CN110598231B - Design method of bionic airfoil blade - Google Patents

Abstract

The invention discloses a design method of a bionic airfoil blade, belonging to the technical field of impeller design and production processing, and comprising the following specific steps of: the method comprises the steps of scanning a component fish body model according to a fish body three-dimensional, correcting through coordinate point data on the model, obtaining the maximum thickness of the model after correction, constructing a control point coordinate of the bionic airfoil blade according to the coordinate point and the maximum thickness on the model, determining the maximum thickness of the bionic airfoil blade to be designed and the control point coordinate according to design requirements, calculating the coordinate point on an outline curve of the bionic airfoil blade, guiding the coordinate point into three-dimensional design software for lofting, and generating the bionic airfoil blade; the bionic airfoil blade designed by the design method has good lift-drag characteristics and hydraulic performance, and the bionic airfoils with different maximum thicknesses can be designed by the design method, so that the practicability is high.

Description

A design method of a bionic airfoil blade

technical field

The invention belongs to the technical field of impeller design and production and processing, and in particular relates to a design method of a bionic airfoil blade designed with fish as a bionic object.

Background technique

Bionics is developing from unilateral bionics to coupling bionics in multiple aspects at the same time, from macro to micro, to a more precise direction; bionic technology is also being applied in engineering drag reduction and performance improvement. The development of bionic technology is also promoting the change of the shape and structure of the impeller; the types of bionic objects are also increasing, among which fish is the most common bionic object;

Chinese patent document (application publication number: CN105201728A) discloses a design method of a combined airfoil blade for a horizontal-axis tidal current turbine. The method studies the hydrodynamic performance of conventional airfoils and bionic airfoils respectively. The purpose of combining the conventional blade airfoil with the bionic airfoil is to design a combined airfoil blade with better performance; this method obtains the three-dimensional digital model of the fin and selects its cross-sections at different positions. The contour is used as a bionic fin airfoil. The bionic fin airfoil is selected through the analysis software, and the two-dimensional coordinates of the bionic airfoil and the required conventional airfoil are derived, and the blade element of the designed blade is optimized to obtain the parameters of each blade element. , the two-dimensional coordinates of the airfoil are converted into three-dimensional coordinate data, and the obtained three-dimensional coordinate data is imported into the three-dimensional design software for lofting processing, and finally the composite airfoil blade is generated. The above methods mainly use fins as bionic objects to design bionic airfoil blades, but because the role of fins in cruising is to maintain the balance of the fish's body, the fins are used as bionic objects to design bionic airfoil blades. The design of the bionic airfoil blade is of limited help in improving the hydraulic performance of the bionic airfoil.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art, and to provide a design method of a bionic airfoil blade with a fish body as a bionic object. This design method aims to improve the hydraulic performance of the bionic airfoil blade, takes the fish body as the bionic object and corrects the head, fin and tail of the fish body, and adopts the design method in the present invention to design the bionic airfoil blade Has high hydraulic performance and lift-drag characteristics.

To achieve the above object, the present invention has adopted the following technical solutions:

A design method for a bionic airfoil blade, comprising the following steps:

S1. Acquisition of point cloud data: Scan the fish body to obtain a three-dimensional digital model, that is, the point cloud data of the fish body, and import the point cloud data of the fish body into the reverse engineering software to obtain the three-dimensional fish body model;

S2. Construct the shape curve of the fish body and determine the length M of the fish body: establish a coordinate system, take the tip of the snout process of the fish body as the coordinate origin, and take the straight line between the tip of the snout process of the fish body and the center point of the connection between the fish body and the fish tail as On the X axis, a two-dimensional fish body shape curve is constructed based on the three-dimensional fish body model obtained in step S1, and the shape curve includes the back curve of the fish body and the abdominal curve of the fish body; the tip of the snout process of the fish body model to the tip of the tail The length of the straight line projected on the X axis is the length of the fish body M;

S3. Processing of the shape curve: Based on the coordinate system established in step S2, the obtained fish shape curve is evenly divided into k parts along the X axis, and k+1 abscissas including the origin are obtained on the X axis, A total of 2(k+1) coordinate points are obtained on the back curve of the fish body and the abdomen curve of the fish body, and the obtained coordinate points are processed dimensionless to obtain dimensionless coordinate points. After smoothing, a smooth fish body shape curve is obtained;

S4. Data correction: perform data correction according to the smooth fish body shape curve obtained after processing in step S3, including head data correction, fin data correction and tail data correction; after the data correction, the shape curve of the bionic airfoil is obtained, The shape curve includes the back curve of the bionic airfoil and the abdominal curve of the bionic airfoil, and the maximum thickness δ _max of the bionic airfoil is determined according to the shape curve of the bionic airfoil;

S5. Based on the coordinate system of step S2, divide the shape curve of the bionic airfoil into equal parts a, and obtain a+1 abscissas including the origin on the X-axis, the back curve of the bionic airfoil and the bionic wing A total of 2 (a+1) coordinate points are obtained on the abdominal curve of the type, and the control point coordinates are calculated according to the obtained coordinate points and the maximum thickness _δmax obtained in step S4;

S6. Establishment of the bionic airfoil blade: determine the maximum thickness of the bionic airfoil blade according to the design requirements, and calculate the coordinate points on the back curve of the bionic airfoil blade and the coordinate point on the abdominal curve of the bionic airfoil blade according to the maximum thickness and the coordinates of the control point , import the coordinate points obtained after the above calculation into the 3D design software for lofting processing, and generate the bionic airfoil blade.

Preferably, the specific steps of correcting the header data in the step S4 are as follows:

Based on the 791 airfoil, taking the leading edge of the 791 airfoil as the coordinate origin, and the straight line between the leading edge and the trailing edge of the 791 airfoil as the X-axis, construct the contour curve of the 791 airfoil. The length of the straight line projected between any point on the profile curve of the airfoil on the X-axis is x _d ', and the chord length of the 791 airfoil is C;

The ratio of the length x _d to the length M of the fish body projected on the X-axis of the tip of the snout of the fish body and any point on the shape curve of the fish body is x _d /M, and the shape curve of the fish body for the part where x _d /M > 0.2 The coordinate point data on the 791 airfoil remains unchanged, and the coordinate point data on the fish body shape curve in the part of x _d /M≤0.2 is corrected: replace the coordinate point data with x _d '/C≤0.2 on the shape curve of the 791 airfoil. The coordinate point data of x _d /M≤0.2 on the fish body shape curve; the connection between the shape curve of the 791 airfoil and the fish body shape curve is uniformly transitioned by the arc method.

