A method for variable-speed sailing body constraint model underwater launching experiment

Abstract

This invention provides an underwater launch experiment method for a variable-speed constrained model of a carrier. It mainly includes a decompression chamber, a synchronous belt slide, a servo motor, a host computer, and a carrier model. This invention utilizes the synchronous belt slide and servo motor arranged within the decompression chamber to control the motion of the carrier model. The motion parameters of the controlled carrier model satisfy the requirements of the similarity law for carrier exiting the water. This invention can maintain a negative pressure environment while controlling the trajectory of the carrier model exiting the water and simulating the variable-speed motion state of the prototype underwater carrier during its exit from the water, satisfying the requirements of the similarity law for exiting the water of a scaled-down model, and taking into account the influence of the free surface on the exiting process, thus achieving a realistic simulation of the prototype carrier's exiting the water motion. This invention is applicable to the simulation of the exiting water motion of scaled-down models under different scale ratios and different prototype motion parameters. It also has reference value for the simulation process of other hydraulic machinery scaled-down model tests and has high practical engineering significance.

Description

Technical Field

[0001] This invention belongs to the field of underwater launch tests of vehicle models, and specifically relates to an underwater launch test method for a constrained vehicle model with variable speed. Background Technology

[0002] Conducting scaled-down surface-launch tests in the laboratory is a crucial research method for understanding the surface-launch performance of marine equipment such as surface-launched vehicles and guiding their engineering design. The key to accurately conducting scaled-down model tests lies in realistically simulating the prototype's surface-launch motion. Conventional laboratory facilities such as circulating water tanks and tunnels cannot effectively simulate the constantly changing speed and movement of the surface-launching segment. While free-launch devices can approximate the prototype's motion as closely as possible, their surface-launch trajectory cannot be controlled, making it difficult to guarantee trajectory stability during simulation; that is, it is difficult to maintain a preset angle of motion throughout the entire surface-launching motion. Therefore, many mechanistic surface-launch tests requiring controlled variables (such as trajectory) cannot be conducted.

[0003] Patent CN113639957A discloses a device platform for underwater launch tests. This device uses underwater guide rails and a catapult to launch a scaled-down model out of the water. However, this device cannot control the trajectory of the model after it is launched from the tube. Furthermore, free catapults make it difficult to precisely control the speed of the launch vehicle each time it exits the water, making it difficult to launch multiple times at the same speed. Additionally, its water tank height is only 2 meters, which cannot meet the water depth requirements for launching large-scale models. Patent CN114486169A discloses a controllable parameter launch experimental device for underwater vehicles. This device can control the motion parameters of the launched vehicle to some extent, but the control process cannot meet the requirements of the similarity law, and cannot realistically simulate the launch process of the prototype vehicle. Therefore, to meet the actual needs of marine equipment development and promote the development of underwater launch test technology in laboratories, it is necessary to develop a principle and method for underwater launch simulation of a variable-speed constrained model of a vehicle that can simulate the underwater launch process of a prototype vehicle under the premise of controllable trajectory. Summary of the Invention

[0004] The purpose of this invention is to provide a method for underwater launch experiments using a constrained model of a variable-speed vehicle.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for underwater launch experiment of a constrained model of a variable-speed vehicle is characterized by comprising a decompression chamber, a synchronous belt slide, a servo motor, a host computer, and a vehicle model; the motion control of the vehicle model is controlled by the synchronous belt slide arranged in the decompression chamber, and the servo motor installed on the top of the synchronous belt slide drives the vehicle model to move by driving the transmission belt in the synchronous belt slide; the decompression chamber provides a negative pressure test environment; the host computer controls the rotation process of the servo motor and controls the parameters of the motion process of the vehicle model; the motion process of the vehicle model controlled by the servo motor meets the requirements of the similarity law of water exit motion; after the vehicle model moves out of the water, the servo motor is controlled to make the vehicle model move back to the origin.

