Underwater vehicle depth profile motion trail simulation in complex internal wave ocean dynamic environment

Abstract

The ocean environment is assumed to be fluid with infinite depth and breadth, the influence of a flow field boundary is not considered, the underwater vehicle is symmetrical in shape and uniform in density distribution, and the gravity center is in the center of the underwater vehicle. A two-dimensional ocean density spring layer profile is constructed by utilizing ocean internal wave data (longitude resolution and latitude resolution are both greater than 1 / 200 degrees, depth resolution is less than 10m, and time resolution is 0.2 h) with high temporal-spatial resolution, and the data such as dynamic viscosity of ocean environment fluid, shape and length of an underwater vehicle and the like are combined to determine the ocean density spring layer profile. Hydrostatic force (gravity and buoyancy) and hydrodynamic force (inertial hydrodynamic force and viscous hydrodynamic force) borne by the underwater vehicle are calculated, and the vertical plane motion trail of the underwater vehicle from the position where the underwater vehicle makes contact with the sea surface to the position where the underwater vehicle is affected by the internal wave density spring layer is simulated.

Description

Technical Field

[0001] The present invention constructs a two-dimensional ocean density thermocline profile based on internal wave data in the ocean environment, and simulates the vertical motion trajectory of an underwater vehicle affected by the internal wave density thermocline inside the ocean in combination with the motion law of the underwater vehicle in the fluid. Background Art

[0002] In physical oceanography, sea surface waves are wave phenomena formed on the surface of the ocean or other fluids, and waves are the main wave types of sea surface waves. In the ocean, the density of the fluid varies with factors such as depth, temperature, and salinity, thus forming a density thermocline structure. In this region, the density of the fluid shows an obvious discontinuity in the vertical direction, forming a relatively steep density gradient layer, causing a jump in the fluid density value. Internal waves in the ocean are wave phenomena generated at the interface between two fluids with different densities, and often occur in the deep layer of the water body. The amplitude of the internal wave fluctuations is generally much larger than that of the surface waves, and these fluctuations do not affect the sea surface, making it difficult to observe the propagation of internal waves.

[0003] As a typical type of internal wave in the ocean, internal solitary waves will not only cause large-amplitude vertical fluctuations inside the ocean, but also generate sudden strong currents during their propagation, so that the motion attitude of the underwater vehicle may mutate or get out of control, and even throw the underwater vehicle out of the sea surface, resulting in its sudden upward floating and exposure of the target. On April 10, 1963, the US nuclear submarine "Thresher" suddenly sank in the Atlantic Ocean off the port of Boston. The reason for the sinking was that the submarine was dragged to the seabed by a strong internal wave. Therefore, the research on the influence of ocean internal waves on underwater vehicles over time and space has received more and more attention. The research on the influence of complex ocean phenomena on the motion of underwater vehicles is of great significance for the underwater vehicle to take emergency measures when encountering internal wave attacks. Summary of the Invention

[0004] The present invention assumes that the ocean environment is a fluid with infinite depth and breadth, does not consider the influence of the flow field boundary, and the shape of the underwater vehicle is symmetric, the density distribution is uniform, and the center of gravity is at the center position of the underwater vehicle. Using complex ocean internal wave data, based on data such as the shape, mass, and speed of the underwater vehicle, the hydrostatic force and hydrodynamic force received by the underwater vehicle are calculated, and a force analysis is performed on the underwater vehicle. The invention combines high spatio-temporal resolution data such as the density, flow velocity, and dynamic viscosity of the ocean environment fluid to construct a real-time two-dimensional ocean density thermocline profile, and simulates the vertical motion trajectory of a suspended underwater vehicle affected by the internal wave density thermocline.

