CN111776131B

CN111776131B - Superspeed water surface navigation ware based on syllogic supercavitation hydrofoil

Info

Publication number: CN111776131B
Application number: CN202010484495.5A
Authority: CN
Inventors: 王一伟; 黄仁芳; 支玉昌; 杜特专; 王静竹; 黄晨光
Original assignee: Institute of Mechanics of CAS
Current assignee: Institute of Mechanics of CAS
Priority date: 2020-06-01
Filing date: 2020-06-01
Publication date: 2021-08-31
Anticipated expiration: 2040-06-01
Also published as: CN111776131A

Abstract

The invention provides an ultra-high-speed water surface vehicle based on a three-section type ultra-cavity hydrofoil, which comprises a ship body, wherein a front hydrofoil and a rear hydrofoil are respectively arranged on two sides of the ship body; the span length of the flat wing of the rear hydrofoil is larger than that of the flat wing of the front hydrofoil; two jet engines are arranged on the ship body between the two rear hydrofoils side by side, and a semi-submerged paddle is arranged at the tail of the ship body. The combined propulsion mode of the semi-submerged propeller and the turbojet engine is adopted, so that strong thrust can be provided for the water surface aircraft under different working requirements, the resistance of the front hydrofoil and the rear hydrofoil can be reduced by adopting the supercavitation wing type, the three-section hydrofoil structure is favorable for reducing the sensitivity of the navigation speed, and the navigation stability is effectively improved.

Description

Superspeed water surface navigation ware based on syllogic supercavitation hydrofoil

Technical Field

The invention relates to the field of ships, in particular to an ultrahigh-speed water surface vehicle which takes a novel supercavitation airfoil profile as a lifting component and is based on a three-section supercavitation hydrofoil.

Background

According to the ship resistance law, the viscous resistance of the ship is in direct proportion to the square of the navigational speed, and the wave making resistance is in direct proportion to the sixth power of the navigational speed. This means that the higher the speed, the greater the resistance that needs to be overcome. Furthermore, the sailing resistance is closely related to the wet surface area of the vessel submerged below the water surface. The water surface aircraft lifts the ship body through the lift force generated by the hydrofoil in the sailing process, reduces the wet surface area, further reduces the viscous resistance and the wave-making resistance, and has unique advantages in aspects of rapidity, seaworthiness and the like.

At present, two technical approaches of increasing the propelling power and reducing the sailing resistance are generally available in the aspect of improving the sailing speed.

The conventional power propulsion device of the ship generally mainly adopts a propeller or water jet propulsion, and when the navigational speed exceeds 50 knots, the conventional power propulsion device generates a cavitation phenomenon, thereby reducing the thrust.

The supercavity drag reduction technology is characterized in that supercavity is utilized to wrap an object, the object is not in direct contact with water any more, and the resistance borne by the object is reduced by about 90% compared with a full-wet state. Patent CN 201210319158.6 provides an ultra-high speed supercavitation twin-hull water surface vehicle, which uses a ventilation device to inflate the hydrofoil and the front transverse edges of the bottom surfaces of two ships, so that the lifting surface of the hydrofoil and the bottom surfaces of two ship bodies form a very thin air film covering, i.e. the hydrofoil and the two ship bottoms form supercavitation, thereby achieving the purpose of reducing viscous resistance.

Patent ZL201710608120.3 has announced a novel supercavitation surface of water high speed boat, produces the supercavitation of stealthy body under the parcel through the cavitation generator to reach the effect of drag reduction, and introduce turbojet as the driving system of yacht, further promote the navigational speed.

However, the scheme for realizing the supercavitation drag reduction adopts manual ventilation, and additional auxiliary equipment such as a cavitation generator and an air compressor is required, so that the mechanism is complex, and the cost and redundant equipment are increased.

Disclosure of Invention

The invention aims to provide an ultra-high speed water surface vehicle which takes a novel supercavitation airfoil profile as a lifting component and is based on a three-section type supercavitation hydrofoil.

