ZHU Wen-ruo 1, GAO Zhong-xin 1, LU Li 1, WANG Fu-jun 2 (1. China Institute of Water Resources and Hydropower Research, Beijing 100038, China; 2. College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China)

Abstract: Normally, in real project, the natural frequency of a structure in water can be obtained by Natural frequency of the structure in air times an influence coefficient. However, there are big errors between the result obtained by traditional experience influence coefficients and realistic ones. For more clearly expressing the influence on structure by water, depreciation coefficient rather than influence coefficient was chosen to discuss. Finite element method based on the fluid-structure interaction was used in cylinder and impeller model analysis and a new set of experience depreciation coefficient was put forward. The results showed that depreciation coefficient has great relationship with natural frequency and vibration mode. It is reasonable to use segment value suggesting that the small value was applied in the low order level and rotation vibration mode, and the high value was applied in the high order. At last, secondary optimization was made in the calculation result of impeller model and the depreciation coefficients which are more consistent with realistic ones show that, in 1, 2, 4, 5 and 6 order, the depreciation coefficient is 0.15; in 3 order, the depreciation coefficient is 0.05 and in 7, 8, 9 and 10 order, the depreciation coefficient is 0.40.

Key words: Fluid-structure interaction, Modal analysis, Depreciation coefficient, Centrifugal impeller

Published in: Journal of Hydraulic Engineering, Vol. 44, No. 12, 2013