A model calculation method for the size of the contact angle between a leaf vein portion on a tobacco leaf surface and a liquid drop

Abstract

The application discloses a model calculation method for the contact angle of a tobacco leaf surface vein part and a liquid drop, and belongs to the technical field of tobacco raw material detection and analysis, and comprises the following steps: observing the micro-morphology of the tobacco leaf surface vein part by using a scanning electron microscope; establishing a vein two-dimensional model according to the morphological characteristic parameters of the tobacco leaf surface vein part; based on a Cassie-Baxter model, establishing a calculation expression of a tobacco leaf vein part wetting contact angle prediction model to predict the contact angle of the tobacco leaf vein part, and obtaining a predicted contact angle; performing finite element simulation on the vein two-dimensional model to obtain a simulated contact angle; measuring the contact angle of the tobacco leaf vein part through an experiment, obtaining an experimental contact angle and calculating a Young contact angle; and performing fitting error analysis on the predicted contact angle and the simulated contact angle. The application can realize the rapid calculation of the predicted contact angle of the tobacco leaf vein part, provide help for industrial cigarette production processes, and optimize the taste of cigarettes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tobacco raw material detection and analysis, and particularly relates to a model calculation method for contact angle size between a leaf vein part on a tobacco leaf surface and a liquid drop. BACKGROUND

[0002] Wetting performance is a problem that needs to be considered in many fields, such as waterproofing, decontamination, rust prevention, corrosion prevention, etc. In recent years, many scholars have analyzed the wetting properties of various plants and found that the main factors affecting the wetting performance are the surface wax, i.e. chemical composition, and the surface microstructure, which can change the contact angle of the liquid drop on the surface. The larger the contact angle, the stronger the hydrophobicity. For example, the surface microstructure of a lotus leaf is in the form of papillae, which can greatly increase the contact angle of the water drop on the surface of the lotus leaf. In addition, a layer of plant wax on the surface also increases the contact angle to a certain extent. The larger the contact angle, the more circular the shape, and the smaller the adhesion on the surface, so the liquid drop can move freely on the surface.

[0003] Many scholars have compiled the wetting characteristics and topography of more than 200 plant leaves, discussed the diversity of the surface morphology of different plant leaves and its role in determining the wetting characteristics, and also discussed how to design and biomimetic surfaces for potential technical applications such as self-cleaning, anti-fouling, and reduction of particle adhesion. The models for the contact angle include the Young's model and the Wenzel model, etc. The Young's model is suitable for ideal cases where the surface is smooth, and the Wenzel model makes the water drop and the microstructure fully contact. In the production process of tobacco products, the wetting performance of tobacco leaves affects key indicators such as the taste, mouthfeel, and tar content of cigarettes. Therefore, detecting the wetting performance of tobacco leaves is an important step to ensure the quality of tobacco products. At present, there is a blank in the theoretical prediction model for the contact angle of the wetting performance of tobacco leaves. How to predict the wetting performance and moisture content of tobacco leaves in the production process and optimize the process according to the wetting of tobacco leaves has become an important problem. SUMMARY

[0004] In view of the above, the present application aims to provide a model calculation method for the contact angle size between a leaf vein part on a tobacco leaf surface and a liquid drop, to solve the problem of the blank in the theoretical prediction model for the contact angle of the wetting performance of tobacco leaves, and the inability to predict the wetting performance and moisture content of tobacco leaves in the production process.

[0005] The technical solution adopted by the present application is as follows:

[0006] The present application provides a model calculation method for the contact angle size between a leaf vein part on a tobacco leaf surface and a liquid drop, comprising the following steps:

[0007] Step 1: observing the microtopography of the leaf vein part on the tobacco leaf surface using a scanning electron microscope and recording the topographic feature parameters of the leaf vein part on the tobacco leaf surface.

