Multi-bilge-line hull with obliquely-lifted forebody of amphibious aircraft

Abstract

The invention belongs to the technical field of hydrodynamic force, and particularly relates to a multi-bilge-line hull with an obliquely-lifted forebody of an amphibious aircraft. Three bilge lines are arranged on a ship body of the multi-bilge-line ship body and include the upper bilge line, the middle bilge line and the lower bilge line, and the upper bilge line, the middle bilge line and the lower bilge line divide the multi-bilge-line ship body into an upper ship body, a middle ship body and a lower ship body. The multi-bilge-line hull adopts an obliquely-lifted front body keel line; spattering restraining strips are arranged on the outer sides of the upper bilge line and the middle bilge line; a water flap is arranged at the stern of the lower hull; the problems that a multi-bilge-line hull of an existing amphibious aircraft is insufficient in sliding stability, poor in splashing performance in waves and large in dampening load are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrodynamics, and in particular relates to a multi-bilge hull with an obliquely rising front body of an amphibious aircraft. Background Art

[0002] The keel line of the forebody of the multi-bilge hull is horizontal, and its planing stability is insufficient; a large amount of whisker-like splashes are generated in the bow area, which splash and impact the propeller and wash the cockpit windshield in the waves; the bottom of the lower hull is horizontal, resulting in a large water load on the lower hull, increasing the weight of the aircraft structure and reducing the aircraft's effective load. Summary of the Invention

[0003] In order to solve the problems of insufficient planing stability, poor splash performance in waves and large water load of existing amphibious aircraft multi-bilge line hulls, the present invention provides an amphibious aircraft with an obliquely raised front body and a multi-bilge line hull, which adopts a design of a raised front body keel line, splash suppression strips and retractable water flaps.

[0004] The technical solution of the present invention: A multi-bilge hull with an obliquely rising forebody for an amphibious aircraft is provided. The multi-bilge hull has three bilge lines arranged on the hull, namely an upper bilge line 2, a mid-bilge line 3, and a lower bilge line 4. The upper bilge line 2, the mid-bilge line 3, and the lower bilge line 4 divide the multi-bilge hull 1 into an upper hull 5, a mid-hull 6, and a lower hull 7. The multi-bilge hull 1 adopts an obliquely rising forebody keel line 8; Splash suppression strips 12 are arranged outside the upper bilge line 2 and the mid-bilge line 3 .

[0005] Further, The inclined angle of the inclined front keel line 8 is 2°±0.2°.

[0006] Further, The width of the splash suppression strip 12 is 5%±0.5% of the width of the multi-bilge hull 1, the angle between the splash suppression strip 12 and the horizontal line is 5°±1°, the splash suppression strip 12 is arranged from the bow point to the propeller rotation plane, and a retractable water flap 13 is arranged at the stern of the lower hull 7.

[0007] Further, The ratio of the length of the multi-bilge hull 1 to the bilge width of the multi-bilge hull 1 is greater than 10.

[0008] Further, The cross section of the intersection of the lower bilge line 4 and the forebody keel line 8 divides the multi-bilge hull 1 into a forebody 9 and an aftbody 10; The length of the rear body 10 is greater than that of the front body 9 .

[0009] Further, The keel line of the rear body has an oblique rising angle of 6°~8°.

[0010] Further, The multi-bilge hull 1 adopts an obliquely rising forebody keel line 8, increases the height of the forebody keel line 8, reduces the distance between the forebody keel line 8 and the upper bilge line 2, reduces the displacement volume of the multi-bilge hull 1, reduces the buoyancy of the bow area 11 of the multi-bilge hull 1, reduces the increase in the nose-up restoring moment, increases the decrease in the longitudinal inclination angle of the multi-bilge hull 1, reduces the longitudinal inclination angle of the multi-bilge hull 1 under the same nose-down moment, thereby reducing the stable planing longitudinal inclination angle before the front end of the bow area 11 touches the water, reduces the lower stability boundary, and improves the planing stability of the multi-bilge hull 1.

