Underwater vehicle head structure capable of slowly releasing drag reducer

Abstract

The invention discloses an underwater vehicle head structure capable of slowly releasing a drag reducer, and belongs to the field of underwater drag reduction of vehicles. Comprising a head cone section and a head circular truncated cone section which are coaxially and fixedly connected, one end of the head circular truncated cone section is in sealed connection with the head cone section, a cavity structure for containing a drag reducer solution is arranged at the joint, and the other end of the head circular truncated cone section is in sealed connection with a navigation body middle section; the head cone section is a rotary body porous medium which is close to a cone, the cone vertex of the head cone section is a molded line stagnation point which forms a conical molded surface, the axial height at the stagnation point is the largest, and the axial thickness is in a change rule of gradually decreasing from the stagnation point to the edge of the bottom end. The defects that in the prior art, a drag reducer solution cannot evenly wrap the whole vehicle, and the integrity of a shell of the vehicle is greatly damaged when the drag reducer is released are overcome.

Description

Technical Field

[0001] The invention belongs to the field of underwater drag reduction of aircraft, and in particular relates to an underwater aircraft head structure capable of slowly releasing a drag reducing agent. Background Art

[0002] As a highly efficient drag reducer, water-soluble polymers can interact with turbulence when dissolved in water, greatly reducing turbulent resistance. Existing studies have shown that adding a trace amount of polymers to turbulence can achieve a drag reduction effect of more than 70%. It has been widely used in firefighting, pipeline transportation, agricultural irrigation, biomedicine and other fields, but it has not yet been applied to underwater vehicles. The main reason is that internal flow scenarios such as pipeline transportation are convenient for adding polymers to form a uniform polymer solution, while the external flow scenario of underwater vehicles cannot form a uniform polymer solution. Therefore, if a device can be proposed to release polymer solutions directly into the external flow field, so that the underwater vehicle can be covered with a layer of drag reduction solution like a fish, the performance of the underwater vehicle will be greatly improved.

[0003] In order to achieve the above goals, relevant research has been carried out. For example, the disclosed annular adjustable injection device for a navigation body includes an injection head, a middle part of the navigation body, a tail part of the navigation body, and a hydraulic cylinder. The injection head is provided with a slit, and the width is adjustable, so that the polymer solution can be sprayed out along the slit. However, the slit of this design is located after the linear segment of the head, and the polymer solution cannot cover the head, so that its drag reduction effect cannot reach the best; in addition, the slit on the outer surface of the model causes the outer structure of the navigation body to be incomplete, and the non-injection state will greatly increase the resistance and easily cause damage to the model. The prior art also discloses a mucus drag reduction device for underwater vehicles. The device uses a gas cylinder to drive the piston cylinder to move, so that the drag-reducing mucus is released to the outer surface through release holes evenly distributed in the circumferential direction of the outer shell of the vehicle to achieve speed increase and range increase. However, due to the limited number of release holes opened on the hull of the underwater vehicle, if the aperture is too large, the stability of the outer surface of the vehicle will be destroyed. If the aperture is too small, the injection rate will be too high and it will not be able to adhere to the wall to achieve drag reduction. In addition, this method cannot achieve uniform distribution of the sprayed solution on the outer surface of the model.

[0004] Therefore, the application of polymer solutions to aircraft disclosed in the prior art does not achieve an improvement in the drag reduction effect of the aircraft. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides an underwater vehicle head structure capable of slowly releasing a drag reducer, which can achieve uniform release of a drag reducer solution by designing and defining the front end profile and material of the vehicle head, that is, combining a porous medium with a set profile line. The present invention solves the shortcomings of the prior art that the drag reducer solution cannot evenly coat the entire vehicle, and that the release of the drag reducer significantly damages the integrity of the vehicle shell.

