Method and device for determining static friction force of bubbles on surface of femtosecond laser modified sample, and storage medium

Abstract

The application discloses a method and device for determining static friction of a surface bubble of a femtosecond laser modified sample and a storage medium. The method comprises the following steps: placing the femtosecond laser modified sample as a heating surface in a test channel arranged vertically to the ground, and controlling a working medium in the test channel to flow in a direction upwardly perpendicular to the ground; applying a heating power to the femtosecond laser modified sample to generate a bubble on a heating surface of the femtosecond laser modified sample; determining a long axis length and a short axis length of the bubble in a preset state, and a bubble movement speed of the bubble; the preset state represents a shape and a movement state of the bubble when the bubble is close to separating from the heating surface; and determining the static friction of the bubble in the preset state according to the long axis length, the short axis length and the bubble movement speed.

Description

Technical Field

[0001] This application relates to the field of reactor processing technology, and in particular to a method, apparatus and storage medium for determining the static friction force of bubbles on the surface of femtosecond laser-modified samples. Background Technology

[0002] In nuclear reactor systems, fuel assemblies, heat exchangers, and other equipment components require efficient heat transfer. Under relatively hot conditions, a two-phase flow environment of steam and water forms inside the equipment. The detachment characteristics of bubbles significantly affect the boiling heat transfer efficiency between the heated surface and the mainstream working fluid. Current technologies can only provide a rough analysis of the forces acting on bubbles on smooth surfaces within simple channels, failing to address the microscopic porous structure characteristics of femtosecond laser-modified surfaces. Furthermore, there are no standardized experimental methods to capture the key parameters as bubbles are about to detach, and a precise calculation model for static friction based on force balance has not been established. This results in the inability to quantify the magnitude of the static friction force exerted on bubbles by modified surfaces prepared with different process parameters.

[0003] This technical deficiency directly causes technical pain points in the industry. On the one hand, it is impossible to evaluate the bubble detachment characteristics of the surface under different femtosecond laser modification processes through quantitative indicators. The process parameters can only be adjusted based on experience, resulting in high research and development trial and error costs and low efficiency. On the other hand, the lack of core data support such as static friction makes it impossible to achieve precise iterative optimization of the femtosecond laser modification process. It is difficult to prepare modified surfaces that match different boiling heat transfer requirements, which limits the engineering application of femtosecond laser modification technology in the manufacturing of high-end equipment such as nuclear reactor fuel assemblies and heat exchangers. Summary of the Invention

[0004] This invention provides a method, apparatus, system, and storage medium for determining the static friction force of surface bubbles in femtosecond laser-modified samples, thereby at least solving the problem in related technologies where the static friction force of modified surface bubbles cannot be accurately quantified. The technical solution of this invention is as follows: According to a first aspect of the present invention, a method for determining the static friction force of bubbles on the surface of a femtosecond laser-modified sample is provided. The method includes: placing the femtosecond laser-modified sample as a heating surface in a test channel arranged perpendicular to the ground, and controlling the working fluid in the test channel to flow in an upward direction perpendicular to the ground; applying heating power to the femtosecond laser-modified sample to generate bubbles on the heated surface of the femtosecond laser-modified sample; determining the major axis length and minor axis length of the bubble, and the bubble movement speed of the bubble, when the bubble is in a preset state; the preset state characterizes the shape and movement state of the bubble when it is about to detach from the heated surface; and determining the static friction force experienced by the bubble in the preset state based on the major axis length, minor axis length, and bubble movement speed.

[0005] In one implementation, the static friction force acting on the bubble in a preset state is determined based on the major axis length, minor axis length, and bubble velocity. This includes: determining the equivalent diameter of the bubble based on the major and minor axis lengths; determining the buoyancy force acting on the bubble in the preset state based on the equivalent diameter, liquid phase density, and gravitational acceleration; determining the drag force acting on the bubble in the preset state based on the equivalent diameter, liquid phase density, liquid phase dynamic viscosity, and relative velocity between the gas and liquid phases; determining the gravity of the bubble in the preset state based on the gas phase density and equivalent diameter; and determining the static friction force based on the force balance between buoyancy, drag force, gravity, and static friction force.

[0006] In another implementation, the method further includes: if the area of ​​the contact region between the heating surface and the bubble increases within a first growth range, then the bubble is determined to be in a preset state.

[0007] In another implementation, the method further includes: if the length growth rate of the major axis and / or minor axis is detected to be within a second growth range, then the bubble is determined to be in a preset state.

[0008] In another implementation, the method further includes: if the bubble velocity is detected to increase in the direction perpendicular to the heating surface, then the bubble is determined to be in a preset state.

[0009] In another implementation, the method further includes: determining the target difficulty of the bubble detaching from the modified sample surface under static friction based on the positive correlation between the magnitude of static friction and the ease with which the bubble detaches from the modified sample surface; reducing the scanning power of the femtosecond laser or increasing the scanning spacing when the target difficulty is greater than the preset difficulty; and increasing the scanning power of the femtosecond laser or decreasing the scanning spacing when the target difficulty is less than or equal to the preset difficulty.

[0010] In another implementation, the method further includes: if the static friction force is detected to be greater than a preset threshold, then the scanning power of the femtosecond laser is reduced or the scanning spacing is increased; the preset threshold is determined based on the reference value of the static friction force of bubbles on the unmodified metal surface; if the static friction force is detected to be less than the preset threshold, then the scanning power of the femtosecond laser is increased or the scanning spacing is decreased.

[0011] In another implementation, the surface of the femtosecond laser-modified sample has a porous microstructure, and the geometric dimensions of the porous microstructure are within a preset size range; the material of the femtosecond laser-modified sample is metal; and the test channel is a test channel.

[0012] According to a second aspect of the present invention, a device for determining the static friction force of surface bubbles in a femtosecond laser-modified sample is provided. The device comprises: a control unit configured to place the femtosecond laser-modified sample as a heating surface in a test channel arranged perpendicular to the ground, and to control the flow of a working fluid in the test channel in an upward direction perpendicular to the ground; a bubble generating unit configured to apply heating power to the femtosecond laser-modified sample to generate bubbles on the heated surface of the femtosecond laser-modified sample; a determining unit configured to determine the major axis length and minor axis length of the bubble in a preset state, and the bubble's movement speed; the preset state characterizes the morphology and movement state of the bubble as it approaches detachment from the heated surface; and the determining unit further configured to determine the static friction force experienced by the bubble in the preset state based on the major axis length, minor axis length, and bubble movement speed.