[0008] Step 2: According to the morphological characteristic parameters of the leaf vein part on the surface of the tobacco leaf, a leaf vein two-dimensional model is established, wherein the leaf vein two-dimensional model includes a planar base, a leaf vein, and a water droplet, the planar base is rectangular, the leaf vein is established on the planar base, and the leaf vein is in a semi-cylindrical shape, the radius of the semi-cylindrical leaf vein is set as R, the length is set as L, and the difference between the radius of the leaf vein and the droplet immersion depth is set as h;

[0009] Step 3: Based on the Cassie-Baxter model, a calculation expression of the tobacco leaf vein part immersion contact angle prediction model is established to predict the contact angle of the tobacco leaf vein part, and a predicted contact angle θ c is obtained;

[0010] Step 4: Finite element simulation is performed on the leaf vein two-dimensional model to obtain the size of the simulated contact angle;

[0011] Step 5: The contact angle of the tobacco leaf vein part is measured through experiments, the experimental contact angle is obtained, and the Young contact angle θ Y is calculated;

[0012] Step 6: Based on the Young contact angle θ Y and the calculation expression of the tobacco leaf vein part immersion contact angle prediction model, fitting error analysis is performed on the obtained predicted contact angle θ c and the simulated contact angle.

[0013] Optionally, in step S1, the tobacco leaf includes a leaf vein part and a mesophyll part, and the contact angles of the leaf vein part and the mesophyll part should satisfy the following conditions:

[0014] θ c > θ Y ;

[0015] Wherein, θ c is the predicted contact angle of the leaf vein part and the mesophyll part under the Cassie-Baxter model, and θ Y is the Young contact angle of the tobacco leaf.

[0016] Optionally, in step S2, the immersion area S1 and the difference h between the leaf vein radius R and the droplet immersion depth should satisfy the following conditions:

[0017] S1 < S2;

[0018] 0 < h < R;

[0019] Wherein, S1 represents the area of the droplet immersing the leaf vein part, S2 represents the projection area of the leaf vein, R represents the leaf vein radius, h represents the difference between the leaf vein radius and the droplet immersion depth, the ratio of S1 to S2 is greater than 1, and h is greater than 0.

[0020] Optionally, in step 3, in the step of establishing a calculation expression of a tobacco vein portion wicking contact angle prediction model, among the factors affecting the wicking contact angle, the local influencing factors include the radius of the vein and the difference h between the vein radius R and the droplet wicking depth, that is, the percentage f of the contact area of the droplet with the tobacco leaf to the total area, and the calculation of the solid-liquid contact area percentage f includes the following steps:

[0021] Calculate the contact arc length l of the droplet with the vein:

[0022] Calculate the contact area S1 of the droplet with the vein:

[0023] Calculate the projected area S2 of the vein: S2 = 2RL;

[0024] Wherein, l represents the arc length, R represents the radius of the vein, h represents the difference between the vein radius and the droplet wicking depth, L represents the length of the vein, S1 represents the contact area of the droplet with the vein, and S2 represents the projected area of the vein.

[0025] Optionally, the contact area of the droplet with the vein obtained is divided by the projected area of the vein to obtain the solid-liquid contact area percentage f, which is substituted into the Cassie-Baxter model to obtain the corresponding prediction contact angle expression:

[0026]

[0027] Wherein, R represents the radius of the vein, h represents the difference between the vein radius and the droplet wicking depth, S1 represents the contact area of the droplet with the vein, S2 represents the projected area of the vein, and θ c is the predicted contact angle of the vein portion and the mesophyll portion under the Cassie-Baxter model, and θ Y is the Young contact angle of the tobacco leaf.

[0028] Optionally, step 5 further includes calculating the Young contact angle θ Y based on the experimental contact angle, specifically including:

[0029] The surface tension γ s of the tobacco leaf is determined by the two-liquid method, and the surface tension includes a polar component and a non-polar component, and the expression is:

[0030]

[0031] Wherein, the superscript P represents the polar part, and D represents the non-polar part;

[0032] Based on the surface tension γ l of the droplet, the solid-liquid interfacial tension is calculated by Fowkes method, denoted as γ sl , and the expression is:

[0033]

[0034] According to the calculated surface tension of tobacco leaf gamma s , the surface tension of the droplet gamma l And the solid-liquid interfacial tension gamma sl The values of the three surface tensions, the Young contact angle theta of different tobacco leaves is calculated Y Size.

