CN114822161B - Method for researching viscosity coefficient of liquid through image acquisition - Google Patents
Method for researching viscosity coefficient of liquid through image acquisition Download PDFInfo
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- CN114822161B CN114822161B CN202210521220.3A CN202210521220A CN114822161B CN 114822161 B CN114822161 B CN 114822161B CN 202210521220 A CN202210521220 A CN 202210521220A CN 114822161 B CN114822161 B CN 114822161B
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- 238000000034 method Methods 0.000 title claims abstract description 40
- 239000007788 liquid Substances 0.000 title claims abstract description 36
- 239000011521 glass Substances 0.000 claims abstract description 94
- 239000008188 pellet Substances 0.000 claims abstract description 67
- 238000002474 experimental method Methods 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 238000004458 analytical method Methods 0.000 claims description 9
- 230000001502 supplementing effect Effects 0.000 claims description 8
- 238000012360 testing method Methods 0.000 claims description 7
- 230000001133 acceleration Effects 0.000 claims description 5
- 230000005484 gravity Effects 0.000 claims description 5
- 238000001454 recorded image Methods 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 18
- 239000003921 oil Substances 0.000 description 42
- 238000003384 imaging method Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 4
- 239000004359 castor oil Substances 0.000 description 4
- 235000019438 castor oil Nutrition 0.000 description 4
- ZEMPKEQAKRGZGQ-XOQCFJPHSA-N glycerol triricinoleate Natural products CCCCCC[C@@H](O)CC=CCCCCCCCC(=O)OC[C@@H](COC(=O)CCCCCCCC=CC[C@@H](O)CCCCCC)OC(=O)CCCCCCCC=CC[C@H](O)CCCCCC ZEMPKEQAKRGZGQ-XOQCFJPHSA-N 0.000 description 4
- 239000004973 liquid crystal related substance Substances 0.000 description 4
- 238000010191 image analysis Methods 0.000 description 3
- 238000006073 displacement reaction Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
- G09B19/00—Teaching not covered by other main groups of this subclass
Abstract
The application provides a method for researching liquid viscosity coefficient through image acquisition, and aims to solve the problem of inaccurate measurement of liquid viscosity coefficient in the prior art. The method provided by the application comprises the following steps: step S01, standing oil in the double-layer glass tube to ensure that no bubbles exist in the oil; step S02, adjusting the temperature of oil in the double-layer glass tube to enable the temperature of the oil to be stable at a certain specific value; step S03, adjusting the position of the measuring camera so that the acquisition center of the camera is opposite to the middle part of the double-layer glass tube along the axis direction of the double-layer glass tube, and meanwhile, no obvious shadow exists in a camera picture; step S04, acquiring and recording image data of the falling of the pellets in the oil liquid through a camera; step S05, analyzing the image data. The application collects the data in the falling process of the small ball by means of the camera so as to measure and research the viscosity coefficient of the liquid, and solves the problem of inaccurate measurement of the viscosity coefficient of the liquid in the prior art.
Description
Technical Field
The application relates to the technical field of experimental teaching data measurement, in particular to a method for researching liquid viscosity coefficient through image acquisition.
Background
The measurement of the viscosity coefficient of the liquid is a typical experiment in a physical experiment of university, and in the measurement process, the falling speed of the small ball adopts a measurement mode of human eye reading and stopwatch timing. Because of the different reaction times of each experimenter, there is often a large error in a single experiment, possibly even making the experimental data unusable. The common solution is to take the average time length of falling 20cm to calculate the speed through multiple experiments, but because the diameter of the small ball has fine differences each time, the diameter of the small ball needs to be measured before the small ball is put in each time to obtain accurate experimental data, and the small ball needs to be ensured to be as close to the central axis of the glass tube as possible when the small ball is put in, so that the whole experiment becomes extremely complex, and the error source cannot be determined in the error analysis process.
The above information disclosed in the background section is only for enhancement of understanding of the background of the application and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
The application provides a method for researching liquid viscosity coefficient through image acquisition, which aims to solve the problems of inaccurate measurement and complex measurement steps of liquid viscosity coefficient in the prior art, and the method can be used for acquiring data in the falling process of a small ball through a camera and analyzing the data.