[0013] According to a third aspect of the present invention, a system for determining the static friction force of surface bubbles in a femtosecond laser-modified sample is provided, the system being configured to perform a method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample as described in the first aspect and any possible implementation thereof.

[0014] According to a fourth aspect of the present invention, an electronic device is provided, comprising: a processor and a memory for storing processor-executable instructions; wherein the processor is configured to execute the executable instructions to implement a method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample, as described in the first aspect and any possible implementation thereof.

[0015] According to a fifth aspect of the present invention, a computer-readable storage medium is provided, on which instructions are stored, which, when executed by a processor of an electronic device, enable the electronic device to perform a method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample, as described in the first aspect and any possible implementation thereof.

[0016] According to a sixth aspect of the present invention, a computer program product is provided, the computer program product including computer instructions, which, when executed on an electronic device, cause the electronic device to perform the method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample as described in the first aspect and any possible implementation thereof.

[0017] The technical solution provided by this invention brings at least the following beneficial effects: By placing the femtosecond laser-modified sample as the heating surface in a test channel perpendicular to the ground and controlling the working fluid to flow vertically upwards, a standardized test environment highly matched with the actual stress scenario of bubbles on the modified surface is constructed. This overcomes the limitation of related technologies that can only analyze the stress on bubbles on smooth surfaces and is adapted to the microscopic pore structure characteristics of femtosecond laser-modified surfaces. Furthermore, by determining the preset state of bubbles nearing detachment and collecting the major and minor axis lengths and bubble velocity in this state, the core effective parameters for calculating static friction force are accurately captured. This is the first time that the quantitative determination of static friction force of bubbles on the surface of femtosecond laser-modified samples has been achieved, filling a technological gap in this field. At the same time, the complete process from test setup, heating and bubble formation to parameter acquisition and static friction force determination is clarified, making the determination process of static friction force operable and no longer dependent on experience. This provides core quantitative data support for subsequent evaluation of bubble detachment characteristics and optimization of modification processes, opening up the technical link between static friction force quantification and process optimization, and solving the pain point of lacking effective data to guide process optimization in related technologies.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application, and do not constitute an undue limitation of this application.

[0020] Figure 1 This is a schematic diagram of a femtosecond laser-modified surface roughness structure in a related art, according to an exemplary embodiment; Figure 2 This is a flowchart illustrating a method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample according to an exemplary embodiment; Figure 3 This is a schematic diagram of a test environment according to an exemplary embodiment; Figure 4 This is a schematic diagram of the actual shape of a bubble according to an exemplary embodiment; Figure 5 This is a schematic diagram of the force balance of a bubble according to an exemplary embodiment; Figure 6 This is a block diagram illustrating a device for determining the static friction force of surface bubbles in a femtosecond laser-modified sample according to an exemplary embodiment. Figure 7 This is a schematic diagram of an electronic device according to an exemplary embodiment. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0022] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0023] Before providing a detailed description of the method for determining the static friction force of surface bubbles in femtosecond laser-modified samples provided in this application embodiment, let's briefly introduce the application scenarios involved in this application embodiment.

[0024] In nuclear reactor systems, fuel assemblies, heat exchangers, and other equipment components require heat transfer, resulting in a steam-water two-phase flow environment under relatively hot conditions. The bubble detachment characteristics significantly impact boiling heat transfer between the heated surface and the main working fluid. Among related technologies, femtosecond laser modification technology can create surfaces such as… Figure 1 The rough structure shown. Different rough structures can lead to bubbles that are easy or difficult to detach, and these different detachment characteristics can also affect the surface heat transfer efficiency.

[0025] Therefore, in order to obtain femtosecond laser-modified surfaces for fuel components and heat exchangers with different boiling heat transfer characteristics, a test and calculation method for the static friction force of bubbles on the surface of femtosecond laser-modified samples can effectively assess the ease of bubble detachment based on the magnitude of the static friction force, thereby guiding the optimization and upgrading of femtosecond laser-modified surfaces.

[0026] To address the aforementioned issues, this application considers the differences in the static friction force leading to bubble detachment characteristics of femtosecond laser-modified surfaces prepared with different process parameters and methods. It proposes a method for determining the static friction force of bubbles on the surface of femtosecond laser-modified samples. First, by placing the femtosecond laser-modified sample in a test channel perpendicular to the ground and controlling the working fluid to flow vertically upwards, a standardized test environment matching the actual stress scenario of the bubbles is constructed. This adapts to the microscopic pore structure characteristics of the femtosecond laser-modified surface, overcoming the limitation of related technologies that can only roughly analyze the stress on bubbles on smooth surfaces. Simultaneously, by determining the preset state of the bubble near detachment, the major and minor axis lengths and bubble velocity in this critical state are accurately captured, providing real and effective core parameters for static friction force calculation. This is the first time that the static friction force of bubbles on the surface of femtosecond laser-modified samples has been quantitatively determined, solving the technical pain point of being unable to quantify this core parameter in the background technology.

[0027] Secondly, by locking the preset state of the bubble nearing detachment as the parameter acquisition node, the interference of parameter fluctuations during the bubble growth stage on the calculation results is avoided, ensuring that the acquired major axis, minor axis length, and motion speed can truly reflect the force basis when the bubble is about to detach. Based on these key parameters, static friction is derived, making the calculation results of static friction highly consistent with the actual resistance effect of the modified surface on the bubble. The obtained static friction data has accuracy and reliability, completely changing the status quo of the background technology where there is no core data to support process optimization, and providing a quantitative and referable basis for adjusting the process parameters of femtosecond laser modification.

[0028] Furthermore, this application clarifies the complete process from test setup and heating to bubble formation, to the acquisition of preset state parameters and determination of static friction. The operation standards and nodes for each step are clear, and the process can be implemented without relying on experience, thus solving the problem of the lack of standardized testing methods in the background technology. At the same time, the process is compatible with femtosecond laser modified samples of various metal materials, and static friction tests of samples prepared with different process parameters can be completed under a unified test framework, which improves the versatility of the method and facilitates its promotion and application in the industry.

[0029] Finally, by determining the static friction force under the preset state, a quantitative correlation was directly established between the microstructure characteristics of the modified surface and the core influencing factors of bubble detachment. Subsequently, the ease or difficulty of bubble detachment from the modified sample surface can be accurately assessed based on this static friction force data, thereby optimizing the femtosecond laser modification process parameters in a targeted manner.

