Numerical Simulation Of Two-dimensional Flow Past A Tall Building Using A Discrete Vortex Method

The paper firstly introduces the development of building flow field technology and the general situation of numerical simulation of unsteady separated flow. Then a detailed discussion on the discrete vortex method used to analyze the two-dimensional flow past a rectangular prism is given. The flow is assumed to be a potential flow except in the region of the free shear layers which are shed downstream from the separation points, the region and the building are represented by discrete vortices.The characteristics of wind field are numerically simulated by Fortran program, the lift and drag coefficients and Strouhal numbers are analyzed for several angles of attack. By numerical simulation, we can evaluate the Strouhal numbers,lift and drag coefficients exactly. The development of vortex obtained from simulation takes a remarkable resemblance to the patters shown in common experiments. The curve distribution and fluctuation of and being reasonable, and the average value at each angle is close to the published results.The flow field around an oscillating square prism under heaving motion is calculated by using the method proposed in this paper. Results in the form of fluctuating lift coefficients, power spectral density of lift coefficients are presented for a square cylinder undergoing transverse oscillations over a range of frequencies and amplitudes. The results demonstrate that the method successfully predicts the vortex lock-in phenomena around the resonance point, as well as capturing the various states of the flow field expected above and below vortex lock-in.As the analysis and calculation results show, the discrete vortex method can analyze and simulate the unsteady separated flow centering on a construction structure with a certain shape in a fairly simple and effective way. It can be used not only to describe the general features of flow field but also to depict the flow mechanism. On the other hand, the necessary precision is likely not to be guaranteed as far as the calculation of the force acting on objects is concerned. The method discussed in the paper is expected to provide a powerful tool in analyzing the features of building flow field and obtaining aerodynamic forces acting on structures.