CN109101752A - A kind of complexity hydraulic structure partial structurtes natural frequency of vibration calculation method - Google Patents
A kind of complexity hydraulic structure partial structurtes natural frequency of vibration calculation method Download PDFInfo
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Abstract
The present invention relates to a kind of complicated hydraulic structure partial structurtes natural frequency of vibration calculation methods.The present invention can high-precision analog part monomer structure practical stiffness, the actual participation quality of its vibration shape of energy high-precision analog again, complicated hydraulic structure partial structurtes natural frequency of vibration solving precision can be greatly improved, carrying out complicated hydraulic structure dynamic design using the present invention can avoid generating high vibration and resonance, guarantee that hydraulic structure inherently safe, instrument and equipment safety and staff are healthy and safe, there is great potential economic benefit, social benefit and environmental benefit.
Description
Technical field
The present invention relates to hydraulic structure technical fields, and in particular to a kind of complexity hydraulic structure partial structurtes self-vibration frequency
Rate calculation method.
Background technique
For solving the local monomer structure natural frequency of vibration of complicated hydraulic structure, first method is built to complicated water conservancy project
The integrally-built natural frequency of vibration of object is built to be solved.This method unites the stiffness matrix of all nodes of overall structure and mass matrix
One solve system of equation, obtains the frequency and amplitude of free vibration of overall structure Yu each partial structurtes, method for solving it is fairly simple and by
It is commonly used to solve the self-vibration characteristic and the vibration shape of dam.But for complicated hydraulic structure, this method often can not be asked effectively
Solution.By taking Large Hydroelectric Power Station Plant as an example: each workshop section in general power station is adjacent, the selection of boundary condition to workshop overall structure from
Vibration frequency is affected, and workshop will not cause workshop overall structure to generate judder in unit operation, but part is tied
Structure judder.Therefore, the problems such as single integrally-built frequency and amplitude of free vibration of unit section workshop is for vibrating is solved without reality
Border engineering significance, but should Accurate Analysis partial structurtes the natural frequency of vibration and the vibration shape.But due to large-scale power station mill construction
Complexity, the vibration shape of each partial structurtes (such as column, floor) is difficult to distinguish from the vibration shape because architectural characteristic often intercouples
Not a certain frequency belongs to the natural frequency of vibration of which partial structurtes.Therefore, this method be unsuitable for solving complicated hydraulic structure from
Vibration frequency and the vibration shape.
Second method is the independent modeling of local monomer structure for needing to solve in complicated hydraulic structure and to ask
Solution, therefore this method not only models simplicity, and it is smaller to solve scale.But the disadvantages of this method are as follows: independent part monomer structure
The constraint condition (rigidity of i.e. local monomer structure) of model is difficult the constraint condition one with monomer structure local in overall model
It causes, or even differs greatly.Still by taking the column of Large Hydroelectric Power Station Plant as an example, if applying fixed constraint at column both ends, due to it
Confinement stiffness ratio constraint rigidity suffered by overall structure central post is much greater, therefore it calculates resulting frequency than practical frequency
Rate wants high by 50% or more.If column both ends are constrained using freely-supported, confinement stiffness ratio constraint suffered by overall structure central post
Rigidity wants small many, therefore it calculates resulting frequency lower than actual frequency 30% or more.Independent part monomer structure model
Mode participation mass it is less than normal than the mode participation mass of monomer structure local in overall model.It is independent from mill construction
Column finite element model does not consider that both ends participate in the quality in the building of constraint, therefore the ginseng of its vibration shape when solving its frequency and the vibration shape
It is less than normal with quality.Therefore second method is for solving the natural frequency of vibration of local monomer structure in complicated hydraulic structure often band
Come large error, even error result.
The third method is asked in complicated overall structure with reference to the method for the dam natural frequency of vibration for solving no- paper library
Solve the local monomer structure natural frequency of vibration.Still by taking powerhouse of hydropower station structure as an example, the advantages of this method is effectively to simulate column P1
The practical stiffness at (as shown in Figure 4) both ends, therefore the computational solution precision that this method obtains has compared with method two compared with much progress.But
The disadvantages of this method are as follows: do not consider that both ends participate in the quality in the building of constraint when solving the frequency and the vibration shape of column P1, the vibration shape
It is less than normal to participate in quality, therefore often bigger than normal using the calculated natural frequency of vibration of this method, ratio bigger than normal is even more than 30%.
Summary of the invention
Technical problem to be solved by the invention is to provide a kind of complicated hydraulic structure partial structurtes natural frequencies of vibration to calculate
Method solves the problems, such as the local monomer structure natural frequency of vibration calculated result inaccuracy of complicated hydraulic structure.
