CN111274728B - Method for analyzing hydro-elastic response of netting and floating body coupling - Google Patents
Method for analyzing hydro-elastic response of netting and floating body coupling Download PDFInfo
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Abstract
The invention relates to a method for analyzing the coupling hydro-elastic response of netting and a floating body, which adopts a mesh ultra-cell method to establish a finite element model for the netting; performing modal analysis on the structure of the culture equipment, and considering the coordinated deformation among the main floating body, the slender floating body and the netting when performing the modal analysis to obtain the corresponding stress and strain under each modal; obtaining the wave flow load of the netting by a mesh ultra-unit method; and establishing a motion equation of the cultivation equipment to obtain a main modal coordinate of the cultivation equipment structure, and calculating the total stress, strain and motion response of the cultivation equipment after modal superposition according to the main coordinate. The invention can not calculate the stress of each mesh any more by the hypercell method, thus greatly reducing the calculation workload; by introducing the entity rate, the calculation precision of the fluid load of the netting is improved; through the coupling analysis of the floating body and the net, the mutual influence between the net and the floating body is considered when the motion response is calculated, so that the accuracy of the calculation result is greatly improved.
Description
Technical Field
The invention relates to the technical field of ship three-dimensional hydro-elasticity analysis and calculation methods, in particular to a netting and floating body coupling hydro-elasticity response analysis method.
Background
Fishery breeding is concerned by many countries and enterprises, and fishery breeding equipment formed by combining floating bodies and netting is also greatly developed. The hydro-elasticity analysis method of a pure floating body is mature, but the net structure has a great difference from the traditional floating body due to the special form of the net structure. The netting is woven by slender net wires, and has thousands of meshes, even hundreds of thousands of meshes and millions of meshes, and the net wires of the netting are low in rigidity. The wave diffraction theory is no longer suitable for calculating the hydrodynamic load of the netting, and a calculation method suitable for the characteristics of the netting needs to be provided. Meanwhile, the netting and the floating body are connected together through the connecting piece, the netting and the floating body can deform under the action of waves and ocean currents, and the coordinated deformation between the netting and the floating body needs to be considered in calculation and analysis. Therefore, in order to analyze the coupling dynamic characteristics of the floating body and the net, a method for analyzing the coupling hydro-elastic response of the net and the floating body needs to be provided.
Disclosure of Invention
The applicant provides a netting and floating body coupling hydro-elastic response analysis method aiming at the defects in the prior art, optimizes a calculation method of netting wave flow load according to the structural characteristics of netting, and simultaneously comprehensively considers the coordination deformation factors between netting and floating body in the modal analysis process, thereby improving the calculation efficiency and the accuracy of calculation results.
The technical scheme adopted by the invention is as follows:
a netting and floating body coupling hydro-elastic response analysis method selects cultivation equipment as a calculation model of the netting and the floating body, and the cultivation equipment has the following structure: the floating structure comprises a frame body with a polygonal cross section and a main floating body with the main dimension larger than or equal to the wavelength, wherein the longitudinal section of the main floating body is of a T-shaped structure and is positioned at the center of the frame body structure, and a circle of the circumference of the main floating body is connected with a corresponding outer side upright post into a whole through a plurality of slender floating bodies with the main dimension smaller than the wavelength; the bottom surface and each side surface of the frame body are respectively provided with a netting;
the coupling hydro-elastic response analysis method comprises the following specific steps: establishing a finite element model of the cultivation equipment, wherein a mesh ultra-cell method is adopted when the finite element model is established for the netting; performing modal analysis on the structure of the culture equipment, and considering the coordinated deformation among the main floating body, the slender floating body and the netting when performing the modal analysis to obtain the corresponding stress and strain under each modal; calculating the hydrodynamic coefficient and the wave exciting force of the main floating body through a potential flow theory, obtaining the wave flow load of the slender floating body through a Morrison equation, and obtaining the wave flow load of the netting through a mesh ultra-unit method; and establishing a motion equation of the cultivation equipment, substituting the obtained hydrodynamic force coefficient and each wave flow load into the motion equation, solving to obtain a modal main coordinate of the structure of the cultivation equipment, and calculating the total stress, strain and motion response of the cultivation equipment after modal superposition according to the main coordinate.
