CN106886666B - Boundary layer grid solving method for lift-drag ratio of underwater glider under different attack angles - Google Patents
Boundary layer grid solving method for lift-drag ratio of underwater glider under different attack angles Download PDFInfo
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- CN106886666B CN106886666B CN201710221791.4A CN201710221791A CN106886666B CN 106886666 B CN106886666 B CN 106886666B CN 201710221791 A CN201710221791 A CN 201710221791A CN 106886666 B CN106886666 B CN 106886666B
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Abstract
The invention provides a boundary layer grid solving method for the lift-drag ratio of an underwater glider under different attack angles, and aims to determine the optimal sliding angle of the underwater glider, obtain the resistance and the lift force under different attack angles and provide theoretical support for selection of a control system and a power source of the subsequent underwater glider. Finally, the accuracy of boundary layer grid numerical simulation is verified through experiments, and the obtained coincidence condition is good. The analysis method can be popularized to other series of underwater motion machines, saves the calculation period compared with the traditional complex formula derivation, improves the calculation efficiency by more than two times, and can effectively predict and solve the problems of the efficiency of the underwater machines and the like. And step A, simplifying the physical model of the underwater glider. And B, creating a fluid external domain model of the underwater glider. And C, creating a boundary layer grid model of the underwater glider. And D, carrying out numerical solution calculation on the lift-drag ratio of the underwater glider under different attack angles. And E, carrying out data result post-processing. The method is applied to the effective solution of the lift-drag ratio of the underwater glider.
Description
Technical Field
The invention belongs to the technical field of target characteristics and identification, and relates to a boundary layer grid solving method for the lift-drag ratio of an underwater glider under different attack angles.
Background
The underwater glider is a novel underwater cableless robot, the power source of the underwater glider is net buoyancy of seawater, and the underwater glider can slowly slide along a zigzag track in the seawater by virtue of the net buoyancy. Because it has no thrust system, it has the characteristics of low noise, long endurance, long sliding distance and the like. Various sensors can be installed on the underwater glider to be used as assistance, and the underwater glider plays a vital role in the aspects of ocean big data collection, military investigation, ocean environment and resource monitoring and the like. In recent years, numerical simulation of underwater gliders mainly comprises calculation of lift-drag ratio, larger lift force, smaller resistance and larger lift-drag ratio can enable the gliders to have better endurance, and hydrodynamic efficiency is improved. Therefore, the invention provides a numerical solving method for lift-drag ratios of underwater gliders at different attack angles, and aims to determine the optimal sliding angle of the underwater glider, obtain resistance and lift at different attack angles and provide theoretical support for selection of a control system and a power source of the subsequent underwater glider.
Disclosure of Invention
The boundary layer grid solving method for the underwater glider lift-drag ratio under different attack angles aims to solve the problem that the accuracy of solving the problem of the gliding efficiency of the underwater glider by using the existing calculating method is poor.
A boundary layer grid solving method for the lift-drag ratio of underwater gliders under different attack angles is realized according to the following steps:
step A, simplifying a physical model of the underwater glider:
firstly, a model is simplified in an ICEM, a tail rudder is repaired in the simplification process, and a hook before release and a communication system which have small influence on fluid simulation are removed, as shown in the figure I.
And B, creating a fluid external domain of the underwater glider as follows:
and establishing a cylindrical fluid domain for the underwater glider by using ICEM meshing software, wherein the front part of the fluid domain is of a semicircular structure similar to the head part of the underwater glider, as shown in the figure II, meshing the fluid domain to generate an unstructured grid with boundary layer meshes, and carrying out mesh encryption treatment on the boundary layer, as shown in the figure III.
Step C, determining numerical simulation conditions of the underwater glider:
leading the underwater glider grid into Fluent, respectively setting boundary conditions as an inlet boundary condition, an outlet boundary condition and a wall boundary condition according to a turbulence model obtained by early derivation and the actual working condition of the underwater glider, setting a seawater fluid medium, and respectively carrying out numerical simulation on a commonly used attack angle of-10 degrees to 10 degrees on the underwater glider. And carrying out 6000 steps of iterative operation, setting a monitor, and carrying out analog simulation to obtain flow field data.
And D, carrying out numerical solution calculation on the lift-drag ratio of the underwater glider under different attack angles.
