EP4640952A1

EP4640952A1 - Underwater cover device

Info

Publication number: EP4640952A1
Application number: EP25168144.1A
Authority: EP
Inventors: Xin Li
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2024-04-09
Filing date: 2025-04-03
Publication date: 2025-10-29
Also published as: CN118345877A; JP2025160104A; US20250313317A1

Abstract

The invention discloses an underwater cover device, comprising a cover body and a gas source connected to the cover body. The cover body has an open end face directed towards an underwater surface, forming a gap between the open end face and the underwater surface. A rotating water flow is formed inside the cover body, and the gas source supplies air into the cover body. The rotating water flow prevents the air from escaping through the gap between the cover body and the underwater surface, thereby forming a water-free space on the underwater surface. This device is applicable to underwater surfaces at any inclination angle and can effectively establish a water-free space even if there is a gap or no contact between the underwater cover device and the underwater surface, demonstrating excellent applicability.

Description

Technical Field

The invention belongs to the field of underwater construction technology and relates to an underwater cover device.

Background Art

When conducting inspection or construction work on solid surfaces underwater (such as ship hulls, dam surfaces, etc.), the following problems are encountered:

1. When observing surfaces in turbid water, the turbidity reduces the effectiveness of lighting on the surface and weakens the reflection of light, making it difficult for cameras to capture clear images of the surface.
2. During underwater welding (e.g., underwater wet welding), the welding area is always in contact with water, causing rapid cooling of the weld due to water's thermal conductivity, leading to brittleness and reduced strength of the weld.

These issues arise because water is present near the surface. If a water-free space can be created near the surface, these problems can be resolved.
Chinese Patent CN202310964286.4 discloses a device for creating a water-free space in an underwater environment. The invention is a steel cofferdam used for underwater construction. The technology involves setting up a cofferdam structure underwater and then pumping out the water inside to create a water-free space, as shown in Figure 1. The air pressure inside the cofferdam is equivalent to atmospheric pressure, so the lower part of the cofferdam structure must maintain a good seal with the underwater solid surface. Otherwise, the pressure difference between the inside and outside of the cofferdam will force water into the cofferdam. This leads to a problem: the cofferdam structure cannot be moved.
To solve this problem, a cover body can be set up underwater, filled with air, as shown in Figure 2. In Figure 2, the cover body is in contact with the underwater solid surface. In reality, the contact surface cannot be perfectly smooth, so there will inevitably be gaps between them. Air pushes water out of the gap between the cover body and the underwater solid surface, creating a water-free space on the solid surface. However, this method has the following issues:

1. When the cover body moves away from the solid surface (as shown in Figure 3), there is a gap between the cover body and the solid surface, meaning they are not in contact. This creates a large gap between them, forming a layer of water with a thickness approximately equal to the distance between the cover body and the solid surface. This makes it impossible to form a water-free space on the solid surface.
2. If the solid surface is not horizontal, some air will escape through the gap between the cover body and the solid surface due to buoyancy, allowing water to enter the cover body, as shown in Figure 4. Even if the cover body and the solid surface are in contact, the contact surface cannot be perfectly smooth, so gaps will still exist. Therefore, air inside the cover body will still escape.

Summary of the Invention

The purpose of the invention is to address the shortcomings of existing technologies by providing an underwater cover device that can effectively create a water-free space near an underwater surface, facilitating underwater surface construction or inspection.
The technical solution of the invention is as follows:
An underwater cover device comprises a cover body and a gas source connected to the cover body. The cover body has an open end face directed towards an underwater surface, forming a rotating water flow inside the cover body. The gas source supplies air into the cover body, and the rotating water flow prevents the air from escaping through the gap between the open end face and the underwater surface, thereby forming a water-free space on the underwater surface.
In the above technical solution, the gas source includes a gas flow regulating mechanism for controlling the flow rate of air supplied into the cover body, thereby controlling the volume of air inside the cover body.
Further, one or more nozzles are arranged inside the cover body, with the nozzles being tangential to the inner wall surface of the cover body. Water is injected into the cover body through the nozzles and flows along the inner wall surface, forming a rotating water flow inside the cover body.
Further, the gas source is connected to the cover body through the nozzles, and air is supplied into the cover body through the nozzles.
Further, the cover body is provided with air holes, and the gas source is connected to the air holes to supply air into the cover body through the air holes.
Further, an annular partition is arranged inside the cover body, separating the water-free space from the rotating water flow.
Further, blades are arranged inside the cover body, and a motor drives the blades to rotate, causing the water inside the cover body to rotate and form a rotating water flow. The rotating water flow prevents the air from escaping through the gap between the open end face and the underwater surface.
Further, the cover body is provided with drainage channels, and part of the water inside the cover body is discharged through the drainage channels.
Further, the device also comprises one or more air chambers connected to the air region inside the cover body. Water in the air chambers flows into the cover body while air enters the air chambers, forming a water-free space inside the air chambers.
Compared to existing technologies, the invention has at least the following beneficial effects:

1. Even if there is a gap between the underwater cover device and the underwater surface, the device can still create a water-free space on a non-horizontal underwater surface.
2. Even if the underwater cover device is not in contact with the underwater surface, the device can still create a water-free space on the underwater surface. Therefore, the underwater cover device can move on the underwater surface without causing friction or wear.

Description of the Drawings

Figure 1 is a schematic diagram of a cofferdam structure in the prior art.
Figure 2 is a schematic diagram of a simple underwater cover structure.
Figure 3 is a schematic diagram of the cover body moving away from the underwater solid surface.
Figure 4 is a schematic diagram of an inclined underwater solid surface.
Figure 5 is a schematic diagram of the underwater cover device according to Embodiment 1 of the invention, with the left side showing a front sectional view and the right side showing a right sectional view.
Figure 6 is a schematic diagram of the drainage channels on the cover body.
Figure 7 is a schematic diagram of one connection method of the air chamber.
Figure 8 is a schematic diagram of another connection method of the air chamber.
Figure 9 is a variation of the air chamber.
Figure 10 is another schematic diagram of the underwater cover device of the invention, with the left side showing a front sectional view and the right side showing a right sectional view.
Figure 11 is a schematic diagram of another method of injecting air from the gas source.
Figure 12 is a schematic diagram of the underwater cover device according to Embodiment 5 of the invention, with the left side showing a front sectional view and the right side showing a right sectional view.
Figure 13 is a schematic diagram of the application of the underwater cover device on an inverted underwater solid surface.

In the drawings: 1. Cover body, 2. Open end face, 3. Gas source, 4. Air hole, 5. Nozzle, 6. Underwater solid surface, 7. Gap, 8. Air chamber, 9. Connecting hole, 10. Mechanical arm and working tool, 11. Blade, 12. Motor, 13. High-pressure water, 14. Pipeline, 15. Air, 16. Drainage channel, 17. Annular partition, 18. Rotating water flow, 19. Cofferdam structure, 20. Water.

Detailed Description

The technical solution of the invention will be further described in detail below with reference to the drawings and specific embodiments.
As shown in Figure 4, if a simple cover body is used to create a water-free space, the air, being less dense than water, can easily escape through the gap between the cover body and the underwater solid surface due to buoyancy. This is the root cause of the problems in the prior art. Therefore, the invention proposes a novel concept: using the inertial force of rotating water flow to create a pressure gradient, which is then used to prevent air inside the cover body from escaping. Based on this concept, the invention provides an underwater cover device that can create a water-free space on an underwater surface. The device comprises a cover body and a gas source connected to the cover body. The cover body has an open end face directed towards the underwater surface, with a gap between the open end face and the underwater surface. A rotating water flow is formed inside the cover body, and the gas source supplies air into the cover body. The rotating water flow prevents the air from escaping through the gap, thereby forming a water-free space on the underwater surface.