[0005] To achieve the above object, the present invention adopts the following technical solution steps:

[0006] (1) Analyze the hydrostatic force and hydrodynamic force received by the underwater vehicle during its motion in the fluid

[0007] (2) Analyze the forces acting on a submarine in a suspended state when encountering internal ocean waves

[0008] (3) Simulate the vertical motion trajectory of an underwater vehicle affected by the internal wave density interface

[0009] The beneficial effects of the present invention are as follows:

[0010] Using high spatio-temporal resolution internal ocean wave data (longitude resolution and latitude resolution are both greater than 1 / 200°, depth resolution is less than 10 m, and time resolution is 0.2 h), a two-dimensional ocean density interface profile is constructed to simulate the vertical motion trajectory of an underwater vehicle from contacting the sea surface to being affected by the internal wave density interface. After the underwater vehicle encounters internal ocean waves, the motion law of the underwater vehicle is depicted in real time. On the one hand, the possible action paths and positions of the underwater vehicle are predicted, providing auxiliary decision-making for the operation of the underwater vehicle when encountering complex internal ocean waves. On the other hand, according to the motion law of the underwater vehicle, the shape of the underwater vehicle is optimized, and the cost and risk of the actual operation of the underwater vehicle are reduced, laying a certain foundation for the research on the influence of internal ocean waves on the motion of the underwater vehicle. Description of the Drawings

[0011] Figure 1 Flow chart of the force analysis of an underwater vehicle in a suspended state when encountering internal ocean waves

[0012] Figure 2 Schematic diagram of the composition and calculation method of each sub-step Detailed Embodiment

[0013] The present invention assumes that the ocean environment is an infinite-depth and infinite-breadth fluid, does not consider the influence of the flow field boundary, and the underwater vehicle has a symmetric shape, uniform density distribution, and the center of gravity is at the center of the underwater vehicle. Based on high spatio-temporal resolution internal ocean wave data and the motion attributes of the underwater vehicle, the forces acting on the underwater vehicle during the process of diving to a suspended state and encountering internal ocean waves are analyzed, and the vertical motion trajectory of the underwater vehicle affected by the internal wave density interface is simulated, including the following specific steps:

[0014] (1) Analyze the hydrostatic force and hydrodynamic force acting on the underwater vehicle when moving in the fluid

[0015] An underwater vehicle stationary on the water surface or underwater generally includes two hydrostatic forces. The first force is the gravity caused by the hull, rudder, and propeller, which is the gravity of the underwater vehicle. The gravity of the underwater vehicle acts vertically downward and acts on the center of gravity of the underwater vehicle. The second force is the hydrostatic force acting on the wetted surface area of the underwater vehicle. The hydrostatic force can be decomposed into two component forces in the vertical and horizontal directions. Since the underwater vehicle has a symmetric shape, the component forces in the horizontal direction cancel each other out, and the force in the vertical direction is the buoyancy force received by the underwater vehicle.

[0016] During the diving motion of the submersible, the submersible is affected by hydrodynamic forces. This is because when the submersible maintains a motion state in the fluid, the surrounding fluid is disturbed, resulting in an increase in the kinetic energy of the fluid. The fluid generates a reaction force on the submersible. To simplify the research, the hydrodynamic forces acting on the submersible in the actual fluid are considered in two aspects: inertial hydrodynamic forces and viscous hydrodynamic forces, and their mutual influence is ignored.

[0017] (2) Analyze the forces acting on the submarine in a suspended state when encountering internal ocean waves

[0018] Analyze the forces acting on the submersible in a suspended state. The submersible is subject to the gravitational force attracted by the Earth and the buoyant force exerted by the fluid. Since the submersible moves near the Earth's surface, the expression of its gravitational force is represented by the following formula:

[0019] F 重 = m * g

[0020] In the formula, m represents the mass of the submersible, g represents the acceleration due to gravity, and g = 9.8 m / s 2 .

[0021] According to Archimedes' principle, when an object is immersed in a liquid, the buoyant force it receives is equal to the weight of the liquid it displaces, and its magnitude is proportional to the volume of the liquid displaced by the object in the liquid. The expression of the buoyant force is represented by the following formula:

[0022] F 浮 = ρ 液 * V 排 * g

[0023] In the formula, ρ 液 represents the density of the fluid, V 排 represents the volume of the fluid displaced by the submersible, g represents the acceleration due to gravity, and g = 9.8 m / s 2 . When the submersible is completely immersed in the liquid, V 排 = V 艇 , V 排 reaches the maximum value.

