Papers by Author: Wen Juan Lou

Abstract: Aerodynamic characteristics of iced conductors were investigated by the wind tunnel test. Under the homogeneous turbulence of 5% intensity, aerodynamic force coefficients of single and bundled conductors were obtained at wind angles of 0°~180°. The variation patterns of aerodynamic forces on the iced conductors with respect to wind angels of attack were systematically studied for the ice thickness of 0.25, 0.5, 0.75 and 1 times of the conductor diameter. The difference of aerodynamic force characteristics for single and bundled conductors were identified and discussed. Based on the Den Hartog and Nigol’s mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed. The results show that lift and torsion force coefficients reach peak values at wind angles of 15°~20°. For bundled conductors, lift force curve is approximately agreed with the curve of single conductor. Drag force coefficients were smaller than these of single conductor at some wind angles. There are noticeably differences of torsion coefficients existed between bundled conductors and single conductor. According to two classical galloping mechanisms, wind angles of 15°~30°are critical for the galloping of iced conductors with crescent shapes.

Abstract: By the combination of POD method and mode superposition method, the eigenvector similarity factor is introduced on the representation of the similarity between the load spacial distribution and the structural mode. Meanwhile, the eigenvalue got from the wind pressure field decomposition indicates the relative ratio of the energy associated with the corresponding load spacial distribution to the total of the wind load energy. It is proved that the eigenvector similarity factor and the eigenvalues are two of most important factors when measuring the relative significance of each modal response. So the quick estimates of the modal responses are provided, which predominates in picking structural modes to obtain wind-induced dynamic response of long-span roof structure with frequency-domain method. Then, by arranging the estimative response of each mode in reduced-order and truncating higher modes to expedite computations, the accurate wind-induced response is calculated by ACQC method, which has taken into account the partial correlation of wind loads and the quad-spectra (imaginary parts of XPSD) of the generalized wind loads. Finally, utilizing the rigid model wind tunnel test data of some large railway station platform, the effectiveness of the scheme proposed is verified.

Abstract: In order to solve the problem of fluid-structure interaction, this paper presents a new numerical method named as particle on grid method (POGM) for incompressible fluid. Based on the physical mechanism of the fluid motion, the POGM has a clearly physical meaning by using representative physical values at points to describe the fluid’s overall flow. It has been proved that this method is consistent with Navier-Stockes’ equation essentially, and some numerical problems have been discussed. Coutte flow and Poiseuille flow are used in the numerical examples. The results of the POGM are well agreed with the analytical solutions of incompressible flows of the examples.

Abstract: The basic concepts and theories of Hilbert-Huang-Transformation (HHT) for signal analysis is introduced and its implementation procedure is programmed. For the collected three orthogonal directions wind speed signals at a measuring point at Sutong Bridge site, Empirical Mode Decomposition (EMD) is conducted to extract the Intrinsic Mode Functions (IMFs). Hilbert transformation is performed on IMFs and its marginal amplitude spectra and amplitude spectra are achieved. The orthogonal exponential matrix that reflects the orthogonalities between the IMFs is obtained, and eigenvalue decomposition is carried out. The results show that the measured wind speed appears non-stationary nature, even for the same measuring point, for the wind speed at different directions, the dominant frequencies are distinct.