Nosepiece for suppressing a water-entry cavity

Abstract

A nosepiece is provided with a recess or cup shape with internal dimensions that provides cavity suppression of a body entering an air and water interface. The nosepiece includes a circular portion with a diameter connectable to a nose of the body. The circular portion has a cylindrical first section and a cylindrical second section with the recess as the formed cup in the first section at a depth where the diameter and depth are selected based on a Weber number for the body such that a cavity is suppressed as the nosepiece and the body enter the air and water interface.

Claims

1. A nosepiece for suppressing a cavity formed by a body with a nose entering a fluid medium, said nosepiece comprising: a circular portion with a diameter D connected to the nose of the body, said circular portion having a cylindrical first section and a cylindrical second section with a combined length of said first cylindrical portion and said second cylindrical portion being L; and a recess as a formed cup in said first section at a depth h; and wherein the dimensions for diameter D and depth h are selected based on a Weber number for the body such that a cavity is suppressed as said nosepiece and the body enter the fluid medium.

2. The nosepiece in accordance with claim 1, wherein said recess has interior walls extending from said first section as a wedge inward to a base of said recess with said base being perpendicular to outside walls of said first section.

3. The nosepiece in accordance with claim 2 wherein said wedge extends to said base at an angle 10.

4. The nosepiece in accordance with claim 3, wherein said circular portion is manufactured as a part of said body.

5. The nosepiece in accordance with claim 3 wherein said circular portion comprises a frangible portion attachable to said body; and wherein said circular portion detaches from said body following cavity suppression.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other objects, features and advantages of the present invention will become apparent upon reference to the following description of the preferred embodiments and to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein:

(2) FIG. 1 is a prior art side view of a typical water entry of a body showing cavity formation in the water;

(3) FIG. 2 is a side view of the nosepiece of the present invention;

(4) FIG. 3 is a side view of water entry of a body with the nosepiece achieving cavity suppression; and

(5) FIG. 4 is a graph of various cavity and splash regimes for water entry.

DETAILED DESCRIPTION OF THE INVENTION

(6) Referring to FIG. 2, a nosepiece 10 of the present invention suppresses an air cavity around the body 100 upon vertical water entry. The nosepiece 10 consists of a body 12 having a circular cross section with a first end section 14, a second end section 16 and a diameter D. The body 12 has a recess 18 with a depth h. The walls 22 of the body 12 have a wedge cross-section expanding from the second end section 16 at an angle . In some embodiments, the angle could be small (i.e., 10). The length L of the walls 22 need only be greater than the depth h of the recess 18.

(7) It is the specific ratio h/D for a given operating Weber number (We) that allows for the cavity suppression. FIG. 3 shows, by illustration, the water entry of the body 100 with the nosepiece 10 causing cavity suppression. A variety of cavity regimes are possible with the nosepiece 10 as the cavity regimes depend on the combination of h/D and We. Cavity suppression will occur when the only gas in the cavity is that which was initially trapped in the recess 18 upon water impact and has evacuated into the toroidal cavity. This is referred to as a closed torus.

(8) FIG. 4 is a graph of cavity and splash regimes for the water entry of a body with the inventive nosepiece 10 at different values of h/D and We. The graph depicts six different regimes of water entry at the moment of a cavity seal. As shown, a flat face with We=516 results in a deep seal.

(9) When h/D=0.12 in a recess and a cupped face and We=562, this results in a partial surface seal. When h/D=0.16 and We=1016, this results in a thick rim seal. When h/D=0.16 and We=2972, this results in a thin rim seal. When h/D=0.32 and We=2949, this results in a below-surface seal. When h/D=0.63 and We=5916, this produces a closed torus.

(10) The operating conditions for the body 100 determine the impact speed U and diameter D of the body to set the Weber number, We=U.sup.2D/. At a given value of We, the graph of cavity and splash regimes can be referenced to find the minimum value of h/D for the nosepiece 10 to suppress a cavity.

(11) The disclosed invention allows for the suppression of an air cavity upon water entry under conditions (i.e., impact We) that would otherwise produce cavities for most common nose geometries such as ogives, cones and disks. The nosepiece 10 is a simple and passive device having h/D in a specific range for a specific operating We.

(12) The nosepiece 10 can be manufactured as a separate portion and attached to the body 100. In some embodiments, the nosepiece 10 can be integrated structurally into the body and manufactured as part of the body. In other embodiments, the nosepiece 10 can be a frangible nose cone mounted to the body 100. This allows the nosepiece 10 to suppress the cavity before breaking off during impact. The body 100 can then employ a more advantageous nose shape for underwater travel following the water entry.

(13) It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.