And E, post-processing data results, summarizing the lift force and resistance results obtained by numerical analysis to obtain a lift-drag ratio, fitting a curve of the lift-drag ratio changing along with the attack angle to obtain a comparison curve graph, and comparing to obtain the optimal sliding angle of the lift-drag ratio.
The invention has the following effects:
according to the method, the optimal gliding efficiency of the underwater glider is obtained through a fluid numerical simulation method, the lift-drag ratio under different attack angles is obtained, the coincidence condition is better through comparison of a simulation value and an experimental value, and the accuracy of a numerical solving method is verified. The analysis method can be popularized to other series of underwater motion machines, saves the calculation period compared with the traditional complex formula derivation, can improve the calculation efficiency by more than two times, saves manpower and material resources compared with the traditional experiment, is more economic, and can effectively predict and solve the problems of the efficiency of the underwater machine and the like.
Drawings
FIG. 1 is a simplified schematic of an underwater glider;
FIG. 2 is a schematic view of an underwater glider fluid field;
FIG. 3 is a schematic diagram of boundary layer meshes;
fig. 4 is a pressure field distribution.
Detailed Description
A boundary layer grid solving method for the lift-drag ratio of underwater gliders under different attack angles is realized according to the following steps:
the method takes computer simulation as a main research means, and mainly comprises numerical modeling and CFD simulation, wherein the CFD simulation is divided into grid division (preprocessing), calculation and solution, and result analysis (postprocessing);
step A, simplifying an underwater glider model:
firstly, a model is simplified in an ICEM, the simplification of the model can not only improve the grid quality and improve the calculation precision, but also greatly reduce the calculation time, is an essential link in simulation analysis, and repairs a tail rudder and removes a hook before release and a communication system in the simplification.
And B, creating a fluid external domain of the underwater glider as follows:
because the underwater glider moves relative to the outer flow field, assuming the underwater glider is stationary, the fluid flows at a speed relative to the speed at which the underwater glider glides. A cylindrical fluid domain is established for the underwater glider by using ICEM meshing software, the front part of the fluid domain is of a semicircular structure similar to the head of the underwater glider, meshing is carried out on the fluid domain to generate an unstructured grid with boundary layer meshes, and mesh encryption processing is carried out on a boundary layer, wherein the number of the meshes is 210 thousands, and the number of the nodes is 45 thousands as shown in the figure III.
Step C, determining numerical simulation conditions of the underwater glider:
the assumed conditions are: seawater is an incompressible fluid, and the influence of waves is not considered. The sea water density and temperature are kept constant, i.e. at 15 deg.C, the density isρ=1025.0kg/m3Dynamic viscosity coefficient ofμ=1.219×10-3kg/m·s-1. The surface curvature of the earth and the earth's rotation are no longer considered, and the seawater is considered to be a plane. The underwater glider is regarded as a rigid body with unchanged volume by the elastic deformation of the underwater glider shell under the slight seawater pressure.
According to a turbulence model obtained by early derivation and the actual working condition of the underwater glider, boundary conditions are respectively set as an inlet boundary condition, an outlet boundary condition and a wall boundary condition, a seawater fluid medium is set, and the common-10-degree to 10-degree attack angle of the underwater glider is respectively subjected to numerical simulation.
And D, carrying out numerical solution calculation on the lift-drag ratio of the underwater glider under different attack angles.
D1, opening fluid mechanics calculation software, importing a Grid model File, namely, the shuixiahuxianganji, mesh through an Import in the File, and carrying out Grid quality inspection through Grid;
d2, setting parameters of a Solver Solver through Define, and adopting three-dimensional steady fluid flow setting;
d3, setting material properties by Define, and mainly giving out the viscosity and density parameters of the seawater to be researched;
step D4, model Models are set by Define, selecting the bandRNGk-εThe wall function is a standard wall function, and the rest is kept as default;
and D5, setting a Define-Boundary Conditions, selecting a velocity entry velocity-inlet, and specifically setting as shown in the table when the angle of attack is 0 degrees and the velocity is 0.5 m/s. The speed of a Y axis is properly adjusted according to different attack angles, when a glider glides, the attack angle does not exceed 10 degrees generally, the Y-axis component of the glider is calculated and is brought into Y-Velocity (m/s), a free outflow flow is selected at an outlet, the surface of the aircraft with the wall surface without the sliding wall surface is a static wall surface without the sliding wall surface, and the surface roughness is 0;
step D6, setting a monitor plane;
step D7, setting the residual to 10-5Initializing a flow field, performing iterative computation, prompting the convergence of the numerical value computation of the flow field after 6000 steps of iteration, and obtaining a computation result.