Embodiment 1

Figure 5 is a schematic diagram of Embodiment 1 of the invention. The figure includes a cover body 1 and a gas source 3. The cover body 1 has an open end face 2, and the cross-section of the cover body is circular. One or more nozzles 5 are arranged on the wall surface of the cover body 1, with the nozzles being tangential to the inner wall surface of the cover body. High-pressure water 6 is injected into the cover body 1 through the nozzles 5, and the water flows along the circular wall surface of the cover body, forming a rotating water flow inside the cover body. The rotating water flow generates centrifugal inertial force, creating a pressure gradient inside the water flow, with the pressure on the outer side of the rotating water flow being higher than that on the inner side.
In this embodiment, there is a gap 7 between the cover body 1 and the underwater solid surface 6. Even if the cover body and the solid surface are in contact, the contact surface cannot be perfectly smooth, so gaps will inevitably exist. If the cover body and the solid surface are not in contact, the distance between them will create a larger gap. Water is continuously injected into the cover body through the nozzles and discharged through the gap between the cover body and the underwater surface.
The cover body 1 is provided with an air hole 4. The air hole 4 is connected to the gas source 3 via a tube. The gas source 3 injects a certain volume of air 15 into the cover body through the air hole. The air pushes part of the water inside the cover body into the gap and discharges it.
Next, the connection between the cover body and the gas source is cut off, meaning the gas source stops supplying air to the cover body. Inside the cover body, because air is less dense than water, it cannot pass through the rotating water flow and thus cannot escape through the gap. Taking a bubble as an example, if a bubble enters the rotating water flow, it will be subjected to buoyancy, gravity (which is negligible), centrifugal inertial force (as the bubble rotates with the water flow), and the pressure gradient force from the rotating water flow. The buoyancy and centrifugal inertial force will push the bubble outward, while the pressure gradient force will prevent the bubble from escaping. Since water is much denser than air, and as long as the water flow's rotational speed is fast enough, the pressure gradient force can far exceed the sum of the bubble's centrifugal inertial force and buoyancy. Therefore, the bubble will move inward under the pressure gradient force, meaning it cannot pass through the rotating water flow and escape through the gap 7 between the cover body and the underwater solid surface. As a result, a certain volume of air gathers in the center of the cover body 1, forming a water-free space on the underwater solid surface. The size of the water-free space can be adjusted by controlling the volume of air injected.
When maintaining the water-free space inside the cover body for a long time, we observed that the water-free space gradually decreases. After analysis, the reasons are: 1) Air slowly dissolves into the water and is discharged with the water flow; 2) Tiny bubbles form at the interface between the air and the rotating water flow, and these bubbles are carried away by the water flow. This may be because the surface tension between the tiny bubbles and the water flow is not negligible, balancing the pressure gradient force of the rotating water flow. To maintain the size of the water-free space inside the cover body, the gas source can periodically supply a certain volume of air to the cover body or continuously supply air at a very low flow rate. Therefore, the gas source also needs to include a gas flow regulating mechanism to control the flow rate of air supplied to the cover body, thereby controlling the volume of air inside the cover body. The gas source 3 can be an air compressor on the water surface or a gas cylinder. This embodiment uses a gas cylinder as an example. The gas pressure inside the cylinder must be higher than the pressure inside the cover body to supply gas to the cover body. The outlet of the gas cylinder is equipped with a switch valve. When the switch valve is opened, air is discharged from the cylinder into the cover body, gathering in the center of the cover body and forming a water-free space. The flow rate and duration of air injection can be controlled by the switch valve, thereby controlling the volume of air inside the cover body and adjusting the size of the water-free space.
The distance between the cover body 1 and the underwater solid surface 6 affects the rotating water flow inside the cover body. If the distance is large, the gap 7 will be large, and the water jet from the nozzles 5 may not form a sufficient rotating water flow inside the cover body. As a result, air inside the cover body may escape through the rotating water flow under the influence of buoyancy and centrifugal inertial force, making it impossible to form a stable water-free space inside the cover body. In practical applications, the distance between the cover body 1 and the underwater solid surface 6 can be adjusted through multiple experiments based on actual conditions.
In Figure 6, the cover body 1 is in contact with the underwater solid surface 6. Since the actual surface cannot be perfectly smooth, there will inevitably be a small gap 7 between them. However, this small gap makes it difficult for water inside the cover body to be discharged, potentially causing issues such as increased pressure inside the cover body and a longer time required to form the water-free space. To solve this problem, drainage channels 16 are provided on the cover body 1, connecting the water inside the cover body to the external environment. The rotating water flow is smoothly discharged through the drainage channels 16, preventing high pressure from forming inside the cover body. Additionally, when the gas source supplies air to the cover body, the water displaced by the air is also smoothly discharged through the drainage channels 16, allowing the water-free space to form quickly.
In this embodiment, the air hole 4 is located at the center of the cover body 1. Since the invention uses the pressure gradient force of the rotating water flow to gather air in the center of the cover body, the air hole 4 can also be located at a non-central position on the cover body 1.

