A method for suppressing cross-medium water entry interference of a supercavitating projectile based on optimization of keel length

Abstract

The application provides a supercavitation projectile cross-medium water entry interference suppression method based on optimization of a cymbal length, comprising the following steps: S1, establishing a projectile-cymbal parameterized model, and demarcating an optimization interval of the cymbal length; S2, coupling a multiphase flow model, a cavitation model and a dynamic grid method to simulate a separation process of the projectile and the cymbal, and obtaining original data of the projectile; S3, performing comparative simulation of multiple groups of different cymbal lengths, and quantitatively extracting three key performance indexes of a supercavity symmetry, a pitch angle deviation and a speed attenuation rate by using the original data of the projectile; and S4, establishing a multi-target optimization criterion based on an interference index, determining a globally optimal cymbal length parameter, and completing the whole optimization process. The application can solve the problem caused by improper design of the cymbal length when the supercavitation projectile and the cymbal cooperatively enter water.

Description

Technical Field

[0001] This invention belongs to the field of underwater weapon design, specifically relating to a method for suppressing interference when a supercavitating projectile enters water across a medium based on the optimization of the card lobe length. Background Technology

[0002] Supercavitation technology utilizes high-speed motion to create an enveloping air cavity (cavitation) around the projectile, ensuring that only the nose of the projectile contacts the water, reducing drag to 1 / 5 to 1 / 10 of traditional underwater weapons. Supercavitating projectiles face extreme fluid impact and attitude instability risks upon high-speed water entry. While the squeegee, a key component, maintains the initial trajectory, its length design presents a fundamental contradiction: a long squeegee (≈1.0~1.5 times the projectile diameter) prolongs fluid shielding time, but separation lag leads to strong vortex shedding interference, causing projectile pitch oscillations >8°; a short squeegee (≈0.5 times the projectile diameter) accelerates separation and reduces interference, but weakens cavitation protection, causing premature cavitation collapse after water entry and accelerated velocity decay. Existing technologies rely on trial and error, failing to quantify the mapping relationship between squeegee length and water entry stability, and traditional simulations struggle to accurately simulate the dynamic separation flow field, resulting in long design cycles, high costs, and poor stability. Summary of the Invention

[0003] The purpose of this invention is to provide a method for suppressing interference when a supercavitating projectile enters water across a medium based on the optimization of the spool length, aiming to solve the problem caused by improper design of the spool length when the supercavitating projectile and the spool enter water together.

[0004] A method for suppressing cross-medium water entry interference of supercavitating projectiles based on card lobe length optimization includes:

[0005] Step S1: Establish a projectile-slot parametric model and define the optimization range for the slot length;

[0006] Step S2: Simulate the separation process of the projectile and the cavitation model by coupling the multiphase flow model with the dynamic mesh method to obtain the original data of the projectile.

[0007] Step S3: Perform comparative simulations of multiple sets of different lobes, and quantitatively extract three key performance indicators—cavitation symmetry, pitch angle deviation, and velocity decay rate—using various raw data of the projectile.

[0008] Step S4: Establish a multi-objective optimization criterion based on the interference index, determine the globally optimal cardioid length parameter, and complete the entire optimization process.

[0009] The significant advantages of this invention compared to existing technologies are:

[0010] (1) By establishing a quantitative mapping model between the card plate length and the stability of water entry, the problem of blindness caused by relying on experience and trial and error in traditional design was solved, and the leap from qualitative design to quantitative optimization was realized, which significantly improved the design efficiency and reliability.

[0011] (2) Based on the multi-objective optimization criteria, the three key indicators of cavitation symmetry, pitch angle deviation and velocity decay rate are optimized in a coordinated manner, which overcomes the performance imbalance caused by single parameter optimization and ensures good cavitation morphology and velocity retention while suppressing pitch oscillation.