[0030] For ease of understanding, the method for determining the static friction force of surface bubbles in the femtosecond laser-modified sample provided in this application will be described in detail below with reference to the accompanying drawings.

[0031] Figure 2 This is a flowchart illustrating a method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample according to an exemplary embodiment, such as... Figure 2 As shown, a method for determining the static friction force of surface bubbles in the femtosecond laser-modified sample is implemented.

[0032] S21, the femtosecond laser-modified sample is placed as the heating surface in a test channel arranged vertically to the ground, and the working fluid in the test channel is controlled to flow in an upward direction perpendicular to the ground.

[0033] The test channel is arranged vertically to the ground and the working fluid flows vertically upward. This is to ensure that the buoyancy, drag, gravity, and static friction of the bubbles are balanced in the vertical direction, avoiding interference from horizontal forces and ensuring the accuracy of static friction calculation.

[0034] S22, apply heating power to the femtosecond laser-modified sample to generate bubbles on the heated surface of the femtosecond laser-modified sample.

[0035] S23, determine the major axis length and minor axis length of the bubble when the bubble is in a preset state, and the bubble's velocity.

[0036] The preset state characterizes the shape and motion of the bubble as it approaches detachment from the heated surface.

[0037] S24. Determine the static friction force on the bubble in the preset state based on the length of the major axis, the length of the minor axis, and the speed of bubble movement.

[0038] In some embodiments, the determination of static friction force of bubbles on the surface of a femtosecond laser-modified sample is carried out through the following steps.

[0039] First, establish the experimental environment.

[0040] A test channel arranged vertically to the ground was selected. The stainless steel femtosecond laser modified sample was cut into a 50mm×50mm×5mm piece, which was used as the heating surface and fixed in the core test area inside the test channel to ensure that the heating surface of the sample was in close contact with the inner wall of the channel without gaps. Water was introduced into the test channel and the flow control system controlled the working fluid to flow stably in a direction perpendicular to the ground. In this embodiment, the inlet flow velocity of the working fluid was controlled at 0.5m / s, the pressure in the test channel was maintained at standard atmospheric pressure of 0.1MPa, and the initial temperature was 25℃.

[0041] Secondly, bubble generation. The femtosecond laser-modified sample is heated by a heating device on the back of the sample. The heating power is increased in a stepwise manner, with an initial heating power of 50W and an increase of 10W each time, and a holding time of 5 minutes, until continuous and stable bubble nucleation and growth appear on the heated surface of the sample. In this embodiment, when the heating power is increased to 120W, bubbles that meet the experimental requirements appear on the heated surface.

[0042] Third, collect preset state parameters.

[0043] The preset state is the shape and motion state of the bubble nearing detachment from the heating surface. At this time, the shape and force of the bubble tend to be stable, which is the key node for parameter acquisition. A high-speed camera (frame rate ≥1000fps) is used to continuously capture the growth and motion process of the bubble on the heating surface. The captured image frames are analyzed by image analysis software to determine the major axis length Li1 and minor axis length Li2 of the bubble when it is in the preset state. The bubble motion velocity ug is calculated by the time and displacement difference of the image frames.

[0044] For example, in this embodiment, when a bubble is about to detach, the major axis length Li1 is 0.8 mm, the minor axis length Li2 is 0.6 mm, and the upward movement speed of the bubble along the vertical heating surface is 0.05 m / s.

[0045] Fourth, determine the static friction force.

[0046] Based on the collected major axis length, minor axis length, and bubble velocity, combined with the bubble's force characteristics and equilibrium relationship, the static friction force acting on the bubble under this preset state is calculated.

[0047] Through the above embodiments, the experimental environment was set up, bubble generation and preset state parameter acquisition were completed, laying the foundation for accurate calculation of static friction force, breaking through the limitation of the lack of standardized parameter acquisition methods in related technologies, and realizing the accurate capture of key parameters when the bubble is about to detach.

[0048] As one implementation method, the specific process of determining the static friction force experienced by the bubble in the preset state in step S24 is as follows.

[0049] First, the equivalent diameter of the bubble is determined based on the lengths of its major and minor axes.

[0050] Specifically, in combination Figure 3 The given schematic diagram of the test environment for the static friction force of the modified surface on the bubble and Figure 4 A schematic diagram of the actual morphology of bubbles is shown. The morphology of bubbles on the modified surface was captured using a high-speed camera, recording the bubble shape as it was about to detach. Since bubbles are mostly round or elliptical near detachment, and not perfectly round, their shape is determined by their major axis length L. i1 and minor axis length L i2 The geometric mean is used to determine the equivalent diameter di of the bubble, and the calculation formula is as follows: Formula (1).

[0051] (1).

[0052] Furthermore, the speed of bubble movement can be easily measured by using a high-speed camera to measure the image. .

[0053] The equivalent diameter of the bubble mentioned above is the basic parameter for subsequent force calculations. The irregular bubble is standardized by using the geometric mean method to ensure the uniformity and accuracy of the force calculations.

[0054] Secondly, the buoyancy force on the bubble in the preset state is determined based on the equivalent diameter of the bubble, the liquid phase density of the bubble, and the gravitational acceleration.

[0055] Buoyancy arises from the density difference between the gas and liquid phases, is related to the volume of the bubble, and is the force that drives the bubble to detach. For vertical upwelling, buoyancy... F B The specific formula for calculating the buoyancy force that drives the bubble to detach is as follows: Formula (2).

[0056] (2).

[0057] in, F B For buoyancy, d i This is based on experimental testing and calculated using the above formula (1). ρ is the density of the liquid phase, which can be calculated by obtaining the temperature and pressure of the measurement area, and g is the acceleration due to gravity.

[0058] Third, the drag force on the bubble in the preset state is determined based on the equivalent diameter of the bubble, the liquid phase density of the bubble, the dynamic viscosity of the liquid phase, and the relative velocity of the gas and liquid phases.

[0059] The drag force is generated by the shearing action of the mainstream fluid in the channel and is the force that drives the bubbles to detach. For vertical upflow, the drag force... The force that drives the bubble to detach is calculated using the following formulas (3) and (4).

[0060] (3).

[0061] in, The density of the liquid phase is... For the dynamic viscosity of the liquid phase, d i Re is the Reynolds number, calculated based on experimental testing and formula (1). denoted as the relative velocity between the gas and liquid phases.

