Testing device for measuring plane global frictional force vector field, and working method

[0033] In order to facilitate the understanding of those skilled in the art, the present invention will be further described below in conjunction with the embodiments and the drawings, and the content mentioned in the embodiments does not limit the present invention.

[0034] Reference figure 1 As shown, a test device for measuring the friction force vector field on the surface of a flat plate of the present invention includes a downstream flat plate 1, a detachable blackened flat plate 2, a calibration line 3, a bracket 4, a light source 5, a movable hinge 6, and an angle disk 7. , Rotatable cantilever 8, adjustable connecting rod 9, camera connecting bracket 10, hinge connecting part 11, among which,

[0035] The downstream flat plate 1 is connected to the nozzle, and the connection is smoothly transitioned to generate a flow field; the detachable blackened flat plate 2 is embedded in the test area of ​​the downstream flat plate 1 to ensure that the upper surface of the detachable blackened flat plate 2 and the downstream flat plate 1 are flat ( No protrusions and depressions), fixed with screws; when preparing for the test, the detachable blackening plate 2 can be removed to facilitate experiment preparation; the upper surface of the detachable blackening plate 2 is smooth, which meets the requirements of liquid crystal spraying and avoids The problem of light reflection; the outer edge of the detachable blackening plate 2 is drawn with a red calibration line 3, and the detachable blackening plate is easy to disassemble, and its surface oxidation and blackening can make the contrast color of the shear-sensitive liquid crystal more obvious. Facilitate the camera diagonal and image calibration. Such as Figure 2a-Figure 2b Shown.

[0036] The rotatable cantilever 8 is connected to the bracket 4 through a movable hinge 6 and a hinge connecting part 11, the length of the rotatable cantilever 8 is less than half of the width of the bracket 4, and it can realize 360° free rotation. The angle plate 7 and the screw 12 are fixed and adjustable The angle of the cantilever 8 can be rotated, and the light source 5 is fixed under the bolt, such as image 3 As shown, it is a rotating part composed of the above-mentioned components. Ensure that the center of the light source 5, the center of the angle plate 7, the center of the movable hinge 6, and the center of the detachable blackening plate 2 are located within the same vertical line. The rotatable cantilever can achieve the camera's multi-view angle to obtain the liquid crystal color change characteristics under different observation angles, so that the magnitude and direction of the fluid wall friction can be measured

[0037] The angle disc 7 is engraved with an angle line 71, which can measure the rotation angle of the rotatable cantilever. Such as Figure 4 Shown.

[0038] The adjustable connecting rod 9 is connected to the rotatable cantilever 8, and a scale 81 is glued to one side of the rotatable cantilever 8, so that the position of the adjustable connecting rod 9 can be adjusted quantitatively. Such as Figure 5 Shown.

[0039] The camera connecting bracket 10 is connected to the adjustable connecting rod 9, and a scale 91 is attached to one side of the adjustable connecting rod 9, which can quantitatively adjust the vertical height of the camera. Such as Figure 5 Shown.

[0040] The bracket 4 is constructed with standard aluminum profiles to ensure strength and stability while reducing weight. The joints are connected with standard angle pieces 13, such as Image 6 Shown. The bracket 4 is fixed on the level ground, and the bracket is placed at the outlet of the nozzle. The light source 5 is fixed and suspended directly above the test area by the bracket 4 to generate a parallel light source.

[0041] The bracket 4, the rotatable cantilever 8, the movable hinge 6, the adjustable connecting rod 9, and the camera connecting bracket 10 are sprayed with matt black spray paint to avoid the interference of reflections on the test.

[0042] The test device of the present invention has simple structure and convenient operation and control. The tested plate can be used as a part of the measurement component, and the integrated design of measurement/flow wall can be realized. The measurement of the global surface friction force field can be achieved by spraying a certain range of liquid crystal coatings.

[0043] The working method of the test device for measuring the plane global friction force vector field of the present invention includes the following steps:

[0044] Step 1: Spray the liquid crystal evenly on the detachable blackened plate;

[0045] Step 2: Adjust the position of the bracket so that the center of the light source and the center of the detachable blackened plate are within the same vertical line;

[0046] Step 3: Adjust the camera connecting bracket and the adjustable connecting rod, fix and calculate the top angle of the camera;

[0047] Step 4: Perform a wind tunnel test. During the test, change the camera's circumferential observation angle and capture the image by rotating the rotatable cantilever;

[0048] Step 5: Calculate the friction force vector field according to the photos taken at different circumferential observation angles.

[0049] The step 1 is specifically: after the liquid crystal is evenly sprayed on the detachable blackened plate, the detachable blackened plate is fixed in the groove of the downstream plate with screws to ensure that the upper surface of the detachable blackened plate and the downstream plate are flat Smooth connection.

[0050] The step 3 is specifically: as the top view angle of the camera needs to be determined in advance and remains unchanged during the test, hang the camera on the camera connection bracket, adjust the vertical position of the camera connection bracket, and adjust the scale on the connecting rod The ruler reads the distance between the top of the camera connection bracket and the rotatable cantilever.

[0051] The step 4 is specifically: conducting a wind tunnel test. The test requires a 360° rotation of the camera’s circumferential observation angle. During the test, the camera’s circumferential observation angle is changed by rotating the rotatable cantilever and the image is captured. The angle of the angle is read and recorded by the angle disc.

[0052] The step 5 is specifically: changing the viewing angle of the photos taken at different circumferential observation angles using the calibration line, extracting the tone value of each photo for Gauss curve fitting, the symmetry axis of the fitting curve is the direction of friction, and the peak value of the curve is There is a corresponding relationship between the magnitude of the friction, and the friction vector field can be calculated.

[0053] The invention uses shear-sensitive liquid crystal to coat the surface of the model. Under normal parallel light irradiation, the color change of the liquid crystal and the size, direction and observation angle of the friction force show the following laws: the color of the liquid crystal coating observed at different circumferential observation angles can be Fitted by Gauss curve, the symmetry axis of the curve is the direction of the friction force, and there is a corresponding relationship between the peak value of the curve and the magnitude of the friction force, so as to calculate the friction force vector field.

[0054] There are many specific applications of the present invention. The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention. Improvements should also be regarded as the protection scope of the present invention.