[0012] (3) The method has clear engineering applicability. Through the technical path of combining parametric modeling and systematic simulation, it not only greatly reduces the test cost, but also the optimized design criteria formed can directly guide the design of the lobes of supercavitating projectiles of different sizes, and has good promotion and application value. Attached Figure Description

[0013] Figure 1 This is a flowchart of a water ingress interference suppression method based on card flap length optimization.

[0014] Figure 2 This is a model diagram of a water-launching projectile with a locking flap, according to an embodiment of the present invention.

[0015] Figure 3 The pressure cloud diagram after water immersion is provided for an embodiment of the present invention.

[0016] Figure 4 A diagram showing the pitch angle variation provided for an embodiment of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0018] Combination Figures 1-4 This invention proposes a method for suppressing interference during cross-medium water entry of supercavitating projectiles based on card lobe length optimization, such as... Figure 1 As shown, it mainly includes:

[0019] Step S1: Establish a projectile-slot parametric model and define a reasonable slot optimization range;

[0020] A parametric assembly model of the projectile body and the separable flaps was established. The projectile body adopts a standard supercavitary shape design with a nose cone angle of 15° and a length-to-diameter ratio of 5:1 for the cylindrical section. The assembly gap between the projectile body 1 and the flaps 2 is controlled within 0.2mm, simulating realistic manufacturing tolerances. The opening angle is fixed at 30° to avoid introducing additional interference variables. The model diagram is shown below. Figure 2 As shown. The length of the card flap. As a key design variable, based on engineering experience and preliminary fluid analysis, its optimization range is defined as 0.6D to 1.0D (where D is the projectile diameter). Within this range, a parameter space containing more than 5 sample points is established (e.g., when D = 100 mm). =60mm, 70mm, 80mm, 90mm, 100mm), ensuring design freedom and covering possible optimization areas.

[0021] Step S2: Construct a cross-medium water entry numerical simulation system, and accurately simulate the separation process of the projectile and the cavitation lobe by coupling a multiphase flow model with a cavitation model and a dynamic mesh method;

[0022] A computational fluid dynamics (CFD) approach was used to construct a simulation model for cross-medium water ingress. This model couples the VOF multiphase flow method with the Schnerr-Sauer cavitation model to accurately simulate the cavitation evolution process.

[0023] ;

[0024] in It represents the volume fraction of the aqueous phase. This refers to the gas phase volume fraction. For the density of water, The projectile velocity vector, The relative velocity vector of the projectile. For simulation time, For gradient, The cavitation mass source term is defined. The model and simulation parameters for the projectile and slugs are set as follows: Projectile body: Fixed supercavitary shape (cone half-angle 15°, cylindrical section length-to-diameter ratio 5:1). Slug design: Length... Set as the core variable, the optimization range is 0.6 to 1.0 times the projectile diameter D (e.g., when D = 100 mm). =60 mm, 70 mm, 80 mm, 90 mm, 100 mm); the opening angle is fixed at 30° to avoid introducing additional interference variables; the assembly gap is set to 0.2 mm to simulate real manufacturing tolerances. Physical model: A VOF multiphase flow model coupled with a Schnerr-Sauer cavitation model is used; the turbulence model is SST k-ω (near-wall y⁺≤1, inlet turbulence intensity 5%). Motion settings: The projectile body is defined as a 6-DOF rigid body, driven by hydrodynamics; mesh system: Overlapping mesh is used: the background domain basic size is 5 mm, and the projectile / cardiolobe domain is locally refined to 0.3 mm; the gas-liquid interface is dynamically adaptively refined to ensure cavitation interface resolution. By simulating the separation process, the original data of the projectile (pitch angle) are obtained. Projectile speed cavitation area on both sides of the longitudinal section of the projectile , This prepares the data for post-processing to extract performance metrics. The simulation results are as follows: Figure 3 As shown, computational fluid dynamics analysis reveals that a significant asymmetric pressure field is formed beneath the card flap upon contact with the water surface. The maximum pressure gradient occurs at the edge of the card flap, with a peak pressure reaching 3.5 MPa. This asymmetric pressure distribution generates an additional pitching moment, directly altering the projectile's angle of attack upon entering the water, and causing corresponding deformation of the cavitation morphology.