[0007] Furthermore, the similarity parameters of the water exit motion similarity law during the motion of the aforementioned aircraft model are:

[0008]

[0009] The motion parameters of the prototype with index p and the model with index m must satisfy the following similarity ratio:

[0010] P am =λP ap ; h m =λh p ; D m =λD p L m =λL p

[0011] In the formula, the diameter of the vehicle model is D; the length is L; the launch depth is H; the mass is M; the initial velocity is V0; the final velocity, the velocity at the free surface, is V1; ΔV = V0 - V1; and the water surface pressure is P. a The density of water is ρ. L The duration of motion in water is t; the kinematic viscosity of water is υ; the acceleration due to gravity is g; the scaling ratio is λ, then: D m =λD p L m =λL p M m =λ 3 M p ;

[0012] Control model environmental pressure P am To meet the similarity requirement, the rotation process of the servo motor is controlled by the host computer to ensure that the acceleration of the model during its water exit motion is equal to that of the prototype, thus achieving t m h m ΔV m The similarity rate requirement must be met; and the model scaling ratio λ must also meet the following requirements: The flow states of the model and the prototype are consistent, and the surfaces of both the model and the prototype are turbulent boundary layers; where Re p It is the prototype Reynolds number.

[0013] Furthermore, the out-of-water motion of the controlled model vehicle satisfies the requirements of similar Froude number, cavitation number, and Reynolds number.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention enables the creation of negative pressure environments for underwater vehicles of varying scales under ballistic control, ensuring that their emergence motion meets the similarity law requirements of scaled-up models. It also takes into account the influence of the free surface, realistically simulating the variable-speed motion of the vehicle during emergence under laboratory conditions. The motion is controlled by high-precision servo motors and synchronous belt slides, resulting in high accuracy and repeatability of the vehicle's emergence motion parameters. Furthermore, the invention allows for the vehicle model to return to its underwater origin, enabling repeated testing within a short time and significantly improving efficiency. Moreover, this invention eliminates the need for mass similarity laws, greatly reducing the requirements for model fabrication and materials, and significantly improving the economic efficiency of model testing. This invention can be applied to scaled-up testing of underwater vehicles and related marine engineering projects, and also has reference value for scaled-up testing of other hydraulic machinery, possessing significant practical engineering implications. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall device of the present invention;

[0017] Figure 2 The above are time-series curves of acceleration, velocity, and displacement of an example of a spacecraft in this invention. Detailed Implementation

[0018] The present invention will now be further described with reference to the accompanying drawings.

[0019] This invention discloses an underwater launch experiment method for a constrained model of a variable-speed vehicle, comprising: a decompression chamber 1, a synchronous belt slide 2, a servo motor 3, a host computer, and a vehicle model 4. Figure 1As shown, the motion control of the aircraft model 4 is controlled by a synchronous belt slide 2 arranged inside the decompression chamber 1. A servo motor 3 mounted on top of the synchronous belt slide 2 drives the aircraft model 4 to move via a transmission belt within the slide 2. The decompression chamber 1 provides a negative pressure testing environment. The motion parameters of the aircraft model 4 (such as speed and acceleration) can be controlled by a host computer controlling the rotation of the servo motor 3. The motion of the aircraft model 4 controlled by the servo motor 3 meets the requirements of the water exit motion similarity law. After the aircraft model 4 exits the water, the servo motor 3 can be controlled to return the model to its origin, allowing the test to restart quickly and ensuring high testing efficiency. Due to the high precision of the servo motor rotation control, the control accuracy and repeatability of the aircraft model's motion process are guaranteed.

[0020] The derivation of the similarity law of the water-emerging motion of the aircraft model and its water-emerging control process are as follows:

[0021] Let the diameter of the launch vehicle be D, its length be L, its launch depth be H, its mass be M, its initial velocity be V0, its final velocity (the velocity at the free surface) be V1, ΔV = V0 - V1, and the water surface pressure be P. a The density of water is ρ L The duration of motion in the water is t, the kinematic viscosity of the water is υ, and the acceleration due to gravity is g.

[0022] Let the scaling ratio be λ, then: D m =λD p L m =λL p M m =λ 3 M p .

