A droplet shear stress and deformation test device and test method

Abstract

The present invention discloses a droplet shear stress and deformation test device and a test method, which relates to the technical field of micro-droplet force analysis. The device includes a high-definition industrial camera, a three-axis displacement platform, a lifting table, a macro camera platform guide rail, a microscope lens, a placement table, a container, a fiber, a clam-shaped droplet, and a vision light source. The industrial camera is connected to the microscope lens. The high-definition industrial camera is on the macro camera platform guide rail, and the macro camera platform guide rail is on the lifting table. A container is arranged on the three-axis displacement platform. A fiber is placed inside the container, and the clam-shaped droplet is suspended on the fiber. A vision light source is arranged on the side of the clam-shaped droplet. The shear stress and surface tension received by the droplet are obtained through the following steps: adjusting the platform tilt angle and droplet mass to control the shear stress of the droplet cross-section; constructing a three-dimensional model based on the planar image of the droplet; calculating the cross-sectional area and mass of the droplet; measuring the shear stress and surface tension received by the droplet. The present invention is convenient to use and low in cost, and can accurately obtain the shear stress and surface tension received by the droplet.

Description

Technical Field

[0001] The present invention relates to the technical field of force analysis of micro-droplets in the gas-liquid separation process, and specifically relates to a droplet shear stress and deformation test device and a test method. Background Art

[0002] During the movement of droplets inside a porous medium, the droplets move along the inside of the porous medium driven by osmotic pressure, and the surface tension between the droplets and the porous medium is the main resistance hindering the movement of the droplets. Due to the complex internal structure and narrow size of the porous medium, it is very difficult to directly measure the deformation and surface tension of droplets inside the porous medium, and the test methods for the shear stress and surface tension received by the droplets are not yet clear. Summary of the Invention

[0003] To solve the above problems existing in the prior art, the present invention provides a droplet shear stress and deformation test device.

[0004] The technical solution of the present invention is as follows: A droplet shear stress and deformation test device includes a high-definition industrial camera, a three-axis displacement platform, a lifting platform, a macro camera platform guide rail, a microscope lens, a placement table, a container, a fiber, a clam-shaped droplet, a bottom plate, a vision light source, and a height adjustment airbag. The high-definition industrial camera is connected to the microscope lens, and the high-definition industrial camera is arranged on the macro camera platform guide rail. The macro camera platform guide rail is arranged on the lifting platform, and the lifting platform and the placement table are fixed on the bottom plate. A three-axis displacement platform is arranged on the placement table, and a container is arranged on the three-axis displacement platform. The container contains a fiber, and the clam-shaped droplet is suspended on the fiber. A vision light source is arranged on the side of the clam-shaped droplet, and height adjustment airbags are arranged at the four corners of the bottom plate.

[0005] The fiber is placed horizontally and has the same height as the center height of the high-definition industrial camera lens. A front view industrial camera is arranged on the front of the clam-shaped droplet, and a side view industrial camera is arranged on the side. The front view industrial camera and the side view industrial camera are aligned with the clam-shaped droplet, and vision light sources are respectively arranged on the side of the clam-shaped droplet away from the high-definition industrial camera.

[0006] A test method based on the droplet shear stress and deformation test device, the centers of two high-definition industrial cameras are aligned with the clam-shaped droplet. The front view and side view contours of the droplet are measured by high-definition magnification through the microscope lens connected to the high-definition industrial camera. The position of the high-definition industrial camera is finely adjusted through the macro camera platform guide rail and the lifting platform, and the relative position between the droplet and the microscope lens is adjusted through the three-axis displacement platform under the container.

[0007] The shear stress of the droplet cross-section is controlled by changing the pressure of the height-adjusting airbag to adjust the tilt angle of the bottom plate, so as to make the droplet tilt relative to the horizontal plane. Under the combined action of gravity and fiber capillary force, shear stress is generated inside the droplet. While the droplet deforms, ensure that the position of the droplet remains unchanged in the high-definition industrial camera, that is:

[0008] During the fiber tilting process, the side-view camera lens always remains parallel to the fiber axis, and the center of gravity of the droplet is within the side-view plane, avoiding measurement errors caused by non-parallelism between the side-view camera and the fiber;

[0009] During the fiber tilting process, the front-view camera lens is always perpendicular to the fiber axis, and the center of gravity of the droplet is also always within the front-view plane, accurately measuring the deformation of the droplet under the action of shear stress.