Embodiment 2

In this embodiment, an air chamber 8 is arranged between the cover body 1 and the gas source 3. The air chamber 8 is connected to the water-free space inside the cover body 1 through a connecting hole 9. All or part of the water in the air chamber 8 can flow into the cover body 1 through the connecting hole 9 and be discharged with the rotating water flow, while air from the cover body 1 enters the air chamber 8 through the connecting hole 9, forming a water-free space inside the air chamber.
In the example shown in Figure 7, the air chamber 8 is connected to the inside of the cover body 1 through a pipeline and the connecting hole. Water in the air chamber 8 flows into the cover body 1 under the influence of the water level difference and is discharged with the rotating water flow. At the same time, air from the cover body 1 enters the air chamber 8, forming a water-free space inside the air chamber.
Figure 8 shows another connection method for the air chamber 8. The air chamber 8 is arranged between the gas source 3 and the cover body 1. The gas source 3 is connected to the air chamber 8 through the connecting hole, and the air chamber 8 is connected to the cover body 1 through the air hole 4. Air from the gas source 3 flows through the air chamber and into the cover body 1. During this process, the air displaces water from the air chamber, forming a water-free space inside the air chamber.
Figure 9 shows a variation of Figure 8. The diameter of the air hole 4 is increased, and the air chamber 8 is arranged on the cover body 1. As a result, the air chamber 8 and the air region inside the cover body 1 form a large water-free space. This allows for the placement of larger devices (such as mechanical arms and welding tools) within this space, enabling operations on the water-free solid surface (e.g., spraying, welding, etc.). This solves the problems associated with traditional underwater operations in water-filled environments, such as the brittleness and reduced strength of welds in underwater wet welding.

Embodiment 3

This embodiment uses a different method to generate the rotating water flow inside the cover body. As shown in Figure 10, blades 11 are arranged inside the cover body 1, and a motor 12 drives the blades to rotate. The water inside the cover body 1 is driven by the blades, forming a rotating water flow. The gas source 3 injects a certain volume of air into the cover body 1 through the air hole 4, causing the air to gather in the central region and form a water-free space. The principle is the same as in Embodiment 1 and will not be repeated here.
The distance between the cover body 1 and the underwater solid surface 6 affects the rotating water flow inside the cover body. If the distance is large, the gap will also be large. The blades 11 cannot effectively drive the water inside the cover body to form a sufficient rotating flow, causing the air inside the cover body to escape through the rotating water flow under the influence of buoyancy and centrifugal inertial force. As a result, a stable water-free space cannot be formed inside the cover body. In practical applications, the distance between the cover body 1 and the underwater surface 6 can be adjusted through multiple experiments based on actual conditions.
In this embodiment, the air hole 4 is located at a non-central position on the cover body 1. Since the invention uses the pressure gradient force of the rotating water flow to gather air in the center of the cover body, the position of the air hole 4 in this embodiment does not affect the formation of the water-free space.

Embodiment 4

As shown in Figure 11, this embodiment differs from Embodiment 1 in that the gas source 3 and the high-pressure water 13 share a common pipeline connected to the tangential nozzles 5. The cover body 1 is submerged in water. High-pressure water 13 flows through the pipeline and the tangential nozzles, forming a rotating water flow inside the cover body 1. The gas source 3 injects a certain volume of air into the pipeline, and the air enters the cover body with the water flow, gathering in the central region and forming a water-free space.

