An underwater 2D3C PIV closed-mirror pod and method of use

Abstract

This invention relates to an underwater 2D3C PIV enclosed reflector compartment and its usage method. It includes a support member, with a horizontally positioned reflector compartment fixed to the bottom of the support member. Two sets of reflector compartments are arranged opposite each other, and a lens and CCD camera are mounted at the head of each individual reflector compartment. While achieving resistance to water flow impact and ensuring the reflector's installation angle is not affected by external factors, it also protects the internal water quality from contamination by the water flow in the vast waters of the experimental environment, allowing for the encapsulation of bubble-free pure water into the device. This device and water filling method effectively solve the problem of filling a sealed container with pure water, achieving encapsulation and filtering out air bubbles, reducing the difficulty and workload of personnel operation, improving the image acquisition quality of the 2D3C PIV system during operation, and enhancing the reliability of the vision measurement system and the lifespan of key optical components.

Description

Technical Field

[0001] This invention relates to the field of marine hydrodynamic testing technology, and in particular to an underwater 2D3C PIV enclosed reflector compartment and its usage method. Background Technology

[0002] The workflow of an underwater 2D3C PIV system is as follows: First, tracer particles are seeded into the flow field to be measured. Then, a laser generator illuminates the flow field at least twice in a very short time interval (Δt) using a sheet light source. A camera then captures the position of the tracer particles under laser illumination. By analyzing the images captured under the two laser illuminations, the displacement of the tracer particles within time Δt can be determined. Subsequent image analysis techniques can then be used to obtain the velocity field of the fluid. Because it utilizes binocular vision imaging, it can synthesize two-dimensional information observed from different angles into three-dimensional information; therefore, two CCD (Charge Coupled Device) cameras are required. In practical applications, to provide watertight protection for the cameras and other electronic equipment, and to reduce interference from the underwater PIV components to the surrounding flow field, the cameras and other optical components are encapsulated in a metal tube shaped like a torpedo. Since both cameras in the underwater 2D3C PIV system photograph the laser-illuminated surface at a certain angle, meaning there is an angle between the camera's focal plane and the laser-illuminated surface, a mechanical mechanism is needed to adjust the angle of the lens in front of the camera to ensure that the camera's focal plane falls on the surface under test, according to the Scheimpflug Principle. This ensures that the camera's imaging plane, lens plane, and the surface under test intersect on the same straight line. Due to technological limitations, it is not possible to obtain a sufficiently small commercial camera, lens, and Scheimpflug angle adjustment mechanism while meeting a certain observation field size. In addition, to strictly control the size of the torpedo-shaped metal structure and avoid excessive interference with the surrounding flow field, a reflector section is placed in front of the lens to transmit the scattered light of the tracer particles to the lens and camera through transparent optical glass and a reflector. This method allows the camera and lens to be arranged along the central axis of the torpedo body, optimizing space utilization.

[0003] To address the impact of different media's (air and water) refractive indices on light propagation, the reflector section needs to be submerged in water. There are generally two methods to achieve this: First, the reflector section is almost completely enclosed. Upstream of the reflector, on the metal section, is a transparent optical glass panel. This glass blocks the impact of water flow on the reflector during testing, preventing slight changes in the reflective angle. Only a few small holes are opened on the four walls of the metal section. When the torpedo body is submerged, water from the pool or tank automatically fills the reflector section. However, this method allows water containing oil or other particulate impurities in the pool / tank to contaminate the optical glass, affecting image formation on the camera's image sensor. The image quality is also affected by the fact that air bubbles cannot be effectively prevented from forming inside the reflector section during the water filling process, thus affecting the imaging quality. Secondly, the reflector section is in a semi-open state and does not use transparent optical glass to block the impact of water flow. When the torpedo body is submerged underwater, the reflector section is automatically immersed in open water. This method faces the same problem as the previous one: oil or impurity particles from the surrounding water will contaminate the surface of the optical glass and cause the reflector to be impacted by water flow, resulting in a slight change in the installation angle of the reflector. All of these will lead to distortion of the final particle image and affect the test results.

