Hydrofoil ship with novel supercavitation wing profiles
阅读说明：本技术 一种具备新型超空泡翼型的水翼船 (Hydrofoil ship with novel supercavitation wing profiles ) 是由 王一伟 黄仁芳 支玉昌 杜特专 王静竹 黄晨光 于 2020-06-01 设计创作，主要内容包括：本发明提供一种具备新型超空泡水翼的水翼船,包括船舶主体,安装在船舶主体前段的前水翼,及设置在船尾的尾水翼,前水翼包括依次连接的平翼,和新型超空泡翼型的斜翼、折翼；尾水翼包括垂直安装的NACA翼型的垂翼,以及水平固定在垂翼下端部的新型超空泡翼型的短翼；新型超空泡翼型,包括两块一端相接另一端张开的吸力面和受力面,以及与张开端连接的收缩端,吸力面、受力面和收缩分别利用数值模拟方法、约翰逊三阶设计方法和NACA设计方法确定轮廓。本发明的水翼船采用具备新型超空泡翼型的气水动一体化组合型前水翼和深浸式的尾翼,使该水翼船在高低速航行时都具有较好的快速性和稳定性,达到工作适应性强、结构简单、工作可靠、节约制造成本的效果。(The invention provides a hydrofoil ship with a novel supercavitation hydrofoil, which comprises a ship main body, a front hydrofoil arranged at the front section of the ship main body and a tail hydrofoil arranged at the stern, wherein the front hydrofoil comprises a flat wing, an inclined wing and a folding wing of the novel supercavitation wing type which are connected in sequence; the tail hydrofoil comprises a vertical wing of an NACA airfoil profile which is vertically arranged and a short wing of a novel supercavitation airfoil profile which is horizontally fixed at the lower end part of the vertical wing; the novel supercavity wing section 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 stress surface is opened, and a contraction end is connected with the opening end, and the suction surface, the stress surface and the contraction are respectively determined by a numerical simulation method, a Johnson three-order design method and a NACA design method. The hydrofoil ship provided by the invention adopts the air-hydraulic integrated combined front hydrofoil with the novel supercavitation wing profile and the deep-immersed empennage, so that the hydrofoil ship has better rapidity and stability during high-speed and low-speed navigation, and the effects of strong working adaptability, simple structure, reliable work and manufacturing cost saving are achieved.)
1. A hydrofoil ship with novel supercavitation wing profiles comprises a ship main body, two symmetrical front hydrofoils arranged at the front section of the ship main body and a tail hydrofoil arranged at the stern,
the front hydrofoil comprises a horizontal flat wing, an inclined wing and a flap, wherein the horizontal flat wing, the inclined wing and the flap are sequentially connected, the inclined wing is connected with one end, away from the ship body, of the flat wing and inclines downwards, the flap is connected with the inclined wing and inclines towards the ship body, the flat wing is an NACA wing type, and the inclined wing and the flap are novel supercavitation wing types;
the tail hydrofoil is integrally positioned on the bottom center line of the tail end of the ship main body and comprises a vertical wing which is vertically installed and is parallel to the axis of the ship main body and a short wing which is horizontally fixed at the end part of the vertical wing, the vertical wing adopts a symmetrical NACA wing shape, and the short wing adopts a novel supercavitation wing shape;
the novel supercavity wing section 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, an arc-shaped contraction end is formed, the suction surface and the stress surface are arc-shaped protruding arc-shaped surfaces from a contact end to the opening end, the suction surface determines the outline through a numerical simulation method, the stress surface determines the outline through a Johnson three-order design method, and the contraction end determines the outline through an NACA design method.
