CN108038259A - Method based on curvature generation Pneumatic component shape - Google Patents
Method based on curvature generation Pneumatic component shape Download PDFInfo
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- CN108038259A CN108038259A CN201711078392.3A CN201711078392A CN108038259A CN 108038259 A CN108038259 A CN 108038259A CN 201711078392 A CN201711078392 A CN 201711078392A CN 108038259 A CN108038259 A CN 108038259A
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Abstract
The invention discloses a kind of method based on curvature generation Pneumatic component shape.The method of the present invention, comprises the following steps：The original shape curve of default Pneumatic component；Nurbs curve Parameter Expression is carried out to original shape curve, obtains the knot vector and control point coordinates of the NURBS interpolation curves of expression original shape curve；First derivative and second dervative of the interpolation curve relative to knot vector are calculated, and then tries to achieve curvature；It is whether consistent with target shape curve according to the curvature of interpolation curve, decide to continue with interative computation and still export current interpolation curve；If continuing interative computation, new second derivative values are tried to achieve using target shape song curvature of a curve and knot vector and first derivative, and new control point coordinates is further calculated, and then together with knot vector, form new interpolation curve.The present invention can efficiently and rapidly calculate the whole appearance curve for obtaining the Pneumatic component for meeting design object, have high efficiency.
Description
Technical field
The present invention relates to pneumatic design field, more particularly to the method based on curvature generation Pneumatic component shape.
Background technology
For Pneumatic components such as aircraft wing, empennage, heads, curvature has very direct with their aerodynamic characteristic
System.In pneumatic design work, main parameter is pressure distribution, and pressure is distributed the liter for determining Pneumatic component
The characteristics such as power, resistance, torque and flow separation.
One basic demand of pneumatic design is continual curvature, only continual curvature, and pressure distribution is not in just prominent
Become, be also not easy flow separation occur.Moreover, the distributional pattern of curvature can also directly affect pressure distributional pattern, curvature
Distribution whether be rationally pressure distribution whether preferable premise.
However, existing parameterization design method, including Hicks-Henne parametric methods, PARSEC parametric methods,
Batten parametric method and CST parametric methods etc. are all based on what geometry was parameterized, although so expression is directly perceived,
It can intuitively see the shape of Pneumatic curve, but between the aerodynamic characteristic of these parametric methods and component (pressure distribution)
Relation it is not directly perceived.To obtain preferable pressure distribution, it is necessary to move repeatedly data point position, and be difficult to find out it
Between rule, even with numerical optimization carry out Automatic Optimal, it is also desirable to consumption for quite a long time.
In addition, in existing parametric method, batten parametric method due to it have extraordinary Partial controll and
Fairing processing ability and obtained most commonly used application, in current most of CAD softwares such as CATIA softwares, exactly use
NURBS parametric methods therein.However, existing this kind of method be it is a kind of using data point come the method that parameterizes, completely
Not comprising curvature information, for the appearance curve of multistage expression, at most can only also ensure it is tangent, it is difficult to control continual curvature, together
When, also it is easier undulating profile occur, it is necessary to adjust data point repeatedly to eliminate undulating profile.
The content of the invention
The technical problem to be solved in the present invention is in order to overcome in the prior art for the Parametric designing side of Pneumatic component
Relation between method, and the aerodynamic characteristic of component is not directly perceived enough, clear and definite, is carried out in order to obtain needed for preferable pressure distribution excellent
Change process takes the defects of very long, proposes a kind of method based on curvature generation Pneumatic component shape.
The present invention is to solve above-mentioned technical problem by following technical proposals：
The present invention provides a kind of method based on curvature generation Pneumatic component shape, its feature is that it includes following
Step：
Make Step 1: obtaining the curvature of multiple positions of target shape curve and the coordinate of front and rear edge data point and cutting arrow
For design object parameter, and the original shape curve of default Pneumatic component；
Step 2: carrying out nurbs curve Parameter Expression to the original shape curve, obtain expressing the original shape
The knot vector and control point coordinates of the NURBS interpolation curves of curve；
Step 3: first derivative and second dervative of the NURBS interpolation curves relative to the knot vector are calculated, into
And the curvature at multiple positions of the NURBS interpolation curves is tried to achieve, wherein multiple positions of the NURBS interpolation curves and institute
The multiple positions for stating target shape curve correspond；
Step 4: judge curvature at the multiple positions of NURBS interpolation curves whether with the target shape curve
The curvature of multiple positions is consistent, when judging result is no, curvature and institute using multiple positions of the target shape curve
State knot vector and the first derivative tries to achieve new second derivative values, and perform step 5, when judging result is to be, perform
Step 6；
Step 5: using the knot vector, the second dervative, the target shape curve front and rear edge data point
Coordinate and arrow is cut, new control point coordinates is calculated, and combined with the knot vector, obtain new NURBS interpolation curves,
Replace original NURBS interpolation curves and return to step three；
Step 6: using the NURBS interpolation curves as output result.
