[0222] According to embodiments of this disclosure, the computer-readable storage medium may be a non-volatile computer-readable storage medium, such as including, but not limited to: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this disclosure, the computer-readable storage medium may be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. For example, according to embodiments of this disclosure, the computer-readable storage medium may include ROM 902 and / or RAM 903 and / or one or more memories other than ROM 902 and RAM 903 described above.

[0223] Embodiments of this disclosure also include a computer program product comprising a computer program containing program code for performing the methods shown in the flowchart. When the computer program product is run on a computer system, the program code enables the computer system to implement the method for generating a two-dimensional Lagrange velocity field provided in embodiments of this disclosure.

[0224] When the computer program is executed by the processor 901, it performs the functions defined in the system / apparatus of this disclosure embodiments. According to embodiments of this disclosure, the systems, apparatuses, modules, units, etc., described above can be implemented by computer program modules.

[0225] In one embodiment, the computer program may rely on a tangible storage medium such as an optical storage device or a magnetic storage device. In another embodiment, the computer program may also be transmitted and distributed in the form of signals over a network medium, and downloaded and installed via the communication section 909, and / or installed from a removable medium 911. The program code contained in the computer program can be transmitted using any suitable network medium, including but not limited to: wireless, wired, etc., or any suitable combination thereof.

[0226] In such an embodiment, the computer program can be downloaded and installed from a network via the communication section 909, and / or installed from the removable medium 911. When the computer program is executed by the processor 901, it performs the functions defined in the system of this disclosure embodiment. According to embodiments of this disclosure, the systems, devices, apparatuses, modules, units, etc., described above can be implemented by computer program modules.

[0227] According to embodiments of this disclosure, program code for executing the computer programs provided in embodiments of this disclosure can be written in any combination of one or more programming languages. Specifically, these computational programs can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. Programming languages ​​include, but are not limited to, languages ​​such as Java, C++, Python, "C", or similar programming languages. The program code can execute entirely on a user's computing device, partially on a user's device, partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0228] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0229] Those skilled in the art will understand that the features described in the various embodiments of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0230] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A method for generating a two-dimensional Lagrangian velocity field, comprising: Acquire molecular marker displacement images, wherein the molecular marker displacement images include images of luminescent lines produced by tracer molecules in the flow field acquired at different times; The molecular marker displacement image is discretized to obtain the pixel abscissa and ordinate of each representation point in each luminescent line image. This includes: for each luminescent line image in the molecular marker displacement image, edge detection is performed on the luminescent line image along the horizontal axis based on a first preset signal intensity threshold to determine the pixel abscissa and scale coordinates at both ends of the luminescent line image along the horizontal axis; the average value of two adjacent scale coordinates is calculated iteratively multiple times to determine the pixel abscissa and scale coordinates of each representation point in the luminescent line image; for the pixel abscissa of each representation point in the luminescent line image, edge detection is performed on the luminescent line image along the vertical axis based on a second preset signal intensity threshold to determine the upper and lower boundaries of the luminescent line image at each representation point's pixel abscissa; and the pixel ordinate of each representation point in the luminescent line image is determined based on the pixel ordinates of the upper and lower boundaries at each representation point's pixel abscissa. The instantaneous velocity at the target position corresponding to each set of characterization points is calculated based on the pixel abscissa and ordinate of multiple sets of characterization points in any two adjacent luminescent line images of the molecular marker displacement image. This includes: for each set of characterization points in the two adjacent luminescent line images, determining the displacement of the second characterization point relative to the first characterization point in the horizontal direction based on the pixel abscissa of the first and second characterization points in the two adjacent luminescent line images, wherein the first and second characterization points are any set of characterization points in the two adjacent luminescent line images; determining the displacement of the second characterization point relative to the first characterization point in the vertical direction based on the pixel ordinate of the first and second characterization points; and calculating the instantaneous velocity at the target position based on the displacement of the second characterization point relative to the first characterization point in the horizontal direction and the displacement in the vertical direction, as well as the acquisition time interval between the two adjacent luminescent line images, wherein the target position represents the intermediate position between the first and second characterization points, and a set of characterization points includes two characterization points located at the same proportional position in the horizontal direction in the two adjacent luminescent line images. Based on the instantaneous velocity at the target position corresponding to multiple sets of characterization points in the molecular marker displacement image, a two-dimensional Lagrangian velocity field corresponding to the tracer molecule is generated. The method further includes: determining multiple sets of representation points with the same scale coordinates in the two adjacent luminescent line images based on the scale coordinates of each representation point in any two adjacent luminescent line images in the molecular marker displacement image, wherein a set of representation points with the same scale coordinates indicates that the two representation points are located at the same scale position in the two adjacent luminescent line images.

2. The method according to claim 1, wherein, Based on a first preset signal strength threshold, edge detection is performed on the luminous line image along the horizontal axis to determine the pixel coordinates at both ends of the luminous line image along the horizontal axis, including: Determine the pixel coordinates of multiple points in the molecular marker displacement image whose signal intensity is greater than the first preset signal intensity; The maximum and minimum abscissas among the pixel coordinates of the plurality of points are determined as the pixel abscissas of the two ends of the luminous line image in the horizontal direction.