[0004] In addition, the water in the pool or tank is usually from municipal tap water, which contains a considerable amount of air. At a certain time and location during the experiment, the light path may randomly encounter air bubbles in the water, thereby changing the direction of light path propagation and affecting the imaging results. Therefore, improving the water quality in the reflector compartment of the underwater 2D3C PIV system and eliminating air bubbles in the compartment is a major challenge. Summary of the Invention

[0005] To address the shortcomings of existing production technologies, the applicant provides an underwater 2D3C PIV enclosed reflector compartment and its usage method. This effectively solves problems such as water contamination from surrounding test objects and bubble interference in the reflector compartment of an underwater 2D3C PIV system used in deep-water towed pools or circulating water tanks for flow field testing. The method includes improving water cleanliness, ensuring the reflector compartment is filled with water, and removing air bubbles from the compartment.

[0006] The technical solution adopted in this invention is as follows:

[0007] An underwater 2D3C PIV enclosed reflector compartment includes a support member, a horizontally arranged reflector compartment is fixed at the bottom of the support member, two sets of reflector compartments are arranged opposite to each other, and a lens and a CCD camera are installed at the head of each reflector compartment.

[0008] The structure of the reflector compartment is as follows: it includes the main reflector compartment, with exhaust end sealing caps and optical transmission glass sealing caps fixedly installed at both ends of the main reflector compartment via threaded connections; the exhaust end sealing cap has two threaded through holes on its end face, and when the internal hexagonal sealing screws are inserted into the threaded holes, they need to be used with a No. 1 O-ring seal. Tightening or loosening these two internal hexagonal sealing screws allows water to be injected or drained into the reflector compartment; the left and right sides of the exhaust end sealing cap have external threads and annular grooves, and a No. 2 O-ring seal is placed in the annular grooves, and tightened with the adjacent metal compartment or reflector main compartment to achieve watertight protection; the optical transmission glass sealing cap includes an optical transmission glass sealing cap body, on which a circular optical transmission glass is pasted. The left and right sides of the optical transmission glass sealing cap body have external threads and grooves, and the same No. 2 O-ring seal is placed in the grooves, and tightened with the adjacent metal compartment or reflector main compartment to achieve watertight protection.

[0009] Its further technical solution lies in:

[0010] The lens includes a Scheimpflug adjustment mechanism.

[0011] The main body of the reflector is a one-piece structure.

[0012] The main body of the reflector consists of a main body shell and a rectangular optical transmission glass. The main body shell contains a reflector and a mounting base, and the two ends of the main body shell have internal threads.

[0013] The rectangular optical transmission glass is glued to the rectangular ring support of the main body shell of the reflector using industrial adhesive.

[0014] A method for using an underwater 2D3C PIV enclosed reflector compartment includes the following operating steps:

[0015] Step 1: First, assemble the optical transmission glass sealing cover and the reflector body together with threads, and use a No. 2 O-ring to ensure watertight protection between the two.

[0016] Step 2: Slowly pour the treated distilled water into the main chamber of the reflector using a small beaker. To minimize water splashing during this process, the main chamber of the reflector can be tilted appropriately. Stop pouring water when the water level is about 2cm away from the opening of the main chamber of the reflector.

[0017] Step 3: Assemble the exhaust end sealing cap and the main body of the rearview mirror using threads, and use a No. 2 O-ring to ensure watertight protection between the two.

[0018] Step 4: Use a small beaker to slowly pour the treated distilled water into the main body of the reflector through the two threaded holes on the vent end sealing cap. In order to minimize water splashing during this process, tilt the main body of the reflector appropriately. When the water fills the top space of the main body of the reflector, it will drive the air out through the two threaded holes. Stop pouring water when the water level is above the two threaded holes and about 1cm above the surface.