Preferably, the specific steps of fin data correction in the step S4 are as follows:

Correction of pelvic fin data: the intersection of the abdominal curve of the fish body and the contour curve of the fins on the abdomen of the fish body produces two intersection points, namely intersection point A and intersection point B; the line that defines the line between the tip of the fish's snout process and intersection point A is projected on the X-axis The length is x _q , the projection of the straight line from the tip of the snout to the intersection point B on the X axis is x _h , the projection of the straight line from the tip of the snout to any point on the abdominal curve of the fish is on the X axis The length is x _a ; the part of x _q /M≤x _a /M≤x _h /M on the abdominal curve of the fish body adopts the arc method and is smoothed in combination with the change trend of the abdominal curve of the fish body;

Correction of dorsal fin data: the intersection of the back curve of the fish body and the profile curve of the fin on the back of the fish body produces two intersection points, which are the intersection point C and the intersection point D; the line that defines the line between the tip of the fish's snout and the intersection point C is projected on the X-axis The length is x _q ', the projection of the straight line between the tip of the fish's snout to the intersection D on the X-axis is x _h ', the projection of the straight line from the tip of the fish's snout to any point on the abdominal curve of the fish is on the X-axis The length on the axis is x _a '; the part of x _q '/M≤x _a '/M≤x _h '/M on the back curve of the fish body is smoothed by the arc method and the change trend of the back curve of the fish body.

Preferably, the specific steps of correcting the tail data in the step S4 are as follows:

The projected length of the line from the tip of the fish head snout to any point of the fish body contour curve on the X axis is x _d , and the data of the part of x _d /M < 0.7 on the fish body contour curve remain unchanged, and the part of x _d /M ≥ 0.7 The data of the fish body extends backward according to the streamline direction of the back curve of the fish body and the abdominal curve of the fish body. The back curve of the fish body and the abdominal curve of the fish body generate an intersection point on the side of the fish tail, and the intersection point is rounded.

Further preferably, the specific steps of data correction in the step S4 are as follows:

Correction of head data: Based on the 791 airfoil, with the leading edge of the 791 airfoil as the coordinate origin, and the straight line between the leading edge and the trailing edge of the 791 airfoil as the X-axis, construct the shape curve of the 791 airfoil, and the 791 airfoil The projection of the straight line between the leading edge of the 791 airfoil and any point on the profile curve of the 791 airfoil on the X axis is x _d ', and the chord length of the 791 airfoil is C;

The ratio of the length x _d to the length M of the fish body projected on the X-axis of the tip of the snout of the fish body and any point on the shape curve of the fish body is x _d /M, and the shape curve of the fish body for the part where x _d /M > 0.2 The coordinate point data on the 791 airfoil remains unchanged, and the coordinate point data on the fish body shape curve in the part of x _d /M≤0.2 is corrected: the coordinate point data of x _d '/C≤0.2 on the shape curve of the 791 airfoil are respectively Replace the coordinate point data of x _d /M≤0.2 on the fish body shape curve; the connection between the shape curve of the 791 airfoil and the fish body shape curve adopts the arc method to evenly transition;

Fin data correction, including dorsal fin data correction and pelvic fin data correction;

Correction of pelvic fin data: the intersection of the abdominal curve of the fish body and the contour curve of the fins on the abdomen of the fish body produces two intersection points, namely intersection point A and intersection point B; the line that defines the line between the tip of the fish's snout process and intersection point A is projected on the X-axis The length is x _q , the projection of the straight line between the tip of the fish snout to the intersection B is on the X axis, the length of the x _h , the straight line from the tip of the fish snout to any point on the abdominal curve of the fish is projected on the X axis The length is x _a ; the part of x _q /M≤x _a /M≤x _h /M on the abdominal curve of the fish body adopts the arc method and is smoothed in combination with the change trend of the abdominal curve of the fish body;

Correction of dorsal fin data: the intersection of the back curve of the fish body and the profile curve of the fin on the back of the fish body produces two intersection points, which are the intersection point C and the intersection point D; the line that defines the line between the tip of the fish's snout and the intersection point C is projected on the X-axis The length is x _q ', the projection of the straight line between the tip of the fish's snout to the intersection D on the X axis is x _h ', the projection of the straight line from the tip of the fish's snout to any point on the abdominal curve of the fish is at X The length on the axis is x _a '; the x _q '/M≤x _a '/M≤x _h '/M part of the back curve of the fish body adopts the arc method and combines the changing trend of the back curve of the fish body for smooth processing;

Correction of tail data: the projected length of the straight line from the tip of the fish head snout to any point of the fish shape curve on the X-axis is x _d , and the data in the part of x _d /M < 0.7 on the fish body shape curve remain unchanged, x _d / The data of the part of M≥0.7 extend backward according to the streamline direction of the back curve of the fish body and the abdominal curve of the fish body. The back curve of the fish body and the abdominal curve of the fish body generate an intersection point on the side of the fish tail. Rounded corners.

Preferably, in the step S3, dimensionless processing is performed on the coordinate points on the back curve of the fish body and the abdominal curve of the fish body, and the coordinate points on the back curve of the fish body are defined as (x _t , f _u (x _t )), The abdominal curve coordinate point of the body is defined as (x _t ,f _l (x _t )); the dimensionless coordinate of the back curve is defined as (x _t ,f' _u (x _t )), and the dimensionless coordinate of the abdominal curve is defined as (x _t ,f' _l (x _t )), the relationship between variables in dimensionless processing is defined as follows:

In the formula, t represents the coordinate point on the X axis, u is the back curve of the fish body, l is the abdominal curve of the fish body, x _t is the back curve of the fish body and the abscissa of the coordinate point on the abdominal curve of the fish body, M is the length of the fish body; f _u (x _t ) is the vertical coordinate on the back curve of the fish body at x _t , and f _l (x _t ) is the vertical coordinate on the abdominal curve of the fish body at x _t ; f' _u (x _t ) is the dimensionless ordinate on the back curve of the fish body at x _t as the abscissa, f' _l (x _t ) is the dimensionless ordinate on the abdominal curve of the fish body at x _t as the abscissa Y-axis.