[0007] The technical solution of the present invention is: an underwater vehicle head structure capable of slowly releasing a drag reducer: comprising a head cone section and a head truncated cone section coaxially fixedly connected, one end of the head truncated cone section is sealed and connected to the head cone section, and a cavity structure for accommodating a drag reducer solution is provided at the connection, and the other end is sealed and connected to the middle section of the navigation body;

[0008] The head cone section is a nearly conical rotating body porous medium, the cone vertex of which is the stagnation point of the profile forming the conical surface, the axial height at the stagnation point is the largest, and the axial thickness gradually decreases from the stagnation point to the bottom edge.

[0009] A further technical solution of the present invention is that the profile of the head cone section adopts the Granville profile, which is expressed as:

[0010]

[0011] Among them, a and b are unknown parameters, and the value range is a≤2, b≤18.

[0012] A further technical solution of the present invention is: the undetermined parameters are selected as a=2, b=10.

[0013] A further technical solution of the present invention is that the pores of the porous medium are 10 microns to 80 microns.

[0014] A further technical solution of the present invention is: a groove is provided on the mounting surface where the head frustum section and the head cone section are connected, which serves as a chamber for containing the drag reducer solution; the outer circumferential surface of the connecting end with the middle section of the vehicle is a stepped structure, and an external thread and a sealing ring groove are provided on the stepped circumferential surface, and the external thread is fixedly connected with the internal thread of the middle section of the vehicle, and a sealing connection between the two is achieved by a sealing ring installed in the sealing ring groove.

[0015] A further technical solution of the present invention is that an internal threaded through hole is provided at the bottom of the drag reducer solution containing cavity of the head frustum section for installing a starter quick connector, which is connected to a pipeline to introduce the drag reducer solution into the cavity.

[0016] A further technical solution of the present invention is: a plurality of through holes and sealing ring grooves are circumferentially opened on the upper mounting surface where the head conical section is connected to the head conical section; the plurality of through holes and the plurality of threaded holes circumferentially opened on the bottom surface of the head conical section are arranged in one-to-one correspondence; a corresponding number of bolts are respectively passed through the through holes of the head conical section and screwed into the threaded holes to complete the fixed connection between the two; a sealing connection between the two is achieved by installing a sealing ring in the sealing ring groove.

[0017] A further technical solution of the present invention is that the circumferential surfaces of the head frustum section and the head cone section are smoothly transitionally connected.

[0018] A further technical solution of the present invention is that the ratio of the axial length of the cone section of the head to the axial length of the frustum section of the head is less than 1:2.

[0019] A method for reducing drag of an underwater vehicle, the specific steps are as follows:

[0020] Determine that the material of the head cone section of the underwater vehicle head structure is a porous medium;

[0021] According to the porous medium flow resistance calculation equation, it is concluded that the flow resistance is positively correlated with the thickness and porosity of the porous medium, and further determined that the solution release rate is proportional to the resistance encountered during the solution release process;

[0022] Based on the above relationship, the profile of the head cone section is designed, and the expression is as follows:

[0023]

[0024] Among them, a and b are unknown parameters, and the range of values ​​is a≤2, b≤18;

[0025] A drag reducer solution receiving chamber is provided on the mounting surfaces of the head frustum section and the head cone section, and the drag reducer solution is introduced into the receiving chamber through a pneumatic quick connector and a pipeline;

[0026] The drag reducing agent solution penetrates into the outer surface of the aircraft head through the pores of the porous medium, and forms a uniform drag reducing film layer on the outer peripheral surface of the aircraft.

[0027] Beneficial Effects

[0028] The beneficial effects of the present invention are:

[0029] 1. The present invention proposes an underwater vehicle head structure capable of releasing a drag reducer in a water tunnel experiment, which is mainly composed of a porous medium section with a linear shape and a head truncated cone section matched therewith, and is connected as a whole through threads to form a complete head model with a certain volume cavity. The present invention adopts a round head linear shape, which can enable the vehicle model to maintain good hydrodynamic performance; in addition, the model adopts a porous medium to release a drag reducer solution, which ensures the integrity of the outer surface linear shape; the solution energy model has a simple structure, is easy to process and assemble, and can be mass-produced and applied.