2. Hydrofoil craft according to claim 1,
the pressure surface Johnson third-order design method comprises the following steps:
converting flow in supercavitation hydrofoil complex plane { Z } into completely wetted hydrofoil complex planeThe flow inside;
the vorticity distribution Ω (x) under the fully wetted airfoil is then calculated, expressed as a sinusoidal series:
wherein V represents the forward speed, A0And AnRepresenting the coefficient of expansion of the sine series of the profile vorticity distribution;
converting a coordinate x and an angular coordinate theta in the chord length direction of the airfoil profile by utilizing the Grouer coordinate transformation:
determining a coefficient An representing unknown vorticity distribution by using a thin-section theory, and determining a lift coefficient result C of the novel supercavity airfoil profile due to conformal transformationLEqual to the coefficient of pitching moment of fully wetted airfoils
A0and A1、A2Respectively representing the expansion coefficients of the sine series of the profile vorticity distribution;
drag coefficient C of novel supercavitation airfoilDCoefficient of lift with fully wetted airfoilCorrespondingly, the calculation formula is as follows:
elimination of A in (2), (4) and (5)0Firstly, on the premise of zero-degree attack angle and non-chord line reference line, determining the pressure surface of the optimal novel supercavitation airfoil profile, then determining the value of the coefficient for maximizing the efficiency of the novel supercavitation airfoil profile, wherein the efficiency of the novel supercavitation airfoil profile is defined as the ratio of lift coefficient to resistance, namely:
after determining this value [ -A ] is determined2/A1]The maximum value of (2) is substituted to obtain the maximum ideal efficiency:
after the conversion:
the calculation formula of the stressed surface shape corresponding to the three solutions is obtained as follows:
wherein y represents the distance perpendicular to the chord length direction of the airfoil, c represents the chord length of the airfoil, and x represents the distance in the chord length direction of the airfoil.
3. Hydrofoil craft according to claim 1,
the steps of determining the suction surface by a numerical simulation method are as follows:
step 100, the maximum thickness is formed at the opening end formed by the pressure surface and the suction surface, and the value of the opening end is 0.1 times of the length of the pressure 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 pressure surface and the suction surface is established;
step 110, establishing a two-dimensional flow field in a cuboid region shape which surrounds 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 120, performing grid division in the two-dimensional watershed by adopting a cutting body grid, and increasing grid density for the front edge, the tail edge and the wake region of the hydrofoil;
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 gas-water dynamic 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.
4. Hydrofoil craft according to claim 1,
the steps for designing the constriction by the NACA design method are as follows:
step 200, setting the length of the contraction end to be 0.36 times of the length of the pressure surface, determining the positions of the front edge and the rear edge of the contraction end, establishing parameterized curves of the front edge and the rear edge through software, and generating a two-dimensional hydrofoil model with the pressure surface, the suction surface and the contraction end;
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 gas-water dynamic performance of the hydrofoil;
step 240, the systolic end parameters are changed and then steps 200 through 240 are repeated to determine the optimal solution for the systolic end profile.
5. Hydrofoil craft according to claim 1,
and if the width of the vertical wing is the chord length C, the length of the ship main body is 22 times of the chord length, the width of the ship main body is 6 times of the chord length, and the height of the ship main body is 2.6 times of the chord length.
6. Hydrofoil craft according to claim 5,
the height of the vertical wing is 1.8 times of chord length, and the widths of the flat wing, the inclined wing and the folding wing are respectively 2 times of chord length; the length of the flat wing is 3.3 times of chord length, and the length of the flap wing and the length of the oblique wing are respectively 3.6 times of chord length.
7. Hydrofoil craft according to claim 6,
the included angle between the oblique wing and the flap is 90 degrees; the included angle between the flat wing and the oblique wing is 135 degrees.
8. Hydrofoil craft according to claim 7,
the immersion depth of the short wing is 1.8 times of chord length, and the length of the short wing is 2.3 times of chord length.
9. Hydrofoil craft according to claim 5,
the spread width of the two front hydrofoils is 16 times of chord length.
Technical Field
The invention relates to the field of ships, in particular to a hydrofoil ship adopting a novel supercavitation wing profile to reduce wave making resistance and viscous resistance during navigation.
Background
With the continuous consumption of land resources, countries in the world use and develop ocean resources as an important strategy for social development, which puts an urgent need on the development of high-performance ships. The ship resistance is closely related to the navigation speed, the hull of the traditional ship is mostly immersed below the water surface, the wet surface area is large, the navigation resistance is increased, the viscous resistance is approximately proportional to the square of the speed, the wave making resistance is approximately proportional to the sixth power of the speed, and therefore the speed of the traditional ship is greatly limited to be improved.
