A numerical simulation method and system for AUV oblique navigation based on turbine machinery

Abstract

The invention discloses a method and system for numerical simulation of an AUV oblique navigation based on a turbine machinery, comprising: creating a rectangular parallelepiped fluid calculation domain for numerically simulating an AUV; setting a velocity inlet condition of the rectangular parallelepiped fluid calculation domain, the velocity inlet condition including a velocity magnitude and a velocity direction; setting a virtual calculation domain and a translational periodic interface boundary condition according to the velocity direction in the velocity inlet condition; simulating the oblique navigation state of the AUV according to the rectangular parallelepiped fluid calculation domain, the velocity inlet condition and the boundary condition.

Description

Technical Field

[0001] The present invention relates to the field of AUV simulation, and in particular to a method and system for slant navigation numerical simulation of an AUV based on turbine machinery. Background Art

[0002] At present, the method of using computational fluid dynamics (CFD) simulation and maneuverability prediction has been confirmed and applied. This maneuverability prediction method generally includes the following four steps: CFD fluid simulation, fitting to obtain hydrodynamic coefficients, constructing the six-degree-of-freedom hydrodynamic equation of the hull, and completing the maneuverability prediction through steering instructions. When performing CFD simulation, it is necessary to simulate the actual navigation test of the hull, which basically has the following types: straight-line test, oblique test (horizontal plane, vertical plane, three-dimensional space), rotation test using momentum source method (horizontal plane, vertical plane), PMM plane motion mechanism test. CFD simulation is mainly divided into the following five steps: geometric model modification and watershed construction, meshing, calculation pre-processing, simulation calculation, and simulation result post-processing.

[0003] The prior art includes the following defects:

[0004] The existing AUV oblique navigation simulation calculation domain requires the AUV hull geometry model to be rotated to the oblique navigation posture, that is, the oblique navigation drift angle (horizontal plane) or the angle of attack (vertical plane). The entire calculation domain is divided into a velocity inlet and a pressure outlet. The boundary of the calculation domain is a sliding wall, and the surface of the AUV hull is a non-slip wall. The type of simulation is a steady-state simulation, that is, the simulation result does not change with time; the water flow velocity is perpendicular to the velocity inlet surface, so as to achieve the purpose of the simulation oblique navigation test.

[0005] However, after the AUV hull geometry model is rotated (each time the AUV hull geometry model is rotated), the grid needs to be re-divided. Taking the calculation of at least 10 working conditions in the horizontal plane, vertical plane, and three-dimensional space as an example, the AUV hull geometry needs to be rotated more than 30 times and the grid needs to be divided more than 30 times. Each grid division will not only bring about grid sensitivity problems, but also increase huge workload, computer and time costs. Not only that, due to the rotation of the AUV hull geometry, the hull coordinate system also rotates with the geometry, which brings about the problem that the hull coordinate system and the geodetic coordinate system do not coincide. After the simulation is completed, the simulation results of the geodetic coordinate system must be converted to the hull coordinate system. This coordinate system conversion calculation is not only time-consuming and labor-intensive, but also prone to calculation errors.

[0006] Based on the current simulation settings, if you do not want to rotate the AUV hull geometry, it is impossible to achieve oblique navigation simulation by only changing the velocity direction at the fluid inlet. Since the fluid will be affected by the walls around the finite computational domain, the fluid angle only maintains the set value at the velocity inlet. As the water flow advances and spreads, the fluid angle will gradually change, thus becoming an uncontrollable factor. For example, the water flow velocity at the inlet is 4 knots, and the water flow direction is set to a vertical angle of attack of 6°. The actual streamlines are as follows: Figure 2 As shown in the figure, the direction of the water flow is only 6° at the inlet, and then gradually changes. This setting obviously does not meet the requirements of the oblique ship test. It can be seen that how to break the boundary restrictions of the calculation domain and ensure that a uniform oblique ship speed direction can be achieved in the entire fluid calculation domain is a key issue that needs to be solved. Summary of the invention

[0007] To achieve the above-mentioned purpose and other related purposes, the present invention discloses a numerical simulation method of AUV oblique navigation based on turbine machinery, comprising:

[0008] Create a cuboid fluid computational domain for numerical simulation of AUV;

[0009] Set the velocity inlet conditions of the rectangular fluid calculation domain. The velocity inlet conditions include velocity magnitude and velocity direction.

[0010] According to the velocity direction in the velocity inlet condition, set the translational periodic boundary condition;

[0011] According to the rectangular fluid calculation domain, velocity inlet conditions and boundary conditions, the oblique navigation state of the AUV is simulated.