[0030] 2. The present invention injects the drag reducer solution into the cavity through a hose, so that it can flow into the outer surface of the aircraft through the porous medium part, and flow along the head to the end of the aircraft under the action of the incoming flow, thereby covering the entire outer surface of the aircraft and producing a significant drag reduction effect. According to the Ergun equation, the flow resistance of the liquid in the porous medium increases with the increase of the porous thickness. The thickness of the porous medium section is the thickest at the stagnation point, and becomes thinner along the outer surface toward the tail end. Therefore, when the drag reducer solution is released along the porous surface, the flow resistance becomes smaller and smaller. Therefore, the drag reducer released at the stagnation point of the porous medium is the least, and the amount of drag reducer solution released will also increase. This structure minimizes the resistance of releasing the drag reducer and makes it easier to get close to the wall.

[0031] 3. The porous medium segment used in the present invention can be replaced, and the plane end can be processed into a non-planar structure to change the thickness of the porous medium segment, thereby changing the flow resistance during the release of the drag reducer solution, and achieving the effect of changing the release distribution of the drag reducer solution. The porous medium segment is located at the front of the aircraft model and will not occupy the internal volume of the aircraft model. Therefore, other equipment can still be arranged in the internal space of the aircraft without affecting each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 are the line coordinates of the head line segment in the embodiment of the present invention.

[0033] Figure 2 Schematic diagram of a water tunnel experiment model for an underwater vehicle in an embodiment of the present invention.

[0034] Figure 3 Schematic diagram of the head model of the underwater vehicle in an embodiment of the present invention.

[0035] Figure 4 for Figure 3 Sectional view along plane AA.

[0036] Figure 5 for Figure 3 Sectional view along plane BB.

[0037] Figure 6The figure is the relationship between the rate of sustained release of the porous medium solution and the corresponding pressure difference in the embodiment of the present invention, which is obtained by point experiment and the straight line is obtained by fitting according to the experimental results.

[0038] Figure 7 The figure is the relationship between the thickness of the porous medium and the pressure difference during the porous medium sustained release of the solution in the embodiment of the present invention. The point is obtained by experiment, and the straight line is obtained by fitting according to the experimental results.

[0039] Figure 8 The drag reduction test results obtained by conducting a water tunnel drag reduction test using the head structure of the present invention are shown.

[0040] Explanation of the reference numerals: 1. porous medium section (head cone section); 2. head frustum section; 3. cylindrical section of the aircraft model; 4. tail section of the aircraft model; 5. internal thread hole; 6. sealing ring groove; 7. sealing ring groove; 8. external thread; 9. through hole; 10. internal thread through hole; 11. When the thickness of the porous medium is 9 mm, the relationship between the rate of sustained-release solution and the pressure difference is, and the fitting linear equation is: y=14.93x-0.30; 12. When the thickness of the porous medium is 3 mm, the relationship between the rate of sustained-release solution and the pressure difference is, and the fitting linear equation is: y =7.63x-0.18; 13. When the sustained release rate is 8mL / s, the relationship between the thickness of the porous medium and its pressure difference, the fitting linear equation is: y=8.77x-39.94; 14. When the sustained release rate is 14mL / s, the relationship between the thickness of the porous medium and its pressure difference, the fitting linear equation is: y=15.09x-71.19; 15. When the sustained release rate is 20mL / s, the relationship between the thickness of the porous medium and its pressure difference, the fitting linear equation is: y=21.79x-101.69. DETAILED DESCRIPTION

[0041] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0043] Based on the problems in the prior art that the drag reducer solution cannot evenly coat the entire navigation body, and the release of the drag reducer causes great damage to the integrity of the vehicle shell, the present invention provides an underwater vehicle head structure that can slowly release the drag reducer, comprising a head cone section and a head frustum section that are coaxially fixedly connected, one end of the head frustum section is sealed and connected to the head cone section, and a cavity structure for accommodating the drag reducer solution is provided at the connection, and the other end is sealed and connected to the middle section of the navigation body; the head cone section is a nearly conical rotating body of porous medium, and the cone vertex is the stagnation point of the profile line constituting the conical surface, the axial height at the stagnation point is the largest, and the axial thickness shows a gradually decreasing change pattern from the stagnation point to the bottom edge.