3. The method according to claim 1, wherein, Before discretizing the molecular marker shift image, the process further includes: Background signals are removed from the molecular marker shift image, and the image of the region containing the luminescent line image is extracted.

4. A system for generating a two-dimensional Lagrange velocity field, applied to the method for generating a two-dimensional Lagrange velocity field as described in any one of claims 1 to 3, the system comprising: Server, used for: Acquire molecular marker displacement images, wherein the molecular marker displacement images include images of luminescent lines produced by tracer molecules in the flow field acquired at different times; The multiple luminescent line images in the molecular marker displacement image are discretized to obtain the pixel coordinates of each representation point in each luminescent line image; Based on the pixel coordinates of multiple sets of characterization points in any two adjacent luminescent line images in the molecular marker displacement image, the instantaneous velocity at the target position corresponding to each set of characterization points is calculated. Here, a set of characterization points includes two characterization points located at the same proportional position in the horizontal direction of the two adjacent luminescent line images. Based on the instantaneous velocity at the target position corresponding to multiple sets of characterization points in the molecular marker displacement image, a two-dimensional Lagrange velocity field corresponding to the tracer molecule is generated.

5. The generation system according to claim 4, further comprising: Femtosecond laser, spherical mirror, nozzle; The femtosecond laser is used to emit laser light; The spherical mirror is used to focus the laser directly above the nozzle; The nozzle is used to generate a flow field, and under the action of the laser, the tracer molecules in the flow field generate light-emitting lines.

6. The generation system according to claim 5, further comprising: Signal enhancement cameras and digital signal generators; The digital signal generator is used to send an exposure signal to the signal enhancement camera a preset number of times at a preset time interval when it receives a pulse signal emitted by the femtosecond laser, wherein the femtosecond laser sends the pulse signal to the digital signal generator at the same time as emitting the laser. The signal enhancement camera is used to expose the luminescent lines generated by the tracer molecules in the flow field each time the exposure signal is received, and after the preset number of exposures, send the generated molecular marker displacement image to the server.

7. A device for generating a two-dimensional Lagrange velocity field, characterized in that, The device includes: The acquisition module is used to acquire molecular marker displacement images, wherein the molecular marker displacement images include images of luminescent lines generated by tracer molecules in the flow field at different times; The processing module is used to discretize the multiple luminescent line images in the molecular marker displacement image to obtain the pixel abscissa and pixel ordinate of each representation point in each luminescent line image; The processing module includes a first detection unit, a first determination unit, a second detection unit, and a second determination unit. The first detection unit is used to perform edge detection on each luminescent line image in the molecular marker displacement image in the horizontal direction based on a first preset signal intensity threshold, and determine the pixel horizontal coordinates and proportional coordinates at both ends of the luminescent line image in the horizontal direction. The first determining unit is used to iteratively calculate the average value of two adjacent proportional coordinates to determine the pixel abscissa and proportional coordinate of each representation point in the luminous line image. The second detection unit is used to perform edge detection on the luminous line image in the vertical direction based on the second preset signal intensity threshold for the pixel horizontal coordinate of each characterization point in the luminous line image, and to determine the upper and lower boundaries of the luminous line image at the pixel horizontal coordinate of each characterization point. The second determining unit is used to determine the pixel coordinates of each representation point in the luminous line image based on the pixel coordinates of the upper boundary and the lower boundary of the pixel coordinates of the luminous line image at each representation point. The calculation module is used to calculate the instantaneous velocity at the target position corresponding to each set of characterization points based on the pixel abscissa and pixel ordinate of multiple sets of characterization points in any two adjacent luminescent line images in the molecular marker displacement image. A set of characterization points includes two characterization points located at the same proportional position in the horizontal direction of the two adjacent luminescent line images. The calculation module includes a third determining unit, a fourth determining unit, and a calculation unit. The third determining unit is used to determine the displacement of the second characterizing point relative to the first characterizing point in the horizontal direction based on the pixel horizontal coordinates of the first characterizing point and the second characterizing point in the two adjacent luminous line images for each set of characterizing points, wherein the first characterizing point and the second characterizing point are any set of characterizing points in the two adjacent luminous line images. The fourth determining unit is used to determine the displacement of the second characterization point relative to the first characterization point in the vertical axis direction based on the pixel ordinates of the first characterization point and the second characterization point, respectively. The calculation unit is used to calculate the instantaneous velocity at the target position based on the displacement of the second characterization point relative to the first characterization point in the horizontal axis direction and the displacement in the vertical axis direction, as well as the acquisition time interval between the two adjacent luminous line images, wherein the target position represents the midpoint between the first characterization point and the second characterization point. The generation module is used to generate a two-dimensional Lagrangian velocity field corresponding to the tracer molecule based on the instantaneous velocity at the target position corresponding to multiple sets of characterization points in the molecular marker displacement image. The device for generating the two-dimensional Lagrange velocity field also includes a determination module. The determination module is used to determine multiple sets of representation points with the same scale coordinates in two adjacent luminescent line images based on the scale coordinates of each representation point in any two adjacent luminescent line images in the molecular marker displacement image. The same scale coordinates of a set of representation points indicate that the two representation points are located at the same scale position in the two adjacent luminescent line images.

Images