The hydrofoil ship raises the ship body out of the water surface by generating upward lifting force through the pressure difference between the upper surface and the lower surface of the hydrofoil when the hydrofoil ship is at high navigational speed, so that the wet surface area of the hydrofoil ship is reduced, the viscous resistance and the wave making resistance of the hydrofoil ship are further reduced, and the hydrofoil ship is an effective way for realizing the rapidity of the ship.
The hydrofoil is used as a key part of the hydrofoil ship, and when the sailing speed reaches 50 knots, the hydrofoil is inevitably subjected to cavitation, which affects the gas-water dynamic performance of the hydrofoil. On the other hand, if the supercavitation phenomenon occurs, namely the suction surface of the hydrofoil is completely surrounded by the cavitation, the resistance of the hydrofoil is greatly reduced at the moment, and the navigation speed can be greatly improved.
Patent document CN 201210319158.6 provides an ultra-high speed supercavitation twin-hull hydrofoil craft, in which the hydrofoil and the front transverse edges of the bottom surfaces of the two craft bodies are inflated by a ventilating device, so that the lifting surfaces of the hydrofoil and the bottom surfaces of the two craft bodies are covered by a thin air film, even if supercavitation is formed between the hydrofoil and the bottom surfaces of the two craft bodies, thereby achieving the purpose of reducing viscous resistance. However, when the scheme is applied to the existing common NACA hydrofoil structure, the cavitation increased at high sailing speed can adversely affect the aerodynamic performance of the hydrofoil, and when the scheme is applied to the existing supercavitation hydrofoil, the working efficiency at low sailing speed is also reduced, and the working requirement of a ship during low-speed sailing cannot be met.
Furthermore, the technique of creating the supercavity by artificial ventilation requires the addition of additional ventilation means, thereby increasing the complexity of the mechanism. In order to meet the requirement that hydrofoil ships have good working efficiency when sailing at low speed and high speed, the development of advanced novel airfoil profiles which have good performance when sailing at low speed and high speed is urgently needed, so that better social benefit and economic benefit are obtained.
Disclosure of Invention
The invention aims to provide a hydrofoil ship adopting a novel supercavitation wing profile to reduce wave making resistance and viscous resistance during navigation.
In particular to a hydrofoil ship with a novel supercavitation wing profile, which comprises a ship main body, two symmetrical front hydrofoils arranged at the front section of the ship main body, and a tail hydrofoil arranged at the tail part of the ship,
the front hydrofoil comprises a horizontal flat wing, an inclined wing and a flap, wherein the horizontal flat wing, the inclined wing and the flap are sequentially connected, the inclined wing is connected with one end, away from the ship body, of the flat wing and inclines downwards, the flap is connected with the inclined wing and inclines towards the ship body, the flat wing is an NACA wing type, and the inclined wing and the flap are novel supercavitation wing types;
the tail hydrofoil is integrally positioned on the bottom center line of the tail end of the ship main body and comprises a vertical wing which is vertically installed and is parallel to the axis of the ship main body and a short wing which is horizontally fixed at the end part of the vertical wing, the vertical wing adopts a symmetrical NACA wing shape, and the short wing adopts a novel supercavitation wing shape;
the novel supercavity wing section 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, an arc-shaped contraction end is formed, the suction surface and the stress surface are arc-shaped protruding arc-shaped surfaces from a contact end to the opening end, the suction surface determines the outline through a numerical simulation method, the stress surface determines the outline through a Johnson three-order design method, and the contraction end determines the outline through an NACA design method.