[0012] Furthermore, according to the velocity direction in the velocity inlet condition, the translational periodic interface boundary condition is set to include:

[0013] If the velocity direction is only in the direction of the horizontal plane, the AUV surface is set as a non-slip wall, and an identical virtual calculation domain is assumed on both sides of the port and starboard sides of the rectangular fluid calculation domain. The walls on the port and starboard sides of the AUV in the rectangular fluid calculation domain are set as translational periodic interfaces, and the walls on the upper and lower sides of the AUV in the rectangular fluid calculation domain are set as slip walls or symmetric surfaces.

[0014] Furthermore, according to the velocity direction in the velocity inlet condition, the translational periodic interface boundary condition is set to include:

[0015] If the velocity direction is only in the direction of the vertical plane, the AUV surface is set as a non-slip wall, and the walls on the left and right sides of the AUV in the rectangular fluid calculation domain are set as sliding walls or symmetric surfaces. An identical virtual calculation domain is assumed on the upper and lower sides of the rectangular fluid calculation domain, and the walls on the upper and lower sides of the AUV in the rectangular fluid calculation domain are set as translational periodic interfaces.

[0016] Furthermore, according to the velocity direction in the velocity inlet condition, the translational periodic interface boundary condition is set to include:

[0017] If the velocity direction has components in both the horizontal and vertical directions, the AUV surface is set as a non-slip wall, and an identical virtual computational domain is assumed in each of the four directions of the upper, lower, left, and right of the rectangular flow domain. The walls on the left and right sides of the AUV in the rectangular fluid computational domain are set as the first group of translational periodic interfaces, and the walls on the upper and lower sides of the AUV in the rectangular fluid computational domain are set as the second group of translational periodic interfaces.

[0018] Furthermore, the K-epsilon turbulence model and wall function were used for simulation.

[0019] On the other hand, the present invention also provides a numerical simulation system for AUV oblique navigation based on turbine machinery, comprising:

[0020] A computational domain creation module is used to create a rectangular fluid computational domain for numerical simulation of the AUV;

[0021] The velocity inlet condition setting module is used to set the velocity inlet conditions of the rectangular fluid calculation domain. The velocity inlet conditions include velocity magnitude and velocity direction.

[0022] The boundary condition setting module is used to set the translational periodic boundary condition according to the velocity direction in the velocity inlet condition;

[0023] The simulation module simulates the oblique navigation state of the AUV according to the rectangular fluid calculation domain, velocity inlet conditions and boundary conditions.

[0024] By adopting the above technical solution, the boundary restrictions of the calculation domain are broken, ensuring that a uniform oblique navigation speed direction can be achieved in the entire fluid calculation domain, and the oblique navigation simulation can be completed without rotating the AUV hull geometry and only changing the speed direction of the fluid inlet. It saves multiple rotations of CAD geometry during the oblique navigation CFD simulation process, saves multiple repetitive meshing work during the oblique navigation CFD simulation process, and can complete the simulation without coordinate system conversion calculation, greatly improving the simulation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. The accompanying drawings are used to better understand the present solution and do not constitute a limitation of the present disclosure. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements, among which:

[0026] Figure 1 is a flow chart of the present invention;

[0027] Figure 2 It is a simulation streamline diagram when the water flow velocity at the inlet is 4 knots and the water flow direction is set to a vertical plane attack angle of 6° in the prior art;

[0028] Figure 3 The left and right virtual computing domains assumed by the present invention;

[0029] Figure 4 The velocity direction and water flow stroke of the virtual calculation domain of the present invention;

[0030] Figure 5 It is the virtual calculation domain arrangement of the horizontal plane oblique flight and the vertical plane oblique flight of the present invention;

[0031] Figure 6 It is a virtual calculation domain arrangement of the three-dimensional oblique navigation of the present invention;

[0032] Figure 7 The simulation results of vertical oblique navigation with a speed of 4 knots and an angle of attack of 6° during the actual application of the solution of the present invention;

[0033] Figure 8 It is a simulated velocity streamline diagram with an attack angle of 2° during the actual application of the solution of the present invention;

[0034] Fig. 9 This is a space oblique speed streamline diagram with an attack angle of 10° and a drift angle of 10° during the actual application of the solution of the present invention;

[0035] Fig.10 This is the spatial oblique velocity vector diagram of an attack angle of 10° and a drift angle of 10° during the actual application of the solution of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0037] Reference Figure 1 The embodiment of the present invention provides a numerical simulation method for AUV oblique navigation based on turbine machinery, comprising the following steps:

[0038] S1: Create a rectangular fluid computational domain for numerical simulation of the AUV.

