Study On Coupled Dynamics Analysis And Working State Identification Of Flood Discharge Structures

With the large number of high-head and large discharge flood discharge structures construction and the trend of lightweight of flood discharge structures, the problem of flow-induced vibration will become prominent. It is an important subject for flood discharge structures design and safe operation to study on flow-induced vibration mechanism, simulation and prediction methods of coupled dynamic analysis of flood discharge structure, optimum design and safety dynamic detection methods of flood discharge structures. In the paper, the following three main areas are studed:Firstly, the study on simulation and prediction methods of coupled dynamics analysis of flood discharge structure. The paper has succeeded in achieving coupled dynamic analysis from traditional analysis mode with single hydrodynamic effect considered to coupled analysis mode with hydrodynamic-structure system coupled effect considered. (1) Based on the study on that the similarity law of fluctuating pressure spectrum agrees with the gravity law, taking radial gate as an example, the paper consider the effect of the system coupling of the whole gate and the hydrodynamic characteristic of gate. This whole coupling system vibration of hydraulic system—structure system of gate—prop system (pier, start and stop lever) is simulated using physical model for the first time, and then a 3D space FEM mathematical model using three-dimensional shell element is set up and its dynamic characteristic is analyzed. (2) The dynamic-stability analysis method of the radial gate arm under eccentric loading is produced, and the influences of the dynamic-stability of radial gate arm under eccentric loading are also studied. (3) Finally, associated with physical, numerical model and dynamic stability analysis, the dynamic safety of the gate was analyzed, and several suggestions and proposal that avoid adverse vibration are presented.Secondly, study on coupled dynamic optimization design methods of flood discharge structures. The paper produces the coupled dynamic optimization design methods of flood discharge structures. (1) Considering the coupled dynamic safety index of guide wall, the paper propose the guide wall structure optimization design method and put forward the section optimization mathematic model of guide wall. Based on the consideration of coupled dynamic safety constraint condition, the geometrical condition, static strength, stability constraint are also taken into account, and the static analysis, couple dynamic analysis and Support Vector Machine(SVM) technique are combined to evaluate the quality of guide wall section intelligently. Employing real encode of GA and generating initial population groups of guide wall sections randomly, the guide wall section is optimized on the condition of that the guide wall structure meet the specification of static and dynamic safety. (3) Considering the static restriction and the dynamic stability of the arms of radial gate, the paper propose the optimization design method and optimization mathematic model of main frame of radial gate. The main frame of radial gate is optimized on the basis of considering geometrical constraint condition, static strength, rigidity constraint, static and dynamic stability constraint. The result shows that the weight of the gate is lightened with the guarantee of the static and dynamic stability of the arms and saves the investment of the project.Thirdly, study on dynamic detection and working state characteristic identification of flood discharge structures under flood discharge excitation. Aimed at the difficult problem of exciting the prototype to test, combined with the ambient loading characteristic, the dynamic characteristic of hydraulic structure is directly identified according to the dynamic response of structure under ambient excitation in the paper. (1) We propose a method in the paper to denoise, reconstruct, determine the order and identify modal parameters based on singular entropy of eigenmatrix. It can be used to solve the problem of system eigenmatrix order determination, and to identify the modal order and the characteristics of structures under the working state. (2) The subjective selection and accuracy of singular value curve peak (spectral density function peak) depend on the accuracy of the calculation of power spectral density function in process of Fourier transform. In order to solve this problem, modal coherence function is put forward in the paper to identify the singular value curve peak accurately. This method solve the problem of modal frequency peaking which is likely to be false modal frequency caused by noise (such as flow frequency) or structural modal frequency, and identify the dominate frequency domain of one mode, improve the accuracy of damping ratio calculation. (3) A large-scale comprehensive prototype vibration tests against Ertan arch dam, Spillway dam and Left guide wall of Three Gorges, Powerhouse with a two-row placed unit of Lijiaxia hydropower station are primarily carried out during the working state (e.g. Flood spillway working state in flood season). And the modal parameter identification theory under flood discharge excitation proposed in the paper is primarily applied to the operational modal parameter identification of these large-scale prototype hydraulic structures, and the normal operational behaviors of these hydraulic structures are evaluated.