The technical scheme adopted by the application is as follows:
a method for studying the viscosity coefficient of a liquid by image acquisition, comprising the steps of:
step S01, standing oil in the double-layer glass tube to ensure that no bubbles exist in the oil;
step S02, adjusting the temperature of oil in the double-layer glass tube to enable the temperature of the oil to be stable at a certain specific value;
step S03, adjusting the position of the measuring camera so that the acquisition center of the camera is opposite to the middle part of the double-layer glass tube along the axis direction of the double-layer glass tube, and meanwhile, no obvious shadow exists in a camera picture;
step S04, acquiring and recording image data of the falling of the pellets in the oil liquid through a camera;
and S05, selecting the image data in the corresponding identification range for comprehensive analysis.
Optionally, the step S02 of adjusting the oil temperature in the double glass tube so that the oil temperature is stabilized at a specific value includes:
the oil in the double-layer glass tube is subjected to heat exchange by adopting a temperature control water circulation device, the temperature of the oil is controlled to be stable, the temperature control duration is at least 10 minutes, and the temperature of the oil is consistent with the temperature of external circulating water.
Optionally, the step S03 adjusts the position of the measuring camera so that the collection center of the camera is opposite to the middle part of the double-layer glass tube along the axis direction, and the specific operation steps of no obvious shadow in the camera picture include:
s31, mounting a solid-color background plate to the opposite side of the acquisition end of the camera;
s32, adjusting camera parameters, wherein the cameras comprise a first camera and a second camera, the cameras of the first camera and the second camera are orthogonally arranged, and the resolutions of the two cameras are adjusted to a specific value; the collecting area of the first camera is outwards expanded from the two ends by taking a certain scale value of the double-layer glass tube as the center, and the collecting height of the collecting area after the outwards expansion is at least 15 cm; the acquisition area of the second camera is the full length range of the double-layer glass tube;
s33, adjusting the position of the light supplementing lamp to enable the light supplementing lamp to be located at the inclined rear of the first camera, so that the background of the double-layer glass tube in the acquisition area of the first camera is free of obvious shadows.
Optionally, the step S04 of collecting and recording, by a camera, image data of the falling of the pellets in the oil liquid specifically includes the following steps:
s41, measuring the diameter of the small ball by adopting a micrometer, and recording;
s42, placing the small ball into the inner tube of the double-layer glass tube from the central axis of the double-layer glass tube;
s43, recording the falling track of the small ball by a first camera in a video recording mode; and meanwhile, the position of the ball falling in real time is acquired and recorded through a second camera.
Optionally, the first camera is used for collecting time when the pellets enter the double-layer glass tube and stop recording after the pellets completely fall to the bottom of the double-layer glass tube.
Optionally, the step S05 of selecting the image data in the corresponding recognition range for comprehensive analysis includes:
s51, replaying the recorded image data, judging whether the pellets meet the test requirement, if so, entering a step S52, and if not, evaluating whether the pellet falling experiment needs to be carried out again;
s52, selecting a range between upper and lower preset scale marks at a certain scale value of the double-layer glass tube as the identification range;
and S53, performing linear fitting on the displacement-time data of the small ball to obtain the speed of the small ball, and converting the speed of the small ball into a standard unit for calculating the viscosity coefficient.
Optionally, the test requirements in step S51 include: if there are bubbles and turbulence around the small ball, the small ball is located in the center of the double-layer glass tube, if there are no bubbles and turbulence around the small ball and located in the center of the double-layer glass tube, the requirement is met, if there are bubbles and turbulence around the small ball, the small ball falling experiment needs to be carried out again, and if the falling track of the small ball is not coincident with the central axis of the double-layer glass tube, the offset is measured.
Optionally, the linear fitting formula of the displacement-time data of the ball in the step S53 is:
y＝v y ·t+y 0
wherein y is the image analysis coordinate of the pellet; v y Is the speed of the pellet in the vertical direction (y-direction); t is the falling time of the pellets; y is 0 Is the vertical (y-direction) coordinate of the pellet at time 0.
Optionally, the calculation formula of the viscosity coefficient is:
wherein ρ is the density of the pellets, ρ 0 The density of oil, g is gravity acceleration, v y The speed of the pellets, D is the diameter of the pellets, and D is the diameter of the double glass tube.