In one embodiment of the invention, the pressure surface is designed in a Johnson third order process with the following steps:
converting flow in supercavitation hydrofoil complex plane { Z } into completely wetted hydrofoil complex planeThe flow inside;
the vorticity distribution Ω (x) under the fully wetted airfoil is then calculated, expressed as a sinusoidal series:
wherein V represents the forward speed, A0And AnRepresenting the coefficient of expansion of the sine series of the profile vorticity distribution;
converting a coordinate x and an angular coordinate theta in the chord length direction of the airfoil profile by utilizing the Grouer coordinate transformation:
determining a coefficient An representing unknown vorticity distribution by using a thin-section theory, and determining a lift coefficient result C of the novel supercavity airfoil profile due to conformal transformationLEqual to the coefficient of pitching moment of fully wetted airfoilsThe calculation formula is as follows:
A0and A1、A2Respectively representing the expansion coefficients of the sine series of the profile vorticity distribution;
drag coefficient C of novel supercavitation airfoilDCoefficient of lift with fully wetted airfoilCorrespondingly, the calculation formula is as follows:
elimination of A in (2), (4) and (5)0Firstly, on the premise of zero-degree attack angle and non-chord line reference line, determining the pressure surface of the optimal novel supercavitation airfoil profile, then determining the value of the coefficient for maximizing the efficiency of the novel supercavitation airfoil profile, wherein the efficiency of the novel supercavitation airfoil profile is defined as the ratio of lift coefficient to resistance, namely:
after determining this value [ -A ] is determined2/A1]The maximum value of (2) is substituted to obtain the maximum ideal efficiency:
after the conversion:
the calculation formula of the stressed surface shape corresponding to the three solutions is obtained as follows:
wherein y represents the distance perpendicular to the chord length direction of the airfoil, c represents the chord length of the airfoil, and x represents the distance in the chord length direction of the airfoil.
In one embodiment of the invention, the step of determining the suction surface by numerical simulation is as follows:
step 110, establishing a two-dimensional flow field in a cuboid region shape which surrounds 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 120, performing grid division in the two-dimensional watershed by adopting a cutting body grid, and increasing grid density for the front edge, the tail edge and the wake region of the hydrofoil;
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 gas-water dynamic performance of the hydrofoil;
step 140, changing the curve parameters of the suction surface, and repeating
In one embodiment of the present invention, the step of designing the constriction end by the NACA design method is as follows:
step 200, setting the length of the contraction end to be 0.36 times of the length of the pressure surface, determining the positions of the front edge and the rear edge of the contraction end, establishing parameterized curves of the front edge and the rear edge through software, and generating a two-dimensional hydrofoil model with the pressure surface, the suction surface and the contraction end;
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 gas-water dynamic performance of the hydrofoil;
step 240, the systolic end parameters are changed and then steps 200 through 240 are repeated to determine the optimal solution for the systolic end profile.
In one embodiment of the present invention, when the width of the vertical wing is defined as a chord length C, the length of the ship body is 22 times the chord length, the width is 6 times the chord length, and the height is 2.6 times the chord length.
In one embodiment of the present invention, the vertical wing has a height of 1.8 times the chord length, and the flat wing, the oblique wing, and the flap each have a width of 2 times the chord length; the length of the flat wing is 3.3 times of chord length, and the length of the flap wing and the length of the oblique wing are respectively 3.6 times of chord length.
In one embodiment of the invention, the angle between the oblique wing and the flap is 90 degrees; the included angle between the flat wing and the oblique wing is 135 degrees.
In one embodiment of the invention, the immersion depth of the stub is 1.8 times chord length, and the length is 2.3 times chord length.
In one embodiment of the invention, the deployed width of both of said front hydrofoils is 16 times the chord length.
The hydrofoil ship adopts the air-hydraulic integrated combined front hydrofoil with the novel supercavitation wing profile and the deep-immersed empennage, so that the hydrofoil ship has better rapidity and stability during high-speed and low-speed navigation, the working range of the hydrofoil ship is increased, and the hydrofoil ship achieves the effects of strong working adaptability, simple structure, reliable work and manufacturing cost saving. The problem that a hydrofoil ship in the prior art can only adapt to a low-speed working condition when adopting a common NACA hydrofoil and can only adapt to a high-speed working condition when adopting a traditional supercavitation hydrofoil is completely solved.
The novel supercavitation airfoil profile design method combines the traditional supercavitation airfoil profile and the common NACA airfoil profile design method, so that the profile of the main body suction surface is surrounded by supercavitation under the design condition, and sufficient structural strength can be ensured. The contraction end increases the strength of the hydrofoil by increasing the cross-sectional area and the inertia modulus of the hydrofoil; on the other hand, the pressure difference resistance can be reduced through the effective curved surface and the attack angle, the trailing edge vortex is reduced, the energy loss is reduced, and extra lift force is provided for the hydrofoil in a full-wet state.
