CN-122021103-A - Infiltration area calculation method and system for stability analysis of water plane

CN122021103ACN 122021103 ACN122021103 ACN 122021103ACN-122021103-A

Abstract

The invention provides an infiltration area calculation method and system for stability analysis of a water plane, which comprises the steps of firstly establishing a body coordinate system and a ground coordinate system, establishing a water plane model by using modeling software, obtaining a pitch angle, a roll angle and a yaw angle of the water plane model at a certain moment, further constructing a coordinate conversion matrix, then calculating the vertical coordinate of vector coordinates of each triangular surface element under the ground coordinate system by using a specific calculation method, judging the triangular surface elements infiltrated in the water by using a specific judgment method, further calculating the total infiltration area of the water plane model, finally constructing a total infiltration area interpolation table based on the total infiltration area of the water plane model at all moments by using a multi-dimensional interpolation algorithm, further realizing stability analysis of the water plane at different moments, accurately describing the position and posture change of the water plane relative to the ground, and effectively improving the calculation accuracy of the total infiltration area.

Inventors

Ji Runjie
LIU GANG
HUANG MIAO
Mai Linrui
Zhang Duwen

Assignees

北京航空航天大学
中国特种飞行器研究所

Dates

Publication Date: 20260512
Application Date: 20251212

Claims (10)