[0011] Further, The splash generated by the multi-bilge line hull 1 is a whisker-shaped splash, and the splashing area is the stagnation line of the upper hull 5 and the middle hull 6. Splash suppression strips 12 are arranged on the outside of the upper bilge line 2 and the middle bilge line 3 to deflect the whisker-shaped splash downward and away from the multi-bilge line hull 1, thereby suppressing the splashing of the multi-bilge line hull 1.

[0012] Further, The bottom of the lower hull 7 is horizontal, and the water load of the lower hull 7 is relatively large. Two retractable water flaps 13 are arranged on the stern of the lower hull 7 and opened downward to reduce the water load of the hull.

[0013] The technical solution of the present invention adopts a multi-bilge hull of an amphibious aircraft with an inclined forebody, which adopts a design of a raised forebody keel line, splash suppression strips, water flaps, a large aspect ratio and a long rear body. The raised forebody keel line lowers the lower stability boundary, improves the gliding stability of the multi-bilge hull, and meets the requirements of gliding stability on the water surface; the splash suppression strips suppress splashes in waves and prevent splashes from impacting propellers and flaps, thereby achieving a splash suppression effect and meeting the splash performance requirements for take-off and landing in waves; the water flaps reduce the water load of the hull and can reduce the weight of the aircraft structure; the large aspect ratio and long rear body design reduce wave motion response, which can further enhance the wave resistance of the amphibious aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A side view of a multi-bilge hull with an obliquely raised front body (water flaps not deployed) of an amphibious aircraft provided in an embodiment of the present invention; Figure 2 A side view of an amphibious aircraft with a multi-bilge hull with an obliquely raised front body (with flaps open) provided in an embodiment of the present invention; Figure 3 A front view of a multi-bilge hull with an obliquely rising front body of an amphibious aircraft provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0016] At present, the multi-bilge hull of amphibious aircraft has a large inclined angle. During take-off and landing, its vertical hydrodynamic force is mainly the buoyancy of the submerged area. When gliding at high speed, if a horizontal forebody keel line is used, the waterline surface is close to the bow, and the aerodynamic moment of the nose is increased by the downward aerodynamic rudder surface. At this time, the buoyancy of the bow area is significantly increased, and the lever arm from the center of gravity is longer, and the nose-up restoring moment generated is larger. Only a small change in the waterline surface is needed to balance the aerodynamic moment of the nose. In this way, the longitudinal inclination angle of the multi-bilge hull decreases less. If the nose-down moment continues to increase, the longitudinal inclination angle of the multi-bilge hull slowly decreases, and the draft of the bow area gradually increases; and the front end of the bow area is tapering, here The buoyancy generated is small, and the forebody keel line at the front end of the bow area is convex. When gliding at high speed, the forebody keel line here touches the water and easily generates hydrodynamic suction. The two work together to sharply reduce the increase in the nose-up restoring moment. At this time, the increase in the nose-up restoring moment generated by the bow area is less than the increase in the nose-down moment, that is, the nose-up restoring moment generated by the bow area is not enough to balance the nose-down moment, then head-down instability occurs, which results in a higher lower stability boundary and insufficient gliding stability, which directly affects the take-off and landing safety of amphibious aircraft.

[0017] Furthermore, the multi-bilge hull's large deadrise angle generates a significant amount of whisker-like spray from the bow during takeoff and landing. However, the narrow width and radius of the bilges limit the effectiveness of suppressing this spray. This is especially true in waves, where the spray impacts the propeller and the cockpit windshield, potentially damaging it and interfering with the pilot's flight. This directly impacts the safety of amphibious aircraft takeoff and landing. The multi-bilge hull's horizontal lower hull and low deadrise angle create significant water loads on the lower hull during landing. To ensure the multi-bilge hull can withstand these heavy water loads, it must be reinforced, increasing the aircraft's structural weight and reducing its payload.

[0018] To this end, it is necessary to lower the lower stability boundary, suppress hull splashing and reduce water load, improve the gliding stability and splashing performance of amphibious aircraft, and reduce the structural weight. The present invention provides an amphibious aircraft with a multi-bilge hull with an obliquely raised front body, which has good gliding stability, excellent splashing performance and low structural weight.