[0062] (4).

[0063] in, Measured by a high-speed camera, It is obtained from the controlled inlet flow rate measurement.

[0064] Fourth, the gravity of the bubble in the preset state is determined based on the gas phase density and equivalent diameter of the bubble.

[0065] Gravity is a downward force perpendicular to the ground, which resists the escape of bubbles. For vertical upwelling, gravity... F G The force that prevents the bubble from detaching can be obtained by calculating the mass of the bubble and the gravity acting on it. The specific process of calculating gravity is as follows (5).

[0066] (5).

[0067] in, F G For gravity, d i This is based on experimental testing and calculated using formula (1). ρ is the density of the gas phase, which can be calculated by obtaining the temperature and pressure of the measurement area, and g is the acceleration due to gravity.

[0068] Fifth, the static friction force is determined based on the force balance between buoyancy, drag, gravity and static friction.

[0069] Combination Figure 5 In a diagram showing the force equilibrium of a bubble when the channel is arranged perpendicular to the ground, the main flow is vertically upward. For a vertically upward flow, the static friction force... F N The force that hinders bubble detachment is related to the roughness of the surface microstructure prepared by different laser modification process parameters. Simultaneously, the boiling interaction between the bubble and the microstructure acting as nucleation cavities also affects bubble detachment. Therefore, this force can be considered a specific force exerted on the bubble by the modified surface microstructure, and is related to the characteristics of the surface microstructure.

[0070] Specifically, when the bubble is in the preset state (near detachment), the forces along the vertical direction are in equilibrium. Buoyancy and drag are the upward driving forces, while gravity and static friction are the downward resisting forces. Since the rough modified surface and microstructure are difficult to characterize, this force is generally difficult to actively solve and predict. However, this force can be given based on the force balance. Therefore, the static friction calculation formula is derived from the force balance relationship as shown in the following formula (6).

[0071] (6).

[0072] Among them, buoyancy, gravity, and drag need to be calculated based on the visual data when the bubble is about to detach and in combination with formulas (1)-(5). Static friction is obtained through this method. .

[0073] The static friction force reflects the ease with which bubbles detach from the modified surface. A higher static friction force makes it more difficult for bubbles to detach from the heated surface, resulting in bubbles remaining on the heated surface for a longer period. This is detrimental to the formation of the next nucleated bubble and leads to higher temperatures on the surface covered by bubbles with poor thermal conductivity. Therefore, static friction force is crucial for understanding the boiling heat transfer characteristics of femtosecond laser-modified surfaces with different roughnesses and microstructures prepared using different process parameters, and can guide the optimization and iteration of femtosecond laser modification processes.

[0074] Through the above implementation steps, the quantitative calculation of static friction force was realized, providing clear physical theory and mathematical model support for the calculation of static friction force. This solved the problem of the lack of scientific calculation models in related technologies, and the calculation results can truly reflect the actual obstruction effect of femtosecond laser modified surfaces on bubbles.

[0075] As one implementation, if the area of ​​the contact region between the heating surface and the bubble is detected to increase within a first growth range, then the bubble is determined to be in a preset state.

[0076] The process of collecting the area of ​​the contact region is as follows: A high-speed camera and image analysis software are used to identify and calculate the area of ​​the contact region between the heated surface and the bubble during bubble growth in real time. The area value St of the contact region at different time points is recorded, and the area growth value ΔS = St + 1 at adjacent time points is calculated. St and the area growth rate η = StΔS × 100%.

[0077] The setting of the first growth range is based on the physical laws of bubble growth. When the bubble is about to detach, the contact point with the heated surface tends to shrink, and the contact area no longer expands significantly. Therefore, the area growth will be at an extremely low level. This range can be adaptively adjusted according to the sample material, modification process, and working conditions, all of which are within the protection scope of this invention.

[0078] The process of setting the first growth range is as follows: The first growth range is the area growth characteristics of the contact area when the bubble is about to detach. According to the growth law of bubbles on the surface modified by femtosecond laser, the area of ​​the contact area will increase rapidly during the bubble growth stage, and the area of ​​the contact area will tend to stabilize when the bubble is about to detach, and the growth value and growth rate will decrease significantly. In this embodiment, the first growth range is set as follows: the area growth value ΔS≤0.01mm2 and the area growth rate η≤1%.

[0079] The process for determining the preset state is as follows: When the area growth value and growth rate of the contact area between the heating surface and the bubble are both within the first growth range mentioned above, it can be determined that the bubble is in a preset state that is about to detach. At this time, the major axis length, minor axis length and bubble movement speed in this state are immediately collected.

[0080] For example, in the early stage of bubble growth, the contact area growth value ΔS=0.08 and the growth rate η=15%; when the bubble grows to 1.2s, the contact area growth value ΔS=0.008 and the growth rate η=0.8%, both of which are within the first growth range. It is determined that the bubble is in the preset state, and then the parameters are collected.

[0081] This implementation process determines the morphology of a bubble as it is about to detach, primarily by capturing the characteristic state of the bubble at the end of its growth phase using a high-speed camera. By quantifying the increase in the contact area, a preset state is determined, solving the problem of the lack of a unified standard for determining preset states in related technologies. This accurately identifies key nodes in parameter acquisition, avoiding parameter distortion caused by deviations in acquisition nodes and ensuring the accuracy of subsequent static friction calculations.

[0082] The specific implementation process is as follows: A high-speed camera continuously captures images of the bubbles on the modified heating surface. The frame rate must meet the requirements for capturing the instantaneous morphology of the bubbles; generally, a high frame rate mode is selected to avoid missing crucial states. The heating power is gradually increased, and the entire process of the bubbles from nucleation and growth to their imminent detachment is observed. During the growth stage, the bubbles will continue to increase in size, and the contact area with the heating surface gradually stabilizes. The process for judging the morphological characteristics of the bubbles about to detach is as follows: the contact area between the bubble and the heating surface no longer expands, the contact point shows a tendency to contract, and the overall shape of the bubble tends to stabilize into a round or elliptical shape.

[0083] Furthermore, to ensure the accuracy of the selected data, the continuous image frames recorded by the high-speed camera were filtered, and the last 1-2 frames before the bubble detached were selected as the measurement basis. The experiment was repeated multiple times, and the bubble morphology data from multiple sets under the same operating conditions were averaged to reduce the error of a single measurement.