The technical scheme to solve the above technical problems is that a kind of complexity hydraulic structure partial structurtes self-vibration frequency
Rate calculation method, comprising the following steps:
S1, the three-dimensional CAD model for creating hydraulic structure；
S2, partial structurtes to be solved are assigned with material properties, and by the elasticity modulus of remaining structure and Poisson's ratio by real
Border parameter assignment, but density value is assigned to 0；
S3, three-dimensional CAD model is divided into several finite element grids by tetrahedron element or hexahedral element；
S4, apply Viscoelastic Boundary Conditions for three-dimensional CAD model；
S5, the first rank natural frequency of vibration f by Finite element arithmetic partial structurtes1；
S6, selection and the finite element grid for having assigned density structure adjacent regions, and press the actual density assignment at the position；
S7, pass through the first rank natural frequency of vibration f of partial structurtes under the conditions of Finite element arithmetic step S62；
S8, as the first rank natural frequency of vibration f1With the first rank natural frequency of vibration f2Relative error be greater than threshold value when, return step
Otherwise S6 enters step S9；
S9, by the first rank natural frequency of vibration f2The natural frequency of vibration as the partial structurtes.
Based on the above technical solution, the present invention can also be improved as follows.
Further, the calculation formula of the first rank natural frequency of vibration f are as follows:
|[K]-ω2[M] |=0 (1)
In above formula, [K] is stiffness matrix, and [M] is mass matrix, and ω is circular frequency.
Further, in the step S4 elastic boundary condition resistance coefficient KbWith damped coefficient CbCalculation formula are as follows:
Cb=ρ cs (4)
In above formula, G is ground modulus of shearing, rbFor wave source to the distance for calculating point, ρ is that ground becomes mould, csFor shearing wave
Speed or compression velocity of wave.
Further, the material properties include density, Poisson's ratio and elasticity modulus.
Further, the threshold value is 5%.
Further, the size of the finite element grid is less than or equal to the 1/3 of partial structurtes sectional dimension to be solved.
The beneficial effects of the present invention are: the present invention can high-precision analog part monomer structure practical stiffness and height
The actual participation quality of its vibration shape of precision analog can greatly improve the complicated hydraulic structure partial structurtes natural frequency of vibration and solve essence
Degree, carrying out complicated hydraulic structure dynamic design using the present invention can avoid generating high vibration and resonance, guarantee waterwork
Object inherently safe, instrument and equipment safety and staff are healthy and safe, have great potential economic benefit, social benefit and ring
Border benefit.
Detailed description of the invention
Fig. 1 is general flow chart of the present invention；
Fig. 2 is hydraulic structure finite element grid schematic diagram in the embodiment of the present invention；
Fig. 3 is hydraulic structure Visco-spring Boundary schematic diagram in the embodiment of the present invention；
Fig. 4 is that frequency domain selects schematic diagram in the embodiment of the present invention.
Specific embodiment
The principle and features of the present invention will be described below with reference to the accompanying drawings, and the given examples are served only to explain the present invention, and
It is non-to be used to limit the scope of the invention.
As shown in Figure 1, a kind of complexity hydraulic structure partial structurtes natural frequency of vibration calculation method, comprising the following steps:
S1, the three-dimensional CAD model for creating hydraulic structure.
S2, partial structurtes to be solved being assigned with material properties, material properties include density, Poisson's ratio and elasticity modulus,
And by the Poisson's ratio of remaining structure and elasticity modulus according to actual parameter assignment, but density value is assigned to 0.
S3, as shown in Fig. 2, three-dimensional CAD model is divided into several finite elements by tetrahedron element or hexahedral element
Grid can use tetrahedron element grid division when static stress or dynamic stress of the calculated result without paying close attention to hydraulic structure, but
The selection of unit range in follow-up work is influenced using tetrahedron element；When calculated result needs to consider that the quiet of hydraulic structure is answered
Power or dynamic stress should be not only convenient in this way the choosing of subsequent cell range using hexahedral element and its tri-prism element of degeneration
It selects, and cell node scale ratio is small using tetrahedron element.
S4, as shown in figure 3, for three-dimensional CAD model apply Viscoelastic Boundary Conditions, hydraulic structure generally build with ground it
On, ground can transmit and loss vibrational energy.It is propagated for that can reduce calculation scale and effectively simulate remote domain vibrational energy
With loss.
S5, the first rank natural frequency of vibration f by Finite element arithmetic partial structurtes1。
The finite element grid of S6, the structure adjacent regions for selecting and having assigned density, and press the actual density assignment at the position.
As shown in figure 4, returning to the A for selecting the both ends column P1 when solving and unit B simultaneously for the first time when solving the self-vibration characteristic of column P1
Its actual density is assigned, second of return chooses unit within the scope of 1-1 and assign its actual density when solving, the 3rd return
Unit within the scope of 2-2 is chosen when solution and assigns its actual density, and so on, it can constantly expand selection range.