[0039] Specifically, the inlet, outlet, and wall are set. The center of gravity of the AUV is at the origin of the absolute coordinate system, and the Cartesian coordinate system of the hull coincides with the absolute coordinate system.

[0040] S2: Set the velocity inlet conditions of the rectangular fluid calculation domain. The velocity inlet conditions include velocity magnitude and velocity direction.

[0041] In this embodiment, the fluid mechanics simulation software Fluent is used for simulation. When setting the velocity inlet conditions, the velocity magnitude and direction vector can be directly set, or the velocity component in the XYZ direction of the coordinate system can be input.

[0042] S3: Set boundary conditions according to the velocity direction in the velocity inlet condition.

[0043] Specifically, they include:

[0044] If the velocity direction is only in the direction of the horizontal plane, the AUV surface is set as a non-slip wall, and an identical virtual calculation domain is assumed on both sides of the port and starboard sides of the rectangular fluid calculation domain. The walls on the port and starboard sides of the AUV in the rectangular fluid calculation domain are set as translational periodic interfaces, and the walls on the upper and lower sides of the AUV in the rectangular fluid calculation domain are set as slip walls or symmetric surfaces.

[0045] If the velocity direction is only in the direction of the vertical plane, the AUV surface is set as a non-slip wall, and the walls on the left and right sides of the AUV in the rectangular fluid calculation domain are set as sliding walls or symmetric surfaces. An identical virtual calculation domain is assumed on the upper and lower sides of the rectangular fluid calculation domain, and the walls on the upper and lower sides of the AUV in the rectangular fluid calculation domain are set as translational periodic interfaces.

[0046] If the velocity direction has components in both the horizontal and vertical directions, the AUV surface is set as a non-slip wall, and an identical virtual computational domain is assumed in each of the four directions of the upper, lower, left, and right of the rectangular flow domain. The walls on the left and right sides of the AUV in the rectangular fluid computational domain are set as the first group of translational periodic interfaces, and the walls on the upper and lower sides of the AUV in the rectangular fluid computational domain are set as the second group of translational periodic interfaces.

[0047] As mentioned above, based on the current simulation settings, if you do not want to rotate the AUV hull geometry, it is impossible to achieve oblique navigation simulation by only changing the fluid angle of the inlet velocity. Since the fluid will be affected by the walls around the finite computational domain, the fluid angle only maintains the set value at the velocity inlet. As the water flow advances and spreads, the fluid angle will gradually change, thus becoming an uncontrollable factor. For example, the water flow velocity at the inlet is 4 knots, and the water flow direction is set to a vertical plane angle of attack of 6°. The direction of the water flow is only 6° at the inlet, and then gradually changes. Such a setting obviously does not meet the requirements of the oblique navigation test.

[0048] This method refers to the idea of ​​setting boundary conditions for a single-channel rotating computational domain of a turbine. A turbine is a rotating machine, and the runner has 24 blades and 24 guide vanes on the outer ring. One runner blade and one guide vane form a group, and the entire turbine can be divided into 24 channels. Since the geometry and movement of each blade of the runner are exactly the same, and they all rotate around the axis, in order to save calculation time and cost, one channel is usually calculated. Each channel is connected to the channels on the front and rear sides, so the movement of this channel is considered to be repetitive and periodic. On both sides of this channel, periodic boundaries are set to connect the next blade. And because the movement of the turbine is a rigid body rotating around the axis, it is set as a rotating periodic interface. With this setting, it can be achieved that in a single channel, the water flow maintains a uniform velocity direction from the inlet of the computational domain to the leading edge of the guide vane, which conforms to the real physical situation.

[0049] AUV is completely different from turbine machinery. First, the navigation of AUV in water is a rigid body linear motion, which does not involve rotational motion at all. Secondly, as an independent moving rigid body, the calculation domain of AUV is a single and independent calculation domain, and there is no periodicity. Therefore, the rotational periodic boundary conditions of turbine machinery cannot be directly applied to the simulation calculation of AUV.

