Device and method for directly measuring shear resistance of sealed underwater wall surface

Abstract

The invention provides a device and a method for directly measuring shear resistance of a sealed underwater wall surface. The device comprises a square pipeline, a cover plate, a pressure sensor, a force transmission shaft, a sample carrying table and a to-be-measured sample piece. According to the invention, the flowing liquid completely immersing the sample piece to be tested is used for simulating underwater navigation conditions. By introducing flowing liquid into the pipeline, shear resistance is generated between the liquid and the to-be-measured sample piece, and the resistance is transmitted to the pressure sensor through the force transmission shaft, so that direct measurement of the underwater shear resistance is realized.

Description

Technical Field

[0001] The present invention aims to study detection problems in underwater engineering and liquid surface drag reduction, relates to underwater engineering and fluid drag reduction, and specifically relates to an underwater shear resistance measurement device and method. Background Art

[0002] In recent years, underwater drag reduction technology has attracted much attention due to its potential drag reduction effect. By imitating the surface structure of organisms in nature, such as shark skin and dolphin skin, the surface of underwater vehicles with drag reduction effect can be designed. In the research process of underwater drag reduction technology, it is necessary to design a resistance detection device to accurately measure the wall shear resistance in order to verify the drag reduction effect and optimize the design. However, the sealing of the direct force measuring device during the measurement process has always been a key technical difficulty, which directly affects the accuracy and stability of the measurement. Therefore, it is particularly important to develop a sealed experimental device for underwater wall shear resistance.

[0003] At present, scholars in related academic fields have developed a variety of technical methods for measuring underwater wall shear resistance. These methods are mainly based on the principle of mechanics, and directly measure the friction between the fluid and the wall through pressure sensors and other equipment. For example, the direct measurement method of pressure sensors is used to convert mechanical signals into electrical signals by combining pressure sensors with liquids, thereby realizing direct measurement of wall shear resistance, which is generally used for shear resistance measurement experiments on acrylic surfaces and lotus leaf surfaces. The fluid forms relative motion with the wall to be measured, which can reflect the changes in wall shear resistance in real time. However, this experimental device involves complex underwater operations and debugging processes, and requires the experimental device to be large enough so that pressure sensors can be installed inside the pipe; another method is the indirect resistance measurement method, which usually includes square pipes, cover plates, slider systems, force pressure sensors, and test samples. The square pipe is used to hold the flowing liquid, and the cover plate is used to close the pipe and install the slider system and force pressure sensor. The slider system can drive the sample to be tested to move relative to the liquid, thereby simulating the real underwater environment. This method has a simple structure and is easy to operate, but the error is large and the calculation process is cumbersome. The applicability and measurement accuracy of the measuring device will be limited.

[0004] In summary, the direct resistance measurement method using pressure sensors has high accuracy and is easy to observe, but has poor sealing, which affects the experimental operation and conclusions. The indirect method is costly, has large errors and low accuracy, and cannot be applied to all types of wall materials, thus limiting the scope of application of the measurement device. At present, there is no experimental device and method that can both simulate a good underwater flow experimental environment and accurately measure underwater wall resistance. Summary of the invention

[0005] The purpose of the present invention is to achieve a pressure sensor placed outside the pipeline while maintaining extremely high sealing and ensuring the normal flow of the fluid in the pipeline. To this end, the present invention provides a new method and device for measuring the shear resistance of underwater walls, which can immerse the sample specimen of the measured wall in the pipeline and place the pressure sensor itself outside the pipeline, and has good sealing and strong flowability, and is suitable for measuring micro friction force walls of millinewton and below.

[0006] The present invention is a novel underwater wall shear resistance detection device, which specifically comprises a square pipe and its cover plate, a sample carrier, a force transmission shaft, an elastic ring, an annular resin filling block, a sample to be tested, a sealing film, an elastic sealing ring, and a pressure sensor.

[0007] This test device uses a square pipe wall and a cover plate threaded nut connection, and the pressure sensor also uses a threaded nut connection method for the cover plate, that is, the pressure sensor, cover plate and pipe are fixed together. This method uses a sealing film, which has a very strong high sealing performance, and the pressure sensor, cover plate and pipe are all in a fixed state. It is a new innovation of the direct measurement method of the pressure sensor.