[0010] The three-dimensional structure of the droplet is reconstructed by the following method. According to the front view and side view of the droplet, identify the contour curve of the droplet. Taking the center of gravity of the droplet as the reference, establish a cylindrical coordinate system of the droplet as Figure 3 shown. Since the horizontal cross-section of the droplet tends to have the smallest surface area under the action of surface tension, the contour of the horizontal cross-section of the droplet is an ellipse. The major axis and minor axis radii of the ellipse are the contour widths of the front view and side view of the droplet respectively,

[0011]

[0012] where, r x is the contour width of the front view of the droplet; r y is the contour width of the side view of the droplet; α is the rotation angle of the droplet relative to the z-axis.

[0013] The cross-sectional area, surface area and volume at any point of the droplet are calculated by the following formulas:

[0014]

[0015] where, ΔA i is the cross-sectional area at point i of the droplet; ΔS i is the discrete surface area at point i of the droplet; ΔV i is the discrete volume at point i of the droplet.

[0016] The average shear stress acting on the horizontal cross-section of the droplet is:

[0017]

[0018] where, V i (i = 1~n) is the volume of the droplet below the horizontal cross-section; A j (j = 1~m) is the horizontal cross-sectional area of the droplet.

[0019] The surface tension acting on the droplet is:

[0020]

[0021] Among them, σ n Surface tension of the droplet; γ Surface tension coefficient; R Curvature radius of the droplet; θ Angle between the normal direction of the surface tension and the horizontal direction.

[0022] According to the force balance of the droplet, under static conditions, there is no shear stress inside the liquid. The shear stress on the droplet can only be balanced by the surface tension. The relationship between the surface tension and the shear stress on the horizontal cross-section of the droplet is:

[0023]

[0024] The present invention proposes a test method for measuring the shear stress and surface tension of a droplet on an inclined fiber. Under the conditions of the same material and physical property parameters, the test results of the surface tension and shear stress of the droplet on the fiber characterize the deformation process of the droplet inside the porous medium under the action of osmotic pressure. The present invention is easy to use and low in cost, and can accurately obtain the shear stress and surface tension received by the droplet. Brief Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the present invention;

[0026] Figure 2 It is a partially enlarged schematic diagram of the present invention;

[0027] Figure 3 It is a three-dimensional reconstruction diagram of the droplet;

[0028] In the figure: 1 - High-definition industrial camera, 2 - Three-axis displacement platform, 3 - Lifting platform, 4 - Macro camera rail, 5 - Microscopic lens, 6 - Placing table, 7 - Container, 8 - Fiber, 9 - Clam-shaped droplet, 10 - Bottom plate, 11 - Visual light source, 12 - Height-adjusting airbag. Detailed Embodiment

[0029] The following further describes the present invention with reference to the accompanying drawings.

[0030] Such as Figures 1-2As shown in the figure, a droplet shear stress and deformation test device includes a high-definition industrial camera 1, a three-axis displacement platform 2, a lifting platform 3, a macro cloud platform guide rail 4, a microscope lens 5, a placement table 6, a container 7, a fiber 8, a clam-shaped droplet 9, a bottom plate 10, a visual light source 11, and a height adjustment airbag 12. The high-definition industrial camera 1 is connected to the microscope lens 5, and the high-definition industrial camera 1 is arranged on the macro cloud platform guide rail 4. The macro cloud platform guide rail 4 is arranged on the lifting platform 3. The lifting platform 3 and the placement table 6 are fixed on the bottom plate 10. The three-axis displacement platform 2 is arranged on the placement table 6, and the container 7 is arranged on the three-axis displacement platform 2. The container 7 contains the fiber 8, and the clam-shaped droplet 9 is suspended on the fiber 8. Two visual light sources 11 are provided on the side of the clam-shaped droplet 9. Height adjustment airbags 12 are provided at the four corners of the bottom plate 10 for supporting the bottom plate 10.