Preferably, the formula for calculating the coordinates of the control point in the step S5 is as follows:

|f _l (x _d )|=f _l (x _i )/δ _max , |f _u (x _d )|=f _u (x _i )/δ _max

where: f _u ( _xi ) is the ordinate on the back curve of the airfoil at point _xi , f _l ( _xi ) is the ordinate on the curve of the airfoil at point _xi , |f _l (x _d ) | is the ordinate of the control point on the belly curve of the bionic airfoil, |f _u (x _d )| is the ordinate of the control point on the back curve of the bionic airfoil, and δ _max is the maximum thickness of the bionic airfoil.

Further preferably, in order to reduce the inconvenience caused by the error of the fish body scanning to the design of the bionic airfoil blade, the step S1 uses m fish bodies to scan, and each fish body is scanned n times, and a total of m×n sets of data are obtained. , a total of m×n fish body shape curves are obtained, the S3 step is performed on the m×n fish body shape curves to obtain dimensionless coordinates, and the dimensionless coordinates are fitted to the data to obtain a smooth fish body shape curve.

Preferably, the data fitting is performed by the least squares method, and the specific fitting method is as follows:

f(x)=b ₀ +b ₁ x

in:

式中：

where:

Since m fish bodies are selected for scanning, and each fish body is scanned n times, a total of m×n groups of data are obtained, therefore, the value of j is m×n; in the formula: b ₀ and b ₁ are constants;

为获取m×n组数据中横坐标x_i的平均值；

为横坐标为x_i时分别位于鱼体的背部曲线或者鱼体的腹部曲线上的纵坐标的平均值；

为横坐标x_i中i取值从1到j时所有横坐标的平均值，

为横坐标为

时位于鱼体的背部曲线上或鱼体的腹部曲线上的纵坐标。x _i is the abscissa on the X-axis, and f( _xi ) respectively represents the ordinate on the back curve of the fish body or the belly curve of the fish body when the abscissa is _xi ;

is to obtain the average value of the abscissa x _i in the m×n group of data;

is the average value of the vertical coordinates on the back curve of the fish body or the abdominal curve of the fish body when the abscissa is x _i ;

is the average value of all abscissas when the value of i in the abscissa x _i is from 1 to j,

is abscissa as

When the ordinate is located on the back curve of the fish body or on the abdominal curve of the fish body.

Preferably, the three-dimensional fish body model is obtained by scanning a sturgeon as a bionic object.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The bionic airfoil blade designed by the design method in the present invention has better lift-drag characteristics and hydraulic performance;

In fluids with different Reynolds numbers, the lift coefficient of the above-mentioned bionic airfoil blade increases correspondingly with the increase of the stall angle of attack. Taking the NACA0012 airfoil and NACA0015 airfoil with superior hydrodynamic performance as a comparison, the The lift coefficient of the bionic airfoil blades designed by the design method is greater than that of the NACA0012 airfoil and NACA0015 airfoil before reaching the stall angle of attack; the drag coefficient increases correspondingly with the increase of the stall angle of attack. The drag coefficient of the bionic airfoil blades designed by the method is smaller than that of the NACA0012 airfoil and NACA0015 airfoil before reaching the stall angle of attack; and 15°, the pressure difference between the upper and lower airfoils is greater than the pressure difference between the NACA0012 airfoil and the NACA0015 airfoil, so the bionic airfoil blades designed in the present invention can generate greater lift;

(2) In the process of designing the bionic airfoil blade by the design method in the present invention, data correction is performed according to the physiological characteristics of the bionic object. In the present invention, the fish body is used as the bionic object, because the function of the fish mouth is to better The geometry of the mouth does not contribute much to the hydraulic properties of the airfoil. The design method in the present invention is based on the 791 airfoil, and the data of the 791 airfoil with x _d /C≤0.2 is used in the bionic of the present invention. On the airfoil blade, the influence of the geometric structure of the fish mouth on the hydraulic characteristics of the bionic airfoil blade is avoided, and the hydraulic performance and lift-drag characteristics of the bionic airfoil blade are further improved;

(3) Since fish are cruising, fins are mainly used to maintain the balance in the cruising process, and fins have little contribution to the hydraulic properties of the airfoil, so the design method in the present invention also contributes to the fin data of the fish body. Correction is made so that the back curve of the bionic airfoil and the abdominal curve of the bionic airfoil of the fin are smoothed by using the arc method and combined with the changing trend of the back curve and the abdominal curve. The back curve and the abdominal curve of the smoothed bionic airfoil are not The fin-like structure without fish improves the hydraulic characteristics and lift-drag performance of the bionic airfoil blade;

(4) The main purpose of the tail of the fish is to push the body forward and control the direction, maintain the balance of the fish, and make little contribution to the hydraulic performance of the bionic airfoil. Therefore, the design method in the present invention corrects the data of the tail, The tail of the bionic airfoil extends backward according to the streamline direction of the back curve of the bionic airfoil and the abdominal curve of the bionic airfoil. The back curve and the abdominal curve generate an intersection point on the right side of the fish body, and the intersection point is rounded. Therefore, by correcting In the future, the tail of the bionic airfoil blade has a smooth rounded structure, which enhances the hydraulic characteristics and lift-drag performance of the bionic airfoil blade;

(5) In the design method of the present invention, in the process of smoothing the shape curve of the fish body model, the coordinate points on the back curve and the abdomen curve of the fish body model are processed in a dimensionless manner, so as to avoid the fish body due to the scanning process. The difference in the size of the fish body and the scanning position leads to the problem that the bionic airfoil blade of the component has a large error, which improves the accuracy of constructing the bionic airfoil blade by the design method in the present invention; in addition, the smooth processing of the curve makes the The designed bionic airfoil has a smooth surface, which reduces the drag of the designed bionic airfoil blade in the fluid.