[0019] The present invention proposes a multi-bilge hull with an obliquely rising front body of an amphibious aircraft, such as Figure 1 and Figure 2 As shown, the design adopts a rising forebody keel line, a large deadrise angle, multiple bilge lines, a splash suppression strip and a long afterbody. The multi-bilge line hull 1 is arranged with three bilge lines on the hull, namely the upper bilge line 2, the middle bilge line 3 and the lower bilge line 4, which divide the multi-bilge line hull 1 into an upper hull 5, a middle hull 6 and a lower hull 7; the cross section at the intersection of the lower bilge line 4 and the forebody keel line 8 divides the multi-bilge line hull 1 into a forebody 9 and an afterbody 10.

[0020] The multi-bilge hull 1 utilizes a skewed forebody keel line 8, increasing its height and reducing its distance from the upper bilge line 2. This reduces the displacement of the multi-bilge hull 1, reduces the buoyancy of the bow section 11, minimizes the increase in the nose-up restoring moment, and increases the decrease in the trim angle of the multi-bilge hull 1. This reduces the trim angle of the multi-bilge hull 1 under the same nose-down moment. This reduces the stable planing trim angle of the bow section 11 before the front end of the bow section 11 strikes the water, lowers the lower stability margin, and improves the planing stability of the multi-bilge hull 1. The skew angle of the forebody keel line 8 should not be too large, as this will reduce the buoyancy of the bow section, resulting in excessive pitch amplitude during low-speed wave takeoff and landing, directly affecting the wave-resistance capability of amphibious aircraft. A skew angle of approximately 2° for the forebody keel line 8, i.e., a forebody keel angle of approximately 2°, is generally recommended.

[0021] The splash generated by the multi-bilge hull 1 is mainly whisker-shaped splash, and the splashing area is mainly at the stagnation line of the upper hull 5 and the mid-hull 6. The bilge width and radius of the upper hull 5 and the mid-hull 6 are small, and their splash suppression effect is limited when taking off and landing in waves. Splash suppression strips 12 are arranged on the outside of the upper bilge line 2 and the mid-bilge line 3 to deflect the whisker-shaped splash downward and away from the multi-bilge hull 1. The width of the splash suppression strip 12 is about 5% of the width of the multi-bilge hull 1, and the angle between the splash suppression strip 12 and the horizontal line is about 5°. The splash suppression strip 12 extends from the bow point to the propeller rotation plane, thereby suppressing the splash of the multi-bilge hull 1.

[0022] The bottom of the lower hull 7 of the multi-bilge hull 1 is horizontal and the deadrise angle is small, which causes a large water load on the lower hull 7 during landing. Two retractable water flaps 13 are arranged on the left and right sides of the stern of the lower hull 7. They are opened downward at the same time during landing. The water flaps 13 touch the water before other parts of the multi-bilge hull 1, and they bear a large amount of water load. At the same time, as the water flaps 13 gradually enter the water, the speed of the amphibious aircraft decreases, and the water load borne by other parts of the multi-bilge hull 1 when they touch the water is reduced, so the weight of the aircraft structure can be reduced.

[0023] The multi-bilge hull 1 features a high aspect ratio—the ratio of its length to its width is greater than 10—to minimize pitch and roll motions. The upper bilge line 2, mid-bilge line 3, and lower bilge line 4 provide adequate ventilation for the multi-bilge hull 1, eliminating the need for steps. To minimize wave motion response, a long aft hull is employed, with the aft hull 10 longer than the fore hull 9. To enhance the upper stability margin, the aft hull keel angle 13 is set between 6° and 8°.

[0024] The technical solution of the present invention utilizes a raised forebody keel line to reduce the buoyancy of the bow area of a multi-bilge hull, minimize the increase in the nose-up restoring moment, and reduce the trim angle of the multi-bilge hull under the same nose-down moment. This reduces the stable gliding trim angle of the bow area before the front end touches the water, lowers the lower stability boundary, and improves the gliding stability of the multi-bilge hull. The splash suppression strips redirect whisker-like splashes, deflecting them downward along the strips and away from the multi-bilge hull, preventing them from impacting the propeller and flaps. This achieves a splash suppression effect and meets the splash performance requirements for takeoff and landing in waves. The water flaps touch the water before the rest of the multi-bilge hull, bearing a large amount of water load. As the water flaps gradually enter the water, the speed of the amphibious aircraft decreases, reducing the water load on the multi-bilge hull when it touches the water. In addition, the use of a large aspect ratio and long rear body design increases the contact points between the multi-bilge hull and the waves, which can further reduce the motion response during takeoff and landing on the water surface, thereby improving the wave resistance of amphibious aircraft.