[0035] Optionally, the surface tension of the droplet is the surface tension of water and diiodomethane, respectively.

[0036] The present application can quickly obtain the predicted contact angle of the vein part by Cassie-Baxter model, and facilitate the prediction of the contact angle size, so as to judge the wetting performance of tobacco leaf, optimize the process during production, and make up for the blank of theoretical derivation in contact angle.

[0037] The present application establishes a two-dimensional model of the semi-cylindrical vein part of tobacco leaf according to the microstructure of tobacco leaf surface, and proposes a calculation expression of the wetting contact angle prediction model of the vein part of tobacco leaf; compared with the traditional prediction of the overall contact angle of plant leaves, the present application is small to the prediction of local topography, and the corresponding finite element simulation is carried out to provide corresponding reliability for theoretical prediction. The expressions of the contact area of the droplet and the vein, the projection area of the vein, the solid-liquid interfacial tension and the solid-liquid contact area ratio are proposed, which can realize the rapid calculation of the predicted contact angle of the vein part of tobacco leaf, provide help for industrial cigarette production process, and optimize the taste of cigarette.

[0038] Compared with the traditional calculation model, the calculation results obtained by the model of the present application can be used to study the wetting performance of specific plants, and the surface tension of plant leaves is obtained to obtain the corresponding Young contact angle. For example, the present application mainly analyzes the wetting performance of the vein part of tobacco leaf, the predicted contact angle calculated by the model applied has small size error with the actual contact angle, and is more consistent with the data of finite element simulation, which shows that the model proposed in the present application has relatively high accuracy.

[0039] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments thereof, with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described below with reference to the drawings, wherein:

[0041] Figure 1 The model calculation method flow chart of the size of the contact angle between the vein part of the tobacco leaf surface and the droplet in an embodiment of the present application;

[0042] Figure 2 A schematic diagram of factors affecting the contact angle of the leaf vein part of the tobacco leaf surface is shown in Figure 1.

[0043] Figure 3 A schematic diagram of part of the leaf vein part in the two-dimensional model of the tobacco leaf is shown in Figure 2.

[0044] Figure 4 A schematic diagram of the curve for predicting the contact angle of the selected three kinds of tobacco leaf using the established theoretical model is shown in Figure 3.

[0045] Figure 5 A schematic diagram of the fitting curve of the theoretical prediction curve of the selected tobacco leaf and the finite element simulation result is shown in Figure 4. DETAILED DESCRIPTION

[0046] Embodiments of the present application will be described in detail below, examples of which are shown in the accompanying drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be interpreted as a limitation of the present application.

[0047] The existing technology is still in a blank state for the contact angle theoretical prediction model of the tobacco leaf infiltration performance. How to predict the infiltration performance and the water content of the tobacco leaf in the production process, and optimize the process according to the tobacco leaf infiltration, has become a relatively important problem. The present application establishes a leaf vein two-dimensional model for the micro surface structure of the tobacco leaf, and proposes a calculation expression of the leaf vein part infiltration contact angle prediction model of the tobacco leaf, which can realize the rapid calculation of the predicted contact angle of the leaf vein part of the tobacco leaf, provide help for the industrial cigarette production process, and optimize the taste of the cigarette.

[0048] The present application provides an embodiment of a model calculation method for the size of the contact angle between the leaf vein part of the tobacco leaf surface and the liquid drop, specifically as shown in Figure 1, which comprises the following steps: Figure 1

[0049] Step 1: The micro-morphology of the leaf vein part of the tobacco leaf surface is observed by using a scanning electron microscope, and the morphological characteristic parameters of the leaf vein part of the tobacco leaf surface are recorded; wherein the magnification, focal length, brightness and other parameters are adjusted until a clear leaf vein image is obtained on the display screen of the scanning electron microscope.