The further technical scheme is as follows:
the frame body is provided with a plurality of outer side upright columns which are arranged along the vertical direction, the outer side upright columns are respectively positioned at the vertexes of the polygon, and the upper part and the lower part between the adjacent outer side upright columns are respectively connected into a whole through an upper cross rod, a lower cross rod and an outer side inclined strut; the main body longitudinal section becomes T shape structure, and it includes the big footpath base in bottom, and its middle part is connected with the center pillar who extends along vertical direction, center pillar is promptly through long and thin body: the horizontal upper supporting rod, the lower inclined strut and the inclined space inclined strut are connected with the outer side upright post.
Calculating the wave flow load of the netting by adopting a mesh ultra-cell method:
the method comprises the following steps: calculating entity rate of netting
Wherein l w Is the center-to-center spacing of the network cables, d w Is the diameter of the mesh wire;
step two: reynolds number of calculation netting
Wherein U is rel The relative speed between the water flow and the netting, and v is the kinematic viscosity coefficient of the fluid;
step three: calculating the resistance coefficient and the lift coefficient of the netting according to the entity rate, the Reynolds number and the included angle theta between the netting and water particles: coefficient of resistance C D (Sn, re, theta), coefficient of lift C L (Sn,Re,θ)；
The net superunit is subjected to the fluid resistance of
Lift force is
Where ρ is the fluid density, C D And C L Respectively the obtained drag coefficient and lift coefficient, A is the area of each netting super unit, n D And n L Respectively the direction vectors of resistance and lift; further obtaining the wave current load of the netting; then, calculating buoyancy force borne by the cultivation equipment according to the motion conditions of the floating body and the netting; parameters such as a floating body, a netting mass array, an additional mass array, a radiation damping array, wave load borne by the floating body, wave current load borne by the slender rod piece, wave current load borne by the netting, buoyancy force borne by the culture equipment and the like are brought into a motion equation;
solving a motion equation by using a numerical calculation method to obtain a modal principal coordinate of the cultivation equipment; and calculating the total motion response, stress and strain of the culture equipment through the main coordinates and the structural modal information.
The main dimension of the slender floating body is specifically less than one tenth of wavelength; the netting is a net-shaped structure woven by metal materials or composite materials.
The invention has the following beneficial effects:
the invention can not calculate the stress of each mesh any more by the superunit method, thus greatly reducing the calculation workload; by introducing the entity rate, the calculation precision of the fluid load of the netting is improved; through the coupling analysis of the floating body and the net, the mutual influence between the net and the floating body is considered when the motion response is calculated, and therefore the accuracy of the calculation result is greatly improved.
Drawings
FIG. 1 is a flow chart of an analytical method of the present invention.
FIG. 2 is a top view of an embodiment of the farming equipment of the present invention.
Fig. 3 isbase:Sub>A cross-sectional view taken alongbase:Sub>A-base:Sub>A in fig. 2.
Fig. 4 is a cross-sectional view taken along section B-B of fig. 3.
Fig. 5 is a cross-sectional view taken along section C-C in fig. 2.
Fig. 6 is a time course curve of the fluid load of the netting provided by the analysis method of the present invention.
Wherein: 1. an outer column; 2. an upper cross bar; 3. a central upright post; 4. an upper stay bar; 5. a space diagonal bracing; 6. a lower diagonal brace; 7. a main float; 8. a lower cross bar; 9. an outer diagonal brace; 10. hooking; 11. netting; 12. and (5) cultivating equipment.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
In the method for analyzing the coupling hydro-elastic response of the netting and the floating body, the method for analyzing the coupling hydro-elastic response comprises the following specific steps: as shown in fig. 1, establishing a finite element model of the cultivation equipment 12, wherein a mesh ultra-cell method is adopted when establishing the finite element model for the netting 11; as shown in fig. 2-5, the structure of the cultivation equipment 12 is subjected to modal analysis, and the coordinated deformation among the main floating body 7, the elongated floating body and the netting 11 is considered during the modal analysis to obtain corresponding stress and strain under each modal;
calculating the hydrodynamic coefficient and the wave exciting force of the main floating body 7 through a potential flow theory, obtaining the wave flow load of the slender floating body through a Morrison equation, and obtaining the wave flow load of the netting 11 through a mesh ultra-unit method;
and establishing a motion equation of the culture equipment 12, substituting the obtained hydrodynamic force coefficient and each wave current load into the motion equation, solving to obtain a modal main coordinate of the structure of the culture equipment 12, and calculating the total stress, strain and motion response of the culture equipment 12 after modal superposition according to the main coordinate.