[0023] By deriving from the π theorem, for the above-mentioned parameters, the following similarity parameters can be obtained:

[0024]

[0025] Based on the above similarity π parameters, the motion parameters of the prototype (subscript p) and the model (subscript m) must satisfy the following similarity ratio:

[0026] P am =λP ap ; h m =λh p ;

[0027] As can be seen from the above similarity rate, the environment in which the model moves needs to be maintained under negative pressure. By using a pressure-reducing pump in conjunction with the pressure-reducing chamber in the system of this invention, the environmental pressure P of the model can be controlled. amThe similarity requirement is met. The rotation process of the servo motor is controlled by a host computer to ensure that the acceleration of the model during its water exit motion is equal to that of the prototype, thus ensuring that t... m h m ΔV m The similarity requirement is met. Since the model moves in a constrained manner, only the model diameter D and length L need to be similar to the prototype in terms of model structure; mass M is not a requirement. This greatly reduces the requirements for model fabrication and materials.

[0028] When the model environmental pressure P am and its motion parameter t m h m ΔV m When both satisfy the similarity ratio, the Fourier numbers and cavitation numbers of the model and prototype automatically satisfy the similarity requirement. The Reynolds numbers of the model during motion are also similar. When the prototype of the aircraft moves out of the water, the prototype's Reynolds number Re... p Often greater than the critical Reynolds number Re c (Re c =) 3.5~5(×10 5 This means that when the prototype navigates in water, its surface boundary layer is in a turbulent state. This requires that the surface boundary layer of the scaled-down model should also be in a turbulent state during testing. Therefore, to ensure that the model's surface boundary layer is always in a turbulent state, let the length of the laminar boundary layer of the model be x. lm With the length L of the model m The ratio is 0.1, meaning the length of the laminar boundary layer on the surface of the model during water discharge is negligible. Thus:

[0029]

[0030] From the above formula, we can obtain:

[0031]

[0032] In the formula, L mc This represents the minimum model length required to guarantee the fully turbulent state of the boundary layer on the model surface. When the model length L... m Greater than L mc At that time, the surface of the vehicle model can be considered as a turbulent boundary layer, that is:

[0033]

[0034]

[0035] set up When the model scaling ratio λ is greater than λ0, the flow states of the model and the prototype are the same, both being turbulent boundary layers. Therefore, the scaling ratio of the scaled model cannot be too small, and it also needs to meet the corresponding numerical requirements.

[0036] According to the above method, this invention can make the water exit motion of different scaled-down vehicles meet the requirements of the similarity law of water exit motion of scaled-down models under ballistic controllable conditions, and realistically simulate the water exit process of vehicles under laboratory conditions.

[0037] Let the diameter of the launch vehicle be D, its length be L, its launch depth be H, its mass be M, its initial velocity be V0, its final velocity (the velocity at the free surface) be V1, ΔV = V0 - V1, and the water surface pressure be P. a The density of water is ρ L The duration of motion in the water is t, the kinematic viscosity of the water is υ, the acceleration due to gravity is g, and the scale ratio is λ. The motion process of the floating body model controlled by the servo motor should satisfy the following similarity law for the motion out of the water:

[0038]

[0039] By controlling the decompression pump and the decompression chamber in this invention, a negative pressure environment P is created for the model's movement. am The similarity requirement is met. The rotation process of the servo motor is controlled by a host computer to ensure that the acceleration of the model during its water exit motion is equal to that of the prototype, so that t... m h m ΔV m The similarity requirement must be met. To simultaneously satisfy the Reynolds number similarity during the model's water exit process, for the model scaling ratio λ, according to the formula:

[0040]

[0041] Based on available online data on Trident's operation, Re p ≈3.51×10 8 , That is, the lower limit of the model scaling ratio is 1:17.

[0042] The simulation process for the prototype vehicle's emergence from the water is as follows:

[0043] The prototype vehicle's emergence process is divided into three stages: acceleration upon exiting the tube, deceleration during underwater navigation, and deceleration upon exiting the water. Based on the similarity law of water exit motion, the simulation of these three stages is designed as follows for the scaled-down model: the scaled-down model first accelerates to a specified maximum speed, then decelerates until it exits the water.

