ICONE15-10488 DEVELOPMENT OF MULTISCALE LES CODE MISTRAL AND ITS APPLICATION TO A T-JUNCTION PIPE FLOW

Abstract

The necessity of multiscale numerical model is explained first to mimic the energy cascade of turbulence in the introduction of this paper. Then, the outline of a multiscale large-eddy simulation code MISTRAL is explained, including the basic equations, turbulence models, numerical formulation and numerical techniques employed. In MISTRAL, both velocity and pressure are split into the large-scale and small-scale resolvable components, and unresolvable components. Each resolvable component is approximated with large-scale and small-scale finite elements. Variational method is used not only to yield the spatially discretized equation system but also to close the turbulence terms resulted from unresolvable components. With such a formulation, multiscale turbulent viscosities can be given and the adequate magnitudes of them may be estimated by the balance of turbulent kinetic energy and model dissipation. The multiscale mass matrix lumping technique is used for an efficient time integration in MISTRAL. As an example of the application, an isothermal flow in a T-junction pipe is analyzed with MISTRAL code. For comparison, numerical results obtained by a conventional LES code are also presented. The 1st and 2nd moments of turbulent velocities as well as the power spectra are computed with these numerical results, to discuss the superiority of MISTRAL in predicting statistical quantities.