[0044] Specifically, the head structure model is threadedly connected with the cylindrical section in the middle of the aircraft model to form a complete aircraft water tunnel test model. The head truncated cone section has two sealing ring grooves and is equipped with sealing rings for sealing between the parts.

[0045] Specifically, the truncated cone section of the model head is provided with a threaded hole for installing a pneumatic quick connector, and the pneumatic connector is connected to a hose. The drag reducer solution is injected into the cavity through the hose, and then flows into the outer surface of the aircraft through the porous medium part, and flows along the head to the end of the aircraft in the downstream direction under the action of the incoming flow, thereby covering the entire outer surface of the aircraft, producing a significant drag reduction effect. The scheme not only ensures that the head line of the aircraft model has excellent hydrodynamic performance, but also maintains the integrity of the aircraft model's appearance.

[0046] Specifically, the porous medium section is a body of revolution, one end of which is a linear end, the linear end adopts the Granville linear end, and the linear equation is:

[0047]

[0048] Among them, a and b are unknown parameters, and the specific reference range is a≤2, b≤18. Here, a=2, b=10 are selected. According to the linear equation, the coordinates of any point on the model head can be obtained, and the axial and radial thicknesses of the porous medium can be determined. The other end is a plane end, and the plane end has 8 internal threaded holes evenly opened along the circumferential direction for connecting the head truncated cone section. The pores of the porous medium are 10 microns to 80 microns. The thickness of the porous medium section is the thickest at the stagnation point, and the thickness gradually becomes thinner along the tail end of the model. Therefore, during the release of the drag reducer solution through the porous medium section, the thickness is the thickest at the stagnation point. As the linear shape develops, the porous medium becomes thinner and thinner. According to the Ergun equation for calculating the flow resistance of porous media:

[0049]

[0050] Where ΔP is the pressure drop; L is the length of the porous medium; μ is the dynamic viscosity of the fluid; U is the apparent flow velocity of the fluid, which is equal to the product of the porosity ∈ and the actual physical velocity V; d p is the diameter of the particle; ρ is the density of the fluid.

[0051] Based on the above formula, it can be concluded that under fixed working conditions, the flow resistance is positively correlated with the thickness and porosity of the porous medium. Therefore, the flow resistance is the largest at the head stagnation point, and the sprayed solution is the least. The thickness gradually becomes thinner along the tail end, the flow resistance gradually decreases, and the released solution gradually increases. This design method is conducive to the drag reducer solution coating the entire navigation body model, and the release resistance is smaller. In addition, according to theoretical and experimental results, the faster the solution is released, the greater the resistance encountered during the solution release process. Specifically, the relationship between the release rate and the pressure difference of the porous medium with a pore size of 30 microns and a thickness of 3mm and 9mm, respectively, is shown in the attached figure. Figure 6 As shown. With the increase of flow rate, the pressure difference gradually increases, that is, the flow resistance increases. At 3mm thickness and 9mm thickness, the quantitative relationship between the slow release rate and the pressure difference is ΔP = 7.63Q-0.18 and ΔP = 14.93Q-0.30 respectively. In addition, when the slow release rate remains unchanged, the flow resistance increases with the increase of the porous medium thickness. The specific relationship is shown in the attached Figure 7 . At a fixed release rate, such as 8mL / s, the relationship between the thickness of the porous medium and the corresponding flow pressure difference is ΔP=8.77H-39.94; at 14mL / s, the relationship between the thickness of the porous medium and the corresponding flow pressure difference is ΔP=15.09H-71.19; when the release rate is 20mL / s, the relationship between the thickness of the porous medium and its pressure difference is ΔP=21.79H-101.69. Therefore, at the above-mentioned release rate, the corresponding flow pressure difference of any porous thickness can be estimated based on the fitting relationship. According to the attached Figure 7 It can be concluded that when flowing freely, the porous medium has the largest flow resistance at the stagnation point due to its thickest thickness, so its flow rate is the smallest. The thinner the porous medium is, the smaller its flow resistance is, so the larger the flow rate is. Therefore, when releasing the drag reducer solution from the porous medium, the flow rate of the drag reducer solution released from the head becomes higher and higher from the stagnation point to the tail end. The advantage is that the flow rate is the smallest at the stagnation point, which can reduce the flow resistance; and in the process of developing toward the tail, the flow rate becomes larger and larger, which is conducive to the drag reducer solution being close to the wall surface and exerting the drag reduction effect.

