Device for measuring surface tension coefficient and air viscosity coefficient based on bubbles

Abstract

The utility model discloses a device for measuring a surface tension coefficient and an air viscosity coefficient based on bubbles, and mainly solves the problems that the conventional device for measuring the surface tension coefficient and the air viscosity coefficient is mutually independent and the experiment cost is relatively high. The device comprises a buffer, a variable pressure intensity device connected with the buffer, a thin tube assembly, a bubble hole assembly, a barometer, a sealing piece connected with the thin tube assembly, a backlight source arranged on one side of the bubble hole assembly, imaging equipment arranged on the other side of the bubble hole assembly, and image data processing equipment connected with the imaging equipment. Through the design, two simple and independent experiments in the traditional sense are integrated into an experiment with rich content through the bubble which is an interesting bridge and a new experiment method generated by the bubble, the experimental device has reliable theoretical basis and teaching value, the teaching experiment method is expanded, and the experiment efficiency is improved. And students can be guided to carefully research fluid mechanics knowledge behind the bubble phenomenon.

Description

Technical Field

[0001] The utility model belongs to the technical field of teaching instruments, and in particular relates to a device for measuring surface tension coefficient and air viscosity coefficient based on bubbles. Background Art

[0002] Surface tension is a property of a liquid's surface that describes the tension or pull on the surface caused by the interaction of liquid molecules inside and outside the liquid. Studying this property of liquid surface tension is crucial for understanding and explaining liquid behavior and many liquid interface phenomena. The surface tension coefficient is the surface tension acting on a line segment per unit length on the liquid surface. Common methods for measuring the surface tension coefficient include the capillary tube method, the maximum bubble pressure method, the pull-off method, the drop weight method, the pendant drop method based on morphology recognition, and the liquid bridge method. Viscosity is a physical property that describes the viscosity and viscosity of a fluid. It measures the fluid's resistance to flow, specifically the internal friction between fluid molecules. Viscosity is a key parameter in fluid mechanics and is crucial for understanding and describing various flow phenomena, including liquid and gas flow, solution diffusion, and heat conduction. Experimental methods involving the air viscosity coefficient include the capillary tube method, the damped vibration method, the air cushion guide method, the simple pendulum method, and the Millikan oil drop method.

[0003] The formation and bursting of bubbles, changes in bubble size, the flow of surface liquids, and changes in color are common physical phenomena in daily life. These phenomena, rich in physical knowledge, can support a wide range of experimental teaching content. The size of bubbles is related to the surface tension coefficient of the liquid and the pressure difference between the internal and external gases. During gas flow, the amount of gas flow is related to factors such as the viscosity coefficient of the gas and the pressure difference between the internal and external gases. In previous experimental teaching, the surface tension coefficient of the liquid and the viscosity coefficient of the gas were two separate experimental contents, each using two independent experimental devices to measure the relevant parameters. Currently, there is no teaching experimental device that can study the surface tension coefficient and the viscosity coefficient of air using the same experimental device. Utility Model Content

[0004] The purpose of this utility model is to provide a device for measuring surface tension coefficient and air viscosity coefficient based on bubbles, which mainly solves the problem that existing surface tension coefficient and air viscosity coefficient measuring devices are independent of each other and have high experimental costs. At the same time, it avoids high physical quantity measurement requirements (such as the time response of a barometer) and lowers the experimental threshold.

[0005] In order to achieve the above purpose, the technical solution adopted by the present utility model is as follows:

[0006] A device for measuring surface tension coefficient and air viscosity coefficient based on bubbles, comprising a buffer, a pressure transformer connected to the buffer, a capillary assembly, a bubble assembly and a barometer, a sealing member connected to the capillary assembly, a backlight source arranged on one side of the bubble assembly, an imaging device arranged on the other side of the bubble assembly, and an image data processing device connected to the imaging device; wherein the barometer is used to measure the difference in gas pressure inside and outside the bubble.

[0007] Furthermore, in the present invention, the holes on the pore assembly are circular holes, and the pore assembly connects the internal gas of the buffer with the external ambient atmosphere only through the holes.

[0008] Furthermore, in the present invention, the inner radius s, length L and hole radius R of the straight capillary tube of the capillary tube assembly should satisfy Where η is the air viscosity coefficient, σ is the bubble surface tension coefficient, and ρ is the air density.

[0009] Furthermore, in the present invention, the pressure transformer adopts a syringe or a syringe pump.

[0010] Furthermore, in the present invention, the bubble hole assembly and the capillary assembly are detachably mounted on the buffer.

[0011] Furthermore, in the present invention, the bubble pore assembly and / or the capillary assembly are integrally formed with the buffer.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) This utility model integrates two traditionally simple independent experiments into a rich experiment through the interesting bridge of bubbles and the new experimental method generated thereby. It has a reliable theoretical basis and teaching value, which not only expands the teaching experimental method, but also guides students to carefully study the fluid mechanics knowledge behind the bubble phenomenon.

[0014] (2) The utility model achieves the purpose of measuring the surface tension coefficient and air viscosity coefficient of bubbles on the same set of experimental equipment by designing a new experimental device and making full use of the static and dynamic data of the system. At the same time, it avoids the high physical quantity measurement requirements (such as the time response of the barometer) and reduces the experimental threshold and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of the present utility model.