[0019] Step 5: Place the reflector section inside the stainless steel drum in the vacuum environment manufacturing equipment;

[0020] Step 6: There is a silicone sealing ring around the opening edge of the stainless steel bucket. An acrylic cover is placed on the stainless steel bucket. When the stainless steel bucket is evacuated, the acrylic cover tightly squeezes the stainless steel bucket due to the pressure difference between the inside and outside. The left and right ends of the pressure gauge are connected to the No. 1 switch valve and the No. 2 switch valve, respectively. The bottom of the pressure gauge is connected to a metal tube, which penetrates the acrylic cover and is inserted into the stainless steel bucket. The contact part between the metal tube and the acrylic cover plate has airtight protection measures. The rear end of the No. 1 switch valve is connected to a silencer. All pipes through which the air flows are made of plastic. In order to eliminate the air in the water in the reflector compartment, first set the No. 1 switch valve to the "closed" state and the No. 2 switch valve 103 to the "open" state. Then turn on the vacuum pump to evacuate the stainless steel bucket. During this process, the distilled water in the reflector compartment will continuously boil and bubbles will be generated one after another. In the early stage, the bubbles mainly contain air in the water. In the later stage, the bubbles mainly contain evaporated water vapor.

[0021] Step 7: In order to remove air from the water in the reflector compartment as thoroughly as possible, repeat the above vacuuming operation 4 to 5 times, each lasting 3 to 5 minutes, with an interval of 2 to 3 minutes between adjacent operations, so that the vacuum pump 105 works intermittently to prevent the equipment from overheating and causing malfunction.

[0022] Step 8: After the bubbles are eliminated, the pressure inside the stainless steel tank needs to be restored to normal pressure. Turn off the vacuum pump, immediately set valve number two to the "closed" position, and slowly open valve number one with a small opening. This effectively controls the speed at which outside air flows through the silencer, valve number one, pressure gauge, and stainless steel tank, preventing a large amount of air from rapidly entering the stainless steel tank and disturbing the water in the reflector compartment that has already had the air removed, thus causing bubbles to form again.

[0023] Step 9: When using the vacuum environment manufacturing equipment to remove air bubbles from the reflector compartment, some water evaporates in the vacuum environment and is pumped away by the vacuum pump. Also, some liquid water is carried away from the water surface by rising air bubbles when the water boils, splashing onto the bottom and walls of the stainless steel tank. Therefore, the liquid water level in the reflector compartment after removing air bubbles will inevitably be lower than before it was placed in the vacuum environment manufacturing equipment for air bubble removal. Use a small-capacity beaker to add water to the reflector compartment appropriately, then remove the reflector compartment from the stainless steel tank. Use two internal hexagonal sealing screws and a No. 1 O-ring to seal the water in the reflector compartment inside the cavity. Finally, pour out the excess water from the exhaust end sealing cap.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention has a compact and reasonable structure and is easy to operate. It uses a vacuum device to create a vacuum environment, which allows residual air bubbles in the reflector compartment to automatically detach from the water, reducing the difficulty of operation, improving efficiency, and ensuring the quality of the water in the compartment.

[0026] Because the entire 2D3C PIV system, including the reflector compartment, has a very compact structure, with the reflector and mounting base occupying most of the space in the main reflector compartment, this invention eliminates the need for large operating spaces and the risk of loosening or deformation of connections compared to degassing methods such as centrifugal stirring and manual shaking of the compartment. The non-contact vacuum environment degassing method does not require space for the compartment itself and will not cause loosening or deformation of mechanical connections.

[0027] This invention encapsulates the reflector and the water in the cavity, which has been filtered to remove air, inside the reflector compartment. This allows the reflector to be immersed in clean, uncontaminated water, protecting it from contamination and corrosion by impurities or oil in the water. It also avoids damage to the reflector's coating caused by repeated switching between air and water during operation or storage.

[0028] This invention relates to a device and method for ensuring the purity of the optical transmission medium in an underwater 2D3C PIV (Particle Image Velocity) system used in deep-water towing tanks and circulating water tanks. Specifically, it involves a device for encapsulating a reflector and a full-cavity water-filled chamber after filtering out air bubbles, as well as a method for removing air bubbles inherent in the water source and air bubbles formed during the process of injecting water into the reflector chamber. Attached Figure Description

[0029] Figure 1 This is a front view of the main observation part of the underwater 2D3C PIV of the present invention.