And E, carrying out data result post-processing, summarizing the lift force and resistance results obtained by numerical analysis to obtain a lift-drag ratio, fitting a curve of the lift-drag ratio changing along with the attack angle to obtain a comparison curve graph, and obtaining the optimal glide angle of the lift-drag ratio through comparison, wherein the lift-drag ratio is the maximum when the attack angle of the underwater glider is 8 degrees and the highest glide efficiency is obtained at the moment.
The effect of the embodiment is as follows:
the numerical calculation result analysis of the invention shows that the underwater glider has the highest drag-drag ratio when the attack angle is 8 degrees, the gliding efficiency of the underwater glider is the highest, the accuracy of the boundary layer grid numerical simulation is verified through experiments, and the obtained coincidence condition is better. The analysis method can be popularized to other series of underwater motion machines, saves the calculation period compared with the traditional complex formula derivation, improves the calculation efficiency by more than two times, saves manpower and material resources compared with the traditional experiment, and can effectively predict and solve the problems of the efficiency of the underwater machine and the like.
Claims (2)
1. A boundary layer grid solving method for the lift-drag ratio of underwater gliders at different attack angles is characterized in that the distribution condition of the outer flow field of the underwater glider is obtained by the boundary layer grid solving method, the lift-drag ratio of the underwater gliders at different attack angles is obtained, the accuracy of the numerical solving method is verified by comparing a simulation value with a test value,
the solving method is realized according to the following steps:
step A, simplifying a physical model of the underwater sliding machine:
firstly, the model is simplified, the tail rudder is repaired during the simplification, the hook before release and the communication system which have small influence on fluid simulation are removed,
step B, establishing an underwater glider boundary layer grid model:
establishing a cylindrical fluid domain for the underwater glider, wherein the front part of the fluid domain is a semicircular structure similar to the head part of the underwater glider, carrying out grid division on the fluid domain to generate an unstructured grid with a boundary layer grid, carrying out grid encryption treatment on the boundary layer,
step C, determining numerical solving conditions of the underwater glider:
respectively setting boundary conditions and seawater fluid media according to a turbulence model obtained by early derivation and the actual working condition of the underwater glider, respectively carrying out boundary layer grid model numerical solution on the underwater glider at a commonly used attack angle of-10 degrees to 10 degrees,
step D, 6000 steps of iterative solution operation of the lift-drag ratio of the underwater glider under different attack angles are carried out,
and E, post-processing a data result, and fitting a curve of the lift-drag ratio parameter changing along with the attack angle obtained by solving the boundary layer grids to obtain the optimal sliding angle.
2. The boundary layer grid solving method for the lift-drag ratio of the underwater glider under different attack angles according to claim 1, wherein the lift coefficient and the drag coefficient are increased along with the increase of the attack angle, when the sliding angle is 8 degrees, the lift-drag ratio is the largest, the sliding efficiency is the highest, and the result is consistent with the conclusion obtained by experiments, so that the accuracy of the boundary layer grid numerical solving method is verified.
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| CN109948269B (en) * | 2019-03-27 | 2020-11-03 | 湖南科技大学 | Hexahedral mesh division method for armored umbilical cable model |
| CN110309571B (en) * | 2019-06-24 | 2022-02-11 | 西北工业大学 | Wing body fusion underwater glider external shape optimization method based on radial basis function model |
| CN110276131B (en) * | 2019-06-24 | 2022-07-26 | 西北工业大学 | Wing body fusion underwater glider appearance optimization method based on polynomial response surface model |
| CN112947502B (en) * | 2021-03-04 | 2022-11-08 | 中国科学院自动化研究所 | Flexible bionic web underwater motion control method and system |
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Inventor after: Yu Xiaodong Inventor after: Quan Zhen Inventor after: Liu Guoliang Inventor after: Kong Xiangbin Inventor after: Zhang Yanqin Inventor after: Cheng Haikuo Inventor after: Guo Lili Inventor before: Zhang Yanqin Inventor before: Quan Zhen Inventor before: Liu Guoliang Inventor before: Kong Xiangbin Inventor before: Yu Xiaodong Inventor before: Cheng Haikuo Inventor before: Guo Lili |
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