(6) The design method in the present invention constructs the coordinates of the control points, and its purpose is to be suitable for calculating the bionic airfoil blades of different thicknesses and designs, and to determine the maximum thickness of the bionic airfoil blades according to the constructed control point coordinates and the design requirements. And calculation formula, calculate the coordinate points of the back curve and abdominal curve of the bionic airfoil blade to be designed, and it is convenient to import the engineering software for lofting processing to design the required bionic airfoil blade, which has wide applicability and strong practicability.

(7) In the design method of the present invention, in the process of designing the bionic airfoil blade, by scanning a plurality of fish bodies, and scanning each fish body multiple times, and then performing the operations of the above steps in the present invention, and then obtaining a plurality of fish bodies. The coordinates of the control points are grouped, and the coordinates of the control points are averaged, which greatly reduces the error existing in the design process of the bionic airfoil blade, so that the designed bionic airfoil blade has good hydraulic characteristics and lift-drag performance.

Description of drawings

Fig. 1 is the structural representation of the present invention;

Fig. 2 is the structural representation of sturgeon model in the present invention;

3 is a comparison diagram of the lift coefficient of the bionic airfoil blade, the NACA0012 airfoil and the NACA0015 airfoil in the present invention; wherein, the Reynolds number Re=1E6;

4 is a comparison diagram of the lift coefficient of the bionic airfoil blade, the NACA0012 airfoil and the NACA0015 airfoil in the present invention; wherein, Reynolds number Re=3E6;

5 is a comparison diagram of the lift coefficient of the bionic airfoil blade, the NACA0012 airfoil and the NACA0015 airfoil in the present invention; wherein, the Reynolds number Re=5E6;

6 is a comparison diagram of the drag coefficient of the bionic airfoil blade, the NACA0012 airfoil and the NACA0015 airfoil in the present invention; wherein, the Reynolds number Re=1E6;

7 is a comparison diagram of the drag coefficient of the bionic airfoil blade, the NACA0012 airfoil and the NACA0015 airfoil in the present invention; wherein, the Reynolds number Re=3E6;

8 is a comparison diagram of the drag coefficient of the bionic airfoil blade, the NACA0012 airfoil and the NACA0015 airfoil in the present invention; wherein, the Reynolds number Re=5E6;

Fig. 9 is the pressure curve comparison diagram of the bionic airfoil blade in the present invention, the NACA0012 airfoil and the NACA0015 airfoil in a fluid whose Reynolds number is 3E6; wherein, the power angle is 5°;

Fig. 10 is a graph comparing the pressure curves of the bionic airfoil blade, the NACA0012 airfoil and the NACA0015 airfoil in a fluid with a Reynolds number of 3E6 in the present invention; wherein, the power angle is 10°;

Figure 11 is a graph comparing the pressure curves of the bionic airfoil blade, the NACA0012 airfoil and the NACA0015 airfoil in a fluid with a Reynolds number of 3E6 in the present invention; wherein, the power angle is 15°;

FIG. 12 is a comparison diagram of the pressure curves of the bionic airfoil blade in the present invention, the NACA0012 airfoil and the NACA0015 airfoil in a fluid with a Reynolds number of 3E6; wherein the power angle is 20°.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention are further described below with reference to the accompanying drawings through specific embodiments.

In this embodiment, sturgeon is used as the acquisition model of the bionic airfoil blade, and the specific operation method in this embodiment is also applicable to other fish bodies for acquiring the bionic airfoil and designing the airfoil blade.

As shown in Figure 1, the bionic airfoil blade designed based on sturgeon as a bionic object, its shape curve includes the back curve of the bionic airfoil blade and the belly curve of the bionic airfoil blade, the back curve of the bionic airfoil blade and the belly curve of the bionic airfoil blade The two ends generate intersection points, the straight line distance between the two intersection points is the chord length of the airfoil, and the maximum distance between the back curve of the bionic airfoil blade and the belly curve of the bionic airfoil blade is the maximum thickness of the bionic airfoil blade _δmax ;

As shown in FIG. 1 , the included angle formed by the back curve of the bionic airfoil blade and the belly curve of the bionic airfoil blade at the leading edge is α, α=14.43°; the back curve and the bionic airfoil curve are in The included angle formed by the trailing edge is β, and β=6.42°.

The specific steps for the design method of the bionic airfoil blade are as follows:

S1. Acquisition of point cloud data: The complete sturgeon body is freely stretched and fixed on a round table with a non-contact 3D laser scanner, and a patch for data collection is pasted around the sturgeon's body, and the three-dimensional scanning is performed. Scan the sturgeon to obtain point cloud data of sturgeon, and import the acquired point cloud data into Geomagic Design X engineering software to obtain a three-dimensional sturgeon model;

In the above step S1, in order to reduce the influence of the scanning error on the accuracy of constructing the sturgeon model, m sturgeon fish are selected for scanning, and each sturgeon fish is scanned n times to obtain m×n groups of data;

In the above step S1, the accuracy of the three-dimensional scanner is 0.03mm;

S2. Construct the shape curve of the sturgeon body. The length M of the sturgeon body has been determined: as shown in Figure 2, a coordinate system is established. The straight line between the tip of the snout process and the center point of the fish body and the connection of the fish tail is the X axis, and a two-dimensional sturgeon fish body shape curve is constructed based on the three-dimensional fish body model obtained in step S1, and the shape curve includes the sturgeon fish body shape curve. The back curve of the fish body and the abdominal curve of the sturgeon body; the projection of the straight line from the tip of the snout to the tip of the tail of the sturgeon model on the X-axis is the length of the sturgeon body M;

S3. Processing of the shape curve: Based on the coordinate system established in step S2, the obtained sturgeon body shape curve is evenly divided into k parts along the X axis, and k+1 horizontal lines including the origin are obtained on the X axis Coordinates, a total of 2(k+1) coordinate points are obtained on the back curve of the sturgeon body and the abdominal curve of the sturgeon body, and the coordinate points of the back curve of the sturgeon body are defined as (x _s , f _u (x _s )), the coordinate point of the abdominal curve of the sturgeon body is defined as (x _s ,f _l (x _s )); the obtained coordinate points are subjected to dimensionless processing to obtain dimensionless coordinate points, and the back curve of the sturgeon body is infinite The dimension coordinate is defined as (x _s ,f' _u (x _s )), the dimensionless coordinate point of the abdominal curve of the sturgeon body is defined as (x _s ,f' _l (x _s )), and the dimensionless coordinate points are in sequence After connecting and smoothing, a smooth sturgeon body shape curve is obtained; the relationship between variables in dimensionless processing is defined as follows:

In the formula, t represents the coordinate point on the X-axis, u is the back curve of the sturgeon fish body, l is the abdominal curve of the sturgeon fish body, x _t is the back curve of the sturgeon fish body and the coordinates on the abdominal curve of the fish body The abscissa of the point, M is the length of the fish body; f _u (x _t ) is the ordinate on the back curve of the sturgeon body at x _t , and f _l (x _t ) is the sturgeon at x _t . The ordinate on the abdominal curve of the fish body; f' _u (x _t ) is the dimensionless ordinate on the back curve of the sturgeon body at x _t , and f' _l (x _t ) is the abscissa of The dimensionless ordinate on the curve of the abdomen of the sturgeon body at x _t ; M is the length of the sturgeon body.

Since in step S1, in order to reduce the influence of the scanning error on the accuracy of building the sturgeon model, m sturgeon fish are selected for scanning, and each sturgeon fish is scanned n times. Therefore, in step S2, a total of m×n sturgeon fish are obtained. The body shape curve, in step S3, 2(k+1) coordinate points can be obtained on each sturgeon body shape curve, and the coordinate points are subjected to dimensionless processing to obtain the dimensionless coordinate points. The least squares method is used for data fitting. After fitting, a sturgeon body shape curve is formed, and the sturgeon body shape curve tends to be smooth. The specific fitting method is as follows:

f(x)=b ₀ +b ₁ x, where:

式中：

where:

Since m sturgeons are selected for scanning, and each sturgeon is scanned n times, a total of m×n groups of data are obtained, so the value of j is m×n;

In the formula: b ₀ and b ₁ are constants;

为获取m×n组数据中横坐标x_i的平均值；

为横坐标为x_i时鲟鱼鱼体的背部曲线上的纵坐标的平均值；

为横坐标x_i中i取值从1到j时所有横坐标的平均值，

为横坐标为

时位于鲟鱼鱼体的背部曲线上纵坐标；When simulating the back curve of the sturgeon body, x _i is the abscissa on the X axis, and f( _xi ) respectively represents the ordinate of the back curve of the sturgeon body when the abscissa is _xi ;

is to obtain the average value of the abscissa x _i in the m×n group of data;

is the average value of the vertical coordinates on the back curve of the sturgeon body when the abscissa is x _i ;

is the average value of all abscissas when the value of i in the abscissa x _i is from 1 to j,

is abscissa as

When the ordinate is located on the back curve of the sturgeon body;

为获取m×n组数据中横坐标x_i的平均值；

为横坐标为x_i时鲟鱼鱼体的腹部曲线上的纵坐标的平均值；

为横坐标x_i中i取值从1到j时所有横坐标的平均值，

为横坐标为

时位于鲟鱼鱼体的腹部曲线上纵坐标。When simulating the abdominal curve of the sturgeon body, x _i is the abscissa on the X-axis, and f(x _i ) respectively represents the ordinate of the abdominal curve of the sturgeon body when the abscissa is x _i ;

is to obtain the average value of the abscissa x _i in the m×n group of data;

is the average value of the ordinate on the abdominal curve of the sturgeon body when the abscissa is x _i ;

is the average value of all abscissas when the value of i in the abscissa x _i is from 1 to j,

is abscissa as

It is located on the ordinate on the abdominal curve of the sturgeon body.

Preferably, in step S1, 3 sturgeons are selected for scanning, and each sturgeon is scanned 3 times to obtain a total of 9 groups of data, in the above formula, j is 9;

S4. Data correction: According to the smooth sturgeon body shape curve obtained after processing in step S3, data correction is performed, including head data correction, fin data correction and tail data correction; The profile curve of the airfoil includes the back curve of the bionic airfoil and the abdominal curve of the bionic airfoil, and the maximum thickness δ _max of the bionic airfoil is determined according to the profile curve of the bionic airfoil;

In the above steps, the specific steps of header data correction are as follows:

Based on the 791 airfoil, taking the leading edge of the 791 airfoil as the coordinate origin, and the straight line between the leading edge and the trailing edge of the 791 airfoil as the X-axis, construct the contour curve of the 791 airfoil. The length of the straight line projected between any point on the profile curve of the airfoil on the X-axis is x _d ', and the chord length of the 791 airfoil is C;

The ratio of the length x _d on the X axis of the projection of the tip of the snout of the sturgeon body to any point on the curve of the sturgeon body shape and the length M of the sturgeon body is x _d /M, where x _d /M > 0.2 Part of the coordinate point data on the shape curve of the sturgeon fish body remains unchanged, and the coordinate point data on the shape curve of the sturgeon fish body part of x _d /M≤0.2 is corrected: put the shape of the 791 airfoil on the shape curve of x _d ' The coordinate point data of /C≤0.2 respectively replace the coordinate point data of x _d /M≤0.2 on the sturgeon body shape curve; the connection between the shape curve of the 791 airfoil and the shape curve of the sturgeon body adopts the arc method to evenly transition .

The specific steps of fin data correction are as follows:

Fin data correction includes dorsal fin data correction and pelvic fin data correction;

Correction of pelvic fin data: The curve of the abdomen of the sturgeon body intersects with the contour curve of the fin of the abdomen of the sturgeon body to generate two intersection points, which are the intersection point A and the intersection point B; The length of the straight line projected on the X-axis is x _q , the length of the straight line projected on the X-axis between the tip of the sturgeon body snout to the intersection B is x _h , the length of the sturgeon body snout tip to the sturgeon body The length of the straight line projected at any point on the abdominal curve on the X-axis is x _a ; the part of x _q /M≤x _a /M≤x _h /M on the abdominal curve of the sturgeon body adopts the arc method and combines with the sturgeon fish The changing trend of the abdominal curve of the body is smoothed;