1. The infiltration area calculation method for the stability analysis of the water plane is characterized by comprising the following steps of: Establishing a coordinate system by taking the mass center of the airplane as an origin, the direction of the aircraft nose of the airplane as a longitudinal axis, the direction of the starboard of the airplane as a transverse axis and the direction of the bottom of the airplane as a vertical axis, establishing a ground coordinate system by taking any point on the sea level as the origin, the initial motion direction of the airplane as the longitudinal axis, the starboard of the airplane and the direction parallel to the sea level as the transverse axis and the earth center as the vertical axis, and acquiring the barycentric coordinates of the water plane under the ground coordinate system; The method comprises the steps of establishing a water plane model by using modeling software, obtaining pitch angle, roll angle and yaw angle of the water plane model based on a body coordinate system at a certain moment, and constructing a coordinate conversion matrix based on the pitch angle, the roll angle and the yaw angle at the moment; The method comprises the steps of carrying out coordinate conversion and infiltration area calculation, namely calculating vector coordinates of each triangular surface element under a ground coordinate system according to the center coordinates of the triangular surface element under the body coordinate system, a coordinate conversion matrix and the center coordinates of the water plane under the ground coordinate system, comparing the vertical coordinate of each triangular surface element in the vector coordinates of each triangular surface element with a preset threshold value respectively, judging that a certain triangular surface element is infiltrated in water and reserved if the vertical coordinate of the certain triangular surface element is larger than the preset threshold value, and calculating the total infiltration area of the water plane model at the moment according to the reserved areas of all the triangular surface elements; And constructing an interpolation table and analyzing stability, namely constructing the interpolation table of the total infiltration area based on the total infiltration area of the water plane model at all moments by adopting a multi-dimensional interpolation algorithm, and inquiring the total infiltration area of the water plane at the corresponding moment in the interpolation table of the total infiltration area according to the pitch angle, the roll angle and the yaw angle in a body coordinate system at different moments and the vertical coordinate in a vector coordinate under a ground coordinate system, thereby realizing stability analysis of the water plane at different moments.
2. The method for calculating the infiltration area for the stability analysis of the water craft according to claim 1, wherein in the coordinate conversion and infiltration area calculation step, after the total infiltration area is calculated, the cross-sectional point coordinates of the water craft model under the body coordinate system are also obtained, the abscissa of the cross-sectional point coordinates is compared with the abscissa of the central coordinate of the triangular surface element under the body coordinate system, if the abscissa of the central coordinate of a certain triangular surface element is greater than the abscissa of the cross-sectional point coordinates, the triangular surface element is judged to be positioned in front of the cross-sectional point and infiltrated in water, and the infiltration area of the front of the water craft cross-sectional point is calculated according to the area of all the triangular surface elements which are reserved and positioned in front of the cross-sectional point.
3. The method for calculating the infiltration area for stability analysis of a seaplane according to claim 2, wherein the speed of the seaplane is also obtained, the hydrodynamic lift force is calculated according to the infiltration area, the speed and the water density of the front part of the fracture point of the seaplane model, and then the average dynamic pressure of the bottom of the airplane body is calculated according to the hydrodynamic lift force, the infiltration area of the front part of the fracture point and the pitch angle of the seaplane.
4. The method for calculating the infiltration area for stability analysis of a seaplane according to claim 3, wherein the average water flow velocity of the bottom of the body is calculated according to the average dynamic pressure, the navigational speed and the water density, and the dynamic friction resistance of the water is calculated according to the average water flow velocity and the infiltration area in front of the break point.
5. The method according to claim 1, wherein in the step of meshing and parameter calculation, the modeling software includes CAD software and 3D drawing software, and the numerical calculation software includes MATLAB and finite element analysis software.
6. A system for calculating the infiltration area for analyzing the stability of a water plane is characterized by comprising a coordinate system building module, a grid division and parameter calculation module, a coordinate conversion and infiltration area calculation module and an interpolation table building and stability analysis module which are connected in sequence, The system comprises a coordinate system establishing module, a ground coordinate system establishing module, a control module and a control module, wherein the coordinate system establishing module establishes a body coordinate system by taking an aircraft centroid as an origin, a aircraft nose direction as a longitudinal axis, a aircraft starboard direction as a transverse axis and a aircraft bottom direction as a vertical axis, establishes a ground coordinate system by taking any point on a sea level as the origin, an aircraft initial motion direction as the longitudinal axis, a direction parallel to the sea level as the transverse axis and a geocenter as the vertical axis, and acquires the gravity center coordinate of the water aircraft under the ground coordinate system; The system comprises a grid dividing and parameter calculating module, a finite element grid dividing and parameter calculating module, a numerical value calculating module, a three-dimensional coordinate calculating module and a three-dimensional coordinate calculating module, wherein the grid dividing and parameter calculating module establishes a water plane model by using modeling software, acquires a pitch angle, a roll angle and a yaw angle of the water plane model based on a body coordinate system at a certain moment, and constructs a coordinate conversion matrix based on the pitch angle, the roll angle and the yaw angle at the moment; The coordinate conversion and infiltration area calculation module calculates vector coordinates of each triangular surface element under the ground coordinate system according to the center coordinates of the triangular surface element under the body coordinate system, the coordinate conversion matrix and the gravity center coordinates of the water plane under the ground coordinate system, compares the vertical sub-coordinates in the vector coordinates of each triangular surface element with a preset threshold value respectively, judges that a certain triangular surface element is infiltrated in water and reserved if the vertical sub-coordinates of the certain triangular surface element are larger than the preset threshold value, and calculates the total infiltration area of the water plane model at the moment according to the areas of all reserved triangular surface elements; The interpolation table construction and stability analysis module is used for constructing a total infiltration area interpolation table based on the total infiltration area of the water plane model at all moments and adopting a multi-dimensional interpolation algorithm, and inquiring the total infiltration area of the water plane at the corresponding moment in the total infiltration area interpolation table according to the pitch angle, the roll angle and the yaw angle in the body coordinate system at different moments and the vertical coordinate in the vector coordinate under the ground coordinate system, thereby realizing stability analysis of the water plane at different moments.
7. The system according to claim 6, wherein the coordinate transformation and infiltration area calculation module further obtains a cross-sectional point coordinate of the water craft model under the body coordinate system after calculating the total infiltration area, compares an abscissa of the cross-sectional point coordinate with an abscissa of a center coordinate of the triangle surface element under the body coordinate system, and if the abscissa of the center coordinate of a certain triangle surface element is greater than the abscissa of the cross-sectional point coordinate, determines that the triangle surface element is located in front of the cross-sectional point and is infiltrated in water and retains the cross-sectional point, and calculates an infiltration area of the front of the water craft cross-sectional point according to the retained area of all triangle surface elements located in front of the cross-sectional point.
8. The system for analyzing stability of a seaplane of claim 7, further comprising obtaining a speed of the seaplane, calculating a hydrodynamic lift from the wetted area in front of the fracture point of the model of the seaplane, the speed of the seaplane, and the water density, and calculating an average dynamic pressure of the bottom of the hull from the hydrodynamic lift, the wetted area in front of the fracture point, and the pitch angle of the seaplane.
9. The system for calculating the wetted area of the stability analysis of the seaplane of claim 8, wherein the average water velocity of the bottom of the body is calculated based on the average dynamic pressure, the navigational speed and the water density, and the hydrodynamic frictional resistance of the water is calculated based on the average water velocity and the wetted area in front of the break point.
10. The wetted area calculation system for the stability analysis of the seaplane of claim 6, wherein the modeling software comprises CAD software and 3D cartography software, and the numerical calculation software comprises MATLAB and finite element analysis software.