Compared with the prior art, the application has the beneficial effects that:
1. in the process of measuring the viscosity coefficient, the timing precision of the falling ball is improved in an image acquisition mode, so that the error of the final measurement result is smaller.
2. The method can accurately judge whether the small ball in the identification range moves at a uniform speed.
3. The device can be slowly placed to watch the falling video of the small ball, observe whether the phenomena of turbulence, bubbles and the like exist around the small ball, reduce the interference of experimental conditions and improve the accuracy of experimental results.
4. The image data collected by the two orthogonal cameras is used for judging whether the small ball is positioned at the center of the double-layer glass tube, judging whether the small ball falls down along the central axis of the double-layer glass tube, and forming a measuring range at a certain position in the double-layer glass tube, so that the measuring range is wider.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of an imaging structure of a camera.
Fig. 2 is a schematic view showing a state in which the pellets fall in the double glass tube.
Fig. 3 is a schematic diagram of the ball drop displacement versus time.
Fig. 4 is a schematic view of a drop position of a test ball.
FIG. 5 is a diagram showing the relative error distribution between stopwatch and camera measurements.
Fig. 6 is a schematic diagram of image coordinate deviation caused by imaging inclination.
Detailed Description
Hereinafter, only certain exemplary embodiments are briefly described. As will be recognized by those of skill in the pertinent art, the described embodiments may be modified in various different ways without departing from the spirit or scope of the present application. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.
The following disclosure provides many different embodiments, or examples, for implementing different features of the application. In order to simplify the present disclosure, components and arrangements of specific examples are described below. They are, of course, merely examples and are not intended to limit the application. Furthermore, the present application may repeat reference numerals and/or letters in the various examples, which are for the purpose of brevity and clarity, and which do not themselves indicate the relationship between the various embodiments and/or arrangements discussed. In addition, the present application provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the application of other processes and/or the use of other materials.
Embodiments of the present application will be described in detail below with reference to the accompanying drawings.
The embodiment of the application provides a method for researching liquid viscosity coefficient through image acquisition, which comprises the following steps:
step S01, standing oil in the double-layer glass tube to ensure that no bubbles exist in the oil;
step S02, adjusting the temperature of oil in the double-layer glass tube to enable the temperature of the oil to be stable at a certain specific value;
step S03, adjusting the position of the measuring camera so that the acquisition center of the camera is opposite to the middle part of the double-layer glass tube along the axis direction of the double-layer glass tube, and meanwhile, no obvious shadow exists in a camera picture;
step S04, acquiring and recording image data of the falling of the pellets in the oil liquid through a camera;
step S06, selecting the image data in the corresponding identification range for comprehensive analysis.
When experiments are carried out, firstly, oil is filled into a double-layer glass tube, a cover is covered for standing, so that bubbles in the oil are completely eliminated, heat exchange is carried out on the oil, the temperature of the oil is at a certain specific value, the position of a camera is adjusted after the temperature is stabilized, the acquisition center of the camera is opposite to the middle of the double-layer glass tube, an acquisition picture is adjusted, no obvious shadow exists in the picture, the accuracy of data in the acquisition process is prevented from being influenced, the track of the falling of a small ball in the oil is recorded through the camera, the falling time of the small ball is calculated through scales on the double-layer glass tube, and comprehensive analysis is carried out by combining the data such as the oil temperature, the falling time, the size data of the small ball, the diameter of the double-layer glass tube and the like, so as to obtain the viscosity coefficient of the oil.
In another embodiment, in order to control the temperature conveniently, the step S02 of adjusting the temperature of the oil in the double glass tube to make the temperature of the oil stable at a specific value includes:
and (3) carrying out heat exchange on the oil liquid in the double-layer glass tube by adopting a temperature control water circulation device, and controlling the temperature of the oil liquid to stabilize the temperature after the temperature of the oil liquid is stabilized, wherein the temperature control time is at least 10 minutes, so that the temperature of the oil liquid is consistent with the temperature of external circulating water. The oil liquid in the double-layer glass tube is prevented from having different temperatures, so that the viscosity coefficient of the oil liquid is inconsistent, and the speed of the oil liquid is inconsistent in the falling process of the measuring ball. If the pellets do not fall down at a constant speed in the measuring process, the temperature control water circulation device is controlled to continuously exchange heat with the oil.