[0025] Step S3: Perform comparative simulations of multiple sets of different cardioid lengths to quantitatively extract three key performance indicators: cavitation symmetry, pitch angle deviation, and velocity decay rate.

[0026] Within the established simulation system, a series of comparative simulations covering the design range were performed. Each simulation simulated the process of a projectile entering water at an initial velocity of 600 m / s at an angle, with a calculation duration of 2 ms. Three key performance indicators were quantitatively extracted through post-processing:

[0027] Cavitation symmetry : ;

[0028] in , The area of ​​the cavitation on both sides of the longitudinal section of the projectile.

[0029] Pitch angle deviation : ;

[0030] in The elevation angle of the projectile upon entering the water. After the projectile enters the water The pitch angle at 2 ms.

[0031] Velocity decay rate : ;

[0032] in The initial velocity of the projectile upon entering the water, After the projectile enters the water =2 ms speed.

[0033] The complete dynamic response under each set of parameters was recorded, and three key performance indicators—cavitation symmetry, pitch angle deviation, and velocity decay rate—were extracted. Based on this, a quantitative mapping model between the cardioid length and performance indicators was constructed through systematic data analysis, as detailed below:

[0034] (1) Obtain multiple sets of The sample data that constitutes the data;

[0035] (2) Through systematic mathematical processing methods, discrete simulation data are transformed into continuous design guidance models; specifically, this includes: normalizing the obtained sample dataset to eliminate the influence of dimensions.

[0036] ;

[0037] in This is the normalized cardiopulmonary bypass length. To optimize the minimum cardioid length of the interval, To optimize the maximum cardioid length of the interval, This is the original cardiopulmonary bypass length value. This represents the normalized cavitation symmetry value. To optimize the minimum cavitation symmetry value of the interval, To optimize the maximum cavitation symmetry value of the interval, This represents the original cavitation symmetry value. This is the normalized pitch angle deviation value. To optimize the minimum pitch angle deviation value of the interval, To optimize the maximum pitch angle deviation value in the interval, This is the original pitch angle deviation value. The normalized velocity decay rate, To optimize the minimum velocity decay rate in the interval, To optimize the maximum velocity decay rate in the interval, This represents the original velocity decay rate.

[0038] A quadratic response surface model is used to establish the mapping relationship between parameters and performance:

[0039] ;

[0040] ;

[0041] ;

[0042] in For the length of the cardiopulmonary bypass, , , , , , , , , For regression coefficients, This is the error term.

[0043] (3) The prediction accuracy of the model is evaluated by leave-one-out cross-validation, requiring a determination coefficient R² ≥ 0.9 to ensure the reliability of the mapping relationship;

[0044] (4) Based on the established mapping relationship, calculate the sensitivity of each performance index to the card lobe length:

[0045] ;

[0046] ;

[0047] ;

[0048] in To find the partial derivative, , , , , , For regression coefficients, For the length of the cardiopulmonary bypass, Due to cavitation symmetry, For pitch angle deviation, This represents the velocity decay rate.

[0049] Firstly, through Confirm the degree of pitch oscillation of the projectile, and then... The root cause of the problem was found to be the asymmetric flow field induced by the cardiopulmonary bypass, which was finally addressed through... Make sure to change While reducing pitch oscillation, it avoids the side effects of losing cavitation protection and drastically reducing velocity. In this example, a slat length of 0.6–1.0 times the projectile diameter is used for simulation, and the pitch angle curve is shown below. Figure 4 As shown, by selecting a reasonable slat length, the maximum pitch angle deviation of the projectile is made less than 5°, thus solving the problem of pitch oscillation of the long slat.

[0050] Step S4: Establish multi-objective optimization criteria, introduce a comprehensive interference evaluation index, determine the globally optimal cardioid length parameter, and complete the entire optimization process.