[0030] Figure 2 for Figure 1 Top view.

[0031] Figure 3This is a schematic diagram illustrating the focal plane adjustment principle under strabismus observation conditions according to the present invention.

[0032] (Scheimpflug Principle application, without reflector).

[0033] Figure 4 This is an assembly diagram of the reflector compartment section of the present invention.

[0034] Figure 5 for Figure 4 Exploded view.

[0035] Figure 6 This is an assembly diagram of the exhaust end sealing cap and sealing screw of the present invention.

[0036] Figure 7 This is an assembly diagram of the exhaust end sealing cap and the No. 2 O-ring seal of the present invention.

[0037] Figure 8 This is a schematic diagram of the assembly of internal components of the reflector body of the present invention.

[0038] Figure 9 This is a schematic diagram of the internal components of the optical transmission glass sealing cover of the present invention.

[0039] Figure 10 This is a schematic diagram of the internal components of the optical transmission glass sealing cover of the present invention.

[0040] Figure 11 This is an assembly diagram of the optical transmission glass sealing cover and the No. 2 O-ring seal of the present invention.

[0041] Figure 12 This is a flowchart of the distilled water treatment process of the present invention.

[0042] Figure 13 This is a schematic diagram of the vacuum environment manufacturing equipment of the present invention.

[0043] The components include: 1. Reflector compartment; 2. Exhaust end sealing cover; 3. Reflector main compartment; 4. Optical transmission glass sealing cover; 5. Socket head cap screw; 6. No. 1 O-ring seal; 7. No. 2 O-ring seal; 8. Kettle; 9. Small capacity beaker; 10. Vacuum environment manufacturing equipment; 11. CCD camera; 12. Lens; 13. Support components;

[0044] 301. Reflector main body shell; 302. Rectangular optical transmission glass;

[0045] 401. Optical transmission glass sealing cover body; 402. Circular optical transmission glass;

[0046] 101. Silencer; 102. No. 1 switch valve; 103. No. 2 switch valve; 104. Pressure gauge; 105. Vacuum pump; 106. Plastic air hose; 107. Acrylic cover plate; 108. Silicone sealing ring; 109. Stainless steel barrel; 110. Metal air hose. Detailed Implementation

[0047] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0048] like Figures 1-13 As shown, the underwater 2D3C PIV enclosed reflector section of this embodiment includes a support member 13. A horizontally arranged reflector section 1 is fixed at the bottom of the support member 13. Two sets of reflector sections 1 are arranged opposite to each other, and a lens 12 and a CCD camera 11 are installed at the head of each reflector section 1.

[0049] The structure of the reflector compartment 1 is as follows: it includes a reflector main compartment 3. Both ends of the reflector main compartment 2 are fixedly installed with an exhaust end sealing cover 2 and an optical transmission glass sealing cover 4 by threaded connection. There are two threaded through holes on the end face of the exhaust end sealing cover 2. When the internal hexagonal sealing screw 5 is inserted into the threaded hole, it needs to be used with a No. 1 O-ring 6. Tightening or loosening these two internal hexagonal sealing screws 5 allows water to be injected or drained into the reflector compartment 1. The left and right sides of the exhaust end sealing cover 2 have external threads and annular grooves. A No. 2 O-ring 7 is placed in the annular groove and tightened with the adjacent metal compartment or reflector main compartment 3 to achieve watertight protection. The optical transmission glass sealing cover 4 includes an optical transmission glass sealing cover body 401. A circular optical transmission glass 402 is pasted on the optical transmission glass sealing cover body 401. The left and right sides of the optical transmission glass sealing cover body 401 have external threads and grooves. The same No. 2 O-ring 7 is placed in the groove and tightened with the adjacent metal compartment or reflector main compartment 3 to achieve watertight protection.

