Sealed underwater wall surface shear resistance direct measuring device

Abstract

The utility model provides a sealed underwater wall surface shear resistance direct measuring device. 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. The device can simulate underwater navigation conditions through flowing liquid, so that shear resistance is generated between the liquid and a to-be-tested sample piece. And the resistance is transmitted to the pressure sensor through the force transmission shaft, so that the direct measurement of the underwater shear resistance is realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to underwater engineering and fluid drag reduction, in particular to underwater shearing resistance measuring device. BACKGROUND

[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 biological bodies in nature, such as shark skin and dolphin skin, a surface with drag reduction effect can be designed for underwater vehicles. In the research process of underwater drag reduction technology, a drag detection device needs to be designed 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, directly affecting the accuracy and stability of the measurement. Therefore, it is particularly important to develop a sealed underwater wall shear resistance experimental device.

[0003] Currently, for the measurement of underwater wall shear resistance, scholars in the relevant academic field have developed a variety of technical methods. These methods are mainly based on mechanical principles and use pressure sensors and other equipment to directly measure the friction between the fluid and the wall. For example, the pressure sensor direct measurement method uses a pressure sensor combined with a liquid to convert mechanical signals into electrical signals, thereby achieving direct measurement of wall shear resistance, which is generally used for measuring shear resistance on acrylic and lotus leaf surfaces. The relative movement between the fluid and the wall to be measured can reflect the changes in wall shear resistance in real time, but this experimental device involves complex underwater operations and debugging processes, and requires the experimental device to be large enough to allow the installation of pressure sensors inside the pipe; another way is indirect resistance measurement, which typically includes a square pipe, a cover plate, a slider system, a force pressure sensor, and a sample to be measured. The square pipe is used to contain the flowing liquid, and the cover plate is used to close the pipe and install the slider system and the force pressure sensor. The slider system can drive the sample to be measured to move relative to the liquid, thereby simulating the real underwater environment. This method is simple in structure and easy to operate, but has large errors and a complicated calculation process, limiting the applicability and measurement accuracy of the measuring device.

[0004] In summary, the pressure sensor direct method has high precision and is easy to observe, but has poor sealing, which affects the experimental operation and conclusion. The indirect method is costly, has large errors, and low precision, and cannot be applied to all types of wall materials, thereby limiting the application range of the measuring device. Currently, there is no experimental device that can simulate a good underwater flow experimental environment and accurately measure the underwater wall resistance. SUMMARY

[0005] The utility model discloses a purpose lies in still keeping very high sealing property and guaranteeing the normal flow of fluid in pipeline under the condition that pressure sensor is placed outside the pipeline. For this, the utility model provides a novel direct measurement device of measuring the shear resistance of underwater wall surface, can immerse the sample test piece of the measured wall surface in the pipeline, and the pressure sensor itself is placed outside the pipeline, and the sealing property is good, and the flowability is strong, is suitable for measuring the tiny friction stress wall surface of millinewton and below.

[0006] The utility model discloses a novel underwater wall surface shear resistance detection device, and it specifically contains square pipeline and its cover plate, sample loading platform, force transmission shaft, elastic ring, annular resin filling block, sample piece to be measured, sealing film, elastic sealing ring, pressure sensor.

[0007] The utility model discloses a square pipeline wall and cover plate threaded nut connection, and the pressure sensor is also connected to the cover plate threaded nut, that is, the pressure sensor, cover plate and pipeline are fixed as a whole. This method adopts sealing film, has very strong high sealing property, and the pressure sensor, cover plate and pipeline are all in fixed state, which is a novel innovation of direct measurement method of pressure sensor.

[0008] The cover plate internal device and function of the utility model are described in detail as follows:

[0009] Rectangular recess, used for installing sample detection frame.

[0010] Through hole, used for connecting pressure sensor to sample loading platform outward, and cooperating with annular resin filling block to press and fix the lower side of sealing film. DRAWINGS

[0011] Figure 1 It is the whole structure schematic diagram of the direct measurement device of underwater wall surface shear resistance in one embodiment of the utility model.

[0012] Figure 2 It is the cross section schematic diagram of the direct measurement device of underwater wall surface shear resistance in one embodiment of the utility model.

[0013] Figure 3 It is the whole layout schematic diagram of the direct measurement device of underwater wall surface shear resistance in one embodiment of the utility model.

[0014] Figure 4 It is the cover plate schematic diagram of the direct measurement device of underwater wall surface shear resistance in one embodiment of the utility model.