In fig. 1, "large floating body" is the "main floating body" of this embodiment, and "floating body and net curtain" are the "cultivation equipment" of this embodiment.
As shown in fig. 2-5, the cultivation equipment 12 comprises a frame body with a polygonal cross section and a main floating body 7 with a main dimension larger than or equal to the wavelength, wherein the longitudinal section of the main floating body 7 is in a T-shaped structure and is positioned at the center of the frame body structure, and a circle of the circumference of the main floating body 7 is connected with the corresponding outer side upright post 1 into a whole through a plurality of slender floating bodies with main dimensions smaller than the wavelength; each side surface and the bottom surface of the frame body are provided with netting 11;
the frame body is provided with a plurality of outer side upright posts 1 arranged along the vertical direction, the outer side upright posts 1 are respectively positioned at the vertexes of a polygon, and the upper part and the lower part between the adjacent outer side upright posts 1 are respectively connected into a whole through an upper cross rod 2, a lower cross rod 8 and an outer side inclined strut 9;
the main floating body 7 has a T-shaped longitudinal section and comprises a bottom large-diameter base, the middle part of the base is connected with a central upright post 3 extending along the vertical direction, and the central upright post 3 is connected with the outer upright posts 1 through a slender floating body, namely a horizontal upper support rod 4, a lower inclined support 6 and an inclined space inclined support 5.
The netting 11 is connected to the frame rod through a hook 10, the central upright post 3 and the lower inclined strut 6 are welded with the large floating body 7, and the connection mode of the slender floating bodies is also welded. So that there is a coordinated deformation between the elongated buoyant body and the main buoyant body 7, and a coordinated deformation between the 11 netting and the elongated buoyant body is generated by the 10 hooks.
Calculating the wave flow load of the netting 11 by adopting a mesh ultra-cell method:
the method comprises the following steps: calculating entity rate of netting 11
Wherein l w Is the center-to-center spacing of the network cables, d w Is the diameter of the mesh wire;
step two: calculating the Reynolds number of the netting 11
Wherein U is rel The relative speed between the water flow and the netting, and v is the kinematic viscosity coefficient of the fluid;
step three: calculating the resistance coefficient and the lift coefficient of the netting according to the entity rate, the Reynolds number and the included angle theta between the netting 11 and water mass points: coefficient of resistance C D (Sn, re, theta), coefficient of lift C L (Sn,Re,θ)；
The superunit of the netting 11 is subjected to a fluid resistance of
The lift force is
Where ρ is the fluid density, C D And C L Respectively, the obtained drag coefficient and lift coefficient, A is the area of the superunit of each netting 11, n D And n L Respectively are the direction vectors of resistance and lifting force; thereby obtaining the wave current load of the netting 11; fig. 6 is a graph showing the time course of the fluid load of the net 11 according to the analysis method of the present embodiment.
Then, according to the motion conditions of the floating body and the netting 11, calculating the buoyancy force borne by the culture equipment 12; parameters such as a mass array, an additional mass array and a radiation damping array of the floating body and the netting 11, wave load borne by the floating body, wave current load borne by the slender rod piece, wave current load borne by the netting 11, buoyancy borne by the culture equipment 12 and the like are brought into a motion equation;
solving a motion equation by using a numerical calculation method to obtain a modal principal coordinate of the culture equipment 12; the total motion response, stress and strain of the culture equipment 12 are calculated through the main coordinates and the structural modal information, and when the motion response of the culture equipment 12 is calculated, the coordinated deformation factors between the main floating body 7 and the net coat 11, between the main floating body 7 and the slender floating body and between the slender floating body and the net coat 11 are considered, and the factors such as elastic coefficients and the like related to the coordinated deformation are taken as calculation bases, so that the precision of the calculation result is greatly improved.
The above description is intended to be illustrative and not restrictive, and the scope of the invention is defined by the appended claims, which may be modified in any manner within the scope of the invention.