[0050] Lens 12 includes a Scheimpflug adjustment mechanism.

[0051] The main body of the rearview mirror is a single-piece structure.

[0052] The main body of the reflector 3 consists of a main body shell 301 and a rectangular optical transmission glass 302. The main body shell 301 contains a reflector and a mounting base. Both ends of the main body shell 301 have internal threads.

[0053] The rectangular optical transmission glass 302 is attached to the rectangular annular support of the reflector main body shell 301 using industrial adhesive.

[0054] like Figure 1 and Figure 2As shown, the reflector in the reflector section 1 transmits the particle-scattered light of the measured area to the lens 12 and the CCD camera 11.

[0055] like Figure 3 As shown, based on the Scheimpflug Principle, by adjusting the positions of the imaging plane of the CCD camera 11, the lens plane 12, and the surface to be measured, the CCD camera 11 can focus on the surface to be measured even under oblique viewing conditions. Combined with the reflector section 1, the lens 12 and the CCD camera 11 can be aligned along... Figure 1 The central axis of the torpedo-shaped structural components is distributed to optimize the spatial layout.

[0056] like Figure 4 and Figure 5 As shown, the exhaust end sealing cover 2, the reflector main body 3, and the optical transmission glass sealing cover 4 are fixed to each other by threaded connection.

[0057] like Figure 6 As shown, the exhaust end sealing cover 2 has two threaded through holes on its end face. When the internal hexagonal sealing screw 5 is inserted into the threaded hole, it needs to be used with a No. 1 O-ring seal 6. Tightening or loosening these two internal hexagonal sealing screws 5 allows water to be injected or drained from the reflector section 1, and the air released from the water during the subsequent de-air bubble removal process is also discharged through these two threaded holes; Figure 7 As shown, the exhaust end sealing cover 2 has external threads and annular grooves on both sides. A second O-ring 7 is placed in the annular groove and tightened with the adjacent metal compartment or the main body compartment 3 of the reflector to achieve watertight protection, thereby preventing water leakage from the reflector compartment 1.

[0058] like Figure 8 As shown, the main body of the reflector 3 consists of a main body housing 301 and a rectangular optical transmission glass 302. The main body housing 301 contains the reflector and a mounting base, and both ends of the main body housing 301 have internal threads. The rectangular optical transmission glass 302 is glued to the rectangular annular support of the main body housing 301 using industrial adhesive, according to… Figure 4 and Figure 5 The assembly method of the reflector section shown uses rectangular optical transmission glass 302 to provide watertight protection, preventing the high-speed water flow from impacting the reflector during the test. It also serves to transmit light from the laser-illuminated surface to the reflector.

[0059] like Figure 9 and Figure 10As shown, the optical transmission glass sealing cover has a circular support on the side near the main body of the reflector 3. A circular optical transmission glass 402 is adhered to the circular support of the main body 401 of the optical transmission glass sealing cover using industrial adhesive. The circular optical transmission glass 402 provides watertight protection and also transmits the light reflected from the reflector to the rear lens 12. Figure 11 As shown, the optical transmission glass sealing cover 4 has external threads and grooves on both sides. The same No. 2 O-ring 7 is placed in the groove and tightened with the adjacent metal compartment or the main body compartment 3 of the reflector to achieve watertight protection, thereby preventing water leakage from the reflector compartment 1.

[0060] Since the 2D3C PIV system is generally used in a laboratory environment, the water source is usually municipal tap water. To maintain the refractive index match with the water quality under test conditions, tap water should be injected into the reflector compartment 1. However, tap water is generally greatly affected by local geographical conditions, and the water quality contains a large amount of minerals and organic matter, which can damage or obstruct the surface of the optical transmission glass and reflector. Therefore, it is recommended to use decalcified and deionized purified water. In addition, in order to improve the transmission efficiency of the reflector in the reflector body shell (including the reflector and mounting base) 301, a metal coating is usually applied to the reflector surface. However, if highly purified water with a conductivity of less than 5 μS / cm is used, it will damage the coating on the reflector surface. Therefore, highly purified water cannot be used. It is generally recommended to use commercially available distilled water as the primary water source injected into the reflector compartment 1.