The invention provides an ultrahigh-speed water surface vehicle based on a three-section type supercavitation hydrofoil, which comprises a ship body, wherein two symmetrical front hydrofoils are respectively arranged on two sides of the front part of the ship body, two symmetrical rear hydrofoils are respectively arranged on two sides of the rear part of the ship body, each front hydrofoil comprises a horizontal flat wing, an inclined wing and a vertical wing, the horizontal flat wing is connected with the ship body at one end, the inclined wing is connected with the other end of the flat wing through one end and inclines towards the direction of the ship body, the vertical wing is connected with the other end of the inclined wing and is vertical to the horizontal plane, the other end of the inclined wing extends to the position below the ship bottom of the ship body, the length of the vertical wing is one fourth of the length of the inclined wing, and the inclined wing and the vertical wing are supercavitation wing profiles;

the rear hydrofoil and the front hydrofoil have the same structure, but the span length of the flat wing of the rear hydrofoil is greater than that of the front hydrofoil;

two jet engines are arranged on the ship body between the two rear hydrofoils side by side, and a semi-submerged paddle is arranged at the tail of the ship body.

In one embodiment of the invention, the supercavity airfoil comprises a suction surface and a force-bearing surface which are connected with each other at one end and are open at the other end, and a contraction end which is connected with the opening ends of the suction surface and the force-bearing surface and forms an arc contraction, wherein the suction surface and the force-bearing surface are arc surfaces which are arc-convex from a contact end to the opening end respectively, the suction surface determines the profile by a numerical simulation method, the force-bearing surface determines the profile by a Johnson three-order design method, the contraction end determines the profile by a NACA design method, and further determines the lengths of the suction surface and the force-bearing surface, the angle of an included angle between the suction surface and the force-bearing surface, and the length of the contraction end.

In one embodiment of the invention, the flat wing is connected at an upper edge of the ship body, and the ship body is a round bilge boat type.

In one embodiment of the present invention, the oblique wing and the flat wing are connected by a folded plate having two sides forming a fixed included angle, bolt holes are formed on two sides of the folded plate, the same bolt holes are formed in the connecting end of the flat wing and the oblique wing, the three are fixed together by bolts passing through the bolt holes, and the included angle of the folded plate is 45 degrees, so that the included angle between the oblique wing and the flat wing after fixing is maintained at 45 degrees.

In one embodiment of the present invention, a plurality of bolt holes are provided in the oblique wing, and the adjustment of the extension length of the oblique wing can be achieved by fixing the oblique wing to the flap through different bolt holes.

In one embodiment of the invention, the front hydrofoil and the rear hydrofoil are both in a duck configuration, and the loads are equal.

In one embodiment of the invention, the oblique wing comprises a rectangular section and a contracted section, the length of the rectangular section is 2.5 chord lengths when the width of the rectangular section is equal to the chord length, the width of one end of the contracted section is equal to the chord length, the width of the other end of the contracted section is equal to one third of the chord length, the two ends are connected within the distance of 1.2 chord lengths, and the inclination angle of one side is larger than that of the other side.

In one embodiment of the present invention, one end of the vertical wing is connected to the contraction section of the oblique wing, and the other end is contracted into an arc-shaped protrusion within a distance of 0.3 chord lengths.

In one embodiment of the invention, the distance between the vertical wings of the two front hydrofoils is equal to the chord length, and the distance between the vertical wings of the two rear hydrofoils is 3.5 chord lengths.

In one embodiment of the invention, the front hydrofoil is attached to the hull at a distance one third of the front end, and the rear hydrofoil is aligned with the aft end of the hull and spaced 10 chord lengths from the front hydrofoil.

The combined propulsion mode of the semi-submerged propeller and the turbojet engine is adopted, so that strong thrust can be provided for the surface vehicle under different working requirements, and the low-speed and ultrahigh-speed sailing effects of the surface vehicle are realized. The semi-submerged propeller sucks air while the paddle continuously passes through a water-air interface, so that the natural cavitation phenomenon is effectively avoided. In addition, the turbojet engine is used as a power propulsion device of the water part, and has the advantages of large thrust, small mass and good speed performance.

The supercavitation airfoil profile not only can play the effect of drag reduction under the supercavitation state, but also can keep higher lift and lower resistance under the complete wetting state, and overcomes the defect that the traditional cut-off type supercavitation hydrofoil has low working efficiency under the complete wetting state.

The lift force required by the surface vehicle at low speed is provided by the ship body, the flat wing, the oblique wing and the vertical wing of the front hydrofoil and the rear hydrofoil; the water surface aircraft leaves the water surface at high speed, and the lift force required by the water surface aircraft is provided by the inclined wings and the vertical wings of the front hydrofoil and the rear hydrofoil. The design length and chord length of the front hydrofoil and the rear hydrofoil are designed according to the working requirement and the working strength to meet the requirement of the parameters.