Correction of dorsal fin data: the intersection of the back curve of the sturgeon body and the profile curve of the back fin of the sturgeon body produces two intersection points, which are the intersection point C and the intersection point D; The length of the straight line projected on the X axis is x _q ', the length of the straight line projected on the X axis between the tip of the sturgeon body snout to the intersection D is x _h ', the tip of the sturgeon body snout to the sturgeon fish The length of a straight line projected on the X-axis at any point on the abdominal curve of the sturgeon is x _a '; on the back curve of the sturgeon body x _q '/M≤x _a '/M≤x _h '/M part adopts a circular arc method and combined with the change trend of the back curve of the sturgeon body for smooth processing;

The specific steps of fishtail data correction are as follows:

The projection length of the straight line from the tip of the sturgeon body snout to any point of the sturgeon body shape curve on the X-axis is x _d , and the data of the part of x _d /M < 0.7 on the sturgeon body shape curve remain unchanged, x The data in the part of _d /M≥0.7 extend backward according to the streamline direction of the back curve of the sturgeon body and the abdominal curve of the sturgeon body. The back curve of the sturgeon body and the abdominal curve of the sturgeon body are in the tail An intersection is generated on one side, and the corners are rounded at the intersection.

S5. Based on the coordinate system of step S2, evenly divide the shape curve of the bionic airfoil into a equal parts, and obtain a+1 abscissas including the origin on the X axis, the back curve of the bionic airfoil and the bionic airfoil A total of 2(a+1) coordinate points are obtained on the abdominal curve of the airfoil, and the coordinates of the control point are calculated according to the obtained coordinate points and the maximum thickness _δmax obtained in step S4;

The control point coordinates include the bionic airfoil back curve control point coordinates (x _d , |f _u (x _d )|) and the bionic airfoil abdominal curve control point coordinates (x _d , |f _l (x _d )|), Its calculation formula is as follows:

|f _l (x _d )|=f _l (x _i )/δ _max , |f _u (x _d )|=f _u (x _i )/δ _max

where: f _u ( _xi ) is the ordinate on the back curve of the airfoil at point _xi , f _l ( _xi ) is the ordinate on the curve of the airfoil at point _xi , |f _l (x _d ) | is the ordinate of the control point on the belly curve of the bionic airfoil, |f _u (x _d )| is the ordinate of the control point on the back curve of the bionic airfoil, and δ _max is the maximum thickness of the bionic airfoil.

Preferably, the value of a is 20, and the coordinates of the control points are shown in Table 1;

Table 1 Fitted coordinates of control points of bionic airfoil blades

S6. Establishment of the bionic airfoil blade: Determine the maximum thickness of the bionic airfoil blade according to the design requirements, and calculate the coordinate points on the back curve of the bionic airfoil blade and the belly curve of the bionic airfoil blade according to the maximum thickness and the coordinates of the control points in Table 1 The coordinate points obtained after the above calculation are imported into the three-dimensional design software for lofting processing, and the bionic airfoil blade is generated.

The sturgeon bionic airfoil blades, NACA0012 airfoil and NACA0015 airfoil prepared by the above method were tested in fluids with different Reynolds numbers, and their lift coefficients, drag coefficients and pressure differences were compared. The comparison results are shown in Figure 3-12 .

Among them, Sturgeon hydrofoil represents the sturgeon bionic airfoil blade.

1. Comparison of lift coefficients

Figure 3-5 shows the lift coefficients of the sturgeon bionic airfoil blade, NACA0012 airfoil and NACA0015 airfoil in fluids with Reynolds numbers Re=1E6, 3E6 and 5E6 respectively. In the fluid of , the lift coefficient of the sturgeon airfoil blade increases correspondingly with the increase of the stall angle of attack. Before reaching the stall angle of attack, the lift coefficient of the sturgeon airfoil blade is larger than that of the NACA0012 airfoil and NACA0015 airfoil;

2. Comparison of drag coefficients

Figure 6-8 shows the drag coefficients of sturgeon airfoil blades, NACA0012 airfoils and NACA0015 airfoils in fluids with Reynolds numbers Re=1E6, 3E6 and 5E6, respectively. The results show that at Re=1E6, 3E6 and 5E6 In the fluid, the drag coefficient of the sturgeon airfoil blade increases with the increase of the stall angle of attack, and the drag coefficient of the sturgeon airfoil blade is smaller than that of the NACA0012 airfoil and NACA0015 airfoil before reaching the stall angle of attack;

From the results of the above three Reynolds numbers, it is found that the larger the Reynolds number, the larger the stall angle of attack, and the maximum lift coefficient will increase accordingly; the sturgeon airfoil blade has a higher lift coefficient than the NACA0012 wing before reaching the stall angle of attack. NACA0015 airfoil and NACA0015 airfoil, but the drag coefficient is smaller than NACA0012 airfoil and NACA0015 airfoil, with better lift-drag characteristics.

3. Comparison of pressure difference

Figure 9-12 shows the pressure distribution at the intermediate cross section of the three airfoils and the intersection of the airfoils at angles of attack of 5°, 10°, 15° and 20°, and Reynolds number Re=3E6. The results show that: The NACA0012 airfoil and NACA0015 airfoil have a similar trend in the same area, that is, as the angle of attack increases, the pressure difference between the upper and lower airfoils increases, resulting in greater lift; the sturgeon airfoil blade is higher than the NACA0012 airfoil and NACA0015 airfoil. Airfoils produce greater lift at 5°, 10° and 15° angles of attack, especially in the region of maximum thickness, but this region may also lead to cavitation; since the 20° angle of attack is greater than the sturgeon airfoil in Reynolds The stall angle of attack under the condition of Re = 3E6, the stall angle of attack of the sturgeon airfoil can be found in the previous section, and the pressure difference between the upper and lower airfoils suddenly decreases;

The above results show that the sturgeon airfoil blade has better hydraulic characteristics than the NACA0012 airfoil and NACA0015 airfoil before reaching the stall angle of attack.

The above content is to further describe the present invention in conjunction with the specific embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. Several simple deductions or substitutions can also be made, which should be regarded as belonging to the protection scope determined by the claims submitted in the present invention.

