Numerical Simulation and Modeling of Complex Turbulent Flows

Professor Kyle D. SquiresMechanical and Aerospace Engineering DepartmentArizona State UniversityTempe, AZ 85287 USAAbstract:Numerical simulation and modeling of the turbulent flows encountered in aerodynamics applications are challenging for several reasons, including the fact that the Reynolds numbers are usually large and the flows often exhibit significant effects of separation. These and other features challenge simulation strategies and have constrained the application of Computational Fluid Dynamics as a tool for analysis and design.
Simulation strategies have typically relied on Reynolds-averaged Navier-Stokes (RANS) approaches that are computationally feasible and often sufficient in attached flows though are unable to accurately account for the complex effects characteristic of flow separation.
Large Eddy Simulation (LES) is a technique that offers greater fidelity and is a powerful approach away from solid surfaces. Near the wall, however, the computational cost of LES is prohibitive, a fact that will constrain its widespread at high Reynolds numbers for the foreseeable future. These and other considerations have motivated development of
hybrid methods, the most popular of these approaches being Detached-Eddy Simulation (DES). DES combines the most favorable elements of RANS and LES models in a single simulation. In this seminar, development and applications of the method aimed at advancing DES will be reviewed. In natural applications of the technique, attached boundary layers are treated by RANS, exploiting the computational efficiency and relative accuracy of RANS models in attached shear layers. The method becomes an
LES in regions away from the wall provided the grid density is sufficient. The range of DES applications to date include an array of ``building block'' test cases such as the flow over a cylinder, sphere, aircraft forebody, and missile base. In addition, the technique has
been applied to complex geometries, including the flows around fighter aircraft. The developing experience base is encouraging expansion of the method beyond the originally intended class of massively separated flows and a brief description of some of the challenges and recent advances will be presented. These include improvements to the method that modify the DES length scale to overcome errors that can arise from the interface between the RANS and LES regions and development of strategies for seeding turbulent fluctuations in boundary layers.

Location: Stauffer Science Lecture Hall, Rm 102

Audiences: Everyone Is Invited

Contact: April Mundy