The three-section structure of the front hydrofoil and the rear hydrofoil can adaptively adjust the lift force according to different sailing speeds, thereby being beneficial to reducing the sensitivity of the aircraft to the speed and improving the stability of sailing.

Drawings

FIG. 1 is a schematic side view of a surface vehicle according to an embodiment of the invention;

FIG. 2 is a right side view of the surface craft of FIG. 1;

FIG. 3 is a schematic representation of a section of a supercavitation airfoil according to one embodiment of the present invention;

FIG. 4 is a schematic view of an oblique wing structure according to an embodiment of the present invention;

fig. 5 is a schematic view of a flap construction according to an embodiment of the present invention.

Detailed Description

The detailed structure and implementation process of the present solution are described in detail below with reference to specific embodiments and the accompanying drawings.

As shown in fig. 1 and 2, in an embodiment of the present invention, an ultra-high speed water surface vehicle 100 based on a three-section type supercavitation hydrofoil is disclosed, which includes a ship body 1 of a round bilge boat shape, two symmetrical front hydrofoils 2 are respectively installed at two sides of a front portion of the ship body 1, and the front hydrofoils 2 are connected to the ship body 1 at a position one third away from the front end and close to an upper edge of the ship body 1; the front hydrofoil 2 comprises a horizontal flat wing 21 with one end connected with the ship body 1, an inclined wing 22 which is connected with the other end of the flat wing 21 through one end and inclines towards the ship body 1, and a vertical wing 23 which is connected with the other end of the inclined wing 22 and is vertical to the horizontal plane, wherein one end of the inclined wing 22 connected with the vertical wing 23 extends to the lower part of the ship bottom of the ship body 1, and the length of the vertical wing 23 is one fourth of the length of the inclined wing 22.

Two symmetrical rear hydrofoils 3 are respectively installed on two sides of the rear part of the ship body 1, and the rear hydrofoils 3 are aligned with the tail end of the ship body 1 and are located on the upper edge of the ship body 1. The rear hydrofoil 3 and the front hydrofoil 2 have the same structure, and the difference is that the span length of the flat wing 21 of the rear hydrofoil 3 is greater than that of the flat wing 21 of the front hydrofoil 2, and the oblique wing 22 of the rear hydrofoil 3 is parallel to the oblique wing 22 of the front hydrofoil 2 and has the same inclination angle. The structure of the front hydrofoil 2 is explained in the following description.

Two jet engines 4 are mounted side by side on the ship body 1 between the two rear hydrofoils 3, and a semi-submerged paddle 5 is mounted at the tail of the ship body 1.

In the present embodiment, the front hydrofoil 2 and the rear hydrofoil 3 are each arranged in a duck configuration such that the loads on the front hydrofoil 2 and the rear hydrofoil 3 are substantially equal, and the loads on the front hydrofoil 2 and the rear hydrofoil 3 are determined by the distances from the center of gravity of the ship body 1.

At low speed (lower than 100 knots), the lift required by the surface vehicle 100 is provided by the flat wing 21, the oblique wing 22 and the vertical wing 23 of the ship body 1, the front hydrofoil 2 and the rear hydrofoil 3; at a high speed (greater than the navigational speed of 100 knots), the surface vehicle 100 leaves the water surface, the lift force required by the surface vehicle 100 is provided by the oblique wings 22 and the vertical wings 23 of the front hydrofoil 2 and the rear hydrofoil 3, and the specific design lengths and chord lengths of the front hydrofoil 2 and the rear hydrofoil 3 are designed to meet the parameters of the conditions according to the working requirements and the working strength.

A combined power propulsion mode is formed by adopting a semi-submerged paddle 5 and a turbojet engine 4, wherein the semi-submerged paddle 5 is arranged in the middle of the tail part of the ship main body 1, and has the characteristics of small volume, high rotating speed and large thrust; the turbojet engines 4 are mounted on the upper portion of the tail end of the ship body 1, and are symmetrical to each other. When the speed of the vehicle is below 100kn, the surface vehicle 100 uses a semi-submersible 5 propulsion mode, and when the speed of the vehicle is above 100kn, the surface vehicle 100 uses a combined propulsion mode of the semi-submersible 5 and the turbojet 4.