Claims

1. A multi-bilge hull with an obliquely rising front body for an amphibious aircraft, characterized in that: The multi-bilge hull has three bilge lines arranged on the hull, namely an upper bilge line (2), a mid-bilge line (3) and a lower bilge line (4). The upper bilge line (2), the mid-bilge line (3) and the lower bilge line (4) divide the multi-bilge hull (1) into an upper hull (5), a mid-hull (6) and a lower hull (7). The multi-bilge hull (1) adopts an obliquely rising forebody keel line (8); Splash suppression strips (12) are arranged outside the upper bilge line (2) and the mid-bilge line (3).

2. The multi-bilge hull with an obliquely raised front body of an amphibious aircraft according to claim 1, characterized in that: The inclined angle of the inclined front keel line (8) is 2°±0.2°.

3. The multi-bilge hull with an obliquely raised front body of an amphibious aircraft according to claim 1, characterized in that: The width of the splash suppression strip (12) is 5%±0.5% of the width of the multi-bilge hull (1), the angle between the splash suppression strip (12) and the horizontal line is 5°±1°, the splash suppression strip (12) is arranged from the bow point to the propeller rotation plane, and a retractable water flap (13) is arranged at the stern of the lower hull (7).

4. The multi-bilge hull with an obliquely raised front body of an amphibious aircraft according to claim 1, characterized in that: The ratio of the length of the multi-bilge hull (1) to the bilge breadth of the multi-bilge hull (1) is greater than 10.

5. The multi-bilge hull with an obliquely raised front body of an amphibious aircraft according to claim 1, characterized in that: The cross section at the intersection of the lower bilge line (4) and the forebody keel line (8) divides the multi-bilge hull (1) into the forebody (9) and the afterbody (10); The length of the rear body (10) is greater than the length of the front body (9).

6. The multi-bilge hull with an obliquely raised front body of an amphibious aircraft according to claim 5, characterized in that: The keel line of the rear body has an oblique rising angle of 6°~8°.

7. The multi-bilge hull with an obliquely raised front body of an amphibious aircraft according to claim 2, characterized in that: The multi-bilge hull (1) adopts an obliquely raised forebody keel line (8), increases the height of the forebody keel line (8), reduces the distance between the forebody keel line (8) and the upper bilge line (2), reduces the displacement volume of the multi-bilge hull (1), reduces the buoyancy of the bow area (11) of the multi-bilge hull (1), reduces the increase in the head-up restoring moment, increases the reduction in the longitudinal inclination angle of the multi-bilge hull (1), reduces the longitudinal inclination angle of the multi-bilge hull (1) under the same head-down moment, thereby reducing the stable planing longitudinal inclination angle of the bow area (11) before the front end touches the water, reduces the lower stability boundary, and improves the planing stability of the multi-bilge hull (1).

8. The multi-bilge hull with an obliquely raised front body of an amphibious aircraft according to claim 3, characterized in that: The splash generated by the multi-bilge line hull (1) is a whisker-shaped splash, and the splashing area is the stagnation line of the upper hull (5) and the middle hull (6). Splash suppression strips (12) are arranged on the outside of the upper bilge line (2) and the middle bilge line (3) to turn the whisker-shaped splash downward and away from the multi-bilge line hull (1), thereby suppressing the splash of the multi-bilge line hull (1).

9. The multi-bilge hull with an obliquely raised front body of an amphibious aircraft according to claim 3, characterized in that: The bottom of the lower hull (7) is horizontal, and the water load of the lower hull (7) is relatively large. Two retractable water flaps (13) are arranged on the stern of the lower hull (7) and are opened downward to reduce the water load of the hull.

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