大攻角下典型主梁断面颤振临界风速数值模拟

Numerical Simulation of Critical Flutter Wind Speed of Typical Bridge Deck Sections at High Attack Angles

针对大攻角下主梁断面颤振稳定性问题,基于计算流体动力学软件ANSYS FLUENT用户自定义函数UDFs和动网格技术,结合Newmark-β法建立了桥梁主梁断面二维流固耦合分析方法,采用该方法在不同攻角下(0°、±3°、±5°、±8°)对薄平板和流线型箱梁断面颤振稳定性进行数值模拟研究,并将数值模拟结果与风洞试验研究结果进行了比较.结果表明:薄平板和流线型箱梁断面的颤振临界风速数值模拟结果与风洞试验结果吻合较好,验证了本文所建立的桥梁主梁断面二维流固耦合分析方法的精度.薄平板断面的颤振临界风速随攻角的增大显著降低;流线型箱梁断面在正攻角范围内颤振临界风速随着攻角的增大而降低,在负攻角范围内颤振临界风速随攻角绝对值的增加先增大后降低;当攻角较大时,薄平板断面和流线型主梁断面均表现出“钝体”特征,气流绕过断面前缘时发生分离,沿断面上下缘产生较大的涡,从而导致主梁断面颤振临界风速降低.

Aiming at the flutter stability of the main girder section at high attack angles,this paper studies the flutter stability of a thin plate and a streamlined box girder section at different attack angles(0°,±3°,±5°,±8°)by numerical simulation method.Two-dimensional fluid-structure interaction(FSI)method combined with Newmark-βmethod is developed based on ANSYS FLUENT user-defined function(UDFs)and dynamic mesh technology.Meanwhile,the numerical simulation results are compared with the wind tunnel test data.The results show that the critical flutter wind speeds of the thin plate section and the streamlined box girder section obtained from numerical simulation method are in good agreement with those from wind tunnel tests,which verifies the accuracy of the two-dimensional FSI analysis method for bridge deck section.The flutter critical wind speed of the thin plate section decreases significantly with the increase of attack angle.The flutter critical wind speed of the streamlined box girder section decreases with the increase of attack angle in the range of positive attack angles,and increases firstly and then decreases with the increasing of absolute values of attack angles in the range of negative attack angles.When the attack angle is large enough,the thin plate section and the streamlined deck section all characterize bluff body,and therefore the incoming flow passes around the leading edge of the section separates and generates large vortices along the upper and lower edges of the section,which leads to a decrease of the critical flutter wind speeds of the bridge girder section.