Study On Novel Fluid Finite Element Method And Its Applications In Wind Flow Around Structure And Wind-Structure Interaction Effect

With the great progresses in computer technique and numerical methods, the turbulent wind simulations and the FSI (Fluid-Structure Interactions) between wind and structures, based on CFD (Computational Fluid Dynamic), have already been hot issues in structural engineering.First, a novel stabilized fluid finite element method is proposed for the predictions of incompressible viscous fluid problems. With the combination of semi-implicit three step method and streamline upwind Petrov-Galerkin (SUPG) method, the SUPG stabilized scheme is used for the spatial discretization, the same order interpolations are performed for both velocity and pressure fields. Thus, the computational stabilization on both velocity and pressure, and the computational efficiency are effectively improved. The numerical predictions on lid driven flows in square, triangular and skewed cavities are close to reference results which testify the accuracy and efficiency of present method.Secondly, based on present novel stabilized fluid finite element method, a novel large eddy simulation of stabilized fluid finite element is developed. With the combination of classical Smagorinsky sub-grid scale model and the SUPG stabilized method, the present method can be successfully applied for numerical simulation of both transient and unsteady turbulent flows with high Reynolds number. The same order interpolation is employed for spatial discretization of both velocity and pressure. The temporal discretization is applied by three-step technique which is second order accurate and high stabilized. Numerical examples show that present method can effectively suppress the computational oscillation of velocities and pressure fields, as well as yield compared accurate velocity and pressure fields as well as aerodynamic parameters. Thirdly, for the second filtering progress of dynamic sub-grid scale model, a simple and fast spatial filtering method on unstructured finite element grids is developed by the combination of both node-based filter and generalized box filter. Then, based on present novel stabilized fluid finite element method and dynamic sub-grid scale model, dynamic large eddy simulation is developed to predict turbulent flow characteristics around structures. Numerical simulation shows that present numerical method can model the turbulent flow problems with complex structural geometry and describe typical vortex structures of wind around structures.Fourthly, for the grids update of the fluid domain, spring analogy method is improved by introducing scale and shape parameters to the definition of the spring stiffness. The improved spring analogy method has the strongpoints of both lineal spring method and torsional spring method, and adapts both two and three dimensional boundary movement problems. On the other hand, based on present large eddy simulation technique of stabilized fluid finite element method, the finite element formulation of wind field described by arbitrary Lagrangian-Eulerian (ALE) formulation is deduced to numerically simulate turbulent wind field under the circumstance of large amplitude structural forced vibration.Finally, by applying the FSI theory, a numerical method is constituted for wind induced vibration analysis of long span spatial structures. Partitioned procedure is adopted, including fluid domain, structure domain and grid domain. Present large eddy simulation technique of finite element method is applied for the prediction of fluid domain. Newmark integral method based on finite element formulation is applied for the computation of structure domain. And improved spring analogy method is applied for the gird update of grid domain. The wind induced vibration of spherical single layer lattice shell structure is predicted, and the bluff flow characteristics and typical vortex structures around structures are indicated. Further more, the mean wind pressure, fluctuating wind pressure and dynamical responses of structures based on the rigid structural model and structural model considering FSI are analysed, respectively.