[0061] Since commercially purchased distilled water still contains a small amount of oxygen, it needs to undergo deoxygenation treatment, such as... Figure 9 As shown, the untreated distilled water is boiled repeatedly 4 to 5 times through the kettle 8 and cooled to between 10°C and 25°C. Then, the cooled water in the kettle 8 is slowly poured into the small-capacity beaker 9 to minimize splashing and the generation of bubbles. The small-capacity beaker 9 is used to facilitate the injection of pure water into the reflector compartment 1.

[0062] according to Figure 3As shown, first, the optical transmission glass sealing cap 4 and the reflector body 3 are assembled together by threads, and the O-ring seal 7 is used to ensure watertight protection between them. Next, the treated distilled water is slowly poured into the reflector body 3 using a small-capacity beaker 9. During this process, in order to minimize water splashing, the reflector body 3 can be tilted appropriately. When the water level is about 2cm away from the opening of the reflector body 3, the pouring is stopped. Then, the exhaust end sealing cap 2 and the reflector body 3 are assembled together by threads, and the O-ring seal 7 is used to ensure watertight protection between them. Next, the treated distilled water is slowly poured into the reflector body 3 through the two threaded holes on the exhaust end sealing cap 2 using a small-capacity beaker 9. During this process, in order to minimize water splashing, the reflector body 3 can be tilted appropriately. When the water fills the top space of the reflector body 3, it will drive the air out through the two threaded holes. When the water level is above the two threaded holes and about 1cm above the surface, the pouring is stopped.

[0063] After completing the above operations, place the reflector section 1 into the stainless steel drum 109 within the vacuum environment manufacturing equipment 10. For example... Figure 10 As shown, there is a silicone sealing ring 108 around the opening edge of the stainless steel bucket 109. An acrylic cover plate 107 is placed on the stainless steel bucket 109. When a vacuum is drawn on the stainless steel bucket 109, the acrylic cover plate 107 tightly squeezes the stainless steel bucket 109 due to the pressure difference between the inside and outside, so that the silicone sealing ring 108 can better perform its sealing function. The left and right ends of the pressure gauge 104 are connected to the first switch valve 102 and the second switch valve 103, respectively. The bottom of the pressure gauge 104 is connected to a metal tube 110. The metal tube 110 penetrates the acrylic cover plate 107 and is inserted into the stainless steel bucket 109. The contact part between the metal tube 110 and the acrylic cover plate 107 has airtight protection measures. The rear end of the first switch valve 102 is connected to a silencer 101. All pipes through which the airflow passes are made of plastic air pipes 106. To remove air from the water in the reflector compartment 1, first set valve 102 to the "closed" position and valve 103 to the "open" position. Then, turn on vacuum pump 105 to evacuate the stainless steel tank 109. During this process, the distilled water in reflector compartment 1 will continuously boil, and bubbles will be generated. In the early stage, the bubbles mainly contain air from the water, while in the later stage, the bubbles mainly contain evaporated water vapor. To remove air from the water in reflector compartment 1 as thoroughly as possible, the above vacuuming operation can be repeated 4-5 times, each lasting 3-5 minutes, with an interval of 2-3 minutes between adjacent operations, so that vacuum pump 105 operates intermittently to prevent the equipment from overheating and causing malfunction. In addition, during the debubbling stage, it is essential to ensure that the two threaded holes of the exhaust end sealing cap 2 are submerged below the water surface. Otherwise, the stainless steel tank 109 must be restored to normal pressure, water must be added to reflector compartment 1 using a small-capacity beaker 9, and then the debubbling operation must be restarted.