[0016] The names corresponding to the reference numerals are:

[0017] 1- buffer, 2- pressure transformer, 3- capillary assembly, 4- cell assembly, 5- seal, 6- backlight source, 7- imaging device, 8- image data processing device, 9- barometer. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0019] Example

[0020] like Figure 1 As shown, the present invention discloses a device for measuring surface tension coefficient and air viscosity coefficient based on bubbles, comprising a buffer 1, a pressure transformer 2, a capillary assembly 3, a cell assembly 4, and a barometer 9 connected to the buffer 1, a sealing member 5 connected to the capillary assembly 3, a backlight source 6 disposed on one side of the cell assembly 4, an imaging device 7 disposed on the other side of the cell assembly 4, and an image data processing device 8 connected to the imaging device 7. The cell assembly 4 or the capillary assembly 3 can be independently mounted on the buffer 1, or both can be integrally formed on the buffer 1. The former can be replaced independently, while the latter needs to be replaced together with the buffer 1.

[0021] In this embodiment, the buffer 1 is a hollow body, which is in a non-sealed state when it exists alone. The volume of the hollow part is much larger than the volume of the bubble. During the change of bubble size, the buffer 1 plays a buffering role, so that the internal air pressure is evenly distributed.

[0022] The pressure changer 2 is in gas communication with the buffer 1 to change or maintain the gas pressure in the buffer in a sealed state. In this embodiment, the pressure changer 2 is a syringe.

[0023] The barometer 9 is in air communication with the buffer 1 to measure the pressure difference between the gas in the buffer 1 and the ambient atmosphere outside the buffer.

[0024] The bubble component 4 is in gas communication with the buffer 1 and includes a circular hole. The bubble component 4 connects the internal gas of the buffer 1 with the external ambient atmosphere through the hole. The bubble component 4 can be replaced with bubble components 4 of different hole diameters to meet the needs of experimental teaching.

[0025] The capillary assembly 3 is connected to the buffer gas path, and the capillary assembly 3 includes a hollow straight capillary tube. The inner radius s, length L and radius R of the hole of the straight capillary tube should meet the following requirements: The capillary assembly 3 has only the straight capillary tube connecting the internal gas of the buffer 1 with the external ambient atmosphere. The capillary assembly 3 can be replaced with different specifications, including different straight capillary inner diameters and different straight capillary lengths, to meet the needs of experimental teaching.

[0026] A seal 5 acts on the capillary assembly 3 to control the flow of gas within the straight capillary. A backlight 6 is a uniformly luminous surface light source located behind the cell assembly 4 to enhance contrast. The imaging device 7 is a camera, comprising a camera and lens, capable of taking photos, recording videos, and saving images. It is located in front of the cell assembly 4 and faces the backlight 6. The image data processing device 8 includes programs for video capture, image analysis, pixel calibration, and dimensional measurement.

[0027] During use, a small amount of the bubble liquid is dipped through the external film-forming part, and the bubble liquid is applied to the hole to form a liquid film to isolate the gas inside the buffer 1 from the external ambient atmosphere, and when there is a non-zero pressure difference between the gas inside the buffer 1 and the external ambient atmosphere, bubbles with a certain curvature radius are formed. The bubble liquid can be replaced with different liquids to meet the needs of experimental teaching.

[0028] The process of measuring the surface tension coefficient of bubbles using this device is as follows: At the beginning of the experiment, light the backlight source 6, check that the seal 5 is under normal control, and the barometer 9 displays normally. Adjust the imaging device 7 so that the image near the hole of the bubble component 4 is clear, and the hole is near the center of the vertical direction of the field of view. Then, control the seal 5 to seal the straight capillary of the capillary component 3. Use the film-forming component to dip a small amount of bubble liquid and apply it to the hole. At this time, a layer of liquid film will form on the hole. If the hole is at the upper end of the buffer 1, air is pressed into the buffer 1 through the syringe to increase the gas pressure in the buffer 1 to form a positive pressure bubble. If the hole is at the lower end of the buffer 1, air is withdrawn through the syringe to reduce the gas pressure in the buffer 1 to form a negative pressure bubble. When the system tends to be quasi-static, use the imaging device 7 to take a picture of the bubble and record the corresponding barometer 9 data. Adjust the syringe and take pictures of bubbles of different sizes and record the corresponding barometer 9 data.

[0029] The device is used to measure the air viscosity coefficient: when a large bubble exists, the syringe is kept stationary and the video recording function of the imaging device 9 is turned on. Then, the sealing member 5 is controlled to unblock the straight capillary tube, and the bubble slowly shrinks. The video recording is stopped after the bubble stops shrinking.