[0050] Since there is no periodicity, but you want to use periodic boundary conditions, you need to assume a virtual periodic computational domain. And since there is no rotational motion involved, you can only assume a translational virtual computational domain. Figure 3 As shown in the figure, the middle is the real computational domain. The left and right sides of the AUV are each assumed to have a computational domain that is exactly the same as the real computational domain and is connected to the real computational domain. Since the virtual computational domain on the left, the real computational domain, and the virtual computational domain on the right are exactly the same, they can form a repeated periodic relationship. According to this idea, the left and right sides of the real computational domain can be set as periodic boundaries. Figure 4As shown in the figure, the water flow velocity entering from the velocity inlet of the virtual computational domain on the right first passes through the virtual computational domain, crosses the periodic boundary on the right, enters the real computational domain, then passes through the real computational domain, exits from the periodic boundary on the left, and enters the virtual computational domain on the left; the water flow velocity entering from the velocity inlet of the real computational domain first passes through the real computational domain, crosses the periodic boundary on the left, and then enters the virtual computational domain on the left.

[0051] In summary, through the assumption of the virtual computational domain, the interface between the virtual computational domain and the real computational domain can be set as a periodic boundary, so that the water flow velocity starts from the entrance of the virtual computational domain and the real computational domain, passes through the periodic boundaries on both sides, breaks the boundary restriction of the computational domain, and realizes that the direction of the water flow velocity remains uniform in the real computational domain.

[0052] Reference Figure 5 In the oblique navigation simulation of the AUV horizontal plane (XOY plane), the water flow velocity has velocity components in the X and Y axes. It is necessary to assume virtual calculation domains on the port and starboard sides, and set the watershed boundaries on the port and starboard sides as translational periodic interfaces. In the oblique navigation simulation of the AUV vertical plane (XOZ plane), the water flow velocity has velocity components in the X and Z axes. It is necessary to assume virtual calculation domains on the upper and lower sides, and set the watershed boundaries on the upper and lower sides as translational periodic interfaces.

[0053] Reference Figure 6 When the AUV has velocity components on the three axes of X, Y, and Z during navigation, the basic idea is to decompose the three-dimensional velocity into the velocity component of the horizontal plane (XOY) and the velocity component of the vertical plane (XOZ), and it is necessary to assume virtual computational domains in the Y and Z directions. For the water flow velocity with components in the X, Y, and Z directions at the same time, the velocity of the XOY horizontal plane will pass through the virtual computational domains on the port and starboard sides, and the velocity of the XOZ vertical plane will pass through the virtual computational domains on the upper and lower sides, so that the velocity direction is consistent on the two planes. Since the three-dimensional velocity is decomposed into the velocity on two two-dimensional planes, two sets of periodic boundaries need to be set. One set is the horizontal plane, the real computational domain forms a periodicity with the virtual computational domains on the port and starboard sides, and the boundaries on the port and starboard sides are translational periodic boundaries. The other set is the vertical plane, the real computational domain forms a periodicity with the virtual computational domains on the upper and lower sides, and the boundaries on the upper and lower sides are translational periodic boundaries.

[0054] This method saves the repeated geometric rotation and meshing work during the CFD simulation of oblique flight. By calculating 10 conditions for horizontal, vertical and spatial oblique flight, it can save about 30 times of manual work and computer core time for geometric rotation and meshing. It also eliminates the risk of reduced calculation accuracy and uncertainty caused by mesh changes. The coordinate transformation calculation in post-processing is directly omitted.

[0055] S4: According to the rectangular fluid calculation domain, velocity inlet conditions and boundary conditions, the oblique navigation state of the AUV is simulated.

[0056] As mentioned above, the simulation calculation is in the form of steady-state calculation, which can meet industrial requirements and save calculation time. In view of the need to obtain results quickly in the industrial field, the turbulence model does not have high requirements for Y+, so the K-epsilon turbulence model and wall function are used for simulation. The simulation fully converged within 800 time steps, and 5.3 core hours were consumed for every 10 million grids. Among them, the simulation results of vertical oblique course with a speed of 4 knots and an angle of attack of 6° are as follows Figure 7 As shown, the simulated velocity streamline diagram with an attack angle of 2° is as follows Figure 8 As shown, the velocity streamline diagram of the AUV in space oblique flight, with an attack angle of 10° and a drift angle of 10° is as follows Fig. 9 As shown in the figure, the velocity vector diagram is Fig.10 As shown, it can be seen that this method can achieve the uniformity of velocity direction in the space oblique navigation flow domain, thereby enabling the simulation to simulate the real space oblique navigation effect.

[0057] The embodiment of the present invention further provides a numerical simulation system for AUV oblique navigation based on turbine machinery, comprising:

[0058] A computational domain creation module is used to create a rectangular fluid computational domain for numerical simulation of the AUV;

[0059] The velocity inlet condition setting module is used to set the velocity inlet conditions of the rectangular fluid calculation domain. The velocity inlet conditions include velocity magnitude and velocity direction.