S7, pass through the first rank natural frequency of vibration f of partial structurtes under the conditions of Finite element arithmetic step S62。
S8, as the first rank natural frequency of vibration f1With the first rank natural frequency of vibration f2Relative error be greater than threshold value (threshold value 5%)
When, otherwise return step S6 enters step S9.
S9, by the first rank natural frequency of vibration f2The natural frequency of vibration as the partial structurtes.
Further, the calculation formula of the first rank natural frequency of vibration f are as follows:
|[K]-ω2[M] |=0 (1)
In above formula, [K] is stiffness matrix, and [M] is mass matrix, and ω is circular frequency.
Further, in the step S4 elastic boundary condition resistance coefficient KbWith damped coefficient CbCalculation formula are as follows:
Cb=ρ cs (4)
In above formula, G is ground modulus of shearing, rbFor wave source to the distance for calculating point, ρ is that ground becomes mould, csFor shearing wave
Speed or compression velocity of wave.
In embodiments of the present invention, the size of finite element grid is less than or equal to the 1/3 of partial structurtes sectional dimension to be solved
(preferably no more than 1/4), by taking powerhouse of hydropower station structural upright as an example, column size is if 1m × 1m, then column prolongs section side
To unit and with the size of column both ends floor preferably no more than 0.25m.
In another embodiment of the present invention, step S3 and step S4 interchangeable sequence, but will increase as partial structurtes imparting
The difficulty of material properties.
The foregoing is merely presently preferred embodiments of the present invention, is not intended to limit the invention, it is all in spirit of the invention and
Within principle, any modification, equivalent replacement, improvement and so on be should all be included in the protection scope of the present invention.
Claims (6)
1. a kind of complexity hydraulic structure partial structurtes natural frequency of vibration calculation method, which comprises the following steps:
S1, the three-dimensional CAD model for creating hydraulic structure；
S2, partial structurtes to be solved are assigned with material properties, and by the elasticity modulus of remaining structure and Poisson's ratio by practical ginseng
Number assignment, but density value is assigned to 0；
S3, three-dimensional CAD model is divided into several finite element grids by tetrahedron element or hexahedral element；
S4, apply Viscoelastic Boundary Conditions for three-dimensional CAD model；
S5, the first rank natural frequency of vibration f by Finite element arithmetic partial structurtes1；
S6, selection and the finite element grid for having assigned density structure adjacent regions, and press the actual density assignment at the position；
S7, pass through the first rank natural frequency of vibration f of partial structurtes under the conditions of Finite element arithmetic step S62；
S8, as the first rank natural frequency of vibration f1With the first rank natural frequency of vibration f2Relative error when being greater than threshold value, return step S6 is no
Then enter step S9；
S9, by the first rank natural frequency of vibration f2The natural frequency of vibration as the partial structurtes.
2. complexity hydraulic structure partial structurtes natural frequency of vibration calculation method according to claim 1, first rank is certainly
The calculation formula of vibration frequency f are as follows:
|[K]-ω2[M] |=0 (1)
In above formula, [K] is stiffness matrix, and [M] is mass matrix, and ω is circular frequency.
3. complexity hydraulic structure partial structurtes natural frequency of vibration calculation method according to claim 1, which is characterized in that institute
State the resistance coefficient K of elastic boundary condition in step S4bWith damped coefficient CbCalculation formula are as follows:
Cb=ρ cs (4)
In above formula, G is ground modulus of shearing, rbFor wave source to the distance for calculating point, ρ is that ground becomes mould, csFor shear wave velocity or
Compress velocity of wave.
4. complexity hydraulic structure partial structurtes natural frequency of vibration calculation method according to claim 1, which is characterized in that institute
Stating material properties includes density, Poisson's ratio and elasticity modulus.
5. complexity hydraulic structure partial structurtes natural frequency of vibration calculation method according to claim 1, which is characterized in that institute
Stating threshold value is 5%.
6. complexity hydraulic structure partial structurtes natural frequency of vibration calculation method according to claim 1, which is characterized in that institute
The size for stating finite element grid is less than or equal to the 1/3 of partial structurtes sectional dimension to be solved.
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Cited By (3)
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| CN111709073A (en) * | 2020-06-04 | 2020-09-25 | 黄淮学院 | Method and system for measuring natural vibration frequency and vibration mode for building structure dynamic analysis |
| CN112231954A (en) * | 2020-10-15 | 2021-01-15 | 中国水利水电科学研究院 | Method for establishing hydraulic structure digital twin model |
| CN112781717A (en) * | 2020-12-31 | 2021-05-11 | 长江勘测规划设计研究有限责任公司 | Method for measuring natural vibration characteristic of complex building structure |
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| CN112781717A (en) * | 2020-12-31 | 2021-05-11 | 长江勘测规划设计研究有限责任公司 | Method for measuring natural vibration characteristic of complex building structure |
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