[0050] It should be noted that, as shown in Figure 2, Figure 2 ​As shown in the figure, the main process of the tobacco leaf vein part contact angle prediction is shown, the factors affecting the contact angle size after applying the Cassie-Baxter model under the known surface microstructure are listed, and the composition is simplified appropriately for the convenience of derivation and calculation, and the specific assumptions are as follows: the influence of micro-morphology is considered first when studying the size of the contact angle, and the influence of the surface wax layer is not considered; the micro-morphology of the vein presents a relatively regular strip under the scanning electron microscope, which is simplified as a homogeneous semi-cylindrical shape.

[0051] Step 2: Establish a two-dimensional model of the leaf vein according to the morphological characteristic parameters of the leaf vein part of the tobacco leaf, wherein the two-dimensional model of the leaf vein includes a plane base, a leaf vein, and a water droplet, the plane base is rectangular, the leaf vein is established on the plane base, and the leaf vein is semi-cylindrical, the radius of the semi-cylindrical leaf vein is set as R, the length is set as L, the difference between the radius of the leaf vein and the immersion depth of the liquid droplet is set as h, and the Young contact angle of different tobaccos is set as θ Y ; wherein, on the plane base, the center line of the leaf vein is drawn, the number, spacing and length of the leaf vein are determined, and a drawing software (such as Adobe Illustrator, AutoCAD or Python matplotlib library) is used to draw a straight line or a curve of the leaf vein.

[0052] Specifically, the micro-morphology of the leaf vein presents a relatively regular strip under the electron microscope, which is simplified as a homogeneous semi-cylindrical shape; the calculation model of the simplified contact angle of the leaf vein part of the tobacco leaf is as shown in Figure 3 , and part of the leaf vein is taken, and the number of leaf veins is 5. For different tobaccos, the diameter of the leaf vein can be changed as a general model, which is a plane model containing a base, a leaf vein and a liquid droplet, wherein the factors affecting the contact angle are the size of the Young contact angle, the local influencing factors include the radius of the leaf vein and the difference between the radius of the leaf vein and the immersion depth of the liquid droplet, and finally the percentage of the contact area of the liquid droplet with the tobacco leaf to the total area. The contact area percentage of the leaf vein part needs to calculate the following physical parameters: the contact arc length of the liquid droplet with the leaf vein, the area of the liquid droplet in contact with the leaf vein, and the projection area of the leaf vein.

[0053] Step 3: Based on the Cassie-Baxter model, a calculation expression of the tobacco leaf vein part immersion contact angle prediction model is established to predict the contact angle of the tobacco leaf vein part, and the predicted contact angle θ c ; the Cassie-Baxter model is a theoretical model for describing the liquid contact angle on a rough surface or a composite surface.

[0054] It should be noted that the Cassie-Baxter model is used instead of the Wenzel model for the contact angle because the roughness factor r is involved in the Wenzel model, and in practice, the roughness factor r is generally greater than 1 for the tobacco leaf surface or other plant surfaces, which leads to a decrease in the predicted contact angle with the increase of the roughness when the measured object is hydrophilic, which is contrary to the fact that the roughness can increase the contact angle, so the Wenzel model has disadvantages in predicting the contact angle of hydrophilic substances, while the Cassie-Baxter model does not cause such a situation and is closer to the actual situation.

[0055] Step 4: Finite element simulation is performed on the vein two-dimensional model to obtain the simulation contact angle size; specifically, the finite element software is used to divide the grid of the vein two-dimensional model, the surface tension, contact angle and other parameters between the droplet and the vein are defined, the simulation is run in the finite element software, the wetting behavior of the droplet on the vein surface is observed, and the post-processing tool of the finite element software is used to analyze the simulation results and extract the contact angle data of the contact area between the droplet and the vein.

[0056] Step 5: The contact angle of the tobacco vein part is measured through experiments to obtain the experimental contact angle and calculate the Young contact angle θ Y ;

[0057] Step 6: Based on the calculation expression of the Young contact angle θ Y and the prediction model of the wetting contact angle of the tobacco vein part, the fitting error analysis is performed on the obtained prediction contact angle θ c and the simulation contact angle.