By adopting a combined propulsion mode of the semi-submerged propellers 5 and the turbojet 4, strong thrust can be provided for the surface vehicle 100 under different working requirements, so that the low-speed and ultrahigh-speed sailing effects of the surface vehicle 100 are realized. The semi-submerged propeller 5 sucks air while the paddle continuously passes through a water-air interface, so that the natural cavitation phenomenon is effectively avoided. In addition, the turbojet 4, as a power propulsion device for the marine part, has the advantages of high thrust, low mass and good speed performance.

As shown in fig. 3, in one embodiment of the present invention, the oblique wings 22 and the vertical wings 23 of the front hydrofoil 2 and the rear hydrofoil 3 respectively adopt a supercavity wing type, which includes two suction surfaces 223 and force-bearing surfaces 224 that are opened at one end and the other end, and a contraction end 225 that is connected with the opening ends 227 of the suction surfaces 223 and the force-bearing surfaces 224 and forms an arc-shaped contraction, and the suction surfaces 223 and the force-bearing surfaces 224 are arc-shaped surfaces that are arc-shaped and convex from the contact ends 226 to the opening ends 227 respectively, wherein the suction surfaces 223 are contoured by a numerical simulation method in the prior art, the force-bearing surfaces 224 are contoured by a johnson three-step design method, and the contraction ends 225 are contoured by a NACA design method, so that the length of the combined rear suction surface 223 and the force-bearing surfaces 224, the angle between the two (i.e., 226), and the length of the contraction ends 225 can be determined.

Generally, the angle formed by the suction surface 223 and the force-bearing surface 224 is about 5 degrees, which can reduce the cross-sectional area as much as possible, while the length of the suction surface 223 and the force-bearing surface 224 is about three times as long as the length of the contraction end 225, which can quickly form super-vacuoles to reduce the resistance, and the angle of the contraction end 225 is about 30 degrees. The suction surface 223 may transition integrally to the end of the converging end 225 to form an upper top surface of the converging end 225, while the lower top surface of the converging end 225 is connected by a force-bearing surface 224 at the diverging end 227 along an arc to the end of the converging end 225 to form an inner concave surface.

The cavitation length formed by the supercavity airfoil of the structure is gradually shortened along the wing tip direction, which is caused by the increase of the number of local cavitations due to the increase of hydrostatic pressure. Compared with the straight wing structure in the prior art, the supercavitation hydrofoil formed by the inclined wing 22 and the vertical wing 23 reduces the resistance of the front hydrofoil 2 and the rear hydrofoil 3, and the vertical wing of the front hydrofoil and the rear hydrofoil is beneficial to reducing energy dissipation and reducing sailing resistance.

The thickness and chord length of the front hydrofoil 2 and the rear hydrofoil 3 are gradually reduced along the direction of the wing tip, secondary influence is generated on cavitation, vortex generation can be reduced, and meanwhile separation flow generated at the bottom of the straight wing in the prior art can not be generated.

In the embodiment, a novel supercavitation airfoil profile is adopted as a basic airfoil profile, and the design method combines the design methods of the traditional supercavitation airfoil profile and the common NACA airfoil profile: that is, the suction side 223 and the force-bearing side 224 are designed using conventional supercavitation airfoil design methods, while the contraction end 225 is designed using conventional NACA airfoil design methods. The hydrodynamic performance of the integral supercavitation airfoil profile can be evaluated according to specific working requirements through a numerical simulation method, and if the hydrodynamic performance does not meet the design requirements, modification optimization is carried out; and circulating the steps until specific design requirements are met.

At high speed (the speed of flight is greater than 100 knots), the suction surface 223 and the stress surface 224 of the supercavitation airfoil profile generate supercavitation as with the traditional supercavitation airfoil profile, and at low speed (the speed of flight is lower than 100 knots), the contraction end 225 of the supercavitation airfoil profile provides additional lift force for the front hydrofoil 2 and the rear hydrofoil 3 as with the conventional NACA airfoil profile, so that the working efficiency of the front hydrofoil 2 and the rear hydrofoil 3 can be improved. The supercavitation wing section in this scheme has synthesized the advantage of ordinary hydrofoil and traditional supercavitation hydrofoil, can have higher hydrodynamic force performance when low speed, can have higher hydrodynamic force performance when high speed again, has overcome among the prior art ordinary NACA hydrofoil can produce the vacuole when high speed, influences the problem of hydrofoil performance, has solved among the prior art supercavitation hydrofoil problem that work efficiency is low when low speed simultaneously.