[0031] The lower part of the high-definition industrial camera 1 is fixed on the slider of the macro cloud platform guide rail 4, and the high-definition industrial camera 1 can move back and forth along the macro cloud platform guide rail 4. The lifting platform 3 includes a housing, a screw rod, a handwheel, and a slider. The handwheel is connected to the screw rod, and the screw rod is screwed to the slider. The macro cloud platform guide rail 4 is fixed on the slider of the lifting platform 3. Rotating the handwheel drives the slider to lift and lower, realizing the up and down movement of the high-definition industrial camera 1.

[0032] The fiber 8 is placed horizontally at the same height as the center of the lens of the high-definition industrial camera 1. A front view industrial camera is provided on the front of the clam-shaped droplet 9, and a side view industrial camera is provided on the side. The front view industrial camera and the side view industrial camera are aligned with the clam-shaped droplet 9, and the front view industrial camera and the side view industrial camera are perpendicularly arranged. Visual light sources 11 are respectively provided on the side of the clam-shaped droplet 9 away from the high-definition industrial camera. A bracket is provided in the container 7, and both ends of the fiber 8 are fixed on the bracket, and the clam-shaped droplet 9 is suspended on the fiber 8.

[0033] A test method based on the droplet shear stress and deformation test device. The centers of the two high-definition industrial cameras 1 are aligned with the clam-shaped droplet 9. The front view and side view contours of the droplet are measured by high-definition magnification through the microscope lens 5 connected to the high-definition industrial camera 1. The position of the high-definition industrial camera 1 is finely adjusted through the macro cloud platform guide rail 4 and the lifting platform 3, and the relative position between the droplet and the microscope lens is adjusted through the three-axis displacement platform 2 below the container 7.

[0034] The shear stress and surface tension received by the droplet can be obtained through the following steps: 1. Adjust the platform tilt angle and droplet mass to control the shear stress of the droplet cross-section; 2. Construct a three-dimensional model based on the planar image of the droplet; 3. Calculate the cross-sectional area and mass of the droplet; 4. Measure the shear stress and surface tension received by the droplet.

[0035] The shear stress of the droplet cross-section is controlled by changing the pressure of the height-adjusting airbag 12 to adjust the tilt angle of the bottom plate 10, so as to tilt the mussel-shaped droplet 9 relative to the horizontal plane. Under the combined action of gravity and fiber capillary force, shear stress is generated inside the droplet. While the droplet deforms, ensure that the position of the mussel-shaped droplet 9 remains unchanged in the high-definition industrial camera 1, that is:

[0036] During the fiber tilting process, the side-view camera lens always remains parallel to the fiber axis, and the center of gravity of the droplet is in the side-view plane, avoiding measurement errors caused by non-parallelism between the side-view camera and the fiber;

[0037] During the fiber tilting process, the front-view camera lens is always perpendicular to the fiber axis, and the center of gravity of the droplet is also always in the front-view plane, accurately measuring the deformation of the droplet under the action of shear stress.

[0038] The three-dimensional structure of the droplet is reconstructed as follows. According to the front view and side view of the droplet 9, identify the droplet contour curve. Based on the center of gravity of the droplet, establish a cylindrical coordinate system for the droplet. Since the horizontal cross-section of the droplet tends to have the smallest surface area under the action of surface tension, the contour of the horizontal cross-section of the droplet is an ellipse. The major and minor axis radii of the ellipse are the contour widths of the front view and side view of the droplet,

[0039]

[0040] where, r x is the contour width of the front view of the droplet; r y is the contour width of the side view of the droplet; α is the rotation angle of the droplet relative to the z-axis.

[0041] The cross-sectional area, surface area and volume at any point of the droplet are calculated by the following formulas for the 3D discrete coordinates of the droplet:

[0042]

[0043] where, ΔA i is the cross-sectional area at point i of the droplet; ΔS i is the discrete surface area at point i of the droplet; ΔV i is the discrete volume at point i of the droplet.