Embodiment 5

Embodiments 1 and 2 use tangential nozzles to generate the rotating water flow inside the cover body. One side of the rotating water flow is the inner wall of the cover body, and the other side is air. The air has a weak constraining effect on the water flow, causing the water flow to expand toward the air side. This increases the cross-sectional area of the water flow, reducing its velocity and weakening the centrifugal inertial force and pressure gradient of the rotating water flow. Additionally, the large contact area between the rotating water flow and the air allows air to dissolve into the water or form tiny bubbles, gradually carrying away the air in the water-free space. To maintain the volume of the water-free space, the gas source must continuously supply air to the cover body.
As shown in Figure 12, this embodiment includes an annular partition 17 inside the cover body to separate the rotating water flow 18 from the air in the water-free space 15. The annular partition serves the following purposes:

1. The annular partition and the inner wall of the cover body form an annular flow channel. The water flows within this channel, constrained by the inner wall of the cover body and the annular partition. By designing the radius of the annular partition, the cross-sectional area of the flow channel can be adjusted, thereby changing the velocity of the rotating water flow. For example, with a constant water supply, a smaller cross-sectional area results in a higher water velocity, increasing the centrifugal inertial force of the rotating water flow and better preventing the air in the water-free space from escaping.
2. The annular partition separates the rotating water flow from the air in the water-free space, reducing the contact area between them. This inhibits the escape of air through the formation of tiny bubbles or dissolution into the water.

In the embodiments described in this specification, the underwater solid surface is a vertical wall, meaning the inclination angle of the underwater surface is 90 degrees. The principle of the invention can be applied to underwater surfaces at any inclination angle. Even on an inverted underwater surface, as shown in Figure 13, the device can create a water-free space.
It can be seen that the device of the invention uses the rotating water flow inside the cover body 1 to prevent the air inside the cover body from escaping. Even if there is a certain distance between the cover body 1 and the underwater solid surface 6, the invention can still create a rotating water flow inside the cover body. Therefore, the cover body 1 and the underwater solid surface 6 can be in a non-contact state. This allows the cover body 1 to move frictionlessly on the underwater solid surface 6 while still creating a water-free space on the underwater surface. This is particularly useful in practical applications. For example, a camera can be placed inside the cover body to capture images of the underwater surface. The underwater cover device can be mounted on an underwater wall-climbing robot, allowing the robot to move quickly along the surface and continuously capture images without contact.
In the description of the invention, water and air are used as examples. The water can be replaced with other liquids, and the air can be replaced with other gases. The invention uses the rotating flow of a liquid to prevent the gas inside the cover body from escaping, and this principle remains unchanged regardless of the type of liquid or gas used.
The above-described embodiments are only some of the preferred implementations of the invention and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention. Therefore, any technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the invention.

Claims

An underwater cover device, characterized by comprising a cover body and a gas source connected to the cover body. The cover body has an open end face directed towards an underwater surface, forming a rotating water flow inside the cover body. The gas source supplies air into the cover body, and the rotating water flow prevents the air from escaping through the gap between the open end face and the underwater surface, thereby forming a water-free space on the underwater surface.
The underwater cover device according to claim 1, characterized in that the gas source includes a gas flow regulating mechanism for controlling the flow rate of air supplied into the cover body, thereby controlling the volume of air inside the cover body.
The underwater cover device according to claim 1, characterized in that one or more nozzles are arranged inside the cover body, with the nozzles being tangential to the inner wall surface of the cover body. Water is injected into the cover body through the nozzles and flows along the inner wall surface, forming a rotating water flow inside the cover body.
The underwater cover device according to claim 3, characterized in that the gas source is connected to the cover body through the nozzles, and air is supplied into the cover body through the nozzles.
The underwater cover device according to claim 1, characterized in that the cover body is provided with air holes, and the gas source is connected to the air holes to supply air into the cover body through the air holes.
The underwater cover device according to claim 3, characterized in that an annular partition is arranged inside the cover body, separating the water-free space from the rotating water flow.
The underwater cover device according to claim 1, characterized in that blades are arranged inside the cover body, and a motor drives the blades to rotate, causing the water inside the cover body to rotate and form a rotating water flow. The rotating water flow prevents the air from escaping through the gap between the open end face and the underwater surface.
The underwater cover device according to claims 1-7, characterized in that the cover body is provided with drainage channels, and part of the water inside the cover body is discharged through the drainage channels.
The underwater cover device according to claim 1, characterized in that the device further comprises one or more air chambers connected to the air region inside the cover body. Water in the air chambers flows into the cover body while air enters the air chambers, forming a water-free space inside the air chambers.