[0052] Specifically, the head conical section is a body of revolution, and the circumferential outer surface is a straight section after passing through a linear section. One end is provided with 8 through holes evenly distributed along the circumference for installing bolts. The through hole is provided with a sealing ring groove near the center direction for installing the sealing ring. When the porous medium section and the head conical section are connected by bolts, the two will press the sealing ring to prevent the drag-reducing solution from leaking out of the joint. A threaded through hole is provided at the center position of this end for installing a pneumatic quick connector. The straight section of the other end face is provided with an external thread and is designed with a step surface for connection and positioning with the model cylindrical section. A circle of sealing ring grooves is provided in front of the thread near the stationary point for installing the sealing ring. When the head conical section and the model cylindrical section are connected by threads, the sealing ring groove is compressed to achieve a sealing effect.

[0053] Specifically, the porous medium section and the head truncated cone section together constitute the model head linear section, wherein the axial lengths of the porous medium section and the head truncated cone section are adjustable to meet different drag reducer solution release requirements. In addition, the linear shape of the porous medium section and the head truncated cone section are two parts of the same linear shape, and the axial length of the porous medium section: the length of the head truncated cone section is less than 1:2.

[0054] The present invention provides a method for reducing drag of an underwater vehicle, and the specific steps are as follows:

[0055] Step 1: Determine that the material of the head cone section of the underwater vehicle head structure is a porous medium;

[0056] Step 2: According to the porous medium flow resistance calculation equation, it is determined that the flow resistance is positively correlated with the thickness and porosity of the porous medium, and further it is determined that the solution release rate is proportional to the resistance encountered during the solution release process;

[0057] Step 3: Based on the above relationship, design the profile of the head cone segment. The expression is as follows:

[0058]

[0059] Among them, a and b are unknown parameters, and the range of values ​​is a≤2, b≤18;

[0060] Step 4: a drag reducer solution receiving chamber is provided on the mounting surfaces of the head frustum section and the head cone section, and the drag reducer solution is introduced into the receiving chamber through a pneumatic quick connector and a pipeline;

[0061] Step 5: The drag reducing agent solution penetrates into the outer surface of the aircraft head through the pores of the porous medium, forming a uniform drag reducing film layer on the outer peripheral surface of the aircraft.

[0062] The above technical solution is further described below in conjunction with the accompanying drawings:

[0063] Reference Figure 2As shown, this embodiment mainly includes a porous medium section 1 and a head truncated cone section 2, and O-rings are installed in the two sealing ring grooves of the head truncated cone section. The internal threaded hole 5 of the porous medium and the through hole 9 of the head truncated cone section are aligned and connected by 8 bolts. After the bolts are tightened, the O-ring is compressed to prevent water from seeping in the contacting part of the two. A pneumatic quick connector is installed in the internal threaded through hole 10 of the head truncated cone section, and the pneumatic quick connector is connected to the hose for conveying the drag reducer solution into the cavity.