[0044] Assume the acceleration a1 during the prototype vehicle's exit from the tube is 20 m / s². 2 The initial velocity upon exiting the tube is 30 m / s, and the water depth is 30 m. Neglecting buoyancy and fluid resistance, and assuming the prototype's motion in the water is uniformly decelerated with an acceleration of approximately -g, i.e., acceleration a2 is approximately -10 m / s². 2If the acceleration changes from a1 to a2 in 0.05s, then the slope of the acceleration change, b, is 60°.

[0045] Let the model scaling ratio λ be 1:11.5, to satisfy... The requirements are as follows: The initial velocity V1 of the model when it exits the cylinder is 8.9 m / s, and the water depth of the model is h. m =h p / λ≈2.61m. The decompression environment of the model is regulated by a decompression pump. Therefore, the time for the model to maintain acceleration a1 is t1=(V1-a1) / ... 2 / 2b) / a1=0.433s, the moment when the acceleration just changes to a1 is t2=t1+0.05=0.483s.

[0046] The change in the model's velocity is then calculated using the following formula:

[0047]

[0048] The specific motion process of water exiting the scaled-down model is as follows: Figure 2 As shown, the model operates at 20 m / s 2 The acceleration increases to 8.7 m / s², then decreases to -10 m / s². 2 The acceleration decreased to -10 m / s². 2 At this point, the model's velocity was 8.9 m / s, and the simulation of the model exiting the cylinder section was complete. Subsequently, the model maintained a velocity of -10 m / s in the water. 2 The model accelerates and travels a distance of 2.61m before reaching the water surface. Finally, it maintains a speed of -10m / s². 2 The acceleration is such that the model moves until it is completely out of the water, thus completing the simulation of the deceleration process during the underwater navigation section and the deceleration process during the water exit section.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for a variable-speed cruise vehicle constrained-mode underwater launch experiment, characterized in that: The system includes a decompression chamber (1), a synchronous belt slide (2), a servo motor (3), a host computer, and a model of the aircraft (4). The motion control of the model of the aircraft (4) is controlled by the synchronous belt slide (2) arranged in the decompression chamber (1). The servo motor (3) installed on the top of the synchronous belt slide (2) drives the model of the aircraft (4) to move by driving the transmission belt in the synchronous belt slide (2). The decompression chamber (1) provides a negative pressure test environment. The host computer controls the rotation process of the servo motor (3) to control the parameters of the motion process of the model of the aircraft (4). The motion process of the model of the aircraft (4) controlled by the servo motor (3) meets the requirements of the similarity law of water exit motion. After the model of the aircraft (4) moves out of the water, the servo motor (3) is controlled to make the model of the aircraft (4) move back to the origin. The similarity parameters of the similarity law of water exit motion during the motion process of the model of the aircraft (4) are: The motion parameters of the prototype with index p and the model with index m must satisfy the following similarity ratio: ; ; ; ; ;D m =λD p ;L m =λL p In the formula, the diameter of the vehicle model is D; the length is L; the launch depth is H; the mass is M; the initial velocity is V0; the final velocity, the velocity at the free surface, is V1; ΔV = V0 - V1; and the water surface pressure is P. a The density of water is ρ L The duration of motion in water is t; the kinematic viscosity of water is υ; the acceleration due to gravity is g; the scaling ratio is λ, then: D m =λD p L m =λL p M m =λ 3 M p ; Control model environmental pressure To meet the similarity requirement, the rotation process of the servo motor (3) is controlled by the host computer to make the acceleration of the model during the water outflow process equal to that of the prototype. , , The similarity rate requirement is met; and the model scaling ratio is also met. Requirements must be met: If the flow states of the model and the prototype are consistent, then the surfaces of both the model and the prototype are turbulent boundary layers; where Re p It is the prototype Reynolds number.

2. The method according to claim 1, wherein the method is characterized in that: The water-emerging motion of the controlled model vehicle (4) satisfies the requirements of similar Froude number, cavitation number, and Reynolds number.

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