[0058] In the embodiment of the present application, in step S1, the tobacco leaf includes a vein part and a mesophyll part, and the contact angles of the vein part and the mesophyll part θ c should satisfy the following conditions:

[0059] θ c > θ Y ;

[0060] Wherein, θ c is the prediction contact angle of the vein part and the mesophyll part under the Cassie-Baxter model, and θ Y is the Young contact angle of the tobacco leaf.

[0061] In the embodiment of the present application, in step S2, the conditions that the wetting area S1 and the difference h between the vein radius R and the droplet wetting depth should satisfy are as follows:

[0062] S1 < S2;

[0063] 0 < h < R;

[0064] Wherein, S1 represents the area of the droplet infiltrating the vein part of the leaf, S2 represents the projected area of the vein, R represents the radius of the vein, h represents the difference between the radius of the vein and the droplet infiltration depth, the ratio of S1 to S2 is greater than 1, and h is greater than 0.

[0065] In the embodiment of the present application, in step 3, in the step of establishing the calculation expression of the leaf vein part infiltration contact angle prediction model, among the factors affecting the infiltration contact angle, the local influencing factors include the radius R of the vein and the difference h between the radius R of the vein and the droplet infiltration depth, that is, the percentage f of the total area of the droplet contact area with the tobacco leaf, and the calculation of the solid-liquid contact area percentage f includes the following steps:

[0066] The droplet and vein contact arc length l is calculated as follows:

[0067] The droplet and vein contact area S1 is calculated as follows:

[0068] The projected area S2 of the vein is calculated as follows: S2 = 2RL;

[0069] Wherein, l represents the arc length, R represents the radius of the vein, h represents the difference between the radius of the vein and the droplet infiltration depth, L represents the length of the vein, S1 represents the droplet and vein contact area, and S2 represents the projected area of the vein.

[0070] In the embodiment of the present application, the obtained droplet and vein contact area and the projected area of the vein are taken as a ratio to obtain the solid-liquid contact area percentage f, which is substituted into the Cassie-Baxter model to obtain the corresponding predicted contact angle c Expression:

[0071]

[0072] Wherein, R represents the radius of the vein, h represents the difference between the radius of the vein and the droplet infiltration depth, S1 represents the droplet and vein contact area, S2 represents the projected area of the vein, and c is the predicted contact angle of the vein part and the mesophyll part under the Cassie-Baxter model, and Y is the Young contact angle of the tobacco leaf.

[0073] After the contact angle prediction expression is determined, the Young contact angle Y of the tobacco leaf is determined. Y The Young contact angle Y is mainly related to the surface tension of the solid, the surface tension of the droplet, and the surface tension between the solid and the liquid, and the expression is as follows: The liquid drop is water, the surface tension of water in air is 72.8 mN / m (20 DEG C), the surface tension of the tobacco leaf is determined by mainly using a two-liquid method, the surface free energy of the solid is estimated by measuring the contact angle of the liquid on the solid surface, in general, the surface free energy of the solid is divided into a polar part and a non-polar part, the polar energy and the non-polar energy of the solid surface can be obtained by measuring the contact angles of two liquids on the solid surface, and the liquid drops are water and diiodomethane.

[0074] In the embodiment of the present application, step 5 further comprises calculating the Young contact angle based on the experimental contact angle, and specifically comprises:

[0075] The surface tension of the tobacco leaf is determined by a two-liquid method s , the surface tension includes a polar component and a non-polar component, and the expression is: wherein the superscript P represents the polar part, and D represents the non-polar part;

[0076] Based on the surface tension of the liquid drop l , the solid-liquid interfacial tension is calculated by using the Fowkes method, denoted as sl , and the expression is:

[0077] According to the values of the calculated s , the surface tension of the liquid drop l and the solid-liquid interfacial tension sl , the Young contact angle Y of different tobacco leaves is calculated.

[0078] In the embodiment of the present application, the surface tension of the liquid drop l is the surface tension of water and diiodomethane, wherein the surface tension of diiodomethane is 50.8 mN / m.