[0024] When the submersible moves non-uniformly in the fluid, the kinetic energy of the fluid around the submersible increases, changing the velocity of the surrounding fluid. Because the fluid has inertia, the fluid generates a reaction force on the submersible, also known as the additional inertial force, which is commonly represented by "fluid inertial force". The magnitude of the fluid inertial force is proportional to the acceleration of the submersible, and the direction is opposite to the direction of the submersible's acceleration. The inertial force for the six-degree-of-freedom motion of the submersible in space can be expressed as

[0025]

[0026] In the formula, λ ijDenotes the added mass, which is the proportionality constant between the added inertial force and the acceleration. F j (j = 1, 2, 3, 4, 5, 6) denotes the inertial forces in six degrees of freedom. Denote the (angular) accelerations of the submersible in six degrees of freedom respectively.

[0027] When the submersible has relative motion with the surrounding fluid, due to the certain viscosity of the fluid, the surrounding fluid will generate viscous hydrodynamic forces on the submersible, and its viscous hydrodynamic forces mainly include frictional resistance and viscous pressure resistance. In engineering practice, the frictional resistance of the submersible is generally approximated by the flat plate frictional resistance. The present invention uses the Prandtl formula to calculate the frictional resistance F 摩擦阻力 , and the Prandtl formula is expressed by the following formula:

[0028]

[0029]

[0030]

[0031] In the formula, C f , ρ 液 , R e , μ 液 Denote the frictional resistance coefficient, density, Reynolds number, and dynamic viscosity of the ocean fluid respectively, S 潜航器 , L 潜航器 Denote the wetted surface area and length of the submersible respectively, v 相对 , ν 液 Denote the relative velocity between the submersible and the ocean fluid and the velocity of the ocean fluid respectively. The viscous pressure resistance F 黏压压阻 The calculation formula is as follows:

[0032]

[0033] In the formula, C d Denote the viscous pressure resistance coefficient of the ocean fluid respectively, A 潜航器 Denotes the maximum cross-sectional area of the submersible perpendicular to the fluid velocity.

[0034] After the submersible encounters the density jump layer in the suspended state, it continuously receives the hydrodynamic forces of internal ocean waves. Usually, the velocity directions of the upper and lower layers of fluid at the internal wave density jump layer are opposite, and the fluid with a certain velocity exerts inertial hydrodynamic forces and viscous hydrodynamic forces on the submersible. Based on the high spatio-temporal resolution ocean internal wave data, the submersible is affected by the hydrodynamic forces of the upper and lower layers of fluid at the internal wave density jump layer, and its acting force is used as the torque of the submersible, resulting in the submersible generating a pitching motion in the vertical plane. The calculation formula of the torque T is as follows:

[0035] T = F * r

[0036] In the formula, F represents the force applied to the object, and r represents the lever arm, that is, the distance from the point of application of the force to the axis of rotation. For the force analysis of the submersible, in the horizontal direction, there is a horizontal component of the hydrodynamic force on the submersible, and in the vertical direction, the submersible is subject to the resultant force of buoyancy, gravity, and the vertical component of the hydrodynamic force.

[0037] (3) Simulate the vertical plane motion trajectory of the submersible affected by the internal wave density jump layer

[0038] Use high spatio-temporal resolution ocean internal wave data to construct a two-dimensional ocean density jump layer profile. Step (2) gives the force analysis of the submersible in the vertical plane affected by the internal wave density jump layer. The upper and lower layers of fluid in the ocean internal wave density jump layer propagate at a certain speed, and the hydrodynamic force acting on the submersible changes in real time with the ocean internal wave data and the motion parameters of the submersible. The linear equation of the submersible's motion in the vertical plane is

[0039]

[0040] In the formula, respectively represent the hydrodynamic force components on the submersible in the horizontal direction, respectively represent the hydrodynamic force components on the submersible in the vertical direction, respectively represent the hydrodynamic force components on the submersible in the pitching direction, respectively represent the horizontal, vertical, and pitching angular accelerations of the submersible, u and q respectively represent the horizontal and pitching angular velocities of the submersible, and I y represents the moment of inertia of the submersible in the pitching direction.