[0084] In another implementation, if the rate of increase of the major axis length and / or minor axis length is detected to be within the second growth range, then the bubble is determined to be in a preset state.

[0085] The acquisition process of the size growth rate is as follows: Using the high-speed camera and image analysis software in claim 1, the major axis length Li1 and minor axis length Li2 during the bubble growth process are identified and recorded in real time, and the length growth rate vL1=ΔtΔLi1 (major axis growth rate) and vL2=ΔtΔLi2 (minor axis growth rate) per unit time are calculated, with the time unit being ms.

[0086] The setting of the second growth range conforms to the volume growth law of the bubble. When the bubble is about to detach, the internal pressure and the external flow field pressure tend to be balanced, and the volume no longer increases significantly. Therefore, the growth rate of the long axis and the short axis is at an extremely low level. This range can be adaptively adjusted according to the test conditions, all of which are within the protection scope of this invention.

[0087] The process of setting the second growth range is as follows: The second growth range is the growth rate characteristic of the size of the bubble when it is about to detach. According to the bubble growth law, the length of the major axis and minor axis will increase rapidly during the bubble growth stage. When it is about to detach, the size growth tends to stagnate and the growth rate decreases significantly. In this embodiment, the second growth range is set as follows: the growth rate of the major axis / minor axis length ≤ 0.001 mm / ms. That is, if the growth rate of either the major axis or the minor axis is within this range, the judgment condition can be met.

[0088] The determination process of the above preset state is as follows: When the growth rate of the major axis length and / or minor axis length of the bubble is detected in real time to be within the second growth range, it can be determined that the bubble is in the preset state of near detachment. At this time, the major axis length, minor axis length and bubble movement speed in this state are immediately collected.

[0089] For example, in the early stage of bubble growth, the growth rate of the major axis is vL1=0.008mm / ms and the growth rate of the minor axis is vL2=0.006mm / ms; when the bubble grows to 1.1s, the growth rate of the major axis is vL1=0.0009mm / ms, which is within the second growth range. It is determined that the bubble is in the preset state, and then the parameters are collected.

[0090] In this implementation step, the preset state is determined by the quantitative characteristics of the size growth rate, which provides an observable and quantifiable basis for judgment, avoids the judgment bias caused by subjective observation, and ensures that the judgment results of different testers and different test scenarios are consistent, thereby improving the repeatability of the test.

[0091] As another implementation method, if it is detected that the bubble movement speed increases in the direction perpendicular to the heating surface, then it is determined that the bubble is in a preset state.

[0092] The process of collecting bubble motion velocity is as follows: a high-speed camera and image analysis software are used to identify and calculate the direction and speed of bubble motion in real time. The focus is on monitoring the velocity ug of the bubble perpendicular to the heated surface, which is the core direction of bubble detachment. The horizontal motion velocity can be ignored.

[0093] The process for determining the change in velocity is as follows: During the bubble growth stage, the contact force with the heated surface is relatively large, and the bubble is generally stationary relative to the heated surface, with a velocity ug≈0 perpendicular to the heated surface. When the bubble is about to detach, the resultant force of buoyancy and drag begins to exceed the resultant force of gravity and static friction. The bubble will exhibit a small upward movement perpendicular to the heated surface, and at this time, the velocity in the vertical direction increases from 0, showing a significant velocity increment Δug>0. This determination is based on the force change law of the attached bubble. The increase in velocity is a direct manifestation of the impending disruption of the bubble's force balance and is the core dynamic characteristic of the bubble nearing detachment. No specific velocity threshold needs to be set; only the increasing trend of velocity in the vertical direction needs to be detected. This method is applicable to bubble determination under all working conditions.

[0094] The process for determining the preset state is as follows: When the bubble velocity is detected to increase in the direction perpendicular to the heating surface (i.e., Δug>0), it can be determined that the bubble is in the preset state of near detachment. At this time, the major axis length, minor axis length and bubble velocity in this state are immediately collected.

[0095] For example, before the bubble grows to 1.0s, the speed of its movement in the direction perpendicular to the heated surface is always 0; when it grows to 1.0s, the upward speed of the bubble is detected to be 0.01m / s, showing a significant increase in speed, and the bubble is determined to be in a preset state, and then the parameters are collected.

[0096] Through the above implementation steps, the judgment criteria for the preset state are supplemented from the dimension of motion state, which solves the problem of the single judgment dimension of related technologies. It complements the judgment of morphological features, making the judgment of the preset state more comprehensive and accurate, and effectively avoiding the deviation caused by the single-dimensional judgment.

[0097] As one implementation method, based on the positive correlation between the magnitude of static friction and the ease with which bubbles detach from the surface of the modified sample, the target ease with which bubbles detach from the surface of the modified sample under static friction is determined; if the target ease is greater than the preset ease, the scanning power of the femtosecond laser is reduced or the scanning spacing is increased; if the target ease is less than or equal to the preset ease, the scanning power of the femtosecond laser is increased or the scanning spacing is decreased.

[0098] Specifically, the mapping relationship between static friction and the ease of bubble detachment is established as follows: Based on the bubble motion characteristics of femtosecond laser-modified surfaces, there is a positive correlation between the magnitude of static friction and the ease with which bubbles detach from the modified sample surface. That is, the greater the static friction, the greater the resistance to bubble detachment, and the more difficult it is for the bubble to detach; conversely, the smaller the static friction, the smaller the resistance to bubble detachment, and the easier it is for the bubble to detach. This mapping relationship is quantitative and can be obtained through multiple experimental fittings. In this embodiment, experimental fitting revealed that for every 0.000001 N increase in static friction, the ease of bubble detachment increases by one level.

[0099] Secondly, the process of determining the target difficulty is as follows: Based on the above positive correlation mapping relationship and combined with the calculated static friction force, the target difficulty of the bubble detaching from the surface of the modified sample under the current static friction force is determined.

[0100] For example, in this embodiment, the static friction force FN≈0.00000249N, and based on the fitted mapping relationship, the target difficulty level is determined to be level 3 (medium to difficult).

[0101] Secondly, the process of setting the preset difficulty level is as follows: The preset difficulty level is set according to the actual engineering requirements. In this embodiment, the preset difficulty level is set to level 2 (medium) for the boiling heat transfer requirements of the nuclear reactor heat exchanger, that is, the bubbles need to have medium difficulty in detachment, taking into account both heat transfer efficiency and operational stability.