[0064] After the bubbles are eliminated, the pressure inside the stainless steel tank 109 needs to be restored to normal pressure. The vacuum pump 105 should be turned off, and the second switch valve 103 should be immediately set to the "closed" state. The first switch valve 102 should be opened slowly, and the opening degree should be small. This can effectively control the speed at which outside air flows through the silencer 101, the first switch valve 102, the pressure gauge 104 and the stainless steel tank 109, so as to prevent a large amount of air from rapidly entering the stainless steel tank 109 and disturbing the water in the reflector compartment 1 that has already been purged of air, thus forming bubbles again.

[0065] When degassing the reflector compartment 1 using the vacuum environment manufacturing equipment 10, some water evaporates in the vacuum environment and is pumped away by the vacuum pump 105. Additionally, some liquid water is carried away by rising air bubbles during boiling, splashing onto the bottom and walls of the stainless steel container 109. Therefore, the liquid water level in the reflector compartment 1 after degassing will inevitably be lower than before it was placed in the vacuum environment manufacturing equipment 10. To be on the safe side, a small-capacity beaker 9 can be used to add water to the reflector compartment 1. Then, the reflector compartment 1 can be removed from the stainless steel container 109. (Refer to...) Figure 4 Use two internal hexagonal sealing screws and O-rings 6 to seal the water in the reflector section 1 inside the cavity, and finally pour out the excess water on the exhaust end sealing cap 2.

[0066] This invention employs a three-section threaded assembly method, combined with conventional O-ring seals, to achieve the encapsulation of the reflector and the water-filled cavity. Along the light propagation path, optical transmission glass is used at the junction of the reflector section and other sections or open water areas. This not only does not affect light propagation but also protects the reflector from the impact of open water flow during the experiment, preventing deviations in the reflection angle that could affect data quality and reduce the effective data area. It also prevents external contamination of the water inside the reflector cavity, thus affecting imaging quality. In addition, encapsulating the reflector in a water-filled cavity ensures that the mirror coating of the optical reflector specifically designed for laser reflection remains constantly wetted, effectively protecting the mirror coating.

[0067] This invention uses readily available commercially available distilled water as the primary water source. Through repeated boiling, the primary water source can be pretreated efficiently and economically, eliminating most of the air in the water.

[0068] This invention utilizes a simple vacuum environment to filter out air from the water in the reflector compartment, reducing the difficulty of operation and improving work efficiency. Compared with traditional manual shaking and centrifugal stirring to remove air bubbles, it has better practical effects and fewer application limitations.

[0069] This invention utilizes the threaded through-hole on the end cap surface to achieve both water replenishment and air venting, and also to achieve the purpose of filling the rearview mirror compartment with water in a simple and efficient manner.

[0070] This invention highlights its comprehensive protective measures and efficient, simple implementation process. The device itself, while resisting water flow impact and ensuring the reflector's installation angle is unaffected by external factors, also protects the internal water quality from contamination by the vast waterways in the experimental environment, allowing for the encapsulation of bubble-free pure water. This device and water filling method effectively solve the problem of filling a sealed container with pure water, achieving encapsulation and filtering out air bubbles, reducing the difficulty and workload of personnel operation, improving the image acquisition quality of the 2D3C PIV system, and enhancing the reliability of the vision measurement system and the lifespan of key optical components.