[0008] A detailed description of the internal devices and functions of the cover in this experimental device:

[0009] A rectangular groove for mounting a sample detection frame;

[0010] The through hole is used to connect the sample stage to the pressure sensor externally and cooperate with the annular resin filling block to press and fix the lower side of the sealing film;

[0011] This invention applies for a high-sealing integrated underwater wall shear resistance test method, including the following operation procedures:

[0012] After the fluid is immersed in the pipeline, the sample to be tested is completely immersed in the liquid;

[0013] Since the sample is completely fixed by the “U”-shaped cavity of the sample carrier and becomes one, the shear force generated on its surface is directly transmitted to the pressure sensor by the force transmission shaft;

[0014] Since the experimental device is precise and has high sealing performance, the underwater shear resistance of the sample surface can be directly read on the pressure sensor;

[0015] Compared with the traditional direct measurement device, this method has obvious advantages:

[0016] Due to the existence of its sealing ring, this experimental device has a high sealing design, which can effectively prevent the leakage of fluid during the measurement process and ensure the accuracy and reliability of the measurement results;

[0017] The integrated design makes the device compact, easy to install and carry, and suitable for simulating various complex underwater environments;

[0018] The integrated design also reduces the connections and gaps between the various components of the device, thereby reducing the measurement errors caused by loose connections or gap changes, which is a necessary requirement for measuring small shear resistance;

[0019] The transparent acrylic material of the square tube enables real-time monitoring of the wall shear resistance, making it easier to observe the stress conditions on the sample surface.

[0020] The presence of the annular resin filling block facilitates dismantling and installation, and improves its adaptability in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of a device for directly measuring underwater wall shear resistance in one embodiment of the present invention;

[0022] Figure 2 It is a cross-sectional schematic diagram of a device for directly measuring underwater wall shear resistance in one embodiment of the present invention;

[0023] Figure 3 A schematic diagram of the overall layout of a direct measurement device for underwater wall shear resistance in one embodiment of the present invention;

[0024] Figure 4 A schematic diagram of a cover plate of a device for directly measuring underwater wall shear resistance in one embodiment of the present invention;

[0025] It includes:

[0026] 1-square pipe; 2-cover plate; 3-sensor; 4-sealing film; 5-force transmission shaft; 6-elastic ring; 7-ring-shaped resin filling block; 8-sample to be tested; 9-ring groove; 10-through hole; 11-ring groove; 12-round hole; 13-rectangular groove; 14-cover plate sealing strip; 15-sample carrier; 16-fixed plate. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0028] like Figure 1 , Figure 2 , Figure 3 , Figure 4As shown, in an embodiment of the present invention, a sealed underwater wall shear resistance direct measurement device includes 1-square pipe; 2-cover plate; 3-pressure sensor; 4-sealing film; 5-force transmission shaft; 6-elastic ring; 7-annular resin filling block; 8-sample to be measured; 9-annular groove; 10-through hole; 11-annular groove; 12-round hole; 13-rectangular groove; 14-cover plate sealing strip; 15-sample loading platform; 16-fixing plate. The wall of the square pipe 1 is provided with an opening, and the cover plate 2 is placed at the opening and connected to the wall of the pipe by bolts.

[0029] A rectangular groove 13 is provided on the cover plate 2, and a through hole 10 is provided at the center of the rectangular groove. The axis center of the bottom cylinder of the force transmission shaft 5 is at the same position as the axis center of the circular hole, and the diameter of the circular hole is larger than the bottom cylinder of the force transmission shaft 5; the cover plate sealing strip 14 is used to seal the gap between the cover plate and the square pipe.

[0030] The force transmission shaft 5 has a cylinder with a diameter slightly smaller than the circular hole on its sunken surface, and a portion of the upper end of the cylinder is machined to form a ring groove 11 for fixing the elastic ring 6, and a flat surface is provided at the rear end close to the sensor side for connecting with the pressure sensor 3 using screws and nuts;

[0031] Specifically, the square pipe 1 can be a pipe container that can hold liquid and has an opening on one side wall, including flanges at both ends that can be connected to an external system. The liquid held can be water or other environmental liquids. By passing flowing liquid into the pipe, the working conditions of the sample to be tested in actual application can be more realistically simulated. The embodiment of the present application does not specifically limit the shape and material of the sample to be tested 8. Exemplarily, the sample to be tested 8 can be a sample with a curved surface to be tested.