[0102] Finally, the process parameter optimization and adjustment process is as follows: the target difficulty is compared with the preset difficulty, and the process parameters of femtosecond laser modification are adjusted in a targeted manner based on the comparison results, with the core adjustments being the scanning power and scanning spacing.

[0103] First, if the target difficulty is greater than the preset difficulty, it means that the bubbles are too difficult to detach. It is necessary to reduce the pore density and roughness of the modified surface and reduce the static friction. In this case, reduce the scanning power of the femtosecond laser or increase the scanning interval.

[0104] Second, if the target difficulty is less than or equal to the preset difficulty, it means that the bubble detachment difficulty meets the requirements or is too easy to detach. It is necessary to increase the pore density and roughness of the modified surface and increase the static friction. In this case, the scanning power of the femtosecond laser should be increased or the scanning interval should be reduced.

[0105] For example, in this embodiment, the target difficulty level 3 is greater than the preset difficulty level 2, so the static friction needs to be reduced. Therefore, the scanning power of the femtosecond laser is reduced from the original 50W to 40W, or the scanning spacing is increased from the original 50μm to 60μm.

[0106] In this embodiment, by establishing a quantitative correlation between static friction and the ease of bubble detachment, process optimization no longer relies on experience but is guided by clear quantitative data. This solves the problems of high trial-and-error costs and low efficiency in existing technology process optimization, and achieves precise optimization of the femtosecond laser modification process.

[0107] As one implementation method, if the static friction force is detected to be greater than a preset threshold, the scanning power of the femtosecond laser is reduced or the scanning spacing is increased; the preset threshold is determined based on the reference value of static friction force of bubbles on an unmodified metal surface; if the static friction force is detected to be less than the preset threshold, the scanning power of the femtosecond laser is increased or the scanning spacing is decreased.

[0108] The preset threshold is set with the unmodified surface as a reference, which clarifies the reasonable range of static friction of the modified surface, so that the process optimization has a unified and scientific quantitative judgment standard and avoids the deviation of subjective judgment.

[0109] In the above embodiments, if the static friction force FN is greater than a preset threshold, it indicates that the pore density and roughness of the modified surface are too high, and the bubbles are too difficult to detach. It is necessary to reduce the surface roughness and pore density to decrease the static friction force. Therefore, the scanning power of the femtosecond laser should be reduced or the scanning interval increased to lower the pore density and roughness of the modified surface. If the static friction force FN is less than a preset threshold, it indicates that the pore density and roughness of the modified surface are too low, and the bubbles are too easy to detach. It is necessary to increase the surface roughness and pore density to increase the static friction force. Therefore, the scanning power of the femtosecond laser should be increased or the scanning interval decreased to increase the pore density and roughness of the modified surface.

[0110] For example, in this embodiment, the static friction force of the modified sample is FN≈0.00000249N, which is greater than the preset threshold of 0.00000225N. Therefore, the scanning power of the femtosecond laser is reduced from 50W to 40W, or the scanning spacing is increased from 50μm to 60μm.

[0111] In this implementation step, a preset threshold is set based on the static friction benchmark value of the unmodified metal surface, making the judgment criteria for process optimization more in line with actual engineering needs. At the same time, it realizes a quantitative comparison between modified and unmodified surfaces, further improving the pertinence and scientific nature of process optimization.

[0112] As one implementation method, the surface of the femtosecond laser-modified sample has a porous microstructure, and the geometric dimensions of the porous microstructure are within a preset size range; the material of the femtosecond laser-modified sample is metal; and the test channel is a test channel.

[0113] The material of the femtosecond laser modified sample can be limited to metal, which can meet the material requirements of engineering equipment such as nuclear reactor fuel assemblies and heat exchangers, including but not limited to stainless steel, titanium alloy, zirconium alloy and other metal and alloy materials. In this embodiment, 304 stainless steel is used, which meets the material requirements of nuclear reactor heat exchangers.

[0114] The surface microstructure of the aforementioned femtosecond laser-modified sample can be defined as having a porous microstructure. This porous microstructure is prepared by femtosecond laser subtractive processing and is the core structure affecting the static friction of bubbles. The geometric dimensions of the porous microstructure are within a preset size range. Based on the process characteristics and engineering requirements of femtosecond laser modification technology, this preset size range is set to 20μm to 100μm, including core geometric parameters such as pore diameter and depth. In this embodiment, the pore diameter of the porous microstructure on the sample surface is 40μm and the depth is 60μm, which is within the preset size range.

[0115] In some embodiments, the preset size range can be from 20 μm to 100 μm. The preset size range of 20 μm to 100 μm is the microstructure size that can be achieved by femtosecond laser modification technology. At the same time, the pore microstructure within this size range can effectively control the detachment characteristics of bubbles. Pores that are too small cannot form effective nucleation cavities, while pores that are too large will cause bubbles to be trapped, neither of which can achieve efficient heat transfer control.

[0116] The test channel can be limited to a rectangular channel. The rectangular channel has a rectangular cross-section, which is suitable for the common flow channel structure in engineering equipment. At the same time, the rectangular channel can ensure the stability and uniformity of the working fluid flow and avoid force field interference caused by irregular flow channel shape. In this embodiment, the cross-sectional specifications of the test channel are 100mm×50mm, which meets the test requirements.

[0117] In this embodiment, by clearly defining the core characteristics of the test object and the test environment, the test environment is highly matched with actual engineering scenarios such as nuclear reactor fuel assemblies and heat exchangers, which greatly enhances the engineering application value of static friction test results. At the same time, the core test conditions are unified, avoiding test result deviations caused by differences in sample material, microstructure size, and channel type, making the results of different tests comparable and universal, which facilitates the promotion and application of this method in the industry.

[0118] Through the above various implementation methods, the core of the process for determining the static friction force of bubbles on the surface of femtosecond laser modified samples includes the construction of the test environment, bubble generation, acquisition of preset state parameters, calculation of static friction force, multi-dimensional determination of preset state, process optimization based on static friction force, and characteristic limitation of test object and environment.

[0119] Therefore, by establishing a standardized experimental environment, accurately determining the preset state, and performing scientific calculations based on force balance, the static friction force of bubbles on the surface of femtosecond laser-modified samples was quantitatively determined. At the same time, a direct correlation between static friction force and process optimization was established, providing a clear quantitative basis for adjusting modification process parameters and solving the core pain points of related technologies.