[0015] It contains:

[0016] 1 – Square pipe; 2 – Cover plate; 3 – Sensor; 4 – Sealing membrane; 5 – Force transmission shaft; 6 – Elastic ring; 7 – Annular resin filler block; 8 – Sample to be tested; 9 – Annular groove; 10 – Through hole; 11 – Annular groove; 12 – Round hole; 13 – Rectangular groove; 14 – Cover plate sealing strip; 15 – Sample stage; 16 – Fixing plate. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0018] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown in this embodiment of the invention, a sealed underwater wall shear resistance direct measurement device includes: 1-square pipe; 2-cover plate; 3-pressure sensor; 4-sealing membrane; 5-force transmission shaft; 6-elastic ring; 7-annular resin filler block; 8-sample to be tested; 9-annular groove; 10-through hole; 11-annular groove; 12-round hole; 13-rectangular groove; 14-cover plate sealing strip; 15-sample stage; 16-fixing plate. The square pipe 1 has an opening in its wall, and the cover plate 2 is placed at the opening and bolted to the pipe wall.

[0019] 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 bottom cylindrical axis of the force transmission shaft 5 is in the same position as the axis of the circular hole, and the diameter of the circular hole is larger than the bottom cylindrical axis 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.

[0020] The force transmission shaft 5 has a cylinder on its lower surface. The outer diameter of the cylinder is smaller than the inner diameter of the circular hole, so that the force transmission shaft can move axially in the circular hole. A portion of the upper end of the cylinder is machined off to form an annular groove 11 for fixing the elastic ring 6. The tail end near the sensor is set as a flat surface for connecting with the pressure sensor 3 by screws and nuts.

[0021] Specifically, the square pipe 1 can be a liquid-containing container with an opening on one side wall, including flanges at both ends for connecting to external systems. The liquid can be water or other ambient liquids. By circulating liquid through the pipe, the working conditions of the sample under test in actual applications can be simulated more realistically. This application embodiment does not specifically limit the shape and material of the sample 8 under test. For example, the sample 8 under test can be a sample with a curved surface.

[0022] In the embodiments 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 have any impact on the frictional resistance of the shear force measurement. Under the above requirements, the shape and material of the cover plate sealing strip 14 are not specifically required. For example, the cover plate sealing strip 14 can be a rubber film.

Claims

1. A sealed direct measurement device for wall shear stress in water, characterized by, It includes: Square pipe (1), in the lower wall of square pipe (1) is provided with opening, opening is provided with cover plate (2) is placed in the opening, annular groove (9) is arranged on the connecting surface of cover plate (2) and square pipe (1), for placing cover plate sealing strip (14), it is provided with fixed plate (16) on the cover plate surface vertically, the fixed plate (16) and cover plate are integral structure and are in the shape of "L", pressure sensor (3) is installed on the fixed plate (16), both are fixed by screw connection, force transmission shaft (5) is fixed on the force measuring end of pressure sensor (3), force transmission shaft (5) extends into square pipe (1) inside through the through hole (10) in the center of rectangular recess (13) provided on the cover plate, square pipe (1) is provided with sealing membrane (4) inside, the lower end of sealing membrane (4) is wrapped annular resin filling block (7), the outer diameter size of annular resin filling block (7) is same with the through hole (10), both are transition fit, sealing membrane (4) lower end is fixed at the gap, elastic sealing ring (6) is arranged on the upper end of force transmission shaft (5) to compress and seal the upper end of sealing membrane (4), force transmission shaft (5) upper end is fixed with sample loading platform (15), both are connected by welding, and form integral "T" shape structure, the sample loading platform (15) is provided with "back" shaped cavity frame to fix the measured sample (8).

2. The apparatus of claim 1, wherein, The sample loading platform (15) and force transmission shaft (5) are integral structure and are in the shape of "T", the diameter of lower force transmission shaft (5) is less than the through hole (10) to pass through the through hole (10) and extend out of the cover plate (2), and the tail is arranged as a plane close to the side of the pressure sensor (3), and the circular hole (12) is arranged on the plane and connected and fixed with the pressure sensor (3) by screw nut, the annular groove (11) is arranged on the force transmission shaft (5) for fixing the elastic sealing ring (6).

3. A sealed, direct shear resistance measurement device for underwater walls according to claim 1 or claim 2, characterised in that, The square pipe (1) is used for carrying water flow, and the square pipe (1) and the cover plate (2) are connected by screw nut.

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