It is preferred that the default original shape curve is the wing appearance curve chosen from aerofoil profile public database.
The target shape curve can be an appearance curve of the pilot process of Pneumatic component iteration optimization design.
It is preferred that the aerofoil profile public database is NASA airfoil databases.
It is preferred that the Pneumatic component includes airfoil member, empennage component, the head part of aircraft.
On the basis of common knowledge of the art, above-mentioned each optimum condition, can be combined, each preferably real up to the present invention
Example.
The positive effect of the present invention is：
The method based on curvature generation Pneumatic component shape of the present invention, on the basis of nurbs curve, combines curvature
Expression way, using the curvature of limited a point and several data points and arrow can be cut go out whole appearance curve come reverse, and according to
This is by the way that more efficiently quickly interative computation is come whole appearance curve of Pneumatic component for obtaining meeting design object, compared to existing
There is technology to significantly improve design efficiency.
Brief description of the drawings
Fig. 1 is the flow chart of the method that Pneumatic component shape is generated based on curvature of a preferred embodiment of the present invention.
Embodiment
With reference to Figure of description, further the preferred embodiment of the present invention is described in detail, following description
To be exemplary, not limitation of the present invention, other any are still fallen among protection scope of the present invention similar to situation.
In following specific descriptions, the term of directionality, such as "left", "right", " on ", " under ", "front", "rear", etc.,
Direction described in refer to the attached drawing uses.The component of the embodiment of the present invention can be placed in a variety of different directions, directionality
Term is for illustrative purposes and nonrestrictive.
Refering to what is shown in Fig. 1, according to the present invention a preferred embodiment it is a kind of based on curvature generation Pneumatic component shape side
Method, it comprises the following steps：
Make Step 1: obtaining the curvature of multiple positions of target shape curve and the coordinate of front and rear edge data point and cutting arrow
For design object parameter, and the original shape curve of default Pneumatic component；
Step 2: carrying out nurbs curve Parameter Expression to the original shape curve, obtain expressing the original shape
The knot vector and control point coordinates of the NURBS interpolation curves of curve；
Step 3: first derivative and second dervative of the NURBS interpolation curves relative to the knot vector are calculated, into
And the curvature at multiple positions of the NURBS interpolation curves is tried to achieve, wherein multiple positions of the NURBS interpolation curves and institute
The multiple positions for stating target shape curve correspond；
Step 4: judge curvature at the multiple positions of NURBS interpolation curves whether with the target shape curve
The curvature of multiple positions is consistent, when judging result is no, curvature and institute using multiple positions of the target shape curve
State knot vector and the first derivative tries to achieve new second derivative values, and perform step 5, when judging result is to be, perform
Step 6；
Step 5: using the knot vector, the second dervative, the target shape curve front and rear edge data point
Coordinate and arrow is cut, new control point coordinates is calculated, and combined with the knot vector, obtain new NURBS interpolation curves,
Replace original NURBS interpolation curves and return to step three；
Step 6: using the NURBS interpolation curves as output result.
It should be appreciated that target shape curve acquired in step 1, is among the design of Pneumatic component iteration optimization
One appearance curve of process.Wherein, data point refers to bent by multiple descriptions on the curve or curved surface that measure or be calculated
The data point of line or surface geometry shape.
According to the definition of Differential Geometry, bent curvature of a curve can be expressed by the first derivative and second dervative of curve.Together
Sample, if it is known that bent curvature of a curve and first derivative, can also be calculated the second dervative of curve.Sweared by the node of curve
Amount, second dervative and front and rear edge data point and cut arrow, it is possible to using the method for nurbs curve interpolation, can directly ask for meeting
The NURBS interpolation curves of condition.
At this time, the curvature of the multiple position of the bent curvature of a curve tried to achieve and target shape curve multiple points in other words can
Can be inconsistent.As it was previously stated, present invention contemplates that obtained Pneumatic component appearance curve should be continual curvature and avoid ripple
The appearance of unrestrained shape, so as to avoid mutation or the flow separation of pressure distribution.Therefore there are the inconsistent feelings of above-mentioned curvature
, it is necessary to be corrected by the method for iteration under shape.
That is, the first derivative and second dervative of generation appearance curve are calculated, and then obtains curvature, judge whether with outside target
Shape song curvature of a curve is consistent.If it is inconsistent, sat using the curvature and front and rear edge data point of target shape curve position
It is design parameter to mark and cut arrow, then is sweared with the use of the node of current appearance curve (the NURBS interpolation curves currently obtained)
Amount and first derivative, try to achieve the second dervative of target shape curve, and then interpolation is tried to achieve new appearance curve and (newly obtained
NURBS interpolation curves).Such iteration, until obtaining obtaining qualified NURBS interpolation curves, as final target outside
Shape curve.