[0071] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A method for using an underwater 2D3C PIV enclosed reflector compartment, characterized in that: The method utilizes a vacuum environment manufacturing equipment (10), which includes a pressure gauge (104). The left and right ends of the pressure gauge (104) are respectively connected to a first switch valve (102) and a second switch valve (103). The bottom of the pressure gauge (104) is connected to a metal air pipe (110). The metal air pipe (110) penetrates an acrylic cover plate (107) and is inserted into a stainless steel barrel (109). The contact part between the metal air pipe (110) and the acrylic cover plate (107) has airtight protection measures. The rear end of the first switch valve (102) is connected to a silencer (101), and the second switch valve (103) is connected to a vacuum pump (105) through a plastic air pipe (106). The usage method includes the following steps: Step 1: First, assemble the optical transmission glass sealing cover (4) and the reflector main body (3) together by thread, and use the second O-ring seal (7) to ensure watertight protection between the two; Step 2: Use a small beaker (9) to slowly pour the treated distilled water into the main chamber (3) of the reflector. In order to minimize water splashing during this process, tilt the main chamber (3) of the reflector appropriately. Stop pouring water when the water level is about 2cm away from the opening of the main chamber (3). Step 3: Assemble the exhaust end sealing cap (2) and the main body of the reflector (3) by threading, and use the second O-ring seal (7) to ensure watertight protection between the two; Step 4: Use a small beaker (9) to slowly pour the treated distilled water into the main body chamber (3) of the reflector through the two threaded holes on the vent end sealing cap (2). In order to minimize water splashing during this process, tilt the main body chamber (3) of the reflector appropriately. When the water fills the top space of the main body chamber (3), it will drive the air out through the two threaded holes. Stop pouring water when the water level is above the two threaded holes and about 1 cm above the surface. Step 5: Place the reflector section (1) into the stainless steel drum (109) in the vacuum environment manufacturing equipment (10); Step 6: When the stainless steel barrel (109) is evacuated, the acrylic cover plate (107) tightly squeezes the stainless steel barrel (109) due to the pressure difference between the inside and outside. In order to eliminate the air in the water in the reflector section (1), first set the first switch valve (102) to the "closed" state and the second switch valve (103) to the "open" state, and then turn on the vacuum pump (105) to evacuate the stainless steel barrel (109). Step 7: Repeat the above vacuuming operation 4 to 5 times, each time lasting 3 to 5 minutes, with an interval of 2 to 3 minutes between two adjacent operations; Step 8: After the bubbles are eliminated, turn off the vacuum pump (105), immediately set the second switch valve (103) to the "closed" state, and slowly open the first switch valve (102), with a small opening, to effectively control the speed at which the outside air flows through the silencer (101), the first switch valve (102), the pressure gauge (104), and the stainless steel barrel (109). Step 9: Use a small beaker (9) to add water to the reflector compartment (1) appropriately, then remove the reflector compartment (1) from the stainless steel bucket (109), use two internal hexagonal sealing screws in conjunction with the first O-ring seal (6) to seal the water in the reflector compartment (1) in the cavity, and finally pour out the excess water on the exhaust end sealing cap (2).

2. The method of using the underwater 2D3C PIV enclosed reflector compartment as described in claim 1, characterized in that: The structure of the reflector compartment (1) is as follows: it includes a reflector main compartment (3), and the two ends of the reflector main compartment (3) are fixedly installed with an exhaust end sealing cover (2) and an optical transmission glass sealing cover (4) by threaded connection; there are two threaded through holes on the end face of the exhaust end sealing cover (2), and the internal hexagonal sealing screw (5) needs to be used in conjunction with the first O-ring seal (6) when inserted into the threaded hole. Tightening or loosening these two internal hexagonal sealing screws (5) allows water to be injected or drained into the reflector compartment (1); the left and right sides of the exhaust end sealing cover (2) have external threads and annular grooves. A second O-ring (7) is placed in the annular groove and tightened with the adjacent metal compartment or the main body compartment of the reflector (3) to achieve watertight protection; the optical transmission glass sealing cover (4) includes an optical transmission glass sealing cover body (401), a circular optical transmission glass (402) is pasted on the optical transmission glass sealing cover body (401), and external threads and grooves are opened on the left and right sides of the optical transmission glass sealing cover body (401). The same second O-ring (7) is placed in the groove and tightened with the adjacent metal compartment or the main body compartment of the reflector (3) to achieve watertight protection.

3. The method of using the underwater 2D3C PIV enclosed reflector compartment as described in claim 2, characterized in that: The lens (12) includes a Scheimpflug adjustment mechanism.

4. The method of using the underwater 2D3C PIV enclosed reflector compartment as described in claim 1, characterized in that: The main body of the reflector (3) is composed of a main body shell (301) and a rectangular optical transmission glass (302). The main body shell (301) contains a reflector and a mounting base. The two ends of the main body shell (301) are threaded.

Images