Numerical Simulation Of 2-D Rectangular Column Under Steady And Unsteady Winds

Previous studies of flow simulation in wind engineering treats the wind as a steady flow. However, air movement near the earth surface is actually the kind of wind whose magnitude and direction change randomly. Using the CFD software Fluent 6.2, a large number of numerical simulations for the flowing around the static and moving rectangular column are conducted, and its responses in stationary and non-stationary wind are obtained. The main work in this paper is outlined as follows.Firstly, within the subcritical range of Reynolds number, the structural drag coefficient is obtained by computation of steady flow field, in which the laminar flow model is used. The structural drag coefficient, lift coefficient and Sthouhal number are obtained by computation of unsteady flow field, in which the k ?ωSST model is used. These results are compared with experimental and numerical data to validate the model in this paper.Secondly, using the dynamic mesh and sliding mesh techniques in Fluent6.2, the response of rectangular column in steady wind is obtained by embedding the Newmark-βcode through the User Defined Function(UDF) in Fluent. The responses of the stationary column, free-to-both-stream-and-transverse column and only free-to-transverse column are compared. The differences of force acted on rectangular column and its response are observed under these three conditions.Thirdly, when the inflow wind is unsteady, the stream-wise response and the transverse response are computed in different cases. The unsteady flow is simulated by assuming the mean wind changing as sinusoidal function. By changing the frequency and amplitude of the sinusoidal gust sequence, the force and response of the rectangular column are obtained. The step shaped inflow is also simulated, and the results are compared with the wind tunnel results.Numerical study of rectangular column under steady and unsteady winds in this paper lays the foundation for further studies on simulation of more complicated unsteady winds effect on bluff bodies.