[0120] This application effectively solves the technical problems in the prior art, namely the lack of a precise method for testing and calculating the static friction force of bubbles adapted to the surface characteristics of femtosecond laser modification, and the inability to quantify this core parameter to guide process optimization. By placing the femtosecond laser-modified sample in a test channel perpendicular to the ground and controlling the working fluid to flow vertically upwards, a standardized test environment matching the actual stress scenario of bubbles is constructed. This environment is adapted to the microscopic pore structure characteristics of the femtosecond laser-modified surface, overcoming the limitation of existing technologies that can only roughly analyze the stress on bubbles on smooth surfaces. Simultaneously, by determining the preset state of the bubble nearing detachment and accurately capturing the major and minor axis lengths and bubble velocity in this critical state, real and effective core parameters are provided for static friction force calculation. This is the first time that the static friction force of bubbles on the surface of a femtosecond laser-modified sample has been quantitatively determined, filling a technical gap in this field.

[0121] Furthermore, by breaking down the static friction calculation into determining the equivalent diameter, quantitatively calculating each force, and solving for force equilibrium, the static friction calculation is supported by clear physical theory and mathematical models, ensuring the accuracy and reliability of the calculation results. This allows the static friction to truly reflect the actual obstruction effect of the modified surface on bubbles. Simultaneously, by providing quantitative criteria for determining the preset state through three dimensions—contact area, size growth rate, and change in motion speed—subjective bias in parameter acquisition is avoided, ensuring the authenticity of the basic parameters and further improving the accuracy of the static friction calculation.

[0122] Furthermore, this method establishes a direct control logic for static friction and femtosecond laser modification process parameters. By adjusting the magnitude of static friction or a preset threshold, targeted adjustments to scanning power and scanning spacing can be achieved, freeing process optimization from reliance on experience. This significantly reduces R&D trial-and-error costs and improves process optimization efficiency. At the same time, it clarifies the core characteristics of the test object and environment, ensuring that the test results are highly matched with actual engineering scenarios such as nuclear reactor fuel assemblies and heat exchangers. This enhances the engineering application value of the test results and promotes the standardization and engineering development of femtosecond laser modification technology in high-end equipment manufacturing.

[0123] To achieve the above functions, the device for determining the static friction force of surface bubbles in a femtosecond laser-modified sample includes hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art will readily recognize that, based on the algorithmic steps of the examples described in conjunction with the embodiments disclosed herein, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0124] This disclosure also provides an embodiment such as Figure 6 The device shown is for determining the static friction force of surface bubbles in a femtosecond laser-modified sample. The device includes a control unit 61, a bubble generation unit 62, and a determination unit 63.

[0125] The control unit 61 is configured to place the femtosecond laser-modified sample as a heating surface in a test channel arranged vertically to the ground, and control the working fluid in the test channel to flow in an upward direction perpendicular to the ground.

[0126] The bubble generating unit 62 is configured to apply heating power to the femtosecond laser-modified sample to generate bubbles on the heated surface of the femtosecond laser-modified sample.

[0127] The determining unit 63 is configured to determine the major axis length and minor axis length of the bubble when the bubble is in a preset state, as well as the bubble's movement speed; the preset state characterizes the shape and movement state of the bubble when it is about to detach from the heating surface.

[0128] The determining unit 63 is also configured to determine the static friction force experienced by the bubble in a preset state based on the major axis length, minor axis length and bubble movement speed.

[0129] In one embodiment, the determining unit 63 is specifically configured to: determine the equivalent diameter of the bubble based on the major axis length and the minor axis length; determine the buoyancy force on the bubble in a preset state based on the equivalent diameter of the bubble, the liquid phase density of the bubble, and the gravitational acceleration; determine the drag force on the bubble in the preset state based on the equivalent diameter of the bubble, the liquid phase density of the bubble, the dynamic viscosity of the liquid phase, and the relative velocity of the gas and liquid phases; determine the gravity of the bubble in the preset state based on the gas phase density of the bubble and the equivalent diameter of the bubble; and determine the static friction force based on the force balance between buoyancy, drag force, gravity, and static friction force.

[0130] In another embodiment, the determining unit 63 is further configured to: if the area of ​​the contact region between the heating surface and the bubble is detected to increase within a first growth range, then determine that the bubble is in a preset state.

[0131] In another embodiment, the determining unit 63 is further configured to: if the length growth rate of the major axis length and / or the minor axis length is detected to be within a second growth range, then determine that the bubble is in a preset state.

[0132] In another embodiment, the determining unit 63 is further configured to determine that the bubble is in a preset state if it is detected that the bubble movement speed increases in the direction perpendicular to the heating surface.

[0133] In another embodiment, the control unit 61 is further configured to: determine the target difficulty of the bubble detaching from the modified sample surface under static friction force based on the positive correlation between the magnitude of static friction force and the ease with which the bubble detaches from the modified sample surface; reduce the scanning power of the femtosecond laser or increase the scanning spacing when the target difficulty is greater than the preset difficulty; and increase the scanning power of the femtosecond laser or decrease the scanning spacing when the target difficulty is less than or equal to the preset difficulty.

[0134] In another embodiment, the control unit 61 is further configured to: if the static friction force is detected to be greater than a preset threshold, reduce the scanning power of the femtosecond laser or increase the scanning interval; the preset threshold is determined based on a reference value of static friction force of bubbles on an unmodified metal surface; if the static friction force is detected to be less than the preset threshold, increase the scanning power of the femtosecond laser or decrease the scanning interval.

[0135] In another embodiment, the surface of the femtosecond laser-modified sample has a porous microstructure, the geometric dimensions of which are within a preset size range; the material of the femtosecond laser-modified sample is metal; and the test channel is a test channel.

[0136] Regarding the apparatus in the above embodiments, the specific manner in which each unit module performs its operations has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0137] Figure 7 This is a schematic diagram of an electronic device provided in this application. (For example...) Figure 7 The electronic device 70 may include at least one processor 701 and a memory 703 for storing processor-executable instructions. The processor 701 is configured to execute the instructions in the memory 703 to implement the method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample as described in the following embodiments.

[0138] In addition, the electronic device 70 may also include a communication bus 702, at least one communication interface 704, an input device 706, and an output device 705.

[0139] The processor 701 may be a processor (central processing unit, CPU), a microprocessor unit, an ASIC, or one or more integrated circuits for controlling the execution of the program of the present application.

[0140] The communication bus 702 may include a path for transmitting information between the aforementioned components.