As shown in fig. 4, in one embodiment of the present invention, the oblique wing 22 is composed of a rectangular section 221 and a contracted section 222, and one end of the rectangular section 221 is connected to the flat wing 21 and the other end is integrally connected to the contracted section 222. The width of the rectangular section 221 is taken as the chord length C, so the length of the rectangular section 221 is 2.5C, the width of one end of the contraction section 222 connected with the rectangular section 221 is equal to C, the width of the other end of the contraction section is equal to 0.3C, the two ends are connected within the distance of 1.2C, the inclination angle of one side is larger than that of the other side, and the whole structure is a trapezoidal spanwise structure.

One end of the vertical wing 23 is connected with the contraction section 222 of the inclined wing 22 and then is vertical to the water surface, the other end of the vertical wing is contracted into an arc-shaped bulge within a distance of 0.3C, and the heights of the vertical wings 23 of the front hydrofoil 2 and the rear hydrofoil 3 are the same.

The oblique wing 22 and the vertical wing 23 are integrally formed, and structurally divided into a three-stage structure consisting of a rectangular section 221, a contraction section 222 and the vertical wing 23.

In the present embodiment, the chord length c is the width (chord length) of the oblique wing 22, but in other embodiments, the chord length c may be selected from the widths of other members depending on the size of the ship body.

The above data corresponds to the shape and size of the surface vehicle 100 in the above embodiment, and in other embodiments, the data needs to be determined experimentally for each specific shape and size of the vessel body 1.

In the present embodiment, the oblique wing 22 and the vertical wing 23 are divided into three sections in the extending direction, and from the installation position, the chord length c of the rectangular section 221 is constant, and the contraction section 222 has a trapezoidal extending structure, and the chord length gradually decreases from c to 0.35 c; the vertical wing 23 is a sharp winglet perpendicular to the water surface, which can reduce the induced resistance.

The three-section design structure of the hydrofoil can meet the requirements of the surface vehicle 100 in different working states. Since the lift of the front hydrofoil 2 and the rear hydrofoil 3 is proportional to the square of the speed, the lift coefficient, and the wetted area, but the displacement of the ship body 1 remains unchanged, the total lift required to be generated by the front hydrofoil 2 and the rear hydrofoil 3 does not change.

The water surface vehicle 100 needs to have larger lift coefficient and larger wetting area of the front hydrofoil 2 and the rear hydrofoil 3 at low speed, so that the forward structure of the rectangular section 221 can increase the wetting area of the front hydrofoil 2 and the rear hydrofoil 3 to improve the lift of the front hydrofoil 2 and the rear hydrofoil 3; at high speed, the lift coefficient and the wetted area of the front hydrofoil 2 and the rear hydrofoil 3 are required to be small, and the contraction section 222 of the front hydrofoil 2 and the rear hydrofoil 3 is in a trapezoidal span-wise structure, so that the wetted area can be reduced. Meanwhile, at a high speed, the front hydrofoil 2 and the rear hydrofoil 3 are quite sensitive to the speed, so that the instability of the water surface vehicle 100 is easily caused, and the trapezoidal-shaped contraction section 222 and the vertical wing 23 vertical to the water surface are designed to help to reduce the navigation speed sensitivity and effectively improve the navigation stability. The length and width of the front hydrofoil 2 and the rear hydrofoil 3 meet the requirements of the designed water surface vehicle 100 on both lift and structural strength of the water surface vehicle 100 at the designed speed.

The spanwise structure of the front hydrofoil 2 and the rear hydrofoil 3 of the present embodiment can satisfy the requirements of different operating states compared to the straight hydrofoil of the prior art. At low navigational speed, the requirements on the lift coefficient and the wetted area of the front hydrofoil 2 and the rear hydrofoil 3 are high, and at the moment, the supercavitation hydrofoil structures of the oblique wing 22 and the vertical wing 23 are in a completely wet state, so that the lift of the hydrofoil is improved by adaptively adjusting the wetted area to enable the water-air interface to be positioned at the rectangular section 221. At high navigational speeds, the lift coefficient requirements for the front hydrofoil 2 and the rear hydrofoil 3 are low, and sufficient lift can be ensured by adaptively adjusting the wetted area so that the water-air interface is positioned at the position of the contraction section 222. In addition, the trapezoidal-shaped contraction section 222 and the vertical wing 23 vertical to the water surface help to reduce the sensitivity of the hydrofoil to the navigation speed, and effectively improve the navigation stability.