In another embodiment, in order to avoid that external factors affect the capturing effect of the camera during the capturing process, the step S03 adjusts the position of the measuring camera so that the capturing center of the camera is opposite to the middle of the double-layer glass tube along the axial direction of the double-layer glass tube, and the specific operation steps of no obvious shadows in the image of the camera include:
s31, mounting a solid-color background plate to the opposite side of the acquisition end of the camera;
s32, adjusting camera parameters, wherein the cameras comprise a first camera and a second camera, the cameras of the first camera and the second camera are orthogonally arranged, and the resolution of each of the two cameras is adjusted to 1920 multiplied by 1080; the collecting area of the first camera is outwards expanded from the 20cm scale of the double-layer glass tube to two ends, and the collecting height of the collecting area after the outwards expanding is at least 15 cm; the acquisition area of the second camera is the full length range of the double-layer glass tube; of course, other scales can be used as centers to expand outwards at two ends.
S33, adjusting the position of the light supplementing lamp to enable the light supplementing lamp to be located at the inclined rear of the first camera, so that the background of the double-layer glass tube in the acquisition area of the first camera is free of obvious shadows.
In another embodiment, in order to facilitate the subsequent calculation, the step S04 of capturing and recording the image data of the ball falling in the oil liquid by the camera specifically includes the following steps:
s41, measuring the diameter of the small ball by adopting a micrometer, and recording;
s42, placing the small ball into the inner tube of the double-layer glass tube from the central axis of the double-layer glass tube;
s43, recording the falling track of the small ball by a first camera in a video recording mode; and meanwhile, the position of the ball falling in real time is acquired and recorded through the second camera, the time is counted when the ball falls to the position of 5 cm of the scale mark, the time is stopped after the ball passes through the position of 25 cm of the scale mark, and the falling time of the ball from 5 cm to 25 cm is recorded.
In this embodiment, the first camera is disposed at a specific position facing the double glass tube for a 5 cm to 25 cm interval to record data, and the above specific steps are also based on the description of the specific position, and it will be understood that the specific position of the first camera may of course be other positions corresponding to the double glass tube.
The first camera and the second camera in the application are both high-speed cameras, so that the movement track of the small ball in the double-layer glass tube can be conveniently recorded.
In another embodiment, in order to facilitate the subsequent playback of the whole falling process of the pellet, the first camera is used for collecting the pellet from the beginning of the pellet entering the double glass tube until the pellet completely falls to the bottom of the double glass tube and then stopping recording.
In another embodiment, the step of selecting the image data in the corresponding identification range for comprehensive analysis in step S05 includes:
s51, replaying the recorded image data, judging whether the pellets meet the test requirement, if so, entering a step S52, and if not, evaluating whether the pellet falling experiment needs to be carried out again;
s52, selecting a range between the upper and lower grid scale marks at the 20cm position of the double-layer glass tube as the identification range;
and S53, performing linear fitting on the displacement-time data of the small ball to obtain the speed of the small ball, and converting the speed of the small ball into a standard unit for calculating the viscosity coefficient.
Optionally, the test requirements in step S51 include: if there are bubbles and turbulence around the small ball, the small ball is located in the center of the double-layer glass tube, if there are no bubbles and turbulence around the small ball and located in the center of the double-layer glass tube, the requirement is met, if there are bubbles and turbulence around the small ball, the small ball falling experiment needs to be carried out again, and if the falling track of the small ball is not coincident with the central axis of the double-layer glass tube, the offset is measured.
In the previous step, the speed calculation formula of the small ball measured in a single time is as follows:
wherein v is the speed of the pellet; t is the time for the pellet to fall within the selected range.
In the foregoing step, the linear fitting formula of the displacement-time data of the pellets is:
y＝v y ·t+y 0
wherein y is the image analysis coordinate of the pellet; v y Is the speed of the pellet in the vertical direction (y-direction); t time of falling of the pellets; y is 0 Is the vertical (y-direction) coordinate of the pellet at time 0.
Further, the calculation formula of the viscosity coefficient is as follows:
wherein ρ is the density of the pellets, ρ 0 The density of oil, g is gravity acceleration, v y The speed of the pellets, D is the diameter of the pellets, and D is the diameter of the double glass tube.
The application measures the displacement and time in the falling process of the small ball by high-speed shooting, further carries out linear fitting on the data, and calculates the viscosity coefficient.