[0030] The data processing process of this embodiment is as follows: the pictures taken by the imaging device 7 and the recorded video are imported into the image data processing device 8, and pictures of the bubble contraction process at multiple different sizes are intercepted from the recorded video and the corresponding moments are recorded. The image is calibrated according to the relationship between the actual size of the known object in the image and the number of pixels, and the bubble size is measured (the bubble size can be the bubble radius r, the bubble diameter 2r, the hole radius R, the hole diameter 2R, the farthest distance h from each point on the bubble surface to the hole surface, or an algebraic expression covering the aforementioned related sizes). Combined with the pressure difference data obtained by the barometer 9 when tending to quasi-static state, the formula can be used to calculate the bubble size. or Calculate the surface tension coefficient of the bubble, and then combine it with the relationship between bubble size and time in the dynamic process, and then use the formula (the bubble satisfies the perfect sphere approximation) or (The bubble satisfies the partial sphere condition) and the viscosity of the air is calculated. It can be seen that neither of the two formulas for the dynamic process mentioned above contains the pressure difference Δp, and Δp is measured only when the state approaches quasi-static. This means that this experimental method does not require the barometer 9 to have a fast time response characteristic, which reduces the requirements for the barometer 9.

[0031] The specific calculation process of the viscosity coefficient is as follows:

[0032] According to Poiseuille's equation:

[0033]

[0034] Where Q is the fluid flow rate through the pipeline, that is, the volume of fluid passing through the pipeline per unit time.

[0035] When the bubble radius meets the set size range, it is approximated as a complete sphere, and the volume of the bubble is:

[0036]

[0037] According to equations (1#) and (2#), under the conditions of the complete sphere approximation, we have:

[0038]

[0039] Linear fit r 4 The relationship curve between η and t is calculated by the slope;

[0040] When the bubble radius meets another set size range, the bubble is no longer approximated as a complete sphere, but a partial sphere. The volume of the bubble is:

[0041]

[0042] According to formula (1#) and (4#), under the partial ball condition, we have:

[0043]

[0044] Linear fitting The relationship curve between η and t is plotted, and η is calculated from the slope.

[0045] Among them, Poiseuille's law is an important law in fluid dynamics. It describes the relationship between the flow rate and the pressure difference at both ends of the pipe, the pipe radius, the pipe length and the fluid viscosity coefficient when an incompressible Newtonian fluid flows steadily in a long straight circular pipe with a small Reynolds number and the flow form is laminar. This law is valid for all fluids. The capillary method commonly used in the laboratory to measure the viscosity of liquids is based on this law. It is rarely used in basic experiments for gas flow phenomena. In the flow field inside the pipe, the Reynolds number Re is:

[0046]

[0047] According to formula (1#), (6#) and We can get:

[0048]

[0049] Where ρ is the air density. When the Reynolds number is ≤ 2300, the fluid flow is considered laminar. Therefore, for the air density, air viscosity, and bubble surface tension coefficient that can be roughly estimated, the laminar flow condition can be satisfied by designing appropriate R, s, and L, namely:

[0050]

[0051] Through the above design, the utility model integrates two simple independent experiments in the traditional sense into a rich experiment through bubbles, an interesting bridge, and the new experimental method generated thereby. It has a reliable theoretical basis and teaching value, which not only expands the teaching experimental method, but also guides students to carefully study the fluid mechanics knowledge behind the bubble phenomenon.

[0052] The above embodiment is only one of the preferred implementation methods of the present invention and should not be used to limit the scope of protection of the present invention. Any changes or modifications that have no substantive meaning made to the main design concept and spirit of the present invention, as long as the technical problems they solve are still consistent with the present invention, should be included in the scope of protection of the present invention.

Claims

1. A device for measuring surface tension coefficient and air viscosity coefficient based on bubbles, characterized in that: The invention comprises a buffer (1), a pressure transformer (2) connected to the buffer (1), a capillary assembly (3), a bubble assembly (4) and a barometer (9), a sealing member (5) connected to the capillary assembly (3), a backlight source (6) arranged on one side of the bubble assembly (4), an imaging device (7) arranged on the other side of the bubble assembly (4), and an image data processing device (8) connected to the imaging device (7); wherein the barometer (9) is used to measure the difference in gas pressure inside and outside the bubble.

2. The device for measuring surface tension coefficient and air viscosity coefficient based on bubbles according to claim 1, characterized in that: The holes on the pore assembly (4) are circular holes, and the pore assembly (4) communicates with the internal gas of the buffer (1) and the external ambient atmosphere only through the holes.

3. The device for measuring surface tension coefficient and air viscosity coefficient based on bubbles according to claim 1, characterized in that: The inner radius s, length L and hole radius R of the straight capillary tube of the capillary tube assembly (3) should satisfy Where η is the air viscosity coefficient, σ is the bubble surface tension coefficient, and ρ is the air density.

4. The device for measuring surface tension coefficient and air viscosity coefficient based on bubbles according to claim 1, characterized in that: The pressure transformer (2) adopts a syringe or a syringe pump.

5. The device for measuring surface tension coefficient and air viscosity coefficient based on bubbles according to claim 1, characterized in that: The bubble hole assembly (4) and the thin tube assembly (3) are detachably mounted on the buffer (1).

6. The device for measuring surface tension coefficient and air viscosity coefficient based on bubbles according to claim 1, characterized in that: The bubble hole assembly (4) and / or the thin tube assembly (3) are integrally formed with the buffer (1).

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