[0051] Establish a multi-objective optimization criterion based on the disturbance index:

[0052] (Require ≤1);

[0053] in For pitch angle deviation, This is a reference value for pitch angle deviation. Due to cavitation symmetry, This is a reference value for cavitation symmetry. For velocity decay rate, This is a reference value for the velocity decay rate. , , These are the weighting coefficients for pitch angle deviation, cavitation symmetry, and velocity decay rate, respectively, and they satisfy the following: .

[0054] In this example, the pitch angle deviation reference value is used. 5°, reference value for cavitation symmetry The reference value for velocity decay rate is 0.90. It is 15%, and take The range is 0.4-0.6. The range is 0.2-0.4. The range is 0.1-0.3. First, filter out those that simultaneously meet the criteria. ≥0.90 ≤5° and The feasible solution set is ≤15%, and then the interference index of each feasible solution is calculated. Through analysis, the selection makes... The minimum sag length is taken as the globally optimal parameter. Practical applications show that the optimized parameters determined by this method can reduce pitch angle deviation by more than 30% and improve velocity decay by more than 15%, effectively enhancing the projectile's water entry stability. This method establishes a complete sag length optimization process through the organic combination of parametric modeling, accurate simulation, performance quantification, and multi-objective decision-making, providing reliable technical support for the engineering design of supercavitating projectiles.

[0055] This invention is not only applicable to the 12 mm diameter projectile used in the above embodiments, but can also be extended to the design of supercavitating projectiles with different sizes and speeds. By simply adjusting the optimized range of the slat length and the corresponding simulation parameters proportionally, the method disclosed in this invention can still effectively suppress water entry interference.

Claims

1. A method for suppressing interference during cross-medium water entry of supercavitating projectiles based on card lobe length optimization, characterized in that, include: Step S1: Establish a projectile-slot parametric model and define the optimization range for the slot length; Step S2: Simulate the separation process of the projectile and the cavitation model by coupling the multiphase flow model with the dynamic mesh method to obtain the original data of the projectile. Step S3: Perform comparative simulations of multiple sets of different lobes, and quantitatively extract three key performance indicators—cavitation symmetry, pitch angle deviation, and velocity decay rate—using various raw data of the projectile. Step S4: Establish a multi-objective optimization criterion based on the interference index, determine the globally optimal cardioid length parameter, and complete the entire optimization process; The multi-objective optimization criterion based on the disturbance index is established as follows: ， in For pitch angle deviation, This is a reference value for pitch angle deviation. Due to cavitation symmetry, This is a reference value for cavitation symmetry. For velocity decay rate, This is a reference value for the velocity decay rate. , , These are the weighting coefficients for pitch angle deviation, cavitation symmetry, and velocity decay rate, respectively, and they satisfy the following: ; Filtering simultaneously satisfies ≥ , ≤ , The solution set, choose one that makes The cardiopulmonary bypass length with the smallest value is taken as the globally optimal parameter.

2. The method for suppressing interference during cross-medium water entry of supercavitating projectiles based on card lobe length optimization according to claim 1, characterized in that, The optimal range for the card flap length is set between 0.6D and 1.0D, where D is the projectile diameter.

3. The method for suppressing interference during transmedium water entry of supercavitating projectiles based on card lobe length optimization according to claim 1, characterized in that, The multiphase flow model coupled with the cavitation model adopts the VOF multiphase flow model coupled with the Schnerr-Sauer cavitation model: ， in It represents the volume fraction of the aqueous phase. This refers to the gas phase volume fraction. For the density of water, The projectile velocity vector, The relative velocity vector of the projectile. For simulation time, For gradient, This is a cavitation quality source term.

4. The method for suppressing interference during cross-medium water entry of supercavitating projectiles based on card lobe length optimization according to claim 1, characterized in that, The three key performance indicators are: Cavitation symmetry : ; in , The cavitation area on both sides of the longitudinal section of the projectile; Pitch angle deviation : ; in The elevation angle of the projectile upon entering the water. Time after the projectile enters the water The pitch angle at that time; Velocity decay rate : ; in The initial velocity of the projectile upon entering the water, Time after the projectile enters the water The speed at which time.

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