[0032] In the embodiment of the present application, the cover plate sealing strip 14 can seal the gap between the cover plate and the sample frame, and does not produce any friction resistance effect on the shear force measurement. Under the above requirements, the embodiment of the present application does not make specific requirements on the shape and material of the cover plate sealing strip 14. For example, the cover plate sealing strip 14 can be a rubber film.

[0033] The sealed integrated underwater wall shear resistance direct measurement device and method described in one embodiment, the method of use is as follows:

[0034] A flowing liquid is introduced into the square pipe 1 until the test sample 8 and the force transmission shaft 5 are completely immersed in the flowing liquid;

[0035] The friction resistance between the test surface of the test sample 8 and the liquid is transmitted to the pressure sensor 3 through the force transmission shaft 5;

[0036] By acquiring the measurement data of the pressure sensor 3, the shear resistance between the sample 8 to be tested and the liquid is obtained;

[0037] A sealed underwater wall shear resistance direct measurement device and method process described in an embodiment: 1. Fix the sensor 3 on the fixing plate 16 with screws and nuts; 2. Insert the epoxy resin filling block 7 into the sealing film 4, and then insert it onto the force transmission shaft 5, and fix the sealing film 4 at the upper end with an elastic sealing ring 6; 3. Pass the force transmission shaft 5 through the circular hole and fix it to the sensor, and press the epoxy resin filling block 7 against the through hole 10 to fix the lower side of the sealing membrane. 4. Place the sample 8 to be tested on the sample carrier 15 and set it on a “U” shaped cavity frame for fixation; 5. Connect the square pipe 1 to the external system; 6. The flowing liquid is passed through, and the friction resistance between the surface of the sample 8 and the water is transmitted to the pressure sensor 3 through the force transmission shaft 5. By acquiring the measurement data of the pressure sensor 3, the friction resistance can be obtained; 7. Turn off the flowing water and release the water in the square pipe 1; 8. Loosen the bolts, remove the cover plate 2, and replace or remove the sample 8 to be tested.

Claims

1. A sealed underwater wall shear resistance direct measurement device, characterized in that: include: A square pipe (1) is provided with an opening on the lower wall of the square pipe (1), a cover plate (2) is provided on the opening and is placed at the opening, an annular groove (9) is provided on the connection surface between the cover plate (2) and the square pipe (1) and is used to place a cover plate sealing strip (14), a fixing plate (16) is provided perpendicular to the cover plate surface, the fixing plate (16) and the cover plate are an integrated structure in an "L" shape, a pressure sensor (3) is installed on the fixing plate (16), the two are fixed by threaded connection, a force transmission shaft (5) is fixed at the force measuring end of the pressure sensor (3), and the force transmission shaft (5) passes through the central passage of the rectangular groove (13) provided on the cover plate The hole (10) extends into the interior of the square pipe (1). A sealing film (4) is provided inside the square pipe (1). The lower end of the sealing film (4) is wrapped with an annular resin filling block (7). The outer diameter of the annular resin filling block (7) is the same as that of the through hole (10). The two are transitionally matched. The lower end of the sealing film (4) is fixed at the gap. An elastic sealing ring (6) is provided at the upper end of the force transmission shaft (5) to press the upper end of the sealing film (4). A sample carrier (15) is fixed at the upper end of the force transmission shaft (5). The two are connected by welding to form an integrated "T"-shaped structure. The sample carrier (15) is provided with a "U"-shaped cavity frame to fix the sample to be tested (8).

2. A sealed underwater wall shear resistance direct measurement device, characterized in that: The sample carrier (15) and the force transmission shaft (5) are an integrated structure in a "T" shape. The diameter of the lower force transmission shaft (5) is slightly smaller than the through hole (10) so that the lower force transmission shaft (5) passes through the through hole (10) and extends outward from the cover plate (2). The rear end of the force transmission shaft (5) close to the side of the pressure sensor (3) is set as a plane, and a circular hole (12) is provided on the surface and connected and fixed to the pressure sensor (3) by screws and nuts. The force transmission shaft (5) is provided with an annular groove (11) for fixing the elastic sealing ring (6).

3. A sealed underwater wall shear resistance direct measurement device as described in claim 1, characterized in that the square pipe (1) is used to carry water or other liquid flow, and the square pipe (1) and the cover plate (2) are connected by screws and nuts.

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