[0060] A boundary condition setting module is used to set the translational periodic interface boundary condition according to the velocity direction in the velocity inlet condition;

[0061] The simulation module simulates the oblique navigation state of the AUV according to the rectangular fluid calculation domain, velocity inlet conditions and boundary conditions.

[0062] Those skilled in the art will appreciate that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined.

[0063] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the embodiments of the present invention are not limited by the order of the actions described, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present invention.

[0064] It can be known from the description of the above implementation modes that those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application can be essentially or partly contributed to the prior art in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes several instructions for enabling a computer device (which can be a personal computer, a server or a network device, etc.) to execute the methods described in the various implementation modes of the present application or certain parts of the implementation modes.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A numerical simulation method for AUV oblique navigation based on turbine machinery, characterized in that: include: Create a cuboid fluid computational domain for numerical simulation of AUV; Set the velocity inlet conditions of the rectangular fluid calculation domain. The velocity inlet conditions include velocity magnitude and velocity direction. According to the velocity direction in the velocity inlet condition, set the translational periodic interface boundary condition, including: Decompose the velocity direction; If the velocity direction has a component in the horizontal plane, the left and right sides of the rectangular fluid calculation domain are set to translational periodic interface boundary conditions; If the velocity direction has a component in the vertical direction, the upper and lower sides of the rectangular fluid calculation domain are set as translational periodic interface boundary conditions, including: If the velocity direction is only in the horizontal direction, the AUV surface is set as a non-slip wall, and an identical virtual calculation domain is assumed on both the port and starboard sides of the rectangular parallelepiped fluid calculation domain. The walls on the port and starboard sides of the AUV in the rectangular parallelepiped fluid calculation domain are set as translational periodic interfaces, and the walls on the upper and lower sides of the AUV in the rectangular parallelepiped fluid calculation domain are set as sliding walls or symmetric surfaces. According to the rectangular fluid calculation domain, velocity inlet conditions and boundary conditions, the oblique navigation state of the AUV is simulated.

2. The method according to claim 1, characterized in that According to the velocity direction in the velocity inlet condition, the translational periodic interface boundary conditions are set as follows: If the velocity direction is only in the direction of the vertical plane, the AUV surface is set as a non-slip wall, and the walls on the left and right sides of the AUV in the rectangular fluid calculation domain are set as sliding walls or symmetric surfaces. An identical virtual calculation domain is assumed on the upper and lower sides of the rectangular fluid calculation domain, and the walls on the upper and lower sides of the AUV in the rectangular fluid calculation domain are set as translational periodic interfaces.

3. The method according to claim 1, characterized in that According to the velocity direction in the velocity inlet condition, the translational periodic interface boundary conditions are set as follows: If the velocity direction has components in both the horizontal and vertical directions, the AUV surface is set as a non-slip wall, and an identical virtual computational domain is assumed in each of the four directions of the upper, lower, left, and right of the rectangular flow domain. The walls on the left and right sides of the AUV in the rectangular fluid computational domain are set as the first group of translational periodic interfaces, and the walls on the upper and lower sides of the AUV in the rectangular fluid computational domain are set as the second group of translational periodic interfaces.

4. The method according to claim 1, characterized in that: The K-epsilon turbulence model and wall function are used for simulation.

5. A numerical simulation system for AUV oblique navigation based on turbine machinery, characterized in that: include: A computational domain creation module is used to create a rectangular fluid computational domain for numerical simulation of the AUV; The velocity inlet condition setting module is used to set the velocity inlet conditions of the rectangular fluid calculation domain. The velocity inlet conditions include velocity magnitude and velocity direction. The boundary condition setting module is used to set the translational periodic interface boundary conditions according to the velocity direction in the velocity inlet conditions, including: Decompose the velocity direction; If the velocity direction has a component in the horizontal plane, the left and right sides of the rectangular fluid calculation domain are set to translational periodic interface boundary conditions; If the velocity direction has a component in the vertical direction, the upper and lower sides of the rectangular fluid calculation domain are set as translational periodic interface boundary conditions, including: If the velocity direction is only in the horizontal direction, the AUV surface is set as a non-slip wall, and an identical virtual calculation domain is assumed on both the port and starboard sides of the rectangular parallelepiped fluid calculation domain. The walls on the port and starboard sides of the AUV in the rectangular parallelepiped fluid calculation domain are set as translational periodic interfaces, and the walls on the upper and lower sides of the AUV in the rectangular parallelepiped fluid calculation domain are set as sliding walls or symmetric surfaces. The simulation module simulates the oblique navigation state of the AUV according to the rectangular fluid calculation domain, velocity inlet conditions and boundary conditions.

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