矩形断面非线性驰振自激力测量及间接验证中若干重要问题的讨论

采用专门研制的小型动态测力天平，通过弹簧悬挂节段模型内置天平同步测力测振风洞试验，对3:2矩形断面的非线性驰振自激力进行了测量。比较了基于实测自激力重构的节段模型位移响应时程与试验结果，从而对自激力测量精度进行了间接的验证；讨论了在进行这种验证时考虑节段模型系统等效阻尼和刚度参数非线性特性的重要性、非风致附加自激力和风致自激力在动态力中的占比、忽略非风致附加气动阻尼力和惯性力的非线性特性对自激力测量精度的影响等若干重要问题。结果显示:对于3:2矩形断面，非风致附加自激力在测得的总动态力中的占比超过了风致自激力的占比，因此从测得的总动态力中提取自激力时必须扣除非风致附加自激力；非风致附加气动阻尼力和惯性力的非线性对驰振自激力测量精度有一定影响，值得考虑；节段模型系统等效阻尼和刚度参数的非线性对节段模型驰振位移响应的重构精度有明显影响，在验证自激力测量精度时必须加以考虑。

Discussionon several important issues in measurement and indirect verification of nonlinear galloping self-excited forceson rectangular cylinders

The nonlinear galloping self-excited forces on a 3:2 rectangular cylinder were measured via wind tunnel tests of a spring-suspended sectional model with synchronous measurements on dynamic force and vibration displacement by using miniature dynamic force balances elaborately developed. The measurement accuracy of the self-excited force was verified indirectly through comparing the time histories of the nonlinear galloping displacement of the sectional model reconstructed by using the measured time histories of the self-excited force with the corresponding measured ones. The importance of considering the nonlinearities of the effective damping and stiffness parameters of the sectional model system in such verification was discussed. The percentages of both the non-wind-induced and wind-induced self-excited forces in the total measured dynamic forces were also evaluated as well as the influences of neglecting the nonlinearities of the non-wind-induced additional aerodynamic damping and inertial forces on the measurement accuracy of galloping self-excited force. It can then be found that for the 3:2 rectangular cylinder the portion of the non-wind-induced self-excited force in the measured total dynamic force exceeds that of the wind-induced self-excited force, and therefore, the non-wind-induced self-excited force should be deducted when extracting the wind-induced self-excited force from the measured total dynamic force. The nonlinearities of the non-wind-induced damping and inertial forces exert some influence on the measurement accuracy of the galloping self-excited force, and deserve to be considered. The nonlinearities of the equivalent damping and stiffness parameters of the sectional model system result in a significant influence on the reconstruction accuracy of the galloping displacement time histories of the sectional model system, and thus, it should also be taken into account in the indirect verification of the measurement accuracy of the galloping self-excited force.