Eddy Collision Models for Turbulence

Abstract

This chapter demonstrates that collisional models are a viable alternative to Reynolds stress transport (RST) models. Simple fluids, such as gases and liquids are the result of collisions between molecules. More complex fluids, such as granular flows and colloidal suspensions (non-Newtonian fluids), result from the more complex collision (or interaction) behaviors of their constituent particles. This chapter examines that collision rules can be constructed for large chunks of fluid material (eddies) such that the resulting collective system behaves like the mean (RANS) flow of a turbulent fluid. The collision model approach has a number of advantages over classic RST models. Turbulent transport does not require a model and mathematical constraints like realizability are automatically satisfied. Using some ideas from lattice-Boltzmann methods and adaptive moving mesh algorithms for computational fluid dynamics (CFD), it is also highlighted that this modeling approach can be made computationally efficient and comparable in cost to classic RST models.