Description

Infiltration area calculation method and system for stability analysis of water plane Technical Field The invention relates to the technical field of aviation engineering, in particular to a method and a system for calculating an infiltration area for analyzing stability of a water plane. Background When the water plane slides on the water surface, unique hydrodynamic phenomena can be generated due to the special ship-shaped fuselage design. The accurate calculation of the wetting area of the water plane is important to optimizing the design and the performance of the water plane. The infiltration area refers to the total surface area of the water plane contacted with water when the water plane slides on the water surface, and the water plane directly influences key performance indexes such as resistance, stability, operability and the like. The traditional infiltration area calculation method is based on a large number of hydrodynamic tests and is estimated through a semi-empirical engineering calculation formula. These methods take mainly into account two important parameters, the keel line infiltration length (KEEL WETTED LENGTH) and the bilge line infiltration length (CHINE WETTED LENGTH). According to factors such as different pitch angles, different inclined rising angles and different drainage volumes, a specific formula is adopted to calculate the two length values, and then the average infiltration length is comprehensively obtained by combining the influence of water flow splashing of the machine head part. Further, the average wetted length is used to estimate the wetted area. However, the prior art has some problems in practical application, namely 1) the application range is limited, that is, the traditional calculation method is only suitable for a specific parameter interval (for example, the pitch angle, the ramp angle and the drainage volume need to meet certain conditions), and the calculation result can deviate from the practical situation seriously beyond the range. 2) The error is large, and because the method is based on a semi-empirical formula, although a plurality of factors are considered, complex hydrodynamic phenomena cannot be completely and accurately reflected, so that a certain error exists in a calculation result. 3) The special case is mishandled in that when some critical parameters approach a limit value (e.g. the angle approaches 0 or a maximum value), the calculation formula may produce a result that is not physically meaningful (e.g. negative or abnormally large positive), which is clearly not the case. In view of the foregoing, there is a great need to develop a more accurate computing method that can accommodate a wider range of operating conditions to improve the accuracy and reliability of the design of a seaplane. The new method can better simulate the real hydrodynamic environment and provide the infiltration area calculation result which is more close to the actual situation, thereby providing powerful support for the optimal design of the seaplane. Disclosure of Invention Aiming at the problems of large error, narrow application range, slow calculation speed, poor real-time performance and the like in the existing calculation process of the infiltration area of the seaplane, the invention provides the infiltration area calculation method for the stability analysis of the seaplane, which can accurately calculate the infiltration area of the seaplane, improves the calculation precision, effectively improves the calculation efficiency and has remarkable rapidity, real-time performance and accuracy. The invention also relates to a infiltration area calculation system for analyzing the stability of the water plane. The technical scheme of the invention is as follows: The infiltration area calculation method for the stability analysis of the water plane is characterized by comprising the following steps of: Establishing a coordinate system by taking the mass center of the airplane as an origin, the direction of the aircraft nose of the airplane as a longitudinal axis, the direction of the starboard of the airplane as a transverse axis and the direction of the bottom of the airplane as a vertical axis, establishing a ground coordinate system by taking any point on the sea level as the origin, the initial motion direction of the airplane as the longitudinal axis, the starboard of the airplane and the direction parallel to the sea level as the transverse axis and the earth center as the vertical axis, and acquiring the barycentric coordinates of the water plane under the ground coordinate system; The method comprises the steps of establishing a water plane model by using modeling software, obtaining pitch angle, roll angle and yaw angle of the water plane model based on a body coordinate system at a certain moment, and constructing a coordinate conversion matrix based on the pitch angle, the roll angle and the yaw angle at the moment; The method comprises the steps of c