Drawings
FIG. 1 is a schematic view of a hydrofoil vessel according to one embodiment of the present invention;
FIG. 2 is a right side view of the hydrofoil craft of FIG. 1;
FIG. 3 is a cross-sectional view of a novel supercavitation airfoil according to one embodiment of the present invention;
FIG. 4 is a schematic illustration of the variation of lift and drag with cavitation number for a novel supercavitation airfoil according to one embodiment of the present invention;
FIG. 5 is a schematic representation of the change in lift-to-drag ratio with cavitation number for a novel supercavitation airfoil according to one 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, in one embodiment of the present invention, a
As shown in fig. 2, the front hydrofoil 2 includes a horizontal flat wing 21, an oblique wing 22 connected to one end of the flat wing 21 away from the ship body 1 and inclined downward, and a flap 23 connected to the oblique wing 22 and inclined toward the ship body 1, the flat wing 21 is a NACA wing profile, and the oblique wing 22 and the flap 23 are novel super-cavity wing profiles; the angle between the oblique wing 22 and the flap 23 is 90 degrees, and the angle between the flat wing 21 and the oblique wing 22 is 135 degrees.
The tail hydrofoil 3 is integrally positioned on the bottom center line of the tail end of the ship main body 1 and comprises a vertical wing 31 which is vertically installed and is parallel to the axis of the ship main body 1 and a short wing 32 which is horizontally fixed at the end part of the vertical wing 31, the vertical wing 31 adopts a symmetrical NACA wing shape, and the short wing 32 adopts a novel supercavitation wing shape.
As shown in fig. 3, the novel supercavity airfoil comprises a
The hydrofoil ship of this embodiment adopts the combined front hydrofoil of the gas water-powered integration that possesses novel supercavitation wing section and the fin of deep-dipping formula, makes this hydrofoil ship all have better rapidity and stability when high low-speed navigation, increases the working range of hydrofoil ship, makes this hydrofoil ship reach work strong adaptability, simple structure, reliable operation, practice thrift manufacturing cost's effect. The problem that a hydrofoil ship in the prior art can only adapt to a low-speed working condition when adopting a common NACA hydrofoil and can only adapt to a high-speed working condition when adopting a traditional supercavitation hydrofoil is completely solved.
The novel supercavitation airfoil section design method combines a traditional supercavitation airfoil section and a common NACA airfoil section design method, the profile of the
The integral gas-water dynamic performance of the novel supercavitation airfoil formed by the characteristics can be verified and optimized by numerical calculation.
The novel supercavitation wing profile can generate supercavitation at high speed, the viscous resistance of the fully-wet hydrofoil is reduced by 90%, and the
preceding hydrofoil 2 adopts pneumatic and pneumatic integrated configuration, comprises flat wing 21, oblique wing 22 and flap 23, and flat wing 21 adopts traditional NACA wing section in order to provide extra lift when high navigational speed, and oblique wing 22 and flap 23 then adopt novel supercavitation wing section, produce when high navigational speed and ventilate supercavitating and provide effectual lift naturally, and then lifting boats and ships owner alms bowl 1, reduce viscous resistance by a wide margin to realize the purpose of high-speed navigation. The front hydrofoil 2 does not need to be additionally provided with a complicated adjusting and driving mechanism, and has the advantages of simple structure, reliable work, high stability and the like.
The tail hydrofoil 3 adopts a deep-dipping structure, when the ship sails at high speed in waves, the ship body 1 is lifted out of the water surface, only the vertical wing 31 and the short wing 32 are below the water surface, the interface of water and air is on the vertical wing 31, and the influence of the waves is small due to the small cross-sectional area of the vertical wing 31, so that the wave force and the wave moment on the
In one embodiment of the present invention, when the width of the vertical fin 31 of the tail hydrofoil 3 is equal to the chord length C, the length of the ship body 1 is 22 times the chord length, the width is 6 times the chord length, the height is 2.6 times the chord length, and the deployed width of the two front hydrofoils 2 is 16 times the chord length.