[0064] Reference Figure 1 As shown, in this embodiment, the outer surface diameter of the cylindrical section 3 of the vehicle model is 60 mm, that is, the maximum outer surface diameter of the head of the model is 60 mm. The axial length of the porous medium section 1 is 10 mm, and the pores of the porous medium are 30 microns; the axial length of the head truncated cone section 2 is 40 mm, including a 30 mm linear section and a 10 mm straight section, that is, the axial length of the porous medium section 1: the axial length of the head truncated cone section 2 is 1:4. Therefore, the length of the head of the underwater vehicle model is 50 mm.

[0065] Reference Figure 3 As shown, eight internal thread holes 5 are evenly distributed in the circumferential direction of the plane end surface of the porous medium section 1, the internal thread size is M3, the depth is 3 mm, and the distance between the center of the internal thread hole and the axis of the model is 16.5 mm.

[0066] Reference Figure 4 As shown, the model head truncated cone section 2 also has 8 through holes 9 evenly distributed along the circumferential direction, with an inner diameter of 4.5 mm. The position of the through hole 9 corresponds to the internal threaded hole 5, that is, the distance from the axis of the model is 16.5 mm, and it cooperates with it. The through hole 9 is also radially inwardly provided with a sealing ring groove 6 for placing an O-ring. The minimum distance from the sealing ring groove 6 to the axis is 11.8 mm, the groove depth is 2.35 mm, and the groove width is 3.10 mm. The selection principle of the O-ring follows GB-T 3452.3-2005. The end face of the head truncated cone section 2 that cooperates with the porous medium section 1 is provided with a cylindrical groove with the axis as the center, a radius of 8 mm, and a depth of 6 mm, which is used to store the drag reducer solution.

[0067] The end faces of the model head frustum section 2 and the cylindrical section 3 are also provided with a cylindrical groove with the axis as the center. The radius of the groove is 24 mm and the depth is 24 mm. The interior of the groove is used for the internal layout of the aircraft model.

[0068] A metal wall with a wall thickness of 10 mm is formed between the two grooves of the head frustum section, and an internal threaded through hole 10 with the axis as the center and a model of M6 is opened in the center of the wall for installing a pneumatic quick connector.

[0069] The end of the model head truncated cone section 2 that matches the cylindrical section 3 is processed with an M55 external thread 8, which is 10 mm long and has a pitch of 1.5 mm, and is used to match the cylindrical section through a threaded connection. The external thread 8 is adjacent to a sealing ring groove 7 along the direction of the aircraft model head end, and the shortest distance between the two is 3 mm. The sealing ring groove bottom radius is 27.25 mm, the groove depth is 2.35 mm, the groove width is 3.10 mm, and the O-ring selection principle follows GB-T 3452.3-2005.

[0070] The specific working process of this embodiment is as follows:

[0071] First, assemble the head of the water tunnel test model and connect it with the cylindrical section and the tail section of the model. Then, pressurize the drag reducer solution and inject it into the cavity formed by the porous medium section and the head frustum section through a hose and a pneumatic quick connector. As the drag reducer solution is continuously injected, it will seep out through the porous medium section. Under the flushing action of the water tunnel flow, the drag reducer solution seeping out of the porous medium will adhere to the surface of the water tunnel model, and flow downstream from the head through the cylindrical section and finally from the tail section. As the drag reducer solution is continuously injected, it will coat the outer surface of the underwater vehicle model and interact with turbulence to achieve the effect of reducing resistance. Attached Figure 8 This is the experimental result obtained when the model in this embodiment releases the drag reducer solution at a flow rate of 14 mL / s in a water tunnel experiment, wherein the drag reduction rate first increases and then decreases with the water tunnel flow rate, and the maximum drag reduction rate can reach 34%.