Specific principle of high-speed photogrammetry ball falling speed:
when the imaging picture of the camera is parallel to the photographed object, the imaging mode at this time can be approximated as aperture imaging. At this time, the distance in the screen is in an equal ratio to the distance of the actual object, as shown in fig. 1:
wherein a is the length of the object side a in fig. 1; a' is the length of the side a of the object after imaging in the camera; b is the length of the object side b in fig. 1; b' is the length of the edge b of the object after imaging in the camera; c is the length of the object side c in fig. 1; c' is the length of the side c of the object after imaging in the camera; c (C) ratio Is the scaling factor between the object and the image.
Thus, as long as a specific position of the pellet in the picture is recognizedAnd calibrating the scaling factor C ratio The position of the pellet in the real space can be obtained>
Since the shooting frame rate of the high-speed camera is high (f. Gtoreq.60 fbs) and can be basically regarded as exposure at equal time intervals, the movement time t of the pellets at the ith frame can be obtained by the frame rate.
t＝t 0 +f·i
Wherein t is 0 The time when the video starts to be recorded; f is shooting frame rate; i is the number of frames of the current picture.
From the position information and time information of the pellets in each frame, the speed v of the pellets can be found:
wherein, the liquid crystal display device comprises a liquid crystal display device,is the speed of the pellets, which is the speed of the pellets,
the specific experimental process is as follows:
and adding castor oil into the double-layer glass tube, covering a dust cover, and standing for a period of time to ensure that no bubbles exist in the castor oil. And white paper is covered on the bracket right behind the double-layer glass tube, so that the background interference during shooting is reduced.
The temperature control water circulation device is communicated with the bottom and the top of the double-layer glass tube, the circulation water inlet is positioned at the top of the double-layer glass tube, the circulation water outlet is positioned at the bottom of the double-layer glass tube, the temperature of the temperature control water circulation device is regulated to 30 ℃, and the temperature is controlled.
After the temperature is stable, the temperature is kept for 10 minutes, so that the circulating water and the castor oil are ensured to exchange heat fully, and the oil temperature and the water temperature reach the same temperature.
The level gauge is placed on a base provided with a double-layer glass tube, and supporting feet on the base are adjusted so that the base is placed horizontally.
Placing a first camera at a position 20cm in front of a double-layer glass tube, setting the resolution of the first camera to 1920 multiplied by 1080, and adjusting the picture so that the first camera can shoot the length of the double-layer glass tube which is more than 15 cm, and the picture center of the first camera is opposite to a scale mark of 20 cm; the second camera is arranged on the other side of the double-layer glass tube and is orthogonal to the first camera, the resolution of the second camera is 1920×1080, and the center of the picture is opposite to the scale line of 20cm (as shown in fig. 2). At this time, the graduation line at 20cm of the double glass tube coincides in the pictures of the first camera and the second camera. And adjusting the light supplementing position to ensure that the light supplementing position is positioned at the inclined rear of the first camera, so that the background of the double-layer glass tube in the two camera pictures has no obvious shadow.
Video recording is started.
One pellet was selected, and its diameter was measured using a micrometer and recorded.
The pellets were gently placed into the tube from the central axis of the double glass tube.
Stopping recording after the pellets fall completely.
The above steps were installed at oil temperatures of 35 degrees celsius, 40 degrees celsius, 45 degrees celsius, 50 degrees celsius and 55 degrees celsius, respectively, to measure, and the data were recorded to wait for analysis.
And (3) data recording:
the imaging surface of the camera is away from the double-layer glass tube: 20.7+0.4 cm (lens distance+focal length).
Glass tube: the total diameter is 35mm, the glass thickness is 2mm, and the inner diameter is as follows: 21mm, and the thickness of the circulating water layer is 3mm. Camera: resolution 1920x1080, frame rate 60fps.
Density of oil (castor oil): 0.955×10 3 kg/m 3 Density of pellets (steel): 7.850 ×10 3 kg/m 3 。
Known oil viscosity coefficient standard reference value (pa·s): 30 ℃ C:: 0.451 Local gravity acceleration at 40 ℃ to 0.231 and at 50 ℃ to 0.129: 9.7913m/s 2 。
Video analysis:
in video playback, it is observed whether there is turbulence of bubbles around the pellet and whether it is located at the center of the glass tube, and if there is no bubbles and turbulence around the pellet and the pellet is always at the center of the tube during the falling process, this experiment can be used to calculate the viscosity coefficient of the liquid.