[0041] According to the motion direction of the submersible and the propagation direction of the ocean internal wave, there are various situations, and the influence of the internal wave on the submersible is different in different situations. Based on the high spatio-temporal resolution ocean internal wave data, the present invention uses the method of calculus to divide the time when the submersible is affected by the internal wave density jump layer into countless small segments. The initial moment is T, and through the loop body, the linear equation of the submersible's motion in the vertical plane is obtained, and the motion trajectory of the submersible is simulated. Then, it is judged whether the submersible has escaped from the ocean internal wave. If the submersible has not escaped from the ocean internal wave, then T = T + ΔT, simulate the next moment T + ΔT, and combine the trajectory of the previous moment to fit the motion law of the submersible for the total duration; if the submersible has escaped from the ocean internal wave, directly output the vertical plane motion trajectory of the submersible affected by the ocean internal wave.

Claims

1. Simulation of the depth profile movement trajectory of a submersible in a complex internal wave ocean dynamic environment, with the following main features: (1) Based on high spatio-temporal resolution ocean internal wave data and submersible attribute data, conduct a force analysis on the submersible: Based on high spatio-temporal resolution ocean internal wave data (longitude resolution, latitude resolution are both greater than 1 / 200°, depth resolution is less than 10 m, time resolution is 0.2 h), according to the general diving depth of the submersible, the submersible is affected by multiple force points of high spatio-temporal resolution ocean internal waves, and its movement trajectory is relatively complex. This patent first proposes that the hydrodynamic forces of ocean internal waves acting on a submersible in the ocean internal waves are mainly divided into hydrostatic force and hydrodynamic force. The hydrostatic force acting on the submersible includes the gravity of the submersible and the buoyancy acting on the wet surface area of the submersible; the submersible is affected by ocean internal wave hydrodynamic forces in an actual fluid, which are considered from two aspects: inertial hydrodynamic force and viscous hydrodynamic force. (2) Based on the Newton's second law of motion of the submersible, calculate the horizontal and vertical accelerations of the submersible: Use high spatio-temporal resolution ocean internal wave data to construct a two-dimensional ocean density jump profile. According to the forces acting on the submersible affected by the internal wave density jump given in step (1), obtain the Newton's second law of motion of the submersible. In Figure 2 of the specification, in step 2, calculate the gravity and buoyancy acting on the submersible by combining the mass, volume data of the submersible and the density data of the fluid around the submersible; use the added mass, (angular) acceleration, wet surface area, velocity, length, maximum cross-sectional area data of the submersible, the pressure drag coefficient, friction drag coefficient, density, Reynolds number, dynamic viscosity, velocity data of the fluid around the submersible to calculate the inertial hydrodynamic force and viscous hydrodynamic force acting on the submersible. Ocean internal waves propagate at a certain speed, and the hydrodynamic forces acting on the submersible change in real time with the ocean internal wave data and the movement parameters of the submersible. The submersible has a real-time changing acceleration in both the horizontal and vertical directions, controlling the movement of the submersible in the horizontal and vertical directions. (3) Based on the torque equation of the submersible, calculate the longitudinal angular acceleration of the submersible and simulate the movement trajectory of the submersible affected by ocean internal waves: In Figure 2 of the specification, in step 3, calculate the torque acting on the submersible based on the torque and the length of the force arm acting on the submersible. In the motion equation of the submersible, the real-time changing ocean internal waves cause the submersible to generate a corresponding longitudinal torque, and there is a real-time changing angular acceleration in the longitudinal inclination direction of the submersible. Combining the (angular) accelerations of the submersible in the horizontal, vertical, and longitudinal inclination directions, the present invention uses calculus to control the acting time of the hydrodynamic forces on the submersible, calculates the movement trajectory of the submersible in each time interval, and fits the vertical plane movement trajectory of the submersible.

2. The vertical plane motion trajectory of the simulated submersible affected by internal waves according to claim 1, wherein Using high spatio-temporal resolution internal wave data and submersible property data, the fluid properties at different locations are different. When a submersible encounters internal waves, it may be affected by complex hydrodynamic forces in multiple different directions, making the movement trajectory of the submersible closer to the real situation. On the other hand, visualizing the movement trajectory of the submersible reveals the movement law of the influence of internal waves on the submersible, provides assistance for the operation decision-making when the submersible encounters complex internal waves, and lays a certain foundation for the research on the influence of internal waves on the movement of the submersible.

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