[0072] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. An underwater vehicle head structure capable of slowly releasing a drag reducing agent, characterized in that: It comprises a head cone section and a head truncated cone section which are coaxially fixedly connected, one end of the head truncated cone section is sealed and connected to the head cone section, and a cavity structure for accommodating a drag reducer solution is provided at the connection, and the other end is sealed and connected to the middle section of the navigation body; The head cone section is a nearly conical rotating body porous medium, the cone vertex of which is the stagnation point of the profile forming the conical surface, the axial height at the stagnation point is the largest, and the axial thickness gradually decreases from the stagnation point to the bottom edge.

2. The underwater vehicle head structure capable of slowly releasing a drag reducing agent according to claim 1, characterized in that: The profile of the head cone section adopts the Granville profile, which is expressed as: Among them, a and b are unknown parameters, and the value range is a≤2, b≤18.

3. The underwater vehicle head structure capable of slowly releasing a drag reducing agent according to claim 2, characterized in that: The undetermined parameters are selected as a=2, b=10.

4. The underwater vehicle head structure capable of slowly releasing a drag reducing agent according to claim 2, characterized in that: The pores of the porous medium are 10 microns to 80 microns.

5. The underwater vehicle head structure capable of slowly releasing a drag reducing agent according to claim 1, characterized in that: A groove is provided on the mounting surface where the head frustum section and the head cone section are connected, which serves as a chamber for containing the drag reducer solution. The outer circumferential surface of the connecting end with the middle section of the vehicle is a stepped structure, and an external thread and a sealing ring groove are provided on the stepped circumferential surface. The external thread is fixedly connected with the internal thread of the middle section of the vehicle, and a sealing connection between the two is achieved by a sealing ring installed in the sealing ring groove.

6. The underwater vehicle head structure capable of slowly releasing a drag reducing agent according to claim 5, characterized in that: The bottom of the drag reducer solution containing cavity of the head frustum section is provided with an internal threaded through hole for installing a starting quick connector, which is connected with a pipeline to introduce the drag reducer solution into the cavity.

7. The underwater vehicle head structure capable of slowly releasing a drag reducing agent according to claim 6, characterized in that: A plurality of through holes and sealing ring grooves are circumferentially opened on the upper surface of the mounting surface where the head frustum section is connected to the head cone section. The plurality of through holes and the plurality of threaded holes circumferentially opened on the bottom surface of the head cone section are arranged in a one-to-one correspondence. A corresponding number of bolts are respectively passed through the through holes of the head frustum section and screwed into the threaded holes to complete the fixed connection between the two. A sealing connection between the two is achieved by installing a sealing ring in the sealing ring groove.

8. The underwater vehicle head structure capable of slowly releasing a drag reducing agent according to claim 7, characterized in that: The circumferential surfaces of the head frustum section and the head cone section are smoothly transitionally connected.

9. The underwater vehicle head structure capable of slowly releasing a drag reducing agent according to claim 8, characterized in that: The axial length of the head cone section: the axial length of the head frustum section is less than 1:

2.

10. A method for reducing drag of an underwater vehicle, implemented based on the underwater vehicle head structure according to any one of claims 1 to 9; characterized in that The specific steps are as follows: Determine that the material of the head cone section of the underwater vehicle head structure is a porous medium; According to the porous medium flow resistance calculation equation, it is concluded that the flow resistance is positively correlated with the thickness and porosity of the porous medium, and further determined that the solution release rate is proportional to the resistance encountered during the solution release process; Based on the above relationship, the profile of the head cone section is designed, and the expression is as follows: Among them, a and b are unknown parameters, and the range of values ​​is a≤2, b≤18; A drag reducer solution receiving chamber is provided on the mounting surfaces of the head frustum section and the head cone section, and the drag reducer solution is introduced into the receiving chamber through a pneumatic quick connector and a pipeline; The drag reducing agent solution penetrates into the outer surface of the aircraft head through the pores of the porous medium, and forms a uniform drag reducing film layer on the outer peripheral surface of the aircraft.

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