In this implementation scenario, since the camera of the camera is facing the scribe line at 20cm, two cells near 20cm can be selected as the recognition range, in which the tilt angle imaged by the camera of the camera is very small, and the influence of the tilt angle can be ignored without performing complicated tilt angle correction. In other implementations, the camera's webcam may select other scales.
And (3) correcting a reading inclination angle:
because the camera cannot move the position during shooting, the recognized coordinates of the small ball need to be corrected in terms of reading inclination when processing data of a wide falling range.
Let the image analysis coordinates (readings with tilt angle) of the pellet be y and the actual coordinates be y' at time t. Let the thickness of the medium passing the light from left to right be d, d 1 ,d 2 ,d 3 ,d 4 . As shown in fig. 6.
From the law of refraction:
n air ·sinθ＝n glass ·sinθ 1 ＝n water ·sinθ 2 ＝n glass ·sinθ 3 ＝n oil ·sinθ 4
wherein, the liquid crystal display device comprises a liquid crystal display device,
the method can obtain:
after the position of the small ball is identified, the relation between the frame number (representing time) and the y coordinate (shown in fig. 3) can be drawn, and whether the linearity is good or not is observed, so that whether the selected small ball falling section moves at a uniform speed or not is judged. If the linearity is good, the experiment meets the experiment requirement of measuring the viscosity coefficient by the falling ball method. The displacement-time diagram in the figure is a few separate line segments, because the pellet is blocked by the score line when it passes through the score line, and therefore the coordinates of the pellet cannot be recognized.
Linear fitting is carried out on the displacement-time data of the small ball to obtain the speed v of the small ball y It is converted into standard units for calculating the viscosity coefficient eta.
y＝v y ·t+y 0
Wherein ρ is the density of the pellets, ρ 0 The density of oil, g is gravity acceleration, v y The speed of the pellets, D is the diameter of the pellets, and D is the diameter of the double glass tube.
The high-speed photographic metric data is shown in table 1, where the primary error is the largest is the experiment with the number 3, with an error of-3.09%. The reason for the large error is found by the drop video, and it is likely that the drop path of the pellets deviates from the central axis of the glass tube, as shown in fig. 4.
TABLE 1 high-speed photographic single measurement results (blank indicates no national standard value contrast)
Compared with the relative error distribution of the traditional method and the high-speed photographic experimental method, as shown in fig. 5, the measurement error of the high-speed photographic method is smaller and more uniform, no great fluctuation exists, the overall distribution is basically kept within +/-3.5%, and if some experiments with larger deviation from the experimental requirements are removed (for example, the experiment similar to the serial number 3 is judged as an invalid experiment because the falling position of the small ball deviates from the central axis, the measurement error of the viscosity coefficient can be controlled within +/-2.5% by the high-speed photographic method.
In summary, the viscosity coefficient measurement is performed by using high-speed photography instead of the traditional method (eyes and stopwatch), so that experimental data with smaller error can be obtained in a single experiment, and the consistency of each measurement is higher than that of the stopwatch measurement. In the actual physical experiment course, the invalid experiment times caused by reading errors or untimely reaction can be reduced, and better consistency of experiment data obtained by different students is ensured.
Through the verification of 30 (more) experiments, the identification algorithm for the falling of the high-speed photogrammetry pellets has good robustness, has simple requirements on experimental devices, and is an excellent measurement means in the measurement experiments of variable-temperature viscosity coefficients.
