Joint Euler-Lagrange Method for Moving Surfaces in Large-Eddy Simulation

Abstract

Continuous growth of computing power strongly encourages engineers to rely more on computational fluid dynamics for the design and testing of new technological solutions. The fast development of these new tools goes along with the increasing availability of high-performance computers, which are necessary to simulate realistic industrial applications. The presented immersed boundary (IB) method is applicable to simple and complex geometries with static and moving boundaries, where fluids interact with the solid structures. The formulation of the method is based on the Eulerian and Lagrangian principles and its key characteristics are its simple formulation and computational efficiency. Furthermore the nature of the method allows the simulations of flows in complex geometries without having to generate complex meshes. The spatial discretization is based on a fixed Cartesian mesh for the Eulerian variables and boundary movements are tracked with Lagrangian particles. Large- Eddy simulations of flows in simple and complex geometries demonstrate the performance of the applied immersed boundary method. Simple cases include the simulation of an isothermal pipe flow and the flow around a sphere. In the first instance, the fluid flows around a static sphere. In the second case the sphere moves relative to the grid for identical flow conditions. Simulations of complex geometries include the investigation of an isothermal and reactive opposed jet flow with perforated and fractal grids. The simulations require cell sizes near the resolution of direct numerical simulations. The injection phase of a piston-cylinder arrangement, assuming constant pressure, is also investigated with the proposed IB method. Good statistical results for first and second moments are achieved for all investigated cases, although the applied grids have to be fine enough to accurately resolve the wall shear stresses. In addition, the concept of using Lagrangian particles has been applied to immiscible flows. Particles are used to improve the accuracy of scalar transport and initial results of simple, two-dimensional test cases are presented.