Claims (10)

1. A design method of a bionic airfoil blade is characterized by comprising the following steps:

s1, point cloud data acquisition: scanning a fish body to obtain a three-dimensional digital model, namely point cloud data of the fish body, and importing the point cloud data of the fish body into reverse engineering software to obtain the three-dimensional fish body model;

s2, constructing a fish body shape curve and determining the length M of the fish body: establishing a coordinate system, taking the tip of the fish body osculating process as a coordinate origin, taking a straight line between the tip of the fish body osculating process and the central point of the joint of the fish body and the fish tail as an X axis, and constructing a two-dimensional fish body appearance curve based on the three-dimensional fish body model obtained in the step S1, wherein the appearance curve comprises a back curve of the fish body and an abdomen curve of the fish body; the length of the projection of the straight line from the tip of the osculum to the tip of the tail of the fish body model on the X axis is the length M of the fish body;

s3, processing of the outline curve: based on the coordinate system established in the step S2, evenly dividing the obtained fish body outline curve into k parts along the X axis, obtaining k +1 abscissa coordinates including the origin on the X axis, obtaining 2(k +1) coordinate points on the back curve of the fish body and the abdomen curve of the fish body, performing dimensionless processing on the obtained coordinate points to obtain dimensionless coordinate points, and obtaining a smooth fish body outline curve after sequentially connecting and smoothing the dimensionless coordinate points;

s4, data correction: performing data correction according to the smooth fish body profile curve obtained after the processing of the step S3, wherein the data correction comprises head data correction, fin data correction and tail data correction; obtaining the profile curve of the bionic wing section after data correction, wherein the profile curve of the bionic wing section comprises a back curve of the bionic wing section and an abdomen curve of the bionic wing section, and determining the maximum thickness delta of the bionic wing section according to the profile curve of the bionic wing section _max ；

S5, based on the coordinate system of the step S2, evenly dividing the outline curve of the bionic wing into a parts, acquiring a +1 horizontal coordinates including the original point on the X axis, acquiring 2(a +1) coordinate points on the back curve of the bionic wing and the abdomen curve of the bionic wing, and acquiring the maximum thickness delta obtained in the step S4 according to the acquired coordinate points _max Calculating coordinates of the control points;

s6, establishing the bionic airfoil blade: determining the maximum thickness of the bionic airfoil blade according to design requirements, calculating a coordinate point on a back curve of the bionic airfoil blade and a coordinate point on an abdomen curve of the bionic airfoil blade according to the maximum thickness and a control point coordinate, importing the calculated coordinate points into three-dimensional design software for lofting, and generating the bionic airfoil blade.

2. The method for designing a bionic airfoil blade according to claim 1, wherein the method comprises the following steps: the specific steps of the header data modification in step S4 are as follows:

based on the 791 airfoil, the front edge of the 791 airfoil is taken as a coordinate origin, and the space between the front edge and the rear edge of the 791 airfoilIs X-axis, constructing 791 profile curve of the airfoil, the length of the projection of the straight line between the leading edge of the 791 airfoil and any point on the profile curve of the 791 airfoil on the X-axis being X _d ', 791 the chord length of the airfoil is C;

the length X of the projection of the fish body osculating tip and any point on the fish body contour curve on the X-axis _d The ratio of the length of the fish body to the length M of the fish body is x _d /M，x _d The coordinate point data on the fish body outline curve with the/M being more than 0.2 is unchanged for x _d Correcting coordinate point data on the fish body outline curve with the part of/M being less than or equal to 0.2: putting the shape curve x of 791 airfoil _d ' C is less than or equal to 0.2, and the data of the coordinate points respectively replace x on the external curve of the fish body _d Data of coordinate points with/M less than or equal to 0.2; 791 the connection between the profile curve of airfoil and the profile curve of fish body is uniform.

3. The method for designing a bionic airfoil blade according to claim 1, wherein the method comprises the following steps: the specific steps of fin data modification in step S4 are as follows:

correction of ventral fin data: the abdominal curve of the fish body is intersected with the outline curve of the abdominal fish fin of the fish body to generate two intersection points, namely an intersection point A and an intersection point B; the length of a straight line projected between the tip of the fish osculum and the intersection point A on an X-axis is defined as X _q The length of the projection of the straight line between the tip of the fish osculating process and the intersection point B on the X axis is X _h The length of the projection of the straight line from the tip of the osculating process of the fish body to any point on the abdominal curve of the fish body on the X axis is X _a (ii) a X on abdominal curve of fish body _q /M≤x _a /M≤x _h The part/M adopts an arc method and combines the change trend of the abdominal curve of the fish body to carry out smoothing treatment;

dorsal fin data correction: the back curve of the fish body is intersected with the outline curve of the fish fin on the back of the fish body to generate two intersection points, namely an intersection point C and an intersection point D; the length of a straight line projected from the tip of the fish osculating process to the intersection point C on the X axis is defined as X _q ' the length of the projection of the straight line between the tip of the fish osculating process and the intersection point D on the X axis is X _h ' straight line projection from fish osculating projection tip to any point on abdominal curve of fishLength of shadow on X-axis being X _a '; x on the back curve of the fish body _q ’/M≤x _a ’/M≤x _h The part'/M adopts a circular arc method and is smoothly processed by combining the change trend of the back curve of the fish body.

4. The method for designing a bionic airfoil blade according to claim 1, wherein the method comprises the following steps: the specific steps of tail data correction in step S4 are as follows:

the projection length of the straight line from the tip of the fish head osculum to any point of the fish body outline curve on the X-axis is X _d Wherein x is on the contour curve of the fish body _d Data for the part,/M < 0.7, are unchanged, x _d The data of the part/M is more than or equal to 0.7 extends backwards according to the streamline directions of the back curve of the fish body and the abdomen curve of the fish body, an intersection point is generated on one side of the fish tail by the back curve of the fish body and the abdomen curve of the fish body, and the intersection point is subjected to fillet treatment.