Under the structure, the interval distance between the vertical wings 23 of the two front hydrofoils 2 is equal to the chord length C, and the distance between the vertical wings 23 of the two rear hydrofoils 3 is 3.5C.

The front hydrofoil 2 is connected to the ship body 1 at a position one third away from the front end, and the rear hydrofoil 3 is aligned with the tail end of the ship body 1, calculated by the overall length of the ship body 1 being 18 c. The spacing between the front hydrofoil 2 and the rear hydrofoil 3 is around 10 c. The distance between the two jet engines 4 is about 3 c.

As shown in fig. 5, in one embodiment of the present invention, the inclined wing 22 is connected to the flat wing 21 by a flap 6 having two sides forming a fixed angle, bolt holes are formed on two sides of the flap 6, and the same bolt holes are formed in the connecting ends of the flat wing 21 and the inclined wing 22, respectively, and the three are fixed together by bolts passing through the bolt holes.

One side of the folded plate 6 connected with the flat wing 21 is a straight edge 61, and the other side is a folded edge 62 forming an included angle of 45 degrees relative to the straight edge 61, so that the included angle between the fixed oblique wing 22 and the flat wing 21 is kept at 45 degrees. The present embodiment facilitates adjustment of the angle of inclination of the tilt wing 22 while facilitating installation and removal.

Further, a plurality of bolt holes may be formed in the oblique wing 22 in the longitudinal direction, and the oblique wing 22 may be fixed to the flap 6 through different bolt holes, so that the extension length of the oblique wing 22 with respect to the flat wing 21 may be adjusted. The structure enables the oblique wings 22 to adjust the cutting positions relative to the water surface according to the size and the navigation parameters of the ship body 1, and improves the lift force of the ship body 1.

The maximum speed of the surface vehicle 100 in the scheme can reach 120-section ultrahigh speed, and the stable navigation attitude can be kept. The water surface vehicle 100 folds hydrofoils at low speed and sails by depending on a ship body, the ship body is of a round bilge boat type, the frictional resistance is smaller and smaller than that of a channel planing boat, meanwhile, the ship body is completely supported out of the water surface by depending on the front hydrofoils 2 and the rear hydrofoils 3 at high speed, the resistance borne by the front hydrofoils 2 and the rear hydrofoils 3 is the main component of the resistance of the whole ship, the wet surface area of the front hydrofoils 2 and the rear hydrofoils 3 is smaller, so that the resistance of the water surface vehicle 100 at high speed is still small, and sufficient thrust can be provided for the whole ship body by the combined propulsion of the semi-submerged paddles 5 and the turbojet engine 4, so that the highest sailing speed of the water surface vehicle 100 can reach 120 knots and is far greater than the highest sailing 60 knots of the current channel planing boat. Therefore, the ultra-high speed surface vehicle 100 based on the three-section type supercavitation hydrofoils provided by the invention has a remarkable advantage in terms of rapidity compared with the conventional planing boat.

The following describes, in a specific embodiment, a process of the force-bearing surface 224 implemented by the johnson third-order design method:

the stress surface 224 of the supercavitation airfoil profile is designed by adopting a Johnson theory, the theory is based on a conformal mapping method, is linearized and popularized by Tulin and Burkart for the first time, and the flow in the complex plane (Z) of the supercavitation airfoil profile is converted into the complex plane of the completely wet airfoil profile