[0141] The communication interface 704 uses any transceiver-like device for communicating with other devices or communication networks, such as Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc.

[0142] Input device 706 is used to receive input signals and output device 705 is used to output signals.

[0143] The memory 703 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital versatile optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto. The memory may exist independently and be connected to the processing unit via a bus. The memory may also be integrated with the processing unit.

[0144] The memory 703 stores instructions for executing the scheme of this application, and the processor 701 controls the execution. The processor 701 executes the instructions stored in the memory 703 to implement the functions of the method of this application.

[0145] In a specific implementation, as one example, the processor 701 may include one or more CPUs, for example... Figure 7 CPU0 and CPU1 in the CPU.

[0146] In a specific implementation, as one example, the electronic device 70 may include multiple processors, such as... Figure 7Processors 701 and 707 are mentioned. Each of these processors can be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. A processor here can refer to one or more devices, circuits, and / or processing cores used to process data (such as computer program instructions).

[0147] The electronic device is as follows Figure 7 The diagram includes a processor 701 and a memory 703 for storing executable instructions of the processor 701; wherein the processor 701 is configured to execute executable instructions to implement the method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample as described in any of the possible embodiments above. Furthermore, it achieves the same technical effect, and to avoid repetition, will not be described further here.

[0148] This application also provides a computer-readable storage medium. When the instructions in the computer-readable storage medium are executed by the processor of a device or electronic device for determining the static friction force of surface bubbles in a femtosecond laser-modified sample, the device or electronic device can perform the method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample as described in any of the above possible embodiments. The same technical effects can be achieved, and to avoid repetition, further details are omitted here.

[0149] This application also provides a computer program product, including a computer program or instructions, which are executed by a processor as described in any of the above possible embodiments, for a method to determine the static friction force of surface bubbles in a femtosecond laser-modified sample. This method achieves the same technical effect and will not be repeated here to avoid repetition.

[0150] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0151] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for determining the static friction force of bubbles on the surface of a femtosecond laser-modified sample, characterized in that, The method includes: The femtosecond laser-modified sample is placed as the heating surface in a test channel arranged vertically to the ground, and the working fluid in the test channel is controlled to flow in an upward direction perpendicular to the ground. A heating power is applied to the femtosecond laser-modified sample to generate bubbles on the heated surface of the femtosecond laser-modified sample; The major axis length and minor axis length of the bubble in a preset state, as well as the bubble's movement speed, are determined; the preset state characterizes the shape and movement state of the bubble as it approaches detachment from the heating surface. The static friction force experienced by the bubble in the preset state is determined based on the length of the major axis, the length of the minor axis, and the bubble's movement speed.

2. The method according to claim 1, characterized in that, The step of determining the static friction force experienced by the bubble in the preset state based on the major axis length, the minor axis length, and the bubble movement velocity includes: The equivalent diameter of the bubble is determined based on the length of the major axis and the length of the minor axis. The buoyancy force on the bubble in the preset state is determined based on the equivalent diameter of the bubble, the liquid phase density of the bubble, and the gravitational acceleration. Furthermore, the drag force experienced by the bubble in the preset state is determined based on the equivalent diameter of the bubble, the liquid phase density of the bubble, the liquid phase dynamic viscosity, and the relative velocity of the gas and liquid phases. Furthermore, the gravity of the bubble in the preset state is determined based on the gas phase density of the bubble and the equivalent diameter of the bubble; The static friction force is determined based on the force balance between the buoyancy, the drag, the gravity, and the static friction force.

3. The method according to claim 1, characterized in that, The method further includes: If the area of ​​the contact region between the heating surface and the bubble is detected to increase within a first growth range, then the bubble is determined to be in the preset state.

4. The method according to claim 1, characterized in that, The method further includes: if the length growth rate of the major axis and / or the minor axis is detected to be within a second growth range, then the bubble is determined to be in the preset state.

5. The method according to claim 1, characterized in that, The method further includes: if the bubble's movement speed is detected to increase in a direction perpendicular to the heating surface, then the bubble is determined to be in the preset state.

6. The method according to any one of claims 1 to 5, characterized in that, The method further includes: Based on the positive correlation between the magnitude of static friction and the ease with which bubbles detach from the surface of the modified sample, the target ease with which the bubbles detach from the surface of the modified sample under the static friction is determined. If the difficulty of the target is greater than the preset difficulty, reduce the scanning power of the femtosecond laser or increase the scanning interval; If the target difficulty is less than or equal to the preset difficulty, increase the scanning power of the femtosecond laser or decrease the scanning spacing.

7. The method according to any one of claims 1 to 5, characterized in that, The method further includes: If the static friction force is detected to be greater than a preset threshold, the scanning power of the femtosecond laser is reduced or the scanning interval is increased; the preset threshold is determined based on the reference value of the static friction force of bubbles on an unmodified metal surface. If the static friction force is detected to be less than the preset threshold, the scanning power of the femtosecond laser is increased or the scanning spacing is decreased.

8. The method according to any one of claims 1 to 5, characterized in that, The surface of the femtosecond laser-modified sample has a porous microstructure, and the geometric dimensions of the porous microstructure are within a preset size range; the material of the femtosecond laser-modified sample is metal; the test channel is a test channel.

9. An apparatus for determining the static friction force of surface bubbles in a femtosecond laser-modified sample, used for performing the method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample as described in any one of claims 1 to 7, characterized in that, The device includes: The control unit is configured to place the femtosecond laser-modified sample as a heating surface in a test channel arranged vertically to the ground, and control the working fluid in the test channel to flow in an upward direction perpendicular to the ground. The bubble generating unit is configured to apply heating power to the femtosecond laser-modified sample to generate bubbles on the heated surface of the femtosecond laser-modified sample. The determining unit is configured to determine the major axis length and minor axis length of the bubble when the bubble is in a preset state, and the bubble movement speed; the preset state characterizes the shape and movement state of the bubble when it is about to detach from the heating surface. The determining unit is further configured to determine the static friction force experienced by the bubble in the preset state based on the length of the major axis, the length of the minor axis, and the bubble's movement speed.

10. A computer-readable storage medium storing instructions thereon, characterized in that, When the instructions in the computer-readable storage medium are executed by the processor of the electronic device, the electronic device is able to perform the method for determining the static friction force of surface bubbles in a femtosecond laser-modified sample as described in any one of claims 1-7.

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