دانلود رایگان مقاله تحلیل جریان سیالات مستقیم immersogeometric با مدل B-rep CAD

Abstract

We present a new method for immersogeometric fluid flow analysis that directly uses the CAD boundary representation (B-rep) of a complex object and immerses it into a locally refined, non-boundary-fitted discretization of the fluid domain. The motivating applications include analyzing the flow over complex geometries, such as moving vehicles, where the detailed geometric features usually require time-consuming, labor-intensive geometry cleanup or mesh manipulation for generating the surrounding boundary-fitted fluid mesh. The proposed method avoids the challenges associated with such procedures. A new method to perform point membership classification of the background mesh quadrature points is also proposed. To faithfully capture the geometry in intersected elements, we implement an adaptive quadrature rule based on the recursive splitting of elements. Dirichlet boundary conditions in intersected elements are enforced weakly in the sense of Nitsche's method. To assess the accuracy of the proposed method, we perform computations of the benchmark problem of flow over a sphere represented using B-rep. Quantities of interest such as drag coefficient are in good agreement with reference values reported in the literature. The results show that the density and distribution of the surface quadrature points are crucial for the weak enforcement of Dirichlet boundary conditions and for obtaining accurate flow solutions. Also, with sufficient levels of surface quadrature element refinement, the quadrature error near the trim curves becomes insignificant. Finally, we demonstrate the effectiveness of our immersogeometric method for high-fidelity industrial scale simulations by performing an aerodynamic analysis of an agricultural tractor directly represented using B-rep.

6. Conclusions

In this paper, we presented a new method for immersogeometric fluid flow analysis that directly makes use of the CAD B-rep of a complex object and immerses it into a locally refined, non-boundary-fitted background fluid mesh to avoid the challenges associated with geometry cleanup and mesh generation and manipulation. To assess the accuracy of the proposed method, we performed computations of the benchmark problem of flow over a sphere represented using B-rep. Quantities of interest such as drag coefficient were in good agreement with reference values reported in the literature. The results showed that the density and distribution of the surface quadrature points are crucial for accurate high-fidelity flow analysis. Also, with sufficient levels of surface quadrature element refinement, the quadrature error near the trim curves became insignificant. Finally, we demonstrated the effectiveness of our immersogeometric method for industrial scale simulations by performing an aerodynamic analysis of an agricultural tractor directly represented using B-rep.