5. The method for designing a bionic airfoil blade according to claim 1, wherein the method comprises the following steps: the specific steps of data correction in step S4 are as follows:

and (3) head data correction: based on the 791 airfoil profile, the 791 airfoil profile leading edge is taken as a coordinate origin, a straight line between the 791 airfoil leading edge and the 791 airfoil trailing edge is taken as an X-axis, an outline curve of the 791 airfoil profile is constructed, and the length of a straight line between the 791 airfoil leading edge and any point on the 791 airfoil outline curve projected on the X-axis is X _d ', 791 the airfoil has a chord length C;

the length X of the projection of the fish body osculating tip and any point on the fish body contour curve on the X-axis _d The ratio of the length of the fish body M to the length of the fish body is x _d /M，x _d The coordinate point data on the fish body outline curve of which the/M is more than 0.2 is unchanged for x _d Correcting coordinate point data on the fish body outline curve with the part of/M being less than or equal to 0.2: putting the shape curve x of 791 airfoil _d ' C is less than or equal to 0.2, and the data of the coordinate points respectively replace x on the external curve of the fish body _d Data of coordinate points with/M less than or equal to 0.2; 791 the connection between the profile curve of airfoil and the profile curve of fish body is uniformly transited by arc method;

correcting fin data, including dorsal fin data correction and ventral fin data correction;

correction of ventral fin data: the abdominal curve of the fish body is intersected with the outline curve of the fish fin on the abdominal part of the fish body to generate two intersection points, namely an intersection point A and an intersection point B; the length of a straight line projected from the tip of the fish osculating process to the intersection point A on the X axis is defined as X _q X, the length of the projection of the straight line between the tip of the fish osculating process and the intersection point B on the X-axis _h The length of the projection of the straight line from the tip of the osculating process of the fish body to any point on the abdominal curve of the fish body on the X axis is X _a (ii) a X on abdominal curve of fish body _q /M≤x _a /M≤x _h The part/M adopts an arc method and combines the change trend of the abdominal curve of the fish body to carry out smoothing treatment;

dorsal fin data correction: the back curve of the fish body is intersected with the outline curve of the fish fin on the back of the fish body to generate two intersection points, namely an intersection point C and an intersection point D; the length of a straight line projected from the tip of the fish osculating process to the intersection point C on the X axis is defined as X _q ', X of the length of the straight line projected on the X-axis between the tip of the fish osculating process and the intersection point D _h ' the length of the projection of the straight line from the tip of the osculating process of the fish body to any point on the abdominal curve of the fish body on the X-axis is X _a '; x on the back curve of the fish body _q ’/M≤x _a ’/M≤x _h The part'/M adopts an arc method and combines the back curve variation trend of the fish body to carry out smooth treatment;

and tail data correction: the length of the projection of the straight line from the tip of the fish head osculating process to any point of the fish body outline curve on the X axis is X _d Wherein x is on the contour curve of the fish body _d Data for the part/M < 0.7 is unchanged, x _d The data with the/M being more than or equal to 0.7 part extend backwards according to the streamline directions of the back curve of the fish body and the abdomen curve of the fish body, an intersection point is generated on one side of the fish tail by the back curve of the fish body and the abdomen curve of the fish body, and the intersection point is subjected to round angle processing.

6. The method for designing a bionic airfoil blade according to claim 1, wherein the method comprises the following steps: in the step S3, the curve of the back of the fish body and the abdomen of the fish body are determinedDimensionless processing is carried out on coordinate points on the curve, and the back curve coordinate point of the fish body is defined as (x) _t ,f _u (x _t ) The abdominal curve coordinate point of the fish body is defined as (x) _t ,f _l (x _t ) ); the dimensionless coordinates of the back curve are defined as (x) _t ,f’ _u (x _t ) Dimensionless coordinates of the abdominal curve are defined as (x) _t ,f’ _l (x _t ) Relationships between variables in dimensionless processing are defined as follows:

wherein t represents a coordinate point on the X-axis, u is a dorsal curve of the fish body, l is an abdominal curve of the fish body, and X _t The abscissa of a coordinate point on a back curve and an abdomen curve of the fish body is shown, and M is the length of the fish body; f. of _u (x _t ) As the abscissa is x _t On the back curve of the fish body, f _l (x _t ) As the abscissa is x _t The longitudinal coordinate on the abdominal curve of the fish body; f' _u (x _t ) As the abscissa is x _t On the non-dimensional ordinate, f 'of the back curve of the fish body' _l (x _t ) As the abscissa is x _t A dimensionless ordinate on the abdominal curve of the fish body.

7. The method for designing a bionic airfoil blade according to claim 1, wherein the method comprises the following steps: the formula for calculating the coordinates of the control points in step S5 is as follows:

|f _l (x _d )|＝f _l (x _i )/δ _max ，|f _u (x _d )|＝f _u (x _i )/δ _max

in the formula: f. of _u (x _i ) Is x _i Ordinate on the point airfoil back curve, f _l (x _i ) Is x _i Ordinate, | f, on the point airfoil-belly curve _l (x _d ) L is the longitudinal coordinate of the control point on the bionic wing section abdomen curve, | f _u (x _d ) I is the longitudinal coordinate, delta, of the control point on the back curve of the bionic wing profile _max The maximum thickness of the bionic airfoil.

8. The method for designing a biomimetic airfoil blade according to any of claims 1-7, wherein: in the step S1, m fish bodies are scanned, and each fish body is scanned n times to obtain mxn groups of data in total, obtain mxn fish body shape curves in total, perform the step S3 on the mxn fish body shape curves to obtain dimensionless coordinates, perform data fitting on the dimensionless coordinates to obtain a smooth fish body shape curve.

9. The method of claim 8, wherein: the data fitting adopts a least square method for fitting, and the specific fitting mode is as follows:

f(x)＝b ₀ +b ₁ x

wherein:

in the formula:

m fish bodies are selected for scanning, and each fish body is scanned for n times to obtain mxn groups of data in total, so that j takes the value of mxn; in the formula: b ₀ And b ₁ Is a constant;

x _i is the abscissa on the X axis, f (X) _i ) Respectively represent the abscissa as x _i The ordinate is positioned on the back curve of the fish body or the abdomen curve of the fish body;

to obtain the abscissa x in the mxn sets of data _i Average value of (d);

as the abscissa is x _i Average values of vertical coordinates on a back curve or an abdomen curve of the fish body respectively;

as the abscissa x _i Where i is the average of all abscissas from 1 to j,

as the abscissa is

The longitudinal coordinate is positioned on the back curve of the fish body or the abdomen curve of the fish body.

10. The method for designing a bionic airfoil blade according to claim 1, wherein the method comprises the following steps: the three-dimensional fish body model is obtained after the sturgeon is used as a bionic object to be scanned.

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