Cavitating Core Geometry for Air-Water Stability
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Solution Overview
Problem
Existing cavitating cores for ammunition fail to maintain stability and range when transitioning between air and water due to inadequate geometry, leading to increased drag and scattering, resulting in reduced effectiveness in hitting underwater targets.
Innovation Solution
A cavitating core design with a contour matching the forward end of the cavity, featuring a quadric nose surface, a narrow circular groove, and a multiblade empennage aft part, made from materials with varying densities, optimized to reduce cavitation drag and maintain stability across both environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cavitating core uses a conventional geometry with length more than 21 calibers, then it can travel stably in water due to natural cavity formation, but it loses stability in air and stops at 0.5-0.7m range
Solution Approach 1:
The core employs different geometric characteristics in different sections: the head part has a specific contour matching the cavity shape for stable water travel, while the aft part features a multiblade empennage structure for aerodynamic stabilization in air. This local differentiation allows the single core to satisfy stability requirements in both air and water environments.
Solution Approach 2:
The core design integrates multiple stabilization functions into a single structure. The aft part's multiblade empennage provides aerodynamic stabilization during air flight, while the overall core geometry maintains compatibility with natural cavity formation in water. This multi-functional design enables the core to maintain stability across both air and water media without requiring separate stabilization systems.
2Reliability
If the cavitating core has a secant nose part with large cavitating edge diameter, then it forms a large cavity for stable water travel, but it increases cavitation drag and reduces underwater trajectory range
Solution Approach 1:
The invention optimizes the cavitating edge diameter to a specific range (0.6-0.8 times the core caliber) and adjusts the secant nose part contour parameters to match the natural cavity shape. These parameter optimizations balance cavity stability with drag reduction, allowing the core to maintain reliable water travel while minimizing energy loss to cavitation drag.
3Ease of operation
If the cavitating core uses a multiblade empennage for aerodynamic stabilization, then it achieves stable air flight, but the narrow blades experience deep inertial washing in water increasing scattering
Solution Approach 1:
The empennage blades are designed with non-uniform characteristics: they have sufficient width and area at the root section to resist inertial washing in water, while maintaining the aerodynamic configuration needed for air stabilization. This local differentiation in blade geometry allows the empennage to provide aerodynamic stability without excessive scattering in the underwater phase.
4Ease of manufacture
If the core contour does not match the cavity contour, then manufacturing is simpler, but the core experiences increased drag and reduced range in water
Solution Approach 1:
The core's head part contour is designed to copy or match the natural cavity contour formed during water travel. This geometric copying ensures optimal hydrodynamic performance and minimizes drag, allowing the core to achieve maximum underwater range while maintaining manufacturability through the use of standard geometric forms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enhances the range and stability of the cavitating core, allowing for precise targeting in both air and water by minimizing drag and scattering, while accommodating various ammunition lengths and materials.
Implementation Method 1
high-speed movement of the cavitating core in the water is accompanied by the formation of a natural cavity
Implementation Method 2
harpoon arrows for arbalests and harpoon guns slow down in the water and quickly stop due to the viscous fluid hydrodynamic drag
Implementation Method 3
Stable flight of the cavitating core in the air is provided by its aft part that may have the form of a multiblade empennage at aerodynamic stabilization
Implementation Method 4
At spin-stabilization it may have a cone-cylindrical form to give gyroscopic stability to the core
Implementation Method 5
The largest cavity diameter D K depends on the cavitation number σ, cavitating edge diameter d and its cavitating drag index c x
Data Source
Figure 1~2
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AI summary
The invention relates to ammunition for missile weapon and firearm. The cavitating core of the invention comprises a head part conjugated with a secant nose surface along the cavitating edge, a central part, and an aft part with a gliding surface, wherein the caliber of the core is defined by the maximum diameter of the circle describing the core cross-section. The contour line enveloping the cross-sections from the cavitating edge to the core caliber in the plane of the core axial longitudinal section is limited by the dependence: Dx=d×1+Lx/d×2×sin φ/π1/NN, where Dx - is the current diameter of the core enveloping contour R, mm; d - is the cavitating edge diameter, mm; Lx - is the current distance from the cavitating edge to the core caliber, mm; ϕ = 60°...270° - is the apex angle of the tangents to the secant nose surface at the points of its conjugation with the cavitating edge measured from the side of the head part; N = (2π / ϕ)0,4...(2π / ϕ)0,2 - is the core volume factor, wherein the core caliber is equal to the current diameter of the core enveloping contour Dx. As a result the invention makes it possible to increase the effective distance for hitting underwater targets when shooting from the air to the water and/or during underwater shooting using arbalests, harpoon guns, artillery, small and sporting-and-hunting weapons.