It can be generated to obtain whole appearance curve based on curvature according to the above method, reach and generation is directly controlled by curvature
The purpose of the feature of Pneumatic component appearance curve.That is, the NURBS interpolation curves as output result, can represent Pneumatic component
Whole appearance curve.
Although the method for the present invention needs, by iterating, to pass through multiple case verifications, general iterations exists
It can reach quite high precision within ten times, computational efficiency is high, takes short.This method directly can generate gas by curvature
Dynamic component appearance curve, therefore the appearance curve that can directly control multistage expression can also lead in the continual curvature of discontinuities
The positive and negative values (direction) of control curvature are crossed so as to easily ensure that appearance curve occurs without waveform, curvature and pressure can also be utilized
More obvious relation controls the pressure of aerofoil profile to be distributed between power distribution.And traditional nurbs curve interpolation method can only lead to
Cross at the coordinate or each data point of each data point and cut arrow to try to achieve curve, therefore for the appearance curve of partitioned representation, it is difficult to
Control its continual curvature, and be difficult in parameterized procedure controlling curve occur without waveform, its control for pressure distribution
Make the direct of curvature control that be also far from.This has fully reflected the method for the present invention compared to traditional nurbs curve interpolation
The technical advantage of method.
The parameterized results for the appearance curve that the present invention produces directly can also be used to or be integrated into CAD software ring
In border.
Although the foregoing describing the embodiment of the present invention, it will be appreciated by those of skill in the art that these
It is merely illustrative of, protection scope of the present invention is defined by the appended claims.Those skilled in the art is not carrying on the back
On the premise of from the principle of the present invention and essence, various changes or modifications can be made to these embodiments, but these are changed
Protection scope of the present invention is each fallen within modification.
Claims (4)
- A kind of 1. method based on curvature generation Pneumatic component shape, it is characterised in that it comprises the following steps：Set Step 1: obtaining the curvature of multiple positions of target shape curve and the coordinate of front and rear edge data point and cutting arrow conduct Count target component, and the original shape curve of default Pneumatic component；Step 2: carrying out nurbs curve Parameter Expression to the original shape curve, obtain expressing the original shape curve NURBS interpolation curves knot vector and control point coordinates；Step 3: calculate first derivative and second dervative of the NURBS interpolation curves relative to the knot vector, Jin Erqiu The curvature at multiple positions of the NURBS interpolation curves is obtained, wherein multiple positions of the NURBS interpolation curves and the mesh The multiple positions for marking appearance curve correspond；Step 4: judge whether the curvature at the multiple positions of NURBS interpolation curves is multiple with the target shape curve The curvature of position is consistent, when judging result is no, curvature and the section using multiple positions of the target shape curve Point vector and the first derivative try to achieve new second derivative values, and perform step 5, when judging result is to be, perform step Six；Step 5: using the knot vector, the second dervative, the target shape curve front and rear edge data point coordinate And arrow is cut, new control point coordinates is calculated, and combined with the knot vector, new NURBS interpolation curves are obtained, are replaced Former NURBS interpolation curves and return to step three；Step 6: using the NURBS interpolation curves as output result.
- 2. the method as described in claim 1, the default original shape curve is chosen from aerofoil profile public database Wing appearance curve.
- 3. method as described in claim 2, the aerofoil profile public database is NASA airfoil databases.
- 4. the method as described in claim 1, it is characterised in that the Pneumatic component includes the airfoil member of aircraft, empennage portion Part, head part.
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| CN201711078392.3A CN108038259B (en) | 2017-11-06 | 2017-11-06 | Method for generating pneumatic component appearance based on curvature |
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| CN110727995A (en) * | 2018-06-29 | 2020-01-24 | 中国航发商用航空发动机有限责任公司 | Blade shape construction method, blade, and computer device |
| CN110908338A (en) * | 2019-11-20 | 2020-03-24 | 北航（天津武清）智能制造研究院有限公司 | Blade profile spline reverse curvature correction method and system for turbine blade |
| CN111767600A (en) * | 2020-06-30 | 2020-10-13 | 春涛国际建筑有限公司 | Curved surface flower bed face brick curvature control construction method and system |
| CN113656895A (en) * | 2021-08-20 | 2021-11-16 | 中国空气动力研究与发展中心高速空气动力研究所 | Improved Parsec parameterization method for describing supercritical airfoil |
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| CN111767600A (en) * | 2020-06-30 | 2020-10-13 | 春涛国际建筑有限公司 | Curved surface flower bed face brick curvature control construction method and system |
| CN113656895A (en) * | 2021-08-20 | 2021-11-16 | 中国空气动力研究与发展中心高速空气动力研究所 | Improved Parsec parameterization method for describing supercritical airfoil |
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