The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any person skilled in the art will readily recognize that various changes and substitutions are possible within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (6)
1. A method for studying the viscosity coefficient of a liquid by image acquisition, comprising the steps of:
step S01, standing oil in the double-layer glass tube to ensure that no bubbles exist in the oil;
step S02, adjusting the temperature of oil in the double-layer glass tube to enable the temperature of the oil to be stable at a certain specific value; step S03, adjusting the position of the measuring camera so that the acquisition center of the camera is opposite to the middle part of the double-layer glass tube along the axis direction of the double-layer glass tube, and meanwhile, no obvious shadow exists in a camera picture; the method specifically comprises the following steps:
s31, mounting a solid-color background plate to the opposite side of the acquisition end of the camera;
s32, adjusting camera parameters, wherein the cameras comprise a first camera and a second camera, the cameras of the first camera and the second camera are orthogonally arranged, and the resolutions of the two cameras are adjusted to a specific value;
the collecting area of the first camera is outwards expanded from two ends by taking a certain scale value of the double-layer glass tube as a center, and the collecting height of the collecting area after the outwards expanding is at least 15 cm; the acquisition area of the second camera is the full length range of the double-layer glass tube;
s33, adjusting the position of the light supplementing lamp to enable the light supplementing lamp to be positioned at the inclined rear of the first camera, so that the background of the double-layer glass tube in the acquisition area of the first camera has no obvious shadow;
step S04, acquiring and recording image data of the falling of the pellets in the oil liquid through a camera; the method specifically comprises the following steps:
s41, measuring the diameter of the small ball by adopting a micrometer, and recording;
s42, placing the small ball into the inner tube of the double-layer glass tube from the central axis of the double-layer glass tube;
s43, recording the falling track of the small ball by a first camera in a video recording mode; meanwhile, the real-time position of the falling ball is collected and recorded through a second camera;
s05, selecting image data in a corresponding identification range for comprehensive analysis; the method specifically comprises the following steps:
s51, replaying the recorded image data, judging whether the pellets meet the test requirement, if so, entering a step S52, and if not, evaluating whether the pellet falling experiment needs to be carried out again;
s52, selecting a range between upper and lower preset scale marks at a certain scale value of the double-layer glass tube as the identification range;
s53, recognizing the position of the small ball in the recognition range, performing linear fitting on displacement-time data of the small ball to obtain the speed of the small ball, and converting the speed of the small ball into a standard unit for calculating the viscosity coefficient.
2. The method for studying liquid viscosity coefficient by image acquisition according to claim 1, wherein the step S02 of adjusting the oil temperature in the double glass tube so that the oil temperature is stabilized at a specific value comprises:
and (3) carrying out heat exchange on the oil liquid in the double-layer glass tube by adopting a constant-temperature water circulation device, and controlling the temperature of the oil liquid after the temperature of the oil liquid is stable, wherein the temperature control duration is at least 10 minutes, so that the temperature of the oil liquid is consistent with the temperature of external circulating water.
3. The method for studying the viscosity coefficient of a liquid by image acquisition according to claim 1, wherein the acquisition time of the first camera is such that the recording is stopped after the pellet starts to enter the double glass tube until the pellet completely falls to the bottom of the double glass tube.
4. The method for studying liquid viscosity coefficient by image acquisition according to claim 1, wherein the test requirement in step S51 comprises: if there are bubbles and turbulence around the small ball, the small ball is located in the center of the double-layer glass tube, if there are no bubbles and turbulence around the small ball and located in the center of the double-layer glass tube, the requirement is met, if there are bubbles and turbulence around the small ball, the small ball falling experiment needs to be carried out again, and if the falling track of the small ball is not coincident with the central axis of the double-layer glass tube, the offset is measured.
5. The method for studying liquid viscosity coefficient by image acquisition according to claim 1, wherein the linear fitting formula of the displacement-time data of the small ball in step S53 is:
y＝v y .t+y 0
wherein y is the vertical (y direction) coordinate of the pellet in the image; v y Is the speed of the pellet in the vertical direction (y-direction); t is the falling time of the pellets; y is 0 Is the vertical (y-direction) coordinate of the pellet at time 0.
6. The method for studying a viscosity coefficient of a liquid by image acquisition according to claim 1, wherein the viscosity coefficient is calculated by the formula:
wherein ρ is the density of the pellets, ρ 0 The density of oil, g is gravity acceleration, v y The speed of the pellets, D is the diameter of the pellets, and D is the diameter of the double glass tube.
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Effective date of registration: 20231211 Address after: No. 309 South 2nd Road, Economic and Technological Development Zone (Longquanyi District), Chengdu City, Sichuan Province, 610199 Patentee after: SICHUAN SHIJI ZHONGKE PHOTOELECTRIC TECHNOLOGY Co.,Ltd. Address before: No. 519, Huixing Road, Ziliujing District, Zigong City, Sichuan Province Patentee before: Sichuan University of Light Chemical Technology |