[0079] The known three quantities l , γ s and γ sl are substituted into the Young equation cos θ Y , the Young contact angle corresponding to different tobacco leaves is solved, and then the solid-liquid ratio fraction f is determined. In the vein part, the predicted contact angle value changes with the change of the variables h and R, in a specific implementation of the present application, the above model is used for contact angle prediction in the vein part, and the following data are obtained for one kind of tobacco leaf:

[0080] When the value of h / R is 0.0, the predicted contact angle c is 70.83 DEG ;

[0081] When the value of h / R is 0.1, the predicted contact angle c= 77.96°;

[0082] When the value of h / R is 0.2, the predicted contact angle θ c = 84.93°;

[0083] When the value of h / R is 0.3, the predicted contact angle θ c = 91.90°;

[0084] When the value of h / R is 0.4, the predicted contact angle θ c = 99.01°;

[0085] When the value of h / R is 0.5, the predicted contact angle θ c = 106.43°;

[0086] When the value of h / R is 0.6, the predicted contact angle θ c = 114.38°;

[0087] When the value of h / R is 0.7, the predicted contact angle θ c = 123.19°;

[0088] When the value of h / R is 0.8, the predicted contact angle θ c = 133.52°;

[0089] When the value of h / R is 0.9, the predicted contact angle θ c = 146.97°;

[0090] When the value of h / R is 1.0, the predicted contact angle θ c = 180.00°.

[0091] It can be found from Figure 4 that the predicted contact angle θ c is positively correlated with h / R, the greater h / R is, the greater the predicted contact angle θ c is, the greater h / R is, the smaller the solid-liquid area fraction f is, so it can be concluded that the predicted contact angle θ c obtained by Cassie-Baxter model is inversely proportional to the solid-liquid area fraction f, by changing the value of h / R to change the size of the predicted contact angle θ c , to control the degree of wettability, which provides a feasible method for industrial cigarette production process.

[0092] After the theoretical result is obtained, a two-dimensional model of the vein is established on the finite element simulation software, parameters are set, and a time diagram of the water drop infiltration in the vein at different moments is recorded, the value of h / R is obtained according to the infiltration depth, the contact angle of the water drop at different moments is measured by using the ImageJ software, the state of the water drop at multiple moments is taken, the simulation data and the theoretical prediction contact angle value θ c are combined, and the fitting curve of both is obtained, as shown in Figure 5 .

[0093] The calculation result obtained by using the model of the present application can be used to study the infiltration performance of specific plants, and the surface energy of the plant leaf is obtained, and then the corresponding Young contact angle is solved. The present application mainly analyzes the infiltration performance of the vein part of the tobacco leaf, the predicted contact angle obtained by the model calculation has a small error with the actual contact angle, and is more consistent with the finite element simulation data, and has a relatively high accuracy.

[0094] The above embodiment shown in the drawings details the structure, features and effect of the present application, but the above is only a preferred embodiment of the present application, and it should be noted that the technical features involved in the above embodiment and preferred mode can be reasonably combined and matched into various equivalent schemes by those skilled in the art without departing from, changing the design idea and technical effect of the present application. Therefore, the present application is not limited by the drawings shown in the drawings, and any change or modification made according to the concept of the present application, or any equivalent embodiment within the scope of the present application, shall be within the scope of the present application.