Claims (3)
1. A method for analyzing the hydro-elastic response of netting and floating body coupling is characterized by comprising the following steps:
selecting breeding equipment (12) as a calculation model of the netting and the floating body, wherein the structure of the breeding equipment (12) is as follows: the floating structure comprises a frame body with a polygonal cross section and a main floating body (7) with the main dimension larger than or equal to the wavelength, wherein the longitudinal section of the main floating body (7) is of a T-shaped structure and is positioned at the center of the structure of the frame body, and a circle of the circumference of the main floating body (7) is connected with a corresponding outer side upright post (1) into a whole through a plurality of slender floating bodies with the main dimension smaller than the wavelength; the bottom surface and each side surface of the frame body are provided with netting (11);
the coupling hydro-elastic response analysis method comprises the following specific steps:
establishing a finite element model of the breeding equipment (12), wherein a mesh ultra-cell method is adopted when the finite element model is established for the netting (11);
performing modal analysis on the structure of the culture equipment (12), and considering the coordinated deformation among the main floating body (7), the slender floating body and the netting (11) during the modal analysis to obtain the corresponding stress and strain under each modal;
calculating the hydrodynamic coefficient and the wave exciting force of the main floating body (7) through a potential flow theory, obtaining the wave flow load of the slender floating body through a Morrison equation, and obtaining the wave flow load of the netting (11) through a mesh ultra-unit method;
and establishing a motion equation of the cultivation equipment (12), substituting the obtained hydrodynamic coefficient and each wave current load into the motion equation, solving to obtain a modal main coordinate of the structure of the cultivation equipment (12), and calculating the total stress, strain and motion response of the cultivation equipment (12) after modal superposition according to the main coordinate.
2. The method for analyzing the hydro-elastic response of the coupling of the netting and the floating body according to claim 1, wherein: the frame body is provided with a plurality of outer side upright posts (1) arranged along the vertical direction, the outer side upright posts (1) are respectively positioned at the vertexes of a polygon, and the upper part and the lower part between the adjacent outer side upright posts (1) are respectively connected into a whole through an upper cross rod (2), a lower cross rod (8) and an outer side inclined strut (9);
the longitudinal section of the main floating body (7) is of a T-shaped structure, the T-shaped structure comprises a bottom large-diameter base, the middle part of the bottom large-diameter base is connected with a central upright post (3) extending in the vertical direction, the central upright post (3) is connected with an outer upright post (1) through a slender floating body, and the slender floating body structure comprises a horizontal upper support rod (4), a lower inclined support (6) and an inclined space inclined support (5).
3. The method for analyzing the hydro-elastic response of the coupling of the netting and the floating body as claimed in claim 1 or 2, wherein: calculating the wave flow load of the netting (11) by adopting a net sheet hypercell method:
the method comprises the following steps: calculating the entity rate of the netting (11)
Wherein l w Is the center-to-center distance of the network cable, d w Is the diameter of the mesh wire;
step two: calculating the Reynolds number of the netting (11)
Wherein U is rel The relative speed between the water flow and the netting, and v is the kinematic viscosity coefficient of the fluid;
step three: according to the entity rate, the Reynolds number and the included angle theta between the netting (11) and water mass points, calculating the resistance coefficient and the lift coefficient of the netting: coefficient of resistance C D (Sn, re, theta), coefficient of lift C L (Sn,Re,θ)；
The superunit of the netting (11) is subjected to a fluid resistance of
Lift force is
Where ρ is the fluid density, C D And C L Respectively the obtained drag coefficient and lift coefficient, A is the area of the superunit of each netting (11), n D And n L Respectively are the direction vectors of resistance and lifting force; thereby obtaining the wave current load of the netting (11);
then, calculating the buoyancy force borne by the cultivation equipment (12) according to the motion conditions of the floating body and the netting (11); bringing the floating body, the mass array of the netting (11), the additional mass array, the radiation damping array, the wave load borne by the floating body, the wave current load borne by the slender rod piece, the wave current load borne by the netting (11) and the buoyancy borne by the culture equipment (12) into a motion equation; solving a motion equation by using a numerical calculation method to obtain a modal principal coordinate of the cultivation equipment (12); and calculating the total motion response, stress and strain of the culture equipment (12) through the main coordinates and the structural modal information.
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| CN113203542A (en) * | 2021-05-07 | 2021-08-03 | 中国船舶科学研究中心 | Netting hydrodynamic test device and test method |
| CN114894437B (en) * | 2022-06-07 | 2023-03-17 | 上海交通大学 | Test device for researching coupling hydrodynamic characteristics of stand column-netting structure |
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