The height of the vertical wing 31 is 1.8 times of chord length, the immersion depth of the short wing 32 is 1.8 times of chord length, and the length is 2.3 times of chord length. When the
The widths of the flat wing 21, the oblique wing 22 and the flap 23 are respectively 2 times of chord length; the length of the flat wing 21 is 3.3 times the chord length, and the lengths of the flap 23 and the oblique wing 22 are 3.6 times the chord length respectively. The inclined wing 22 and the flap 23 form an included angle of 90 degrees; the included angle between the flat wing 21 and the oblique wing 22 is 135 degrees.
In one embodiment of the present invention, the
the profile design of the
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 hydrofoil is represented by a sinusoidal series:
wherein V represents the forward speed, A0And AnRepresenting the coefficient of expansion of the sine series of the profile vorticity distribution; θ is a variable related to the coordinate x in the chord length direction of the airfoil, see the following formula (3);
and (3) converting a coordinate x (along the chord length direction of the airfoil) in the chord length direction of the airfoil and an angular coordinate theta by utilizing a Grouer coordinate transformation:
the thin section theory is used for solving the problem of completely soaking the periphery of the hydrofoilDetermining a coefficient An representing unknown vorticity distribution, and a lift coefficient result C of the novel supercavity airfoil profile due to conformal transformationLEqual to the coefficient of pitching moment of fully wetted airfoils
A0and A1、A2Respectively representing the expansion coefficients of the sine series of the profile vorticity distribution;
drag coefficient C of novel supercavitation airfoilDCoefficient of lift with fully wetted airfoil
elimination of A in (2), (4) and (5)0Firstly, on the premise of zero-degree attack angle and non-chord line reference line, determining the pressure surface of the optimal supercavitation airfoil profile, then determining the value of the coefficient for maximizing the efficiency of the supercavitation airfoil profile, wherein the novel supercavitation airfoil profile efficiency is defined as the ratio of lift coefficient to (inviscid) resistance, namely:
thus, finding the maximum efficiency is equal to 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 at the surface is proportional to the circulating current, and the cavitation index is zero.
Therefore, different maximum efficiency values can be found from the number of terms retained in the vorticity distribution expression in equation (2).
Tulin-Burkart retained only the first two items of the series. For this family of profiles, the maximum ideal efficiency (at 0 attack angle) obtained by substituting equation (2) is:
the so-called 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 calculation formula of the stressed surface shape corresponding to the three solutions is obtained as follows:
wherein y represents the distance perpendicular to the chord length direction of the airfoil, c represents the chord length of the airfoil, and x represents the distance in the chord length direction of the airfoil.
In this embodiment, novel supercavitation wing section has adopted the mode of traditional supercavitation wing section and ordinary NACA wing section combination, novel supercavitation wing section main part produces the supercavitation with traditional supercavitation wing section the same when high speed, the sharp-pointed fin of novel supercavitation wing section provides extra lift for the hydrofoil with the NACA wing section the same when low speed, thereby improve the work efficiency of hydrofoil, so novel supercavitation wing section among this embodiment has synthesized the advantage of ordinary hydrofoil and traditional supercavitation hydrofoil, can all have higher air water dynamic performance at low speed and high speed.
In one embodiment of the present invention, the step of determining the
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 gas-water dynamic performance of the hydrofoil;
step 140, changing the curve parameters of the suction surface, and repeating
In one embodiment of the present invention, the steps for designing the
step 200, setting the length of a contraction end to be 0.36 times of the length of a pressure surface, determining the positions of a front edge and a rear edge of a 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 pressure surface, a suction 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 gas-water dynamic 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.
In the above embodiment, the designed novel supercavitation airfoil is an SCSB-25-5 hydrofoil, and the designed lift coefficient is 0.25 and the designed attack angle is 5 degrees in the completely supercaviated state. It can be seen from fig. 4 and 5 that, along with the increase of cavitation number, the lift force of the novel super-cavity wing profile is increased even the overall efficiency is increased continuously, when the super-cavity occurs, namely the cavitation number is smaller than 0.3, the lift-drag ratio of the hydrofoil is not changed greatly, and the novel super-cavity wing profile can provide enough lift force at high, medium and low speed compared with the common hydrofoil and the traditional super-cavity hydrofoil, which means that the
In an embodiment of the present invention, the length of the
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.
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