(162e) Predicting Turbulent Flows Using the Immersed Surface Technology Combined with Block Mesh Refinement (IST/BMR)

This talk will center on using a fast and versatile grid generation technique for the LES of industrial fluid mechanics problems. The approach known as The Immersed Surfaces Technique (IST) dispenses from the use of conventional structured grids and finite-element unstructured type of grids, in that solid bodies are immersed within a Cartesian grid from a CAD file. The idea (which differs from the Immersed Boundaries of Peskin) is to represent solid walls by a Level Set function representing the exact distance to the surface, which is zero at the surface, positive in the fluid(s) and negative in the solid. The fluid(s) and the solid have their own material properties, based on the Level Set function. The technique has the major advantage to solve conjugate heat transfer problems and fluid-structure interactions. In practice, the CAD file of the solid is first immersed into a cubical grid covered by a Cartesian mesh. The Navier-stokes equations are modified to account for the presence of the solid level set function. The treatment of viscous shear at the solid surfaces is handled using information buried in the solid level-set function. The BMR technique (Block Mesh Refinement) was developed to help better solve the boundary layer zone when use is made of the IST technique discussed above. In BMR, more refined sub-blocks are automatically generated around solid surfaces; with dimensions made dependent on the Reynolds number (the sub-block scale should always be set such that it covers the boundary layer thickness). An unlimited number of sub-blocks of different refinement can be generated, with connectivity between the blocks matching up to 1-to-8 cells. The method has been validated for canonical laminar and turbulent flows, and is now under evaluation for its extension to LES. Various examples will be presented; limitations and issues will be discussed as well.