[0044] The average shear stress acting on the horizontal cross-section of the droplet is:

[0045]

[0046] where, V i (i = 1~n) is the volume of the droplet below the horizontal cross-section; A j (j = 1~m) is the horizontal cross-sectional area of the droplet. The surface tension acting on the droplet is:

[0047]

[0048] Among them, σ n Surface tension of the droplet; γ surface tension coefficient; R radius of curvature of the droplet; θ angle between the normal direction of the surface tension and the horizontal direction.

[0049] According to the force balance of the droplet, under static conditions, the liquid inside does not bear shear stress, and the shear stress on the droplet can only be balanced by the surface tension. The relationship between the surface tension and the shear stress on the horizontal cross-section of the droplet is:

[0050]

Claims

1. A test method based on a droplet shear stress and deformation test device, characterized in that: The centers of two high-definition industrial cameras (1) are aligned with the clam-shell-shaped droplet (9). The front view and side view profiles of the droplet are measured by high-definition magnification through the microscopic lenses (5) connected to the high-definition industrial cameras (1). The position of the high-definition industrial cameras (1) is finely adjusted by the macro gimbal guide rail (4) and the lifting table (3). The relative position between the droplet and the microscopic lens is adjusted by the three-axis displacement platform (2) under the container (7). The shear stress and surface tension acting on the droplet are obtained through the following steps: 1) Adjust the platform tilt angle and the droplet mass to control the shear stress of the droplet cross-section; 2) Construct a three-dimensional model based on the planar image of the droplet; 3) Calculate the cross-sectional area and mass of the droplet; 4) Measure the shear stress and surface tension acting on the droplet; The three-dimensional structure of the droplet is constructed as follows. According to the front view and side view of the droplet (9), the contour curve of the droplet is identified. Based on the center of gravity of the droplet, a cylindrical coordinate system of the droplet is established. Since the horizontal cross-section of the droplet tends to have the minimum surface area under the action of surface tension, the contour of the horizontal cross-section of the droplet is an ellipse. The major axis and minor axis radii of the ellipse are the contour widths of the front view and side view of the droplet respectively. where r x is the width of the front view contour of the droplet; r y is the width of the side view contour of the droplet; α is the rotation angle of the droplet relative to the z-axis; The surface tension acting on the droplet is: Among them, σ n Surface tension of the droplet; γ surface tension coefficient; R radius of curvature of the droplet; θ angle between the normal direction of the surface tension and the horizontal direction; The cross-sectional area, surface area and volume at any point on the droplet are calculated from the 3D discrete coordinates of the droplet by the following formulas: where, ΔA i cross-sectional area at point i of the droplet; ΔS i discrete surface area at point i of the droplet; ΔV i discrete volume at point i of the droplet; The average shear stress acting on the horizontal cross-section of the droplet is: Among them, V i (i = 1 to n) is the volume of the droplet below the horizontal cross-section; A j (j = 1 to m) is the horizontal cross-sectional area of the droplet; According to the force balance of the droplet, under static conditions, the liquid does not bear shear stress inside, and the shear stress on the droplet can only be balanced by the surface tension. The relationship between the surface tension and the shear stress on the horizontal cross-section of the droplet is as follows:

2. The test method of a test device based on droplet shear stress and deformation as described in claim 1, wherein: The shear stress of the droplet cross-section is controlled as follows. The pressure of the height-adjusting airbag (12) is changed to adjust the tilt angle of the bottom plate (10), so that the droplet (9) is tilted relative to the horizontal plane. Under the combined action of gravity and fiber capillary force, shear stress is generated inside the droplet. While the droplet is deformed, the position of the droplet (9) in the high-definition industrial camera (1) is ensured to remain unchanged, that is: During the fiber tilting process, the side view camera lens is always parallel to the fiber axis, and the center of gravity of the droplet is in the side view plane, avoiding measurement errors caused by non-parallelism between the side view camera and the fiber; During the fiber tilting process, the front view camera lens is always perpendicular to the fiber axis, and the center of gravity of the droplet is also always in the front view plane, accurately measuring the deformation of the droplet under the action of shear stress.

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