Internal flow:

according to the thin profile theory, the potential flow around the fully wetted profile is represented by a continuous vorticity distribution, and the typical vorticity distribution Ω (x) for a fully wetted foil is represented by a sinusoidal series:

the glaue coordinate transformation performs a transformation of the coordinate x (in the direction of the airfoil chord length) and the angular coordinate θ:

the lift coefficient of a supercavitation hydrofoil results equal to the pitching moment coefficient of a fully wetted hydrofoil due to conformal transformation:

similarly, the drag coefficient of a supercavitation hydrofoil is related to the lift coefficient of a fully wetted hydrofoil as follows:

in order to eliminate A in (2) and (4), (5)₀Firstly, finding an optimal stress surface on the premise of a zero-degree attack angle and a proper reference line (instead of a chord line); second, the value of the coefficient that maximizes the hydrofoil efficiency, defined as the ratio of the lift coefficient (4) to the (inviscid) drag (5), is sought, i.e.:

finding the maximum efficiency equals finding [ -A [ ]₂/A₁]Is measured. The maximum value is searched for, and the physical condition that the vorticity at any point of the airfoil surface (surface) is positive is required to be met, so that cavitation bubbles are prevented from being generated on the surface. In fact, in this asymptotic approach, the dynamic pressure of the surface is related toThe circulation is directly proportional and the cavitation index is zero.

Different maximum efficiency values can be found according to the number of terms retained in the vorticity distribution expression in equation (2). Tulin-Burkart retains only the first two terms of the series, for this family of profiles, the maximum ideal efficiency (at 0 attack angle) is:

three terms of Johnson are retained at A₃In equation (2), this results in 1.44 times efficiency (equal to 0 at the ideal angle of attack), in fact:

the shape of the stress surface is corresponding to the three solutions as follows

In one embodiment of the present invention, the step of determining the suction surface using a numerical simulation method is as follows:

step 100, the maximum thickness is formed at the opening end formed by the suction surface and the stress surface, and the value of the opening end is 0.1 times of the length of the suction surface, so that the positions of the front edge and the rear edge of the suction surface are determined, parameterized curves of the front edge and the rear edge are established through software, and a two-dimensional hydrofoil model only comprising the suction surface and the stress surface is established;

the software here may be CAD software.

Step 110: establishing a two-dimensional flow field in a cuboid region shape which surrounds the novel supercavitation airfoil section, wherein the section is in the two-dimensional flow field, the front edge and the tail edge of the section are respectively 5 times of chord length and 10 times of chord length away from the adjacent side edge, and the upper edge and the lower edge of the opening end are respectively 0.6 times of chord length away from the upper surface and the lower surface of the two-dimensional flow field;

step 120, performing grid division in the two-dimensional watershed by adopting a cutting body grid, and increasing grid density for a front edge, a tail edge and a trail area of the cross section;

step 130, initializing the calculation parameters in a computational fluid dynamics solver: the inlet of the flow field is given with the incoming flow speed of the fluid, the outlet is given with the average static pressure, and the boundary conditions of the non-slip smooth wall surface are given to the surface of the hydrofoil and the boundary of the flow field area; based on the boundary conditions and the initial conditions, carrying out hydrofoil cavitation numerical calculation by using a computational fluid dynamics solver and a cavitation solver to obtain the velocity, pressure and cavitation distribution conditions of a flow field area and the hydrodynamic performance of the hydrofoil;

step 140, changing the curve parameters of the suction surface, and repeating steps 100 to 130 to determine the profile of the suction surface under the optimal solution of the curve shape.

In one embodiment of the present invention, the steps for designing the contraction end by the NACA design method are as follows:

step 200, setting the length of a contraction end to be 0.36 times of that of a suction surface, determining the positions of a front edge and a rear edge of the sharp tail wing, establishing parameterized curves of the front edge and the rear edge through software, and generating a two-dimensional hydrofoil model with the suction surface, the stress surface and the sharp tail wing;

step 210, establishing a two-dimensional flow field in a shape of a cuboid region surrounding the novel supercavity airfoil section, wherein the section is in the two-dimensional flow field, the front edge and the tail edge of the section are respectively 5 times chord length and 10 times chord length away from the adjacent side edge, and the upper edge and the lower edge of the opening end are respectively 0.6 times chord length away from the upper surface and the lower surface of the two-dimensional flow field;

step 220, performing grid division in the two-dimensional watershed by adopting a cutting body grid, and increasing grid density for a front edge, a tail edge and a trail area of the cross section;

step 230, initializing the calculation parameters in the computational fluid dynamics solver: the inlet of the flow field is given with the incoming flow speed of the fluid, the outlet is given with the average static pressure, and the boundary conditions of the non-slip smooth wall surface are given to the surface of the hydrofoil and the boundary of the flow field area; based on the boundary conditions and the initial conditions, carrying out hydrofoil cavitation numerical calculation by using a computational fluid dynamics solver and a cavitation solver to obtain the velocity, pressure and cavitation distribution conditions of a flow field area and the hydrodynamic performance of the hydrofoil;

step 240, changing the parameters of the contraction end, and then repeating steps 200 to 230 to find the optimal solution of the contraction end.

Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.

Claims

1. An ultra-high speed water surface vehicle based on a three-section type ultra-cavitation hydrofoil comprises a ship body and is characterized in that two symmetrical front hydrofoils are respectively arranged on two sides of the front part of the ship body, two symmetrical rear hydrofoils are respectively arranged on two sides of the rear part of the ship body, each front hydrofoil comprises a horizontal flat wing, an inclined wing and a vertical wing, wherein one end of each horizontal flat wing is connected with the ship body, the inclined wing is connected with the other end of each flat wing through one end of each horizontal flat wing and inclines towards the direction of the ship body, the vertical wing is connected with the other end of each inclined wing and is perpendicular to the horizontal plane, the other end of each inclined wing extends to the position below the ship bottom of the ship body, the length of each vertical wing is one quarter of the length of each inclined wing, and the inclined wings and the vertical wings are ultra-cavitation wing profiles;

the oblique wing comprises a rectangular section and a contraction section, the width of the rectangular section is equal to the chord length, the length of the rectangular section is 2.5 chord lengths, the width of one end of the contraction section is equal to the chord length, the width of the other end of the contraction section is equal to one third of the chord length, the two ends are connected within the distance of 1.2 chord lengths, and the inclination angle of one side is larger than that of the other side;

the distance between the vertical wings of the two front hydrofoils is equal to the chord length, and the distance between the vertical wings of the two rear hydrofoils is 3.5 chord lengths;

two jet engines are arranged on the ship main body between the two rear hydrofoils side by side, and a semi-submerged paddle is arranged at the tail part of the ship main body;

the super-cavity wing type comprises a suction surface and a stress surface, wherein one end of the suction surface is connected with the other end of the stress surface, the other end of the suction surface is opened, the stress surface is connected with the opening end of the suction surface and the opening end of the stress surface to form an arc-shaped contracted contraction end, the suction surface and the stress surface are arc-shaped surfaces protruding towards the opening end from a contact end respectively, the suction surface determines the profile through a numerical simulation method, the stress surface determines the profile through a Johnson three-step design method, the contraction end determines the profile through an NACA (network application programming interface) design method, and then the lengths of the suction surface and the stress surface, the angle of an included angle between the suction surface and the stress surface and the length of the contraction end are determined;

the suction surface with the contained angle size that the stress surface formed is at 5 degrees, the suction surface with the length of stress surface is the triple of shrink end length, the contained angle of shrink end is 30 degrees, the suction surface wholly passes through the extreme point department of shrink end, in order to form the last top surface of shrink end, the lower top surface of shrink end is connected to by opening end department stress surface border arc the extreme point of shrink end forms an interior concave surface.

2. The surface vehicle of claim 1,

the flat wing is connected to the upper edge of the ship body, and the ship body is of a round bilge boat shape.

3. The surface vehicle of claim 1,

the oblique wings and the flat wings are connected through a folded plate with a fixed included angle formed on two sides, bolt holes are formed in two sides of the folded plate, the same bolt holes are formed in the connecting ends of the flat wings and the oblique wings, the oblique wings and the flat wings are fixed together through bolts penetrating through the bolt holes, the included angle of the folded plate is 45 degrees, and the included angle between the fixed oblique wings and the flat wings is kept at 45 degrees.

4. The surface vehicle of claim 3,

the inclined wing is provided with a plurality of bolt holes, and the bolt holes are fixed with the folded plate through different bolt holes, so that the extending length of the inclined wing can be adjusted.

5. The surface vehicle of claim 1,

the front hydrofoil and the rear hydrofoil are arranged in a duck shape, and the loads of the front hydrofoil and the rear hydrofoil are equal.

6. The surface vehicle of claim 1,

one end of the vertical wing is connected with the contraction section of the inclined wing, and the other end of the vertical wing is contracted into an arc-shaped bulge within 0.3 chord length distance.

7. The surface vehicle of claim 1,

the front hydrofoil is connected to the ship body and is one third away from the front end, and the rear hydrofoil is aligned to the tail end of the ship body and is 10 chord lengths away from the front hydrofoil.