Claims

1. A model calculation method for the contact angle between the vein portion of the tobacco leaf surface and the droplet, characterized in that: The following steps are involved: Step 1: Use a scanning electron microscope to observe the microscopic morphology of the veins on the surface of the tobacco leaves and record the morphological characteristic parameters of the veins on the surface of the tobacco leaves; Step 2: Based on the morphological characteristic parameters of the vein part of the tobacco leaf surface, a two-dimensional vein model is established. The two-dimensional vein model includes a plane base, veins, and water droplets. The plane base is rectangular, and the veins are established on the plane base. The veins are semi-cylindrical. The radius of the semi-cylindrical vein is set to R, the length is set to L, and the difference between the vein radius and the droplet infiltration depth is set to h; Step 3: Based on the Cassie-Baxter model, the calculation expression of the tobacco leaf vein part infiltration contact angle prediction model is established to predict the contact angle of the tobacco leaf vein part and obtain the predicted contact angle Specifically, in the calculation expression step of establishing the prediction model of the partial wetting contact angle of tobacco leaf veins, among the factors affecting the wetting contact angle, the local influencing factors include the radius R of the leaf vein and the difference h between the leaf vein radius and the droplet wetting depth, that is, the percentage of the contact area between the droplet and the tobacco leaf to the total area. , calculate the percentage of solid-liquid contact area The following steps are involved: Calculate the arc length of contact between the droplet and the leaf vein : ; Calculate the area of ​​contact between the droplet and the leaf vein : ; Calculate the projected area of ​​leaf veins : ; in, represents the arc length, R represents the radius of the vein, h represents the difference between the radius of the vein and the depth of the droplet penetration, Indicates the length of the leaf veins, represents the contact area between the droplet and the leaf vein, represents the projected area of ​​leaf veins; The contact area between the droplet and the leaf vein Projected area of ​​leaf veins Make the ratio and get the percentage of solid-liquid contact area , which is substituted into the Cassie-Baxter model to obtain the corresponding predicted contact angle expression: ； ； Where R represents the radius of the leaf vein, h represents the difference between the leaf vein radius and the droplet penetration depth, represents the contact area between the droplet and the leaf vein, represents the projected area of ​​the leaf veins, is the predicted contact angle of the vein part and the mesophyll part under the Cassie-Baxter model, is the Young's contact angle of the tobacco leaf; Step 4: Perform finite element simulation on the two-dimensional model of leaf veins to obtain the simulated contact angle; Step 5: Measure the contact angle of the tobacco leaf veins experimentally, obtain the experimental contact angle and calculate the Young's contact angle ; Step 6: Based on Young's contact angle The calculation expression of the contact angle prediction model of tobacco leaf vein part infiltration is used to predict the contact angle obtained. The fitting error analysis was performed with the simulated contact angle.

2. The model calculation method for the contact angle between the vein portion of the tobacco leaf surface and the droplet according to claim 1 is characterized in that: Tobacco leaves include the vein part and the mesophyll part. The contact angle of the vein part and the contact angle of the mesophyll part are The following conditions should be met: ； in, is the predicted contact angle of the vein part and the mesophyll part under the Cassie-Baxter model, is the Young's contact angle of the tobacco leaf.

3. The model calculation method for the contact angle between the vein portion of the tobacco leaf surface and the droplet according to claim 1 is characterized in that: In step S2, the wetted area The difference h between the leaf vein radius R and the droplet wetting depth should satisfy the following conditions: ； ； in, represents the area of ​​the leaf veins soaked by the droplet, represents the projected area of ​​the leaf vein, R represents the leaf vein radius, h represents the difference between the leaf vein radius and the droplet penetration depth, and The ratio of is greater than 1 and h is greater than 0.

4. The model calculation method for the contact angle between the vein portion of the tobacco leaf surface and the droplet according to claim 1 is characterized in that: Step 5 also includes calculating the Young's contact angle based on the experimental contact angle , specifically including: Determination of the surface tension of tobacco leaves by the two-liquid method , the surface tension includes polar and non-polar components, and the expression is: ， Among them, the superscript P represents the polar part, and D represents the non-polar part; Based on the surface tension of the droplet , the solid-liquid interfacial tension is calculated using the Fowkes method and is expressed as , the expression is: ； According to the calculated surface tension of tobacco leaves , the surface tension of the droplet and solid-liquid interfacial tension Three surface tension values ​​are used to calculate the Young's contact angle of different tobacco leaves. size.

5. The model calculation method for the contact angle between the vein portion of the tobacco leaf surface and the droplet according to claim 4, characterized in that: The surface tension of the droplet are the surface tensions of water and diiodomethane, respectively.

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